Tuleyome Tales: Return of the Swainson’s Hawk

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A Swainson’s hawk in Contra Costa County displays typical nest building activity. (Dave Harper/Courtesy photo)

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By Judith Lamare
Special to the Express

When will the first Swainson’s hawk return to our region from its annual migration south? Certainly by the second week of March, we will see the early returnees circling above their nesting trees throughout the Central Valley of California and foraging in nearby agricultural fields. Sacramento, Yolo, Contra Costa and San Joaquin Counties have the highest concentrations of nesting sites.

Swainson’s hawks leave our region in September to fly thousands of miles south. A recent study showed that hawks who nest in the same community, spend the winter in different areas, as far apart as Sinaloa, Mexico, Meta, Colombia, and Salta, Argentina. When a hawk returns to our region, it returns to the site where it nested the previous season, and meets up with its mate there.

Swainson’s hawks are found in various colors, but these field marks remain constant. Some Swainson’s hawks look purely black and white, and are called “light morphs,” while others may have feathers of dark browns, so the field marks aren’t readily apparent.

They are called “dark morphs.” Many others are “intermediate” between light and dark. The way to tell a Swainson’s hawk from a red-tailed hawk is by looking at the underside of the wing. The red-tailed hawk will have a dark leading edge of the wing while the Swainson’s hawk wing will be lighter at the leading edge. The red-tailed hawk will have a “belly band” of color next to a white chest, while the Swainson’s hawk will have a lighter belly than their chest color.

In 1983, the State of California declared the Swainson’s hawk to be threatened according to the criteria set by the California Endangered Species Act. Since then the California Department of Fish and Wildlife (CDFW) has confirmed the need for special government protection for this species. By the end of March in California, about 2,000 Swainson’s hawk pairs will be preparing nests to take care of eggs. If you witness harassment of hawks, contact the CDFW hot line at 1 888 334-CALTIP (888 334-2258), 24 hours a day, seven days a week or you may submit anonymous tips to CDFW using tip411 .

By April, Swainson’s Hawk pairs are in nest building, or rebuilding, mode. They will build at the site of their last nest, or in a suitable tree nearby. Nests are usually in tall, older trees, near the top of the tree. To locate one, watch for hawks flying in and out of a tree with sticks in their beaks.

The chicks would have started flying from the nest by July 1. They start learning by climbing out of the nest on branches, called “branching.” This is a very exciting time for hawk nest watchers. Our nesting hawk pairs need nearby foraging areas to feed a new generation of our most endangered raptor in California.

The best foraging is alfalfa fields and irrigated pasture because this is where the highest value prey are found in large numbers for the longest period of time. The favorite prey for feeding the young are small field mice, squirrels, rabbits, and voles. The biggest threat to the breeding success of the Swainson’s hawk is the loss of foraging grounds, largely as a result of urbanization of agricultural land. Preservation of agricultural land and urban limit lines is critical to protecting foraging habitat.

Judith Lamare is co-founder of Friends of the Swainson’s hawk, a citizen advocacy group based in Sacramento. Find Friends of the Swainson’s hawk on Facebook and at www.swainsonhawk.org.

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