Accipitriformes

For a long time, the majority view was to include them with the falcons in the Falconiformes, but many authorities now recognize a separate order Accipitriformes. A DNA study published in 2008 indicated that falcons are not closely related to the Accipitriformes, being instead more closely related to parrots and passerines. Since then, the split and the placement of the falcons next to the parrots in taxonomic order has been adopted by the American Ornithological Society's South American Classification Committee (SACC), its North American Classification Committee (NACC), and the International Ornithological Congress (IOC). The British Ornithologists' Union already recognized the Accipitriformes, and has adopted the move of Falconiformes. The DNA-based proposal and the NACC and IOC classifications include the New World vultures in the Accipitriformes, while the SACC classifies the New World vultures as a separate order, the Cathartiformes. However, a 2021 analysis of mitochondrial genes suggested a stronger phylogenetic relationship between Cathartiformes and Accipitriformes, and they are now normally included within the Accipitriformes as the family Cathartidae. When Cathartiformes is considered a separate order, sister to Accipitriformes, Accipitriformes sensu lato is called Accipitrimorphae.

Characteristics

The Accipitriformes are known from the Middle Eocene and typically have a sharply hooked beak with a soft cere housing the nostrils. Their wings are long and fairly broad, suitable for soaring flight, with the outer four to six primary feathers emarginated.

They have strong legs and feet with raptorial claws and opposable hind claws. 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. Monogamy is the general rule, although an alternative mate is often selected if one dies.