Behavioral flexibility of a declining songbird, the Wood Thrush (Hylocichla mustelina), in suburban forests

Abstract

As urbanization increases, so does the need to understand the mechanisms behind urban biodiversity loss and alternatively, population persistence, as wildlife adapt to novel ecosystems. Wildlife conservation has historically focused on relatively pristine natural areas and large tracts of contiguous habitat, and while those areas are certainly valuable, they are not alone in supporting native wildlife. Smaller, more fragmented, and disturbed natural habitats still support many native wildlife species, including birds. Globally, birds and their common prey, insects, are in decline. My dissertation sought to assess whether suburban forest fragments can support forest nesting species, focusing on the Wood Thrush (Hylocichla mustelina), a declining Neotropical migrant songbird species of conservation concern. First, I investigated the invertebrate communities in forest leaf litter between suburban forest fragments and a larger contiguous forest (hereafter referred to as rural), as Wood Thrush are primarily ground-foraging insectivores. Using mixed effects models and canonical correspondence analysis, I found that suburban forest fragments have higher diversity and biomass of invertebrates than rural forests, likely due to the prevalence of non-native decomposers. In my second research chapter, I examined whether parental behavior at the nest, specifically provisioning, differed between suburban and rural forest, and found that suburban nesting Wood Thrush are provisioning their young at higher rates than their rural counterparts. In my final research chapter, I compared nestling condition between forest types using the scaled mass index method, as well as ectoparasite loads of hematophagous bird blowflies, genus Protocalliphora. Neither ectoparasitism nor urbanization influenced nestling condition. My research indicates that suburban forest fragments are indeed supporting breeding Wood Thrush, although adults nesting in suburban fragments are working harder to raise young of similar condition. Future research on the potential costs of increased provisioning on the adults themselves is necessary, as increased seasonal parental investment can impact lifetime reproductive success. In addition, dietary comparisons between forest types would further assess Wood Thrush behavioral flexibility in suburban habitats, as suburban parents may be provisioning with invertebrates of lesser nutritional quality.The National Science Foundation Graduate Research Fellowship Program, The University of Massachusetts Graduate School Dissertation Research Grant, The Organismic and Evolutionary Biology Research Grant, The Bradford G. Blodget Scholarship Fund for Ornithological StudiesDoctor of Philosophy (Ph.D.