Featured Species Description
Tricolored Blackbird
If you look closely through flocks of blackbirds foraging in fields and grasslands in the Central Valley, you may notice some with white stripes on their folded wings. When those birds flush up into the air, the stripes are revealed as lower borders to brilliant crimson patches, each dashingly set against a satin black wing. These three colors of the males - black, red, and white - provide the bird with its name, the Tricolored Blackbird. On the other hand, females and young lack the wing patches and are dull blackish-brown with pale and dark streaking on the upper breast and head.
Observing a Tricolored Blackbird nesting colony from a safe distance provides one with indelible memories of their loud, cacophonous songs, their densely packed territories and their bold manner. This species is one of California's wildlife jewels -- not to be confused with its widespread and common cousin, the Red-winged Blackbird.
With one of the smallest global ranges of any North American songbird, over 99% of the Tricolored Blackbird world population nests in California, with the vast majority in the Central Valley. It is the most colonial of all North American songbirds and one of the most susceptible to massive nesting failure from predator and human disturbance, including mowing or harvesting of fields that are home to nesting colonies. Thus, protection of nesting colonies of Tricolored Blackbirds in the Central Valley is key to the species' survival. Sadly, results from recent surveys indicate that the population has suffered significant declines over the past few decades.
Tricolored Blackbirds choose colony nest locations carefully. They need drinking water nearby, vegetation that can hide or protect the nests from predators, and large open landscapes where they can find enough insects and other prey (snails, small clams, worms etc.) to feed themselves and their young. In addition, some colony sites are used annually while others are only used for one nesting season and abandoned in subsequent years. Thus, it becomes difficult to predict where Tricolored Blackbird colonies will appear in any given year.
While colonies can range from a few to over 100,000 nests, remarkably these blackbirds can synchronize their egg-laying so that all pairs build nests and lay their first eggs within a week of settling into the colony. This enables an entire colony of blackbirds to take advantage of temporary habitat conditions by rearing young in only 45 days. Colonies that do not synchronize their egg-laying grow in size as new birds arrive to begin nesting at the periphery of the colony, and the overall nesting period lasts much longer.
In Yolo County, the nesting population is fragmented into a few relatively small colonies of hundreds to several thousand pairs. The number and locations of colonies vary year-to-year depending upon weather and cropping patterns, local population levels of insect prey and other factors. In recent years, these colonies have nested primarily in patches of Himalayan blackberry, thistle, cattail/bulrushes marshes and safflower fields, unlike those in the southern San Joaquin Valley where some of the largest colonies are known to nest in wheat and triticale (hybrid rye and wheat) fields near dairies. Other known nesting habitats in the Central Valley include stinging nettle and willow thickets. Creating additional suitable nesting conditions in Yolo County may attract new colonies.
During fall and winter, Tricolored Blackbirds form large, nomadic flocks and a few may join flocks of other blackbird species. In search of concentrations of waste grain and other seeds that are the staple of their winter diet, these flocks can range to the coast and throughout much of the Central Valley and inland valleys.
John Sterling is a Wildlife Ecologist at H.T. Harvey and Associates, an environmental consulting firm. He is a lifelong birder and currently serves as the President of the Central Valley Bird Club. He is also a nature photographer, and the photographs in this account are used with his permission.
Photos used with permission from John Sterling - harveyecology.com(click for full size pictures)
