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Occurrence of the Connecticut Warbler increases with size of patches of coniferous forest
Citation:
Lapin, C., M. Etterson, AND G. Niemi. Occurrence of the Connecticut Warbler increases with size of patches of coniferous forest. CONDOR. Ornithological Society of North America, Lawrence, KS, 115(1):168-177, (2013).
Impact/Purpose:
This manuscript describes the research performed by Carly Lapin for her Master’s degree at the University of Minnesota Duluth. It is intended to increase our knowledge of a relatively unstudied forest songbird that breeds primarily in the Canadian boreal forest, but reaches is greatest densities in the United States in the coniferous forests of northern Minnesota. The manuscript will also help inform large-scale management of lowland coniferous forest for protection of the Minnesota Connecticut Warbler (Oporornis agilis) population. The primary audience will be the ornithological community and the forest management community.
Description:
The Connecticut Warbler (Oporornis agilis) is a rare and declining Neotropical migrant that breeds in north-central United States and south-central Canada. To better understand the habitat needs of this species, we analysed habitat and landscape at three spatial scales (buffer radii of 100 m, 500 m, and 1000 m) using 371 observations of Connecticut Warblers in 18 years among 86 sites in 28 forest stands of northern Minnesota. We regressed combinations of habitat variables with two response variables, Connecticut Warbler abundance (the total number of individuals ever recorded at a site or stand) and Connecticut Warbler frequency (the number of years recorded out of 18 years) using a zero-inflated negative binomial distribution and logistic regression, respectively. A subset of models was retained using Akaike’s Information Criterion, and model-averaged predictions were calculated for each combination of buffer size and response variable. When comparing model-averaged predictions to observed data, the best models were those using Connecticut Warbler frequency at the 1000 m buffer (r2 = 0.52). At the 1000 m scale, Connecticut Warblers were positively associated with a combination of large patches of upland coniferous and lowland black spruce forest and were negatively associated with upland deciduous forest. These models were used to create a map of predicted Connecticut Warbler breeding habitat among the areas sampled in northern Minnesota.