Fewer bluebirds this year

Upon monitoring 469 birdhouses on 38 different lines three times between May and August, it was recorded that 241 bluebird nestlings fledged while 654 tree swallow nestlings fledged.
There also were some moralities recorded, including 19 bluebird chicks, 44 bluebird eggs, 72 tree swallow chicks, 29 tree swallow eggs, and six adult tree swallows.
Two lines do need special mention. The 10 birdhouses by Crossroads School in Devlin, which generally are used by two pairs of bluebirds and at least six pairs of tree swallows, have been taken over by house sparrows.
This year, no bluebirds and only two pairs of tree swallows were there.
Four boxes contained house sparrows. A male sat on top of the empty boxes ensuring that no other birds nested in them.
A second line of note is Line #1 on one side with 10 birdhouses. In 2005, the willows were sprayed with Roundup. No birds were able to raise young that year, although attempts were made to do so.
Two dead adults, several rotten eggs, and many dead nestlings were found in the boxes that year. In 2006, a few birds fledged their young.
This year, it’s almost back to normal—two pairs of bluebirds and four pairs of tree swallows. Box #9 had broken eggs and the rest were empty.
Even though there are more birdhouses this year, there were fewer bluebirds and tree swallows occupying them.
Since West Nile virus does infect bluebirds, according to reports from the U.S., this could account for the lower populations. But that’s just one possibility. It also could be a natural cycle.
Mortality was much greater in 2007 than it has been in the 17 years of the bluebird project.
Wrens and house sparrows, whose numbers have risen rapidly in the last two years, have taken over many of the birdhouses. Wrens fill up several boxes with twigs when they stake out their territories.
They even fill up houses that have bluebird eggs in them. The bluebirds have to start over again elsewhere.
House sparrows drive others birds away.
Since most of the birdhouses where monitored three times from May to August, it was recorded most birds fledged between June 20 and July 3.
In the fall, the local “Get Outdoors” club cleaned out most of the bird boxes.
There are other volunteers for monitoring. Shirley Morrish, along with Julianna and Nick Donaldson, do two lines, Julianna and Nick do another line, Lisa and Danielle Gregory monitor three lines, and Justin Donaldson does two lines.
In addition, Henry Van Ael, Ilka Milne and sons, Adam and Arthur, have two lines while Tony Elders monitors the line near his residence.
There are 38 lines in total, but there are many other birdhouses throughout the district which school children have made, plus other people set up their own lines.