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Utility poles and Harris's Hawks, Cooper's Hawk eye color, a critical river for Whooping Cranes, and a new book about the Ivory-billed Woodpecker
Utility poles and Harris's Hawks, Cooper's Hawk eye color, a critical river for Whooping Cranes, and a new book about the Ivory-billed WoodpeckerBirding Briefs -- August 2004
Published: June 25, 2004 Fatal Attraction
Utility poles give birds of prey high perches to scan for food, but as most urban birders know, the poles can also be deadly for the birds. Any animal that comes in contact with two phase wires on a pole or a phase wire and a ground completes a circuit and receives a fatal jolt of electricity. In Tucson, Arizona, utility poles are particularly deadly for Harris's Hawks.
James Dwyer, a graduate student at the University of Arizona's School of Renewable Natural Resources, has studied raptor electrocutions in Tucson for the last two years. He has discovered that electrocution causes 80 percent of all Harris's Hawk deaths in the area.
Furthermore, Dwyer discovered that about 70 percent of all electrocutions are of young birds and roughly 15 percent of incidents involve adult females.
Dwyer, who was profiled recently in the Arizona Daily Star, is working with Tucson Electric Power Co. to place bird guards on utility poles to prevent raptor deaths. Because it's impractical to retrofit all of the company's 100,000 utility poles, Dwyer has recommended fixing the poles within 1,000 feet of each Harris's Hawk nest. This year, about 1,500 poles around 78 nests will receive bird guards.
Other birds commonly electrocuted in Tucson are the Great Horned Owl and the Red-tailed Hawk. |
Hawk Eyes
Ask an expert hawk watcher for a way to gauge the age of a Cooper's Hawk that no longer has a juvenile's brown back and brown-streaked breast and face, and the expert will probably tell you to take a long look at the color of the bird's eyes.
And for good reason. For as Contributing Editor George H. Harrison wrote in our October 2003 issue (Cooper's Hawk was pictured on that issue's cover, shown at right), it is well known that the eyes of first-year Cooper's Hawks start out yellow or light orange and then darken, becoming orange or red as the bird grows older. The change is especially noticeable in males.
But just how reliable is eye color as an indicator of age? To answer that question, Robert Rosenfield, a biologist at the University of Wisconsin, Stevens Point (the same professor Harrison quoted in his article), staked out Cooper's Hawk nests in North Dakota and on Vancouver Island, British Columbia, between 1999 and 2002. Working with colleagues in Canada, North Dakota, Wisconsin, and Minnesota, Rosenfield captured and re-captured dozens of hawks, noting each bird's eye color, sex, age, and reproductive output. Then they compared their results with similar data from an earlier study of Cooper's Hawks in Wisconsin.
As expected, older Cooper's Hawks tended to have darker irises than younger hawks, and males had darker eyes than females. (The researchers found females that were nine years old but had yet to acquire red irises.) But Cooper's Hawks in North Dakota and British Columbia acquired orange or red irises more frequently and more quickly than birds at known and comparable ages in Wisconsin.
Even if the irises of a hawk from British Columbia and a hawk from Wisconsin were the same color, the birds might still be different ages.
Rosenfield and his colleagues published their results in the September 2003 issue of the Wilson Bulletin, the quarterly journal of the Wilson Ornithological Society. |
Whooping Cranes and the Platte
Each spring, the world's only flock of wild Whooping Cranes migrates from the Texas coast to breed in Wood Buffalo National Park in Canada. In fall the birds return to Texas. Along their 2,400-mile route are several stop-over sites, noted on the map above, where the endangered cranes rest and eat. Each site is important to the survival of the 185-bird flock, but because of its central location on the flock's migratory corridor, Nebraska's Platte River is an especially important stop-over site.
A National Academy of Sciences report released in April questions the quality of crane habitat along the central Platte. It says the river's habitat conditions "adversely affect the likelihood of survival of the Whooping Crane, but to an unknown degree." In any one year, about seven percent of the crane population stops over along the Platte, and most, if not all, Whooping Cranes stop over on the Platte at some time in their lives.
The report, written by a committee of biologists, ecologists, engineers, and others, says, "If habitat conditions on the central Platte River -- that is, the physical circumstances and food resources required by cranes -- decline substantially, recovery could be slowed or reversed."
The Platte River also is critical to the survival of two other conservation-dependent birds: the threatened Piping Plover and the endangered Interior Least Tern. The National Academy's report says the river's habitat conditions "adversely affect" the survival and recovery of the two birds. Bare sandbars and beaches have disappeared along the river in recent years, and at the same time, the number of breeding birds of both species has declined significantly. To address the recovery of the Platte's endangered birds, the committee recommends a multi-species management approach to the river. To read the 247-page report, click here. |
This Just In
The Greater Sage-Grouse and Kittlitz's Murrelet have been named candidates for protection under the Endangered Species Act. The U.S. Fish and Wildlife Service will study whether the birds warrant federal protection.
Alexander Skutch died at his farm in Costa Rica on May 12, eight days before his 100th birthday. Ornithologist, naturalist, and the author of dozens of books and hundreds of scientific papers, Skutch was the leading expert on Central American birds. He was honored with the Loye and Alden Miller Research Award just days before his death. The honor, given by the Cooper Ornithological Society, recognizes lifetime achievement in ornithological research. Birder's World profiled Skutch in 1990 and 2001.
The Museum of the Birds of Maryland, a 44-year-old collection of specimens, study skins, and turn-of-the-century field notes, has closed because it is inaccessible to the handicapped. The museum includes specimens of 350 species, 275 of which are mounted and on display. A fundraising campaign is expected to begin this fall to raise money to renovate a nearby building that could house the museum.
Jerome A. Jackson received the American Birding Association's Chandler Robbins Award at this year's ABA Convention. The award is given to those who make significant contributions to birder education and bird conservation. The ABA commended Jackson for his "regular contributions to Birder's World and other popular outlets."
A birding team sponsored by Birder's World and Bushnell placed third in this year's Great Texas Birding Classic. Thanks to the team, $9,000 will be donated to the Quintana Island Habitat Enhancement project. |
Searching for Ivory-bills
Recent Chandler Robbins Award recipient Jerry Jackson wrote about the Ivory-billed Woodpecker in our June 2002 issue ("The Truth Is Out There," p.40). His long-awaited book about the woodpecker hits bookstores this month (Smithsonian Institution Press, 2004, $24.95). More than a natural history of the bird, the volume relates Jackson's personal quest for the last remaining Ivory-bill.
You can order Jackson's book, In Search of the Ivory-billed Woodpecker, from Powell's Books. |
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