Nature Notes for April 13, 2012
Eastern Bluebirds are truly beautiful birds and we are lucky enough to live in an area where they can be easily seen. The Rice Lake Plains, just south of Rice Lake, are home to a healthy population of this species.
The male of this small thrush is bright blue on the back, with a brick red breast the same colour as a robin’s breast, and white belly. The female is a faded version of the male. They have a gently warbling song.
Bluebirds prefer open habitat with scattered trees. The trees must contain dead snags with old woodpecker holes in them for nesting. They feed on arthropods in the breeding season. They feed their young on insects as the nestlings require animal protein to thrive. Their preferred hunting technique is to sit on a perch to search an area of short vegetation and then drop to the ground to capture their prey.
Before European settlement in Ontario, they probably occurred on the Rice Lake Plains, the savannah around Lake St. Clair and in areas that had been subjected to forest fires. The rest of the province was covered by dense forest which was not attractive to this species.
In winter they form small flocks and feed mostly on fruit. In a winter such as has just passed, many bluebirds remained in this area throughout the winter. The winter was relatively mild, with little snow and an abundance of fruit, some of which is still hanging on vines and bushes.
Bluebirds are secondary cavity nesters. That is, they nest in cavities in trees excavated by other species, mainly woodpeckers. In the mid-twentieth century, their population was in such a decline that they were listed as threatened. There were a number of reason for this decline, but chief among was the competition for nest cavities from two non-native species, the European Starling and the House Sparrow.
Fortunately bluebirds will nest readily in human built structures. Founded in 1978 by Dr. Lawrence Zeleny, the North American BluebirdSociety encouraged people to erect nest boxes in suitable habitat. NABS provided information about bluebirds and their needs and recommended nest box plans for those who wanted to help.
If nest boxes are built with the correct size opening, they will exclude European Starlings. However, a nest box that will admit a bluebird will also admit a House Sparrow, so care must be taken to site nest boxes away from areas that have House Sparrows.
Male bluebirds will vigorously defend their chosen nesting cavity from all competitors. I was recently told of a male who successfully defended his nest box from a starling. He attacked the starling and pinned him to the ground and sat on him for about ten minutes.
Two other native bird species will also compete for these artificial cavities, the Tree Swallow and the House Wren. Since Tree Swallows are semi-colonial in their breeding habits, spacing the boxes 200-300 meters apart will make them less attractive to Tree Swallows. To deter House Wrens, the boxes should not be placed near shrubby habitats or wood edges.
In this area, Hazel Bird started a nest box trail in the Harwood area which she maintained for over 30 years. Due to her efforts, bluebird populations have recovered in this area.
There are two other species of bluebirds, Western and Mountain. The Western Bluebird doesn’t seem to wander outside its stronghold in western North American. The Mountain Bluebird on the other hand, sometimes wanders east. One was found this past winter in Prince Edward County and was seen by quite a few birders.
For more information about bluebirds, refer to the web site of the Ontario Eastern Bluebird Society, oebs.ca or the North American Bluebird Society, nabluebirdsociety.org.