26/10/2018
A new study has documented the
astonishing distances covered each year by Willow
Warblers breeding in the north-easternmost part of the species'
range.
Using geolocators, the
researchers tracked three male yakutensis Willow Warblers from their
breeding grounds in Chukotka, Russia, to their wintering range in sub-Saharan
Africa.
They found that all three
individuals were very similar in the routes they took to their final wintering
sites in southern Tanzania or northern Mozambique, in their use of stopover
sites in south-west Asia and in the overall timing of migration. In total, this
southward migration route amassed to a distance of between 12,000 and 13,000 km
– one of the longest among songbirds, despite the warblers weighing less
than 10 g.
The Willow Warblers initially
followed a north-west migratory route when leaving the breeding area, and after
crossing the initial longitudes, the routes were gradually directed more
towards west and south-west until they reached the first stopover site. The end
of this initial part of the migration occurred during the autumn equinox, with
data suggesting a slow but continuous migration, with one bird showing a
potential stop lasting only a few days. After the main stopover period in south-west
Asia, the birds changed to a southerly migration route, along which they
reached the wintering sites in Eastern Africa. The passage farther south in
East Africa followed at a very narrow longitudinal range for all birds. In
total, it took the warblers between 93 and 118 days to complete their epic
migration from the Russian breeding areas to the first sub-Saharan stopover
site.
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