Diet, cast composition, and energy and nutrient intake of red-tailed hawks (Buteo jamaicensis), great horned owls (Bubo virginianus), and turkey vultures (Cathartes aura)

Four adult red-tailed hawks (Buteo jamaicensis), four adult great horned owls (Bubo virginianus), and four adult turkey vultures (Cathartes aura) were fed I-day-old chicks (Gallus gallus) or 3-wk-old Syrian golden hamsters (Mesocricetus auratus) to satiety in metabolism cages to determine whether these prey species would meet energy and nutrient needs in captivity. Chicks contained 24% dry matter and (on a dry basis) 67% crude protein, 21% ether extract, 5% ash, 2.1% calcium, and 1.5% phosphorus. Hamsters contained 30% dry matter and (on a dry basis) 50% crude protein, 35% ether extract, 8% ash, 2.5% calcium, and 2.0% phosphorus. Magnesium, sodium, potassium, iron, copper, manganese, zinc, and selenium concentrations were also determined. Daily dry matter intakes were equivalent to 1.7-3.2% of raptor body weight. Cast dry matter regurgitated and egested comprised 2-8% of dry matter consumed. Casts egested by owls were higher in ash, calcium, phosphorus, and magnesium than casts egested by hawks or vultures, apparently because of the predominance of bone in owl casts. Daily metabolizable energy intakes were 96-184 kcal/BWkg0.73. The energy and nutrient needs of these raptors should be met without further supplementation by feeding 1-day-old chicks or 3-wk-old hamsters to satiety.