Violett's Bluebirds . . .

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. This site is dedicated to other bluebird monitors who would like to control house sparrows without trapping and killing them.

Note to homeowners who feed house sparrows: Please do not put any bird seed in your yard which attracts House Sparrows and do not let them reproduce in nestboxes. Monitors trying to help Bluebirds must deal with the House Sparrow population explosion caused by homeowners feeding House Sparrows. House Sparrows viciously kill native birds (including Bluebirds) and take over nesting sites.

Western Bluebirds are declining due to habitat loss, pesticides killing their food source (insects), chemicals, and seed feeders upsetting the natural balance.

All feeders attract rats and, according to Vector Control, are the number one cause of rat infestations. Rats are another reason native birds are on the decline.

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.

Bluebird boxes on the main Yorba Linda trail were cleared of most House Sparrow problems shortly after replacing small 1-holed (standard) Bluebird boxes with 2-holed mansions.

Construction Box Plans
Floor Size
Possible Keys to Success

In an attempt to discover why the trail became free of House Sparrows, tests with 2-holed mansions were done at locations with a history of House Sparrow problems:

2001 and 2002 Tests:

2001 Golf Course (complete) (well spaced)

Purvis 2000/2001 (Large Box Comp)

2002 Tests - La Mirada (clustered boxes)

2002 Tests - Vaqueros (saturated site)

2002 Tests - Fawzi (paired boxes)
2007 Tests - Bet Zimmerman (clustered boxes)

Some of the above test sites had a history of extra boxes where previous monitors followed the common advice to let house sparrows sit on eggs and young to keep them "occupied." House sparrows become easily attached to territories and end up taking multiple boxes (see historical logs using paired standard boxes and PVC boxes at La Mirada). Those areas seemed to carry more house sparrow problems into the following nesting season.

Bluebirds need about 2 acres of forage per box to feed nestlings. For best results, boxes should be spaced no closer than 300 feet from any other Bluebird sized box.. My observations have been that any extra bluebird-sized boxes near a bluebird nest is an invitation for house sparrows to come in and cause problems. This urban trail is surrounded by homeowners putting out millet seed mixtures which attract and maintain high concentrations of house sparrows.

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.

Female Western Bluebird
10/13/01; Yorba Linda, California

2000

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.

2001 - 2007 Results:

— Years of the Wrens —

Old 1-holed nestboxes were retrofitted with small hole guards and hung on the trail in an attempt to help Bewicks Wrens. House Wrens took those boxes and then overflowed into Bluebird boxes causing problems by throwing out Bluebird eggs and stuffing twigs over Bluebird nests. All small boxes were removed from the urban trail during 2005 and it took a few seasons for that mistake to diminish.

Small boxes are still used on my mountain trail and are used by Mountain Chickadees and Pygmy Nuthatches (see links and photos below).

Nest Pictures