HOLDEN – Bluebirds are often seen near the Fields Pond Audubon Center parking lot, thanks to our bluebird box monitors, volunteers Kathy and Jim Zeman.

While ice and snow were still on the ground, Jim was busy building bluebird boxes. He put up four new boxes within sight of the Nature Center, so that Bluebirds would have every opportunity possible to use our site for nesting.

Over the past few months, Jim and Kathy have checked the boxes on a regular basis and have discovered the following:

Of 29 boxes, 16 had or have nests. Fifteen were tree swallow nests, one had a bluebird nest. On April 29, the bluebird nest was first discovered – a shallow grass, cupped nest, not deep as swallows make, nor feather-lined as swallows do.

On May 5, five pale blue, bluebird eggs were present in the nest. On May 22, five live hatchlings were present, and on June 7, five bluebirds successfully fledged.

According to Jim and Kathy, this was a particularly early and successful fledging, so we are all hoping that this pair of bluebirds will try again this summer. When bluebirds have a second brood in a season, the young from the first help feed the new hatchlings. “We have seen this,” states Jim.

Last summer, the Nature Center had 10 bluebirds fledge, five from each of two nests. An interesting thing about last year’s birds – one of the bluebird nests had five white eggs.

This happens less than 10 percent of the time – usually bluebird eggs are blue, like eggs of their relatives the robins. From the literature, white eggs are not thought to be genetically linked. Offspring from white eggs won’t necessarily produce white eggs of their own. Biologists are not really sure why occasionally eggs are white – perhaps it could be diet.

And just in case anyone is worried about disruption at the nests, routinely checking the boxes does not cause the adult birds to abandon the nest.

Around the country, managers of hundreds of Bluebird House Trails monitor their bluebird nests. Bluebirds tolerate it.

“The swallows almost always dive bomb us. We have found bluebirds almost never do,” says Jim.