By Ken Bevis, Stewardship Wildlife Biologist, Washington State Department of Natural Resources ken.bevis@dnr.wa.gov
Ah spring! The days get longer, the sun comes back, the birds begin singing and flying about, looking for love, and places to nest – like those beautiful nest boxes you put up!
Do you ever go back and check them? Maybe clean out the old nest materials?
How about last fall? Or earlier this spring?
And what about that cracked roof?
Until birds actually start building new nests or laying eggs, there is still time to go in there and remove any old nesting materials and provide a nice, clean cavity.
Larger boxes, like for kestrels or small owls, or even wood duck boxes, are less urgent than the smaller boxes for songbirds. They don’t fill up with material brought in by the residents. However, they can become full of poop and possibly dead things that are good to clean out. Some people will annually look in even their bigger boxes, remove the worst of it and put a new touch of wood shavings or chips in there.
I always wonder about natural cavities; no one cleans them out. (Maybe that’s why woody makes new ones?). I once saw a big cavity in a felled, hollow silver maple that had generations of barn owl use. The layer of pellets, bones, poop and sawdust was probably 16 inches deep! And the owls were still using it. Hmm.
It was suggested to me by my friend (and ace tree-farmer) Scott Ranney, that cedar chips are not optimal for bedding in boxes as some species react negatively to them. Anyone else hear this? Makes sense, however, as cedar is indeed quite volatile in fresh chips and may dissuade some nesters. Old weathered cedar (like in a natural log) is a preferred substrate as testified by generations of pileated woodpeckers and various squirrels.
I clean out my nest boxes in late winter, just before the first migrants arrive. I live in open forest edge country, in the northern mountains. My hypothesis is that sometimes wintering birds (or even squirrels) will roost overnight in the boxes during cold spells, and the old nesting material could provide some insulation (even if poopy) for these hunkered down critters. Hence, remove the old nests just before nesting begins again.
Most importantly is to check them every year, preferably to monitor use, and for maintenance. I did maintenance on my boxes the first week of March. I replaced a broken box, replaced two roofs, remounted one (the tree had fallen over), and scraped poop, feathers and grass out of most.
I keep a journal record of nests in boxes (hard to determine success) mostly for interest, but to remind myself of why I do this. For example, in 2020 we had nests of some kind in 32 out of 34 boxes on our property near Winthrop. The two without birds had wasps! That was a good year. In 2021, we had the heat dome in June, right when many baby birds were in the nest and very vulnerable. Most boxes had nesting attempts (26/34), but several appeared to be only starts (i.e. no eggshells, poop, feathers). There were 13 swallow nests, but seven had dead baby birds in them… dang it! Others in our area reported similar outcomes from the brutal heat. But still, there were six broods of tree and/or violet green swallows that successfully nested in the boxes I provided, and produced young birds that migrated away last fall. Some will undoubtedly return. That feels good.
This year, the bluebirds and swallows are already back. They are flying around checking out my boxes as I write.
Send me a description of your box project and any outcomes you have had at Ken.Bevis@dnr.wa.gov. It’s fun to provide habitat!
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