For the past few winters, I'll occasionally see a few Eastern Bluebirds around our house in SE Minnesota. They seem to come and go at will, never stopping for long. About two weeks ago I located a flock of five that were checking out the bluebird houses along the fence line. They were randomly flying from house to house, inspecting them and doing a lot of chattering. Twice there were "episodes" in which the bluebirds coughed up a pit of some kind. Upon inspection I realized these were the pits from hackberries. I wondered how they could survive on such a limited food supply since during the warmer months they feed on worms and insects.
With nightly temperatures below zero (F), I decided I would give the local bluebirds a treat. I went to the local pet store and purchased 500 mealworms. I placed these mealworms on top of some of the bluebird houses in hopes that the bluebirds would locate them. My first attempts only brought in flocks of Dark-Eyed Juncos who were more than willing to eat the treats I had put out for the bluebirds.
Noticing that one of the bluebird boxes had a number of hackberry pits scattered in the snow underneath, I started to wonder if these birds were roosting in this particular box. One early morning I put out some mealworms on this particular box and within minutes three bluebirds came swooping in for their treat. Success! So I put more of them on top of the box and the same three kept coming back for more. I did this for a few days, but only the three bluebirds were seen.
Then on the evening of January 27, 2009 I went out to bring in some firewood for the stove. It was about 15 minutes after sunset and as I started to load up my wheelbarrow with firewood, there was a lot of chattering going on around the bluebird house where I had seen all those pits. I quickly wheeled the firewood into the house and grabbed my camera gear. Along the fence line and in the trees, chattering away were a lot more than just three bluebirds.
I really didn't know how many there were because they were actively flying between two of the houses. Some going in the houses, some going out. From previous experience I knew that Eastern Bluebirds huddled together in bluebird houses during cold winter nights. A few years back I had driven past the front gate at sunset and had seen three or four vacate a house by the gate. I wasn't however prepared for what I was about to see. I never would have believed that so many birds could fit into one bluebird house.
Without further ado, here is an time edited video showing the Eastern Bluebirds roosting in a bluebird house for the night. The original video is about 17 minutes long. I have taken out the pauses in activity to keep the size of the video as small as possible. Any time a bird entered or left the house, a count will appear in the upper right of the video. (You may need to put the video on pause for a while if using slow Internet connection in order to play the video in its entirety.)