Three decades ago, almost no bluebirds were left in Minnesota. A 1979 count put their population at 22 birds. Now the Minnesota Department of Natural Resources estimates their population at around 25,000.
Much of the birds' comeback has been due to a recovery project started in the late 1970s, Carrol Henderson, supervisor of the DNR's non-game wildlife program, told Tom Crann, host of All Things Considered on Tuesday.
Between the 1930s and 1960s, bluebirds lost much of their natural habitat to non-native species like the House Sparrow, which can kill bluebirds and destroy their eggs, according to a spokesperson from the DNR. The Bluebird Recovery Program reacted by building birdhouses with holes that are small enough only for bluebirds or smaller birds to enter.
"We've been teaching people to put out the rest... sort of nest boxes, then how to maintain those boxes on a weekly basis," Henderson said. "The bluebirds need intensive nest box management because if you just have random tree cavities or if somebody puts up a generic nest box that's not specifically for bluebirds, that nest box might be taken over by starlings or house sparrows."
Henderson said the perfect environment for bluebirds is actually golf courses.
"A golf course has good-looking bluebird habitat because they will flit up to a tree, then they fly down to the ground and grab an insect then take it back to the nest to feed the chicks," Henderson said. "If the box is successfully maintained, the bluebirds might nest two or even three times this summer."
This year's temperate winter has been good for bluebirds, but a late cold snap could hurt the population, Henderson said.
"Some bluebirds have already laid their eggs this year," he said. "Normally, they're just starting to build their nests now."