Gray Hawk Guide (Buteo plagiatus)

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Carrie Sanderson

Carrie is an artist, writer, and birdwatcher. You can often find her staring out the window with binoculars to hand, watching the crows chase away a buzzard, or at the beach sketching the gulls and waders. She has been passionate about birds for over a decade, and her love for them grows daily. Birds uplift and give her joy. She doesn’t know what she’d do without them!

Latest posts by Carrie Sanderson (see all)

• Gray Hawk Guide (Buteo plagiatus) - October 25, 2022
• Swainson’s Hawk Guide (Buteo swainsoni) - October 19, 2022
• Harris’s Hawk Guide (Parabuteo unicinctus) - September 26, 2022

Formerly known as the Mexican Goshawk, Gray Hawks are unique in their coloring compared to other North American buteos. Their dark brown eyes contrasting with their light grey colors certainly draw me to this enchanting diurnal hawk.

Taxonomists have had a field day trying to place the Gray Hawk in the correct genus. The way they fly and their long tail makes a Gray Hawk look more like an accipiter (think Northern Goshawk Accipiter gentilis), but their broad wings and osteology show more affinity with a buteo. They were given their own genus at one point, Asturina. But then the species was split into Buteo plagiatus (Gray Hawk) and Buteo nitidus (Gray-Lined Hawk). Within Buteo nitidus, there are three subspecies: Buteo nitidus blakei, Buteo nitidus nitidus, and Buteo nitidus pallidus. There are no subspecies of Buteo plagiatus.

While discussions on their genus continue, I will carry on with what I know about Gray Hawks! By the way, the hawks are known as Grey Hawks and Grey-Lined Hawks for my fellow British-speaking birding friends.

Taxonomy At A Glance

• Domain: Eukaryota
• Kingdom: Animalia
• Phylum: Chordata
• Class: Aves
• Order: Accipitriformes
• Family: Accipitridae
• Genus: Buteo
• Species: Buteo plagiatus

How to Identify A Gray Hawk

Gray Hawks have gray and white stripes on their bellies and breasts, which reminds me of one of my childhood favorite book characters, Burglar Bill, and his striped top. The upper parts and crown are medium gray, with whitish underwings and a bit of gray barring. Their black tail is longer than those of other buteos and has bands of narrow gray-brown and white widening towards the base of the tail.

Gray Hawks have dark brown eyes, a black hooked bill and bright yellow cere (the fleshy part at the base of the bill), black talons, and bright yellow tarsi. Wing length appears to gradually increase from south to north across the population range – meaning the wingspan of the Gray Hawks in the U.S. may be slightly bigger than the Gray Hawks in South America.

Females are a bit darker and larger in mass than males, which is often the case with birds of prey. An adult male is 391 – 470 g in mass, and a female adult is 552 – 699 g. Their lengths are 37 – 46 cm; typically, a male is about 41 cm, and a female is 44 cm. Otherwise, males and females are similar in coloring. As I mentioned before, the adult plumage is unique amongst all North American raptors.

A juvenile’s bill, cere, tarsi, and talons are similar to that of adults. Other than that, they look different. They have a dark stripe through the eye and dark stripes on either side of the throat. Lightly colored sides of the head, and eyes are lighter brown than the adults.

The juveniles’ upper parts are dark brown, almost black, and lightly spotted in a yellow-brown color. The underparts are also yellow-brown, streaked with dark brown, almost black, across the breast, continuing onto the belly where it looks more like spots. Their tail is longer than the adults’ and is gray-brown with dark bands of color that get wider down to the tip of the tail. Their underwings are yellow-brown with some dark barring on the flight feathers. Juveniles can be confused with Broad-Winged and Red-Shouldered Hawks.

The Gray-Lined Hawks (Buteo nitidus) are the same in length (38 – 46 cm), but the males and females have a smaller mass. Males are 350 – 497 g, and females are 320 – 592 g (females again tend to be larger than males). Compared to the Gray Hawk, they are a lighter gray and have a barred gray crown, nape, back, and wings.

Where Do Gray Hawks Live: Habitat

Gray Hawks are neotropical birds of prey. From a minority of breeding pairs in the south of Arizona and Texas, their range extends across northern Mexico through Central America to parts of South America. It includes the Caribbean coast, east Columbia (east of the Andes) to east Bolivia, northern Argentina, Paraguay, and southeast Brazil, as well as north and east of Suriname and Trinidad and Tobago. Also, west of the Andes in the lowlands of western Ecuador.

They like to be near rivers and streams, particularly during the breeding season. An abundance of mesquite and cottonwood is vital for them to thrive, forage and raise their young.

In the tropical climes, their habitat varies from savanna and open thorn scrub to tropical forests. It is thought that rivers and streams are not as crucial in these areas as in the U.S. There is less known about the population outside of the U.S., though.

Gray Hawk Diet and Feeding

Lizards, lizards, and more lizards! Whiptail lizards are a particular favorite in Arizona. In some areas, the Gray Hawks love the taste of spiny lizards.

Gray Hawks forage in mesquite woodlands close to cottonwood and willow trees, the preferred sites for nesting in the northern part of their territories. Not much is known about the population further south, but in Suriname, for example, Gray Hawks were seen to forage in open forests and along the edges of them. They were also seen hunting for birds and mammals, in addition to lizards.

Gray Hawk Breeding

Most of what is known about the Gray Hawks is based on their habitat in Arizona. The small population that breed there is migratory, and they return to breed around mid-March to early April. The females lay eggs early to late May, and the young leave the nest in July or early August, or even late August if the first clutch fails and a female has a second brood.

In other areas, little is known about the Gray Hawk population. However, in Suriname in South America, eggs are laid in February, and nestlings appear in March to early May.

Gray Hawk Nesting And Eggs

Nest-building starts while a male and female are courting, which can last till mid-May. The nest is high in the canopy of cottonwood or willow trees, though it is still covered despite the height. It comprises of sticks and fresh twigs, and leaves are used for lining. The hawks keep adding twigs and sticks to the nest’s rim until the eggs have hatched.

A female Gray Hawk lays one clutch of 2 to 3 eggs per breeding season, though if the first clutch is unsuccessful, she may lay a second one. She is the one who does the incubating, and the male fetches food for her while she spends about 32 to 34 days doing so. The male may cover the eggs if the female leaves the nest to feed somewhere else; otherwise, he is on food delivery duty.

The young leave the nest around 42 days old, though a few days before that, they can be seen moving around on branches surrounding the nest. They stay near the nest after fledging but for how long and how long they rely on their parents for food is unknown. Adults will chase away the juveniles who come too close to the adults’ breeding sites.

Gray Hawk Population

According to Birds of the World, recent research shows the small population in Arizona and Texas is stable and possibly increasing. As long as their habitat remains intact, numbers could increase even more. It is thought there are less than 100 breeding pairs in the U.S.

After some digging, I discovered on BirdLife International that the overall population size of Gray Hawks (Buteo plagiatus) was estimated at 2 million adults in 2016. Data on the population of the Gray-Lined Hawks is limited: it is estimated between half a million to almost 5 million adults, which is quite a broad scope. Both species have an extensive range.

Are Gray Hawks Endangered?

Conservation status is rated Least Concern. However, the U.S. Fish and Wildlife Service have labeled Gray Hawks a Species of Concern (they call them Asturina nitida, not Buteo plagiatus); in Arizona, they are a Species of Special Concern; and in Texas, they are Threatened.

Habitat loss poses an ongoing threat, as with many of our treasured birds. Due to human activity and urbanization, rivers and streams that dry up, resulting in the disappearance of mesquite and cottonwood, as well as cutting them down, will have an impact on the breeding pairs in Arizona and Texas. Deforestation in the neotropics would cause habitat loss, drive the hawks away, or cause them to die out.

Gray Hawk Habits

Gray Hawks are skillful hunters. They adopt the “perch and wait” approach. Their heads and necks are supple, and they can turn their heads almost 180 degrees. Once prey is spotted, they speed down from their perch, snatch an unsuspecting lizard off the ground or from a tree trunk or branch using their talons, and continue to fly.

Compared to most other buteos, they soar much lower over the ground. Their flight looks more like that of an accipiter than a buteo: a few quick wing-beats followed by gliding. They keep their wings level and fan their tails when soaring. Soaring in the early afternoon is more common during the breeding season. They are likely staking out their territory.

Gray Hawks have distinctive calls: the Peacock call mainly during the breeding season, and the Creee! call that can be heard all year round. As the first name suggests, the call sounds like the cry of a peacock. One whistled note that has three parts to it. While there is a typical sound to it, it can also sound rolled, slurred, and amplified. It’s thought the female slurs and amplifies the call.

The Creee! call is one note and used as an alarm call. People often hear this call when they have entered an area where the Gray Hawks nest, and usually, the female makes this sound.

Gray Hawk Predators

The Great Horned Owl (Bubo virginianus) is the Gray Hawk’s biggest predator and possibly the Red-Tailed Hawk (Buteo jamaicensis) too. More study is needed to be certain. The Great Horned Owl will take the Gray Hawk’s nestlings one by one, and incubating females have been killed by them, too. A female is less aggressive towards the owl and sometimes chases off the owl, unlike the male, who will repeatedly dive at the Great Horned Owl, occasionally making contact. A male will also be vocal towards and chase off Cooper’s Hawks (Accipiter cooperii), Red-Tailed Hawks (Buteo jamaicensis), Zone-Tailed Hawks (Buteo albonotatus), and Common Ravens (Corvus corax).

Another possible threat to the Gray Hawks is shooting and trapping in parts of their range outside of the U.S. For instance, 11 out of 13 banded Gray Hawks were found shot in Mexico. It is not believed to happen in the Gray Hawks’ U.S. breeding grounds.

Gray Hawk Lifespan

The lifespan of a Gray Hawk is six years, according to the BirdLife International Gray Hawk Species Factsheet. In addition, two Gray Hawk males that were banded as nestlings were recovered five years later. The survivorship and lifespan of Gray Hawks (Buteo plagiatus) need further research, as well as studies on their breeding and wintering habitat outside the U.S.

I rather like some of the mystery surrounding this hawk. It adds excitement when you spot a Gray Hawk in its natural habitat, much like when you see a rare bird while on a walk in your local park or woods. And the fact it has been hard to fit the Gray Hawk into an existing genus (and for everyone involved to be happy about it) makes for a unique hawk – if it were my decision, I’d put the Gray Hawk back into Asturina.

It feels like Gray Hawks deserve to have their own genus, given their distinctiveness.

FAQ

Research Citations

• Bibles, B. D., R. L. Glinski, and R. R. Johnson (2020). Gray Hawk (Buteo plagiatus), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA.
• https://www.audubon.org/field-guide/bird/gray-hawk#
• https://www.allaboutbirds.org/guide/Gray_Hawk/#
• https://www.allaboutbirds.org/guide/Gray_Hawk/id
• https://ebird.org/species/gryhaw2
• BirdLife International (2022) Species factsheet: Buteo plagiatus. Downloaded from http://www.birdlife.org on 18/10/2022.
• BirdLife International (2022) Species factsheet: Buteo nitidus. Downloaded from http://www.birdlife.org on 18/10/2022

Looking for more interesting readings? Check out:

• Broad-Winged Hawk Guide (Buteo platypterus)
• Red-Shouldered Hawk Guide (Buteo lineatus)
• Common Black Hawk Guide (Buteogallus anthracinus)
• Swainson’s Hawk Guide (Buteo swainsoni)