Grackles are a type of blackbird known for their striking iridescent plumage. They are highly gregarious, often moving, feeding, and roosting in large flocks that can number in the hundreds or thousands, especially outside of the breeding season. This natural tendency means that a single, attractive resource in a suburban yard can quickly draw a concentrated population, driven by their adaptability to human environments.
Identifying the Common Grackle Species
The species most frequently encountered in North American yards are the Common Grackle (Quiscalus quiscula) and the Great-tailed Grackle (Quiscalus mexicanus), found primarily in the southern and western United States. The Common Grackle is medium-sized with a long, dark bill and pale yellow eyes. Its iridescent head often appears glossy purple or bluish-green, contrasting with a bronzy body, and males possess a long, wedge-shaped tail that appears creased in flight.
The Great-tailed Grackle is noticeably larger and more slender. Males exhibit a rich, uniform iridescent black and purple sheen across their entire body and are known for their remarkably long, keel-shaped tail. Both species are long-legged and display a characteristic upright posture as they walk across lawns, confirming their identity through these distinct physical features and conspicuous yellow eye color.
Primary Reasons for Large Gatherings
The main driver behind large grackle concentrations is the reliable availability of food and shelter, which they efficiently exploit through flocking. Suburbia provides predictable, high-calorie food sources that are often easier to access than natural foraging grounds. These sources include spilled seed beneath bird feeders, pet food left outdoors, and poorly secured garbage bins, providing an abundant, easy meal for a large group.
Lawns are also attractive feeding areas, especially when they contain soil invertebrates like grubs and earthworms, which grackles expertly extract. These birds are omnivorous, consuming insects, seeds, fruits, and even small vertebrates, making a diverse yard a prime location for sustenance. Their need for water also concentrates them near bird baths, leaky outdoor faucets, or shallow landscape features.
Grackles also gather in large numbers for security, a phenomenon known as communal roosting, especially during fall and winter migration. These large, often mixed-species flocks seek dense, protective cover for overnight rest, preferring tall evergreen trees or utility lines near a consistent food supply. The sheer number of individuals offers protection against predators, and shared knowledge of nearby feeding locations increases foraging efficiency.
Non-Harmful Ways to Reduce Their Presence
Mitigating the presence of a large grackle flock requires modifying the environment to eliminate primary attractants without causing harm, as all native grackle species are protected under the Migratory Bird Treaty Act. The most effective step is adjusting outdoor food sources. Switch birdseed offerings to safflower or thistle, which are generally unappealing to grackles but still attract smaller songbirds. Feeders should be changed from open trays to weight-activated or tube feeders with short perches, making them difficult for larger birds to access.
Ground food must be eliminated by cleaning up spilled seed daily and ensuring pet food is only offered indoors. Secure waste by requiring garbage cans to have tight-fitting, heavy lids to prevent access. Addressing communal roosting involves thinning out dense tree branches in favored evergreen or deciduous trees to reduce protective cover.
Visual and auditory deterrents can also be employed to make the area seem unsafe. These include hanging reflective tape or using devices that emit predator or grackle distress calls. Limiting accessible standing water, such as emptying bird baths for a short period, further reduces the yard’s appeal. Consistency in applying these non-lethal modifications signals that the environment is no longer a sustainable resource.