Controlling Blackbird Damage

to Sunflower and Grain Crops

in the Northern Great Plains

United States

Department of

Agriculture

Animal and

Plant Health

Inspection

Service

Agriculture

Information

Bulletin No. 679
2

Cover photo: Flocks of red-winged blackbirds, sometimes numbering in the tens of

thousands, can destroy a grain field in a few

days. (APHIS photo by David Bergman.)

The U.S. Department of Agriculture (USDA)

prohibits discrimination in its programs on the

basis of race, color, national origin, sex,

religion, disability, political beliefs, and marital

or familial status. (Not all prohibited bases

apply to all programs.) Persons with

disabilities who require alternative means for

communication of program information

(Braille, large print, audiotape, etc.) should

contact the USDA's TARGET Center at (202)

720–2600 (voice and TDD).

To file a complaint, write the Secretary of

Agriculture, U.S. Department of Agriculture,

Washington, DC 20250, or call (800) 245–

6340 (voice) or (202) 720–1127 (TDD).

USDA is an equal employment opportunity

employer.

Mention of companies or commercial

products does not imply recommendation or

endorsement by USDA over others not

mentioned. USDA neither guarantees nor

warrants the standards of any product

mentioned. Product names are mentioned

solely to report factually on available data

and to provide specific information.

This publication reports research involving

pesticides. All uses of pesticides must be

registered by appropriate State and/or

Federal agencies before they can be

recommended.

CAUTION: Pesticides can be injurious to

humans, domestic animals, desirable plants,

and fish or other wildlife—if they are not

handled or applied properly. Use all

pesticides selectively and carefully. Follow

recommended practices for the disposal of

surplus pesticides and pesticide containers.
3

United States

Department of

Agriculture

Animal and

Plant Health

Inspection

Service

Agriculture

Information

Bulletin No. 679

Issued

December 1993

Slightly revised

August 1997

1

George Linz and Richard Dolbeer work for the Denver Wildlife Research Center,

a unit of the Animal and Plant Health Inspection Service (APHIS), Animal

Damage Control program, in Fargo, ND, and Sandusky, OH, respectively.

James Hanzel is with North Dakota State University’s Crop and Weed Sciences

Department, in Fargo, ND. Louis Huffman is with APHIS, Animal Damage

Control, in Bismarck, ND.

Controlling Blackbird Damage

to Sunflower and Grain Crops

in the Northern Great Plains

By George M. Linz, Richard A. Dolbeer,

James J. Hanzel, and Louis E. Huffman1
4
5

Red-winged blackbirds (Agelaius

phoeniceus), common grackles

(Quiscalus quiscula), and yellow-headed

blackbirds (Xanthocephalus

xanthocephalus) cause severe damage

to ripening crops in North Dakota, South

Dakota, and Minnesota. Scientific surveys show that blackbirds damage $4

million to $11 million worth of sunflower

each year in these three States. On

occasion, blackbirds have destroyed

entire fields of sunflower in a few days.

Preventing this magnitude of crop damage requires knowledge about the

blackbird’s habits and various methods

available to prevent damage.

In late summer, after the nesting season, blackbirds form flocks and roost at

night in numbers varying from a few to

over a million birds. These flocks and

roosting congregations are sometimes

comprised of a single species, but often

all three species mix together. Although

some blackbirds roost in trees in the

northern Great Plains, the birds prefer to

roost in dense cattail marshes. Between

40 and 50 percent of the blackbird population dies every year. But these mortality figures are offset by the birds’

Introduction

Blackbirds often use alternate feeding sites when available. (APHIS photo by

George Linz.)
6

reproductive success. On average, a

female produces two to four fledglings

per year. The three common blackbird

species have many differences in their

nesting biology, food preferences, feeding habitats, and migration patterns.

Red-Winged Blackbird

Red-winged blackbirds are the most

numerous breeding blackbird in the

Dakotas and Minnesota and perhaps

the most abundant bird in North

America. The male, a little smaller than

a robin, is black with red and yellow

shoulder patches. The brownish

female, which is smaller than the male,

is often mistaken for a large sparrow.

Redwings nest throughout North

America in marshes, hayfields, and

ditches. Often adult males mate with

more than one female. Insects are the

dominant food during the nesting season (May–July), with the diet shifting to

predominantly grain crops and weed

seeds in late summer through winter.

Redwings from the Dakotas and Minnesota migrate to the lower Great Plains

and gulf coast region in winter. Red-winged blackbird (immature male) on an ear of corn. (Photo courtesy of the

U.S. Department of the Interior, Fish and Wildlife Service.)
7

Common Grackle

Common grackles are slightly larger

than robins, with iridescent black feathers and a long keel-shaped tail. The

male, slightly larger than the female, has

more iridescence on the head and

throat. Grackles are common nesters

throughout North America east of the

Rockies, nesting in shelterbelts, farmyards, marshes, and towns. The male

grackle usually mates with one female.

Flocks feed in fields, lawns, woodlots,

Common grackle (mature male). (USDI, Fish

and Wildlife Service, photo by Roger Clopp.)

Winter range of red-winged blackbirds, yellow-headed blackbirds, and common

grackles breeding in the northern Great Plains.

Breeding range of 

blackbirds

Winter range: 

red-winged blackbirds, 

common grackles

Winter range: 

yellow-headed 

blackbirds

Winter migration

routes

Red-winged blackbirds

and common grackles

Yellow-headed

blackbirds
8

and bottomlands. Grackles have a diet

somewhat similar to that of redwings,

but grackles are more predatory, feeding occasionally on small fish, field mice,

songbird nestlings, and eggs. Grackles

also feed on acorns and other tree fruits

in winter. Grackles often roost in cattail

marshes with other blackbirds in late

summer, but grackles prefer roosting

sites in upland deciduous or pine trees

in their wintering locations in the Southern United States.

Yellow-Headed Blackbird

A robin-sized bird, the male

yellowhead has a black body with a conspicuous yellow head and breast and a

white wing patch seen only when the

bird is in flight. The female is smaller

and browner with yellow throat and

breast and does not have a white wing

patch. Yellowheads are locally abundant nesters in deep-water marshes of

the northern Great Plains and western

North America. Like redwings, male

yellowheads often mate with more than

one female. This species feeds extensively on insects during the nesting season and in late summer and fall on weed

Other Bird Species

Other birds are sometimes seen

feeding with redwings, yellowheads,

and grackles but cause only minor damage to agricultural crops. The brownheaded cowbird (Molothrus ater) is a

small, sparrow-sized blackbird. The

male is black with a brown head, and

the female is gray. Cowbirds feed primarily on weed seeds and insects, often

in association with grazing livestock.

The European starling (Sturnus vulgaris)

is robin sized and is dark with light

speckles and a distinctively short tail.

Although starlings sometimes forage in

grain and sunflower crops, these birds

are usually searching for insects and do

not feed on the crop. However, starlings

will damage ripening fruit crops. House

sparrows (Passer domesticus) are small

brown birds sometimes mistaken for

female redwings. House sparrows can

cause significant local damage to small

grain crops and sunflower grown near

farmsteads and towns. Rusty blackbirds

(Euphagus carolinus) are robin sized

and can be recognized in fall and winter

by their rust-colored plumage. Their diet

consists largely of insects. Brewer’s

seeds, sunflower, corn, and small

grains, often in association with redwings and grackles. An early migrant,

yellowheads leave the northern Great

Plains area before redwings and grackles, wintering in Mexico.

Yellow-headed blackbird (mature male).

(USDI, Fish and Wildlife Service, photo by

James Leupold.)
9

blackbirds (Euphagus cyanocephalus)

are similar in size to male redwings.

Males are black with whitish eyes;

females are brownish gray with dark

eyes. These birds feed primarily on

weed seeds and insects.

Legal Status

Blackbirds are native migratory birds

and thus come under the jurisdiction of

the Federal Migratory Bird Treaty Act, a

formal treaty with Canada and Mexico.

Blackbirds are protected by Federal law

(Title 50, Code of Federal Regulations,

Part 21.43) in the United States except

that they may be killed 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.” Some States

and local governments may have additional restrictions on killing blackbirds.

Starlings and house sparrows were

introduced from Europe and are not protected by Federal law.

Blackbird damage to agricultural crops

is readily discernible because flocks of

birds are conspicuous and signs of damage are obvious. However, superficial

surveys of agricultural fields often overestimate blackbird damage and thus

exaggerate the overall severity of the

economic threat for four reasons: (1) the

high visibility 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, and harvesting; (2) observers

naturally seek out the conspicuously

bird-damaged plants; (3) bird damage is

often most severe along field edges,

where an observer is most likely to

check; and (4) damage caused by other

animals such as raccoon and deer or by

wind is sometimes mistaken for bird

damage.

Damage to sunflower and grain crops

can be economically severe and quite

frustrating to the farmer when relief is

not easily available. During the past two

decades, studies on blackbird damage

to various crops such as corn and sunflower indicate that on statewide or

regional level, overall damage is low,

Estimating Crop Damage

generally 1 to 2 percent of the crop. If

all farmers lost less than 2 percent of

their crops, there would be little concern;

however, the damage is not equally distributed. While most farmers escape

economically serious blackbird damage

(that which affects more than 5 percent

of their crops), profit margins for other

farmers are significantly reduced. Some

growers would like to plant sunflower in

their crop rotation, but the threat of bird

depredation precludes this option.

Farmers whose crops are seriously

damaged by blackbirds may find various

damage control measures cost effective.

It is important to obtain objective estimates of potential damage levels in a

field before investing large amounts of

money on control. The person making

the final decision on control measures

must consider the value of the crop, the

cost of control, and the degree of effectiveness of the control measure in relation to the probable levels of damage.

Estimates of damage levels in previous

years for the same or nearby fields are

another means of predicting future damage levels because local bird damage is

often fairly consistent from year to year.
10

This information also provides a good

baseline for evaluating the effectiveness

of management strategies. Of course, it

is important that estimates of damage

be objective and reflect the entire field,

not just a small portion of the field that

has high damage.

To estimate the amount of blackbird

damage in an agricultural field objectively, at least 10 locations widely

spaced throughout the field should be

examined. For example, if a field has

100 rows and is 1,000 feet long, the

estimator should walk staggered

distances of 100 feet along every 10th

row (for example, 0–100 feet in row 10,

101–200 feet in row 20, and so on). In

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

visually estimate the damage on the

head or ear of each plant to the nearest

1 percent (for example, 2 percent

destroyed, 20 percent destroyed). For

corn, six kernels usually represent about

1 percent of the corn on an ear; for sunflowers, it may be easiest to visually

divide the head into four quarters and

then estimate the percentage of seed

missing. When finished, determine the

average damage for the 100 plants

examined, and this will give an approximation of the percentage loss to the

field. Multiplying the percentage loss

by expected yield can give a rough

estimate of yield lost. In small grains,

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.

Control Methods

Cultural Practices

Most economically severe blackbird

damage to agricultural crops occurs in

fields within 5 miles of roosts. Thus,

one strategy is to plant crops that do not

attract blackbirds—such as soybeans,

potatoes, or hay—in fields that are

within a few miles of a roost. If crops

vulnerable to damage, such as corn or

sunflower, are planted near a roost, it is

important that sources of alternative

food be available to reduce the feeding

pressure on these cash crops. When

crops are ripening, one strategy for providing alternative feeding areas is to

delay plowing or tilling previously harvested cropland near the roost. Also,

farmers should synchronize planting of

fields of vulnerable crops near roosts so

that all fields mature at about the same

time. In general, as the number of suitable alternative feeding areas declines,

maturing grain or sunflower fields

become more attractive to blackbirds,

and protecting the crop becomes more

difficult.

The timing of harvest can be very

important for reducing damage to crops

from flocks of blackbirds. Although field
11

corn generally becomes unattractive to

birds when the kernels mature and

harden, sunflowers continue to be

attractive after they mature and thus

should be harvested as soon as possible. Sweet corn should be harvested

as early as possible in areas with extensive damage. Delaying harvest of sweet

corn by only 1 or 2 days can result in

substantially greater damage if flocks of

blackbirds are in the area.

Bird-Resistant Crops

Planting crop varieties known to be

resistant to blackbird feeding should be

part of a grower’s bird-damage management plan. Bird-resistant sunflower

hybrids may soon be available from

commercial seed companies for use in

areas subject to a high risk of depredation. The seed of these hybrids is protected by morphological traits, such as

concave-shaped heads, horizontally oriented heads, and long head-to-stem distance. These traits make it difficult for

birds to position themselves on the plant

so they can extract seeds from the

head. These hybrids must be planted in

north–south rows to maximize their birdresistant characteristics.

Cattail Marsh Management

Cattail marshes used as roost sites

for blackbirds can be sprayed with

glyphosate (®Rodeo Aquatic Plant Herbicide) to reduce the density of the cattails, which reduction in turn disperses

the birds. Rodeo is the only herbicide

registered for controlling cattails growing

in standing water. (Other herbicides are

available for use on cattails growing in

marshes without surface water.) Generally, cattails must be treated 1 year

Corn hybrids vary greatly in their susceptibility to bird feeding. Hybrids of

corn with long husk extension and thick

husks have been shown to be more

resistant to damage than other hybrids.

Sweet corn is vulnerable to blackbirds

for only a few days before harvest and,

thus, may be easier to protect than field

corn and sunflower.

Sunflowers with concave heads, horizontally

oriented heads, and long head-to-stem

distance appear to suffer less damage from

birds than other varieties. (Photo courtesy of

North Dakota State University; used by

permission.)

Cattail marshes can be managed using a

registered aquatic herbicide to disperse

roosting blackbirds. (APHIS photo by David

Bergman.)
12

before vulnerable crops are planted in

the vicinity of the marsh to allow time for

the cattails to decompose, making the

marsh unattractive to blackbirds for

roosting for several years. For maximum effectiveness, the herbicide should

be aerially applied at a rate of

4.5 pints/acre in August up to first frost.

Sufficient cattails should be removed to

create at least 70 percent open water in

the marsh. Thinning out cattails in these

marshes reduces blackbird use and

improves the habitat for other, more

desirable wildlife, such as waterfowl.

For more detailed information about

managing cattail marshes in the Dakotas,

you may contact:

USDA, APHIS

Animal Damage Control (ADC)

Bismarck, ND (701 250–4405)

Pierre, SD (605 224–8692)

or

U.S. Department of the Interior

 (USDI)

Fish and Wildlife Service

Wetland Habitat Office

Bismarck, ND (701 250–4403)

Frightening

Frightening devices can be effective

in protecting crops from flocks of blackbirds but require considerable work and

long hours. The efficient use of these

devices mandates that farmers persistently scare the birds before their feeding patterns become well established.

Devices need to be employed especially in the early morning and in late

A propane exploder and a popup scarecrow powered by carbon dioxide.

(APHIS photo by John Cummings.)
13

afternoon, when the birds are most

actively feeding.

Propane exploders are a popular

frightening device. In general, there

should be at least 1 exploder for every

10 acres of crop to be protected.

Exploders should be elevated on a barrel stand to “shoot” over the crop, and

they should be moved around the field

every few days. Exploders should be

turned off (manually or with automatic

timers) each night to save propane and

reduce objectionable noise levels. In

addition, exploders should be reinforced

occasionally with other scare devices

because birds lose their fear of frightening devices over time.

By shooting a .22-caliber rifle just

over the top of the crop, a person on a

stand or truck bed can frighten birds

from large fields (40 acres or more).

Obviously, care must be taken when

shooting in this manner, and the use of

limited-range cartridges is recommended. Also effective are pyrotechnic

devices such as cracker shells, bird

bangers, and screamers. These pyrotechnic devices, fired from shotguns or

specially designed pistols, explode after

traveling up to 150 yards. Shooting

birds with a shotgun, using standard bird

shot, often can kill a few birds and reinforce other scare devices. However,

this technique 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.

A variety of other bird-frightening

devices, including electronic noise systems, helium-filled balloons tethered in

fields, radio-controlled model planes,

tape-recorded distress calls for birds,

and various types of scarecrows, are

also occasionally used to rid fields of

blackbirds. The effectiveness of these

devices is highly variable and depends

on the persistence of the operator, the

skill used in employing them, the attractiveness of the crop, and the number of

birds and availability of alternative food

sources. As mentioned with the use of

propane exploders, birds tend to adjust

or adapt to frightening devices. It is

usually best to mix the use of two or

more devices rather than to rely on a

single device.

Airplane Hazing

Harassing feeding blackbirds with an

airplane can sometimes be an effective

method of chasing flocks from sunflower

fields. This technique appears to be

most effective if combined with other

mechanical methods on the ground,

such as shotguns or pyrotechnics.

Airplanes can be used to scare blackbirds.

(APHIS photo by David Bergman.)
14

Repellants

®Avitrol, the only chemical registered

for control of blackbirds in corn and sunflower, is a cracked-corn bait in which 1

out of every 100 particles is treated with

the active ingredient, 4-aminopyridine.

The bait is applied by airplane along

access lanes placed in the fields, at the

rate of 3 pounds/acre. When a blackbird eats one or more treated particles, it

flies erratically and emits distress calls.

This abnormal behavior often causes

the remaining birds in the flock to leave

the field.

Careful consideration must be given

to the timing of initial and repeat

baitings. The first baiting should be

when birds first initiate damage, and

repeat baitings should occur as necessary, about 5 to 7 days apart. Weeds

that hide bait, ground insects (e.g.,

crickets) that eat bait, and excessive

rainfall can contribute toward making the

product less effective. Instructions on

the label, especially the avoidance of

baiting field edges, should be carefully

followed to avoid killing nontarget birds.

Summary

Although red-winged blackbirds, yellowheaded blackbirds, and common grackles significantly damage agricultural

crops in the northern Great Plains,

superficial surveys of fields sometimes

overestimate damage and lead to

unnecessary expenditures on blackbird

control. If significant damage is likely to

occur in a field, an integrated pest management approach is most effective in

protecting crops from blackbirds. To

reduce crop losses, individual growers

will need to assess their particular situation and employ one or more of the

techniques discussed in this bulletin.

Finally, in implementing a damage control program, it is important to exercise

caution and follow procedures on the

label instructions before using pesticides

or frightening devices.

The National Wildlife Research Center

(NWRC), which is part of USDA’s ADC

program, is the only Federal entity

devoted to wildlife damage-control

research. NWRC scientists, located in

Ft. Collins, CO, and at field research

stations throughout the United States,

design and test environmentally safe

and cost-effective methods of reducing

wildlife–human conflicts. University

researchers and private industry also

contribute valuable information for solving wildlife problems.

Wildlife management methods developed by these research programs are

used under field conditions by ADC’s

wildlife specialists. Regional headquarters are located in Denver, CO (303

969–6560), and Nashville, TN (615

736–2007). ADC also maintains many

State offices, which are usually located

in State capitals. We encourage sunflower growers to contact their State’s

ADC office for assistance with wildlife

damage problems.

Research and Methods

Implementation
15

The following bibliography lists a few

useful materials on the subject of blackbird control.

Booth, T. W. 1993. Bird dispersal techniques. In: Hygnstron, S. E.; Tim, R. M.;

Larson, G. E., eds. Prevention and control of wildlife damage. Lincoln, NE: University of Nebraska Cooperative

Extension Service.

Dolbeer, R. A. 1980. Blackbirds and

corn in Ohio. Res. Publ. 136. Washington, DC: U.S. Department of the Interior,

Fish and Wildlife Service. 18 p.

Dolbeer, R. A. 1993. Blackbirds. In:

Hygnstron, S. E.; Tim, R. M.; Larson,

G. E., eds. Prevention and control of

wildlife damage. Lincoln, NE: University

of Nebraska Cooperative Extension

Service.

Kopp, D. D.; Carlson, R. B.; Cassel,

J. F. 1980. Blackbird damage control.

Circ. E-692. Fargo, ND: Cooperative

Extension Service, North Dakota State

University. 5 p.

Leach, J. A.; Linz, G. M.; Baltezore, J. F.

In press. Economics of cattail (Typha

spp.) control to reduce blackbird damage to sunflower. Agriculture, Ecosystems & Environment.

Linz, George M.; Hanzel, J. J. In press.

Birds in sunflower. In: Schneiter, A., ed.

Sunflower, 2d ed. Agronom. Monogr.

No. 35. Madison, WI: American Society

of Agronomy, Crop Science Society of

America, and Soil Science Society of

America.

Robbins, C. S.; Brun, B.; Zim, H. S.

1983. Birds of North America: a guide to

field identification. New York: Golden

Press. 360 p.