Monday, February 15, 2016

A flash of blue

By Beth Sullivan
Somehow blue is just more vibrant against the background of snow.
The bright blue is always more intense against the snow.

Our Eastern Bluebird population ebbs and flows during the winter. They do not truly make a big migration, but may move around in loose flocks. A winter walk in the woods will often be enhanced by their warble song and movements through the trees.

Equal opportunity eaters

During the summer season they are mainly insect eaters, catching crickets, grasshoppers and caterpillars on the ground. Occasionally they will convince themselves they are fly catchers and snatch something on the wing. At this time of year they roam the woods, looking for insect eggs, larva and also berries. Many trees and shrubs have fruits that persist through the winter. Sumac is one of their favorites. A good place to look for wintering Bluebirds is a sunny patch of Sumac in an overgrown field. Knox preserve is a great spot; Fennerswood fields and Preston Nature Preserve are others.
Sumac berries persist well into winter.

During the cold times, Bluebirds will spend the night in a communal roost. Often in a nest box along a field edge, there might be a dozen Bluebirds crammed in for warmth. I have witnessed more than 6 Bluebirds flying out of one box, leaving me to scratch my head, wondering. A nest cam would be a great thing!
They are attracted to suet during these cold months, and in my yard, they seem always to show up in February. They can be feisty, defending a suet cage from other birds at some times, but also willing to share with other Bluebirds.
Bluebirds seem willing to share among themselves.

But unwilling to share with strangers.

House hunting time

At this time of the season, they are paired up already and are beginning to look for suitable nest sites. This past weekend, with snow on the ground, we watched a bright male fly to a house at Knox Preserve. He examined the hole, sat on top and sang, brought up a piece of grass, and sat atop the roof waving it around. Relatively easily we spotted the lovely female sitting high in a cherry tree. She watched, warbled back, and flew down to inspect, in and out several times. Then they flew off across the field together, presumably to check out other real estate offerings.
The male checks out the house first. Photograph by Rick Newton.
The soft-colored female waits nearby before passing judgement on a nest site.

Many years they have chosen a nest box, only to be forced out by House Sparrows. These sparrows are not native and are considered invasive. They are not protected by the same laws that protect our native song birds and therefore it is fair game to remove nest material when a house sparrow has taken over. It is also OK to remove eggs. House sparrow eggs are light and speckled. Bluebird eggs are “Robins egg blue” as are most of the Thrush family.
House Sparrows compete for food in winter and housing in summer.

We will be watching our boxes. If Bluebirds arrive we will make every effort to prevent the sparrows from attacking. But it is impossible to be ever vigilant. If the Bluebirds are persistent, they may be well established with their first brood when the Tree Swallows arrive at the end of March and start looking to share the same housing.
Tree Swallows also enjoy the same housing.

On many of our Avalonia preserves, we have made sure there is room for all.

Photographs by Beth Sullivan, unless otherwise indicated.

No comments:

Post a Comment