Bluebirds are back — with help from humans

Our abnormally early spring caught many by surprise. Take, for instance, Gary Pelton, who manages natural resources for the Army Corps of Engineers at flood control dams on the upper Connecticut River.

http://www.rutlandherald.com/article/20100523/FEATURES02/5230365               # # # # Bluebirds are back — with help from humans  •  By LI SHEN - Published: May 23, 2010  •  Our abnormally early spring caught many by surprise. Take, for instance, Gary Pelton, who manages natural resources for the Army Corps of Engineers at flood control dams on the upper Connecticut River. In mid-April Gary was cleaning out the 100 or so nest boxes at the Springfield dam, preparing for the expected arrival of bluebirds within a week or two. Unscrewing the front of a box, he was astonished to see a bluebird doggedly sitting on her nest. Undeterred by the giant intruder, she didn't budge. Gently, Gary slipped his screwdriver under the bird and lifted her enough to count five eggs. She remained sitting as he replaced the front of the box.  •  To Pelton and others the bluebird is an icon of spring, one worthy of help. For years the population of these beautiful birds had been declining, but now, fortunately, there are signs of a rebound. Probably the greatest threat they have faced over the years has been competition from European starlings and house sparrows, both of which were introduced to America more than a century ago. House sparrows were brought here in the mid-19th century under the mistaken assumption they would control pests in crops. (In fact, the sparrows ate the very grain they were to protect.) In 1890 starlings were released in America by a Shakespeare fan, who tried bringing to this country all the bird species mentioned in the bard's plays. Both the starlings and the sparrows compete with bluebirds for tree cavities for nesting.  •  The bluebirds' plight led to efforts, begun almost 40 years ago, to provide them with artificial nest boxes. It's relatively easy to make a box that will keep out a starling: all that's needed is a box with an opening too small for them but large enough for bluebirds. House sparrows are more problematic because they can fit through small entry holes.  •  Since house sparrows live around human dwellings, though, situating bluebird boxes far from buildings is one way to discourage them. Another trick is to plug the box entry hole until the bluebirds arrive here in spring. House sparrows stay north for the winter, which means they can grab the best nest sites early in the season. Plugging the holes until the bluebirds come forces sparrows to look elsewhere for homes.  •  A few native bird species, including tree swallows and house wrens, will also take up residence in bluebird boxes.  •  Bluebirds and swallows can co-exist quite well on the same neighborhood, however. This is because most types of birds won't allow other members of their species within their nesting grounds, but they will allow a second species to live nearby. When two nest boxes are placed a few feet apart, territorial swallows are apt to take one, chase off other swallows, and live peacefully with bluebird neighbors.  •  To discourage house wrens, it's best to place bluebird boxes far from the tangles of bushes and brush, where the wrens generally hang out.  •  Bluebirds also are threatened by such critters as squirrels, mice, cats and raccoons. Raccoons, able climbers with long legs and dexterous paws, can reach inside holes or even unlatch a box. Making nest box entrances just one and one-quarter inches deeper by adding an extra patch of wood on the outside can thwart raccoons. Squirrels do not have a long reach, but they can chew. They can enlarge the entrance to suit themselves and move in.  •  Mounting nest boxes on metal poles with an internal diameter of one and one-half inches can keep squirrels at bay and discourage most other marauders. If the nest box is mounted on a wooden post — which bluebirds seem to prefer — consider applying a liberal coating of automotive grease in a 12-inch band beginning12 inches below the nest box. Special barriers or baffles will also work to fend off predators. One approach is to enclose the pole under the nest box with a 2-foot length of 4-inch diameter stove pipe or plastic sewer pipe. Larger four-legged predators cannot climb around this, and a plug at the top end of the pipe will block mice. A 36-inch wide, cone-shaped baffle of sheet metal is effective as well.  •  "Location, location, location" as they say, is key to attracting bluebirds to nest boxes. As a grassland species, bluebirds generally don't like urban or forested places, so they gravitate to open expanses of short grass with a few trees and scattered, knee-high bushes. Boxes should be mounted 5 or 6 feet off the ground. Like other birds, bluebirds are territorial and usually won't nest within 300 feet of another pair of their own species, so multiple boxes should be spaced accordingly. If you offer several boxes, and they all become occupied by bluebirds, consider yourself lucky.  •  A 60 percent or more occupancy rate by bluebirds in a given area signals a need for more boxes, says Pelton, who altogether has helped assemble some 500 boxes at the Springfield and other dam areas. He cleans and repairs them each spring with a small army of volunteers.  •  Pelton had interesting news to report this season: To the best of his knowledge, not one of his bluebirds had to compete with sparrows.  •  Li Shen is an adjunct professor at Dartmouth Medical School and a member of the Thetford conservation commission. This column is illustrated by Adelaide Tyrol. The Outside Story is assigned and edited by Northern Woodlands magazine and is sponsored by the Wellborn Ecology Fund of the New Hampshire Charitable Foundation: wellborn@nhcf.org.  •