Songbirds set long-distance migration record

Date: November 15, 2018

Source: Lund University:

Researchers at Lund University in Sweden have studied flight routes to determine how far willow warblers migrate in the autumn. The results show that the willow warbler holds a long-distance migration record in the ten-gram weight category -- with the small birds flying around 13,000 kilometres or longer to reach their destination.

The recently completed study investigated willow warblers that breed during the summer in north-east Russia. Biologists at Lund University together with Russian researchers from Magadan, close to the Kamtjatka Peninsula, managed to get a good overview of the route and distance travelled by the small birds during their autumn migration.

The measurements were taken by small data loggers attached to the backs of the birds. The next year, the birds were recaptured and the researchers downloaded and processed the data.

From their breeding habitats in eastern Siberia, the willow warblers fly to staging areas located in south-west Asia and the eastern Mediterranean. From there, they continue to their winter destinations, located in Kenya and Tanzania -- a distance of around 13,000 kilometres.

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Marathon Willow Warbler migration uncovered

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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Research reveals why males outnumber females in bird world

Date: July 7, 2016

Source: University of East Anglia

Female birds 'fly the nest' from sparsely populated breeding sites leaving behind small groups of lonely males -- according to new research from the University of East Anglia.

Research published in the Journal of Animal Ecology shows for the first time the causes of skewed sex ratios among small and declining bird populations.

The findings reveal how female birds are thought to be choosing busier breeding locations -- where habitat is often better, males are more abundant, and the ratio of males to females is more equal.

Lead researcher Prof Jenny Gill, from UEA's School of Biological Sciences, said: "Many migratory bird populations are declining and very small local populations are becoming more common.

"If females prefer places where males are more abundant, small populations are likely to decline even faster.

"However, the unpaired males will continue singing throughout the breeding season in a bid to find a mate, and so we may be underestimating declines in these small populations. We wanted to find out whether this was happening."

The research team used British Trust for Ornithology (BTO) ringing data to explore the extent, causes and consequences of varying sex ratios in breeding populations of willow warblers (Phylloscopus trochilus) across the UK.

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