Laura Erickson's For the Birds

Thursday, June 17, 2021

Out with the Old and In with the New

Every year, people ask me whether they should clean out old nests after birds are done nesting so that other birds can use them. Old nests can be dangerous for new baby birds. Some avian parasites enter nests via the adult birds or fly in where they sense hot little nestlings. And some of these parasites spend part of their life cycle in the nesting materials, ready to attach themselves to new baby birds when there’s a second nesting. Clearing out all the nesting materials reduces the chances of that. You must be certain that the birds are done with the first nesting before disturbing any materials, though. And as I just learned, birds are quite capable of throwing out old nesting material without our help. 

When my baby chickadees fledged a couple of weeks ago, I knew they were gone for good—chickadees nest only once a year, and to minimize parasite issues, neither the adults nor the chicks ever return to the cavity. I wanted to salvage the nest as a keepsake, and also wanted to know exactly how deep the cavity was. I dreaded the possibility that there might be unhatched eggs or dead chicks in the nest, but that would have been worth knowing. Our cherry tree is so riddled with holes that it wasn’t going to be suitable for digging out a new cavity next year anyway, so Russ was planning to cut the tree down this week. But on Tuesday, a House Wren changed our plans. When I saw him inspecting the cavity, I set up my 300-mm camera on a tripod to get some video. 

House Wren taking over now empty chickadee cavity!

He was focused on two tasks, claiming the cavity for his own in a way that a female House Wren would recognize, and ensuring that the cavity would be a safe place for babies by dumping out all traces of the chickadee nest. When I first noticed him, I saw him toss out two big chunks of the chickadee nest, which fell to the ground at the base of the tree. I wondered how long it would take before he started carrying in sticks—the tangible proof of a House Wren’s claim of ownership. My very first video showed that he was already accomplishing both aims. He flew in with a stick, pushed it through the cavity entrance, and then disappeared inside, popping up to the entrance a few times to toss out fluffy bits of the chickadee nest. Then he flew away to get another stick and repeated the process.

During the time my camera was capturing video, he also brought a forked twig. No matter what he did, he couldn’t get it through the entrance hole. When he gave up, the twig didn’t fall to the ground—one end got stuck in an edge of the duct tape wrapped around the tree below the entrance hole. It is still there two days later despite the rainstorm Wednesday night.

 This male seems to be the wren who is busy with a nest in the little woods at the back of my yard.  Most of the time he sings from back there, but when he came over to the chickadee cavity, he sang a few songs from the cherry tree and nearby boxelder before getting too busy to sing—he only stuck around the chickadee cavity for short bursts of activity before returning to his current nest and chicks. Wren parents share their feeding duties while their young are nestlings, but when the babies in their first nest fledge, the mother usually takes a break while the male assumes all or most of the responsibility for taking care of the fledglings even as he advertises the other cavities he’s maintaining in hopes of attracting a new mate or the previous one if she hasn’t already moved on to someone else. I don’t know how many other cavities he has, so at this point don’t know whether a batch of baby wrens will take their start in the chickadee cavity or not. Nature will take its course, but meanwhile, for the first time ever, I have some very fun video of a busy little House Wren.