NESTING HABITAT RELATIONSHIPS OF SYMPATRIC CRESTED CARACARAS, RED-TAILED HAWKS, ANDWHITE-TAILED HAWKS IN SOUTH TEXAS

Abstract

We quantified nesting-site habitats for sympatric White-tailed Hawks (Buteo albicaudatus) (n = 40), Red-tailed Hawks (B. jamaicensis) (n = 39), and Crested Caracaras (Caracara cheriway) (n = 24) in the Coastal Sand Plain of south Texas. White-tailed Hawks and Crested Caracara nest sites occurred in savannas, whereas Red-tailed Hawk nest sites occurred in woodlands on the edge of savannas. White-tailed Hawk nest sites were in shrubs and trees that were shorter (3.5 ± 1.0 m) and had smaller canopy diameters (5.5 ± 2.1 m) than those of Red-tailed Hawks (10.1 ± 2.0 m, 13.7 ± 5.8 m) and Crested Caracaras (5.6 ± 1.7 m, 8.5 ± 3.5 m). Red-tailed Hawk nest sites had higher woody densities (15.7 ± 9.6 plants) and more woody cover (84 ± 19%) than those of White-tailed Hawks (5.6 ± 5.8 plants, 20 ± 21%) and Crested Caracaras (9.9 ± 6.7 plants, 55 ± 34%). Crested Caracara nest sites were in dense, multi-branched shrubs composed of more living material (97 ± 3%) than those of White-tailed (88 ± 18%) and Red-tailed hawks (88 ± 18%). Nest sites of White-tailed Hawks, Red-tailed Hawks, and Crested Caracaras were similar to random samples from the surrounding habitat indicating that preferred nesting habitat was available for each of these species at least within 60 m of active nest sites. Nest tree height, along with woody plant and native grass cover best discriminated nest sites among the three raptor species. There was no overlap at Red-tailed and White-tailed hawk nest sites in vegetation structure, while Crested Caracara nests were in habitat intermediate between the two other species. Partitioning of nesting habitat may be how these raptor species co-exist at the broader landscape scale of our study area in the Coastal Sand Plain of Texas.