Habitat choice and parasite load of migratory populations of the blackcap (Sylvia atricapilla)

1) Is there a difference in microhabitat choice between the different migratory populations of the blackcap (Sylvia atricapilla) that would contribute to the establishment of an isolation barrier between the populations and to assortative mating?

The aim of my diploma thesis is to analyse the hypothesis that there is a significant difference in territory choice between individuals of the different migratory populations of the blackcap (Sylvia atricapilla) summering in the southwest of Germany and eastern Austria. In Freiburg, Germany, intend to asses whether individuals of the newly established northwest (NW) migrating population to the British Isles choose different habitat characteristics than individuals of the population migrating southwest (SW) to the Iberian Peninsula. In Austria, near Linz, I would like to analyse the differences in microhabitats between the NW migratory population and the populations migrating SW and southeast (SE) towards Africa. As the populations live in sympatry in the two countries, finding behavioural differences, like a differing choice in territories, could indicate that these contribute to establishing a spatial isolation barrier between the populations. The creation of such a spatial reproduction barrier, decreasing gene flow, would further contribute to an ongoing divergence between the small northwest migrating population (about 10 % of the whole population) and the populations migrating SW and SE.
The aim is also to asses the hypothesis that a different choice in territories contributes to assortative mating.

I intend to examine these criterions by retrieving birds ringed individually after arrival in the area of Mooswald Freiburg and near Linz in Austria and by measuring different habitat variables in their established territories such as percentage of vegetation covering, song post quality or distance to nearest disturbances. Through isotope analysis of claw tips, taken while ringing the birds, the typical wintering grounds of an individual can be assessed and therefore territories can be specifically assigned to birds of the NW, SW or SE migrating populations. By capturing females when mated and nesting I would like to asses whether assortative mating takes place, to which a different choice in territories could contribute.

2) Does a differing choice in territories of individuals from the different migratory populations of the blackcap (Sylvia atricapilla) create a spatial isolation barrier for the parasites that infest them? Do individuals of the different populations therefore carry different parasites?

To asses this question I intend to combine the analysis of microhabitats of NW and SW migrating birds from Germany as well as of NW, SW and SE migrating birds from Austria with the analysis of the parasites the birds of these populations carry. I would like to asses the hypothesis that birds of the different migratory populations carry different parasites according to their territories. Finding variations in parasites in NW, SW and SE migrating birds could indicate that a different choice in territories creates an isolation barrier for the parasites infesting them. This could further lead to ceasing of gene flow and to divergence of the parasite populations infesting the different migratory populations.

To asses which parasites infest which population birds will be individually ringed after arrival in Freiburg and near Linz and blood samples taken. From these the DNA will be extracted to detect the different parasite species or lineages carried by the birds. After microhabitat analysis I will be able to tell if there is a variation in parasites between the different migratory populations according to their choice in territories.