Habitat Manager's Dilemma

Thanks to a donation, installation, and encouragement from a local group of bird folks, we added three new bluebird houses to the upper savanna area and have been more diligent in monitoring them. We have felt no angst in years past in removing the occasional sparrow nest from bluebird boxes we have maintained, and have often had at least one bluebird family successfully fledge young.

This year, however, we were faced with a new situation, as shown in two photos immediately below. On April 5, a couple of Carolina chickadee eggs were observed in one of the old nest boxes located in the southwest corner of the savanna. We followed our usual practice when finding eggs of any bird species in a box and left them alone. But six days later, on April 11, the regular check of the box discovered an additional chickadee egg plus five bluebird eggs! This raised the stakes on a decision as to how, or if, to intervene.

April 5, 2012

April 11, 2012

The long term strategy of Habitat Home has been to recreate and/or enhance a few habitat-worthy areas of the property to encourage occupation and success among a wide range of plant and animal species. While we have favored native plant species and removed some non-natives, in particular invasive species, we have generally had no interest in playing favorites. A notable exception has been the introduction of nest boxes, more or less intended to encourage bluebirds. These boxes have been occupied by bluebirds, tree swallows and nuthatches, often resulting in successful families of young birds.

In this case of two native bird species, the question is whether to let nature run its course or if it is better to remove the chickadee eggs. Would we be crossing a line in "natural" selection, intervening in support of not the "fittest" but the "preferred"? Would the chickadee and bluebird compete for nest "rights"? One might expect the female bluebird to begin to sit on the nest and incubate the eggs since she was probably the most recent egg layer here. But if she did, the chickadee eggs would almost certainly hatch first, since they have a shorter gestation time. What would happen then? Would the female bluebird feed the newly hatched chickadees? Would the chickadees destroy the bluebird eggs before they hatched? It's difficult to imagine a scenario which results in all the birds living happily ever after. But hey, this is how it works; I'm sure this is not the first time a nest has been simultaneously used by two birds.

We decided that since we received a donation and installation of nest boxes this year, specifically intended to promote the local bluebird population, that we would intervene and remove the chickadee eggs, which we did on April 12 (see photo below). We expect this to increase the odds of success of any of the eggs (now only the bluebird eggs) to hatch and the young to fledge.

April 12, 2012
(after human intervention)

Addendum 4/23/2012: Following yesterday's post (above), it has been pointed out to me that there are reported cases of birds raising young of different species, or even multiple parents raising young in the same nest. Plus, by removing the chickadee eggs, I have violated both state and federal laws covering protected species, which include chickadees. While I am not planning to turn myself in to the sheriff's office, I will likely not so over-think this issue if it presents itself again. I guess this is what we meant by "challenges and frustrations" in the blog's upper right sidebar introduction.