A field guide to nestlings

Checking a nestbox

Yesterday afternoon Dan and I went out with our cordless drill to check the nestboxes in the fields behind the house here. There were ten nextboxes in these meadows, and another seven or eight at the 100-acre woods. We didn’t have time to get over to the latter group. One of the ten here had come unattached at one end and was hanging sideways. I wasn’t too surprised at this as they do seem to be fairly old boxes, but I hadn’t been expecting it. Fortunately, this seems to have happened before anyone got around to using it, but I intend to replace a few of the worst boxes and make sure the others are firmly secured so it won’t happen again.

The remaining nine boxes were all occupied, however. And all of the occupants were birds. This was gratifying for me, since I’d gone to the trouble of cleaning them all out back in March. It was fun to open each up and see who had made it home.

House Wren nestling

The first box we opened was the one that the bluebirds had nested in last summer. We had seen the bluebirds checking it out early this spring, but they had disappeared from that field soon after, and seemed to be hanging about the fields farther back. When we took the door of the box, it was apparent why they’d decided to leave: the box had been taken over by House Wrens. At the bottom of the box was the grassy base of a bluebird nest, and on top of that were the thick twigs that the wrens prefer for their foundation.

The nestlings we found yesterday were all at different developmental stages. This one is about halfway through growing. Its eyes are opened and the feathers are just starting to burst from their waxy sheaths. When I first lifted it out of the box the blue-gray sheen from the sheaths made me initially think “bluebird!” before I realized it didn’t see quite right, and noticed the brown fuzz of the emerging feathers. He’s still naked enough that you can see the big hole that is his ear, behind and about the same size as his eye. Once all the feathers are grown out these holes will be protected by a handful of special feathers with a low density of barbs that allow more sound to pass through.

Four of the nine boxes contained House Wren families. I knew about two of them, the two boxes nearest the house, as I’d heard the two males countersinging from time to time, but I didn’t realize that we actually had four pairs in the area. Most surprising was that the distance between the two farthest apart was only about 330m (1090 ft); four pairs crammed into less than four acres, food must be abundant here. All four boxes had baby wrens, some younger than others.

Tree Swallow nestling

There were two boxes with Tree Swallows nesting in them. The nestlings in the first box were younger than those in the second, and the adults were using a box that had been used by House Wrens last year. Even at this young age you can really see the difference in shape between the different species. The Tree Swallows are noticeably longer, with stubbier beaks, than the House Wrens.

Tree Swallow nestling

The young swallows in the second box were much nearer to fledging, perhaps only a few days away. This one sat alertly but quietly while I took its photo, but this was probably the last day on which it would; any older and it would likely try to make a break for it.

These guys were in last year’s chickadee box. We found a box that had housed chickadees this year, too, though I didn’t get any photos as the young seemed to have already fledged (perhaps they’re the ones I’ve been hearing begging for food in the trees around the house just recently). This year’s chickadees were in a box used by wrens last year. It’s interesting to note how the species all seem to move around, like they’re playing musical nestboxes. I would have thought that the “microhabitat” around each of the boxes would have more of an influence on who chose what box.

Bluebird chicks in nest

We had a sense of which areas the bluebirds might be in, but the first one took us a bit by surprise, as I’d actually thought this box was being used by Tree Swallows, and the one around the corner, which it turns out is being used by swallows, was the one I thought the bluebirds were in. As the chicks get larger it starts to be quite a tight fit in the little nest, and when you look in often all you see is a big mound of feathery bodies. It makes it hard to count how many individuals there are, especially once they’re past the stage of lifting their head to beg for food at any sign of movement. It looks to me like there might be five bluebirds in this box, but we didn’t lift them all out to check.

Eastern Bluebird nestling

The bluebirds are easy to identify because of the blue feathers, and the speckling on the back and shoulders that are characteristic of the thrush family (robins and the spot-breasted thrushes also show these speckles). The male chicks have got these lovely blue tail and wing feathers. Feathers of female chicks will be more grayish, perhaps with just a tinge of blue. I only removed the one chick, above, which happened to be a male, and I’m not sure what the ratio of males to females in the nest was, though I can see at least two males in the nest photo above.

Bluebird eggs in nest

The very last nestbox, at the very back of the property, was the second bluebird. While every other nest we’d check had nestlings (except the chickadee, which was empty), this last nest still contained eggs, the smooth blue-green that’s typical of thrushes (including robins). Tree Swallows have white eggs, and House Wrens speckly brown ones. The grassy lining here is typical of our bluebirds, too.

It’s great to see all the nestboxes being used, and all of the broods doing so well. On our next sunny day I’ll make a trip around to the 100-acre woods and see what’s happening over there, too.

A field guide to nestboxes

House Wren nest in nestbox

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.

House Wren nest in nestbox

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.

Tree Swallow nest in nestbox

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.

Tree Swallow nestling

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.

Tree Swallow nest

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.

Tree Swallow nest in nestbox

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

Tree Swallow nest

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

Eastern Bluebird nest in nestbox

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:

Eastern Bluebird nestlings

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.

Chickadee nest in nestbox

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.

Chickadee nest in nestbox

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.

Squirrel nest

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…

Cedar log being stripped by squirrel for nest material

…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.