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Where do the Blackcaps go from Bukowo? A recent paper by BMRS provides a new insight into that topic based on data from geolocators.

By 4 lutego 2021 No Comments

In October 2020 an international scientific journal Proceedings of the Royal Society B (B – Biological Sciences) published a paper on Blackcap migration: Individual  variability and versatility in an eco-evolutionary model of avian migration, co-authored by prof. Magdalena Remisiewicz, the Head of our Station. In the study, an international team lead by ornithologists from the Max Planck Institute in Germany summarized data from geolocators on Blackcaps fitted at several locations in Europe, including Bukowo, one of Operation Baltic field stations.

The Blackcap Sylvia atricapilla is a passerine with a complex migration strategy. Its various European populations exhibit a whole range of migratory behaviour. Southern populations are completely sedentary, more northern ones migrate either short distances to winter in the Mediterranean, or take longer, trans-Saharan routes. Directions of their migrations are also diverse – from south-west to south-east, and include a recently developed north-western direction, used by some central European birds that winter in the British Isles. Thus this species is a perfect model to study the evolutionary diversity of bird migration strategies.

Migration routes and wintering areas of Blackcaps were studied with the use of geolocators. They are tiny loggers (the smallest weigh less than 1 gram) which register the intensity of ambient sunlight and time. Upon the recorded time of sunrise and sunset and day length, a dedicated software calculates the geographic coordinates of the sites visited by the bird that carried the device. Because of their small dimensions geolocators can be safely applied to passerines. However, as the device only records the data and does not transmit them, it must be retrieved to download the data. From fifty geolocators fitted on Blackcaps at Bukowo since 2015 we were able to retrieve nine. One more was retrieved by dr Piotr Piliczewski, our collaborator, who fitted geolocators on Blackcaps at another ringing site in Western Pomerania. Data from all our retrieved loggers were used in the paper.

The research demonstrated the existence in Central Europe of a narrow zone of intergradation between Blackcap populations migrating in SW and SE directions, and the hybrids from that zone migrated to S. The study showed that birds wintering in the British Isles originate from a broader area of Europe than previously thought. The paper also presented the routes of the individuals with geolocators, including those from Bukowo. “Our” Blackcaps migrated generally in SW direction to spend winter in Iberian Peninsula, north-west Africa, but some also moved in S direction to Sicily and other Mediterranean islands. We hope to retrieve more geolocators in next seasons, which will help us to uncover other secrets of Blackcap migrations.

The full text of the article is available at BMRS website.

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