As we enter March, spring is slowly unfolding in the Sky Islands. Wildflowers are in their prime, warmer temperatures rule the roost, and the forefront of bird migration is upon us. Among the winged wanderers returning to our local haunts are gray hawks.
I look forward to their spring return perhaps more than any other migrant. For me they embody the transition from cold to warm, from winter to spring, and from austere to fecund. Though our Raven’s Nest Nature Sanctuary hosts many raptors, including golden eagles, osprey, and zone-tailed hawks, it is gray hawks that capture my imagination the most.
Gray hawks range from southeast Arizona, southern New Mexico, and southern Texas through both coasts of Mexico deep into Central America, terminating in northern Costa Rica. Thus, they are best described as a neotropical buteo or soaring hawk.
Those that breed in the Sky Islands almost all depart for warmer Mexican climes. Occasionally a lingering breeder spends the winter in our state, where they sometimes show up on the Patagonia Christmas Bird Count. I lose part of myself when they migrate south again in October, awaiting their return once more in March.
In terms of size, gray hawks are smaller than the more familiar red-tailed hawk and appear to be about the same size as the similar-looking and ubiquitous Cooper’s hawk, though they weigh considerably less. Their nickname south of the border is “Mexican goshawk.” They weigh about 18 ounces on average and have short wings, that help them outmaneuver prey in tight spaces.
The sexes look alike in their steel-gray, barred plumage. Other features that stand out are their bright yellow feet, the yellow base of their hooked beak, and their black and white striped tail. These traits make misidentification unlikely.
The gray hawk has a characteristic call, which I describe as a lilting, haunting whistle. It is often repeated in a series, which helps to pinpoint their whereabouts. This is not always an easy task since gray hawks not only have to be stealthy in order to detect and dispatch their keen-eyed prey – many lizards readily recognize the flying silhouette of a raptor – but also to avoid being predated themselves. To this end they will mob larger raptors that pose a threat to them.
In turn I’ve witnessed smaller American kestrels returning the favor with their own aerial assault. Either way, the smaller bird, the mobber, sends a message of vigilance to its potential slayer. The one species that may pose the largest threat to gray hawks is a silent and unseen predator – great horned owls. A perched, sleeping hawk is no match for this deadly ghost.
Within our region, gray hawks are usually very habitat-specific. They prefer to nest and hunt in well-defined riparian zones, often where there is water, tall trees such as Fremont cottonwood, and an abundance of their preferred prey — lizards. In fact the U.S. range of this species encompasses those regions with the greatest lizard diversity. I have seen Clark’s spiny lizards in their deadly clutch, as well as several sizable snakes. Gray hawks prey upon most any small mammal, bird, or amphibian that is unwary enough to be caught, either from a perch or from flight. I once saw one with a rather large desert cottontail near Sonoita Creek.
At Raven’s Nest, our yearly pair of gray hawks nest in a large mesquite tree within a dense mesquite woodland. While this habitat paradigm is rare north of the border, the species employs this plasticity throughout the more southern parts of its range, where it even prefers drier, secondary forests.
Courting gray hawks capture my attention, as the male performs aerial undulations and vocal histrionics aimed at winning the female. He will also lay the foundation of a stick nest, indicating his fitness to be a parent in doing so.
Once secured, the bond is monogamous. The average clutch size is two to three pale blue eggs, which take slightly over a month for the female to incubate. During this time, the male delivers various prey items for her consumption, hence the need to prove his mettle during courtship.
The hatched chicks take about six weeks to fledge, with both parents furnishing food for them. The immatures are heavily barred below and brown overall, lending them a degree of camouflage beyond even the adults.
Gray hawks seem to be slowly expanding their range in the U.S., where they have increased their numbers from about 80 nesting pairs to around 200 within the last few decades. Still, they are vulnerable to a variety of threats. Foremost is habitat degradation and destruction. Livestock overgrazing lowers prey abundance and cover. Land clearing for housing and industry often levels riparian zones and mesquite woodlands. Climate change proffers more fire, altering their habitat. Any chemical used on the land may bioaccumulate in their flesh, as gray hawks are top predators. All the more reason to savor this tropical terror as it plies the skies amidst our forested islands.
Vincent Pinto and his wife, Claudia, run RAVENS-WAY WILD JOURNEYS LLC, their Nature Adventure & Conservation organization devoted to protecting and promoting the unique biodiversity of the Sky Islands region. RWWJ offers a wide variety of private, custom-made courses, birding & biodiversity tours. Visit: www.ravensnatureschool.org