An Urban, Suburban, Rural Red-Tailed Hawk Nesting Habitat Comparison in Southeastern Wisconsin

Abstract

Red-tailed hawks (Buteo jamaicensis) nesting in urban environments is becoming more common, yet no studies have documented components of urban nesting habitat. In this study I define, describe, and compare urban, suburban and rural red-tailed hawk nesting habitat in southeast Wisconsin. Nests were located from a vehicle between 1 February and 30 April from 1987 through 1994, and were visited periodically to determine reproductive success. Nest site data were collected when nestlings were 2 to 5 wk old. Habitat data were collected within a 0.04-ha circular plot around the nest tree after fledging. Land-use data were collected within a 1.5-km radius (706.9 ha), and a 0.25-km radius (19.6 ha) of the nests. A nest site was classified as urban if~ 70% of the 706.9-ha area was used for industrial or residential purposes ( developed), rural if </= 30%, and suburban if > 30% and< 70% was developed. The amount of natural, agricultural, residential and industrial land-use within the 706.9 and 19.6-ha areas was determined from 1990 aerial photos. Urban, suburban and rural nest sites were compared. Productivity was not significantly different for urban, suburban and rural nest sites (P = 0.857). Average nesting success for red-tailed hawks in the Milwaukee metropolitan area from 1989 through 1994 (N:426) was 81.9% (R:75.3-92.7%). Productivity for the same 6-yr period averaged 1.43 young/active nest (R:1.13-1.91) and brood size at banding (2.5 to 5 wk) averaged 1.75 young/successful nest (R:1.61- 2.06). Productivity varied significantly (P < 0.001) being higher in 1994 than each of the preceding yr (P:<0.001-0.015). Nest trees for suburban sites were significantly taller than urban sites (P = 0.009) but not rural sites (P = 0.061). Nest closure was statistically identical for the three categories (P = 0.978). Suburban sites had significantly more shrub diversity than urban and rural sites (P = 0.017, P = 0.004, respectively), and had higher shrub density than rural sites (P = 0.044). The 706.9-ha area for urban sites was significantly more homogeneous than suburban and rural sites (P < 0.001, P = 0.001, respectively). Distances between active red-tailed hawk nests for urban sites were > for suburban and rural sites (P = 0.004, P < 0.001, respectively), and distances for suburban sites were> rural sites (P = 0.018). The amount of land with natural cover within the 706.9-ha area for urban nest sites was significantly different for urban, suburban and rural sites (P < 0.001). The amount of natural cover within the 19.6-ha area was identical for urban, suburban and rural sites (P = 0.967). The amount of land with natural cover is a critical nesting habitat component. Natural habitat comprised about 16% of the land within the 706.9- ha area for urban sites; 40% of this area was wooded, and 60% had herbaceous cover. Urban planning should incorporate these amounts of natural habitat to allow for red-tailed hawks and other wildlife to coexist with humans in an urban environment.