Bluebirds hatch nearly simultaneously. It takes only about 20-30 minutes for all eggs to hatch. Chicks hatch blind and naked.
Both parents take care of the young and feed them with a diet rich in proteins.
Nestlings grow fast and leave the nest in about 16 to 25 days, depending on the region. After they fledge, parents continue taking care of the fledglings for about three weeks until they become independent.
How long does it take for bluebird eggs to hatch?
The incubation period is variable within the Bluebird’s range lasting 13.5 days on average. Birds in warmer mid and southern states have slightly shorter incubation periods than those in colder northern regions.
The female Bluebird starts incubating the eggs on the last or day before last she lays the last egg. She lays one egg every day but does not sit on them.
The female does all the incubation of the eggs. Once the egg hatch, she also does the young’s brooding until they can regulate their body temperature when they have a coat of feathers.
The male is always around doing different duties. He protects the territory and the nest and brings food to the female while incubating the eggs.
A Bluebird clutch hatches in a short period.
Bluebird clutch of eggs hatches within a period of 20 to 30 minutes.
Field observations indicate that each chick starts the process of hatching 1 to 6 hours before emerging entirely from the egg.
The short time it takes for all chicks to hatch is by design.
The female incubates the eggs for about the same period, which ensures that eggs hatch simultaneously, eliminating the size advantage of chicks that hatch first over those that hatch last.
Blind and mostly naked.
Bluebird chicks at hatch are blind and mostly naked with patches of gray down. They weigh approximately 2.4 gr.
Chicks are “altricial,” which refers to nestlings that stay in the nest and depend entirely on their parents until they become nutritionally independent or can find food for themselves.
Both parents work equally to feed the chicks.
Both parents feed the chicks from day one. As in other birds, chicks open their mouth wide when they sense one of the parents in the cavity.
Studies of the breeding biology of nesting Bluebirds indicate that both parents take about the same number of trips in and out of the cavity.
The same studies noted that during the first week, the female alternates feeding with brooding the young birds as they cannot regulate their body temperature.
After a week, the young birds can regulate their body temperature, and the female does not have to brood them although she spends the night with them.
Parents appear to take more feeding trips and be more active during the early morning hours. The feeding continues in the afternoon but not as frequently as in the morning.
Foods fed to nestlings.
The parents bring crickets, spiders, grasshoppers, butterflies, and moth larvae, as well as berries such as raspberry, mulberry, dogwood, cherry, and honeysuckle.
The diet of nestling bluebirds is high in protein, consisting of approximately 68% invertebrates and 32% berries. A high protein diet helps chicks grow as fast as possible and leave the nest soon.
Photo: Festive Coquette/Flickr/CC by 2.0
Four to 5 chicks defecating in a small cavity would make a big mess, but both parents clean up the cavity throughout the day.
As in many birds, right after chicks are fed, these turn around to present the parent with a fecal sack or pellet. The fecal material is encased in a bag-like gelatinous packet the parent takes with its beak and drops far outside the nest.
When the chicks are very young, parents will eat the fecal sacks, but this practice ends as the chicks get older and are fed a variety of food items.
If one of the chicks dies, one of the parents, when possible, pulls it out of the cavity and drops it outside the nest.
How fast do nestling bluebirds grow?
Bluebird chicks develop fast. After hatching, chicks begin making calls loud enough to be heard when parents arrive with food.
Photo: Putneypics/Flickr/CC by 2.0
Feather begin to grow and replace the gray down by day 2. The nestlings open their eyes by days 5 and 6. By day seven, the chicks have short feathers in most of the body’s back and sides. By day 13, chicks are completely feathered.
By day 13 and older, male and female chicks can be told apart based on their plumage color.
Leaving the nest comes next.
As with the onset of the breeding season, the age at which chicks leave the nest varies with latitude.
Bluebirds in northern portions of the species range start nesting later, take slightly longer to hatch, and appear to take a little longer to leave the nest than birds in southern states.
However, the difference is small.
Across the species range, young Bluebirds leave the nest between the ages of 16 to 21 days after hatching.
Because all chicks hatch at about the same time, size differences among chicks seldom develop. Chicks of the same age and size leave the nest simultaneously.
Parental care after fledging.
Parents and chicks stay together after fledging for about three weeks.
After leaving the nest, young Bluebirds remain in a relative hide for the first week or so. The parents bring food to the fledglings, which are easily located by their persistent calls.
During the first week after leaving the nest, fledglings still depend entirely on the parents for food. They begin practicing flying from place to place.
After the first week, the young birds begin to follow the parents to more open spaces. The young Bluebirds also start performing the typical sit-wait-and-drop strategy to catch invertebrates.
As fledglings gain experience obtaining their food, the parents feed them less and less.
Once fledglings become nutritionally independent, they begin to take trips further and further from the family unit after about three weeks.
Then, they join flocks of juvenile birds that move about in the region.
Field observations have noted that chicks hatched late in the summer may remain with the parents through the winter.
Overall, the time it takes for young Bluebirds to separate from the parents is variable.
Some fledglings stay in the family’s territory for a long time, while others join flocks of juvenile birds and leave the family unit in about three weeks.
Photo: Wendy /Flickr/CC by 2.0
Nestling Bluebirds may face problems.
Studies of nesting Bluebirds noted that when one of the breeding pair dies or disappears after the eggs have hatched, a replacement or adoptive parent may join the bird left in the territory.
The age of the nestlings at the time a member of the pair disappears results in different outcomes.
If an adult dies when the nestlings have a coat of feathers and are approaching the day of fledging, the replacement mate, male or female, will help feed the young.
The study noted that the replacement mate appears not interested in the proper feeding of its adoptive chicks.
If the nestlings are only days old and the male dies, the female may raise the brood even with an uninterested replacement male.
When the female dies while the nestlings are only days old, these are likely to die because the male does not brood the nestling.
A replacement female does not show interest in young adoptive nestlings, and in some cases, she may kill the nestlings to start a need nesting attempt with her as the mother.
Replacing a missing bird in a territory is a way for “floaters” to acquire a territory. A floater is an adult bird ready to breed but does not have a mate or territory.
Older siblings may help parents raising the new brood.
Another observation of these studies was that young birds of the previous brood, still in the parents’ territory, may help feed their younger siblings.
This behavior appears to be rare, and the actual help young birds provide is also in doubt. It may be that young birds do this as a manner of practicing for when they become parents.
- Bluebirds Nests and Eggs: All you Need to Know
- Most Eastern Bluebirds Mate for life, But there is More to It.
- Do Eastern Bluebirds Migrate for the Winter?
- Eastern Bluebird, Life History. All About Birds. The Cornell Lab of Ornithology.
- Gill, Frank (1995). Ornithology. New York: W.H. Freeman.
- Sialis Online. Bluebirds.
- The Birds of the World Online. Eastern Bluebird (Sialia sialis). Cornell Lab of Ornithology, Ithaca, New York.
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