To clean, or not to clean, that is the question!

That’s a line from MacBird, by Shakesparrow.   Sorry, I just couldn’t resist a morning pun.

The cleaning question, however, is a real one.  I’ve had lots of people ask me about it in the past and there are certainly a great many opinions on the subject.  In this context, I’m talking about cleaning out bird houses (not your own house! You should clean that).  For people who put out bird feeders and bird houses, caring for them is always a question.  While there are those people who will put out the houses and feeders and ignore them until they fall apart, there are also others who pull them in and regularly scrub them down.  Since the breeding season is actively kicking off now, it’s an issue that’s been on my mind.

As many of our local birds are territorial, they often return to the same territory year after year to breed.  In doing that, some of the species will even return to the same nesting site.  So…what would they like to find when they get there?  Well, apparently, it may depend on the species.

So, before I get into details let’s do a briefing on the why’s and wherefore’s of the cleaning.  Why clean?  Well, one idea relates to parasites.  There are a great many kinds of external parasites that birds can get.  Adults may be fine with some of them, but young in the nest may have problems growing with a mite infestation in their nest.  Cleaning a nest box out can eliminate the threat of retaining parasites.

Why not clean?  Well, a couple of thoughts on that front relate to the ease of nest-building and the extra insulation that’s provided by previous nest material.  Birds that can construct a nest on top of an old nest may have less work to do and have an easier time controlling the temperature inside the box.

What to do what to do?  The answer, like most things in science, is complicated (and we like it that way!!!).  In a review of the literature, Tomasz Mazgajski found that there really weren’t any clear, universal patterns.  Some birds tend to avoid nest boxes with used material in them.  Others are more drawn to those boxes.  Other species don’t seem to show a preference.

Mazgajski, T.  2007.  Effect of old nest material on nest site selection and breeding parameters in secondary hole nesters – a review.  Acta Ornithologica 42:  1-14

In one table in his paper, he does point out something that might be locally interesting.  Eastern Bluebirds apparently do have a preference for nest boxes with old material in them while European Starlings (which often compete for access to those boxes) have a preference for clean boxes.   Now that’s an important consideration in deciding whether to clean the box or not.  You may be able to tailor your own nest boxes to the birds that you want to see (and I do hope that you vote for the bluebird over the starling).  “Will all great Neptune’s ocean wash this dirt clean from my house?” asks MacBird.  Clearly, the answer is ‘No!’ We want the bluebirds!


About thomasbiology

I'm an Associate Professor of Biology at Queens University of Charlotte with a background in animal behavior with an emphasis in bird song. I've got two secret goals with this blog (well, since I'm sharing them, they're not so secret): 1. To encourage people to look at the natural world around them- not just as a hiking destination, but to notice all the little things moving around them all the time; and 2. To show some of the science that relates to these little things moving around. There's some really fascinating research out there that so few people get to see.
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