Painted Into a Corner.
Since 1966, the species has declined at an annual rate of three percent nationwide, according to nesting-bird census data compiled by the U.S. Geological Survey. 'That's pretty staggering when you figure that translates into a 50-percent decline in less than 20 years,' says Christopher W.
Thompson of the Washington Department of Fish and Wildlife, one of a handful of scientists who has closely investigated the species.
In studies in the Southeast and elsewhere, scientists are scrambling to learn more about the painted bunting and searching for clues on the causes of its decline. Key suspects in the bird's disappearance are loss of prime breeding habitat and the recent arrival of nest-sabotaging cowbirds. Buntings are not yet close to extinction, scientists say. But, adds Joe Meyers, a U.S.
Geological Survey biologist overseeing bunting studies in Georgia, 'We want to help the painted bunting before it gets to endangered-species status--while there are still a lot more birds out there to work with.' Painted buntings, like other migratory songbirds, spend winters in warm climates and fly north to breed in spring and summer. Their northern breeding range splits into two uneven parts. The expansive western portion spreads from western Mississippi to southwestern Missouri and southeastern Kansas, and southwest to southeastern New Mexico and northeastern Mexico. The smaller eastern part runs along a narrow strip of coastal plain from southeastern North Carolina to central Florida. Scientists believe the eastern birds winter mostly on Caribbean islands and in southern Florida, while western birds venture to Mexico and Central America. Unlike many other declining migratory songbirds, painted buntings usually nest and winter in bushy and partly wooded habitats rather than dense, mature forest. Scientists believe plenty of winter habitat remains, though they stress more investigation is needed.
Meanwhile, they suspect trouble is brewing on the breeding grounds-- particularly in the eastern portion, where a smaller population nests mostly along the fast-developing coast. Joe Meyers and his colleagues Lisa Duncan and Elizabeth Springborn, two University of Georgia biologists, have spent the past three years monitoring a prime southeastern breeding ground: 6,100-acre Sapelo Island. On this island off Georgia's central coast, they radio-track, band and spy on nesting buntings to study the birds' habitat preferences, productivity and survival rates.
On a warm June morning, Springborn parks the researchers' van on a dirt road surrounded by a gently rolling expanse of shrub-scrub--a sandy, bushy transitional habitat between beach dune and mature live-oak forest. Suddenly a blaze of color streaks by and an adult male bunting lands on the road in front of her. On the dusty ground, surrounded by wax myrtle and buckthorn, the bird truly looks hand-painted--a clashing patchwork of color only the most audacious artist would brush. Springborn takes in this first bunting of the day--his purplish blue head, lemon-lime back and blazing scarlet underparts and eye ring. The male hops a few inches, shakes his wings in a territorial display, then, locked on a moving rival or mate, takes off and vanishes into a wax myrtle shrub.
This roadside display is just one way male buntings warn off competitors and entice interested females. After arriving on their breeding grounds in April, males advertise their territories, singing from strategic perches and flaunting their scarlet rumps and chests. Clashing males flutter in each other's faces and grapple, sometimes tumbling to the ground for bloody battles.
Meanwhile, the retiring yellow and green females weave fine grasses into high-walled cup nests, usually in wax myrtle and other shrubs, low trees such as a red cedar or pine, or in vine tangles or Spanish moss. The female incubates her three to four eggs for almost two weeks, then she feeds her young for eight to nine days until they fledge. After the young leave the nest, male buntings pitch in and feed the loitering fledglings for about three weeks, as the females start on a second brood.
Breeding is risky business even in Sapelo's ideal shrub-scrub habitat, most of which is protected as part of a state wildlife refuge. Many nestlings and eggs disappear down the gullets of black racers, yellow rat snakes, raccoons and other predators. Some blow out of nests during violent storms. Last year proved a tough one on Sapelo: By the time the birds migrated south in late August, Springborn and Duncan tallied only nine successful nests out of 32--a success rate of just 28 percent. Duncan said 1997 was a better year: 61 percent of the bunting pairs successfully raised nestlings. She thinks warm weather in 1998 was a factor: good conditions for snakes, and therefore bad for buntings.
Some of the bunting's best remaining habitat sits on prime real estate. 'The beach areas are most important,' says Meyers. 'They can pack more birds in--but these areas are very limited in the Southeast.' The abundant food and shelter provided in shrub-scrub probably allow more bunting territories to 'fit' into these areas. Undisturbed shrub-scrub habitat, such as that on Sapelo Island, likely churns out 'surplus' birds that later disperse to marginal breeding areas.
These prime breeding areas are also coveted by people, however. 'The red flag on the Atlantic coast population is that development is escalating, so we're concerned that's why mainland populations are taking a steep nosedive,' says Chuck Hunter of the U.S. Fish and Wildlife Service (FWS). On the Atlantic coast, coastal dune scrub, weedy fields and woodland edges are being lost to resorts, subdivisions and tree farms. Buntings eat wild grass and weed seeds, and supply their young with tall-grass insects such as grass- hoppers. Development usually wipes out these resources. 'People want to eliminate all wax myrtles and other wild shrubs and lay down sod. All the structures for nesting and singing are being replaced by grass the birds can't use,' says Meyers.
Buntings do nest in less-pristine spots, such as forest patches left after housing developments replace prime habitat, but these birds likely pay a serious price. 'Predators can be a function of habitat,' says Meyers. 'In this case, the poorer the habitat, the higher the number of predators.' Among the most serious suburban hunters are domestic cats, along with nest- robbing raccoons, crows and blue jays.
Nesting buntings that evade these predators must contend with the starling- sized brown-headed cowbird, another prime suspect in the case of the disappearing bunting. This blackbird, which moved into the Southeast from the Midwest during the past few decades, lays its eggs in other birds' nests, leaving the hosts to raise their hefty young, usually to the detriment of the hosts' own offspring.
'Sightings of adult painted buntings feeding young cowbirds are now commonplace along Florida's Atlantic coast,' reports Jim Cox, Partners in Flight coordinator for the Florida Game and Fresh Water Fish Commission.
The cowbird threat seems to vary depending on habitat quality. For instance, cowbirds thrive in northeastern Florida's expanding suburbs, but are scarce in undisturbed habitats such as those on Sapelo Island. A new wrinkle has recently emerged, however: A South American and Caribbean species called the shiny cowbird seems to be expanding its range into the southern United States.
This invader first appeared in Florida in 1985, and may prove a further threat to buntings. Like their brown-headed cousins, shiny cowbirds never raise their own young. Despite the discouraging news, it's too soon to lament the demise of the Southeast's rainbow bird.
With the most likely villains--habitat destruction and cowbirds-- identified, conservationists are taking steps to stem the bunting's decline. One step is to protect optimal bunting habitat. Parks now provide scattered bunting refuges, though more information is needed about how much area the birds require and just what constitutes perfect habitat. In northeast Florida, Cox plans to study bunting nesting success in state protected areas and pinpoint areas for future parks. 'If our managed areas are the minimum needed to sustain the population, we need to be focusing acquisition efforts on some of the remaining tracts of habitat and attempt to secure these before they become shopping malls,' he says.
Another step is to control nest-raiding species. 'In my view,' says Thompson, 'the wild cards are brown-headed and shiny cowbirds.' Thompson recommends cowbird trapping programs, which help protect cowbird-plagued Kirtland's warblers in Michigan and black- capped vireos in Texas and Oklahoma.
But in the end, protected islands such as Sapelo--sparse in cowbirds and rich in good habitat--may prove the best insurance for the Southeast's buntings. Says the FWS's Hunter: 'My prediction would be that we'll continue to see a decline on the mainland, and that sea islands off South Carolina and Georgia and southern North Carolina are going to be incredibly important for the birds' long-term persistence.'
Maryland-based journalist Howard Youth wrote about rooftop-nesting least terns in the June/July issue.
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|Title Annotation:||efforts to save the painted bunting songbirds|
|Date:||Aug 1, 1999|
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