Appendix F – Species Accounts ECOLOGY OF RED-TAILED HAWK IN CALIFORNIA By Carie Battistone July 5, 2012 The red-tailed hawk (Buteo jamaicensis) is a robust, broad-winged hawk that resembles most other hawk species in shape and form. There are 12 subspecies of red-tailed hawks. As is typical for most raptors, red-tailed hawks exhibit distinctive color variations, making differentiation of subspecies difficult. Of the two most extreme are the Harlan's hawk (B. j. harlani) and the Krider’s hawk. The Krider’s does not have its own distinct range and therefore has not been given it own subspecies designation. This hawk is a white variation differentiated by a mostly white tail, white face, pale underwings (Preston and Beane 2009). The Harlan’s hawk was formerly considered a separate species, but is now considered a dark variation of the red-tailed hawk, with black above and below, some white speckling intermixed throughout, and white-gray tail feather mottled or streaked with black and tinged rufous or light brown (Collins and Bloom 2000, Preston and Beane 2009). Other subspecies share key distinguishing features to some extent, such as the rusty tail feathers of the adults, a dark bar on the underwing between the shoulder and wrist (patagial bar), and a banding pattern across the abdomen (belly band) (Palmer 1988, Preston and Beane 2009). Light variations of red-tailed hawk adults exhibit lighter coloration and a dark head, red tail and patagial bar, with little to no markings on the chin, breast, throat, and thighs, with the exception of dark streaks on the belly and flanks (Bent 1937, Palmer 1988). Light morphs from western North America exhibit more ventral rufous streaking than red-tailed hawks in other parts of North America (Clark and Wheeler 2001, Preston and Beane 2009). Dark morph red-tailed hawks are common in Canada and the western United States, and are typically chocolate brown throughout, with some dark morphs having a heavy rufous pattern (Preston and Beane 2009). The patagial bars are obscured by the dark pigmentation; however the rufous tail feathers can still be seen in adults. Juvenile red-tailed hawks have a heavily barred tail that lacks the distinctive rusty tone of the adult, with undertail feathers more faintly barred (Bent 1946, Clark and Wheeler 2001). The most distinguishing feature for juveniles is the two-toned upper wings, with primary flight feathers showing a lighter brown then secondary flight feather (Clark and Wheeler 2001). Juvenile plumage is retained until they reach the breeding age of 2 years. Male and female red-tailed hawks are similar in appearance but express sexual dimorphism, meaning females are generally larger then males. Adult males have a body length of 45 to 56 cm (17.7-22 in), and weigh between 690 to 1300 g (1.5-2.9 lbs); whereas females range from 50 to 65 cm (19.7-25.6 in) in length, and weigh 900 to 1,460 g (2.0-3.3 lbs) (Palmer 1988, Farmer et al. 2009, Preston and Beane 2009). The oldest known wild red-tailed hawk is 30 years and 8 months (Lutmerding 2011); however, most do not attain such an age in the wild. The Bird Banding Lab (BBL) records through 1994 showed out of 5,194 red-tailed hawks recovered, only 31 survived longer then 17 years in the wild, and of these, 11 survived longer than 20 years (Soucy 1995). Red-tailed Hawk Species Account Page 1 of 17 The red-tailed hawk is widely used in falconry due to their even temperament and their ability to hunt and obtain sizable game (Palmer 1988). Falconry take data shows 223 red-tailed hawks were obtained from the wild from 2006 to 2010, 41% of all raptors obtained from the wild during this time frame (CDFG 2012). Of the 223, 5 were adults, 185 were immature, 9 were nestlings, and sex was undetermined for 24. Habitat Red-tailed hawks occupy a variety of habitats. Generally, they prefer open habitat, such as sparse woodlands, grasslands, agricultural regions, and urban areas (Grinnell and Miller 1944, Howell et al. 1978, Palmer 1988, Preston and Beane 2009). They are often found in areas with nearly equal proportions of woodland, pasture and cropland habitat (Bednarz and Dinsmore 1982). Densely vegetated habitat or areas devoid of trees or perches are generally avoided (Bednarz and Dinsmore 1982, Farmer et al. 2009). The highest densities of red-tailed hawks were reported in the oak woodlands of California and Colorado (Fitch et al. 1946). Red-tailed hawks often frequent urban and suburban areas, which likely provide sufficient prey and nest sites, as indicated by higher productivity sometimes found from hawks inhabiting here (Stout et al. 2006). Nests are commonly located in patchy woodlands and riparian corridors adjacent to foraging sites, especially those near agricultural fields (Bent 1937, Fitch et al. 1946, Bednarz and Dinsmore 1982, Palmer 1988, Moorman and Chapman 1996, Tietje et al. 1997). Often, nests are found in the upper quarter of trees with moderate canopy cover and are placed at the crotch of main branches and limbs (Fitch et al. 1946, Bednarz and Dinsmore 1982). A variety of tall trees are used for nesting, including oak, sycamore and eucalyptus (Tyler 1913, Fitch et al. 1946, Palmer 1988, Speiser and Bosakowski 1988). Mader (1978) found red-tailed hawks nesting on a saguaro cactus in Arizona’s Sonoran desert. Red-tailed hawks also nest on cliffs (Bond 1939). Artificial nesting sites, such as transmission towers, billboards and ledges of buildings, are utilized regularly (Stout et al. 1996, Stout et al. 2006). Accessibility to edge habitat may play a role in nest site selection (Bednarz and Dinsmore 1982, Speiser and Bosakowski 1988, Moorman and Chapman 1996, Preston and Beane 2009). During the winter months, red-tailed hawks can be found in much of the same habitat as during the breeding season. Foraging habitats include grasslands, parks, vacant lots, and agricultural areas (Fitch et al. 1946, Palmer 1988, Preston 1990, Leyhe and Ritchison 2004, Preston and Beane 2009). Distribution across a landscape is a function of prey and perch site availability (Preston 1990). Alterations to the landscape (e.g. forest clearing, fire suppression and agricultural development) likely have benefited the species distribution due to the increased availability of open land with abundant prey (LaSorte et al. 2004, Farmer et al. 2009). Migration Red-tailed hawks are considered partially migratory, although typically in California, the species is a year-round resident and remains in or near the breeding territory (Fitch et al. 1946, Gates 1972, Farmer et al. 2009, Preston and Beane 2009). Hawks in the northernmost range (portions of Alaska and Canada) will migrate south, while hawks in the mid-latitudes (45°–50°N) are typically resident year-round (Preston and Beane 2009). Those that do migrate usually only do so at distances of less than 1,500 km, and will rarely cross bodies of water more than 25 km across (Preston and Beane 2009). Red-tailed Hawk Species Account Page 2 of 17 Satellite tracking and band return data shows that young hawks from southern California and northern Baja will migrate longer distances into Nevada, Montana, and Wyoming (Farmer et al. 2009). Red-tailed hawks practice “leap-frog migration”; that is, some northern birds winter farther south then southern birds (Farmer et al. 2009). Abundant prey may alter or delay migratory patterns (Craighead and Craighead 1956). For instance, red-tailed hawks have been known to “short-stop” (overwinter farther north then in previous years) during migration, a behavior adaptation likely due to long-term trends for milder climatic conditions and increased prey availability at bird feeders (Goodrich and Smith 2008). Timing of migration is determined by weather patterns and prey availability (Farmer et al. 2009, Preston and Beane 2009). For northern breeders, spring migration initiates in February to March, with migrating individuals arriving at the breeding sites as late as June (Preston and Beane 2009). For mid-latitude breeders migration is typically shorter, with small north-south movements, altitudinal movements, or little to no migration. The Golden Gate Raptor Observatory (GGRO) in the Marin Headlands, California, is one of the “hotspots” for migrating diurnal raptors in California since it is along one of the major migratory bird pathways along the Pacific Coast. Red-tailed hawks are one of the most observed raptors at GGRO. Sixty-six percent of all sightings in 2009 were red- tailed hawks (n=8297) and turkey vultures (n=8060) (Elliot and Fish 2010). Hawk sightings during the Fall/Winter migration season are illustrated in Figure 1. Figure 1. Red-tailed hawk migration profile at GGRO, 1986-2009 (Elliot and Fish 2010) Food Habits Red-tailed hawks consume a diverse array of prey, including mammals, snakes, small to medium sized birds, reptiles, amphibians, and insects; however, small mammals, reptiles and birds are most common (Gates 1972, Palmer 1988, Steenhof and Kochert 1988, Marti and Kochert 1995, Farmer et al. 2009, Preston and Beane 2009). Diets vary seasonally depending on prey availability and abundance (Peterson 1979, Steenhof and Kochert 1988). In California, Fitch et al. (1946) documented a spring and summer diet consisting of (in order of frequency) ground squirrels, pocket gophers, and rabbits, whereas fall and winter diets consisted of (in order of frequency) pocket gophers, ground squirrels, and rabbits (Fitch et al. 1946). Red-tailed hawks prey on ducks in the Prairie Pothole Region, and scavenge when carrion is available, especially in winter months Red-tailed Hawk Species Account Page 3 of 17 when live resources are less available (Palmer 1988, Sargeant et al.