Impacts of forest fragmentation on health and condition of passerine birds in the U.S. Midwest

This project evaluated how forest fragmentation impacts the health and condition of a declining flagship forest species, the Wood thrush (Hylocichla mustelina).

This was done through a comparison of Wood thrushes occurring in SE Michigan forest patches that were in different stages of human-driven fragmentation (i.e. big vs. small fragment size). To that end, we investigated several key disease-related factors: in addition to avian malaria prevalence, we examined changes in fragment vegetation characteristics, vector populations, as well as changes in the immune systems of resident birds.

Increasing habitat fragment size was positively associated with improved general condition of resident birds. Thus, Wood thrushes in smaller fragments were in poorer shape and had an altered immunological profile indicative of infection. In addition, birds on larger, higher quality fragments, were more likely to behave aggressively towards decoys, most likely because they were actually nesting and thus compelled to defend their territories and offspring.  

(Support by: Department of Agriculture)