Bluebird and Small Cavity Nester Conservation
Sialis - Bluebirds and other small cavity nesters



Mixed Nest

Bluebird and chickadee eggs in same nest.  Photo by Kathy
Black-capped Chickadee female. Photo by Kathy, May 2010

Kathy of NY (AKA nybluebirdfan) photographed this nest with two Black-capped Chickadee eggs and four Eastern Bluebird eggs. It is not known which bird laid the first egg, but it was probably the chickadee, as they tend to nest earlier, and when Kathy first noticed this there were only three bluebird eggs. The female bluebird incubated all 6 eggs. Only the bluebird eggs hatched (on May 6, 2010.)

The nest was a made with dried grass, like a typical bluebird nest, but lined with hair like a chickadee nest. Both species were seen coming in and out of the Gilwood box early on, but the bluebirds eventually won out (as they almost always do.)

I heard numerous reports in early 2010 of bluebirds and chickadees competing for nests - chickadees usually started first, and then bluebirds win.

Sometimes birds will remove the eggs of another species, sometimes not (see In terms of incubation:

  • Eastern Bluebirds incubate for about 12-14 days (can be 11-19). The babies stay in the nest about 17-18 days (can be 19-21).
  • For chickadees (black-capped, assume others are similar) incubation is typically 12-13 days, and fledging is around day 16.
  • So...the timing is pretty similar. In a situation like this, I would not interfere and just let it play out.

Bluebirds seem very attracted to Gilwood boxes. Chickadees also tend to like boxes with a small interior like the Gilwood, the Gilbertson, and a small NABS-style box. There are a number of other boxes available on the property.

If you have birds fighting over boxes, please do try putting up a second nestbox. However, often neither bird wants to give up.


References and More Information:


Pictures of bluebirds and other cavity nesters

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    You cannot begin to preserve any species of animal unless you preserve the habitat in which it dwells. Disturb or destroy that habitat and you will exterminate the species as surely as if you had shot it. So conservation means that you have to preserve forest and grassland, river and lake, even the sea itself. This is vital not only for the preservation of animal life generally, but for the future existence of man himself—a point that seems to escape many people.
    -Gerald Durrell, The Nature Conservancy

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