Housing stock is at a premium if you’re a Tree Swallow at the Montlake Fill. Tree Swallows are cavity nesters, meaning they need to build their nests in tree holes, but they are unable to excavate their own holes. They depend on woodpeckers and insect-borers to create the holes in dead snags, and at the Fill, there just aren’t that many snags with holes in them.

To alleviate the housing shortage, the Center for Urban Horticulture folks have been putting up nest boxes on short poles in the North Blue Forest and in Kern’s Restoration Pond habitat near the Dime Lot (E-5 to people under the age of 50).

To my eyes, the nest boxes look far more inviting than a hole in a dead tree, but the Tree Swallows think differently. Their favorite choices are the holes in the small snag on the south edge of the Southwest Pond. Every year, there is a fight over who gets these holes.

This year, though, looks to be a little more peaceful. For one thing, the snag broke off about halfway up, so there is less real estate to argue over. For another, two Tree Swallows showed up on February 19, well ahead of the other lookey-loos, and immediately claimed the second hole from the top. Other early arrivals are quickly claiming the rest.

More Tree Swallows are appearing every day, so the market in nest boxes will be brisk over the next few weeks. I’m keeping my eye on the home that’s always last to go. It’s a ramshackle affair just north of the Southwest Pond. A real fixer-upper for the right bird, perhaps, but no self-respecting female Tree Swallow would look twice at it. It leans over worse than the Tower of Pisa – so much so that any egg laid in the box would immediately roll right out again. Last year a little male was perched on the roof, singing for all he was worth. I had to admire his heart but wondered where he kept his brains.