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USDA Controlling Blackbird Damage 0V& United States to Sunflower and Grain Crops Department of Agriculture

Animal and in the Northern Great Plains Plant Health lo -jo Inspection e CO Service (, j

Agriculture information Bulletin No. 679 Cover photo: Flocks of red-winged black- , 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) Mention of companies or commercial prohibits discrimination in its programs on the products does not imply recommendation or basis of race, color, national origin, sex, endorsement by USDA over others not religion, disability, political beliefs, and marital mentioned. USDA neither guarantees nor or familial status. (Not all prohibited bases warrants the standards of any product apply to all programs.) Persons with mentioned. Product names are mentioned disabilities who require alternative means for solely to report factually on available data communication of program information and to provide specific information. (Braille, large print, audiotape, etc.) should contact the USDA's TARGET Center at (202) This publication reports research involving 720-2600 (voice and TDD). . All uses of pesticides must be registered by appropriate State and/or To file a complaint, write the Secretary of Federal agencies before they can be Agriculture, U.S. Department of Agriculture, recommended. Washington, DC 20250, or call (800) 245- 6340 (voice) or (202) 720-1 1 27 (TDD). USDA is an equal employment opportunity CAUTION: Pesticides can be injurious to employer. humans, domestic , 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 containers.

2 United States Department of Agriculture Controlling Blackbird Damage and Plant Health to Sunflower and Grain Crops Inspection Service

Agriculture in the Northern Great Plains Information Bulletin No. 679 By George M. Linz, Richard A. Dolbeer, issued December 1993 James J. Hanzel, and Louis E. Huffman 1

Slightly revised August 1997

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.

Introduction

Red-winged blackbirds (Agelaius phoeniceus), common grackles ( quiscula), and yellow-headed blackbirds (Xanthocephalus xanthocephalus) cause severe damage to ripening crops in North Dakota, South Dakota, and Minnesota. Scientific sur- veys show that blackbirds damage $4 million to $1 1 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 dam- age requires knowledge about the blackbird’s habits and various methods available to prevent damage. In late summer, after the nesting sea- son, 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 , 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 popu- lation these mortal- dies every year. But Blackbirds often use alternate feeding sites when available. (APHIS photo by ity figures are offset by the birds’ George Linz.)

5 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, feed- ing 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 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. nest throughout North America in marshes, hayfields, and ditches. Often adult males mate with more than one female. are the dominant food during the nesting sea- son (May-July), with the diet shifting to predominantly grain crops and weed seeds in late summer through winter. Redwings from the Dakotas and Minne- sota migrate to the lower Great Plains and gulf coast region in winter. Red-winged blackbird (immature male) on an ear of com. (Photo courtesy of the U.S. Department of the Interior, Fish and Wildlife Service.)

6 Common Grackle Common grackles are slightly larger than robins, with iridescent black feath-

ers 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, farm- Winter migration yards, marshes, and towns. The male routes grackle usually mates with one female. Flocks feed in fields, lawns, woodlots,

Red-winged blackbirds and common grackles

Yellow-headed blackbirds

Breeding range of blackbirds

Winter range: red-winged blackbirds, common grackles Winter range: yellow-headed blackbirds

Winter range of red-winged blackbirds, yellow-headed blackbirds, and common Common grackle (mature male). (USDI, Fish grackles breeding in the northern Great Plains. and Wildlife Service, photo by Roger Clopp.)

7 and bottomlands. Grackles have a diet Other Bird Species somewhat similar to that of redwings, Other birds are sometimes seen but grackles are more predatory, feed- feeding with redwings, yellowheads, ing occasionally on small fish, field mice, and grackles but cause only minor dam- songbird nestlings, and . Grackles age to agricultural crops. The brown- also feed on acorns and other tree headed (Molothrus ater) is a in winter. Grackles often roost in cattail small, sparrow-sized blackbird. The marshes with other blackbirds in late male is black with a brown head, and summer, but grackles prefer roosting the female is gray. feed pri- sites in upland deciduous or pine trees marily on weed seeds and insects, often in their wintering locations in the South- in association with grazing livestock. ern United States. The European starling (Sturnus vulgaris)

is robin sized and is dark with light

Yellow-Headed Blackbird speckles and a distinctively short tail. A robin-sized bird, the male Although starlings sometimes forage in yellowhead has a black body with a con- grain and sunflower crops, these birds spicuous yellow head and breast and a are usually searching for insects and do white wing patch seen only when the not feed on the crop. However, starlings bird is in flight. The female is smaller will damage ripening crops. House and browner with yellow throat and Yellow-headed blackbird (mature male). sparrows (Passer domesticus) are small breast and does not have a white wing (USDI, Fish and Wildlife Service, photo by brown birds sometimes mistaken for James Leupold.) patch. Yellowheads are locally abun- female redwings. House sparrows can dant nesters in deep-water marshes of cause significant local damage to small the northern Great Plains and western seeds, sunflower, corn, and small grain crops and sunflower grown near North America. Like redwings, male grains, often in association with red- farmsteads and towns. Rusty blackbirds yellowheads often mate with more than wings and grackles. An early migrant, (Euphagus carolinus) are robin sized one female. This species feeds exten- yellowheads leave the northern Great and can be recognized in fall and winter sively on insects during the nesting sea- Plains area before redwings and grack- by their rust-colored . Their diet son and in late summer and fall on weed les, wintering in Mexico. consists largely of insects. Brewer's

8 Estimating Crop Damage

blackbirds (Euphagus cyanocephalus) Blackbird damage to agricultural crops generally 1 to 2 percent of the crop. If are similar in size to male redwings. is readily discernible because flocks of all farmers lost less than 2 percent of Males are black with whitish eyes; birds are conspicuous and signs of dam- their crops, there would be little concern; females are brownish gray with dark age are obvious. However, superficial however, the damage is not equally dis- eyes. These birds feed primarily on surveys of agricultural fields often over- tributed. While most farmers escape weed seeds and insects. estimate blackbird damage and thus economically serious blackbird damage exaggerate the overall severity of the (that which affects more than 5 percent Legal Status economic threat for four reasons; (1) the of their crops), profit margins for other Blackbirds are native migratory birds high visibility of blackbird flocks tends to farmers are significantly reduced. Some and thus come under the jurisdiction of heighten the awareness of bird damage growers would like to plant sunflower in the Federal Migratory Bird Treaty Act, a compared with other, more subtle forms their crop rotation, but the threat of bird formal treaty with Canada and Mexico. of loss caused by weeds, insects, other depredation precludes this option. Blackbirds are protected by Federal law pests, and harvesting; (2) observers Farmers whose crops are seriously (Title 50, Code of Federal Regulations, naturally seek out the conspicuously damaged by blackbirds may find various Part 21 .43) in the United States except bird-damaged plants; (3) bird damage is damage control measures cost effective. that they may be killed when found often most severe along field edges, It is important to obtain objective esti- “committing or about to commit depre- where an observer is most likely to mates of potential damage levels in a dations upon ornamental or shade trees, check; and (4) damage caused by other field before investing large amounts of agricultural crops, livestock, or wildlife, animals such as raccoon and deer or by money on control. The person making or when concentrated in such numbers wind is sometimes mistaken for bird the final decision on control measures and manner as to constitute a health damage. must consider the value of the crop, the hazard or other nuisance.” Some States Damage to sunflower and grain crops cost of control, and the degree of effec- and local governments may have addi- can be economically severe and quite tiveness of the control measure in rela- tional restrictions on killing blackbirds. frustrating to the farmer when relief is tion to the probable levels of damage. Starlings and house sparrows were not easily available. During the past two Estimates of damage levels in previous introduced from Europe and are not pro- decades, studies on blackbird damage years for the same or nearby fields are tected by Federal law. to various crops such as corn and sun- another means of predicting future dam- flower indicate that on statewide or age levels because local bird damage is regional level, overall damage is low, often fairly consistent from year to year.

9 Control Methods

This information also provides a good average damage for the 1 00 plants Cultural Practices baseline for evaluating the effectiveness examined, and this will give an approxi- Most economically severe blackbird of management strategies. Of course, it mation of the percentage loss to the damage to agricultural crops occurs in is important that estimates of damage field. Multiplying the percentage loss fields within 5 miles of roosts. Thus, be objective and reflect the entire field, by expected yield can give a rough one strategy is to plant crops that do not not just a small portion of the field that estimate of yield lost. In small grains, attract blackbirds—such as soybeans, has high damage. estimates of loss are more difficult to potatoes, or hay—in fields that are

To estimate the amount of blackbird obtain. One possibility is to compare within a few miles of a roost. If crops damage in an agricultural field objec- the yields from plots in damaged and vulnerable to damage, such as corn or tively, at least 10 locations widely undamaged sections of a field. sunflower, are planted near a roost, it is spaced throughout the field should be important that sources of alternative examined. For example, if a field has food be available to reduce the feeding

1 00 rows and is 1 ,000 feet long, the pressure on these cash crops. When estimator should walk staggered crops are ripening, one strategy for pro- distances of 100 feet along every 10th viding alternative feeding areas is to row (for example, 0-100 feet in row 10, delay plowing or tilling previously har-

1 01-200 feet in row 20, and so on). In vested cropland near the roost. Also, each of the 100-foot lengths, the estima- farmers should synchronize planting of tor should randomly select 10 plants and fields of vulnerable crops near roosts so visually estimate the damage on the that all fields mature at about the same head or ear of each plant to the nearest time. In general, as the number of suit-

1 percent (for example, 2 percent able alternative feeding areas declines, destroyed, 20 percent destroyed). For maturing grain or sunflower fields corn, six kernels usually represent about become more attractive to blackbirds,

1 percent of the corn on an ear; for sun- and protecting the crop becomes more flowers, it may be easiest to visually difficult. divide the head into four quarters and The timing of harvest can be very then estimate the percentage of seed important for reducing damage to crops missing. When finished, determine the from flocks of blackbirds. Although field

10 corn generally becomes unattractive to Corn hybrids vary greatly in their sus- Cattail Marsh Management birds when the kernels mature and ceptibility to bird feeding. Hybrids of Cattail marshes used as roost sites harden, sunflowers continue to be corn with long husk extension and thick for blackbirds can be sprayed with attractive after they mature and thus husks have been shown to be more glyphosate (®Rodeo Aquatic Plant Her- should be harvested as soon as pos- resistant to damage than other hybrids. bicide) to reduce the density of the cat- sible. Sweet corn should be harvested Sweet corn is vulnerable to blackbirds tails, which reduction in turn disperses as early as possible in areas with exten- for only a few days before harvest and, the birds. Rodeo is the only herbicide sive damage. Delaying harvest of sweet thus, may be easier to protect than field registered for controlling cattails growing corn by only 1 or 2 days can result in corn and sunflower. in standing water. (Other herbicides are substantially greater damage if flocks of available for use on cattails growing in blackbirds are in the area. marshes without surface water.) Gener-

ally, cattails must be treated 1 year Bird-Resistant Crops Planting crop varieties known to be resistant to blackbird feeding should be part of a grower’s bird-damage manage- ment plan. Bird-resistant sunflower hybrids may soon be available from commercial seed companies for use in areas subject to a high risk of depreda- tion. The seed of these hybrids is pro- tected by morphological traits, such as concave-shaped heads, horizontally ori- ented heads, and long head-to-stem dis- tance. These traits make it difficult for Sunflowers with concave heads, horizontally birds to position themselves on the plant oriented heads, and long head-to-stem appear to suffer less damage from Cattail marshes can be managed using a so they can extract seeds from the distance birds than other varieties. (Photo courtesy of registered aquatic herbicide to disperse head. These hybrids must be planted in North Dakota State University; used by roosting blackbirds. (APHIS photo by David north-south rows to maximize their bird- permission.) Bergman.) resistant characteristics. 11 before vulnerable crops are planted in Frightening devices mandates that farmers persis- the vicinity of the marsh to allow time for Frightening devices can be effective tently scare the birds before their feed- the cattails to decompose, making the in protecting crops from flocks of black- ing patterns become well established. marsh unattractive to blackbirds for birds but require considerable work and Devices need to be employed espe- roosting for several years. For maxi- long hours. The efficient use of these cially in the early morning and in late mum 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) A propane exploder and a popup scarecrow powered by carbon dioxide. (APHIS photo by John Cummings.)

12 afternoon, when the birds are most traveling up to 150 yards. Shooting Airplane Hazing actively feeding. birds with a shotgun, using standard bird Harassing feeding blackbirds with an

Propane exploders are a popular shot, often can kill a few birds and rein- airplane can sometimes be an effective frightening device. In general, there force other scare devices. However, method of chasing flocks from sunflower should be at least 1 exploder for every this technique usually is not as effective fields. This technique appears to be

10 acres of crop to be protected. in moving birds as the other devices that most effective if combined with other Exploders should be elevated on a bar- have greater range. Thus, a shotgun mechanical methods on the ground, rel stand to "shoot” over the crop, and patrol should not be used as the sole such as shotguns or pyrotechnics. they should be moved around the field means of frightening birds. every few days. Exploders should be A variety of other bird-frightening turned off (manually or with automatic devices, including electronic noise sys- timers) each night to save propane and tems, helium-filled balloons tethered in reduce objectionable noise levels. In fields, radio-controlled model planes, addition, exploders should be reinforced tape-recorded distress calls for birds, occasionally with other scare devices and various types of scarecrows, are because birds lose their fear of frighten- also occasionally used to rid fields of ing devices over time. blackbirds. The effectiveness of these By shooting a .22-caliber rifle just devices is highly variable and depends over the top of the crop, a person on a on the persistence of the operator, the stand or truck bed can frighten birds skill used in employing them, the attrac- from large fields (40 acres or more). tiveness of the crop, and the number of Obviously, care must be taken when birds and availability of alternative food shooting in this manner, and the use of sources. As mentioned with the use of limited-range cartridges is recom- propane exploders, birds tend to adjust

Also effective are pyrotechnic or adapt to frightening devices. It is mended. Airplanes can be used to scare blackbirds. devices such as cracker shells, bird usually best to mix the use of two or (APHIS photo by David Bergman.) bangers, and screamers. These pyro- more devices rather than to rely on a technic devices, fired from shotguns or single device. specially designed pistols, explode after

13 Summary Research and Methods Implementation

Repellants Although red-winged blackbirds, yellow- The National Wildlife Research Center ®Avitrol, the only chemical registered headed blackbirds, and common grack- (NWRC), which is part of USDA's ADC for control of blackbirds in corn and sun- les significantly damage agricultural program, is the only Federal entity flower, is a cracked-corn bait in which 1 crops in the northern Great Plains, devoted to wildlife damage-control

out of every 1 00 particles is treated with superficial surveys of fields sometimes research. NWRC scientists, located in the active ingredient, 4-aminopyridine. overestimate damage and lead to Ft. Collins, CO, and at field research The bait is applied by airplane along unnecessary expenditures on blackbird stations throughout the United States, access lanes placed in the fields, at the control. If significant damage is likely to design and test environmentally safe rate of 3 pounds/acre. When a black- occur in a field, an integrated pest man- and cost-effective methods of reducing bird eats one or more treated particles, it agement approach is most effective in wildlife-human conflicts. University flies erratically and emits distress calls. protecting crops from blackbirds. To researchers and private industry also This abnormal behavior often causes reduce crop losses, individual growers contribute valuable information for solv- the remaining birds in the flock to leave will need to assess their particular situa- ing wildlife problems. the field. tion and employ one or more of the Wildlife management methods devel- Careful consideration must be given techniques discussed in this bulletin. oped by these research programs are to the timing of initial and repeat Finally, in implementing a damage con- used under field conditions by ADC’s baitings. The first baiting should be trol program, it is important to exercise wildlife specialists. Regional headquar- when birds first initiate damage, and caution and follow procedures on the ters are located in Denver, CO (303 repeat baitings should occur as neces- label instructions before using pesticides 969-6560), and Nashville, TN (615 sary, about 5 to 7 days apart. Weeds or frightening devices 736-2007). ADC also maintains many that hide bait, ground insects (e.g., State offices, which are usually located crickets) that eat bait, and excessive in State capitals. We encourage sun- rainfall can contribute toward making the flower growers to contact their State’s product less effective. Instructions on ADC office for assistance with wildlife the label, especially the avoidance of damage problems. baiting field edges, should be carefully followed to avoid killing nontarget birds.

14 The following bibliography lists a few Kopp, D. D.; Carlson, R. B.; Cassel, useful materials on the subject of black- J. F. 1980. Blackbird damage control. bird control. Circ. E-692. Fargo, ND: Cooperative Extension Service, North Dakota State

Booth, T. W. 1993. Bird dispersal tech- University. 5 p. niques. In: Hygnstron, S. E.; Tim, R. M.; Larson, G. E., eds. Prevention and con- Leach, J. A.; Linz, G. M.; Baltezore, J. F. trol of wildlife damage. Lincoln, NE: Uni- In press. Economics of cattail ( Typha versity of Nebraska Cooperative spp.) control to reduce blackbird dam- Extension Service. age to sunflower. Agriculture, Ecosys- tems & Environment. Dolbeer, R. A. 1980. Blackbirds and corn in Ohio. Res. Publ. 136. Washing- Linz, George M.; Hanzel, J. J. In press. ton, DC: U.S. Department of the Interior, Birds in sunflower. In: Schneiter, A., ed.

Fish and Wildlife Service. 18 p. Sunflower, 2d ed. Agronom. Monogr. No. 35. Madison, Wl: American Society Dolbeer, R. A. 1993. Blackbirds. In: of Agronomy, Crop Science Society of Hygnstron, S. E.; Tim, R. M.; Larson, America, and Soil Science Society of G. E., eds. Prevention and control of America. wildlife damage. Lincoln, NE: University of Nebraska Cooperative Extension Robbins, C. S.; Brun, B.; Zim, H. S. Service. 1983. Birds of North America: a guide to field identification. New York: Golden Press. 360 p.