An experimental test of whether pied flycatchers choose the best territory for rearing the young. Issue 4 (1st August 2015) - Mäntylä, Elina
Abstract: It is often assumed that birds are able to choose a breeding territory that will later on have the most food for nestlings. Studies on this essential question are, however, few. We studied territory choice of a long-distance migrant, the pied flycatcher Ficedula hypoleuca in southwestern Finland. In one study area, we monitored the territory choice of males via the order of territory settlement. Female territory choice was studied experimentally in another study area where the correlation between male and territory quality was removed by not allowing males a free choice of territory. We defined several habitat characteristics and estimated the abundances of invertebrate prey from air, ground and trees with appropriate traps from the surroundings of the nest sites in both study areas. Against the expectation that parent birds would choose an arthropod-rich territory, neither males nor females seemed to choose those territories that later had the most food for nestlings. There was, however, some evidence that more eggs were laid in territories with more aphids and that more fledglings were produced in territories with high ant abundance. Our findings thus suggest that while it would be beneficial for birds to be able to choose food-rich territories, they may not be able to detect the right cues for doing so early in the breeding season. The possibility and importance of detecting the territories with the best prospects of rearing young may, however, vary among and within seasons and more studies on this topic are clearly needed.