Bring Back the Bluebirds Project Update
This has been a challenging and educational season for the Bring Back the Bluebirds Project, as nestbox competition and depredation have become serious and ongoing threats. So far this season, five nests have failed—with a sixth coming close to failing—as a result of these threats, while only two nests have fledged without incident. Although these are known issues in bluebird trails, and our partners on San Juan Island also encountered these problems, we’ve been lucky to escape them in previous years of our work in the Cowichan Valley.
Depredation is a common cause of nest failure for all birds but this year we have discovered that predators are not the biggest threat facing nesting bluebirds in our area: rather, the most danger comes from invasive English House Sparrows. Known to be highly territorial and aggressive, House Sparrows will attack and kill any birds nesting within their territory. As detailed in our last project update, at this year’s first breeding territory, occupied by our first translocated pair of 2014, this is exactly what has happened—twice. We are choosing to share with you a detailed account of one bluebird pair’s struggle with House Sparrows throughout this season. These problems highlight not only a major impact of exotic species but also why it is so important to monitor nestboxes, and why it is better to have no nestbox than to have one that raises House Sparrows.