Flights and fancy

RICHMOND, Ky. - When Kent Kessler bought 20 acres outside of town four years ago, he was hoping it was more than just a good site to build a new home.

"I put up a purple martin box that first spring, and by the time we moved in, we had an established colony," said Kessler, a lifelong birder who grew up in rural Jefferson County, east of Louisville, Ky. "My dad and I tried for years to get purple martins to nest on our land, but they wouldn't come."

According to information on the Purple Martin Conservation Association Web site, the birds have specific aerial space requirements. Purple martin houses should be erected in an open spot, 30 to 120 feet from human housing, and no trees within 60 feet should be taller than the bird houses. Having a pond or lake nearby is a plus.

Kessler's colony of about 60 nesting pairs lives in three big bird houses on a hill behind his home, overlooking a hay field and a pond, with no trees nearby. It's an ideal colony site.

The largest member of the swallow family, the purple martin _ Progne subis _ is a fast-flying, 7-˝-inch tall bird that often is confused with the tree swallow. Adult males are dark purple (almost black), and females are lighter, with whitish gray on their breasts.

East of the Rocky Mountains, purple martin populations are completely dependent on humans for nest sites. There are two sub­species in the western states that nest primarily in abandoned woodpecker nest cavities.

TRACKING THE NUMBERS

Each year, purple martins fly thousands of miles a year during their migrations.

"They leave here in early August and fly to Brazil for the winter," Kessler said. "They arrive back in south Florida in January, and back here about March 15, but some birds continue as far north as Canada."

Kessler's kinship with purple martins is more than just admiration. He is part of a continental effort to monitor nesting success, a Purple Martin Conservation Association initiative called Project Martinwatch.

"On last count (June 6), we had 44 nests, 147 eggs and 29 infants produced by the 60 or so nesting pairs in our colony," Kessler said.

Statewide, according to PMCA data, there are about 750 purple martin colonies being monitored, and there are about 50,000 known colonies across the United States. Purple martins also nest in Mexico.

Each week during the spring nesting period, which extends into June, Kessler lowers the martin houses and inspects each tray where the birds build a nest, lay a clutch of eggs and raise their young. It takes about 15 days for eggs to hatch, and an additional 26 to 32 days for the young to fledge.

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His children help collect information about the birds in their colony, noting the number of eggs in the nest and the age of the hatched young in each numbered bird house.

Then Kessler reattaches the pole guard (predator shield) and raises the bird houses back up onto their 16-foot poles. This process continues until the baby birds are almost ready to fledge and leave the nest.

Purple martins are completely habituated to humans and don't seem alarmed when their nests are inspected. They fly around while the birdhouses are opened, then they fly back to check on their nests after the box is back on the pole.

Purple martins have some nesting quirks that puzzle birders. "Sometimes they build a dam of mud in front of their nests," Kessler said. "And every time you open a nest, you'll see green foliage in there. Some people think that helps moisten or cool the eggs inside the box.

"There's always a lone adult male that watches over the box when the other birds are away. Each birdhouse is made with its own front porch. That keeps the males separated and prevents them from trying to dominate other nest sites. They can get very territorial."

The nesting reports are e-mailed to PMCA officials.

The weekly census was the subject of a recent field trip for his daughter's second-grade class at Saints Peter and Paul School in Lexington, Ky. The Kesslers also have a bluebird trail of 25 nest boxes on their property, and they have nesting tree swallows.

"Purple martins are wonderful birds," Kessler said. "We know adults come back to the same colony year after year, but the question is, how many come back for how long?"

KEEPING PURPLE MARTINS

In late summer, populations in a local area often congregate, in preparation for their long flight to South America. "I've been to Lake Reba (in Madison County, Ky.) and seen hundreds of martins staging for the migration," Kessler said.

For hundreds of years, purple martins nested in large gourds. Today, many birders erect plastic nest boxes shaped like gourds. "The birds really like that gourd shape. The nest boxes are white to reflect the hot sun and have slide-out nesting trays," Kessler said.

Predators attracted to eggs and young purple martins in the nest include raccoons, rat snakes and owls. "Starlings can be a problem too. They try to nest in the boxes and will poke holes in martins' eggs and kill young," Kessler said.

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Having purple martins around has its advantages, besides an endless aerial acrobatic show. They are insectivores that eat a wide range of flying insects, including flies, wasps, Japanese beetles, cicadas, gnats and moths, "but not as many mosquitoes as people think," Kessler said. "Martins are on the roost (in their nest box) at night when most mosquitoes are out."

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© 2008, Lexington Herald-Leader (Lexington, Ky.).