Researchers look for causes of dove decline.

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Researchers look for causes of dove decline.

The continuing slide of mourning dove numbers continent-wide is the focus of attention for North America's best and brightest wildlife experts.

JEFFERSON CITY -- Prolific and ubiquitous, the mourning dove is North America's most plentiful game bird. Americans take for granted the presence of these somber yet handsome birds in backyards and grain fields. Wildlife managers aren't so complacent, however. They're putting the species under a microscope to ferret out the causes of a five-decade population decline.

Biologists who monitor populations of migratory birds have been eyeing the downward trend in mourning dove numbers since the mid 1950s. When first detected, it might have been a natural phenomenon, part of a normal cycle common in many wild species. But with 2001 population surveys showing mourning dove numbers at one quarter of the species' 1955 abundance, wildlife research biologists are sharpening investigative spades to turn up answers.

"The mourning dove is kind of a special case," says John Schulz, a wildlife research biologist for the Missouri Department of Conservation. "With almost any other species, the cause of a population decline can be linked, at least in part, to habitat. With ducks, it has been loss of wetlands, with quail and rabbits, elimination of fence rows and brush piles. But that answer doesn't work with doves."

The mourning dove, said Schulz, is a "habitat generalist." About the only places they don't thrive are wetlands and the forests of the far north. They adapt equally well to row-crop agriculture, cattle ranches, oak-hickory forest and prairie. In the absence of trees, they will even nest on the ground, rearing as many as nine broods per year from February through October. While many species dwindled in the face of intensive agriculture, mourning doves actually flourished.

What, then, could the problem be? Disease is one possibility. Schulz is studying the effects of a disease known as trichomonaisis on dove populations. If the disease is affecting dove numbers, that will raise questions about how the disease spreads and why it is a problem now.

Another possible factor that Schulz is exploring is lead poisoning. Spent pellets from shotgun shells have long been known to harm waterfowl and predators that eat ducks and geese. Water birds pick up lead pellets accidentally while feeding in areas where hunting occurs. But early results of Schulz's research indicate that doves actively look for lead pellets. They may eat them as grit to help grind food in their gizzards, or they may mistake the pellets for seeds.

"Ducks develop chronic lead poisoning from ingesting small numbers of pellets," says Schulz. "We're finding that doves eat so much lead shot that they develop acute poisoning and die. It's too early to know if this is enough of a problem to contribute to population declines, but it's important to find out, one way or the other."

Competition from exotic species is an emerging threat to mourning doves. Eurasian collared-doves, which entered the United States through Florida in the 1980s, have extended their range throughout Missouri. Originally found only in northern Africa, the species colonized Europe in the 1940s and 1950s. If they become plentiful here, they could reduce the availability of food and nest sites for Missouri's native mourning doves.

Meanwhile, the white-winged dove, originally native to the southwestern United States and Mexico, has been extending its range north and east, turning up in Missouri and as far north as Nebraska. And banded turtle-doves, sold in pet shops, also have adapted to the wild in Missouri.

Researchers also are examining the possible effect of hunting on mourning dove numbers. "The assumption has always been that mourning doves' tremendous reproductive potential could offset a carefully regulated harvest," said Schulz. That assumption is being tested in studies so we can adjust regulations if necessary.

"The good news is that doves still are plentiful throughout their range," said Schulz. "By examining the problem early, we hope we can gain an understanding of the situation before it becomes critical."

- Jim Low -
 


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