As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Sunday 11 November 2018

Marathon Willow Warbler migration uncovered


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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