Birding at Derby Hill extends well beyond the spring raptor migration. DHBO maintains a trail of 18 bluebird boxes along Sage Creek Drive and at the north lookout. An open field with scattered trees or posts is ideal habitat for Eastern Bluebirds, a cavity nester. However, this close to Lake Ontario, the birds encounter extreme competitive pressure from Tree Swallows, another desirable cavity nester. The nest boxes are paired to help alleviate this pressure; the Tree Swallow will nest in one box of the pair and defend the second box from other Tree Swallows, leaving it vacant for Eastern Bluebirds to occupy.
Nesting started late this year due to a bout of cold, rainy weather. The first Eastern Bluebird egg appeared on May 6 (compared to April 18 in 2012). Two successful nestings at the north lookout fledged 6 young. Tree Swallows laid 53 eggs and fledged 36 young. The spring weather was rough on these aerial insectivores.
The boxes are monitored weekly from March until the final fledging, usually in August. Visitors are encouraged to enjoy the cavity nesting birds, but please do not open the boxes. You may think you are being helpful by removing a House Sparrow nest, but displacing it may only cause the aggressive male to invade another nest box and remove eggs or kill nestlings and/or adults. It is better to leave the nest intact and let the monitor trap and remove the House Sparrow.
If you see a problem with any of these nest boxes, please report it. Better yet, come on up and join in on one of the weekly checks.