Hawks are medium to large birds of prey that belong to the family Accipitridae. There are over 240 species of hawks found worldwide, with some key characteristics that define their physical appearance. Hawks have broad wings and long, rounded tails to provide excellent aerial maneuverability when hunting prey. They have strong, curved talons and hooked upper beaks called tomial teeth used for tearing meat. Their vision is among the sharpest in the animal kingdom, allowing them to spot potential prey from afar. While their plumage varies by species, common colors include brown, black, white, and grey.
Size and Wingspan
Hawks range dramatically in size. The smallest hawk species is the African pygmy falcon, with males weighing just 55-85 grams and a wingspan of 20-23 cm. Larger hawk species can have impressive wingspans exceeding 1.5 m. For example, the ferruginous hawk has a wingspan of up to 1.8 m. In terms of length, hawk species range from 20 cm to over 60 cm from head to tail. The smallest hawks may be comparable in size to a mourning dove, while large hawks like the red-tailed hawk outweigh backyard songbirds by over 1,000 times.
Key physical traits like wingspan and wing shape also vary by species and hunting strategy. Long-winged hawks like the northern harrier are adapted for open country hunting and aerially stalking prey. In contrast, accipiters like the sharp-shinned hawk have short, rounded wings ideal for maneuvering through dense foliage when chasing songbirds.
Legs, Feet, and Talons
A hawk’s legs and feet are uniquely adapted for hunting and killing prey. Their legs are relatively long and slender. Larger species may have feathering extending partway down the legs, unlike smaller falcons. The feet have four toes, three facing forward and one facing back. This anisodactyl toe arrangement provides strength and balance for grasping prey items.
Each toe is tipped with a curved, pointed talon used for catching and clasping prey. These talons are exceptionally strong and can exert over 450 psi of pressure. For comparison, the human hand exerts around 60 psi. The talons are used to swiftly kill prey immediately upon capture. Hawks also use their talons defensively against potential predators or threats. They will often rake their talons across an antagonist while flying by.
Beak and Facial Features
Like other birds of prey, hawks have large, hooked beaks used for tearing meat and feeding. The upper mandible is notched and features tomial teeth pointing backward. These help hawks neatly slice and shred the flesh of prey items. Hawks have rounded nostrils located centrally on the cere at the base of the upper beak. This provides a good sense of smell to aid in finding prey.
Many accipiters like the Cooper’s hawk have distinctive bold striping patterns on their napes. This helps them blend into dappled sunlight when concealed in trees. Hawks tend to have relatively flat faces, unlike the prominently curved beak of eagles and falcons. Their eyes are forward-facing, providing three-dimensional vision and visual acuity up to 8 times greater than humans. Streamlined contours around the eyes may help hawks spot prey motion.
Plumage and Coloration
Hawks display an incredibly diverse array of plumage colors and patterns depending on species. Some key trends in hawk plumage include:
– **Browns**: Medium to dark brown upperparts are common, providing camouflage against trees and dirt when hunting perched or on the ground. Light brown undersides blend against sky and clouds in flight.
– **Grays**: Light morph red-tailed hawks and other buteos have mottled gray and white undersides. Northern harriers are gray with an owl-like facial disk.
– **Reds**: Red-tailed and red-shouldered hawks get their names from distinctive rufous tail and shoulder patterns. The red-tailed hawk’s bellyband is also reddish.
– **Whites**: Light morph ferruginous hawks and rough-legged hawks are mostly white below with black wingtips. Harris’s hawks have white tail tips.
– **Blacks**: Black plumage may be featured on the wings, back, helmets, or tails of species like zone-tailed hawks and common black hawks. Melanistic red-tailed hawks are entirely black.
– **Bars**: Bold black and white bars on the tail and flight feathers provide camouflage in forests for barred owls and hawk-owls.
– **Creams**: Some hawks like the sharp-shinned have light colored underparts with fine dark barring. Adult broad-winged hawks are mostly cream.
– **Tans**: The ufous hawk earns its name from its overall rufous tan coloration.
Sexual Dimorphism
Many hawk species exhibit sexual dimorphism, where males and females differ consistently in size and plumage characteristics. In most species, females are distinctly larger than males. For example, female northern goshawks may weigh over 50% more than their mates. Plumage also often varies between the sexes, with females sometimes having more bold patterning. However, juveniles often resemble adult females until they complete their first molt. Red-tailed hawks are strongly dimorphic, with brown-toned females and more melanistic males.
Molting and Plumages
Like all birds, hawks molt and replace all feathers periodically. Hawks generally molt and replace feathers gradually over multiple seasons. Their plumage can be divided into basic categories:
– **Juvenile** – 1st year plumage with distinct patterns from adults
– **Immature** – 2nd and 3rd year progressing toward adult appearance
– **Subadult** – Near adult appearance but still some juvenile traits
– **Adult** – Definitive species-specific non-breeding plumage
– **Alternate adult** – Bright breeding plumage in some species
Young hawks often have white or buffy tips on their feathers creating a scalloped pattern. Their tails may be banded. As they mature, these patterns gradually fade to be replaced by adult plumage after 2-3 years in most species.
Vocalizations
Hawks are highly vocal birds, using calls for communicating territorial boundaries, courtship, alarms, and begging in young. Calls are often categorized as:
– **Whistles** – Made by disturbing air flow through vibrating tail feathers during display dives.
– **Chirps/Chatter** – Short, repetitive chips or chek notes used in courtship or to signal alarm.
– **Screams & Screeches** – Alarm and panic calls often made when mobbing potential threats.
– **Trills** – Rapid pulsed notes like cackling, whinnying, or keening.
Calls are unique to each species. The red-tailed hawk’s signature cry is a loud, hoarse, descending whine that drops an octave at the end. Red-shouldered hawks give a thin, wailing kee-aah cry. Accipiters like Cooper’s hawks give a loud kak-kak-kak series of alarm notes.
Variation and Identification
With over 240 species worldwide, hawks show incredible variation related to habitat and prey. Identifying hawks is challenging even for experts, but focusing on key features can help:
– **Size** – Span ranges from 20 cm to 1.5 m. North American buteos are generally bulky and broad-winged.
– **Wing shape** – Long, narrow, pointed wings indicate open country harriers. Short, rounded wings identify forest accipiters. Broad, fingered wings on buteos.
– **Legs** – Long yellow legs indicate large buteos. Feathering partway down legs is typical of accipiters.
– **Tail** – Square or notched tails on accipiters and harriers, rounded fans on buteos. Check patterns and color.
– **Head** – Bold striping on nape of accipiters. Dark facial disks on harriers. Watch for crests.
– **Plumage** – Note underpart and tail color variations. Compare extent of dark markings.
– **Behavior** – Soaring over open areas indicates buteos, while accipiters stay in cover.
Conclusion
Hawks occupy diverse habitats worldwide thanks to adaptations like broad wings for soaring over prairies or cliffs and short rounded wings for forest chasing. Their sharp talons, hooked beaks, acute vision, cryptic plumage, and varied vocalizations equip each species for hunting success. Identification involves noting size, wings, legs, tail shape, head pattern, plumage colors, and hunting behavior. With so much variation, the hawk family provides an excellent showcase of evolution through isolation and adaptation. Their shared traits like raptorial feet, sharp vision, and powerful flight make this partnership of predators one of nature’s most successful designs.