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We contextually analyzed the song of the Bobolink (Dolichonyx oryzivorus) to examine the role of sexual selection on song versatility. Recordings were obtained as territorial males were randomly presented with a caged male (a conspecific intruder), a caged female (a potential breeding partner), and an empty control cage. Sound spectrograms created from the recordings were analyzed and an index of versatility was calculated for each male in each manipulation so that individual song variation could be compared among behavioral contexts. These analyses suggest that more complex or versatile song production is being selected intersexually, whereas short repetitive song is intrasexually selected. Published in The Condor,...
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Population growth and decline are particularly sensitive to changes in three key life-history parameters: annual productivity, juvenile survival, and adult survival. However, for many species these parameters remain unknown. For example, although grassland songbirds are imperiled throughout North America, for this guild, only a small number of studies have assessed these parameters. From 2002 to 2006, in the agricultural landscape of the Champlain Valley of Vermont and New York, USA, we studied Savannah Sparrow (Passerculus sandwichensis) and Bobolink (Dolichonyx oryzivorus) demography on four grassland treatments: (1) early-hayed fields cut before 11 June and again in early- to mid-July; (2) middle-hayed fields...
The Earth is warmer today than it has been during most of the last 11,000 years; as warming trends approach unprecedented levels, there is little doubt that future climate change will have profound effects on species conservation and management. Grassland ecosystems and many grassland-dependent birds are particularly vulnerable to rapid shifts in climate variability and associated changes in drought and extreme weather events. For grassland birds, climate change is likely to exacerbate environmental threats such as habitat loss due to shifting agricultural practices and housing sprawl. Our goal was to identify how certain grassland bird species are sensitive to climate variability and which regions have the highest...


    map background search result map search result map Grassland songbird survival and recruitment in agricultural landscapes: implications for source-sink demography. Fledging times of grassland birds in North Dakota and Minnesota Grassland songbird survival and recruitment in agricultural landscapes: implications for source-sink demography. Fledging times of grassland birds in North Dakota and Minnesota