Swallows Hirundo rustica initiating primary moult in Sweden in autumn

Swallows, both adults and 1y birds, undergo a complete moult in African winter-quarters from September to April (Ginn & Melville 1983, Moult in Birds). Some adults moult one or two primaries in Europe, however, then suspend and resume their moult in Africa (or in the Mediterranean; see below). This fraction grows from north to south; in South Spain 19 % of adults caught at Coto Doñana 27.7-13.8.67 had growing primaries (Bird Study 17: 49-61)), in Germany their share was 5 -10 % (Vogelwelt 97: 121-132), in Switzerland 3 % (Orn.Beob. 72: 119-120). In Sweden, the first moulting adult Swallow (P1 and P1-2 growing) was recorded at Foteviken, S. Scania on 19.8.78 (Vår Fågelvärld 38: 48-49).

During a ringing campaign at SW Scanian roosts (particularly the Foteviken - Klagshamn area, c55.25 N, 13.00 E, and Lake Krankesjön, 55.42 N, 12.28 E) in the autumns 1993-95 we checked particularly for primary moult in all adult hirundines. Out of 310 Swallows investigated 7 (2.3 %) had initiated their moult. The sex ratio males : females was 121/138, 51 birds could not be sexed. Two moulting birds were females, four males, one could not be sexed

Two birds showed an asymmetrical pattern; one female had exchanged P1 of the left wing (26 August) and then suspended, one male had P1 and P2 growing on 16 September, in the other cases the pattern was symmetrical. Data for all birds are given in full below:

1. male, 19 August. P1 growing, 0.4, rest of remiges old.
2. female, 26 August. P1 on left wing fresh, rest of remiges old.
3. female, 14 September. P1 fresh, rest of remiges old.
4. male, 16 September. P1 - 2 0.4 on left wing, rest of remiges old.
5. male, 18 September. P1 0.9, P2 0.3, rest of remiges old.
6. unsexed, 19 September. P1 fresh, rest of remiges old.
7. male, 21 September. P1 fresh, rest of remiges old.

Recoveries of Swallows ringed in Scania are rare and not very informative, the trail ends in the Mediterranean area with spring birds from Malta as extremes. (In 1999 we had our first bird from true wintering grounds, however: 2nd calendar year, Bloemfontein (29.07 S, 26.10 E), South Africa 18.2.99 - contr. male Foteviken (roost) 31.7.99). It would be interesting to learn if there is a second halt - say, in Tunisia, Algeria or Mallorca - where more birds from our area initiate their moult, then suspend and continue their southward flight. Considering the estimated duration of complete moult (150-185 days, i.e. almost half a year) in Africa, there is no time to be wasted, particularly if there is a second migration period by the turn of the year when Swallows move from West to Central Africa (Moreau (1972): The Palaearctic-African Bird Migration Systems; Gatter (1987): Vogelzug in Westafrika: Beobachtungen und Hypothesen zu Zugstrategien und Wanderrouten. Vogelwarte 34: 80 - 92). Such a migration must involve fattening and probably new suspension of moult.

This note was written by Peter Olsson and Christer Persson, published on the web 11.6.99. The material was collected by Kerstin Norrman, Per Nothagen and Peter Olsson.