Bluebirds disappear in favour of sparrows when housing densities reach two per acre, the mean housing density in Bermuda today. The House Sparrow nests from February to June. A sparrow nest is an untidy nest made of grass, and trash often wrapping over the top of the nest.
The Bermuda's bluebirds in the past used to have 3 broods a season but because of the aggressive house sparrow competing for nesting boxes it has almost been reduced to one brood in June and July.
Sparrows fit through the same size hole (1 ½ inches) as the bluebird, and as such they often evict bluebirds from nesting boxes killing the young and adult in the process. Many bluebirds are attacked and killed by groups of sparrows. When sparrows occupy your bluebird box, the male sparrow has staked his territory, claimed your nesting box for the season and will continually attract females to his box.
The only way to rid the nesting box of sparrows is to deter the male sparrow from nesting. There are various ways to do this:
- Continually remove the sparrow nest, or wait and remove the eggs and nest.
- Leave the box open for a week or more.
- Take your box down for a few weeks.
- Trap and cull the male sparrow.
If one continually evicts the sparrow and there are bluebirds in your area the bluebird will nest.