Nearctic Knots (Calidris canutus canutus) in S. Sweden in autumn and winter.

In a survey of the winter distribution and migration of Nearctic and Siberian Knots Dick et al. 1976 (Ardea 64: 22-47) point out the Irish Sea, the North Sea and the Bay of Biscay as wintering areas of Nearctic birds, while Siberian Knots spend the winter in Africa. In Iceland Nearctic birds occur as transmigrants in July and August, reaching Denmark and the Waddensea in August. Roos 1984 (Anser, suppl. 13) believes, that the migration of Nearctic Knots "leaves Sweden untouched", but a decade later Blomqvist & Lindström 1992 (WSG Bull. 64, Suppl.: 91-94) connected spring observations (March - May) of Knots in S. Sweden with the Nearctic populations.

It could be added that there are Swedish winter recoveries from Great Britain and the Waddensea as early as the seventies, and that a couple of these are quoted by Dick et al.: Morups tånge (Halland) 1y 29.8 and Visingsö (Lake Vättern) 2y+ 27.7, both recovered in Norfolk in March, Ottenby 2y+ 13.8 to Scotland in February. A couple of Ottenby Knots from Charente-Maritime/Gironde (i.e. the French part of the Bay of Biscay) in November probably belong to the same group; if they had been of Siberian origin they should have been in Africa by that time. Furthermore there is at least one bird from the mouth of Vistula to the French part of the Bay of Biscay (1y 30.8 - 25.11; Gromadzka (1991): Wader ringing at Vistula mouth. Autumn 1990), and the British annual report for 1986 (Ring. & Migr. 8: 171) tabulates five British Knots from Poland; Nearctic birds may be hidden here, too.

There is still another material from the Baltic. In a short communication 1980 (Beitr. Vogelkunde 26: 234 - 236) and another in Wader Study Group Bulletin (51: 53 - 55) H. W. Nehls suggested that Nearctic Knots are regular autumn visitors to the German Baltic area; by that time (the late eighties) there were five - six spring recoveries from the North Sea of birds ringed in the former German Democratic Republic and a spring bird (on its way to Iceland) in Balsfjord in N. Norway. These birds probably enter the western parts of the Baltic by way of S. Norway, i.e. they follow the route Skagerack-Kattegat-the Belt Sea/the Sound.

Average bill lengths from feathers in Nearctic and Siberian Knots and of Knots ringed in the Bay of Wismar in autumn are shown in the table below (data from Nehls), mean values of 29 juvenile autumn birds (20.8 - 16.10) and 6 winter birds from the Falsterbo peninsula have been added for comparison:

As could be expected German and S. Scanian autumn juveniles have similar mean values, and with average bill-length 32.8 mm six winter birds agree with both the mean value of Nearctic Knots and that of S. Scanian juveniles in autumn. Another indication that autumn Knots in Scania are of Nearctic origin was delivered by a recovery in the winter season 95-96: ringed 1y Falsterbo peninsula 4.10.95, dead Scheveningen, Holland 5.2.96. In spite of this recovery and similar recoveries from Germany and Poland, we still know practically nothing about the way of "entry" to the Baltic. Out of 16 Knots (15 1y, 1 2y+) controlled at Langenwerder and ringed elsewhere in the same autumn, 10 came from Poland, 2 from Ottenby (Sweden) and 4 from S. Norway (the latter migrating on a south-easterly course). At the same time Swedish catches indicate that Nearctic birds may occur both inland and along the Baltic and Kattegat shores in late summer and autumn; the bird from Lake Vättern 27 July to Norfolk is particularly remarkable; on what course and altitude do such birds enter the Scandinavian air territory? It is difficult to believe, that a fairly "maritime" species like the Knot would be inclined to fly inland from Kattegat in summer, and in some years there are summer observations of Knots as wide apart as Lake Kvismaren (Närke; inland), Lake Ånn (Jämtland; inland) and Haparanda Sandskär (Gulf of Bothnia). (Someone ought to fit all these pieces together).

Occurrence of Nearctic Knots on inland localities in Sweden as well as along the Baltic coasts could indicate a broad-front entry from N or NW of birds flying at high altitude at least in July and August, while strong winds from NW and high water levels probably cause the occurrence of (Nearctic) Knots in the Sound and the German Baltic in late autumn. The ratio Nearctics : Siberians in late summer and autumn is a matter for conjecture, before any far-reaching conclusions are drawn from existing recoveries, there should perhaps be more information about the complete time-table of Siberian Knots; in autumn many Siberian Dunlin (to: Dunlin Calidris alpina phenology and biometry in the Sound area, S. Sweden.) occur late in the Baltic area - why not a contingent of Siberian Knots as well?

The fact that rather substantial flocks may be involved in late autumn even in Germany is shown by 32 newly arrived Knots at Hiddensee/Rügen 9.11.93 (Ber. Vogelw. Hidd., Heft 11, 1994), 23 of these still lingered behind on 25 November in spite of frost and early formation of ice. A flock of the same magnitude (49 ex) wintered on the isle of Måkläppen (Falsterbo Peninsula) in 1989/90 (Fåglar i Skåne 1989) and when this is written (Jan. 98) 20 - 30 Knots are sticking to Lundåkra Bay in the Sound and have good prospects of riding out the winter there. These birds never leave the Baltic area and dispersal from Germany to the Swedish west coast and the Belt Sea is likely to cause at least the early spring observations in the same areas.

The Scanian material was collected by Ulf Lundwall, Per Nothagen, Peter Olsson and Christer Persson, most birds were caught at the spits of Skanör. First manuscript 18.1.98, English version 23.1.02.

Till "Öresund - ett strömmande vatten"

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