Date: 4/7/17 2:58 pm From: Frank Enders (via carolinabirds Mailing List) <carolinabirds...> Subject: Bluebird roosts on branch of 16' oak for 2 months
Around January 25th I flushed a bluebird from a small red/black oak on the south side of a barn. Judging from the guano deposits on the ground, this bird had been roosting for a week or two, probably since I stopped working the chicken house for the previous flock of broilers.
The roosting spot was ten feet up in a 16 foot tall tree, some 5 feet east of the southwest corner of the barn, which had vertical 8' sidewall, then sloped up to about 25 foot peak. The tree had several hundred dead leaves on it all winter, the roosting bird visible with difficulty.
I tried to avoid chasing the bird away, but noticed it several times at dawn or dusk, when I was walking around the corner of the barn. I tried to go by only in full daylight or well after sunset. One day I saw two birds in the area, not yet on the roost. I supposed this roosting bird, which was a male, was "guarding" a bluebird box (with an Elizabethan aluminum collar against blacksnakes) 200 feet west northwest from the roost tree. I was surprised to find no evidence of nesting in that box, though it had regularly been used in previous years.
The last time I saw the bird or fresh guano was the evening of March 24, 2017. I am a bit amazed the bird roosted in one spot for 5 weeks. This is a dark place, as I use no security lights, but in March I had a feed truck here at least once a week, though probably only at night half the time. The trucks might shine a light on the bird as they turned around in the barnyard, as also if I drove home after dark, my car's headlights might illuminate the roost momentarily.
Since the bird has not been seen at the roost site, a pair of bluebirds has been hanging around my martin gourds, which happen to be a bit low (my martins not here yet--neighbor had about 10 10 days ago). Bluebirds have nested in a gourd every so often, even when martins occupied many.
While rains would wash away the guano deposits, it seemed to me that a possum might detect such deposits and then climb to eat any roosting passerines.
I write this partly because a man noosing and banding Saw-whet Owls in New Jersey told me he had a poodle which would alert the bander to roosting Saw-whets they had bypassed. Clearly the scent of the owl pellets gave the owl away to the dog.
This was next to the Delaware River, near where sludge dredged from below the Philadelphia sewage treatment plant had been dumped, such that there was rich weedy growth and presumably an abundance of mice for the owls.