Portrait of a Red Tail Hawk – San Joaquin Valley California, USA

510 Views – 05/23/2011

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The Accipitriformes is an order that has been proposed to include most of the diurnal birds of prey: hawks, eagles, vultures, and many others, about 225 species in all. For a long time, the majority view has been to include them with the falcons in the Falconiformes, but some authorities have recognized a separate Accipitriformes. A recent DNA study has indicated that falcons are not closely related to the Accipitriformes, being instead related to parrots and passerines. Since then the split (but not the placement of the falcons next to the parrots or passerines) has been adopted by the American Ornithologists’ Union’s South American Classification Committee (SACC), its North American Classification Committee (NACC), and the International Ornithological Congress (IOC).

The DNA-based proposal and the NACC and IOC classifications include the New World vultures in the Accipitriformes, an approach followed in this article. The SACC classifies the New World vultures as a separate order. The placement of the New World vultures has been unclear since the early 1990s.

Characteristics: Accipitriformes are known from the Middle Eocene (the possibly basal genus Masillaraptor from the Messel Pit) and typically have a sharply hooked beak with a cere (soft mass) on the proximodorsal surface, housing the nostrils. Their wings are long and fairly broad, suitable for soaring flight, with the outer 4–6 primaries emarginated.

Accipitriformes have strong legs and feet with raptorial claws and an opposable hind claw. Almost all Accipitriformes are carnivorous, hunting by sight during the day or at twilight. They are exceptionally long-lived, and most have low reproductive rates.

The young have a long, very fast-growing fledgling stage, followed by 3–8 weeks of nest care after first flight, and 1 to 3 years as sexually immature adults. The sexes have conspicuously different sizes and sometimes a female is more than twice as heavy as her mate. This sexual dimorphism is sometimes most extreme in specialized bird-eaters, such as the Accipiter hawks, and borders on non-existent among the vultures. Monogamy is the general rule, although an alternative mate is often selected if one dies.

The Accipitriformes are among the most diverse orders in size, from the small sparrowhawks to the biggest Old World vultures, and the somewhat bigger Andean Condor (one of the largest flying birds extant) if the Cathartidae are included.