Tricolored Blackbird Life History

Habitat

Habitat Marshes

Historically Tricolored Blackbirds nested in wetlands with cattails, bulrushes, and willows, but as wetlands were converted to agricultural fields, towns, and business parks they started nesting in agricultural fields. Now a large percentage of the population nests in triticale fields, a wheat x rye hybrid used to feed dairy cows. Where wetlands are available Tricolored Blackbirds continue to use them for nesting and foraging. More recently Tricolored Blackbirds have also been found nesting in patches of Himalayan blackberry near stock ponds or irrigated pastures in the foothills of the Sierra Nevada, California. Foraging habitats include cultivated fields, feedlots associated with dairy farms, and wetlands.

Back to top

Food

Food Insects

Tricolored Blackbirds eat grasshoppers, seeds, beetles, weevils, caterpillars, and snails among other things. They also frequently eat livestock grain. They pick seeds and insects from the ground or from shrubs and occasionally fly up to catch insects in midair. Like other blackbirds, they use their large and sharp bill to pry apart dense grasses to find insects. Sometimes one will even stick its head underwater to grab an aquatic insect in a flooded rice field.

Back to top

Nesting

Nest Placement

Nest Shrub

In the past, Tricolored Blackbirds nested in freshwater marshes with cattail, rushes, and willows. They now nest almost exclusively in triticale fields, especially those with invasive mustard or mallow plants. Females select the nesting site within a male's territory, typically close to freshwater with plenty of concealing vegetation. Females build nests in vegetation from just above ground level up to about 8 feet.

Nest Description

Female Tricolored Blackbirds build an open-cup nest out of long leaves that they weave around plant stems. The female collects leaves from grasses or cattails, but before weaving them into the nest she first soaks them in water. After she completes the sides of the nest, she adds a bit of mud to the bottom and tops it off with softer plant material. Females do the majority of the building with occasional help from the male. The nest takes about 3 days to build and is about 7 inches tall and 5 inches wide.

Nesting Facts
Clutch Size:3-4 eggs
Number of Broods:1-2 broods
Egg Length:0.8-1.1 in (2.1-2.7 cm)
Egg Width:0.6-0.8 in (1.6-1.9 cm)
Incubation Period:11-14 days
Nestling Period:11-14 days
Egg Description:

Pale blue with reddish-brown splotches and wavy lines.

Condition at Hatching:

Naked and helpless.

Back to top

Behavior

Behavior Ground Forager

Tricolored blackbirds are highly social birds that nest, roost, and forage in large groups. They are obsessively noisy and readily join flocks with other blackbirds, European Starlings, and Brown-headed Cowbirds. Large black clouds of males fly en masse to and from potential breeding sites until they settle on a colony site. Tricolored Blackbirds form dense breeding colonies unlike Red-winged Blackbirds, which are more patchily distributed across the landscape during the breeding season. This is likely due to differences in territoriality: Tricolored Blackbirds defend only their nesting patch, whereas male Red-winged Blackbirds defend larger areas that include nesting and foraging areas. Courting males perch atop vegetation, sing, preen, and shift their perch over and over until they grab the attention of one or more females. Males routinely mate with one or more females, but tend to have fewer mates than male Red-winged Blackbirds. Like Red-winged Blackbirds, Tricolored males also perform a song-spread display to attract females where they hunch over their perch, spreading out the wings and tail and fluffing up the neck feathers while they sing. Once territories are set and mates secured, males and females perch at the edge of the territory, stick their bill upwards with feathers sleeked and red shoulder patches exposed to proclaim territory ownership.

Back to top

Conservation

Conservation Red Watch List

Tricolored Blackbirds declined by more than 50% since 1970, leaving the global breeding population at approximately 300,000 individuals according to Partners in Flight. They are a Red Watch List species, with a Continental Concern Score of 18 out of 20. The International Union for the Conservation of Nature (IUCN) lists them as endangered and they are being considered for the California Endangered Species List. Population declines are due, in part, to loss of wetlands due to agricultural and urban conversion as well as to draining and diverting water from wetlands. Loss of wetlands pushed Tricolored Blackbirds to nest in agricultural areas, which has now put them in conflict with farming practices. Farmers often mow triticale fields (a wheat and rye hybrid grown to feed dairy cows) where Tricolored Blackbirds nest while chicks are still in the nest, causing widespread losses. An additional strain on Tricolored Blackbirds comes from the conversion of agricultural fields to orchards and vineyards that provide no nesting habitat. Conservation efforts include working with farmers to alter harvesting schedules to allow young birds to fledge, buying farmland, and improving nesting areas on National Wildlife Refuges.

Back to top

Backyard Tips

Tricolored Blackbirds aren't likely to come to a bird feeder in urban areas, but if you live in rural areas near agricultural fields they might. You can also try putting out corn and other grains on the ground to entice them to your yard.

Back to top

Credits

Beedy, Edward C., William J. Hamilton, III, Robert J. Meese, Daniel A. Airola and Peter Pyle. 2017. Tricolored Blackbird (Agelaius tricolor), version 3.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski, Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley guide to birds, second edition. Alfred A. Knopf, New York, USA.

Back to top