Evaluating the prevalence and effects of within-nest colonies of the odorous house ant (Tapinoma sessile) on nestling survivorship and success in five species of midwestern birds

The odorous house ant (Tapinoma sessile Say) is a cosmopolitan species found throughout North America. Seasonally polydomous, it nests in a variety of habitats, including in soil, within stem cavities, in houses, and in bird nests. Despite the fact that T. sessile colonies have been known to occupy bird nests for almost a century, few studies have been conducted on the prevalence of this phenomena or the possible affects the presence of these ants might have on bird nestling success. In this study, we document T. sessile colonies inhabiting the nests of eight common midwestern bird species. We also examine possible relationships between the presence of T. sessile colonies and habitat type, bird species, arthropod communities within the nest, nestling stress, nestling parasite load, and fledging success in five bird species. In total, 46 bird nests were examined during the summer of 2014. For each nest, blood and fecal samples were taken from each nestling for white blood cell and intestinal parasite counts, respectively. After the nestlings fledged or died, the nests were immediately collected, frozen, and sieved to remove all arthropods within the nest, which were then ID’ed to order and morphospecies. Overall when species were grouped together we found no significant relationship between the presence of ants and fledging success. Some arthropod taxa were more likely to be found in nests without ants in certain bird species. Future work will examine the activity of ants while bird nests are still active and include a larger sample size.