On a recent bird walk around the Montlake Community Center, I spotted dozens of cliff swallows diving to the ground and digging in the mud with their bills. One by one, they took off flying, carrying their mud toward the 520 Bridge.
It was apparent that a large nest construction project was underway. See also: The adaptive reuse of Capitol Hill chickadees. Meanwhile, the bridge is also undergoing some larger-scale work this weekend.
Cliff swallows are slight, graceful birds with blue wings and reddish throats. Like Wilson’s warblers, they recently returned to our region after wintering down south. Now they’re pairing up and preparing for a summer of raising and rearing chicks.
Cliff swallows build nests on the undersides of large horizontal surfaces — like the 520 Bridge — in colonies containing up to a couple of thousand individuals. Because they live in such large groups, they display many complex social behaviors, including cheating. It’s a lot of work to gather and carry all the mud they need for building, so when their neighbors aren’t looking, swallows often steal wet mud from nearby nests.
Interestingly, cliff swallows seem to have benefitted from human expansion. Before people came along, they could only nest under natural rock outcroppings. Now that there are plenty of manmade overhangs to colonize, these birds have greatly expanded their numbers and range.
Because cliff swallows and other swallow species have adapted so well to humans, they’re sometimes regarded as pests. The Seattle Audubon Society provides advice and instructions on living with swallows or, if need be, driving them away from your home. Note that you’re allowed to remove nests when swallows first start making them, but that it’s illegal to disturb nests that are occupied by eggs or chicks.
Interested in learning more?
- Check out this YouTube video of cliff swallows collecting mud.
- For general information about cliff swallows, see their page at the Cornell Lab of Ornithology.
- Visit the Macaulay Library of Natural Sounds to hear the cliff swallow’s call. Check out the first result on this list for a good recording of an individual swallow, and the second result for a recording of several swallows vocalizing at once.
Previous Aviary Posts
- Hill welcomes avian arrivals from the tropics
- An update on the owls of Interlaken
- The adaptive reuse of Capitol Hill chickadees