Michael J. Bodenchuk 

State Director 

USDA-APHIS-Wildlife Services 

San Antonio, Texas 

 

David L. Bergman

State Director 

USDA-APHIS-Wildlife Services 

Phoenix, Arizona 

Human-Wildlife Conflicts

Numbering in the tens of millions of birds, 

grackle populations in North America can 

cause a variety of conflicts with people. 

Grackles eat agricultural crops and 

livestock feed, damage property, spread 

pathogens, and collide with aircraft. Their 

large roosts can be a nuisance in urban 

and suburban areas. A combination of 

dispersal techniques, exclusion, and lethal 

removal may help to reduce grackle 

damage. 

Agricultural Crops and Landscapes

Grackles feed upon and damage grain and 

fruit crops, including rice, corn, wheat, 

tomatoes, watermelon, lettuce, figs, citrus, 

and cantaloupe. Newly planted rice in 

southern states is often consumed by 

grackles prior to the birds’ spring 

migration. In peanut-growing areas, 

common grackle (Quiscalus quiscula) 

(Figure 1) damage can result in crop 

losses up to 25 percent after windrowing. 

A 1969 to 1971 study in Oklahoma 

showed that more than 72 percent of 

common grackles captured in peanutgrowing areas had peanuts in their 

gizzards.

Where producers grow sunflowers and 

corn simultaneously, sunflowers receive 

more damage than corn. Grackles feed on 

sunflowers during the early ripening stage. 

Sunflower fields located near wetlands 

receive 2 to 4 times more damage than 

Wildlife Damage Management 

Technical Series

U.S. Department of Agriculture

Animal & Plant Health Inspection Service

Wildlife Services

April 2020 Grackles

Figure 1. Common Grackle (Quiscalus quiscula)

Quick Links

Human-Wildlife Conflicts 1

Damage Identification 3

Management Methods 4

Economics 7

Species Overview 8

Legal Status 12

Glossary & Key Words 13

Resources 14 

Appendix 16 
fields in other locations. Common grackle damage to 

sunflowers does not subside until late fall. 

Common grackles will pull up sprouting corn, feed on corn 

during the milk and dough stages when the kernels are 

soft, and on mature field corn in the dent stage, removing 

the entire kernels from the cob. Throughout the Midwest, 

common grackles cause extensive damage to ripening 

corn. In Southern Ontario, common grackles are most 

active in corn fields during May and June and in grape 

vineyards during July. 

Great-tailed grackle (Quiscalus mexicanus) damage to 

ripening oranges and grapefruit (Figure 2) in south Texas 

varies in type and economic importance. Fruit with 

cosmetic damage, small pecks and/or scratches on the 

fruit peel are downgraded and reduced in value. Holes 

poked in the fruit or pulp cause blemishes that make the 

fruit unfit for direct consumption. Grackles damage citrus 

to acquire monoterpenes from the peel. The birds spread 

the monoterpenes on their feathers to kill ectoparasites. 

Grackle damage to fruit starts in the spring on immature 

citrus and extends through the fall and winter on ripening 

fruit. The most significant damage occurs after the 

breeding season during July through September as birds 

prepare for migration.

Because it is difficult to disperse great-tailed grackles from 

citrus groves during the summer, producers and managers 

often resort to lethal removal. 

Droppings from grackle winter roosts change soil pH and 

damage ornamental trees, (e.g., Bradford pear trees), 

harvestable trees (e.g., loblolly pine), and turf. Small 

ornamental plants, especially when sprouting, are 

damaged directly by foraging birds. 

Livestock and Aquaculture

Grackles are agricultural pests at feedlots and dairy farms. 

They eat livestock feed and spread bacterial pathogens 

that may impact cattle and milk production. Rates of feed 

consumption vary with the weather and number of birds. 

Salmonella and Escherichia coli O157:H7 may be spread 

mechanically (i.e., on feathers and feet) and through 

droppings by grackles and other blackbirds in mixed flocks 

both within a feedlot and between feedlots. 

Great-tailed grackles, pigeons (Columbia livia), European 

starlings (Sturnus vulgaris) and mourning doves (Zenaidura 

macroura) cause the greatest economic losses in 

southwestern cattle feeding operations. 

Common grackles also have been known to prey upon fish 

in fish hatcheries, natural ponds and aquaculture facilities.

Structures

In some winter roosts, grackles concentrate on powerlines, 

as well as on nearby trees and shrubs. When grackles 

depart en masse from powerlines, the lines oscillate wildly, 

often contacting other lines or structures and causing 

power outages. A single power outage caused by birds can 

easily cost over $10,000 in repairs and lost productivity. 

Human Health and Safety

Winter roost sites for mixed blackbird flocks, including 

grackles, typically result in large concentrations of fecal 

droppings that can serve as a fertile medium for the 

fungus Histoplasma capsulatum. If the soil under these 

Histoplasma-positive roost sites is disturbed, the fungal 

spores can be released resulting in a human health 

hazard. If inhaled, the fungal spores cause a lung infection 

in people called histoplasmosis. 

Grackles can be a significant threat to aviation safety 

where large winter roosts or croplands used for feeding

Figure 2. Grackle damage to grapefruit.

Page 2 WDM Technical Series─Grackles
coincide with aviation flight paths. According to a U.S. 

Federal Aviation Administration report, from 1990 to 2013, 

the following number of aircraft-bird collisions occurred by 

species: boat-tailed grackle (Quiscalus major) (22), greattailed grackle (37), common grackle (122), unidentified 

grackle species (125), and blackbirds (1,271). The 

blackbird category likely included grackles due to their 

tendency to join mixed flocks. 

Nuisance Problems

In urban and suburban settings, large grackle roosts can 

be noisy. The noise can last throughout the night, if the 

area is well lit. Nuisance complaints also arise because of 

droppings, especially on houses and cars located under 

roost trees and structures. 

Grackles can attack people and pets when they perceive a 

threat to nests or young. Minor injuries to people have 

been documented. 

Damage Identification

Because of their gregarious nature, grackles are easily 

observed and identified. Nuisance complaints are 

determined from visual observations, noise, and fecal 

droppings. 

Citrus damage requires close inspection, as grackles may 

peck only one small hole in the fruit that is not visible until 

picked. Systematic searches of ripening fruit must be 

made if grackles are observed in orchards. Inspect hanging 

fruit from a ladder to determine the whether fruit is being 

damaged. 

Blackbird damage to agricultural seed crops often is easy 

to identify because the flocks of birds and the visible signs 

of the damage are conspicuous. However, correct 

identification of the species of birds in the agricultural field 

is important, along with evidence that the birds are actually 

feeding on the crop. For example, European starlings 

superficially resemble blackbirds and sometimes feed in 

cornfields, yet they usually feed on concentrations of 

insects, such as armyworms, and cause little, if any, 

damage to corn. Also, red-winged blackbirds often are 

attracted to agricultural fields, such as corn and sunflower, 

initially feeding on rootworm beetles, sunflower weevils, 

and other insect pests. They will not damage the crop itself 

until the grain has reached the milk stage. Blackbirds often 

forage in newly planted grain fields, such as winter wheat, 

feeding on previous crop residue, weed seeds, and insects 

without bothering the sprouting grain. Blackbirds can, 

however, cause serious damage to newly sprouted rice.

Blackbird damage also can be confused with other forms 

of loss. Deer, raccoon, and squirrel damage to corn can be 

mistaken for blackbird damage. Also, seed shatter in 

sunflower caused by wind may resemble bird damage; 

however, the difference usually can be detected by 

examining sunflower heads for the presence or absence of 

bird droppings and by looking on the ground for hulls or 

whole seeds. Careful observation of the birds in the field 

and a little detective work usually will result in the correct 

identification of the cause of damage. 

To accurately estimate the amount of blackbird damage in 

an agricultural field, examine at least 10 locations widely 

spaced throughout the field. For example, if a field has 100 

rows and is 1,000 feet long, walk staggered distances of 

100 feet along every 10th row (for example, 0 to 100 feet 

in row 10, then 101 to 200 feet in row 20, and so on). In 

each of the 100-foot lengths, randomly select 10 plants 

and visually estimate the damage on the head or ear of 

each plant to the nearest 1% (for instance, 2% destroyed, 

20% destroyed). For corn, six kernels usually represent 

about 1% of the corn on an ear; for sunflower, it may be 

easiest to visually divide the head into four quarters and 

then estimate the percentage of seeds missing. When 

finished, simply determine the average damage for the 

100 plants examined. This will give an approximation of 

the percent loss to the field. Multiply the percent loss by 

expected yield to get a rough estimate of yield loss. In 

small grains, such as rice, estimates of loss are more 

difficult to obtain. One possibility is to compare the yields 

from plots in damaged and undamaged sections of a field. 

Page 3 U.S. Department of Agriculture
Management Methods

Grackles adapt easily to human-dominated environments, 

and exploit human food and other features of human 

landscapes. Thus, an integrated damage management 

approach to grackle damage focuses on reducing and 

eliminating the damage, rather than simply controlling 

grackle populations. 

The effectiveness of management methods varies 

considerably by bird species and crops. Strategies that 

work in one situation might not be applicable in another. 

For example, a strategy to manage damage in rice fields 

where blackbirds feed and roost will likely differ from a 

strategy to protect sunflower fields where blackbirds only 

feed. Additionally, a repellent application that is effective 

with common grackles might not be as effective with larger 

species, such as great-tailed grackles. 

The timing of management activities is important. 

Management is most effective when done just prior to 

planting a vulnerable crop or just prior to the crop ripening. 

Producers should also be knowledgeable of grackle 

movement and behavior. For instance, southern rice 

growers can best protect their crops if they are planted 

after most blackbirds have migrated north, usually after 

late March.

The effectiveness of certain methods to prevent bird 

damage to citrus varies considerably from season to 

season. From April to July, the birds congregate in small 

breeding colonies which makes them more susceptible to 

baiting and toxicants. From August to October, the birds 

can be baited into and treated with toxicants. Intensive 

shooting and use of pyrotechnics can also be successful at 

this time of year at groves with high grackle 

concentrations. From late October to March, birds travel 

widely each day and are easily frightened from groves by 

pyrotechnics and shooting. Depending on the cost and 

duration of the damage to citrus and other fruits, exclusion 

with netting and hazing may be successful. Otherwise, 

habitat modification, repellents and lethal removal may be 

tried. 

Habitat Modification

Habitat modification to disperse roosts may be effective 

when trees are used for thermal cover in the winter. 

Pruning trees to open the canopy reduces the thermal 

cover and forces the grackles to roost elsewhere. Pruning 

trees is not effective in southern climates, however, where 

trees and powerlines are selected for predator defense 

and not for thermal cover. Roost structures may be 

completely removed, but the birds may relocate to a new 

roost location nearby.

Mechanical methods (e.g., mowing, disking or burning) for 

managing cattail roosts and nesting areas used by mixed 

flocks are labor-intensive, expensive, and often ineffective 

because the stands quickly reestablish themselves. 

Cattails can be managed by flooding, but cattail-dominated 

wetlands in the prairie pothole region seldom have water 

controls to facilitate flooding. 

Sometimes glyphosate herbicide is aerially applied for 

controlling cattails due to the limitations associated with 

mechanical treatments and flooding. Aerial application is 

recommended for managing cattails because basin areas 

usually are too large for ground-based sprayers. Cattails 

should be treated with glyphosate during the late summer 

when the plants are most actively metabolizing and 

transporting carbohydrates to their rhizomes (i.e., 

Page 4 WDM Technical Series─Grackles

Figure 3. Netting may offer some protection for blueberries.
underground stems). Treatments can last for more than 4 

years, if water levels remain stable. To prevent blackbird 

use of cattail, the ideal ratio of open water to cattails is 

70:30. For greatest success, water levels should remain 

stable at a depth of more than one foot. 

Exclusion

Nets are used to exclude grackles from small trees, 

gardens, or vines with ripening fruit. The use of netting for 

large-scale applications is often cost-prohibitive. Exclusion 

wires, such as porcupine wires, may prevent grackles from 

roosting on some human-made objects, such as light 

fixtures, and reduce damage associated with droppings on 

cars and equipment. 

Netting is effective in the protection of blueberries (Figure 

3). Netting is expensive to use and many owners of small 

plantings do not invest in it. Unfortunately, it is these small 

producers who tend to experience more severe bird 

damage. 

In south Texas, several citrus grove owners used 

monofilament lines placed in grids of 10, 23, and 36 feet 

apart and 3 feet above the canopy of their trees to prevent 

damage from great-tailed grackles. These protected groves 

experienced less damage than unprotected groves; 

however, preliminary results indicated that the grids only 

were cost-effective when damage levels were high.

Frightening Devices

Grackles may be hazed from roost sites using 

pyrotechnics. However, continuous, multiple-night efforts 

are often required to move the birds from well-established 

roosts. 

Propane cannons and pyrotechnics are effective in citrus 

groves to reduce great-tailed grackle damage. Both are 

used extensively in sunflower fields to reduce common 

grackle damage. Propane cannons can be made more 

effective by elevating them above the crop, using timers, 

and allowing the cannons to rotate and fire in alternative 

directions. The use of scarecrows can enhance the 

effectiveness of propane cannons.

Mylar tape or helium-filled “eye-spot” balloons (Figure 4)

may be used to protect small areas, such as gardens, for a 

limited period of time. However, long-term efficacy should 

not be expected. Mylar tape is ineffective for protecting 

large citrus groves from great-tailed grackles. 

Although frightening techniques help reduce damage to 

citrus during the late fall and winter, site tenacity by greattailed grackles makes these methods less effective during 

the post-breeding period of July through September.

Repellents

Methyl anthranilate (MA) is registered as a repellent for a 

wide variety of birds and situations (see EPA Reg. No. 

33162-1). The naturally-occurring compound stimulates 

the trigeminal nerves in a bird’s beak, eyes, and throat 

causing discomfort. MA can be used on grass and turf to 

prevent grazing (particularly by geese) and on ripening 

fruit, rice, sunflowers, and other crops to prevent pecking. 

MA products may not be cost-effective for nuisance 

damage if their use requires repeated applications over a 

large area. 

MA products are water soluble, so they must be reapplied 

following irrigation or rain. MA is not registered for use in 

feedlots or dairies, nor is it effective at preventing damage 

associated with roosting birds. Applicators should read and 

follow label directions and contact their state pesticide 

regulatory agencies to determine if MA requires special 

pesticide licensing. MA products may not be used in 

California or Nebraska. 

Page 5 U.S. Department of Agriculture

Figure 4. “Eye-spot” balloons may help protect small areas from grackle 

damage for a limited period of time.
Toxicants

DRC-1339 (3-Chloro-4-methylbenzenamine) is an oral 

toxicant registered for use with grackles in both 

commercial animal operations and non-crop areas where 

grackles gather and feed, loaf, or roost. DRC-1339 may 

only be used by USDA-APHIS certified applicators trained in 

bird control or by persons under their direct supervision. 

DRC-1339-treated baits are fed to birds as part of a 

mixture of treated and untreated bait. Rice, fat pellets, 

cracked corn, distiller’s grain, french fries, dog food, and 

watermelon have been used as bait. Birds consuming 

DRC-1339 metabolize the chemical and die of renal failure 

within 1 to 3 days, usually at roost sites. Applicators should 

carefully examine every application project to determine 

where birds may die. It is recommended that local 

authorities and the public be notified when large bird 

mortalities in populated areas are anticipated. Special 

local needs labels may be approved under certain 

circumstances. 

DRC-1339 can be used to reduce migrating blackbird 

populations prior to nesting season. The application of 

DRC-1339-treated baits in corn stubble is more effective 

than soybean stubble, and rice bait is preferred over corn 

bait by blackbirds. However, the application of DRC-1339-

treated rice bait down bait lanes in ripening sunflower 

fields does not reduce local blackbird populations or 

sunflower damage. The use of bait trays is also ineffective. 

Trapping

Grackles can be trapped using decoy traps, funnel traps 

and drop nets. However, trapping usually is ineffective if 

food sources outside of the traps are readily available to 

the birds. 

A decoy trap is a large poultry wire or net enclosure 

containing 10-20 decoy birds, food, and water. Birds enter 

the trap through an opening in the top of the cage that is 

covered with a wire mesh. The birds can fold their wings 

and readily drop though the opening to the food below. 

Decoy traps have been effective at capturing grackles in 

small areas, notably at airfields where off-site food is 

unavailable. If decoy traps are used, care must be taken to 

prevent tampering by the public

Funnel traps (Figure 5) with entrances on the ground are 

more effective than decoy traps for capturing great-tailed 

grackles. 

Drop nets have been used successfully for small scale 

trapping, particularly at food sources or small roosts. Drop 

nets are weighted nets set on poles above the ground with 

a triggering device to release the net and allow it to drop 

on top of birds. They are normally used at locations where 

birds gather to feed or roost and may be used over bait. 

Neither traps nor drop nets are considered effective for 

large roost problems or for reducing fruit or citrus damage.

Shooting

While night shooting of birds in roosts may remove some of 

the animals, shooting is rarely effective at stopping 

damage. Shooting birds coming into a feedlot, dairy, or a 

crop field may reinforce hazing with pyrotechnics, but it is 

rarely an effective stand-alone tool. 

Other Control Methods

Decoy (lure) crops are used to entice feeding blackbirds 

away from valuable, commercial crops. The concept is 

simple—plant a small field (about 20 acres) of sunflowers 

Page 6 WDM Technical Series─Grackles

Figure 5. Funnel traps are sometimes used to capture grackles and 

other birds. 
or another crop, such as corn, that is attractive to grackles. 

The decoy crop and the commercial crop should be 

synchronized so they mature at the same time, otherwise 

the decoy crop will be less attractive to the birds. Do not 

spray the decoy crop with insecticides, and do not harass 

the birds using it. The goal is to keep the birds in the decoy 

crop as long as possible, thereby reducing the time they 

spend in the nearby commercial field. To encourage the 

birds to stay in the decoy field, farmers can continue to 

spray registered repellents and harass birds in their 

commercial field. In essence, the decoy crop is sacrificed 

to grackles to protect the harvestable crop. North Dakota 

producers who used decoy crops saved $2 to $4 for every 

$1 spent on the crops. Fields with associated decoy crops 

sustained less damage than fields without them. 

In addition to decoy crops, bird-resistant, nontoxic coatings 

for rice seeds have been studied to evaluate their 

effectiveness at reducing bird damage. The coated rice 

becomes sticky when wet and fouls the birds' bills so that 

they cannot feed efficiently. In a study using clay-coated 

rice, the amount of sprouting rice lost to birds decreased 

from 36.5 percent to 17 percent. Bird resistant varieties of 

sorghum, corn, and sunflower have also been studied and 

limited varieties have been produced to alleviate blackbird 

damage. 

Sodium lauryl sulfate (SLS) is a wetting agent (i.e., 

surfactant) used on grackles at roost sites. When applied 

to birds, SLS allows water to penetrate and saturate the 

feathers so that with low temperatures (< 41°F) and 

sufficient water, birds die of hypothermia. The product is 

for use on upland roosts located away from bodies of 

water. In some situations, it may be an appropriate 

alternative to DRC-1339. Check federal and state 

regulations before using SLS.

Relocation of roosting grackles in urban areas may be 

effective for reducing damage. Relocation of roosts can be 

accomplished with pyrotechnics, habitat modification or 

continued disturbance of the roost using low-powered 

lasers or water from a high-pressure hose. Relocation of 

the roost is particularly attractive as an alternative to lethal 

control. However, relocation may result in the movement of 

the roost to another area where damage may continue. 

Because grackles often feed over a large area surrounding 

their roost site, relocation of the roost is not an effective 

method for protecting crops. The exception may be when 

crops are planted in southern states around the same time 

that birds are preparing to migrate north. In these limited 

situations, the dispersal of the roost may trigger a northern 

migration away from all freshly planted crops. 

Handling

When handling birds, be sure to wear appropriate personal 

protective equipment, such as gloves and protective eye 

wear.

Translocation

Translocation of grackles is not considered effective for 

resolving most conflicts or significantly reducing roosting 

populations.

Euthanasia

Euthanasia of grackles may be done by cervical dislocation 

or by administering isoflurane or carbon dioxide gas to 

birds placed in a sealed container. Care should be taken to 

minimize stress and handling prior to euthanasia. Confined 

areas must be large enough to avoid stress to the birds as 

much as possible.

Disposal

Check your local and state regulations regarding carcass 

disposal.

Economics

There are no economic estimates for grackle damage to 

crops nationwide. Most national damage estimates are for 

mixed flocks that include grackles, European starlings, and 

several blackbird species. The following includes damage 

estimates in specific states.

Page 7 U.S. Department of Agriculture
In 1979 and 1980, results from a field survey indicated 

that sunflower producers in North Dakota sustained 

between $4 and $11 million in losses due to blackbird 

flocks that often contain a mixture of grackles, red-wingedblackbirds (Agelaius phoeniceus), yellow-headed 

blackbirds (Xanthocephalus xanthocephalus), and brownheaded cowbirds (Molothrus ater).

A 2003 bioenergetics model estimated blackbird damage 

to sunflowers in North Dakota at $5 to $10 million 

annually. Losses by blackbirds continue to remain high. 

Annual blackbird damages to corn and sunflower crops in 

North Dakota from 2008 to 2010 averaged $1.3 million 

and $3.5 million, respectively. The economic impact to 

sunflower producers in North Dakota, South Dakota, and 

Nebraska for the years 2009 to 2013 had an annual 

average loss from blackbirds of $18.7 million, $7.3 million, 

and $2.6 million, respectively.

In Florida, two types of tropical fruit— the lychee (Litchi 

chinensis) and longan (Euphoria longana)— are rapidly 

increasing in economic importance with a combined 

annual value of over $19 million. During the late 1990s, 

estimates of bird damage to longan ranged from 1 to 28 

percent ($640 to $43,546) per acre, with most of the 

damage caused by common grackles and monk parakeets. 

Bird damage to lychee was 11 percent or $1,179 per acre 

in only 1 of 4 of the groves studied. 

In 1989, producers identified European starlings, American 

robins (Turdus americanus), and common grackles as the 

3 most common species causing damage to blueberries in 

15 states and British Columbia. The survey also found that 

birds accounted for 10 percent of the losses to blueberry 

crops. With blueberries averaging $2.42 per pound, birds 

caused an estimated $8.5 million in blueberry damages 

nationwide. Common grackles also feed on cherries, 

showing a preference for sweet cherries over tart cherries. 

Damage estimates associated with cattle feed depredation 

are dependent upon feed mixture, but a 2010 study 

showed the economic losses were as high as $15.43 per 

100 kilograms ($6.99 per 100 pounds) of daily 

maintenance livestock feed. By eating the feed, birds 

deprive the livestock of important grain, starch and other 

nutrients. 

Page 8 WDM Technical Series─Grackles

Species Overview

Identification

Three species of grackles are present in North America: the 

common grackle, the boat-tailed grackle, and the greattailed grackle. A fourth species, the greater Antillean 

grackle (Q. niger) is present in Puerto Rico. All are part of 

the Family Icteridae that includes blackbirds, orioles, 

cowbirds, meadowlarks, and bobolinks.

Physical Description

The common grackle is 12.5 inches long, with a wing span 

of 17 inches, and weighs 4 ounces. The bird has glossy 

black feathers and pale yellow eyes. The male’s feathers 

are iridescent purple on the head, nape, and breast with 

bronze iridescence on the body and wings. Females are 

slightly less glossy than males. Young birds are dark brown 

with a dark eye. There may be a slight color variation 

between populations. Common grackles are larger than 

other blackbirds, such as red-winged blackbirds, Brewer’s 

blackbirds, and rusty blackbirds, with longer wings and a 

keeled tail. Males have distinctive mating displays. 

The male boat-tailed grackle is 16.5 inches long, with a 

wing span of 23 inches, and weighs 8.8 ounces. The 

female is slightly smaller (length 14.5 inches, wing span 

17.5 inches, weight 4.2 ounces). The male boat-tailed 

grackle is glossy black with greenish-blue iridescence. The 

female is blackish above with a rufous-brown breast and 

throat. Eye color varies between populations from brown to 

pale to yellow. The boat-tailed grackle is larger than other 

blackbirds and the common grackle, with longer wings and 

a keeled tail. Males have distinctive mating displays. The 

boat-tailed grackle is located in coastal saltmarshes and 

adjacent open areas, generally not flocking with other 

birds. 

The male great-tailed grackle (Figure 6) is 18 inches long, 

with a wing span of 23 inches, and weighs 6.7 ounces. 

Females are 15 inches long, with a 19-inch wing span, and 

weigh 3.7 ounces. The male is glossy black with uniform 

purple-blue iridescence. The female is blackish above with 
pale to dark greyish-brown on the breast and throat. Eye 

color varies between populations from brown to white. The 

great-tailed grackle is the largest grackle, with longer wings 

and an extremely long, keeled tail. Mating displays by 

males are distinctive. It is located in various upland 

habitats from farmlands to city parks. The great-tailed 

grackle forms large winter roosts. 

Range

The common grackle breeds throughout the United States 

and southern Canada east of the Rocky Mountains and 

south of Hudson’s Bay. It winters from Nebraska to Texas, 

and east to Pennsylvania and Florida (Figure 7). A native to 

North America, its range may have expanded due to 

agriculture and climate. 

The boat-tailed grackle is found on the coastal Atlantic, 

south of Massachusetts through all of Florida and the U.S. 

Gulf coast through Texas (Figure 8). It is native to North 

America. 

The range of the great-tailed grackle extends from 

Louisiana and western Arkansas, west through Colorado, 

Utah, southern Nevada and southern California, and 

southward through northern Mexico (Figure 9). Native to 

North America, its range may have expanded due to 

agriculture and climate. 

Voice and Sounds

The common grackle’s song is not musical— it consists of a 

harsh, toneless hiss (“kh-sheee or kh-reezzh”). Its call is a 

harsh, dry “karrz” or “kerrr,” and the male’s call is a thin, 

wheezy, toneless “zweeesh” and a nasal, hoarse “krrrjk”.

The song of the boat-tailed grackle is a varied series of 

high, ringing notes “kent, kent,” or “teer, teer”. The male 

call is a deep “chuk”.

The great-tailed grackle’s song is a series of loud, 

unpleasant noises and mechanical rattles of “kikikiki” or 

“ke ke ke ke ke teep”. The male’s call is a low, hard “chuk” 

or “kuk”. 

Page 9 U.S. Department of Agriculture

Figure 6. A male great-tailed grackle (Quiscalus mexicanus) . The greattailed grackle is the largest of the three grackle species in North America.

Figure 7. Distribution of common grackles. 
Reproduction

Female grackles breed during their first year. Common 

grackle and great-tailed grackle males also breed during 

their first year, although the territorial breeding behavior of 

great-tailed grackles does not always allow for yearling 

males to establish breeding territories. Male boat-tailed 

grackles do not breed until their second year.

Average clutch size for all three species is 3 to 5 eggs with 

a range of 1 to 5 eggs for great-tailed and boat-tailed 

grackles and 1 to 7 eggs for common grackles. All three 

species typically raise 1 clutch, but may raise a maximum 

of 2 clutches per year.

Common grackle males assist in defending the nest and 

raising chicks, but great-tailed grackle and boat-tailed 

grackle males do not. Differential survival rates for male 

and female boat-tailed grackles yields a breeding season 

sex ratio of 2 females per male, with a corresponding 

increase in population fecundity.

Following a nest building period of 1 to 6 weeks, female 

grackles lay their eggs. Incubation for all grackle species is 

11 to 15 days. Boat-tailed and common grackle chicks 

fledge in 10 to 17 days, while great-tailed grackle chicks 

fledge in 20 to 23 days.

Male great-tailed grackles do not participate in the raising 

of young, leaving nest building, incubation, and feeding of 

nestlings and fledglings to the females. Great-tailed 

grackles experience nest loss during the breeding season, 

with hatching success rate of 55 to 89 percent and a 

nestling fledging rate of 36 to 93 percent. 

Nesting Cover

Female grackles build nests, preferably in the tree canopy 

and out of reach of predators. All species of grackles are 

“loose colonial breeders” (i.e., nesting and breeding in 

close proximity as a group), but single nests may also 

occur. 

Common grackles prefer to nest colonially in shelterbelts 

near inhabited farms. In North Dakota, one study 

estimated a mean density of 0.2 common grackle colonies 

and 3.4 nests per square mile. Common grackles have a 

preference for blue spruce (Picea pungens), but also nest 

in Siberian elm (Ulmus pumila), box elder maple (Acer 

negundo), caragana (Caragana arborescens) and 

hawthorn (Crataegus monogyna).

Because boat-tailed grackles are found primarily along the 

coast, nests are often built in cattail or other marsh 

vegetation, above the reach of flood waters. 

Page 10 WDM Technical Series─Grackles

Figure 8. Distribution of boat-tailed grackles. Figure 9. Distribution of great-tailed grackles. 
During the nesting season in south Texas, great-tailed 

grackles prefer to nest and roost in huesache (Acacia 

farnesciana), mesquite (Prosopis qlandulosa) and ebony 

(Pithecellobium flexicaule) thickets. 

Mortality

The rat snake (Elaphe obsoletta) has been identified as a 

common predator on grackle nestlings. Texas indigo 

snakes (Drymarchon melanurus erebennus) feed on greattailed grackle nestlings, and purple gallinules (Porphyrula 

martinica) are known to eat boat-tailed grackle chicks. 

During a 7-year study in South Carolina, approximately 61 

percent of common grackle nests fledged at least 1 young. 

Depredation was the leading cause of common grackle egg 

and nestling mortality (32.3 percent), while 27.2 percent of 

nestlings died of starvation. Nestling losses due to 

starvation are probably greater for the great-tailed grackle. 

Population Status

The population status of all three grackle species is 

considered common to overabundant. 

Common grackle populations peak in August and 

September when sunflowers reach their maturity. In the 

prairie pothole region of North Dakota, South Dakota, 

Minnesota, and Canada, the size of the fall population of 

common grackles is estimated to be 19 million birds. 

Typically, boat-tailed grackles do not associate with other 

species of birds and usually are found in small colonies 

during the breeding season. Both great-tailed grackles and 

common grackles may join other species in winter 

concentrations, roosting in mixed flocks numbering in the 

tens of thousands. Urban roosts may spread over several 

city blocks. 

Overall, great-tailed grackles have a sex ratio of 1.3 

females:1 male. The ratio varies throughout the year based 

on life history needs.

Page 11 U.S. Department of Agriculture

Habitat

Wetlands dominated by cattails can harbor more than 

70,000 blackbirds, including common grackles. Wetlands 

containing over 20,000 birds are common in the prairie 

pothole region of the United States. The peak roosting and 

staging period at Sand Lake, South Dakota, is from late 

August through September. The roosting habitat is 

dominated by cattails (Typha latifolia) with areas of 

phragmites (Phragmites spp.). 

Common grackles are known to roost in forested areas 

along Lake Texoma in southeastern Oklahoma in 

November. Their home ranges average 125 square miles. 

The minimum area used by the Lake Texoma roosting 

population is estimated at 768 square miles.

Boat-tailed grackles are associated with salt and fresh 

water marshes. They are rarely found more than 30 miles 

from the coast.

The use of chaparral, citrus, and residential areas by greattailed grackles is low during the winter, but increases 

sharply with the start of the nesting season in April. The 

species sometimes uses agricultural fields and pastures. 

Their use of feedlots is low during the summer, but high 

from October to April, with peak use in October and March 

when the birds are migrating.

Behavior

Grackles are diurnal birds that forage from nest sites or 

roost areas. Great-tailed grackles and common grackles 

form large winter roosts, often mixing with other species of 

blackbirds. 

Common grackles may exhibit communal nesting with little 

to no territoriality except immediately surrounding the 

individual nests. All species of grackles form loose pair 

bonds with 1 male breeding with 1 or more females, and 1 

female mating with 1 or more males. Males play a minor 

role in building and repairing nests or feeding young. 

Molting occurs during late summer.
Figure 10. Common grackle at bird feeder.

Common grackles are habitat generalists that nest in a 

variety of habitats, including open woodlands, swamps, 

and areas around human habitation.

The primary winter roosting period in the southern rice belt 

states of Arkansas, Louisiana, and Texas is from December 

15 to January 31. During the winter, more than 80 percent 

of blackbirds in the southern rice states are from northern 

breeding areas. Approximately 50 percent of the redwinged blackbirds, cowbirds, and grackles that breed in 

eastern North America winter in rice producing states. 

Migrant blackbirds leave southern roosts in mid-February 

to early March.

Food Habits

Grackles are primarily granivores and eat agricultural seed 

crops, as well as hard and soft mast. They feed in 

agricultural areas, forests, open spaces and humandominated landscapes. 

Grackles forage on the ground. In the summer, animal 

matter, such as worms, grasshoppers, spiders, moths, 

salamanders, small fish, mice and the eggs of other birds, 

make up 25 percent to 50 percent of their diet. From July 

to mid-August, grackles eat primarily small grains (42 

percent) and insects (34 percent), whereas, between midAugust and late October small grains (36 percent) and 

sunflower seeds (48 percent) are important food items. In 

the winter, human-provided food sources, such as garbage 

and birdseed (Figure 10), make up a significant part of 

their diet. 

Overall, crop and habitat availability influence the diet of 

common grackles. In North Dakota, insects comprise 79 

percent of the diet for common grackles during May and 

June. During the summer, the amount of sunflower seeds 

in a grackle’s diet can increase dramatically. 

Boat-tailed grackles (Figure 11) often feed in shallow 

water, wading and plunging their heads into the water to 

capture prey. 

Legal Status

All grackles are federally protected by the Migratory Bird 

Treaty Act, but actions to control damage, including lethal 

take, is allowed under a “Standing Depredation Order” (50 

CFR 21.43) which allows take of grackles “...when found 

committing or about to commit depredations upon 

ornamental or shade trees, agricultural crops, livestock or 

wildlife, or when concentrated in such numbers and 

manner as to constitute a health hazard or other 

nuisance.” The federal standing depredation order 

overrides state regulations or the need for a state permit.

Page 12 WDM Technical Series─Grackles

Figure 11. Boat-tailed grackle illustration.
U.S. Department of Agriculture Page 13

Acknowledgements

Figure 1. Photo by Thomas Barnes, U.S. Fish and Wildlife Service

Figure 2. Photo by Texas A&M Extension Service

Figure 3. Photo by Jan Hygnstrom

Figure 4. Photo by John Humphreys, USDA-APHIS-Wildlife Services

Figure 5. Graphic by Thomas Hall, USDA-APHIS-Wildlife Services

Figure 6. Photo by John and Karen Hollingsworth, U.S. Fish and Wildlife Service

Figures 7-8. Maps from The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology.

Figure 9. Map from Terry Sohl, https://www.sdakotabirds.com

Figure 10. Photo by Kevin Keirn

Figure 11. Graphic by Louis Agassiz Fuertes, U.S. Fish and Wildlife Service

We thank Page Klug and Kevin Grant for providing critical reviews of this manuscript. 

Key Words

Grackle, Quiscalus major, Quiscalus mexicanus, Quiscalus 

quiscula

Disclaimer

Wildlife can threaten the health and safety of you and 

others in the area. Use of damage prevention and control 

methods also may pose risks to humans, pets, livestock, 

other non-target animals, and the environment. Be aware 

of the risks and take steps to reduce or eliminate those 

risks. 

Some methods mentioned in this document may not be 

legal, permitted, or appropriate in your area. Read and 

follow all pesticide label recommendations and local 

requirements. Check with personnel from your state 

wildlife agency and local officials to determine if methods 

are acceptable and allowed. 

Mention of any products, trademarks, or brand names 

does not constitute endorsement, nor does omission 

constitute criticism. 

Citation

Bodenchuk, M.J. and D.L. Bergman. 2020. Grackles. 

Wildlife Damage Management Technical Series. USDA, 

APHIS, WS National Wildlife Research Center. Fort Collins, 

Colorado. 16p.

Glossary

Diurnal: Active during the daytime. 

Ectoparasite: A parasite that lives on the outside of its 

host. 

Granivore: An animal that feeds on the seeds of plants as a 

main or exclusive food source, in many cases leaving the 

seeds damaged and not viable. 

Monoterpene: A component of fragment oils found in 

leaves, flowers, and fruits. 

Pyrotechnics: Flares or cartridges fired from a gun or 

launcher that produce a loud blast or scream accompanied 

by smoke and a flash of light. 

Relocation: The act of moving an animal from one spot to 

another. For example, moving an animal from your attic to 

the backyard.

Staging Period: During migration, a time when birds rest 

and feed to improve body condition and increase body fat. 

Translocation: The act of moving an animal outside of its 

original home range, usually a considerable distance away. 
Page 14 WDM Technical Series─Grackles

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U.S. Department of Agriculture
Appendix 

Page 16

 

 

Type of Control 

 

Available Management Options 

Exclusion Netting to protect ripening fruit

Frightening Devices  Lasers, pyrotechnics, and propane cannons at roost and feeding sites; May provide short-term 

relief in airport environments 

 Mylar tape or helium-filled “eye-spot” balloons to protect limited areas, such as gardens, for a short 

period of time

Habitat Modification  Trim roost trees to open the canopy and reduce noise and droppings 

 Remove nests to reduce attacks on people or pets or mitigate hazards near aircraft

 Remove roosting habitat (cattails and trees) in the prairie pothole region to reduce damage to 

nearby crops 

 Desiccants to advance the harvest date of crops

 Modify planting and harvesting times of crops

Repellents  Avitrol (Avitrol Corporation) to frighten and disperse flocking birds (4-aminopyradine)

 Avipel® Shield (Arkion Life Sciences) seed treatments for newly planted corn seeds (9,10-

anthraquinone)

 AV-1011® (Arkion Life Sciences) seed treatments for newly planted rice seeds in AR, LA, MS, MO 

and TX (9,10-anthraquinone)

 Methyl anthranilate sprayed or used as fog on lawns or other surfaces to repel congregating birds

 Lemon grass oil, garlic oil, clove oil, peppermint oil, rosemary oil, thyme oil and white pepper are 

registered as bird repellents or are exempt from EPA registration 

Shooting Remove individual birds or reinforce the effectiveness of propane cannons and other pyrotechnics

Toxicants DRC-1339 (3-chloro-4-methylbenzenamine)

Trapping Decoy traps, funnel traps or drop nets

Other  Decoy (lure ) crops

 Bird-resistant seeds and crops

 Sodium lauryl sulfate (SLS) for controlling roosts 

 Relocation of roosts using a variety of management methods

Damage Management Methods for Grackles