Richard A. Dolbeer 

Science Advisor 

USDA-APHIS-Wildlife Services 

Airport Wildlife Hazards Program

Washington, D.C.

George M. Linz 

Research Wildlife Biologist 

USDA-APHIS-Wildlife Services 

National Wildlife Research Center 

Fargo, North Dakota 

Human-Wildlife Conflicts

Landscapes

Red-winged blackbirds can cause 

considerable damage to ripening corn, 

sunflower, sorghum, wheat and oats in the 

milk and dough stages, and sprouting and 

ripening rice. The closely related tricolor 

blackbird does some damage to ripening 

rice in California. Damage by common 

grackles is similar, except that grackles will 

feed on mature field corn in the dent 

stage, removing entire kernels from the 

cob. Common grackles also will pull up 

sprouting corn. 

Great-tailed grackles damage various fruits 

and melons, although the loss generally is 

minor. In recent years, however, their 

damage to citrus crops in localized areas 

of the lower Rio Grande Valley of Texas 

has been substantial. Great-tails peck the 

citrus fruit skin, creating blemishes or 

holes. Boat-tailed grackle (Quiscalus 

major) is a species of the Gulf and 

southeastern and mid-Atlantic coasts that 

is very similar in size and appearance to 

great-tails. They do some damage to 

sprouting rice.

Wildlife Damage Management 

Technical Series

U.S. Department of Agriculture

Animal & Plant Health Inspection Service

Wildlife Services

August 2016 Blackbirds

Figure 1. The red-winged blackbird (Agelaius phoeniceus) 

is one of the most abundant birds in North America; the 

late summer population probably exceeds 300 million 

birds. The black male, with striking red and yellow shoulder patches, is about 40 percent larger than the female. 

The female resembles a large sparrow more than a blackbird. 

Quick Links

Human-Wildlife Conflicts 1

Damage Identification 3

Management Methods 4

Economics 7

Species Overview 8

Legal Status 11

Glossary & Key Words 12

Resources 13 

Appendices 14 
Brown-headed cowbirds can cause damage to ripening 

sorghum, rice, millet; and sprouting rice. Yellow-headed 

blackbirds cause localized but generally minor damage to 

ripening corn and oats, often in association with redwings. 

Damage to early ripening sunflower can be high near 

wetlands; however, most yellowheads leave the northern 

prairie regions by the time corn and sunflower reach 

physiological maturity in mid-September. Brewer’s 

blackbirds generally cause minor damage to oats and fruit 

crops, but consume large numbers of noxious insects 

during the summer months. Rusty blackbirds typically 

cause little damage to crops. 

Female cowbirds lay their eggs in the nests of other 

songbirds. Cowbird nest parasitism has had a negative 

impact on populations of certain songbirds such as the 

endangered Kirtland’s warbler (Dendroica kirtlandii) and 

black-capped vireo (Vireo atricapillus).

Livestock

The increased use of feedlots and dairy farms by grackles 

in the northern areas of their expanding range may be a 

cause for concern in the future, due to the potential for 

disease transmission. Cowbirds consume some livestock 

feed, but often glean waste grain and seed from dung. 

Brewer’s blackbirds generally cause minor damage to 

livestock feed in feedlots.

Human Health and Safety

The close association of cowbirds and grackles with 

livestock at feedlots in winter (Figure 2) has the potential 

to amplify and spread disease to humans such as avian 

influenza although there is no evidence that this has 

happened.

The accumulation of feces at winter roosts (Figure 3), 

especially sites used in multiple winters, provides an 

enrichment of the soil favorable for the growth of the 

histoplasma fungus that can infect humans.

Flocks of blackbirds near airports (Figure 4) can cause a 

risk to flight safety because these birds can be ingested in 

large numbers into turbine-powered engines. 

Nuisance Problems 

Massive congregations of blackbirds and starlings in winter 

roost sites near human activity and habitations (Figure 4) 

can create nuisance concerns, as well as disease concerns 

as noted previously, because of the noise and 

accumulation of large amounts of feces and associated 

odors around the roost site. 

Figure 2. Flocks of blackbirds and starlings often concentrate in livestock 

feeding areas during winter where they compete with livestock for food and 

cause concerns regarding disease transmission to livestock and humans.

Page 2

Figure 3. Roosting concentrations of blackbirds in wooded areas near 

human activity can create a variety of problems, including damage to 

vegetation and the accumulation of feces with associated odor and disease 

concerns.

WDM Technical Series—Blackbirds
Blackbird damage to agricultural 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, starlings superficially 

resemble blackbirds and sometimes feed in cornfields, yet 

they usually feed on concentrations of insects such as 

armyworms, doing little, if any damage to corn. Also, redwinged blackbirds often are attracted to agricultural fields, 

such as corn and sunflower, initially to feed 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 (Figure 5). Also, seed shatter in sunflower caused by wind may resemble bird damage; however, the difference usually can be detected by 

examining sunflower heads (Figure 6) 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, 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. 

Damage Identification

Page 3

Figure 4. A mixed flock of several million blackbirds and starlings enter a 

winter roost site at dusk in a wooded area near the Memphis, Tennessee 

International Airport. During the day, these birds forage in woodlands and 

agricultural fields up to 30 miles from the roost.

Figure 5. Damage to ripening corn by blackbirds (left) and mammals (e.g., 

deer [right], raccoons, or squirrels) can sometimes be confused. Blackbirds 

usually slit or shred the husk and peck out the soft contents of kernels, 

leaving the kernel coats, which turn black. Deer, raccoons, and squirrels 

chew through the husk and bite off the kernels. In addition, raccoons often 

pull stalks down to ground, leaving muddy paw prints on the corn plant. 

U.S. Department of Agriculture
A key to damage prevention is the integration of multiple 

methods that are complimentary; a single technique used 

in isolation is seldom successful. Habitat management 

(see below) is the foundation of integrated pest 

management because these techniques provide long-term 

protection and enhance the effectiveness of control 

techniques such as frightening devices. 

As discussed below, it also is important to monitor the crop 

or situation and apply reactive control methods before or 

as soon as damage begins and only if damage is likely to 

be substantial. Money is often wasted when (1) control 

techniques are directed at blackbirds in crop-damage 

situations after the birds have already inflicted substantial 

damage and are migrating or moving to other ripening 

fields, or (2) the overall damage inflicted is minor (e.g., less 

than 1% of crop) and the cost of control exceeds the 

losses.

Habitat Modification

Most economically severe blackbird damage to agricultural 

crops occurs in fields within 5 miles of roosts. Thus, one 

strategy is to plant non-attractive crops; such as soybeans, 

wheat, potatoes, or hay; in fields within a few miles of a 

roost. If crops vulnerable to damage, such as corn or 

sunflower, are planted near a roost, make alternative 

feeding sites available to reduce the feeding pressure on 

these cash crops. Delay the plowing or tilling of previously 

harvested cropland near roosts to provide alternative 

feeding sites to reduce damage to maturing crops. Fields 

near roosts should not be planted unusually early or late so 

that they mature in isolation from other fields in the area. 

In general, as alternative feeding sites decline, maturing 

grain or sunflower fields become more attractive to 

blackbirds, and keeping them out becomes more difficult.

Damage to sprouting rice fields planted near blackbird 

roosts in Louisiana and Texas can be substantially reduced 

by delaying planting until April. By this time, the large flocks 

of migrant blackbirds will have left for their northern 

nesting areas. 

The timing of harvest can be very important in reducing 

damage to fields from flocks of blackbirds. For example, 

redwings inflict most damage to sweet corn at the time of 

fresh-market harvest, when the corn enters the milk stage. 

Timely harvest of sweet corn can substantially reduce 

damage. Field corn generally becomes unattractive to birds 

when the kernels mature. Sunflower, sorghum, and rice 

continue to be attractive after they mature and thus should 

be harvested as soon as possible. In some cases, a preharvest desiccant can be used on mature sunflower to 

advance dry down and harvest by 7-10 days. 

Figure 6. Typical damage by red-winged blackbirds to a ripening oil-seed 

sunflower head in North Dakota.

Page 4

Figure 7. Corn varieties with thick husks that extend beyond the cob (center 

ear) are less prone to damage by red-winged blackbirds compared to 

varieties with thinner, shorter-husked ears as demonstrated in this 

experiment in an aviary. 

Management Methods

WDM Technical Series—Blackbirds
Hybrids of corn with long husk extension and thick husks 

are more resistant to damage than other hybrids (Figure 7). 

Sorghum that contains a high tannin content also is less 

preferred than low-tannin varieties. For sunflower, birds 

prefer oil seed cultivars over the confectionery cultivars. 

Using sunflower cultivars with heads that turn downward 

as they mature and seeds with thick hulls should also help 

reduce feeding by blackbirds.

Studies of red-winged blackbird feeding habits in ripening 

corn fields revealed that they often are attracted to fields 

with high populations of insect pests such as rootworm 

beetles, corn borers, and Japanese beetles. Cultural practices or chemical applications to reduce these insects will 

make the fields less attractive to the birds.

Sunflower growers in the northern plains can thin out 

dense stands of cattails in marshes where large numbers 

of blackbirds roost near sunflower fields. Apply an aquatic 

formulation of the herbicide glyphosate in swaths to about 

70% of a cattail marsh. Thinning the cattail stands usually 

decreases or eliminates blackbird roosts in a marsh and 

increases use by waterfowl for nesting and other activities.

Exclusion

Exclusion of blackbirds and other birds from agricultural 

crops is practical only for small gardens, experimental 

plots, and high-value fruit crops. Use lightweight nets to 

cover trees, bushes, or small plots. 

Protect individual ears of sweet corn in garden plots by 

placing paper bags over them after the silk has turned 

brown.

Frightening Devices

The use of frightening devices can be quite effective in 

protecting crops from flocks of blackbirds. Their use also 

requires hard work and long hours for the farmer, who 

needs to be persistent and innovative to keep one step 

ahead of the birds. It is especially important for devices to 

be employed in the early morning and in late afternoon 

when the birds are feeding most actively. Crops such as 

sweet corn, which are vulnerable to blackbirds for only a 

few days before harvest, may not be too difficult to protect; 

however, the task becomes formidable for crops such as 

sunflower and sorghum, which may be vulnerable for up to 

6 weeks. 

The effectiveness of frightening devices is highly variable, 

depending on the persistence of the operator, the skill 

used in employing a device, the attractiveness of the crop, 

the number of birds, and the availability of alternate feeding sites. Birds tend to adjust or adapt to frightening devices. It is usually better to use two or more devices than to 

rely on a single device.

Auditory

Propane exploders are the most popular frightening devices. Some have timers that automatically turn them on and 

off each day or have remote-controlled activators. In general, use at least one exploder for every 10 acres (4 ha) of 

crop to be protected. Elevate exploders on a barrel, stand, 

or truck bed to “shoot” over the crop, and move them 

around the field every few days. In addition, reinforce this 

technique occasionally with other frightening devices. By 

shooting a .22-caliber rifle just over the top of a crop, a 

person on a stand or truck bed can frighten birds from 

fields of 40 acres (16 ha) or more. Obviously, care must be 

taken when shooting in this manner, and the use of limited 

range cartridges is recommended. 

A variety of auditory bird-frightening devices, including electronic high-intensity acoustic systems and tape-recorded 

distress calls for birds occasionally are used to rid fields of 

blackbirds.

Visual

A variety of visual bird-frightening devices, including helium

-filled balloons tethered in fields, radio-controlled model 

planes, reflecting tapes made of Mylar® (Figure 8), and 

various types of animated scarecrows, occasionally are 

used to rid fields of blackbirds. 

U.S. Department of Agriculture Page 5
Auditory-Visual

Pyrotechnics fired from a 12-gauge shotgun (shell 

crackers) or other pistol-type launcher (e.g., bangers and 

screamers) can be effective at frightening blackbirds. 

Shooting birds with a shotgun, using standard non-toxic 

bird shot, can kill a few birds and often reinforce other 

scare devices such as pyrotechnics and propane cannons. 

This technique, however, usually is not as effective in 

moving birds as the other devices that have greater range. 

Thus, a shotgun patrol should not be used as the sole 

means of frightening birds.

Chemical

Avitrol® is an EPA-registered chemical frightening agent 

(active ingredient 4-aminopyridine) for blackbirds and other 

pest birds that previously had labels for use in ripening 

corn and sunflower fields from the 1970s to early 2000s. 

This product is no longer registered for field crops but can 

be used in non-crop areas. The ingestion of one or more 

treated corn particles by a blackbird causes erratic flight, 

distress calls, and usually death. This behavior often 

causes the remaining birds in the flock to leave the area.

Repellents

Various bird repellents using the active ingredient methyl 

anthranilate currently are registered for maturing grain, 

sunflower, or fruit crops. Several seed-treatment repellents 

using anthraquinone or other active ingredients such as 

benzyl diethyl ammonium saccharide have been registered 

to reduce bird damage to freshly planted and sprouting 

corn, rice, and other crops. However, the registration status 

and trademark names of these products often change; 

thus, check with county extension agents or USDA-APHISWildlife Services (WS) biologists for products currently 

registered. Always read the product label and refer to state, 

province, and local restrictions.

Fertility Control

No specific work is being done on fertility control in 

blackbirds.

Toxicants

StarlicideTM is a registered toxicant for blackbirds and 

starlings in feedlot situations. The active ingredient, 3-

chloro-p-toluidine hydrochloride, is incorporated into 

pelletized bait at a concentration of 0.1% and sold 

commercially under the trade name Starlicide Complete®. 

Starlicide Technical® (DRC-1339, 98% active ingredient), 

which can be custom-mixed with livestock feed or other 

bait material, is also available through the USDA-APHIS 

Wildlife Services (WS) Program. Starlicide Technical® can 

be used only by or under supervision of WS employees. 

Starlicide is a slow-acting toxicant; birds usually die 1 to 3 

days after feeding. Baiting programs are most successful in 

winter, especially with snow cover present, when alternate 

foods are scarce. A successful program generally requires 

a period of prebaiting with nontoxic bait to accustom the 

target blackbirds and starlings to feed at specific bait sites 

inaccessible to livestock in the feedlot. Monitoring to 

ensure that nontarget birds such as doves, song birds, and 

barnyard fowl do not feed at bait sites is essential. Check 

the product label for details on use, application, personal 

protection, factors affecting efficacy, and disposal. Always 

read product labels and refer to state, province, and local 

restrictions.

Figure 8. Mylar® reflecting tape strung above the vegetation can reduce 

blackbird feeding activity in agricultural fields such as this millet crop in 

Ohio.

Page 6 WDM Technical Series—Blackbirds
Trapping

Certain species of blackbirds, particularly redwings, brownheaded cowbirds, and common grackles, often can be 

readily trapped in decoy traps. These traps also are effective for starlings. Consult a state wildlife official, such as a 

conservation officer or game warden, before putting a decoy trap into operation. A decoy trap is a large (e.g., 20- x 

20- x 6-foot) poultry wire or net enclosure containing 10 to 

20 decoy birds, food, and water (Figure 9). Birds enter the 

trap through an opening (often 2- x 4-foot) in the top of the 

cage that is covered with 2- x 4-inch welded wire mesh. The 

blackbirds can fold their wings and readily drop through 

the openings to the food below, generally cracked corn, 

millet, or sunflower seeds. A small (e.g., 2- x 2- x 3-foot) 

gathering cage with a sliding door attached to an opening 

at an upper corner of the trap can be used to collect 

trapped birds. A corralling baffle running about two-thirds 

the length of the trap can aid in driving the birds into the 

gathering cage.

A decoy trap often catches 10 to 50 blackbirds and starlings per day and occasionally up to 300 when located 

near a large roost. Obviously, the decoy trap is of questionable value when trying to reduce large roosting populations

and damage to the surrounding agricultural fields. These 

traps, however, can be used to temporarily reduce local 

populations of blackbirds in special situations. For example, decoy traps have been used successfully in an 11-

county area of Michigan since the 1970s to reduce cowbird populations during the nesting season. This control 

was initiated to increase the nesting success of the 

Kirtland’s warbler, an endangered species whose nests 

often are used by cowbirds for laying their own eggs. Each 

year decoy traps in this area of Michigan have captured 

about 3,600 cowbirds. Decoy traps might also be successful in reducing localized populations around feedlots or 

fruit crops. 

Immediately release any nontarget songbirds accidentally 

captured in a decoy trap. Blackbirds to be disposed of 

should be killed humanely. They can be transferred from 

the gathering cage to a cardboard box or canvas-covered 

cage and asphyxiated with carbon dioxide gas. Examine all 

dead birds for bands, and report any bands found to the 

USFWS. 

Shooting

As discussed under Frightening Devices, shooting to kill 

with a shotgun is most effective when used occasionally to 

supplement or reinforce other scare devices. By itself, 

shooting with a shotgun is not cost-effective in frightening 

blackbirds from large agricultural fields, and is totally ineffective as a means of reducing populations. Examine any 

killed birds for bands. It also may be useful to examine the 

stomach contents to determine if the birds are feeding on 

insect pests and weed seeds.

Blackbirds provide some benefits by feeding on harmful 

insects, such as rootworm beetles (Diabrotica spp.) and 

corn earworms (Helicoverpa zea), and on weed seeds, 

such as Johnson grass. Because of their abundance, redwings are a food source for a variety of avian and mammalian predators.

Page 7

Figure 9. A typical blackbird and starling decoy trap showing elevated feed 

platform in center of trap and gathering cage on the far left. Birds enter the 

trap through a 2 x 4-foot (0.6 x 1.2-m) opening covered with 2 x 4-inch (5 x 

10-cm) welded wire located directly above the feed platform.

U.S. Department of Agriculture

Economics
Superficial surveys of agricultural fields often overestimate 

blackbird damage and thus exaggerate the overall severity 

of the economic threat for one of four reasons: (1) the 

conspicuousness of blackbird flocks tends to heighten the 

awareness of bird damage compared with other more 

subtle forms of loss caused by weeds, insects, other pests, 

weather, and harvesting; (2) the eye naturally seeks out 

the conspicuously bird-damaged plants; (3) bird damage is 

often most severe along field edges where an observer is 

most likely to notice; and (4) damage by raccoons, other 

mammals, or wind sometimes is mistaken for bird damage 

(see the section Damage Identification). This is not to 

downgrade the problem of blackbird damage in agriculture; 

damage can be economically severe on occasion and quite 

frustrating to the farmer when relief is not readily available. 

It is important, however, to obtain objective estimates of 

damage levels likely to occur, for only then can someone 

make intelligent decisions regarding the amount of money 

and effort to be invested on control. The final decision on 

control measures must take into account the value of the 

crop, cost of control, and the degree of effectiveness of the 

control measure in relation to the probable levels of 

damage. 

Studies during the past four decades concerning blackbird 

damage to various crops such as corn and sunflower 

indicate that on statewide or regional bases, overall 

average damage is low, generally less than 1% of the crop. 

This may translate into national losses per year of $150 

million combined for corn, sunflower, and rice (at 2012 

prices) but overall, this is a minor loss to the macro 

agricultural economy. If all farmers received less than 1% 

damage, there would be little concern; however, the 

damage is not equally distributed. While most farmers 

escape economically serious damage, a few farmers 

receive serious damage. For example, a bioenergetics 

study of blackbird damage to sunflowers in the northern 

Great Plains indicated an overall loss of sunflower to 

blackbirds was estimated to be only 1.7% of the crop. 

Other studies indicated that about 2% of the fields 

received more than 10% loss. Only in these relatively few 

fields that sustain high levels of damage can control 

measures generally be cost-effective. 

While accurate prediction of damage is often impossible to 

obtain, knowledge of the location of a field in relation to 

traditional roosting sites often provides the basis for a 

sound estimate of potential damage. For example, studies 

of blackbird damage to ripening corn in Ohio and North 

Dakota have revealed that almost all losses exceeding 5% 

of the crop have occurred in fields within 5 miles of 

marshes containing large blackbird roosts in late summer. 

Objective estimates of damage levels in previous years for 

the same or nearby fields are another means of predicting 

future damage levels, because bird damage is fairly 

consistent from year to year within a locality. This 

information also provides a good baseline for evaluating 

the effectiveness of management strategies. Of course, it 

is important that estimates be objective and apply to the 

entire field.

Identification

The term blackbird loosely refers to a diverse group of 

about 10 species of North American birds that belong to 

the avian family Icteridae. The most common species 

include: 

 Red-winged blackbird (Agelaius phoeniceus)

 Common grackle (Quiscalus quiscula)

 Great-tailed grackle (Quiscalus mexicanus)

 Brown-headed cowbird (Molothrus ater)

 Yellow-headed blackbird (Xanthocephalus 

xanthocephalus)

 Brewer’s blackbird (Euphagus cyanocephalus)

 Rusty blackbird (Euphagus carolinus)

In addition to blackbirds, this family includes orioles, 

meadowlarks, and bobolinks. 

Page 8

Species Overview

WDM Technical Series—Blackbirds
Physical Description

The various species of blackbirds have several traits in 

common. Males are predominantly black or iridescent in 

color. The male red-winged blackbird is a little smaller than 

an American robin and is black with red and yellow shoulder patches (Figure 1). The smaller female is brownish, 

resembling a large sparrow. The common grackle is an 

iridescent blackbird slightly larger than a robin with a long 

keel-shaped tail. The male, slightly larger than the female, 

has more iridescence on the head and throat. The greattailed grackle is similar to the common grackle but with a 

much larger tail. The male is slightly smaller than an American crow (Corvus brachyrhynchos); the female is smaller 

and browner than the male. The brown-headed cowbird is 

the smallest blackbird. The male is black with a brown 

head and the female is brown (Figure 10). Both sexes have 

finch-like bills. 

The yellow-headed blackbird is a robin-sized bird. The male 

has a striking appearance with a black body, conspicuous 

yellow head and breast, and a white wing patch in flight. 

The female is smaller and browner, with a yellowish throat 

and breast. The Brewer’s blackbird is a robin-sized bird. 

The male is all black with whitish eyes and the female is 

brownish gray with dark eyes. The rusty blackbird is similar 

to Brewer’s blackbird, but its fall and winter plumage has a 

rusty coloration.

Range

The red-winged blackbird is an abundant nester throughout 

much of North America and winters throughout the southern United States. The common grackle is a common nester throughout North America east of the Rockies and winters in the southern U.S., often in association with other 

blackbird species and starlings. The great-tailed grackle is 

an abundant year-round resident in the southwestern U.S. 

(especially Texas) and Mexico. In recent years, great-tailed 

grackles have expanded their range northward into the 

central Great Plains where they gather in feedlots and dairies in winter. Cowbirds originally were a species of the 

Great Plains associated with bison, but with the clearing of 

forests for agriculture, now occur in spring and summer 

throughout much of North America. Cowbirds spend winters in the central to southern U.S., often roosting with other blackbird species and starlings. Yellow-headed blackbirds are locally abundant nesters in deep-water marshes 

of the northern Great Plains and western North America. 

They spend winter farther south than other blackbirds, primarily in Mexico. Brewer’s blackbirds are common in the 

northern Great Plains and western North America. It is a 

winter migrant in the central and southern Plains states, 

sometimes roosting with other blackbird species. Rusty 

blackbirds occupy Canada, Alaska, and northern New England and Michigan. They migrate in winter to the southern 

U.S. from the Atlantic coast to east Texas. (See Appendix 2 

for range maps) 

Sign

Blackbirds are most often noticed by their visual appearance and by their congregations into large flocks outside of 

the nesting season. For sign associated with agricultural 

damage, see the section on Damage Identification.

Voice and Sounds

Each blackbird species has distinctive vocalizations that 

are easily recognizable with a little practice. The sounds 

made when large numbers of blackbirds are entering 

nighttime roosts can be quite cacophonous. 

Page 9

Figure 10. The brown–headed cowbird (Molothrus ater), the smallest of the 

blackbirds, often feeds in close association with livestock. The female 

cowbird (above) lays her eggs in the nests of other birds

U.S. Department of Agriculture
Reproduction

Blackbirds and grackles mature in 1 year. Nesting typically 

occurs from April to July. Females have 3 to 5 eggs in their 

open-cup nests made of grasses and other vegetation. 

Eggs hatch after about 12 days of incubation; the young 

grow rapidly and are ready to fledge about 10 days later. 

Females often will renest if their initial nest is destroyed. 

Their high mortality rate is offset by a reproductive rate of 2 

to 5 young fledged per female per year.

Cowbirds do not build nests or incubate eggs; females lay 

their eggs in nests of other songbirds. They are the only 

North American songbird to do so. Females deposit 1 or 

sometimes 2 eggs per host nest, laying up to 25 or more 

eggs per nesting season. The cowbird nestlings usually outcompete other nestlings for food, crowding them out of the 

nest. 

Mortality

The annual survival rate of blackbirds and grackles is 

about 50-60% for adults (1 year or older) and even less for 

first-year birds. 

Because of their abundance, blackbirds are an important 

food source for a variety of mammalian and avian 

predators. Predation, exposure to inclement weather, and 

flying into wires and other structures are all important 

sources of mortality. 

Population Status

The red-winged blackbird is one of the most abundant 

birds in North America. In July, after the young have 

fledged from nests, the continental population exceeds 

300 million birds. The common grackle is the second most 

abundant blackbird, with a population approaching 200 

million in mid-summer. Most of the other blackbird species, 

although not as common as the redwing or grackle, all 

have abundant healthy populations. Exceptions are the 

rusty blackbird and the tricolored blackbird (Agelaius 

tricolor), a species similar in appearance and behavior to 

red-winged blackbirds that has a restricted range in 

California.

The population of rusty blackbirds has declined by as much 

as 90% from 1966 to 2013 (based on Breeding Bird 

Survey data). The reason for this decline is not clear but 

some authors suggest habitat degradation as the root 

cause.

Habitat

Red-winged blackbirds nest in diverse habitats of marshes, 

hayfields, ditches, and hedge rows. Large flocks feed in 

fields and bottomlands. Common grackles nest in small 

colonies in shelterbelts (especially evergreens such as 

spruces), farmyards, marshes, and towns. Flocks feed in 

fields, lawns, woodlots, and bottomlands. Common 

grackles often roost with redwings, but are partial to 

roosting sites in upland deciduous or pine trees. Greattailed grackles nest in colonies in shrubs and trees, 

sometimes in association with herons and egrets. The 

flocks feed around farms, pastures, and parks. In winter, 

great-tailed grackles gather in nighttime roosts in live oaks 

and other dense vegetation. 

Cowbirds deposit eggs in the nests of other birds. They 

feed as flocks in pastures, feedlots, and lawns, and often 

are associated with livestock. Yellow-headed blackbirds 

nest in emergent vegetation over marshes and other 

wetlands. They feed in agricultural fields, meadows, and 

pastures during late summer and fall, sometimes in 

association with redwings or other blackbirds. 

Brewer’s blackbirds nest in in colonies in a variety of 

habitats. They feed in flocks on waste grain and weed 

seeds in agricultural lands, pastures, and lawns. Rusty 

blackbirds nest in northern swamps, bogs, and muskeg 

throughout Canada, Alaska, northern New England, and 

Michigan. They often feed on insects in a variety of 

habitats. During winter, rusty blackbirds prefer swampy 

areas and river bottoms in the southern U.S. They often 

roost with other species of blackbirds. 

Behavior

Outside of the nesting season, blackbirds generally feed in 

flocks and roost at night in congregations varying from a 

few birds to several million birds (Figures 4, 11). These 

Page 10 WDM Technical Series—Blackbirds
flocks and roosting congregations sometimes consist of a 

single species, but often several species intermingle. 

Sometimes non-blackbird species, notably European starlings and American robins, join them. The flocks will forage 

during the day up to 30 miles from the nighttime roost location.

Redwings, common grackles, and cowbirds generally migrate from Canada and the northern U.S in October to November, spending the winter in the southern U.S. Yellowheaded blackbirds are early migrants, departing the northern Great Plains by September, although flocks numbering 

several hundred can be found feeding in North Dakota in 

late September.

Food Habits

All blackbirds have an omnivorous diet consisting primarily 

of grains, weed seeds, fruits, and insects. The relative proportions of these food groups, however, vary considerably 

among species and even between sexes within a species. 

Red-winged blackbirds feed primarily on insects during the 

nesting season (May through July), with the diet shifting 

predominantly to grain and weed seeds in late summer 

through winter. Males and females often forage in separate flocks, with females more insectivorous than males. 

The common grackle’s diet is similar to that of the redwing, 

but the grackle is more predatory. Its diet occasionally includes small fish, field mice, songbird nestlings, and eggs. 

Grackles have a larger, stronger bill than redwings, allowing them to crack open and feed on acorns and other tree 

fruits in winter. Great-tailed grackles are omnivorous: their 

diet includes insects, aquatic organisms, eggs from nesting 

birds, fruits, and grains. The diet of cowbirds consists predominantly of weed seeds and grains, and less than 25% 

insects. The diet of yellow-headed blackbirds is similar to 

that of redwings; yellowheads primarily eat insects during 

the nesting season and grains and weed seeds at other 

times. Brewer’s blackbirds eat about two-thirds grain and 

weed seeds and one-third insects and other animal matter. 

The diet of rusty blackbirds contains more insects than 

that of other blackbirds. Over 50% of their food is animal 

matter. Grain (gleaned from harvested fields in fall and 

winter), weed seeds, and tree fruits also are eaten. 

Blackbirds are native migratory birds, and thus come under 

the jurisdiction of the Federal Migratory Bird Treaty Act 

(MBTA), a formal treaty with Canada, Mexico, Japan, and 

Russia. Blackbirds have federal protection in the U.S. Most 

species of blackbirds may be killed under the Depredation 

Order for Blackbirds, Cowbirds, Grackles, Crows, and Magpies (50 CFR 21.43), but only 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.” In 2010, rusty blackbirds 

were removed from the Depredation Order and given full 

protection by the MBTA as has always been the case for 

the tricolored blackbird. Other revisions include that nontoxic shot must be used when taking birds by shotgun under the authority of CFR 21.43. Also, at the end of each 

calendar year anyone taking blackbirds under CFR 21.43 

must provide the US Fish and Wildlife Service (USFWS) the 

following information: name and address of taker, species 

and number taken, month when birds were taken, state 

and county where birds were taken, and a general explanation of why the birds were taken. 

Page 11

Figure 11. A flock of over 2,000 red-winged blackbirds descends into a 

sunflower field in North Dakota to feed on the ripening seeds.

Legal Status

U.S. Department of Agriculture
Page 12

Acknowledgements

Figure 1. Photo by G.M. Forcey

Figure 2. Photo by J.F. Glahn, USDA

Figure 3. Photo by R.A. Dolbeer, USDA-APHIS-WS 

Figure 4. Photo by S.R. Stopack, USDA-APHIS-WS 

Figure 5. Photos by R.A. Dolbeer, USDA

Figure 6. Photo by G.M. Linz USDA-APHIS-WS, NWRC

Figure 7. Photo by R.A. Dolbeer, USDA-APHIS-WS 

Figure 8. Photo by R.A. Dolbeer, USDA-APHIS-WS 

Figure 9. Photo by R.A. Dolbeer, USDA-APHIS-WS 

Figure 10. Photo by Alan Schmierer, FLICKR Commons

Figure 11. Photo by North Dakota State University

We thank Phil Mastrangelo, USDA, for providing a critical review of this manuscript. 

Glossary

Blackbird: A group of new world bird species in the family 

Icteridae, not to be confused with the Eurasian blackbird 

(Turdus merula), which is a thrush related to the American 

robin. 

Nesting season: The time of year, typically from April to 

early July, when blackbirds build nests (except for cowbirds), lay eggs and raise young to fledging. 

Roost: A site of dense vegetation (trees, cattails, brush) 

where blackbirds gather at dusk to spend the night. Blackbirds typically gather in roosts during all seasons outside 

the nesting season. 

Key Words

Agelaius phoeniceus, blackbird, cowbird, crop damage, 

grackle, Molothrus ater, Quiscalus mexicanus, Quiscalus 

quiscula, redwing, red-winged blackbird, roost, starling, 

Sturnus vulgaris

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. 

WDM Technical Series—Blackbirds

Some states and municipalities have additional restrictions 

on the killing of blackbirds. European starlings, which often 

associate with blackbirds during winter, are an introduced 

species in North America and are not protected by the 

MBTA.
Page 13

Resources

Bent, A. C. 1965. Life histories of North American Blackbirds, Orioles, Tanagers, and Allies. Dover Publications, Inc., New York. 549 pages and 37 plates. 

Birds of North America series (detailed life history accounts of all blackbird species) at http://

bna.birds.cornell.edu/bna/species

Dolbeer, R. A. 1981. Cost-benefit determination of blackbird damage control for cornfields. Wildlife Society 

Bulletin 9:43-50. 

Dolbeer, R. A. 1990. Ornithology and integrated pest management: the red-winged blackbird (Agelaius 

phoeniceus). Ibis 132:309-322. 

Dunning, J. B., Jr. (Editor). 2007. CRC handbook of avian body masses. CRC Press. Boca Raton, Florida, 

USA.

Hagy, H., J. Raetzman, G. Linz, and W. Bleier. 2005. Decoy cropping methods for luring blackbirds away 

from commercial sunflower: USDA wildlife conservation sunflower plots. Proceedings of the Wildlife Damage Management Conference 11:304-310. 

Johnson, D. B., F. S. Guthery, and N. E. Koerth. 1989. Grackle damage to grapefruit in the lower Rio 

Grande Valley. Wildlife Society Bulletin 17 (1):46-50.

Linz, G. M., and H. J. Homan. 2011. Use of glyphosate for managing invasive cattail (Typha spp.) to disperse blackbird (Icteridae) roosts. Crop Protection 30:98-104. 

Linz, G. M., H. J. Homan, S. J. Werner, H. M. Hagy, and W. J. Bleier. 2011. Assessment of bird-management 

strategies to protect sunflowers. BioScience 61:960-970. 

Peer, B. D., H. J. Homan, G. M. Linz, and W. J. Bleier. 2003. Impact of blackbird damage to sunflower: bioenergetic and economic models. Ecological Applications 13:248-256.

Robbins, C. S., B. Bruun, and H. S. Zim. 1983. Birds of North America: A Guide to Field Identification. Golden Press, New York. 360 pages. 

White, S. B., R. A. Dolbeer, and T. A. Bookhout. 1985. Ecology, bioenergetics, and agricultural impact of a 

winter-roosting population of blackbirds and starlings. Wildlife Monograph 93. 42 pages. 

Wilson, E. A., E. A. LeBoeuf, K. M. Weaver, and D. J. LeBlanc. 1989. Delayed seeding for reducing blackbird 

damage to sprouting rice in southwestern Louisiana. Wildlife Society Bulletin 17:165-171.

Internet Center for Wildlife Damage Management (http://icwdm.org)

National Wildlife Control Training Program (http://wildlifecontroltraining.com)

U.S. Department of Agriculture
Damage Prevention and Control Methods for Blackbirds

Type of Crop Damage 

Method of 

Control 

Sprouting corn 

and rice 

Ripening corn, 

sorghum and 

sunflower 

Ripening rice and 

oats 

Fruit crops Feedlots 

Exclusion Generally not 

practical; netting 

for small plots

Generally not 

practical; netting 

for small plots; 

paper bags over 

ears/heads

Generally not 

practical; netting 

for small plots

Netting is cost 

effective for highvalue crops

Various techniques

Cultural methods Deep planting; 

avoid early planting 

of rice

Grow nonpreferred 

crops near roosts; 

provide alternative 

feeding sites; avoid 

early/late planting; 

use resistant 

hybrids; harvest as 

early as possible

Same as for 

ripening corn; 

resistant hybrids 

not available

Provide alternative 

feeding sites; early 

harvest

N/A

Frightening Numerous devices 

available; must be 

varied to minimize 

habituation

Numerous devices 

available; must be 

varied to minimize 

habituation

Numerous devices 

available; must be 

varied to minimize 

habituation

Numerous devices 

available; must be 

varied to minimize 

habituation

Numerous devices 

available; must be 

varied to minimize 

habituation

Chemical 

repellents

Registered seed 

treatments may be 

available 

Registered 

products may be 

available 

Registered 

products may be 

available 

Registered 

products may be 

available 

Registered 

products may be 

available 

Toxicants None available None available None available None available Starlicide

Trapping Generally not 

practical

Generally not 

practical

Generally not 

practical

Decoy traps Decoy traps

Shooting Helpful to reinforce 

frightening devices; 

futile for 

population 

reduction

Helpful to reinforce 

frightening devices; 

futile for 

population 

reduction

Helpful to reinforce 

frightening devices; 

futile for 

population 

reduction

Helpful to reinforce 

frightening devices; 

futile for 

population 

reduction

Helpful to reinforce 

frightening devices; 

futile for 

population 

reduction

Page 14

Appendix 1
Appendix 2

Range Maps of Common Blackbird Species. Map by Cornell Lab of Ornithology. Data by NatureServe.

Page 15
Characteristics of Selected Blackbird Species

Photo Name Size 

(Dunning 2007) 

Feeding and 

habitat 

Conflicts with humans 

Brewer’s 

blackbird 

(Euphagus 

cyanocephalus) 

Male = 67 grams

Female = 58 grams

Consumes large numbers of 

harmful insects during the 

summer months. Flocks feed in 

pastures and feedlots, and often 

are associated with livestock.

Causes generally minor damage to 

oats, fruit crops, and livestock 

feed. 

Brown-headed 

cowbird 

(Molothrus ater)

Male = 49 grams

Female = 38 grams

Eats weed seeds and grains. 

Insects are < 25% of diet. Female 

lays eggs in nests of other 

songbirds, the only North 

American songbird to do so. Often 

roosts with red-winged blackbirds, 

grackles, and European starlings.

Damages sprouting rice; ripening 

sorghum, sunflower, and millet. 

Eats some livestock feed; gleans 

waste grain and seed from dung. 

Parasitizes nests of some 

endangered species. Winter roosts 

in urban areas cause disease and 

nuisance concerns. 

Common grackle 

(Quiscalus 

quiscula)

Male = 120 grams

Female = 92 grams

Omnivorous; feeds on acorns, 

insects, frogs, fish, and seeds. 

Prefers fields, lawns, woodlots, 

and bottomlands. Often roosts 

with red-winged blackbirds, 

brown-headed cowbirds, and 

European starlings. 

Similar to damage by red-winged 

blackbirds, but will feed on corn in 

the dent stage, removing entire 

kernels. Also, grackles will pull up 

sprouting corn. Winter roosts in 

urban areas cause disease and 

nuisance concerns.

Great-tailed 

grackle 

(Quiscalus 

mexicanus) 

Male = 222 grams

Female = 116 grams

Omnivorous; feeds on insects, 

aquatic organisms, eggs from 

nesting birds, fruits, and grains on 

farms, pastures, and parks. Nests 

in colonies in shrubs or trees, 

sometimes in association with 

herons and egrets. 

Damages fruits and melons, 

although the loss is generally 

minor. They will peck citrus fruit 

skin, creating blemishes or holes.

Rusty blackbird 

(Euphagus 

carolinus)

Male = 64 grams

Female = 55 grams

More insectivorous than other 

blackbirds. Over 50% of their food 

is animal matter. Grain (gleaned 

from harvested fields), weed 

seeds, and tree fruits also are 

eaten. They prefer swampy areas 

and river bottoms. 

This species does little damage to 

crops.. Population is declining and 

a specific depredation permit is 

required to take Rusty blackbirds. 

Roosts in small numbers with other 

blackbirds and European starlings 

in winter. 

Red-winged 

blackbird 

(Agelaius 

phoeniceus)

Male = 65 grams

Female = 40 grams

Eats primarily weed seeds and 

grains. Females feed on more 

insects than males. Nests in 

cattails in marshes and ditches, 

but also in upland hay fields and 

brush. Often roosts with cowbirds, 

grackles, and European starlings. 

Damages sprouting rice; ripening 

corn, sunflower, rice, and other 

grain crops. Winter roosts in urban 

areas cause disease and nuisance 

concerns. 

Yellow-headed 

blackbird 

(Xanthocephalus 

xanthocephalus) 

Male = 80 grams

Female = 50 grams

Feeds in agricultural fields, 

meadows, and pastures during 

late summer and fall, sometimes 

with red-winged blackbirds or 

other blackbirds. Nests in deepwater marshes. 

Causes generally minor damage to 

ripening corn, sunflower, and oats, 

often in association with redwinged blackbirds. 

Dave Menke

Alan D. Wilson

Thomas G. Barnes

John and Karen 

Hollingsworth

Dave Menke

Dave Menke

G.M. Forcey

Page 16

Appendix 3