Hooded Warbler
Ecoregional Scale Conservation Planning

Made possible through a partnership with the National Wetlands Research Center

Whip-poor-will (Caprimulgus vociferus)
The whip-poor-will is a Neotropical migrant with a more northerly range than the chuck-will’s-widow, although the ranges of the two are not exclusive and overlap broadly across the CH. Whip-poor-wills have declined 1.8 percent per year since 1967 in the CH (Sauer and others 2005; Table 005 Table 005) , where the species is a Bird of Conservation Concern and has a regional combined score of 17 Table 001 (Table 001) . A large proportion of the continental population (35.5 percent) breeds in the CH (Panjabi and others 2001). The species is a rare breeder in the WGCP (regional combined score = 13).
Relative abundance of Whip-poor-will, derived from Breeding Bird Survey data, 1994 - 2003.
image courtesy of www.whatbird.com

Natural History:
Owing to its cryptic coloration and crepuscular activity pattern, the whip-poor-will is one of the least-studied birds in North America (Cink 2002). Breeding habitat in the CH and WGCP consists of xeric deciduous and mixed forests with a sparse understory. In addition, birds are often associated with open areas, such as rural farmland, powerline and roadway rights-of-way, clearcuts and selectively logged forest, old fields, and reclaimed surface mines. Shaded forest stands with limited ground cover adjacent to open areas for foraging provide ideal whip-poor-will habitat. The species is usually absent from extensive areas of closed canopy forest, but no data exists on minimum or maximum forest patch size thresholds. Small isolated woodlots in a Maryland agricultural landscape are not used (Reese 1996, cited in Cink 2002). Grand and Cushman (2003) found whip-poor-wills in Massachusetts strongly associated with complex patch shapes and high contrast edges. Nests are placed on the forest floor, and hatching is synchronized with the full moon to optimize foraging time of adults. The species does not appear to be strongly territorial; home range sizes range from 2.8–11.1 ha.

Model Description:

The habitat suitability model for whip-poor-will contains four variables:

  • landform
  • landcover
  • successional age class
  • the relative composition of forest and open habitats in the landscape

The first suitability function combines landform, landcover, and successional age class into a single matrix (SI1) that defines unique combinations of these classes Table 136 (Table 136) . We directly assigned suitability index scores to these combinations based on relative habitat rankings for vegetation and successional age class associations of whip-poor-wills reported in Hamel (1992).

Whip-poor-wills nest in forest and forage in openings. Therefore, they require landscapes with an interspersion (SI2) of these landcover types. We assumed a landscape with 70 percent forest and 30 percent open habitat was optimal (suitability index score = 1.000; Wilson, pers. comm.) and landscapes with a greater proportion of forest were more suitable than those with less forest cover provided some openings were present Table 137 (Table 137 ; sensu Cooper 1981).

We calculated the overall suitability index score as the geometric mean of the two component factors.

Overall SI = (SI1 * SI2)0.500