Bluebird Information
Eastern Bluebird (Sialia sialis)
- The Eastern Bluebird is a member of the thrush family, as is the robin.
- Adult males are a dark blue color on their head, back, wings and tail. They are a reddish-brown color on their chin and breast. Their belly is white.
- Adult females are a duller blueish-gray color on the head, dull brown on their back and blue on the tail and wings. They are a light reddish-brown on the chin and breast. Their belly is white.
- The Eastern Bluebird is found throughout the Eastern U.S. and Southern Canada.
- Eastern Bluebirds in the north will remain as far north during the winter as they can as long as they can find food, water and shelter. The harder the winter, or the more scarce food, water and shelter are, the further south they will migrate until winter breaks.
- Eastern Bluebirds generally return north to the State of New York in early to mid-March.
Nest Box Location
- Bluebirds nest in open fields or orchards. They do not generally nest in cities or suburbs.
- Place the box in as open an area as possible with perches available; do not mount on trees or buildings.
- Keep away from the edge of woods as house wrens will fill them up with sticks.
- Mount the box 4 to 6 feet high on a metal pole. Download the pdf NYSBS Bluebird Nesting Boxes
- Place a guard on the pole to keep out raccoons, snakes and other potential predators. Download the pdf Predator Control on Nest Box Trail.
- Try to face the box opening towards a tree or bush to give the fledglings something to fledge to up off the ground.
- Do not face the box opening INTO the prevailing wind direction.
- Place boxes 100 yards from each other to minimize bluebird territory overlap. This distance can be reduced if there are trees/shrubs/landscape that break up the line of sight between the boxes.
- Consider placing boxes in pairs, either back to back or within 4-6 feet of each other to encourage Tree Swallows and bluebirds to both nest. They will tolerate each other but not pairs of the same species.
- If you don’t get bluebirds in some boxes (or too many House Wrens) after a couple seasons, consider moving them to another more open location.
Nest Box Dimensions
- There are many styles and shapes of bluebird boxes. Some made of wood, others PVC. Some general criteria are:
- Inside dimensions a minimum of 4″x4″ (4″x5″ preferable) for the Eastern Bluebird, 5″x5″ for the mountain/western bluebirds.
- Entrance hole diameter of 1.5 inches for the Eastern Bluebirds, slightly larger for the Mountain/Western Bluebirds.
- Bottom of entrance hole should be approximately 6 inches above the floor
- No perch
- Box should open from top, side or front to allow for monitoring
- Provide ventilation at top of sides and drainage holes in bottom. Download the pdf NYSBS Nest Box Plans
Average Activity Periods
- Courtship – 3 to 5 days
- Nest building – 4 to 5 days
- Egg Laying – starts 1 or 2 days after nest is completed. One egg is laid each day until the clutch is completed. Average clutch size is 4 to 6 eggs. Eggs are clear blue or occasionally white.
- Incubation – starts when last egg is laid, lasts on average around 14 days
- Brooding – starts when eggs hatch, lasts for the first few days to keep them warm until they have developed feathers and can regulate their own body temperature. Stop nest checks after 12 days to prevent premature fledging. Fledging usually occurs around 18 days old.
Nest Box Monitoring
- Try to monitor at least once a week. Keep accurate records each time you monitor
- Stop monitoring 12 days after the eggs hatch. The young *may* prematurely fledge at this time
- Minimize your time at the nest, especially in wet/cold weather
- Tapping on side of box may help flush out brooding parent
- Take note of eggs and nestlings and dates when laid, hatched and fledged
- Remove nest after nestlings fledge to promote a subsequent nesting.
- Bluebirds will nest up to 3 times a season.
- Join the New York State Bluebird Society and/or the North America Bluebird Society. The societies will provide valuable information and contact with birders with similar interests.
- Submitting your data will help monitors understand the bluebirds’ breeding success. Download the pdf Monitoring Bluebird Nest Boxes.
- Submit your nest box survey here.
Competing Species
Tree Swallows, Black Capped Chickadees, House Wrens and House Sparrows may attempt to nest in your box. The first three are tolerable. House Sparrows ARE NOT. Please do not settle for House Sparrows. If you let them breed, you are actually working AGAINST bluebirds and other native cavity nesting birds.
- Tree Swallows: Mount a 2nd box on the same pole or on a pole 4-6 feet away. Tree Swallows will nest in one, bluebirds in the other.
- House Wrens: Move the box out in the open, away from the edge of the woods.
- House Sparrows: Keep removing their nests to deter them. They are a non-native unprotected species so you can deal with them as you see fit. NYSBS has in-house traps which you can order by mailing the pdf Order By Mail form. Utilize “Sparrow Spookers” after first egg is laid to discourage House Sparrows from using the nest box.
- Download the pdf Residential House Sparrow Advisory.
- Another source for in-box traps is Van Ert Enterprises.
Predator Deterrence
- Put a pole guard on the pole to keep climbing predators out.
- Some people grease the poles as well. Recommend using synthetic grease.
- Have the roof of the box overhang the front around 4 to 6 inches to make it harder for predators to reach the entrance hole.
- If birds of prey attack your bluebirds, move the boxes away from trees where the prey birds may be launching their attacks.
- Keep grass/weeds trimmed near box to remove predator hiding spots.
- Deter feral/stray cats. They prey on many bird species.
- Download the pdf Predator Control on a Nest Box Trail.
Food Supply
Bluebirds eat mainly insects that they capture on the ground. They do not eat bird seed. They will eat berries, currants, raisins and mealworms when insects are not readily available.
- Keep some areas mowed to provide ground insects more readily.
- Supply some of the materials listed above in bad weather (early spring, late fall, during winter) to supplement insect food.
- Place materials on a covered, open sided tray.
- Plant native berry-bearing shrubs/trees (holly, bayberry, red mulberry, pin/wild red cherry, American mountain ash).
The NYS DEC sells berry producing seedlings each spring. Visit their website here.
For a list of native trees/shrubs bluebirds are known to utilize for food download the pdf Plantings for Eastern Bluebirds.
Wintering Over
Bluebirds will winter over if the weather does not get too harsh and they have (1) shelter, (2) food and (3) water.
For shelter, bluebirds will roost in empty nest boxes. You can add clean dried grass or pine needles in the fall, if you wish, for bedding material. You can also plug up air vent holes to help prevent heat loss. You can also build or buy roosting boxes. Download the pdf Roosting Box Plans.
For food, you can plant berry bearing trees and shrubs so the bluebirds will have fresh food available. They also eat raisins and currants. Mealworms are another option but they are expensive. Two sites recommended by the North American Bluebird Society for the purchase of mealworms are: Grubco and Nature’s Way.
Bluebirds can also be fed suet mixes. For some successful mixtures download the pdf Winter Food for Bluebirds.
Only use peanut butter in a mixture, not alone, as it may stick to the birds’ crop.
For water, you can put fresh water out daily if there is not running water available. There are also products available to heat or vibrate the water to help prevent freezing.