March of the collared-dove, Whimbrel watchers needed, new threat to Peregrines, Tricolored Blackbirds in California, duetting songbirds
Birding Briefs -- August 2008
Published: June 20, 2008
|Whimbrel watchers needed|
Have you seen this band? The Whimbrel in the foreground at right wears a band that was attached to its leg on Chiloe Island in Chile, a wintering site for tens of thousands of Whimbrels and Hudsonian Godwits. Seven weeks after it was banded, the bird was found in March 2007 at California's Mystic Lake - about 6,500 miles from Chile.
Researchers from the U.S. Fish and Wildlife Service and other agencies have banded individuals of both species in hopes that resightings will uncover their migration routes. If you spot a bird wearing a band, report it to Jim Johnson (firstname.lastname@example.org; 907-786-3423) or Brad Andres (email@example.com; 303-275-2324). We've published detailed information about what to look for on our blog, Birder's World Field of View.
Annual count plots the march of the collared-dove
Introduced in the Western Hemisphere in the mid-1970s on New Providence, Bahamas, the Eurasian Collared-Dove is showing no signs of slowing its explosive range expansion and population growth in North America.
That's the dramatic conclusion of February's four-day Great Backyard Bird Count (GBBC), sponsored by the National Audubon Society and the Cornell Lab of Ornithology. Observers reported collared-doves in British Columbia, Manitoba, and Oregon for the first time ever, and they counted a record 10,542 collared-doves in 39 states and provinces, up from 8,080 birds in 35 states and provinces last year.
Among the 10 sites reporting the most collared-doves, three were in Florida, two were in Texas, and two were in Colorado. The only region in which the bird was not found was the Northeast.
Since 1999, when 1,078 collared-doves were found in eight southeastern states, the GBBC has documented a nearly 10-fold increase in the population.
The bird's success has been attributed to the wide availability of seed offered by backyard bird feeders. But it has a long way to go to catch up to its darker-plumaged relative, the Mourning Dove. It was the second most-frequently reported bird on this year's count (Northern Cardinal was first) and the tenth most numerous, coming in at 268,699 individuals.
This year's count also produced record numbers of participant checklists (85,700) and species (635). Masked Duck, Ivory Gull, and Arctic Loon were reported for the first time. And northern finches were tallied in large numbers, including Common Redpoll (100,805) and Pine Grosbeak (15,830).
|Common Black-Hawk, Loggerhead Kingbird, and more rare birds|
Falcons seared in fight against flames
Decades after DDT nearly drove the Peregrine Falcon to extinction, the world's fastest bird is facing a growing, new chemical menace.
We first learned about PBDE, or polybrominated diphenyl ether -- a substance used as a flame retardant in mattresses, television casings, electronics, and other products -- in March 2007, when researchers reported that eight eggs in Maine and New Hampshire contained toxic amounts of deca-BDE, the most common type.
Now comes news that falcons in San Francisco, Long Beach, Los Angeles, and San Diego are also depositing the flame retardant in their eggs, and in the highest concentrations ever found in wildlife.
Scientists at the California Department of Toxic Substances Control and two universities concluded this after examining 95 unhatched eggs and two dead chicks collected between 1986 and 2007. Deca-BDE was found in higher levels in birds from big cities than birds from coastal or inland areas.
Urban Peregrines' reliance on pigeons as a main source of food may account for the difference. "We find significant levels of BDE-209 in urban pigeons," the researchers write.
The chemical's impact on breeding success is unknown.
A new tune about duetting songbirds
Male and female birds of a handful of songbird species sing duets - overlapping songs that suggest the vocalizations are organized. The behavior has been reported in more than 220 species worldwide, or about 4 percent of passerines, and was thought to be most common among tropical and subtropical birds.
But a graduate student at the University of California at Berkeley has shown that duetting also occurs in at least 7 percent of temperate-zone North American songbirds.
Twenty-one species from 12 families sing duets. They include Great Kiskadee, Pygmy Nuthatch, Carolina Wren, Ruby-crowned Kinglet, Gray Catbird, Painted Redstart, Western Tanager, Baltimore Oriole, Common Redpoll, and House Sparrow.
The behavior appears to have evolved separately at least 17 times, writes the researcher, Lauryn Benedict, in the January 2008 issue of the Journal of Avian Biology. She compiled the data using species accounts published in The Birds of North America.
Birds that duet are far more likely than non-duetters to maintain long-term monogamous pairs, and 50 percent of duetting species defend the same territory year-round.
|Agreement spares blackbirds|
The list of threats to the Tricolored Blackbird is long -- loss of nesting habitat, low reproductive success in marshes and uplands, and breeding failure when farm fields are plowed. No wonder its population declined as much as 50 percent in the 1990s. Few of our birds are so deserving of protection.
So it was especially good to hear that the largest Tricolored colony in the world -- 80,000 birds, nearly one-third of the total population -- was safeguarded in May. The blackbird lives primarily in California's Central Valley.
A farmer in Tulare County agreed to delay harvesting 160 acres until the birds that nest on the land have fledged their young. Audubon California will compensate the farmer for any lost value to his crops. A year earlier, a similar agreement protected a Riverside County colony.