Mini geo-locators give researchers first migratory information on mountain plovers

2012-01-26T00:10:00Z Mini geo-locators give researchers first migratory information on mountain ploversBy BRETT FRENCH french@billingsgazette.com The Billings Gazette
January 26, 2012 12:10 am  • 

Tiny backpacks carried by mountain plovers that nest in northeastern Montana have given researchers their first glimpse into where the birds travel when they fly south at the end of summer.

Only two of the 24 birds that were fitted with the geo-location devices were recaptured this spring, so the data that was downloaded is sparse. Yet from the recovered information researchers discovered that the birds flew to Nebraska before continuing on to Colorado and Kansas. They eventually wintered in parts of Oklahoma and Texas.

“We’re trying to get some handle on where they are overwintering,” said Steve Dinsmore, an Iowa State University researcher who has spent 17 years studying mountain plovers in northeastern Montana. “This fills in another piece of the puzzle on their life history.”

Rained out

The long-legged black, brown and white birds, which are smaller than a robin, have generated a lot of interest out of concern that their numbers were perilously low. Despite petitioning by conservation groups, the U.S. Fish and Wildlife Service decided in May that the birds were not sufficiently threatened or endangered across a large extent of their range to warrant protection under the Endangered Species Act. The agency estimates there are more than 20,000 breeding pairs of the birds, many of which winter in California.

Montana’s wet spring hampered the researchers’ recapture of birds fitted with geo-locators. That’s why only two were recovered. The Montana research is being conducted in southern Phillips County, an area known for its slippery “gumbo” roads whenever rain falls. That made access tough. Also, mountain plovers favor arid landscapes. With much of the prairie under water, they found the environment less hospitable.

Given a drier spring this year, the plovers should come back. Dinsmore has found that in Montana, the birds are closely associated with prairie dog towns. More than 75 percent of plovers located in the state nested in the vegetation mowed down by prairie dogs. Many of the ground-nesting mountain plovers are faithful to a specific prairie dog colony over the course of their life. So declines in prairie dog populations in the region — largely due to sylvatic plague but also caused by landowner poisoning and shooting — can force plovers to relocate.

Over the past two years, the combination of wet weather and fewer prairie dog towns has meant that mountain plover nesting success has dropped in southern Phillips County. Last year’s nesting success — only 21 percent — was the lowest since Dinsmore began keeping records.

“The number of birds that the researchers have gotten in hand has declined each of the last two years,” said biologist Dennis Jorgensen of the World Wildlife Fund, which is helping to fund Dinsmore’s research. “These birds are specialists of arid climates, but we’ve been faced with two wet years.”

Mountain plovers generally arrive in Montana around mid-April. The female will lay a clutch of three eggs that the male incubates. Then she will lay another three eggs that she will incubate. Sometimes she breeds with another male.

If a nesting is unsuccessful, the birds will often try again. But third attempts are rare because it takes about five weeks to rear the young before they fly south around the end of September or first week in October. Birds hatching too late wouldn’t be able to make the trip.

Since the birds are long-lived — the oldest one Dinsmore has marked is now more than 12 years old — their chances of reproducing again are good even if there are problems for one or two years. So there’s hope that the low nesting success will reverse itself, he said.

All together now

Dinsmore’s study of mountain plovers has reinforced how interdependent some of the short-grass prairie and plains animals are. Prairie dogs, with their burrowing and clearing of vegetation, create habitat for owls, hawks, songbirds and ferrets, in addition to mountain plovers.

All the species are closely tied to the stewardship of landowners, farmers and ranchers. Jorgensen said the research that Dinsmore has conducted on mountain plovers was aided by people like landowner Dale Veseth.

“Ranchers are the primary managers and stewards of the land out there because they act as partners,” Jorgensen said. “We need to try and engage ranchers so these birds have a place to breed to sustain the population overall.”

This spring, provided the conditions are favorable, Jorgensen hopes to fit another 11 birds with the tiny 2- to 3-gram backpacks that allow tracking. The devices work by recording the time of sunrise and sunset as well as the light intensity. The units are capable of storing about one year’s worth of data.

“This is the first time the technology has gotten small enough to track these small animals,” Jorgensen said.

The birds are captured at night when they are on their nests. The geo-locator information can only be collected if the birds return to the same area where they can be recaptured.

The World Wildlife Fund is paying for Dinsmore’s work to locate and monitor plover nests to determine hatching success; to band plovers to determine annual survival, population size and trends; and to find out more about mountain plovers’ migration schedule and routes.

With the recovery of more of the geolocators, the researchers’ data will be more conclusive than that from just two units, Jorgensen noted.

“We’re trying to understand how mountain plovers utilize a prairie dog landscape that is constantly changing,” Dinsmore said.

Although he has been researching in the area for 17 years, Dinsmore said he wants to keep returning as long as there are “new and exciting questions coming up.

“They’re a fascinating bird.”

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