A while ago I wrote about the marvelous success of the nest box installation program along Putah Creek masterminded by Yolo Audubon’s own Melanie Truan. Over the years, those nest boxes have produced nearly fourteen thousand fledgling Tree Swallows, Western Bluebirds, Ash-throated Flycatchers, House Wrens, and others.
The effort has shown that demand for nest holes far exceeds the natural supply in a semi-wild part of the county. In tamer urban settings, where trees are normally trimmed or removed whenever they show the signs of decay that make for holes, it seems likely that demand is similar or greater. For example, nest boxes in the Davis Cemetery have been essential for bluebird nesting there, and I suspect they have produced the birds that are colonizing east Davis.
This year, an enterprising graduate student at UC Davis, Alison Ke, tested the idea about supply and demand by setting out fifteen nest boxes along a route running from Community Park to Northstar Park in Davis. Half of the boxes were occupied by tree swallows (near Northstar pond) and by bluebirds at several locations.
The boxes are hung from high, horizontal branches and suspended on long, garden-variety planter holders, as protection from predators and vandalism. So, you need a special tool to place and retrieve them.
As it turns out, some kind of protection is crucial. Fellow Auduboner Joe Zinkl and I put up six boxes where we had seen bluebirds last winter in Slide Hill Park and the Wildhorse Agricultural Buffer in Davis. Four boxes went unused. One had a house wren nest, and another received consistent visits from bluebirds–and both were destroyed by vandals! Sober conclusion: if you can’t hang the boxes on out-of-reach branches, put them on out-of-reach property.
Beyond their conservation value, nest boxes are educational, providing unexpected insights about our birds. For example, I was wrong to think there were no bluebirds where Alison Ke put up nest boxes. Again, I thought that the bluebirds around Slide Hill Park were colonists from nearby. But one of the birds was color-banded, and proved to be from the far side of Winters, some fifteen miles away.
Michael Perrone, Conservation Chair, Yolo Audubon