Bird of the Month: Tricolored Blackbird
Written by Andy McCormick
Andy McCormick, Volunteer and Former Board President of Eastside Audubon
The Tricolored Blackbird evolved in the wetlands of Central California but in response to habitat loss and a warming climate it is expanding its range. It arrived in Washington in 1995.
The Tricolored Blackbird is a close relative of the Red-winged Blackbird (Agelaius phoeniceus) but evolved separately during the ice age about 10,000 years ago. Both males are black, but the tricolor has a glossy appearance. The epaulettes (lesser coverts) of the tricolor are a brick red in place of the bright red of the redwing, and the trim color (median coverts) is white in place of the light yellow of the redwing.
The female tricolor is smaller than the male and has a cold gray plumage (Sibley) with no rufous coloring, and a dark grey belly. Both the male and female tricolors have a long, narrow, and pointed bill. The song of both sexes is a harsh descending nasal scold. Photos, vocalizations, and videos of the Tricolored Blackbird can be found at the Macaulay Library.
Taxonomists place both of these blackbirds in the genus Agelaius, from the Greek, agelaios, belonging to a flock. The tricolor species name references the three colors of the male’s breeding plumage: a black body, with a red and white wing patch.
A COLONIAL NESTER
Tricolored blackbird
Scientific Name: Agelaius tricolor
Length: 8.75”
Wingspan: 14”
Weight: 2.1 oz (59 g)
AOU Alpha Code: TRBL
The Tricolored Blackbird is a colonial nester and has strict requirements for successful breeding. Suitable breeding habitat is characterized by “(1) a protected substrate in flooded, thorny, or spiny vegetation; (2) an open accessible source of water for drinking and bathing; and (3) a suitable foraging space providing insect prey” (Meese and Beedy 2015:81). Historically, the once widespread wetlands of the Central Valley of California fulfilled these requirements.
However, expansion of human development and agriculture, including the conversion of grasslands to fruit and nut orchards, has reduced tricolor foraging habitat, The filling of wetlands reduced their breeding habitat. These losses now force Tricolored Blackbirds to use alternative nesting substrates, one of which is Himalayan Blackberry.
SYNCHRONICITY IN BREEDING
Tricolored Blackbirds nest in a synchronistic pattern. In early spring flocks of tricolors search for habitat suitable for breeding, often in a location previously used by colonies. This could be a wetland or mass of spiny shrubs such as blackberry. Members of the flock perform reconnaissance flights in areas up to nine kilometers from the nesting site searching in upland grassland for insect prey consisting of dragonflies, damselflies, and sometimes mayflies. If the abundance of insects is satisfactory, females will begin building nests in unison. If not, the entire flock will abandon the location.
Tricolored Blackbird colonies once contained 100,000 nests. Today, colonies consist of hundreds to thousands of nests constructed as close as 18 inches from one another. The same shrub or clump of cattail may contain five or six nests. Egg laying occurs in all the nests within the same few days. After egg laying, females stay deep in the marsh out of sight. Incubation takes 11 days and young leave the nest in about two weeks (Kaufman). The entire colony completes the breeding process from nest building to fledging in 42 days.
Female Tricolored Blackbird
RISKS AND BENEFITS
Colonial nesting to this extent is uncommon among birds. The Passenger Pigeon once nested in similar large colonies. Large flocks provide mutual protection, and synchronous breeding allows reproduction within a restricted time window. Tricolors must complete the breeding cycle beginning during spring flooding and the emergence of aquatic insects and ending with the heat of early summer and the accompanying drying of wet areas. The tightly-knit colonies allow predators such as rodents, skunks, snakes, muskrats, herons, and birds of prey to move easily and quickly from nest to nest devastating a colony. In response to heavy predation an entire flock will abandon the colony even leaving live chicks in the nest.
Tricolors also practice brood reduction. This behavior results from a lack of insect prey. Newly hatched tricolors feed only on insects for the first nine days of life and if there are not enough insects to go around, adults will remove hatchlings from the nest. Hundreds of hatchling carcasses litter the ground at large tricolor colonies.
STATUS AND DISTRIBUTION
After a six-year study completed in 1937, John Neff estimated there were over 1,500,000 Tricolored Blackbird nests in 26 counties in California. This translates to a population of millions of Tricolored Blackbirds. Historically, tricolors have also bred in Oregon and Baja California. Today 98% of the Tricolored Blackbird population is in the Central and San Joaquin Valleys of California.
Tricolors were first recorded in Washington in 1995 when a colony of about 30 birds was observed in Wilson Creek which is east of Soap Lake. The population of tricolors in Washington is small and variable. No systematic survey has been conducted. Current colony size estimates of between 30 and 150 individuals and evidence of breeding have been determined using eBird checklist reports (McCormick). Between 50 and 150 Tricolored Blackbirds overwinter in Adams County near Othello while surviving on dairy cow feed grain, a century-old behavior among tricolors in California.
In May 2023 tricolors were reported for the first time in Idaho. This finding and previous expansion into Washington, Northeast Oregon, and Nevada suggest that these birds are expanding their range northward. Likely factors in the expansion include the reduction of suitable breeding and foraging habitat by human activity, and drying of previous wetlands due to global climate change as a multi-year drought continues in Southern California and Baja California.
REFERENCE
For a full analysis of the Tricolored Blackbird in Washington, please see: McCormick, A.J. (2022), The Tricolored Blackbird in Washington: First assessment of status and distribution. Western Birds 53:3, 186-198. McCormick, Western Birds
Photo credit Andy McCormick.
References available upon request from amccormick@eastsideaudubon.org
Visit the Eastside Audubon Bird Gallery to read Bird of the Month articles covering over 200 bird species.