Changes in arthropod communities between breeding stages in nests of Great Tits

The biotic and abiotic environments in bird nests change during the nesting cycle as eggs are laid and incubated and nestlings develop and eventually fledge. Nest-arthropod communities have been studied for many bird species and are commonly sampled after young fledge. However, the population dynamics of arthropods in nests are expected to vary over the nesting cycle as a result of the changing nest environment, in symphony with arthropod life cycles and generation times. Few investigators have examined nest arthropod communities at different stages of the breeding period. We collected nests of Great Tits (Parus major) at the egg stage, nestling stage, and after fledging, and extracted nest arthropods using Berlese funnels and identified them to Primary Taxonomic Groups (PTGs). Total arthropod abundance, as well as abundance of fleas, parasitic mites, and adult predatory beetles, was higher during the nestling stage than after fledging. The abundance of beetle mites decreased from the egg stage to fledging, whereas larval predatory beetles and scavenger flies increased. Thus, our results demonstrate important changes in overall abundance, but also in the trophic structure of nest arthropod communities during the nesting cycle. Our results also suggest that nests collected after fledging may give biased information on the abundance of parasites, or nest-arthropod communities in general, during the nestling stage.