A field guide to nestboxes

We have had a string of absolutely beautiful spring-like days so far this week. I could’ve spent much of the day out hiking if I didn’t have work I needed to get done indoors. However, yesterday I did take a bit of the afternoon to go out and clean out our nestboxes. Dan heard the first bluebird over the weekend, and it won’t be long before they start checking out nest sites.

I took our cordless drill because there are ten boxes in the fields out back of the house, and another two near the house (and that’s not including the dozen over at the 100-acre woods). Each has two screws holding the faceplate on. If I had to unscrew all 24 screws by hand, and then put them all back in again, I would have a very sore wrist by the end of the session! I just did the “local” boxes yesterday, and left the woods ones for perhaps tomorrow.

When we moved in last summer, much of the nesting season was already done. I noted two of the boxes being active last summer, but didn’t see anyone at the others. I’m not sure when the last time the boxes were cleaned out, because I wasn’t here to do it last winter. Most birds won’t next in a box that’s already got nesting material in it, so if you want to encourage as many active nests as possible, you really need to do it every year. It could be that they were cleaned out last March, and we just didn’t notice anyone because they’d already wrapped up, or perhaps they hadn’t been cleaned for a few winters and that’s why they weren’t used.

I enjoy cleaning boxes in part because it gets me outside on these lovely days, but also for the discovery of who was living in the boxes last year. Quite often it’s a surprise when you unscrew the faceplate and remove it, especially if you weren’t able to observe the occupants while they were using it.

Different species have different styles of nests, so you can usually guess who was living in a particular box based on its contents. Sometimes you can also figure out whether or not the babies fledged, too.

The above two boxes were both used by House Wrens. Wrens build very twiggy nests, using very coarse material for most of the stuffing. It looks like they were being a little over-zealous with their nest-building, but this is their usual style. They prefer for their nest to be near the level of the hole, so they’ll stuff the box with as many twigs as it takes to fill it to reach the hole. Then they arrange the twigs so the cup depression in them is tucked into one of the back corners, and will usually line that with hairs or fine grasses.

This one’s the nest of a Tree Swallow. Swallows have a habit of using large, pale feathers in their boxes (in fact, they like large, pale feathers so much that you can sometimes get them to pluck one from your fingers the way you might feed chickadees from your hand). You can always tell when it’s a swallow nest in the box as a result.

This was one of the two boxes where I saw it in use last summer. These guys fledged in early August, about a month after we moved in.

Here’s the nest after I pulled it out of the box. It’s amazing how well the nests (of most species) will stay together when removed, usually remaining quite square. It’s a little hard to see in this photo perhaps, but the front side of the nest is positively caked with poop. This is from the young birds defecating while they’re perched in the doorway (as above) trying to decide whether they should fly. It may take them a couple of days to work up the courage. Prior to that the parents will remove the fecal sacs from the nest in order to keep it clean. You can usually tell if a nest fledged young because often there will be two or three droppings left behind in the nest, the last ones from the babies before they fledged, which the parents didn’t need to worry about removing.

Here’s another Tree Swallow nest. Just the one feather in this one, but a very similar construction.

You can see the caked droppings on the right side of the nest here, the side that was under the entrance/exit hole.

This was the nest of an Eastern Bluebird. This was the other of the two boxes where we actually saw the box in use last summer:

You can tell the nest hasn’t changed at all, but what’s with all the fluffy white stuff in the winter box? It was plant down, although I wasn’t sure what type. Possibly milkweed, given the abundance of the stuff in our meadows. The seeds of whatever the fluff had belonged to were now gone. To where? This box is near to a couple of small saplings, within jumping distance for a squirrel. The hole’s a bit on the small side for a Red Squirrel, however. I’ve also read that mice will use nestboxes over the winter, but this one was on a pole with a baffle, and I don’t think mice will climb trees and jump. So I’m a bit puzzled about the fluffy down.

I was delighted when I opened this box and discovered this nest. It belonged to a Black-capped Chickadee. I don’t know that I’ve seen inside a chickadee nest before. They cover the bottom of the cavity with mosses, and then the nest itself is lined with soft rabbit or other animal hair.

When I say “nest”, however, I use the term loosely. They don’t build a cup or significant depression like most species do, instead just making a nice soft base that they place the eggs on. I was so delighted by this find that I left the moss there, thinking maybe they’d reuse it, but in coming home and reading a bit more it looks like chickadees won’t reuse their mossy nests, so I’ll need to clean it out when I head out to do the boxes at the 100-acre woods. There was a male singing in the cedars you can see in the background of the previous photo, who may be intending to use the box again this year. Chickadees prefer natural cavities, but won’t turn their beaks up at a nestbox when natural cavities and dead trees are scarce, as they seem to be here.

Finally, I discovered this last box tucked against the wall of one of the outbuildings. I’m not sure when or why it was removed from the fields or wherever it had been, but somebody seems to have found it and liked it. This one I was fairly sure belonged to a squirrel, so I left it there.

The material is strips of cedar bark…

…torn from this log which was leaning against the wall right beside the nestbox. I did some Googling to just confirm that this was indeed a squirrel nest, and in doing so discovered this page at the Hilton Pond Center, a nature centre in the Piedmont of South Carolina. In it he shows a photo of a nestbox filled with cedar bark, just like mine – and notes that this is the preferred nest medium for flying squirrels! I think we have both species around here, although this is near the absolute northern limit for Southern Flying Squirrels, so it’s more likely to be a Northern. This looks like it was or is going to be a natal nest – one used for raising young – as opposed to a roosting nest, which are typically smaller. Now I’m wondering about all that fluff in the bluebird box – could it be a roosting nest? It’s kind of out in the open for a flying squirrel, though.

To say that I was stoked to find this is a bit of an understatement. Although flying squirrels aren’t really uncommon, they’re so rarely seen because they’re nocturnal, so they hold a bit of mystery for me. I’ve only ever seen one, at the lake house last year, which jumped on to our deck railing one evening. I got about a 1.5-second-long look at it in the light cast through the window before it was gone again. How neat would it be to have an active nest here? Even an inactive nest is a pretty cool find, though.