About the NWRC

NWRC is the research arm of USDA’s Wildlife Services 

program. The Center is a leader in providing sciencebased solutions to the complex issues of wildlife 

damage management as related to agriculture; natural 

resources, including threatened and endangered 

species; property and infrastructure; and public health 

and safety. NWRC scientists strive to find solutions 

that are biologically sound, environmentally safe, 

and socially responsible. Often, Wildlife Services’ 

operational staff help NWRC scientists develop and 

evaluate new management tools and methods. 

NWRC employs more than 150 scientists and support 

staff at its headquarters in Fort Collins, CO, and at 

field stations throughout the United States. NWRC’s 

scientists have expertise in a wide range of disciplines, 

including animal behavior, wildlife biology, wildlife 

sensory biology, chemistry, immunology, statistics, 

population modeling, genetics, toxicology, and 

veterinary medicine.

More Information

In addition to developing and testing new methods 

for dispersing problem blackbirds, NWRC scientists 

are also documenting habitat use and movements 

of blackbirds throughout the Great Plains. To learn 

more about these and other NWRC blackbird 

research efforts, visit us online at www.aphis.usda.gov/

wildlifedamage/nwrc. 

United States Department of Agriculture

Solutions Through Science

Managing Roosts 

Throughout the Prairie Pothole Region of the Great 

Plains, commercial sunflower crops are often planted 

near cattail wetlands. This arrangement is ideal for 

blackbirds, as they roost in cattails and easily fly short 

distances to feed on nearby sunflowers. One method 

NWRC and North Dakota State University scientists 

developed that has been successful at reducing blackbird 

damage to sunflowers is the thinning of adjacent cattails to 

make them less suitable for blackbirds.

Cattails can be sprayed with Government-approved 

aquatic herbicides between mid-July and early 

September. Herbicides should be applied in strips 

either aerially or with ground-based sprayers. The 

remaining untreated cattails offer habitat for other 

migratory birds that prefer more open wetland areas. 

For more information and guidance on using aquatic 

herbicides for cattail thinning, please call USDA 

Wildlife Services in North Dakota at (701) 355-3300. 

Other research with the College of William and 

Mary is exploring the use of “sonic nets” to disrupt 

communication among birds in a flock. Sonic nets work 

by producing a sound (usually 2–10 kHz at 80 decibel 

Sound Pressure Levels) that prevents birds from hearing 

each other’s calls. When birds cannot hear each other 

or predators, their perception of predation risk increases, 

which can cause them to leave an area. Sonic nets may 

be another way to make cattail marshes unsuitable for 

roosting blackbirds. 

NWRC headquarters in Fort Collins, CO Protecting Sunflowers From Blackbirds

Animal and Plant Health Inspection Service

Program Aid No. 1959

NWRC North Dakota 

Field Station; Fargo, ND: 

(701) 630–3776

NWRC Headquarters; 

Fort Collins, CO: 

(970) 266–6000

WS North Dakota State 

Office; Bismarck, ND: 

(701) 355-3300

“Solutions to problems depend 

upon knowledge, which only 

research can provide.” 

Edwin R. Kalmbach, first Director for the 

predecessor of the NWRC (1940–1954)

Photo credits: The photo of the red-winged blackbird was taken by

Kevin Keirn. The photo of the researcher launching a hawk-shaped 

UAS was taken by Shelly Angelucci Eshleman. All remaining images 

in this brochure were taken by USDA employees or are part of the 

APHIS image collection.

USDA is an equal opportunity provider, employer, and lender. 

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. Mention of trade names or commercial 

products in this report is solely for the purpose of providing specific 

information and does not imply recommendation or endorsement by the 

USDA over others not mentioned.

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. 

Contact Us

WS Eastern Regional 

Office; Raleigh, NC: 

(919) 855–7200

WS Western Regional 

Office; Fort Collins, CO: 

(970) 494–7443

WS Operational Support 

Staff; Riverdale, MD: 

(301) 851–4009

Revised August 2018

www.aphis.usda.gov/wildlifedamage/nwrc
A researcher launches 

an unmanned 

aircraft system (UAS) 

shaped like a hawk 

over a commercial 

sunflower field. This 

is one of several 

collaborative studies 

between NWRC, 

the Federal Aviation 

Administration, and 

university scientists to 

explore the use of UAS 

to disperse birds from 

agricultural crops. 

Problem

In late summer, large flocks of blackbirds gather 

in the northern Great Plains to prepare for their 

strenuous migration to southern wintering grounds 

in the United States and Mexico. The birds acquire 

energy for their trip by feasting on nutrient-rich 

seeds and berries. Unfortunately for farmers, many 

of those seeds come from agricultural crops. Redwinged blackbirds, common grackles, and yellowheaded blackbirds cause most of the damage to 

commercial crops. Sunflower producers in North 

Dakota, South Dakota, and Minnesota suffer millions 

of dollars in losses each year due to blackbirds. 

Reducing blackbird damage to sunflower crops is 

a constant challenge for farmers. They can suffer 

losses ranging from slight to devastating (total 

crop loss). Blackbirds tend to eat just a portion 

of the grain in a field; this damage lowers the 

overall yield, but it often isn’t enough to trigger an 

insurance claim. 

Birds that gather in fields in mid-August are also not 

easy to harass: they are molting their flight feathers 

and tend to stay in nearby wetlands. It is these birds 

that can cause the most damage. 

Through research and direct help in the field, the 

U.S. Department of Agriculture’s (USDA) Wildlife 

Services program works with farmers to address 

these challenges.

Science-Based Solutions

To help reduce blackbird damage to commercial 

sunflower crops, scientists at USDA are working with 

university partners to better understand the birds’ 

ecology and behavior. Much of this work takes place at 

the National Wildlife Research Center’s (NWRC) field 

station in Fargo, ND. There, scientists are studying 

the effectiveness of various bird repellents to protect 

crops, habitat management to prevent large roosts, and 

the use of unmanned aircraft systems (also known as 

drones) as scare devices and monitoring tools. They 

are also looking at existing tools and how to broaden 

and enhance their use in managing damage.

Repellents and Farming Practices

NWRC researchers are working to identify, develop, 

and improve chemical repellents for reducing 

blackbird damage to ripening sunflowers. They are also 

evaluating methods to effectively spray repellents onto 

sunflower heads. The heads hang nearly horizontal to 

the ground, which makes spray treatments difficult. 

USDA also works directly with growers who are having 

problems with blackbirds. Wildlife Services personnel 

help growers reduce damage using several tools and 

methods. Propane cannons and pyrotechnics scare 

birds away from fields, and farming practices that 

remove ripened sunflowers earlier in the season can 

also head off problems. For example, applying a drying 

agent, such as glyphosate and saflufenacil herbicides, 

to sunflowers allows farmers to harvest earlier and 

avoid late-season damage from blackbirds.

New Scare Devices and Monitoring Tools 

One promising new tool in wildlife damage 

management is unmanned aircraft systems (UAS). 

NWRC scientists are evaluating if UAS can be used 

as a scare device to protect crops from birds and for 

monitoring wildlife activities. Because UAS are mobile, 

they can overcome the limits of stationary hazing 

devices. NWRC is researching bird responses to UAS, 

as well as best practices for their use. For example, 

which UAS color, size, and shape works best? At what 

approach, altitude, and speed do UAS most effectively 

disperse birds? 

Red-winged 

blackbirds cause 

most wildlife damage 

to sunflower crops.

The potential of UAS as a hazing tool will depend on 

how blackbird flocks behave in response. Many factors 

impact whether or not a flock will leave a field. These 

include not only the UAS type, number, and flight 

dynamics, but also flock size and access to other 

food sources. 

Using Lure Crops 

“Lure crops” or “wildlife conservation plots” can 

significantly reduce bird damage to nearby commercial 

sunflower fields. The concept is simple—plant a small 

field (about 20 acres is ideal) of sunflowers or another 

crop, such as corn, that attracts blackbirds. Do not 

spray the crop with insecticides, and do not harass the 

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

crop as long as possible, thereby reducing the time 

they spend in nearby commercial sunflower fields. 

Each seed eaten in the lure crop is one less seed eaten 

in the commercial field. To encourage the birds to stay 

in sections planted with the lure crops, farmers can 

continue to spray registered repellents and harass 

birds in their commercial fields. 

Based on NWRC’s research, the most successful 

lure crops are those planted between wetlands and 

commercial fields. The lure crops have also proven 

beneficial to many other bird and wildlife species. 

USDA’s Agricultural Research Service and the 

University of Minnesota are developing a high-yielding 

strain of perennial sunflower that could be used as 

a lure crop to entice birds away from highly valuable 

commercial crops. 

Cattail stands are thinned to make them less suitable 

for blackbirds.

Roughly 39 million red-winged 

blackbirds, 19 million common 

grackles, and 17 million 

yellow-headed blackbirds 

migrate through the Great 

Plains each fall.

Partnering with NWRC 

investigators are 

scientists from North 

Dakota State University 

and stakeholders from 

the National Sunflower 

Association.