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Down to business

It never really feels like springtime until the swallows have returned to the marine lab. This year the barn swallows (Hirundo rustica) came back right on schedule in the last week of March. They have been flying around ever since. I've seen them gathering mud on the banks of Younger Lagoon, but they haven't been very serious about nest building. The cliff swallows (Petrochelidon pyrrhonota), on the other hand, were late arrivals, and I was beginning to worry about them. I didn't see the first cliff swallow until the 1st of May.

Unlike the barn swallows, the cliff swallows immediately started spackling mud on the buildings. There have been a few aborted attempts, but overall they have been very busy little birds. I've been keeping an eye on one nest in particular, as it seems to be the one progressing most rapidly. This nest is located on a building that has been used every year, by both barn swallows and cliff swallows. In previous years I've seen and photographed the nests side-by-side. There isn't any reason to expect them not to nest together again.

So here's what has been going on so far.

The first stage is a simple shelf of mud. The birds are building on vertical walls, but corners where they can use two walls are prime locations. Even a tiny ledge can be used to support those first splats of mud, and once the mud dries it becomes foundation for additional layers. See the mud in the swallow's beak?

Sometimes the birds get this far and then decide to abandon the nest. And sometimes they keep going. Here's what's going on less than a meter away from this nest.

Four cliff swallows building mud nests on wooden walls
Cliff swallows (Petrochelidon pyrrhonota)
© Allison J. Gong

Notice how the birds use their tails as braces so they can cling onto vertical walls. Woodpeckers do the same thing. Of the four birds in the photo above, the two outer ones look like they're just starting to build. I've seen two birds flying in and out of that larger nest, but have no idea whether or not they're the same two birds every time. I suspect they are a mated pair.

The cliff swallow's nest is the gourd-shaped one, with a body that narrows to a much smaller opening just big enough for one bird to pass through. When the nest I was watching got to the stage in the photo above, I thought the opening would be on the left, since there's already a nice curve along that side of the front edge.

I might be kind of right. Today the opening is much narrower, and located off-center towards the left.

Cliff swallow nest on wooden walls
Cliff swallow (Petrochelidon pyrrhonota) nest
© Allison J. Gong

This nest may be finished tomorrow or the next day. It will have taken the birds about a week from start to finish.

Why are there no birds near the nest, you may ask? Well, when I walked out of the building I noticed that all of the swallows were in the air, and nobody was at the nest site. The birds were making alarm calls and flying around, but it didn't look like they were feeding, and none were returning to the nests even for short visits. I looked around and up and found the reason for the swallows' unrest.

Red-tailed hawk (Buteo jamaicensis)
© Allison J. Gong

The hawk was perched directly across from the swallows' nest site, and the swallows were not happy about it.

(For some reason the embedded video isn't working right now. You can watch it from YouTube directly by clicking on that link in the lower left corner.)

Some of the swallows flying around the hawk were barn swallows. I think they are nesting in the breezeway of the building under the hawk. Anyway, the hawk's presence was obviously upsetting to all of the swallows. It hung out for about 10 minutes and then flew away over the field. And immediately, the cliff swallows got right back down to the important business of building a home for the next generation.

What do you think?

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