22.03.2021: Blackcaps (Sylvia atricapilla) are one of the most common bird species in Europe, and the most common in Austria. Across their range, they show a multitude of migratory strategies. Birds in the South are mostly sedentary, and the further North they breed, the longer their migrations get. Some populations can be found South of the Sahara Desert in winter. A research group from the Max-Planck Institute for Evolutionary Biology in Plön (Germany) – in collaboration with researchers from the Austrian Ornithological Centre (AOC) at the Konrad Lorenz Institute of Ethology in Vienna – set off to investigate the variability of their migratory strategies, using geolocators which are attached to the bird´s bodies.

While birds in southern Europe are primarily so-called resident birds (i.e. they remain in one area all year round), the further north they breed, the furthest they migrate. Some populations even spend the winter in Africa, south of the Sahara. In this collaboration with researchers from the Max-Planck Institute for Evolutionary Biology, scientists from the Austrian Ornithological Centre (Vetmeduni/University of Vienna) investigated the variability of the migration strategies of blackcaps.

Bird migration "tracked"

Austria is particularly suitable as a study area because a multitude of indicators suggests that a blackcap “divide” runs across the country. Bird populations move along this route either to the southwest – towards the Iberian Peninsula - or southeast - to East Africa, south of the Sahara.

In order to precisely track their migration, researchers caught over 200 blackcaps all over Austria and equipped them with small position loggers, so-called “geolocators”. A geolocator is a type of tachograph that is placed on the birds' backs. A sensor on a memory chip records the intensity of daylight every few minutes and saves it with precise information on the time and date. This makes it possible to determine the exact position of the animals at a particular point in time. "The data obtained from this actually show a very narrow zone – around 30 km around the 14th degree of longitude – where Eurasian blackcaps migrate in an intermediate direction ranging from southwest to  southeast," says Ivan Maggini from the Austrian Ornithological Institute.

Migratory birds react to changes in the environment

These results enable the scientific examination of various theories regarding the evolution and the genetic control of migration in blackcaps and other migratory birds. Another interesting result of this study is that one of the geolocator-marked birds spent the winter in Great Britain. "This newly established wintering area has been enjoying increasing popularity for 50 years and is related to the feeding of garden birds by bird lovers," explains Wolfgang Vogl, also an expert at the Austrian Ornithological Institute. While it was previously assumed that these “Great Britain overwinterers” were birds from the area between southern Germany and central Austria, it has now been established that birds from all European populations are repeatedly found there. It seems that blackcaps have, within a short period of time, discovered the more favorable climatic conditions in Great Britain and have adapted their migration behaviour accordingly.

According to Maggini and Vogl, this study shows how a common species such as the blackcap can help understand the flexibility and adaptability of migrating bird species to rapidly changing environmental conditions.

 

Read the full study here: https://royalsocietypublishing.org/doi/full/10.1098/rspb.2020.1339

The article "Individual variability and versatility in an eco-evolutionary model of avian migration" by Delmore K. et al. was published in Proceedings of the Royal Society of London, Series B.