Male Western Bluebird
Yorba Linda, Calif. (10/13/01)
Western bluebirds are successful on this urban southern California trail
without the need to trap or or kill house sparrows. By using boxes with
two holes, adult Bluebirds can escape from an attack and survive for continued
defense of the box, eggs and young.
Monitors are encouraged to experiment and design a box style that works best for them. It is easy to do. Here are some ideas to get you started:
Note to homeowners who feed house sparrows: Monitors trying to help Bluebirds and other native birds must deal with House Sparrows taking over nest sites and killing native songbirds. House Sparrow problems are usually a result of homeowners feeding and raising House Sparrows.
If you feel you must feed birds, at least be selective and limit your offerings to Hummingbirds/nectar; Safflower (not sunflower) for Finches/Doves; Thistle for Finches/Siskins. Those choices are the least damaging to our environment.
Plans on how to build 2-holed boxes I use on my own trail are given in the
"Construction" link below. Bluebirds have the advantage
over House Sparrows if the battle takes place outside the box. The second
hole allows adult Bluebirds to escape from the box and the majority will win
most battles immediately. There may be a few losses during the initial
"transition" year as Bluebirds gain confidence during battles.
Monitors should place nestboxes to allow two acres forage so that Bluebirds don't have to leave the box unprotected while searching for food. See "Keys to Success" link below for other tips. House Sparrows will use these boxes in the absence of Bluebird competition. It is important for monitors to remove House Sparrow nests and eggs during weekly checks.
The following links include my comments and observations of why each feature was chosen. Almost everything about the box is non-standard according to the North American Bluebird Society. Therefore, quotes from NABS-connected people (the people who influence standards) are included so that grassroots monitors trying to solve problems can make an informed choice.
Too busy to build a box? Contact Linda Violett for availability of old trail boxes (2-holers) or Southern California Bluebird Club for hanging 1-holed boxes.
Below are links to test sites that were used as the
learning tools
to arrive at the "Keys to Success".
Successful test sites were those having only one Bluebird box per two acres
forage and House Sparrow nests/eggs were removed promptly each
week. Large trail monitors should expect a few Bluebird losses during the
first "transition" year as Bluebirds learn to use the escape hole. The best test site
to study is the first one set up by Shari Kastner of New Berlin, Wisconsin.
It involves only one box but it is a great example of a site with both House
Sparrow and House Wren problems.
Bluebirds need two acres of forage to feed a clutch of chicks. Extra boxes within that territory is an invitation for House Sparrows to move in and cause problems.
Female Western Bluebird
10/13/01; Yorba Linda, California
Test Site Links:
2008 — 2010 Wisconsin (one box)
2007 Tests - Bet Zimmerman (clustered boxes)
(well spaced) (Large Box Comp)
Female Western Bluebird
(With Wing Flipped Up; 10/13/01)
1998 Year of the House
Sparrows
During 1998 using 1-holed boxes with small 4x4 floors, bluebirds were losing nestboxes
to house sparrows on my trail—constant removal of house sparrow nests and eggs was
necessary at a few sites. Unnecessary nestling deaths were occurring from
overcrowded conditions.
1999 Results:
Oversized boxes ("mansions") with 2-holes were built for House Sparrow problem areas with good results. However, one clutch of Bluebirds was attacked and killed by house sparrows. The adults survived and immediately built a new nest and fledged young. Bluebird adults will use the second hole to escape if the box comes under attack.* Trail management is just as important as nestbox design. Sparrows are not allowed to use nestboxes on this trail, they are never allowed to sit on eggs or young. Bluebirds need 2 acres forage to find insects and boxes should be spaced accordingly.
Initially, boxes were not being built deep enough to protect nestlings from Starlings reaching into the box. Deeper boxes (8" hole to floor drop) with wooden face guards solved the starling problem.
For the 2000 season, old small 1-hole bluebird boxes were converted with 1 1/4" face guard holes and added to some bluebird sites in an attempt to diversify the trail. At a few of these loosely paired sites, bluebirds took one box and house sparrows took the other. These were the only sites where house sparrows were able to get a toehold on my trail. Pairing boxes is an invitation to house sparrows on this trail.
Jays were able to snatch a runt from a first clutch of bluebirds and
came back during the second clutch and could reach in just enough to nip
all of the babies to death. As long as 8.5" boxes are
provided, avian predator/competitor problems are solved.
