Not all birds live in trees -- many bird species depend on open grasslands for food and shelter, and their habitat is disappearing. Some of these little birds carry miniature transmitters and geo-locators on their backs, helping scientists understand migratory patterns, wintering grounds and survival needs.
Greg Levandoski, director of operations for the international program of Rocky Mountain Bird Observatory (RMBO), along with his colleagues, has been studying and researching grassland birds as they migrate from Colorado and states farther north to the southern United States and Mexico. He concentrates on the Chihuahuan Desert, where he says there are 15-17 grassland priority conservation areas that biologists and conservationists think are the most important grasslands remaining. Their research area covers Arizona, New Mexico, Texas and six states in Mexico.
According to RMBO information, the Chihahuan desert provides primary wintering grounds for more than 90 percent of grassland birds in western North America. These range from raptors to songbirds, including the Baird's and grasshopper sparrows, mountain plover, Ferruginous hawk, western meadowlark and Colorado's state bird, the lark bunting. RMBO has about 140 species of grassland birds in their database, and focus on about 30 high-priority species that either benefit from or require grasslands.
Learn more about migratory birds by attending the International Migratory Bird Celebration May 11 in Fort Collins: rmbo.org. The event includes bird banding stations, activities, and a bike, bird and brew tour.
"It's hard to help them and conserve them if you don't understand their needs," says Levandoski. To do this, RMBO has acquired grants and established partnerships with organizations such as the city of Fort Collins, U.
In order to better understand the birds' migratory paths and preferred wintering grounds, Levandoski says researchers captured and placed tiny radio transmitters on Baird's and grasshopper sparrows. "We have people out in the field every day with an antenna and a headset and they listen for little beeps broadcast by the transmitters."
A newer technology allowed researchers to use geolocators on black swifts. These small light sensors are attached to birds' backs and record daylight length and intensity. "Using calculations similar to those mariners used to make, you can figure out latitude and longitude," Levandoski explains. The instruments do not transmit data, but store information, which is then collected by recapturing birds the next year. Geo-locators are now getting small enough that Levandoski hopes they may soon be used on sparrows.
Grassland birds vary in their migratory ranges. Baird's sparrows breed in North Dakota, Montana and the Saskatchewan areas, flying south to Mexico in the winter. Grasshopper sparrows are much more widespread, shares Levandoski. "We have them on city properties breeding in summertime." These and many other seed-eating birds need a large network of grasslands to exist and thrive. Levandoski says that "Of all the groups of birds on the continent, probably worldwide, grassland birds have been the most affected and have had the most widespread population decline."
"One of the important lessons we've learned," says Levandoski, "is that due to the random nature of where rain falls each year in the desert, it's really important that we conserve a whole network of grasslands. Many of these species seem to shift the bulk of their wintering populations year to year depending on where the rain fell and where grass is in good condition."
RMBO also works closely with ranchers. RMBO connects them with resources and helps provide management plans to make ranching operations more profitable while also providing better quality bird habitat. Changes like rotational grazing, access to water, and understanding the needs of both cattle and birds come into play. RMBO hires wildlife biologists to work with ranchers, arranging voluntary agreements that benefit both birds and land owners.
"Our overreaching goal," shares Levandoski, "is to improve habitat quality for birds and ranchers. We recognize that if a ranch isn't economically viable, it can turn into something else."
The monitoring phase of RMBO's wintering grassland bird project is winding down, and researchers are starting to assimilate their data. Some of the questions they ask involve simple questions with more difficult answers: What kind of grass structure do birds need for protection from predators? What kind of food resources do they need? Are there certain seeds that are more nutritious or easier to access? Levandoski ponders these questions and reviews what they've noted so far. "We have a lot left to learn."
Each month in Outpost, Deborah Huth Price will write about the studies telling us more about the natural world around us.