Great-tailed Grackle (Quiscalus mexicanus)
These familiar birds sing one song: ¿Quien es mas macho?
By Noreen Damude
A bird with an attitude, a taste for close-packed urban living and a touch of clash and class, the great-tailed grackle is the black bird most folks love to hate. After a day of foraging in surrounding fields, hordes of great-tails sweep darkly into town near sunset to roost overnight in noisy arboreal ghettos, stacking themselves tightly from tree top to lowest branches. The strident yelps, shrieks, cackles and cracks, as alpha males joust for optimal perch sites, seem to go on interminably before birds finally settle in for the night. In some well-lit parking lots, complete silence never obtains.
Yet for those nature watchers who can resist the initial recoil from foul-smelling white-washed sidewalks, chalk-bespattered car windshields and cacophonous vocalizations, the great-tailed grackle offers a highly visible, easily accessible display of avian behavior at its most fascinating. Start watching them a while, and soon their intricate life history unfolds, with its idiosyncratic social structure, inimitable vocal repertoire, macho territorial displays, oblique courtship rituals and seraglio-based family ties. Highly adaptable, behaviorally flexible, bold to the point of brazenness, great-tails acclimate easily to life in the big city and intrigue us with their quirky lives.
Sometimes dubbed the “jackdaw— or “crow-blackbird,— the male great-tailed grackle is a large, glossy-black bird with purplish sheen, pale lemon eyes and a distinctively flat-headed silhouette culminating in a sharply pointed bill. Eighteen inches from stem to stern, the male grackle sports an enormous keel-shaped tail that it holds in a distinctive V-shaped configuration during flight. Similar to the closely related boat-tailed grackle, found only along the coast in marshes, great-tails can be difficult to identify where the two species overlap. Females apparently have no problem recognizing the appropriate mate, as there is no evidence of hybridization between the two species.
As habitat generalists, great-tails typically occur in open to semi-open landscapes, mostly in the lowlands, including farmland, irrigated fields brushy areas, and marshes. Shunning deserts, mountains and the heavily forested portions of the state, they overwhelmingly seek out comfortable urbanized situations such as tree-lined streets, parks, gardens, manicured lawns and golf courses. They prefer to nest in grassy areas with scattered trees and shrubs — often near water — that afford them the insect and plant matter they need. Their diet consists of terrestrial arthropods, aquatic invertebrates, small vertebrates, bird eggs and fruit along with grain and grass seeds. Interestingly, males eat mostly grains and plant matter, while females focus on animal protein, especially insects, during the nesting season.
Perhaps the most intriguing aspect of great-tailed grackle biology is their mating system. Alvaro Jaramillo and Peter Burke note in New World Blackbirds that breeding is invariably polygynous, with males mating with several females apiece. Come early spring, males set up small territories to prepare for the arrival of females a few weeks later. Males stage elaborate nuptial displays, strutting about with drooping wings and tails fully spread. The tempo picks up as they vibrate their wings, producing strange rattling, crashing sounds. They then belt out an unmusical assortment of piercing whistles, squeals and shrieks sounding like poorly maintained machinery set at full throttle and in desperate need of lubrication. The cacophonous “love-threat— duet is performed by males only and is typically accompanied by the “ruff-out— display.
As the competition intensifies, the male-bird equivalents of arm-wrestling ensue — taking the form of competitive neck-craning and star-gazing postures, wing drooping and quivering, culminating in an ecstatic “wing-hover— dance. Unmatched for their vitality, if not obsessiveness, the males tend to focus more on intimidating and impressing rival males than on seducing the smaller, seemingly indifferent females.
Masters of machismo, male great-tails go eyeball-to-eyeball, bill-to-bill, against all rivals. They will even try to fend off the “threat— of their own reflection in a nearby car rearview mirror. Dozens of males repeat this frenetic courtship routine hundreds of times in a morning without a single female in sight. If present, a female may respond by giving the solicitation display, drooping and quivering her wings then cocking her tail over her back as she gives her “Take me, I’m yours,— solicitation call.
So why do grackles emphasize male-to-male confrontations? As is often the case in a resource-based system, the answer lies in the female side of the equation. Nature has granted the female great-tail grackle both the ability and resources to care for her young with little or no help from the male. In fact, males rarely if ever help build the nest, incubate eggs, or brood young. A male’s time and energy is almost wholly invested in guarding his harem from surreptitious intrusions from rogue males or predators.
And once nesting activities get underway, the harem master switches focus to chasing his neighbor’s females, thus maximizing his fitness by mating with as many of them as possible. But, once mating opportunities are exhausted, these roving Lotharios move on. Nevertheless, males that hold larger territories and spend a greater portion of their time defending the nesting colony appear to sire a greater number of offspring than less vigilant ones.
Females, for their part, squabble constantly among themselves over nest sites and building materials within the nesting colony, filching tidbits from their neighbors whenever possible. Not to be outdone by the male, an individual female is not above cheating on the harem master should his vigilance flag for an instant. As is often typical of this type of mating system, first-year males do not breed, but young females do, perhaps because the sex ratio is highly skewed towards females.
Great-tailed grackles are abundant residents in the southern portion of the state and continue to expand their range throughout the country. Their aggressive expansion has been fanned by two factors: the irrigation of dry areas and the planting of trees in formerly treeless grasslands and deserts. According to George Simmons’ Birds of the Austin Region, great-tails were considered rare and local summer residents in 1921 from early March to July, reaching their northern limit in Central Texas. Today, great-tails have pushed their home range as far north as southern Canada.