Origin of Passerine Migratory Waves: Evidence from the Blackcap at a Stopover Site

Abstract

Hundreds of millions birds migrate through Israel every spring, usually in several waves during which a large number of birds are seen flying over Israel for several days, followed by periods in which only a small number are spotted. The aims of this study were to (1) determine whether the spring migration of the blackcap demonstrates a wave pattern, (2) determine the effect of weather conditions en route on the number of blackcaps arriving and forming each wave, and (3) use morphological characteristics and stable isotope composition of the feathers to examine the hypothesis that early arriving blackcaps represent populations breeding in low latitudes while later ones represent northern populations.We found that (1) our first hypothesis was fully supported, and blackcaps arrive to Israel in "waves"; (2) weather conditions, and in particular wind speed and direction, were significantly related to the number of blackcaps captured; and (3) our morphological and δ C-13 data suggest that birds from the early season originated from more southern latitudes and/or more western longitudes within the breeding range of blackcaps.

Limited flexibility in departure timing of migratory passerines at the East-Mediterranean flyway

“…In the blackcap, early females had shorter wings than late females. This trend is partially in agreement with a previous study on the blackcap in Israel 61 , which suggested that blackcaps (both sexes) from the early migration phase had shorter wings than the later arrivals. The same study found that the shorter wing individuals breed at a more southerly or westerly destination in Europe 61 .…”

“…This trend is partially in agreement with a previous study on the blackcap in Israel 61 , which suggested that blackcaps (both sexes) from the early migration phase had shorter wings than the later arrivals. The same study found that the shorter wing individuals breed at a more southerly or westerly destination in Europe 61 . The longer wings of the later arrivals may therefore facilitate adjustment to the fast spring vegetal growth in breeding grounds in eastern Europe compared to the western range 82 .…”

“…These three species breed in Europe and Western Asia and spend the main non-breeding season in the Afrotropical zone. The blackcap captured in Israel during migration are a mixture of breeding populations spanning from eastern to northern Europe, and its main non-breeding range spans across different regions in Africa 61 (Fig. 1 ).…”

Temporal migration patterns between natal locations of ruby-throated hummingbirds (Archilochus colubris) and their Gulf Coast stopover site

“…The second factor we tested, fuel load, did not support our prediction that there would be differences in the cost of migration across the range, rather individuals from both northern and southern latitudes arrived with similar fuel loads. These results are similar to other studies [ 8 , 35 – 37 ] that found no relationship between fuel load and migratory distance. Moreover, most individuals in this study, as well as ruby-throats from this location previously described by Zenzal and Moore [ 15 ], typically arrived with some fuel stores.…”