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| An adult cliff swallow eagerly picks up freshly exposed mud as construction material to add to a nearby nesting colony |
Recently, Julie (one of our seasonal interns) made the suggestion that it would be neat to capture the very active nest building behavior of a colony of cliff swallows that is currently taking advantage of our pumping on the Rest Pond. Fresh mud is apparently a big draw because a few nights ago I witnessed a few dozen birds in nearly constant motion, roundtripping between the edge of the receding water and the underside of our Route 2 connection to the estuary. (Amazingly, a constant pulse of cars and trucks thundering overhead do not seem to be a deterrent!)
Despite the fact that this went on for literally more than an hour (or at least the part I watched), it was surprisingly difficult to get individual birds in front of the camera, much less find focus. These acrobatic fliers were even targeting specific areas along the waterline, but as soon as they'd settle to the ground, their heads would quickly plunge into the soft muck, and then they would be back on the wing.
This species is the most colonial swallow in the world and that's saying something for a group known to like company. Nesting settlements can number into the thousands out west, but eastern colonies tend to be considerably smaller. If I had to guess, I would say there were 30-50 birds heavy into nest building under the bridge. But again, this is a hard count to make because these things are in near-constant motion!
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| Rarely were there more than a couple birds touching the ground at the same time, but over a one-hour stretch the miniature excavation effort was more or less constant |
At one point, I did manage to focus on an individual with binoculars enough times to see that I could estimate that each individual beakful of mud looked to be about the size of a pencil eraser. This is meaningful when you consider that the average nest takes about 1,000 such pellets to construct. Males and females work together. They have been observed flying literally miles to find mud of the proper consistency. In our case, the colony is just a hundred yards or so from the source, but that still means a lot of individual wing beats to build a single nest.