Energetics and flight performance:

references, abstracts and comments. Where there is no abstract, an abstract has been written, where abstracts are too long they have been abridged. Abstracts in languages other than English have been translated into English. The comment is personal, it points out errors and possible follow-ups, it is begun: CP:
The whole energetics "genre" has a tendency to reproduce a few basic papers and the original Odum paradigm again and again, still there is some slow progress; what was regarded as true and correct in 1963 is not entirely to the point in 2003. Quotation of old papers leads to contradictions in new ones; I cannot see through all these ambiguities, but I will do my best.

L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, Å

Langslow, D. R. (1976): Weights of Blackcaps on migration. Ring. & Migr. 1: 78 - 91.

Lank, D. B. & R. C. Ydenberg, R. C. (2003): Death and danger at migratory stopovers: problems with 'predation risk'. J. Avian Biol. 34: 225-/228.

(Conclusion) The term "predation risk" has been used in literature to refer variously and even interchangeably to any of several meanings, and this can lead to conceptual confusion. In answer to the question posed by Dierschke's (2003) title, light and heavy birds are both "under risk", and all else being equal, heavy birds would face a higher probability of capture. However, in this system, different levels of escape performance correlate with body condition, such that heavier birds can allocate more towards anti-predatory behaviour, and thus reduce their immediate probability of mortality from predation. Distinguishing between danger from the environment, escape performance of an individual, and anti-predatory behaviour as interacting determinants of mortality rate will help identify interesting questions and enable a clearer discussion of the significance of ecological processes.

Lawson, J. W., Magalhães, A. M. & E. H. Miller (1998): Important prey species of marine vertebrate predators in the northwest Atlantic: proximate composition and energy density. MEPS 164: 13 - 20.

Prey energy density values are crucial inputs to bioenergetic consumption models. Vertebrate predators in the northwest Atlantic consume a variety of prey species, but the proximate composition (PC; proportions of lipid, protein, ash and water) and energy density (ED; kJ g-1) of prey, and their variability, are known poorly. In this study, key prey species from Newfoundland and Labrador were studied: Atlantic cod Gadus morhua, American plaice Hippoglossoides platessoides, sand lance Ammodytes dubius, Arctic cod Boreogadus saida, northern shrimp Pandalusborealis, redfish Sebastes spp., Greenland halibut Reinhardtius hippoglossoides, squid Illexillecebrosus and Gonatus fabricii, capelin Mallotus villosus, Atlantic herring Clupea harengus and daubed shanny Lumpenus maculatus. PC and ED varied greatly among species and were influenced by size, season, geography and year. Herring, capelin and G. fabricii had the highest ED, whereas Atlantic cod, plaice, sand lance and shrimp had the lowest. Halibut and I. illecebrosus increased in ED with size. EDs of capelin and redfish varied seasonally; that of plaice and sand lance did not. Herring and halibut had higher ED in the early 1990s than in recent years. Such variation in prey ED has important implications for digestive efficiency, foraging energetics, and dietary preferences of vertebrate predators.

Lind, J. (2001): Escape flight in moulting tree sparrows (Passer montanus). Funct. Ecol. 15: 29-/35.

Lind, J. & S. Jakobsson (2001): Body building and concurrent mass loss: flight adaptations in tree sparrows. Proc. R. Soc. Lond. B 268: 1915-/1919.

Environmental changes are responsible for the evolution of flexible physiology, and the extent of phenotypic plasticity in the regulation of birds' organ size has not been appreciated until recently. Rapid reversible physiological changes during different life-history stages are virtually only known from long-distance migrants, and few studies have focused on less extreme aspects of organ flexibility. During moult, birds suffer from increased wing loading due to wing-area reductions, which may impair flight ability. A previous study found that tree sparrows' escape flight is unaffected during moult, suggesting compensatory aptness. We used non-invasive techniques to study physiological adaptations to increased wing loading in tree sparrows. As wing area was reduced during natural moult the ratio of pectoral-muscle size to body mass increased. When moult was completed this ratio decreased. We show experimentally a novel, strategic, organ-flexibility pattern. Unlike the general pattern, where body mass is positively coupled to pectoral-muscle size, tree sparrows responded within 7 days to reductions in wing area by reducing body mass concurrently with an increase in pectoral-muscle size. This rapid flexibility in a non-migratory species probably reflects the paramount importance and long history of flight in birds.

CP: The authors have measured the surface area of the "pectoral muscle" using alginate gel, while down and contour feathers are growing. This creates an increased demand for supportive tissue in the whole pectoral area, and the authors are not convincing when discussing the possibility that they just measured a "swollenness" of skin with lots of growing down in pin.

Lindström, Å., S. Bensch & D. Hasselqvist (1985): Höstflyttningsstrategi hos unga blåhakar Luscinia svecica. Vår Fågelvärld 44: 197-206.

Autumn migration strategy of young Bluethroats, Luscinia svecica. [The study was performed at two sites: Ammarnäs (65.58 N/16.05 E) and Kvismaren (59.10 N/15.25 E).](...)The results from Ammarnäs show that the young Bluethroats leave their birthplace already from the middle of August, and that they leave without any store of fat, or with just a small amount.
(...)The weight and fat figures from Kvismaren show that Bluethroats arrive with no or little amounts of fat, and that they stay for some time and leave with considerable amounts of fat. The fattest bird had about 25 % of its body weight in fat, and several others had similar amounts of fat. A bird with a 25 % fat content can reach 800 - 1000 km, i.e. over the Baltic Sea and quite some distance into the Soviet Union, where the next resting places are presumably situated.(...)

Lindström, Å. (1986): Fat deposition in migrating birds. Introductory paper no 44, Dept of Ecology, Lund University.

Lindström, Å. & T. Alerstam (1992): Optimal fat loads in birds: a test of the time minimisation hypothesis. Am. Nat. 140: 477-491.

Lindström, Å., Visser, G. H. & S. Daan, S. (1993): The energetic cost of feather synthesis is proportional to basal metabolic rate. Physiol. Zool. 66: 490-510.

Lindström, Å. & T. Piersma (1993): Mass change in migrating birds: the evidence for fat and protein storage re-examined. Ibis 135: 70-78.

Lindström, Å. (1997): Basal metabolic rates of migrating waders in the Eurasian Arctic. J. Avian Biology 28: 87 - 92.

Loske, K.-H. (1990): Spring weights and fat deposition of Palaearctic passerine migrants in Senegal. Ring. & Migr. 11: 23 - 30.

This paper compares the patterns of weight and fat-class of Palaearctic passerine migrants trapped at two sites in Senegal in spring 1986. Despite considerable variations in some species (Reed Warbler Acrocephalus scirpaceus and Subalpine Warbler Sylvia cantillans) the great majority of the birds trapped had weights well above the breeding and wintering levels and showed clear evidence of premigratory fattening. In the Yellow Wagtail Motacilla flava and Chiffchaff Phylloscopus collybita some individuals weighed more than twice as much as others. Mean values of fat-classes of first captures and retraps differed significantly. Species could be divided into two different groups: (a) those (Sand Martin Riparia riparia, Yellow Wagtail and Pied Wagtail M. alba) with small variation in fat classes (12 % - 23 %), and those (Chiffchaff, Subalpine Warbler, Reed Warbler and Redstart Phoenicurus phoenicurus) showing a high variation in fat-class (39 % - 55 %). Birds of the first group had a significantly higher mean fat-class than those of the second group.

Lundgren, B., A. Hedenström & J. Pettersson (1995): Correlation between some body components and visible fat index in the Willow Warbler Phylloscopus trochilus (L.). Orn. Svec. 3: 75-80.

The correlations between some body components and visual as well as chemically extracted fat deposits of migratory Willow Warblers were studied. This study shows that the use of body mass and visual fat index are good predictors of fat deposition in the Willow Warbler. The results also indicate that body water and fat content explain most of the variation of total body mass, followed by carcass-dry mass and pectoralis muscle dry-mass (spring birds). A significant, positive correlation between pectoralis muscle dry-mass and total extracted fat content in spring birds suggests a possible muscle hypertrophy associated with fat deposition. This may be an adaptation to carry heavy fat loads during migratory flights.


Massias, A. & P. H. Becker (1990): Nutritive value of food and growth in Common Tern Sterna hirundo chicks. Orn. Scand. 21: 187 - 194.

McCauley, V. J. E & K. Tsumura (1974): Calorific values of Chironomidae (Diptera). Can. J. of Zool. 52: 581 - 586.

McNamara, J. M. & A. I. Houston (1990): The value of fat reserves and the trade-off between starvation and predation. Acta Biotheor. 38: 37 - 61.

McNeil, R. & F. Cadieux (1972): Fat content and flight range capabilities of some adult spring and fall migrant North American shorebirds in relation to migration routes on the Atlantic coast. Naturaliste Canadien. 99: 589 - 606.

Meissner, W. (1998): Fat reserves in Dunlins Calidris alpina during autumn migration through Gulf of Gdansk. Orn. Svec. 8: 91 - 102.

To describe fat reserves in adult and juvenile Dunlins during autumn migration in the Gulf of Gdansk, multiple regression equations for estimating fat mass in Dunlins were derived. The average fat level in a particular wave of migrants depends on many factors. Low amount of accumulated fat suggests that this species migrates along the southern Baltic in small steps, similarly to the rest of Europe. The interpretation of the results is difficult because at least two distinct migration routes cross the Gulf of Gdansk region. Dunlins starting their primary moult had lower fat index than birds in advanced stages of moult. The rate of fattening in Dunlin depends on the quality of the feeding place (higher in the sewage farm than in the river estuary). Birds which stayed longer in the feeding area had, on average, lower fat mass increments than those leaving Gulf of Gdansk after a short stay. Birds with low fat mass started putting on weight immediately, whereas "fat" birds lost weight at the beginning. Those results confirmed Mascher's (1966) hypothesis about differences in body mass change rate during the first day of stay in birds with low and high fat reserves. The level of free fatty acids in the blood appears to be a factor controlling this pattern. Differences in fat accumulation between Ottenby (southern Sweden) and Gulf of Gdansk are discussed.

Meissner, W. (2001): Biometrics of Turnstone Arenaria interpres migrating in autumn through the Gulf of Gdansk region. Orn. Svec. 11: 181 - 188.

In this study we analyse biometrical data of 69 adult and 389 juvenile Turnstones Arenaria interpres caught during autumn migration when passing through the Gulf of Gdansk in the period 1983-1999. Adults had significantly longer wings than juveniles. Mean values of other measurements did not differ significantly between the age classes. Adults migrating early were larger than those passing the study area later. These earlier and larger migrants are regarded as females, which leave nesting areas before somewhat smaller males. Data obtained from 67 juvenile Turnstones caught at least twice in the same season showed that juvenile Turnstones may have more than one migration strategy when departing from the Gulf of Gdansk. Some of them behave as energy minimizing migrants and migrate with low fat reserves in small steps. The others stay longer, build up large energy reserves (up to 50 % of their initial body mass) and are probably able to reach West Africa in one flight.

Mlody, B. & P. H. Becker (1991): Körpermasse-Entwicklung und Mortalität von Küken der Flußseschwalbe (Sterna hirundo) unter ungünstigen Umweltbedingungen. Vogelwarte 36: 110 - 131. (The development of body mass and mortality of chicks of the Common Tern under unfavourable environmental conditions).

The development of body mass and mortality of Common Tern chicks was studied on the Wadden Sea island of Minsener Oldeoog, Germany, in 1983 and 1984. The breeding success in 1984 was on average 0.08 fledged birds per clutch (1983: 1.5), which is the worst result in six years of investigation at this site (1981-1986). In 1984 only 3 % (1983: 67 %) of the hatched chicks fledged finally. 7 % (7 %) were caught by predators and the remaining 90 % (26 %) were found dead at the nest. Chicks alive as well as dead chicks showed a high deficit of body mass in 1984 compared to 1983. Their body mass development was severely retarded in 1984; body mass increased insufficiently on many days or even decreased. Most of the mortality occurred in an eight-day-period (23 to 30 June 1984), that started with stormy weather and began about a week after the peak of hatching. During its course, 88 % of the chicks died. The age of the dead chicks had the comparatively high median value of 8 days, whereas usually chicks are most likely to die in their first few days of life. The largest decrease in body mass occurred during the period after the storm and affected all age classes of chicks. Most of the dead chicks were lean and had an empty stomach. Some other indirect clues point to a food shortage at that time. The temporal coincidence of high chick mortality with the stormy period was striking, the causes for the mortality are nevertheless hard to name. The proximate factor of death was probably starvation, in some cases perhaps hypothermia. A reduction in the foraging rate of the adult birds due to altered behaviour of the prey species is assumed to be the ultimate factor, perhaps assisted by other factors as the choppy sea surface after the storm.

Monaghan, P., Uttley, J. D. & M. D. Burns (1992): Effect of changes in food availability on reproductive effort in Arctic Terns Sterna paradisaea. Ardea 80: 71 - 81.

The breeding effort of Arctic Terns in two conditions of low food availability in Shetland (A: poor food supply during courtship and very poor during chick rearing, B: very poor during courtship and poor during chick rearing) was compared with that of Arctic Terns breeding in two areas of good food supply elsewhere. In Shetland situation B courthship prey were small and males provisioned females at a comparatively high rate. Neither the onset of laying nor egg size appeared to be affected; clutch size was slightly reduced in Shetland B, and a significantly higher proportion deserted during incubation. Sandeels Ammodytes marinus were the main chick prey and feeding rates were highest when prey were small. No young fledged in the Shetland situations. Adults at the good food supply sites were heavier than those in Shetland and there was a significant positive relationship between adult weight at the time of hatching and the time to nest failure. These data are discussed in relation to the proximate role of food supply in influencing reproductive decisions and a model is proposed suggesting that individual Arctic Terns have a critical threshold body weight below which they abandon breeding.

Moreau, R. E. (1969): Comparative weights of some Trans-Saharan migrants at intermediate points. Ibis 111: 621 - 624.

Moreau, R. E. (1972): The Palaearctic-African Bird Migration Systems. Academic Press, London & New York.

Møller, A. P. (1991): Influence of wing and tail morphology on the duration of song flight in skylarks. Behav. Ecol. Sociobiol. 28: 309-/314.


Newton, I. (1968): The temperatures, weights, and body composition of molting bullfinches. Condor 70: 323 - 332. Internetversion av denna uppsats.

The mean rectal temperature of adult Bullfinches remained fairly stable from before the start of molt until near its end, when it dropped by about 1° C. Body temperature in juveniles was about 1 ° C higher in midmolt than at the start and end. In molting birds of both age groups, the temperature in the middle part of the daylight period was higher (by up to about 1° C) than in the morning or evening, but this trend was absent before or after molt.
The body feathers of juveniles serve for only 3-9 weeks (till postjuvenile molt) and are weaker (with fewer barbs and barbules) than those of adults, which last a year. On the other hand, the flight and tail feathers of juveniles, which are not renewed at post-juvenal molt, are just as substantial as those of adults. Between the end of one molt and the start of the next, nearly a year later, the body plumage of adults lost one-third of its weight; but in the flight and tail feathers the loss was negligible. The plumage was at its heaviest at that stage of molt when most feathers were growing.
Both adults and juveniles increased in weight during moult, and for some weeks afterward, through increases in allthree body components: lean dry material, water, and fat. In addition, the water contentof Bullfinches was higher during molt than at other times; the extra water was localized in the growing feathers, which, at peak molt, contained up to 7 per cent (1.1 g) of the total water in the bird.
A diurnal cycle was superimposed on the seasonal trends. Whether molting or not, birds lost water, lean dry material and fat overnight and replaced them during the day. Moreover, the diurnal fat cycle increased in amplitude, irrespective of molt, as the season advanced and nights became longer and colder. In contrast, the diurnal cycle in lean dry material was much greater in amplitude during heavy molt than at other times. It is suggested that at peak molt the breakdown of body protein occurred overnight (and was replaced during the day), and that the amino acids so released might be used partly to support feather growth which continued at the same rate as by day.
By analogy with data from chicken feathers, the total amino acids required for feather synthesis by molting Bullfinches was calculated. It is concluded that the total protein required for feather growth is probably set by its cystine content, for this amino acid is present in feather keratin at much higher concentration than in the proteins of plant seeds, on which Bullfinches feed during molt. Possibly the birds can lighten the demand for cystine by synthesizing it from surplus methionine.
Adult Bullfinches produced about 2 g of feathers during a molt of 11-12 weeks, and juveniles 1.5 g in 7-9 weeks; in both, keratin was synthesized, on the average, at 27 mg per day.
From carcass analyses, it seems that Bullfinches were able to meet entirely the nutritional demands of molt from food eaten at the time; they did not show the long-term protein deficit associated with the molts of certain species, and had fat contents as high as did nonmolting birds caught at the same time.

Newton, I. (1969): Winter fattening in the Bullfinch. Physiol. Zool. 42: 96-107.

Bullfinches in England were heavier in December/January (23 - 26 g) than in October/November (22 - 25 g). Water comprised 64 % of this weight difference, lean dry material (mainly protein) 24 %, and fat 12 %. The significance of thelarge seasonal changes in protein are not known.
It is unlikely that the increased fat deposits significantly improved the virds' insulation in the colder months, and the insulating potential of the plumage was no better then than in October.
The fat served mainly as an overnight energy reserve; in the colder months, with longer nights, more fat was laid down each day and more lost each night. Some Bullfinches also stored whole seeds in their gullet prior to roosting, but these contributed less than one-fourth of the overnight energy requirements in October/November and less than one-fifth in December/January.
In all four months, most birds were found to contain some fat at dawn, This fat store was greater and, in the absence of feeding, probably sufficient for several more hours of activity in December/January (when food was generally scarcer) than in October/November. After using all their fat, starving Bullfinches can live for a few hours by breaking down body protein, but at no time could the birds have fasted a whole day and survived. As a supplement to reduced food intake, stored fat could contribute to the energy requirements over only a few days, though periods of food shortage may last up to several weeks. "Winter" fat cannot therefore be regarded as a long-term reserve, and only by obtaining sufficient food each day to lay down fat for overnight use can teh birds survive from one day to the next.

Newton, I. (1972): Finches. Collins, London.

Nisbet, I. C. T., W. H. Drury & J. Baird (1963): Weight-loss during migration. Part I: Deposition and consumption of fat by the Blackpoll Warbler Dendroica striata. Bird-Banding 34: 107-138. Internetversion av denna uppsats

[CP] This and the following papers are important antiques, like the above one by Newton. Blackpoll Warblers were ringed and studied in Massachusetts and again on Bermuda; from this comparison the authors drew conclusions about the energy consumption during migration flight. Values, conclusions, theoretical positions are no longer up-to-date, but any student of fat accumulation, weight loss on migration etc. should have some basic knowledge of the contents of this paper. Use more modern estimates, where such exist, the next generation involves a.o. Raveling & Lefebvre 1967 and Hussell and Lambert 1980.

(...)3. During 3-24 September 1962, most birds caught at Round Hill, Massachusetts, weighed only 10-15 gm. Arrivals of light birds followed cold frosts. In late September and early October more heavy birds were caught; most of the birds which were caught put on weight rapidly during rainstorms and appeared to depart immediately after clearing. Immatures appeared to put on weight more slowly than adults.
4. At Drumlin farm, Massachusetts, many more very heavy birds (16-23 gm) were caught. In at least two different years a group of birds of average weight 20.8 gm has been caught in late September and early October, and three such birds have been killed during nocturnal migration at this time. It is suggested that this is the usual departure weight of the species.
(...)6. New England is an area where Blackpoll Warblers pause in their migration for several weeks to put on fat for overseas flight.
(...)8. On the nights of 2-3 October 1962, many heavy Blackpoll Warblers (average weight 17.3 gm) were attracted to the Bermuda lighthouse: these birds were part of a flight from New England which passed Bermuda without stopping. Lighter birds (11-16 gm) stopped on Bermuda on several days later in October, but these birds had not flown directly from New England.
9. Forty-five birds kept overnight in dark cages lost weight at an average rate of 0.062 gm/hour.
10. The birds which flew to Bermuda during 1-3 October 1962 lost weight at an average rate of 0.107 ± 0.013 gm/hour; this figure may be an over-estimate but is unlikely to be an under-estimate. This gives an upper limit for their average power consumption of 1.02 ± 0.13 Kcal/hour, only about 2.0 times the resting power consumption in spite of a load of 6 - 10 gm of fat. It is argued that they lost little or no water during the flight, but this needs further study.
10. Blackpoll Warblers have sufficient fat-reserves when they leave New England to fly non-stop for 105-115 hours. This is enough for a non-stop flight to the mainland of South America in the usual weather in which they migrate.

/"New England" designates the six northeastern states of USA, Maine, New Hampshire, Vermont, Massachusetts, Rhode Island and Connecticut, first colonized by Englishmen./

Nisbet, I. C. T. (1963): Weight-loss during migration. Part II: Review of other estimates. Bird-Banding 34: 139-159. Internetversion av denna uppsats

1. Eight field-studies of migrating birds are summarized, and an estimate of the rate of weight-loss obtained from each. Except for two doubtful estimates, all the figures lie between 0.56 percent and 1.3 percent of total body-weight per hour; the estimate for the Blackpoll Warbler is the lowest and probably the most reliable. It is suggested that a reasonable average for the power consumption of migrating passerines is 0.076 Kcal./gin. total weight/hour: this figure will be too high if some of the observed weight-loss consists of water.
2. A laboratory measurement of the power consumption of a hovering hummingbird was 0.206 Kcal./gm. total weight/hour, which is 2.7 times that suggested for passerines in forward flight.
3. Nine theoretical calculations of the power consumption of flying birds are reviewed. Their predictions range from far below the lowest field-estimate to far above the highest. The most reliable estimates are those from semi-empirical theories based on the measurements of hummingbirds. Aerodynamic theories are at present unsatisfactory, but at least one offers promise for future development. Physiological theories suggest that some very fat birds expend power at a rate approaching the maximum possible for the organism. Physiological and aerodynamic theories which agree for small birds diverge for large birds, and the discrepancy should be tested by experiments on large birds.

Norman, D. (1992): The growth rate of Little Tern Sterna albifrons chicks. Ring. & Migr. 13: 98-102.

One hundred and six Little Tern chicks have been weighed and had their wing length measured in the colony at Gronant, Clwyd, Wales, in two different years. Forty of them were re-measured on dates at least six days later and growth rates calculated. There were big differences in the weather in the two years of this study but no difference in growth rate. Chicks put on weight quickly and reached close to their full weight at an age of about 10 days. After an initial period of two or three days with litle growth, wing length increased approximately linearly at a rate between 6.5 and 7.5 mm/day, with a mean of 6.8 ± 0.2 mm/day. Chicks could just fly at 14 or 15 days of age, with wing lengths of about 100 mm, some 70 mm shorter than the mean wing lengths of fully-grown juveniles. They were fed on small fish, mainly sandeels and "Whitebait", and satiated chicks were frequently seen to refuse food. The growth rate measured here is probably close to the maximum achievable in this habitat and possibly limited only by the birds' metabolism.

Norman, S. C. (1987): Body weights of Willow Warblers during autumn migration within Britain. Ring. & Migr. 8: 73-82.

The relationship between weights of Willow Warblers and the autumn migration strategy of the species was investigated by examination of weights of first-autumn birds captured at two inland sites in Britain over the period 16 July to 30 September. The migration 'season' was divided into two periods and the data from each compared. No account was taken of the sex of the birds and only individuals which had completed moult were used. Capture times throughout the season were standardised and actual weights were used.
Mean overnight weight-loss was found to be about 8 % of total body weight and mean diurnal weight-gain about the same over the first period of the season, slightly more over the latter period. Results implied that this order of increase was needed by birds to meet overnight metabolic requirements and, that they migrated at weights virtually equivalent to normal roosting levels.
A migration strategy is proposed based on the findings of Baggott (1975, 1986) that approximately 13 % of total wet weight of first-autumn Wilow Warblers comprises fat deposits. It is suggested that the majority of Willow Warblers use normal evening weight levels for successive short-stage migratory flight (<300 km) through Britain, and that about 5 % of body fat is held available in reserve for the funding of additional energy demands which might be imposed should adverse weather conditions be encountered.
Estimates of the 'fat' loadings birds require to traverse France and for trans-Saharan flight from Iberia are discussed.


Okill, J. D. & S. Wanless (1986): Weights and wing lengths of juvenile Gannets Sula bassana from Noss and Ailsa Craig. Ring. & Migr. 7: 125 - 129.

Weights and wing lengths were taken of juvenile Gannets caught on the sea after they fledged from Noss and also from juveniles found dead at the base of the cliffs of Ailsa Craig. Both parameters varied widely, but in general, juveniles weighed more and had shorter wings than adults. Juveniles on Ailsa Craig had significantly shorter wings and weighed more than their counterparts on Noss. This was attributed to differences in cliff structure at the two colonies.

O'Reilly, K. M. & J. C. Wingfield (1995): Spring and autumn migration in Arctic shorebirds: same distance, different strategies. Am. Zool. 35: 222 - 233.

The Arctic is an extremely inhospitable region for most of the year, but during the summer months it bursts with life. A major proportion of avian species nesting in the Arctic are shorebirds (order Charadriiformes, suborder Charadrii). They migrate thousands of kilometers from their wintering grounds to take advantage of abundant food resources each summer and display a variety of migratory strategies. In an attempt to classify this variation, not only between spring and autumn migration, but within a migration, we present four categories. These relate to the distance a species generally flies between stopovers: short distance bout, intermediate distance bout, long distance bout, and combinations. We then explore further differences between spring and autumn migration. Spring migrants experience poor weather and decreased food availability as they fly north. Many cope with huge flocks, which serve as protection from predators, but may also reduce foraging efficiency and increase aggression. In contrast, autumn migrants generally encounter favorable weather and ample food. Flock sizes are usually smaller, thus foraging efficiency is higher and aggression lower than during spring migration. Physiologically, spring migrants are preparing for breeding and reproductive hormones are secreted. In the Western Sandpiper (Calidris mauri), luteinizing hormone levels are higher for spring than autumn migrants. Late spring migrants have higher testosterone levels than either early spring migrants or autumn migrants. Corticosterone levels are also higher in spring vs. autumn migrants. Although spring and autumn migrants travel similar distances, their strategies differ behaviorally and physiologically.

Ormerod, S. J., S. J. Tyler & J. M. S. Lewis (1986): Biometrics, growth and sex ratios amongst Welsh Dippers Cinclus cinclus. Ring. & Migr. 7: 61 - 70.

Biometric data were collected from over 500 Dippers in mid and south Wales between 1978 and 1985. Mean wing lengths for both sexes were significantly shorter in first years than in older birds. For combined ages, males and females could be separated above and below wing length 92 - 94 mm; the sex ratio did not differ from 1 : 1. Wing lengths in both sexes were shorter than in Scandinavian Dippers, although Welsh males had significantly longer wings than males in south west Scotland. Body weights in both sexes increased during moult and prior to breeding, and a 'condition factor' is suggested from regression of weight on wing length. Weights of nestlings indicated sex-related differences, although it was impossible to sex every nestling using weight alone.

Ormerod, S. J. (1989): The influence of weather on the body mass of migrating Swallows Hirundo rustica in South Wales. Ring. & Migr. 10: 65 - 74.

Factors influencing the body condition of Welsh Dippers were assessed from 1153 measurements of mass and wing length, and 789 measurements of tarsal length, made on over 1000 individuals. Conditions indices were derived by comparing actual masses with those predicted from regressions of mass on wing length and tarsal length after log : log transformation. The indices gave an indication of the mass of a bird for a given body size.(...)

Ormerod,, S. J., S. J. Tyler (1990): Assessment of body condition in Dippers Cinclus cinclus: potential pitfalls in the derivation and use of condition indices based on body proportions. Ring. & Migr. 11: 31 - 41.

Factors influencing the body condition of Welsh Dippers were assessed from 1153 measurements of mass and wing length, and 789 measurements of tarsal length, made on over 1000 individuals. Conditions indices were derived by comparing actual masses with those predicted from regressions of mass on wing length and tarsal length after log : log transformation. The indices gave an indication of the mass of a bird for a given body size.(...)


Pearson, D. J. (1975): The status, migrations and seasonality of the Little Stint in Kenya. Ring. & Migr. 8: 91 - 108.

(Only weight data quoted) Weights were almost all within the range 18 - 26 g from November to March. A few higher weights (up to 38 g) were recorded in the rift in autumn, mainly in adults. In spring, mean weights increased in the rift to above 30 g (highest weights above 40 g), but comparable fattening was not found on the coast. Analysis of carcasses from Magadi showed that most October-March birds contained only 4-10 % lipid (as percentage of total weight). Some August-September birds were fatter (20-30 % lipid) and most late April-May birds were very fat (30-40 % lipid). Pectoral muscle total weight and lean dry weight were significantly greater at times of migration August-September and late April-May, than in the wintering period.(...)

Pearson, D. J., C. Backhurst, & D. E. Backhurst (1979): Spring weights and passage of Sedge Warblers Acrocephalus schoenobaenus in Central Kenya. Ibis 121: 8 - 19.

Pedersen, J. & J. R. G. Hislop (2001): Seasonal variations in the energy density of fishes in the North Sea. J. Fish Biol. 59: 380 - 389.

The energy density (ED, kJ/g wet mass) of saithe Pollachius virens, haddock Melanogrammus aeglefinus, whiting Merlangius merlangus, Norway pout Trisopterus esmarki, herring Clupea harengus, sprat Sprattus sprattus, sandeel Ammodytes marinus and pearlsides Maurolicus muelleri, from the North Sea, increased with total length, LT. However, there was not always a significant (P > 0·05) linear relationship between LT and ED. Seasonal differences in ED were obvious in mature fish, while geographical differences were insignificant. For all species there was a highly significant correlation (P < 0·0001) between the percent dry mass of the fish (DS) and ED. A general relationship was established for gadoids and sandeel ED = -3·1492 + 0·3459 DS and herring ED= -4·6395 + 0·4170 DS. Thus seasonal and size-specific data on ED needed for bioenergetics and gastric evacuation models can be determined simply from DS, which is considerably less costly and time consuming than calorimetry or proximate analysis.

Peiro, I. G. (1995): Patterns of abundance, body-mass dynamics and habitat use of the Reed Warbler Acrocephalus scirpaceus in two reedbeds of south-eastern Spain. Ring. & Migr. 16: 100 - 108.

The abundance, vertical distribution and body mass of the Reed Warbler were studied in two reedbeds of different structure and composition at Hondo Natural Park, south-eastern Spain during the breeding and non-breeding cycle in 1992-1993.
Adult abundances showed similar patterns in both reedbeds, with two initial peaks in the first half of May and the second half of July. Juveniles however showed asynchronous cycles, possibly as a result of a delay in the incubation period in the dense reed. The birds' abundance was related to breeding activity, expressed as the percentage of birds with brood-patch, since catches declined when birds had brood patches.
Weight of adult birds was positively correlated with fat-score, bill volume and tarsus-length, whereas in juveniles body mass was correlated with fat and feather-length. The seasonal changes in body masses were similar in both adults and juveniles, with the greater mean weights obtained in the autumn months.
The patterns of habitat use showed that the vertical distribution of birds differed between the two reedbeds studied. Reed Warblers occupied mainly the upper levels in the densest reedbeds and the middle layers in the cleared reedbeds.

Pennycuick, C. J. (1975): Mechanics of flight. In: Avian Biology. Vol. V., pp. 1 - 75. Farmer, D. S. & J. R. King (eds.). Academic Press, New York and London.

Pettersson, J. (1983): Åldersbestämning av tättingar och vadare. Rapport från Ottenby fågelstation nr 1, 2nd rev. edition.

CP: Pictures "defining" the fat rankings used in the paper below are given here. The liver still shows in rankings "4" and "5", intestines show in rankings 0 - 3, and some still in ranking "4". In addition there is a ranking for superfat birds: "6". This ranking scale has been widely applied in Sweden; Busse & Kania 1970 is quoted as source, but as a matter of fact the Ottenby scale deviates strongly from the Operation Baltic scale, unfortunately the two scales simultaneously used in the Baltic are not compatible. Pettersson is intent on continuous development, Busse & Kania on defining "catch structures" for the eye.

Pettersson, J. & D. Hasselquist (1985): Fat deposition and migration capacity of Robins Erithacus rubecula and Goldcrests Regulus regulus at Ottenby, Sweden. Ring. & Migr. 6: 66-76.

To investigate migration strategy we have studied the visually observable fat deposits of Robins and Goldcrests and made calculations of flight distance capacity. High fat deposits in Robins and Goldcrests after one night migrations to Ottenby suggest that these birds could migrate two or more nocturnal stages without refuelling. The long periods needed to recover depleted fat reserves could be one reason for Robins storing fat for more than one night's migration. Recoveries in the same autumn of Robins ringed at Ottenby confirm our suggested pattern of fat deposition and migration strategy.
CP: There is a good linear regression WEIGHT on RANKING with sample-sizes order of magnitude 1 - 4.000 birds. Still, it is obvious, that the relation based on the Ottenby scale is slightly bow-shaped.

Piersma, T. & N. Van Brederode (1990): The estimation of fat reserves in coastal waders before their departure from northwest Africa in spring. Ardea 78: 221 - 236.

To derive realistic equations for evaluating the fat loads of waders before their departure from NW Africa in spring, we have analysed samples of waders inadvertedly killed during catching operations in Morocco, Tunisia and Mauritania. We studied the relationships between body and fat mass and structural size variables. Part of the original variation in body mass was attributable to a constant relative water loss between capture and first weighing, and body mass values used in the subsequent analyses were corrected accordingly. In the four species for which large samples were available (Knot, Little Stint, Dunlin and Redshank), linear regressions of fat mass on body mass indicated that 50-60 % of the differences in individual body mass is due to differences in the total fat mass. In all four species wing length correlated well with lean mass, suggesting that this dimension is generally a better structural size variable than total head, bill and tarsus plus toe length. Only in Dunlins, bill length correlated best with lean mass. Multiple regression with fat mass as the dependent variable and body size and structural size variables as independent variables, showed that only those dimensions which correlated with lean mass, contributed significantly to the explained variance in fat mass in addition to body mass. An alternative regression model in which body mass was estimated from fat mass and structural size variables and then reformulated, did not lead to improved predictive equations. The suggested equations to estimate fat mass in individual Knots, Little Stints, Dunlins and Redshanks allows the estimation of fat mass of the heaviest birds with an accuracy of ca. 30 %, but with a much lower accuracy in light birds (all estimated values within 100 % from the true value). (...)

Piersma, T. & J. Jukema (1990): Budgeting the flight of a long-distance migrant: changes in nutrient reserve levels of Bar-tailed Godwits att successive spring staging sites. Ardea 78: 315 - 338.

A single population of Bar-tailed Godwits Limosa lapponica was studied before departure from their wintering grounds on the Banc d'Arguin in Mauritania, and at a spring staging site in the Dutch Wadden Sea. On the Banc d'Arguin the godwits started gaining body mass in the course of March at rates of about 2.8 g per day in males and 3.2 g per day in females, before leaving north between 25 and 27 April. In the Wadden Sea, body mass increased linearly over the entire staging period (29 April-31 May) at 5.6 g per day in males and 7.5 g per day in females. Half of the mass increase was due to the deposition of fat, the other half to increases in fat-free tissue (mainly muscle protein). If the godwits flew at the heights with most tail wind assistance by varying their flight altitude up to 5.5 km, they gained an average wind assistance of 18 km/h, which would add considerably to their estimated air speed of 57 km/hour. At an average ground speed of57 + 18 = 75 km/hour the godwits would cover the required 4300 km in 57.3 h.During this flight, males and females were estimated to lose 136 g and 178 g respectively. Since half of these mass losses consisted of fat, they represent energetic equivalents of 3163 kJ and 3857 kJ respectively, leading to estimated flight costs of 55 kJ/hour for males and 67 kJ/hour for females. The energy reserves stored on the Bamc d'Arguin would not enable the Bar-tailed Godwits to cover the distance between W. Africa and the Wadden Sea in one flight without making good use of favourable high-altitude winds.

CP: The estimates of this paper are outdated, look for more recent values.

Piersma, T. (1990): Viewpoint. Pre-migratory "fattening" involves more than the deposition of fat alone. Ring. & Migr. 11: 113 - 115.

Piersma, T. (2002): Energetic bottlenecks and other design constraints in avian annual cycles. Integr. Comp. Biol. 42: 51-/67.

Pilastro, A., F. Spina & P. Micheloni (1998): Geographical variation in pre-migratory condition of Swallows Hirundo rustica in Italy. Ring. & Migr. 19: 67-74.

In order to investigate pre-migratory strategies of Swallows in Italy, simultaneous ringing activities were carried on during three focal days (September 6-8 1996) at 24 different roosts scattered across the Italian peninsula and main islands. A total of 8,771 Swallows was ringed, out of which 81.6 % were juveniles and 18.2 % adults. Among the latter 28.3 % were classified as males, and 71.7 % as females. Most birds had already completed their body moult; a higher fraction of birds still in active moult was found among adults. The frequency of adults with active primary moult was intermediate between the values reported for Northern-Central and Southern Europe respectively. Mean body mass values were higher in adults, which were also fatter than juveniles. Both in adults and in juveniles, fat score was significantly lower in moulting birds. A high variability in mean body mass values and frequency of fat birds was found between roosts. The mean body mass of the 25 % heavier birds corresponded to 24.1 % and 30.5 % of the lean body mass for juveniles and adults respectively. The situation observed in early September does not indicate a clear north-south gradient in the average physical conditions of pre-migratory Swallows, suggesting the use of roosts as sites of concentration of birds staging and fattening in the surrounding areas. The observed latitudinal gradient in the frequency of adults at the roosts might be related to earlier southward movements of more northern birds.

CP: Fat rankings are discussed in the text but not given explicitely! I suspect that the ranking material was very irregular. And: were balances calibrated against each other? A good, coordinated effort, but the presentation is not transparent.

Potts, G. R. (1971): Geographical variation in pre-migratory condition of Swallows Hirundo rustica in Italy. Ibis 113: 298-305.


Raveling, D. G. & E. A. Lefebvre (1967): Energy metabolism and theoretical flight range of birds. Bird Banding 38: 97-113. Internetversion av denna uppsats.

At present, there exists a considerable amount of empirical and theoretical estimates of weight loss and energy expenditure of migratory flight, which Nisbet (1963) has excellently reviewed. He noted the weaknesses inherent in many prior estimates and concluded that power consumption in small birds is about 0.076 kcal/gm total weight/hr. This conclusion, based primarily on calculated weight loss for a small sample of Blackpoll Warblers appears low, in our opinion, for small migrating passerines. We propose, instead, a simple method for estimating flight energy requirements which we believe yields more reasonable results for a wider range of species. Our method proposes that the energy expenditure of sustained flight can be estimated for many species as twelve times the standard metabolism rate. Comparison of the predicted estimates and available empirical data provides reasonable support for our method of estimation. A discussion of these data and our curve is presented along with some comments provided by Nisbet et al. (1963). (...)

Redfern, C. P. F., Topp, V. J. & P. Jones (2004): Fat and pectoral muscle in migrating Sedge Warblers Acrocephalus schoenobaenus. Ring. & Migr. 22: 24 - 34.

Increases in fat and pectoral muscle mass are important physiological changes associated with migration, but the extent to which these are linked is uncertain. The relationship between fat and pectoral muscle in first-year Sedge Warblers was investigated using the carcasses of 20 birds that died by flying into the lighthouse on Bardsey Island, North Wales, UK, in autumn 1996, and data for fat and pectoral muscle scores from 3,281 Sedge Warblers ringed while on migration through the Wetland Trust Reserve at Elms Farm, Sussex, UK, between the end of July and early October in the years 2000, 2001 and 2002. For the Bardsey sample, the mass of tracheal pit fat (claviculo-coracoid fat body) correlated with the masses of fat at other body sites, and was a good measure of overall fat levels. Lean dry pectoral muscle mass did not correlate with the mass of tracheal pit fat, suggesting that pectoral muscle mass and fat mass are independent measures of body size. The link between fat and pectoral muscle mass was investigated further using the Elms Farm data. Wing length, time of capture, fat score and pectoral muscle score all made significant contributions to overall body mass. Although fat and pectoral muscle scores were correlated overall, analysis by year and fat score range supported the idea that these can vary independently. Analysis of fat and pectoral muscle scores by different ringers suggested that fat scores were consistently applied in different years; however, pectoral muscle scores may be harder to standardise between ringers. In summary, we suggest that fat and pectoral muscle mass increase independently in preparation for migration, but the factors which determine variation in pectoral muscle scores in relation to fat scores in different years are unknown.

Rheinwald, G. (1975): Gewichtsentwicklung einiger nestjunger Höhlenbrüter. J. Orn. 116: 55 - 64.

The weight development of 4 species of passerines breeding in nest boxes was investigated: Parus major, P. caeruleus, P. palustris and Ficedula hypoleuca.(...)
Generally the distribution of weights of the nestlings was symmetrical with small range in the first days. Three days after hatching the distribution was asymmetrical to the right and the range increased heavily. In the middle of the nestling time the asymmetry and the range had reached their maximum and remained there until the young could not longer be weighed.
In the species investigated the line connecting the daily averages is sigmoid and nearly equals the adult weight at the 14th day (tits) and the 12th day (Pied Flycatcher), respectively.(...)

Ricklefs, R. E. (1967): A Graphical Method of Fitting Equations to Growth Curves. Ecology 48: 978 - 983.

No summary; Ricklef compares the behaviour of the logistic equation, Gompertz's and Bertalanffy's growth equation. From text: In form, the Gompertz, and to a greater extent the von Bertalanffy curves differ from the logistic curve in a marked slowing of growth rate and prolongation of the growth period in relatively later stages of growth. [Inflection points 1/2 (log.), 1/e (G.), 8/27 (vB.)]

Ricklefs, R. E. (1969): Preliminary Models for Growth Rates in Altricial Birds. Ecology 50: 1031 - 1039.

The rate of growth in body weight of birds is not correlated with nestling mortality, but rather is a function of the adult body size of the species and the mode of development of the young. To examine the adaptive basis of growth rates, models are formulated which incorporate the mortality of the young, their energy requirement and their rate of growth into a function which determines the productivity of the offspring. This function is maximized when growth rate occurs as rapidly as possible, at the expense of brood size. Optimally, one young should be raised which grows as rapidly as the parents are able to supply food. Because this is not observed in nature, and because of othe inefficiencies due to the form of the growth curve, it is postulated that physiological constraints, based on the functional organization of the body plan, limit growth rate. This may occur either through bottlenecks placed on the rate at which food can be processed and utilized, or by problems of allocation of energy and tissues among mature and embryonic functions.

Ricklefs, R. E. & S. C. White (1981): Growths and energetics of chicks of the Sooty Tern (Sterna fuscata) and Common Tern (S. hirundo). Auk 98: 361 - 378. Internetversion av denna uppsats.

We measured the energy budgets of chicks of the Common Tern (Sterna hirundo) on Great Gull Island, New York and of the Sooty Tern (S. fuscata) on the Dry Tortugas, Florida. The respiratory energy requirement was determined by measuring oxygen consumption in a closed system. We calculated the growth energy requirement from the lipid and protein contents of a series of chicks spanning the range between hatching and fledging. Young Common Terns grow about twice as rapidly as young Sooty Terns. In most respects, their development follows a similar course, but energy budgets calculated for the two species differed in several ways. (1) Maintenance metabolism was lower in the Sooty Tern owing to its warm environment. (2) Sooty Terns allocated more of their energy intake to lipid accumulation from an earler age. (3) In the Sooty Tern, the allocation of energy to growth initially was high, but its absolute amount decreased steadily throughout the growth period. In the Common Tern, both growth and maintenance energy allocations increased rapidly during the first half of the development period. (4) In Sooty Tern chicks energy metabolism approached its maximum rate (135 kJ/day) by the end of the first third of the development period, after which it leveled off. In the Common Tern, energy metabolism increased from about one-quarter of its maximum during the first 5 days after hatching to its maximum of 200 kJ/day during the third week of the postnatal development period.
Although these observations support the hypthesis that slow growth in pelagic seabirds is selected to reduce the energy requirement of the chick, our energy budgets also suggest that a doubling of the growth rate by the Sooty Tern would increase the maximum energy requirement of the chick by only 20 % and the total feeding requirement of the adult by only 5 %.Moreover, the levels of water in muscles suggest that the Sooty Tern develops mature function earlier than does the Common Tern, which in itself might be sufficient to account for the slower growth of the first species.

Ricklefs, R. E. (1983): Avian postnatal development, in: Farner, D. S., King, J. R. & K. C. Parkes (eds.): Avian Biology. Vol 7: 1 - 83. Academic Press, New York.

Ricklefs, R. E. (1984): The optimization of growth rate in altricial birds. Ecology 65: 1602-1616.

I have developed models relating the growth of altricial birds to annual production of fledglings, a measure of evolutionary fitness. In the models, growth rate influences production through its effects on the power requirements of the nestling and the length of the nestling cycle, the latter in turn affects probability of survival to fledging and number of broods reared per year. The models were evaluated to determine whether empirically reasonable estimates pf power requirements and nesting mortality resulted in predicted optimum growth rates within the range of observed values. By and large the models were successful. They do not adequately explain the reduced growth rates of tropical altricial species compared to their temperate-zone counterparts. Moreover, they do not address the phenomenon of slow growth in self-feeding, precocial species. But the confirmation of the model for many altricial birds suggests that it may be possible to understand interspecific variation in growth rates as the result of adaptations to levels of predation and the requirement for, and availabilty of energy to the nestling.

Riddiford, N. & R. C. Auger (1983): Weight gains and resumption of passage by Willow warblers on spring migration. Bird Study 30: 229-232.

Observations and trapping at Dungeness (Kent) suggested that spring Willow Warblers moved on rapidly during the day of arrival. Gains in weight were demonstrated through calculating mean weights by time intervals, in relation to time after sunrise, and presenting these in sub-samples based on homogeneous wing-length classes. These indicated steady weight gains during the day (particularly the morning when the birds fed most actively) for each size class, and suggested that 0.4 - 0.7 g weight gains were sufficient to allow resumption of passage.

Robson, D., Barriocanal, C., Garcia, O. & O. Villena (2001): The spring stopover of the Reed Warbler Acrocephalus scirpaceus in northeast Spain. Ring. & Migr. 20: 233 - 238.

The patterns of spring stopover of the Reed Warbler were investigated at a coastal site in northeast Spain between 1993 and 1997. Birds arrived in good physiological condition, with a mean fat load of 10 %. There was a seasonal decline in wing length and fat load, suggesting that larger and fatter birds migrate earlier. Only 4.3 % of the birds stopped over for more than one day. These birds carried lower fat loads and had a later capture time than transients. In addition they tended to show no increase in mass during their stopover, although this can be an effect of birds in different stages of their migratory journey. Birds at our site had a mean stopover length of one day, enough to gain sufficient fat stores to reach the next feeding site. This strategy may be expected in spring, when birds are under selection pressure to minimize migration time.

Rodriguez, M. (1985): Weights and fat accumulation of Blackcaps Sylvia atricapilla during migration through Southern Spain. Ring. & Migr. 6: 33 - 38.

The weights and fat of Blackcaps during autumnal and spring passages through Southern Spain have been studied. The birds passing during autumn have a mean weight of 19.2 g, more than birds which winter in these areas (Herrera & Jordano 1981); 82.5 % winter in the Mediterranean Basin (probably in Northern Africa) and 17.5 % are long-distance migrants. The latter birds weigh more than 21 g, and they can be considered as long-distance migrants (Langslow 1976). The birds passing in spring, with a mean weight of 22.3 g, are distributed into two groups with different weights and with different fat accumulations which must represent different migratory strategies related to their breeding areas.(...)

Rubolini, D., Gardiazabal Pastor, A., Pilastor, A. & F. Spina. (2002): Ecological barriers shaping fuel stores in barn swallows Hirundo rustica following the central and western Mediterranean flyways. J. Av. Ecol. 33: 15 - 22.

The crossing of ecological barriers is among the most energy-demanding and risky phases of migration. Scanty field data exist on the relationship between ecological barriers and pre-migratory fuel storing in songbirds. The aim of this study was to analyse whether the distance to be covered across ecological barriers can be considered as a factor affecting pre-migratory fuel stores in barn swallows Hirundo rustica following the two main western European flyways, funnelling through Iberia and Italy. Data refer to 13029 swallows and were collected during July - October in 1997-1998 at 19 roost sites, scattered over Spain and Italy (south of 43°N). During the post-breeding phase (PB, July-August) energy stores did not differ significantly between the two geographical areas, whereas during the pre-migratory phase (PM, September-October) swallows in Italy carried larger energy stores than those in Spain. Assuming the swallows leave for migration from the fuelling site, we found a significant positive correlation between the width of ecological barriers and an average index of energy stores for each roost site during the PM phase. The width of ecological barriers (along a N-S migration route) was expressed as (1) the distance between the roost site and the coast of North Africa (representing the Mediterranean Sea), and (2) the distance between the roost site and the southern margin of the Sahara desert (the total width of ecological barriers) The weaker correlations obtained when considering only the Mediterranean as a barrier suggests that swallows may cross the desert without substantial refuelling in North Africa. Hence, we showed that fuel stores have a degree of population-specific variability among Italian and Iberian barn swallows and that the extension of ecological barriers may play a role in determining the amount of stores needed for the migratory flight.

CP: Iberian and Italian birds may head for quite different latitudes in Africa; the discussion totally ignores what has been common knowledge for fifty years. Birds heading for West Africa, Central Africa and South Africa most probably head for different stopover areas. This is what happens when ornithology loses touch with its own history, with knowledge acquired over decades, and it's a rather common phenomenon. It's easy to pull a trick like this in Journal for Avian Biology, which goes like a blind terrier for alleged evolutionary adaptations.


Scebba, S. & G. Moschetti (1996): Migration pattern and weight changes of Wood Sandpiper Tringa glareola in a stopover site in southern Italy. Ring. & Migr. 17: 101 - 104.

408 Wood Sandpipers were examined at a stopover site in the central Mediterranean near the southern Italian coast during the pre- and postbreeding migration. Some details about the timing of passage of adults and young birds are given. The weight changes are examined; birds arriving in the spring had very low mean body mass and could well have overflown non-stop across the Mediterranean as well as perhaps the whole or part of the Sahara. Summer migrating birds use the artificial ponds both as resting area and as a refuelling site to accumulate fat.

Scott, R. E. (1961): Weight change in male Reed Buntings. Bird Study 8: 152 - 154.

(A study at Dungeness of newly arrived Reed Bunting males in February) (...)2. Weights obtained indicate increase during the day with a slowing in rate of increase or slight fall around noon.(...) 4. Individuals vary up to 2.5 gms. in the 10 hour day considered, peak weight occurring at dusk and lowest weight near 12.00 hours.

Stolt, B.-O. & J. Mascher (1962): Untersuchungen an rastenden Blaukehlchen (Luscinia s. svecica) in Uppland, Mittelschweden, unter besonderer Berücksichtigung der Körpermasse und Gewichtsvariationen. Vogelwarte 21: 319 - 326.

[CP]: This is history, and the results are not conclusive (cf. Lindström et al. 1985), but the paper belongs in the mental luggage of any student. Bluethroats lost 2 g overnight; referring to Helms & Drury 1960 the authors assume that 50 % of this was due to loss of stomach/intestine contents and 50 % due to fat metabolization. This weight loss was made good for in the daytime, but no more.

Summers, R. V. & M. Waltner (1979): Seasonal variations in the mass of waders in southern Africa, with special reference to migration. Ostrich 50: 21-37.

Swaddle, J. P., Witter, M. S., Cuthill, I. C., Budden, A. & P. McCowen (1996): Plumage condition affects flight performance in common starlings: implications for developmental homeostasis, abrasion and moult. J. Avian Biol. 27: 103-111.

Variation in length and asymmetry of wing primary feathers can arise from a breakdown of developmental homeostasis, feather abrasion and incomplete growth during moult. Indirect predictions have been made concerning the impact of primary length and asymmetry on the flight ability of birds, but they have not been explicitly tested. Here we provide evidence from both natural variation in primary feather condition and experimental manipulations of primary feather length and asymmetry to indicate that these factors influence aspects of flight performance in the Common Starling Sturnus vulgaris. Damaged and incompletely grown primaty feathers reduce escape flight performance. Experimentally reduced primary lengths reduce take-off speed; increased primary asymmetry decreases aerial manoeuvrability. A comparison of the experimental and natural plumage data indicates that birds may be able to adapt to a change in wing morphology, perhaps reducing the effects of feather loss or damage on flight. The results from this study indicate that primary feathers are under strong stabilising selection to maximise developmental homeostasis and reduce feather asymmetry. These findings are also of ecological importance to the damage-avoidance and moult strategies of these birds. This is the first experimental evidence to indicate a quantitative reduction in flight performance with feather lengths and asymmetries typical of those observed during flight feather moult and feather damage in any species.

Swaddle, J. P. & M. S. Witter (1997): The effects of molt on the flight performance, body mass, and behavior of European starlings (Sturnus vulgaris ): an experimental approach. Can. J. Zool. 75: 1135-/1146.

The physiological and energy costs of avian molt are well documented, but indirect consequences such as changes in flight performance have received less attention. Here, we report two experiments that investigated flight performance, body mass regulation, and behavior in captive starlings (Sturnus vulgaris). In the first experiment, we found a U-shaped shape in take-off escape performance during natural molt: birds ascended at the shallowest trajectories during midmolt. Birds' body mass was also reduced during molt. In the second experiment, we manipulated the plumage of starlings to simulate different stages of flight-feather molt. This allowed us to separate the aerodynamic costs of feather loss from the physiological costs of feather synthesis normally associated with plumage growth. Through observations of flight (take-off, aerial manoeuverability and level flapping-flight speed) and behavioral parameters, we demonstrated that birds in simulated molt have reduced flight performance and reduced body mass. These birds also decrease the time spent performing energetically costly activities and seek areas of relative protection. In the longer term, some aspects of performance return to pretreatment levels, implying compensation for the plumage manipulations. Our results demonstrate that molt incurs significant functional costs that may play an important role in the adaptive radiation of molt strategies and molt patterns observed in avian species.

Swaddle, J. P., Williams, E. V. & J. M. V. Rayner (1999): The effect of simulated flight feather moult on escape take-off performance in starlings. J. Avian Biol. 30: 351-/358.

We investigated the effects of the plumage changes associated with moult on the anti-predator take-off performance of European Starlings Sturnus vulgaris. By altering the plumage to simulate moult, we have isolated the biomechanical consequences of changes in wingform from the underlying physiological and metabolic changes. that may occur during natural moult. Previous analyses of avian take-off performance have relied on descriptive observations of wingtip kinematics or dual measures of take-off speed and angle. We have developed a novel method using the energy gain per wingbeat as a measure of overall take-off performance. The advantages of this measure compared with previous approaches are that it summarises the potential trade-off between height gain and speed gain, and can be related directly to lift on the wings. Analysis of high speed (100 Hz) video tapes indicated that birds in simulated moult suffer a reduction in total energy produced during the second wingbeat of take-off, resulting in slower take-off speed. This reduction in take-off performance is also associated with a marked change to the pattern of the movement of the wingtip during flight;moult-manipulated birds appear to reverse the wingtip at the top of the downstroke although there is no associated change in wingbeat amplitude or duration. Birds appeared to be able to regain, in part, their flight performance within 6 days of the manipulation, as take-off speeds returned to pre-manipulation levels. This partial return to pre-manipulation flight performance was associated with an alteration in pattern of movement of the wingtip during take-off. The relevance of this adaptation to birds in natural moultis discussed. Any reduction in take-off performance is likely to influence directly individual behaviour and survival; hence the ablity to quantify take-off in different species under a common currency is of general ecological importance and will enable predictions to be generated and tested concerning the effects of natural moult in wild birds.


Tierney, M., Hindell, M. & S. Goldsworthy (2002): Energy content of mesopelagic fish from Macquarie Island. Antarctic Science 14: 225 - 230.

The water and calorific content of fifteen species of mesopelagic sub-Antarctic fish from Macquarie Island were determined. Mean percent water content was 69-82 %. Calorific content was highly variable between species, especially in the Myctophidae, where it ranged between 22.62-59.26 kJ/g dry weight. The water and calorific content varied with size class within a species, with the smallest size classes generally having the lowest water content but highest calorific content. These values will be useful for future assessment of energetic transfer between trophic levels and energetic modelling of Southern Ocean ecosystems.

Tucker, V. A. (1974): Energetics of natural avian flight. In: Paynter, R. A. (ed.) Avian energetics: 298 - 328. Nutt. Orn. Cl., Cambr. Mass.


Uttley, J. D. (1992): Food supply and allocation of parental effort in Arctic Terns Sterna paradisaea.. Ardea 80: 83 - 91.

Male and female reproductive strategies differ, resulting in differences between the time and energy budgets of the sexes during reproduction. Consequently, the responses of the sexes to environmental conditions during breeding may not be the same: Recently Arctic Terns breeding in Shetland have experienced reduced food availability, whereas those breeding in Orkney have not. Male and female Arctic Tern in Orkney contribute equally to incubation, but males brood young chicks (less than 10 days old) less and feed them more, than females do. Males in Shetland contribute less than females to incubation during laying, but the brooding and feeding effort of the two sexes are equal when caring for young chicks, due to a switch from brooding to foraging by females. The changes in allocation of effort during laying may allow the laying of a larger and better quality cluch than would otherwise be possible, through reducing female energy expenditure and increasing courtship feeding. Changes later in the breeding season may increase potential chick survival or be a manifestation of reduced reproductive effort and increased somatic effort.


Veiga, J. P. (1986): Settlement and fat accumulation by migrant Pied Flycatchers in Spain. Ring. & Migr. 7: 85 - 98.

Pied Flycatchers migrating through Spain showed a marked tendency to settle in some areas. During the stay their weight and fat reserves increased. The density of settled birds and some unidentified seasonal features were major factors determining the settling rate of newly arrived birds. The level of fat reserves at arrival also seemed to be involved in the decision as to whether to stay or not. The tendency to settle was stronger in juveniles than in adults, apparently as a consequence of their lighter weight on arrival. The length of stay was related to the rate of gain in weight. The role of age-related factors on the decision to depart is discussed in the light of differences between the settlement and movement patterns of juveniles and adults.

[CP]: A private ranking-scale based on the "fullness of the furcular cavity" was in use.

Wallgren, H. (1954): Energy metabolism of two species of the genus Emberiza as correlated with distribution and migration. Acta Zool. Fenn. 84: 1-110.

Ward, P. (1963): Lipid levels in birds preparing to cross the Sahara. Ibis 105: 109-111.

Wood, B. (1982): Weights and migration strategy of Blackcaps Sylvia atricapilla wintering in Tunisia. Ibis 124: 66-72.


Ydenberg, J., Butler, R. W., Lank, D. B. & (2002): Trade-offs, condition-dependence and stopover site selection by migrating sandpipers. J. Avian Biol. 33: 47-55.

Western sandpipers Calidris mauri on southward migration fly over the Gulf of Alaska to the Strait of Georgia, British Columbia, where they stop for a few days to replenish reserves before continuing. In the Strait, individuals captured on the extensive tidal mudflats of the Fraser estuary (oom 25000 ha) are significantly heavier (2.71 g, or > 10 % of lean body mass) than those captured on the small (< 100 ha) mudflat of nearby Sidney Island. Previous work has shown that the difference cannot be attributed to seasonal timing, size, age or gender effects, and here we compare predictions made by six hypotheses about a diverse set of data to explain why partway through a migratory journey of order of magnitude 10000 km, birds have such different body masses at two stopover sites within 40 km of each other. The 'trade-off' hypothesis - that the large Fraser estuary offers safety from predators, but a lower fattening rate, while the small Sidney Island site is more dangerous, but offers a higher fattening rate - - made six successful predictions, all of which were upheld by the data. All other hypotheses failed at least one prediction. We infer that calidrid sandpipers arriving in the Strait of georgia with little fat remaining (and therefore low body mass) choose to take advantage of the high feeding rate at small sites like Sidney Island because they are less vulnerable to avian predators than are individuals with higher fat reserves, who instead elect to feed at large open sites like the Fraser estuary mudflats.


Zwarts, L., Blomert, A.-M. & R. Hupkes (1990): Increase of feeding time in waders preparing for spring migration from Banc d'Arguin, Mauritania. Ardea 78: 237 - 256.

In order to increase body mass during the 4-6 weeks before their departure from the Banc d'Arguin in spring, some waders, such as Dunlin, Knot, Bar-tailed Godwit, increased the total time they spent feeding. They fed more at night and fed throughout neap tides and at high temperatures, circumstances in which feeding activity was depressed in winter. In other species, however, such as the Little Stint, feeding time did not increase during the premigration period. In winter, feeding time and body mass in the 14 wader species studied were negatively associated, but this trend disappeared during the premigration period. Nocturnal feeding was particularly important in the smaller waders, but the larger waders also began to feed at night later in the season. It is suggested that only when pressed for time, waders will feed at times when the yield from the feeding is low.

Zwarts, L., B. J. Ens, M. Kersten & T. Piersma (1990): Moult, mass and flight range of waders ready to take off for long-distance migrations. Ardea 78: 339 - 364.

Wader species wintering on the Banc d'Arguin increased their body mass by about 40 % during the 4 - 6 weeks before their departure in spring. This estimate is based on 1) the empirical fact that most waders which had finished or suspended their body moult into summer plumage were heavy and thus ready to take off, and 2) the assumption that only the heaviest birds in the population left, which allowed the mass of disappearing waders to be estimated from counts and the frequency distribution of body masses in samples of captured birds. The mass gain on the Banc d'Arguin is just over 1 % per day, when expressed as a proportion of winter mass. A review of studies on waders preparing for migration shows that 1) the total migratory reserve adds 20-80 % to winter mass, 2) the rate of mass gain is 0.1-4 % per day and 3) the period of mass increase lasts four weeks on average, but longer if waders prepare for spring migration on the wintering areas. We suggest that all wader species leaving the Banc d'Arguin at the end of April and the beginning of May are able to reach SE and NW Europe without refuelling. This seems only possible if current equations to predict flight range systematically underestimate this range, even when the energetic benefits of favourable winds at high altitude are taken into account.


Åkesson, S., A. Hedenström, A. & D. Hasselquist (1995): Stopover and fat accumulation in passerine birds in autumn at Ottenby, southeastern Sweden. Orn. Svec. 3: 81-92.

Stopover duration and fat accumulation were studied during autumn migration at two sites near Ottenby, Öland, southeastern Sweden in 1985 and 1986. The species are Thrush Nightingale, Barred Warbler, Lesser Whitethroat, Whitethroat, Willow Warbler and red-backed Shrike. We captured the birds in mistnets between 10 July and 20 August and recorded visually the fat class and measured the body mass. Post juvenile moult was scored on juvenile birds. In several of the species fat class and body mass increased with day of season (Thrush Nightingale, Barred Warbler and Whitethroat), while in the Lesser Whitethroat there was a reduction in fat class and body mass with day of season. Recaptures revealed that the highest daily increase in body mass was 2.7 % in a Willow Warbler and a Red-backed Shrike, while a Barred Warbler showed a maximum daily body mass increase of 2.4 %. The duration of stopover in migrants varied between 2 and 7 days.

79 entries 29.3.06.

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