Long-term phenological shifts and intra-specific differences in migratory change in the willow warbler
Submitted by avianbiology on 10 October 2014.
Every year, billions of birds move across the Earth to reach their wintering and breeding grounds. One of these mass movement members is the willow warbler, a long-distance migrant that winters in sub-Saharan Africa and breeds in northern Europe and Asia. This bird only weighs about 8 grams but still travels more than 10000 km across deserts and seas twice a year.
With the onset of global climate change, the phenology of seasons in temperate climates has begun to shift. How this shift affects seasonal timing of life-history events in migratory birds has been widely studied in recent years, and the responses seen appear to be species specific. However, it is still known that birds of e.g. different age and sex have different migratory behaviours, and so responses to climate change could also differ between individual birds depending on these factors. In addition, climatic impacts on bird phenology will not affect one life-history component in isolation but could shift the association between them or resonate through several in parallel. Effectively, migration and reproduction should thus be studied in synergy.
In this study, we have investigated behavioural responses in the three most important life-history components of breeding ground phenology; spring arrival, reproduction and autumn departure in the willow warbler. We have also focused on the within-species details of willow warbler migration, identifying behavioural differences in migratory response between birds of different age, sex, migratory phase and juvenile origin.
The willow warbler’s incredible journey, it’s sheer abundance (it is Sweden’s most common bird species) and it’s melancholy song are all great inspirational attributes of this little passerine that interested us in investigate more of how it copes with being a migrant in a changing world.
You can read the article by following the links below:
Below you can see a short video filmed during the study - Willow warblers keep their nest tidy!