Earlier this November, I watched several Eastern Bluebirds feeding in Eliza Howell Park, birds that were probably on a brief stopover during their southward migration. This observation started me thinking about my other observations of this species over the last 15 years.
The difference between the female and male Eastern Bluebird can be seen clearly in these two photos by Margaret Weber. The female is shown first here.
Eastern Bluebirds were in serious decline throughout their range last century (especially from about 1920 till about 1970). They are insect eaters and a secondary cavity nesting species. Unable to make their own nesting holes as woodpeckers do, they need to find existing cavities. There were many reasons for the decline, including pesticide use, removal of dead trees, habitat change, etc. In addition, European Starlings, an introduced species that is also a secondary cavity nester, was much more aggressive about claiming tree cavities.
In the last 50 years, however, Bluebirds have gone from being endangered to being a conservation success story. One part of the turnaround has been the widespread use of Bluebird nesting boxes, made with an opening that is large enough for bluebirds but too small for the larger Starlings. Thanks to a birdbox making project of Sidewalk Detroit, there are now a couple such boxes in Eliza Howell Park.
Fifteen years ago, I did not usually see Bluebirds in the park during the breeding season. Now I have seen them in most of the last 10 breeding seasons and they have probably been nesting here for several years (though I have not been able to make positive confirmation until recently).
The nesting box shown above was placed in the Spring of 2018 and has been used by Bluebirds both last year and this year. They usually have 2 broods per year, typically in the same nest. Note the evidence of the frequent use of the entrance hole.
In late April this year, while the female was away from the nest, I put my camera in the box and took a quick picture.
Recently, after nesting was finished for the year, I opened the box to clean it out for them to use again next year. My guess is that they added more nesting material after the first brood.
The feather confirms the species that used the nest, if there were any doubt.
Eastern Bluebirds migrate each spring and fall, but do not go very far south. Southern Michigan is at the northern end of the winter/year-round range. I occasionally see one or two in the winter in Eliza Howell, but I don’t really expect to see them again until March. (The range map from the Cornell Lab of Ornithology.)
In addition to helping bluebirds find “housing,” nest boxes provide a good opportunity for bird watchers to see these lovely birds. Bluebirds need some open area (ideally something like a field with scattered trees) for their insect hunting. They are not likely to nest in small urban backyards, but Eliza Howell is now one urban location where there is a good chance to watch them in the spring and summer.
The next photo, also by Margaret Weber, taken at a different location, suggests some of the pleasure in Bluebird watching in nesting season.
Eliza Howell Nature Walks 