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 door 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.
BREAKING NEWS RE: SPARROW CONTROL
There has been great success overseas with the use of Monafilament (fishing) line strung infront of the entrance hole to deter sparrows. Sparrows flutter before entering the hole and catch their wings on the fishing line, where the blue birds can fly straight in to the hole. There is also a thought that the sparrows eye site is not as good as the bluebird and that the 8lb fishing line is hard for them to see. This year, due to the limited nesting of Bluebirds from March to May, the Bermuda Bluebird Society have installed fishing line on almost all of our boxes. The majority of our boxes have the 2 vertical fishing line design seen on the websites below:
Following the measurements of the websites above, we used four 1 1/2 " nails and tightly wrapped 8lb fishing line around the nails.
St.Georges Golf course in April 2012 had five boxes with a more extensive fishing line pattern (added horizontal lines, seen below) in front of the hole and all had blueirds nesting where all the other boxes had sparrows.
PLEASE NOTE: WE ADVISE ONE CUT THE FISHING LINE AWAY WHEN THE BLUEBIRD CHICKS ARE ABOUT 10 DAYS OLD SO WHEN FLEDGING FROM THE BOX THEY HAVE NO CHANCE BEING CAUGHT IN THE FISHING LINE.