University of New Hampshire
Mentor: Dr. Matt Tarr, Department of Forestry and Wildlife (Cooperative Extension)
Quantifying the reproductive success of a declining shrubland-obligate songbird,the prairie warbler (Setophaga discolor), breeding in an active gravel pit in southeasternNew Hampshire
Shrubland habitats are dominated by low-growing trees and shrubs and they have become increasingly uncommon in New England since the mid 1950’s. In response, populations of many shrubland-obligate wildlife species, including prairie warblers (Setophaga discolor), have also declined. Currently, prairie warblers are a species of international conservation importance and in many parts of their range they rely on human-created shrublands including clearcuts, powerline rights-of-way, old fields, and gravel pits as their primary breeding habitats. In southeastern New Hampshire, prairie warblers occur most frequently in active and reclaimed gravel pits where they often occur in greater abundance than in other shrubland types. No studies to-date have quantified whether gravel pits actually function as “source” habitats that support viable breeding populations of prairie warblers that produce enough young to offset annual mortality, or whether these habitats are “sinks” that support many individuals, but conditions within the habitat (e.g., low food availability, high exposure to predators) reduce reproductive output below the level required to maintain a population without regular immigration. Understanding where these birds reproduce successfully is critical for guiding habitat management and conservation efforts aimed at conserving this declining species. My study will quantify the reproductive success of a population of prairie warblers breeding in a large (50 ha) actively mined gravel pit in southeastern NH. Specifically, I will quantify the abundance and age structure of male prairie warblers, determine the proportion of males that are breeding, and quantify the number of young produced by each female. From these data I will calculate the
annual rate of increase (λ) for this population to determine if enough young are produced to offset expected mortality. I expect that this habitat will support a population consisting primarily of older birds and that the λ will be sufficient to equal or exceed annual mortality.