Denver Blackbirds
Varieties
There are many different species of blackbirds, including the Red-Winged Blackbird, Common Grackle, Great-Tailed Grackle, Brown-Headed Cowbird, Yellow-Headed Blackbird, Brewer's Blackbird and Rusty Blackbird. The Red-Winged Blackbird and Common Grackle are the most prevalent.
Red-Winged Blackbird
Identification
The male, a little smaller than a robin, is black with red and yellow shoulder patches. The smaller female is brownish, resembling a large sparrow.
Range and Habitat
The red-winged blackbird nests in hayfields, marshes and ditches. Large flocks feed in fields and bottomlands. Redwings winter in the southern United States.
Fun Facts
Insects are the dominant food during the nesting season (May through July).
Except during nesting season, redwings congregate in large nighttime roosts in marshes or woods containing up to several million birds.
Annual survival rate is only about 50% to 60%.
hese birds provide some benefits by feeding on harmful insects, such as rootworm beetles and corn earworms, and on weed seeds, such as Johnson grass.
Damage to Crops
Red-winged blackbirds can cause considerable damage to ripening corn, sunflower, sorghum, and oats in the milk and dough stages, and to sprouting and ripening rice.
Common Gackle
Identification
An iridescent blackbird larger than a robin, the common grackle has a long keel-shaped tail. The male, slightly larger than the female, has more iridescence on the head and throat.
Range and Habitat
A common nester throughout North America east of the Rockies, the common grackle nests in shelterbelts, farmyards, marshes, and towns. Flocks feed in fields, lawns, woodlots, and bottomlands. These birds winter in the southern United States, often in association with redwings, cowbirds, and starlings.
Fun Facts
Grackles have a larger, stronger bill than redwings, allowing them to feed on acorns and other tree fruits in winter.
Damage to Crops
Grackles will feed on mature field corn in the dent stage, removing entire kernels from the cob and will pull up sprouting corn.
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 given federal protection in the United States. They may be killed 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,” as stated in federal laws regarding migratory birds (50 CFR 21). Some states have additional restrictions on the killing of blackbirds.
Prevention and Control Methods
Exclusion
Generally not practical; netting can be used on small plots. Netting is cost-effective for high-value crops.
Cultural Methods
Deep planting, avoid early planting of rice. Grow nonpreferred crops near roost; provide alternative feeding sites. Avoid early or late planting; use resistant hybrids. Harvest as early as possible. Same as for ripening corn except resistant hybrids are not available. Provide alternative feeding site; early harvest.
Frightening
Several devices available; most popular is propane exploder.
Repellents
Seed treatments.
Toxicants
None.
Trapping
Generally not practical.
ACKNOWLEDGEMENTS
The above information was adapted from PREVENTION AND CONTROL OF WILDLIFE DAMAGE with permission of the editors, Scott E. Hygnstrom, Robert M. Timm, and Gary E. Larson (Cooperative Extension Division, Institute of Agriculture and Natural Resources University of Nebraska-Lincoln, United States Department of Agriculture Animal and Plant Health Inspection Service, Animal Damage Control, Great Plains Agricultural Council Wildlife Committee).