Canopy Characteristics Affect Reproductive Success of Golden-Cheeked Warblers

Authors: J. A. Klassen, M. L. Morrison, H. A. Mathewson, G. G. Rosenthal, and R. N. Wilkins

The golden-cheeked warbler (Setophaga chrysoparia), listed by the U.S. Fish and Wildlife Service as endangered in 1990 due primarily to habitat loss and fragmentation, is a Neotropical migrant songbird that breeds exclusively inmature juniper–oak (Juniperus–Quercus) woodlands in central Texas, USA. Previous studies suggested suitable breeding habitat consists of >35% canopy closure (with 50–70% cover optimal), and ≥10% oak composition. However, little is known about this species’ habitat relationships at the southwestern edge of its breeding range. Therefore, within this portion of the species’ breeding range, we investigated influences of canopy closure and tree species composition on pairing and reproductive success of golden-cheeked warblers during 2009 and 2010. We used remote sensing and ground sampling to acquire variables to describe habitat characteristic, and we estimated pairing for breeding and reproductive success by golden-cheeked warblers. We found successfully breeding pairs in areas with >20% canopy cover, 35% juniper composition, and only 3% oak composition. A logistic model for pairing success retained juniper, oak, and the interaction between these 2 variables, and the model for reproductive success retained juniper, canopy closure, study area, and the interaction between canopy closure and study area. Our results expand our knowledge of habitat conditions that warblers use for breeding, thus expanding the range of habitat management options available for this species during breeding season.

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