The first surprising thing about monitoring the boxes is that I don’t actually have many bluebirds. Only one of my nine boxes has a pair of bluebirds in it. They have successfully fledged five young birds this season, and are on their second nest right now. The other boxes are occupied by tree swallows, house wrens, and chickadees, most of which have recently fledged.
Each species I have encountered has a very distinctive nest style, so even if I don’t see any adult birds in the area, I know what species I’m dealing with. Blue birds make neat nests entirely of grasses. Chickadees will lay down a layer of moss, and then line it with fur. Tree swallows create grass nests, and then line them with a layer of found feathers. House wrens nests are the most cacophonous. They pile their boxes full to the brim with twigs, making it hard to get a good count of their eggs and hatchlings. When a pair of house sparrows claimed a nest box, I found a large messy nest made of bits of anything they could find from grasses to bits of garbage.
This is my first time monitoring bird boxes, and I love being out there and seeing the birds grow. Building the nest and laying eggs can take a few weeks for a pair of birds, but once the eggs hatch, it all happens very fast. The hatchlings grow from tiny little dinosaur-like creatures to fledglings ready to leave the nest in the span of a couple of weeks.
I had a slight problem with a pair of house sparrows claiming a nest earlier this season. House sparrows are an invasive species and pose a huge problem to other cavity nesting birds. They are violent protectors of their nests, and are willing to kill native birds in order to take over their nesting sites. I managed to deter the sparrows by removing their nest from the box. My plan was initially just to slow them down and buy myself some time to catch them. I fully expected to return the next week to find that they had built another nest, and I was ready with a sparrow trap that Peggy Falk (the previous bluebird monitor) had sent me. When I got to the nest box, I found that a pair of tree swallows had built a new nest there. I kept a close eye on that box to make sure the sparrows didn’t return, but I haven’t seen them in the area since. The tree swallows laid two eggs in the box, one of which survived to leave the nest.
I am fascinated with the behavior of the different species of birds I have encountered. Blue birds are very tolerant of me checking the nests. The parents usually vacate the box before I even get close to it, so I don’t see them very often. Chickadees are similar in that regard, but tree swallows and house wrens let me know that my presence is unwelcome. When I check a house wren box, at least one of the parents will hover on a nearby branch and chirp angrily at me until I leave. Tree swallow behavior changes as the nesting season progresses. They don’t seem bothered by me while they are working on the nest, or right after they have laid a clutch of eggs. A week after they lay the eggs though, the mother will not leave the box. During that time, I can’t get an accurate count of the eggs. By the next week, the eggs have usually hatched, and again the parents seem watchful, but unbothered. Once the young are close to fledging, however, the parents get more protective and will swoop around, nearly hitting my head until they’re satisfied that I’m leaving.”
Written by Kaitlind “Kaiti” Fasbury, Blandford Nature Center Land Stewardship Volunteer