Bluebirds of San Diego County

Bluebird Basics

male at nest in Agave stalk by R. Seignious Western Bluebird nestlings by V. Elmore

"Bluebirds of San Diego County" website:

To attract Western Bluebirds you need the right habitat such as open forests, parklands with scattered oaks or pine trees, orchards where there is no pesticide spraying, or large mowed lawns with mature trees. They also do well in urban parks, golf courses, and even cemeteries. These open areas with low vegetation allow them to easily see and hunt insects. If you put a nestbox in an area of dry or dense shrubbery and trees, you will get wrens, flycatchers, titmice, not bluebirds. When breeding, Western Bluebirds have territories of about 3 acres and will protect and defend them from other bluebirds. Western Bluebirds do not usually allow other bluebirds to nest within about 300 yards. To reduce territorial fighting, it is better to space nestboxes farther apart than too close together; and place them so that the occupants can't see one another.

There are many different designs for bluebird nestboxes. Choose a nestbox that is made of wood for good insulation from heat and cold, and has an entrance hole of 1-9/16 inches in diameter to prevent non-native European Starlings from using the box. The diameter of the interior floor should be at least 5 by 5 inches for Western Bluebirds. And there should be 6 to 7 inches from the bottom of the entrance hole to the floor to keep eggs and nestlings out of reach of scrub-jays or crows that might poke their heads into the nestbox and try to snatch them. If the wood of the box is very smooth, it is a good idea to cut grooves into the wood below the inside entrance hole to help nestlings get a foothold as they attempt to fledge. The wood should be at least 3/4 inch thick to provide adequate insulation from the sun; pine, cedar, and exterior plywood are all good choices. If you live in areas of the county where summer temperatures are regularly over 90 degrees, then you should add 1/4 to 1/2 inch ventilation holes in the top of the sides of the box; or design a box with 1/2 inch space gaps between the top of the sides and the roof; and consider placing the box where it will get shade from the afternoon sun. The roof should overhang the entrance hole at least 1 to 2 inches to keep out rain and shade the entrance. In order to monitor the box, it will also need to open either from the side, front or top. [Note: The Western Bluebird lays larger clutches of eggs than the Eastern Bluebird, and is a slightly larger bird. Western Bluebirds require an entrance hole of 1-9/16" and an inner chamber of 5" x 5". Eastern Bluebird boxes are smaller with an entrance hole of 1-1/2" and an inner chamber of 4" x 4" - too small for Western Bluebirds.]

Mount the nestbox on a pole under the shade of a tree at a height of 4 to 6 feet, or hang it from a tree branch. Be sure to place the box so that you can easily monitor it regularly

Check your box at least once a week during spring and early summer. Opening the box will not hurt the birds (songbirds do not have a good sense of smell, so leaving your scent will not deter them). Western Bluebirds make neat nests of fine grasses and have 4 to 6 light blue eggs. Record number of eggs, young, etc. Do not monitor the box after the young are 14 days or older as they may fledge prematurely. After the bluebird young have fledged and left the box, remove the old nest and clean out the box. Western Bluebirds usually have two broods (occasionally three) during each breeding season from late March to the beginning of August.

Males sing from a territory to attract a mate. When a female arrives, the male leads her to all the possible nesting locations that he has discovered within his territory. The female will examine each cavity and make the final choice. The male will sing and wing wave while she does this. He also feeds her bits of food. After she selects a site, the female will usually build the nest in about a week while the male guards her. When the nest is finished, the female will lay one egg a day in the morning for about a week. After ALL of the eggs have been laid (usually 4-6), she then begins to incubate them for 13-14 days, taking breaks to go feed. During the week while the female bluebird is egg laying she spends very little time at the nestbox, so if you see eggs and no female around at this time do not conclude the nest is abandoned. Once the young hatch, both parents feed them and remove the white fecal sacs to keep the nest clean. After about 19-24 days, the spotted young leave the nest and fly to nearby trees. They will be fed for a few weeks by the parents until they can catch food on their own.

A water source for your bluebirds is very important. A shallow birdbath will provide water for them to drink, as well as a place to frolic and bathe. Bluebirds eat insects and berries. Plant berry producing shrubs and trees like toyon, elderberry, and nevin's barberry. You can also feed them mealworms (available online and at pet stores) during the breeding season. It is best to put out a limited quantity at the same time each day in a little dish, in the shade near their nestbox and where ants won't get to them.

Competition: watch for non-native house sparrows.
Pests: ants, earwigs or wasps may infest nestboxes.
Predators: cats, scrub-jays, crows and Cooper's hawks can be a threat to bluebirds in San Diego County.
Poisons: many pesticides are toxic to birds and should not be used near nestboxes.

First make sure they are truly abandoned. You need to watch the nest from a distance for at least 1 hour continually; to be sure no parent is coming to the nest. If only one parent appears to be tending the young, it may be able to raise them unassisted. If the male disappears, the female will be able to raise the young, for she will brood them at night. The male bluebird, though, lacks this instinct, and though he will feed the young, he won't brood them overnight. He'll be able to keep them alive only if they are more than a week old, and the weather is warm. If the chicks are warm to the touch and seem well fed, leave well enough alone. Abandoned young may be weak and cold but can survive for 24 hours. Keep them warm and in a dark box and take them immediately to a licensed bird rehabilitator. It's illegal, not to mention very difficult, to raise young birds, which need food every 20 minutes when small. They have a much better chance to survive with someone who has experience. To find a licensed bird rehabilitator, call the Project Wildlife San Diego County Emergency Wildlife Hotline at 619-225-9202.

The Bluebird Book, by Don and Lillian Stokes
Enjoying Bluebirds More, by Julie Zickefoose
Bluebird Activity Book, by Myrna Pearman
(FREE PDF copy at: