What Is a Flock of Grackles Called?

A flock of grackles is most commonly called a “plague.” You will also see the terms “annoyance” and “chattering” used, though “plague” is by far the most recognized collective noun for these iridescent blackbirds. These names belong to a centuries-old English tradition of assigning colorful group labels to animals, and in the case of grackles, the terminology reflects genuine public sentiment. Anyone who has watched thousands of glossy black birds descend on a parking lot at dusk can understand why “plague” stuck.

Where These Collective Names Come From

Fanciful collective nouns for animals trace back to medieval England, where hunting manuals cataloged “terms of venery” for everything from a “murder” of crows to an “exaltation” of larks. Most of these labels were invented for sport or wit, not science. Grackles, being a New World species, were never part of that original medieval list, but the tradition of coining evocative group names carried forward. At some point, popular usage settled on “plague” for grackles, likely because their enormous winter roosts and boisterous calls made them one of the more conspicuous and polarizing birds in North American suburbs and farmland.

It is worth noting that none of these collective nouns carry any official scientific standing. Ornithologists simply say “flock” or “roost” depending on whether the birds are in flight, feeding, or gathered for the night. If you want to sound literary, “plague” is the word. If you want to be precise, “flock” works for any group of grackles on the move, and “roost” works for the massive overnight gatherings that give these birds their reputation.

How Big Grackle Flocks Actually Get

The word “plague” starts to feel less like hyperbole when you see the numbers. A five-year study of roosting flocks in central New Jersey tracked common grackles and European starlings sharing roost sites that ranged from about 2,000 birds to over 100,000 individuals. Roosts were active anywhere from three to twenty weeks, with total roosting populations peaking around mid-August when the greatest number of roost sites were in use simultaneously. By late fall, fewer roosts remained active, but the surviving ones were enormous, sometimes exceeding 30,000 birds each.¹

These are not just theoretical counts. In cities across the southern United States, winter roosts of grackles regularly blanket shopping center trees, highway overpasses, and power line corridors. Houston, Austin, and other Texas cities deal with grackle roosts every winter that number in the tens of thousands and generate constant complaints about noise and droppings. The birds seem to prefer the warmth of urban heat islands and the artificial lighting of commercial areas, which may help them spot predators at night.

Radio-tagging data from the New Jersey study revealed something interesting about how these massive congregations form and dissolve. The researchers found that changes in the total roosting population were driven largely by birds shifting between small, scattered roosts that fell below detection thresholds and the larger “major” roosts being counted. In other words, the grackles were always out there; they just cycled between being visible in huge groups and being dispersed in smaller, harder-to-notice clusters.¹

Why Grackles Gather in Such Large Numbers

The sheer scale of grackle flocks raises an obvious question: what do the birds get out of crowding together? The two leading explanations are predator protection and information sharing, and the evidence suggests both play a role.

A study of great-tailed grackles feeding on open grass meadows in Panama tested whether flock density changed how individual birds behaved. When grackles fed in denser groups, their search paths became straighter and more efficient, and females scanned their surroundings for danger less frequently. The interpretation is straightforward: with more eyes watching, each bird could afford to spend more time feeding and less time looking up.² Feeding rates themselves did not change with flock size, suggesting the benefit was not about finding more food per se but about being able to forage with less anxiety.

The information-sharing hypothesis goes a step further. A landmark paper on communal roosting in birds argued that roosts and breeding colonies evolved primarily as “information centres” for finding unevenly distributed food. Birds returning to a roost with empty stomachs could follow well-fed birds the next morning to productive foraging sites. Predation pressure, meanwhile, was considered the main force shaping the physical structure of these gatherings: how tightly the birds clump, where they position themselves, and how they respond to threats.³

For grackles specifically, both mechanisms are plausible. They eat a wide variety of foods, from insects and grain to french fries and pet food left on porches, and the availability of these food sources shifts unpredictably. A roost full of thousands of birds essentially becomes a nightly poll of who found food where, and the hungrier birds benefit by tagging along with the successful ones the following day.

Social Hierarchies Within the Flock

A grackle flock is not a formless swarm. Within it, individual birds maintain distinct social ranks, and those ranks have real consequences. Boat-tailed grackles provide one of the clearest examples. Males and females spend most of the year in separate groups. During the nesting season, females gather in large, dense colonies on small marsh islands or in isolated trees. Many males show up at each colony, but only a few high-ranking individuals actually mate. The dominant male at a colony can hold his position for years; alpha males may be ten years old or older.⁴

This kind of dominance hierarchy means that for many male grackles, being part of the flock does not guarantee reproductive success. Lower-ranked males hang around the edges, waiting for an opportunity or hoping to move up the ladder when a dominant bird ages out or disappears. The system creates intense competition, which helps explain the dramatic size difference between male and female grackles. Males are substantially larger and flashier because they are competing for a limited number of mating slots within a colony where many females nest close together.

Common grackles have a somewhat less rigid system, but they still establish pecking orders at feeding sites and roosts. Watch a group of grackles at a bird feeder and you will quickly notice that certain individuals eat first while others wait at a respectful distance. These interactions are brief and usually settled with a quick display rather than actual fighting, but they are constant.

Crop Damage and the “Plague” Reputation

Grackles belong to the blackbird family Icteridae, and along with red-winged blackbirds and brown-headed cowbirds, they are among the most economically damaging birds in North American agriculture. The collective noun “plague” resonates with farmers who have watched flocks descend on ripening fields.

A comparison of blackbird damage to corn and sunflower crops in North Dakota found that sunflower took the harder hit, with damage roughly fourteen times greater in sunflower fields than in corn. Annual production losses from blackbird damage averaged about $1.3 million for corn and $3.5 million for sunflower in that state alone.⁵ Sunflower is particularly vulnerable because the seeds are large, energy-rich, and easily accessible to a bird perching on the flower head.

A broader economic analysis pooling five years of survey data estimated that the average annual total economic impact of bird damage to sunflower production across North Dakota, South Dakota, and Nebraska was roughly $18.7 million, $7.3 million, and $2.6 million, respectively. Combined direct and indirect losses for confectionery and oilseed sunflower hybrids averaged about $2.5 million and $11.3 million per year.⁶ These figures include not only the crop eaten by birds but also the costs farmers incur trying to deter them, from propane cannons and reflective tape to altered planting schedules.

Grackles are not the only blackbirds involved in crop damage, but their willingness to feed in large, coordinated flocks across open agricultural land makes them a major contributor. Their omnivorous diet also means they rotate between natural food sources, waste grain, and standing crops depending on what is available, so damage is not confined to one season or one crop type.

Health Concerns Around Large Roosts

Beyond agricultural losses, large grackle roosts raise genuine public health questions. The most well-documented concern involves Histoplasma capsulatum, a fungus that thrives in soil enriched by bird droppings. When a roost occupies the same location for years, the fungal spores can accumulate to levels that become hazardous if the soil is disturbed.

In one documented case in Illinois, researchers isolated the fungus from 27 out of 34 soil samples collected at an estate that had hosted a bird roost for more than a decade. When the property was sold for commercial development, health officials worried that construction would release clouds of spores into the air, posing a risk to workers and the surrounding community.⁷ Inhaling Histoplasma spores can cause histoplasmosis, a respiratory infection that ranges from mild and flu-like in most people to severe and potentially life-threatening in those with weakened immune systems.

This is not a hypothetical risk confined to one property. Anywhere a large roost has persisted for years, particularly in warm, humid climates with moist soil, the same fungal buildup can occur. Cities that host recurring winter grackle roosts in the same trees or structures year after year accumulate droppings that create ideal conditions for Histoplasma. The practical takeaway is that disturbing soil beneath a long-standing bird roost, whether through construction, landscaping, or cleanup, should be done with precautions such as wetting the soil to suppress dust.

Grackle Species in North America

When people talk about grackle flocks, they are usually referring to one of three species, each with somewhat different habits. Common grackles are the most widespread, found across the eastern two-thirds of the continent. Great-tailed grackles dominate the Southwest and have been expanding northward aggressively. Boat-tailed grackles stick close to the Atlantic and Gulf coasts. All three form large flocks, but the common grackle is the species most likely behind those enormous winter roosts in suburban parking lots and highway corridors east of the Rockies.

The great-tailed grackle is the expansion specialist of the group. Research comparing the two southern species found that the great-tailed grackle has shifted its ecological niche as part of its rapid spread, moving into human-altered habitats like irrigated farmland, urban parks, and fast-food parking lots. This behavioral flexibility is consistent with observations that species capable of adjusting their habits can rapidly extend their range by exploiting environments that other birds would avoid.⁸ The boat-tailed grackle, by contrast, has stayed closer to its traditional coastal marsh habitat, and its range dynamics appear to be shaped more directly by shifts in climate than by behavioral innovation.

A Range That Keeps Expanding

If you feel like you are seeing more grackles than you used to, you might be right. Climate modeling studies project that the common grackle’s range will expand significantly northward over the coming decades. Annual mean temperature is by far the most important variable predicting where common grackles can live, accounting for about three-quarters of the model’s predictive power.⁹ As winters warm, previously inhospitable territory in northern Canada and potentially Alaska opens up.

This is not a new pattern. Reconstructions of the common grackle’s historical range suggest that during the last ice age, its suitable habitat was compressed into the southern portion of North America, including the Florida peninsula. Since then, the species has expanded its distribution area by more than 300%.⁹ Future projections suggest further significant expansion even under relatively optimistic climate scenarios, pushing into northern parts of North America that currently see few or no grackles.¹⁰

For people living in areas where grackles are already abundant, this means the massive fall and winter roosts are unlikely to shrink anytime soon. For people in northern regions who have only occasionally encountered these birds, the “plague” may be coming your way. The combination of warming temperatures, abundant human-provided food sources, and the grackle’s remarkable adaptability to urban environments makes continued range expansion likely over the next half century.

Living With the Plague

Grackles occupy an unusual cultural niche among North American birds. They are too common and too noisy to inspire the same affection as cardinals or bluebirds, but they are also undeniably impressive animals. Their iridescent plumage shifts from black to purple to bronze in the right light. They are remarkably intelligent foragers, known to dip hard food in water to soften it and to follow lawn mowers to snatch up displaced insects. And their ability to thrive in cities, suburbs, agricultural landscapes, and wild habitat alike puts them among the most successful birds on the continent.

Managing large urban roosts remains a genuine challenge. Cities have tried everything from recorded predator calls and laser deterrents to pruning roost trees and installing bird spikes on ledges. Results are mixed at best. The birds often simply relocate to the next block. Researchers who study blackbird management have noted that the regulatory framework around these efforts is complex, involving federal protections under the Migratory Bird Treaty Act alongside state-level permits for lethal control in agricultural settings.¹¹ You cannot simply poison or shoot a roost of grackles, even if they are covering your car in droppings every night. The legal landscape reflects the broader tension between the genuine economic and health costs of massive roosts and the fact that grackles are native wild birds performing their natural behaviors at a scale that happens to inconvenience humans.

For backyard birders frustrated by grackles dominating their feeders, some practical adjustments help. Switching to safflower seed, which grackles dislike but cardinals and chickadees eat readily, can reduce grackle visits. Tube feeders with short perches are harder for the larger-bodied grackles to use. Weighted feeders that close under heavier birds also work. None of these methods will eliminate grackle visits entirely, but they shift the balance. The plague, it turns out, can at least be negotiated with.