During nesting: Unfortunately, sometimes during nesting, a male or female bluebird disappears. It's a tough world out there, and you may never know what happened (see Predator ID and Solutions). You may not even realize it happened, unless you are a backyard bluebirder who recognizes the look and behavior of individual birds (e.g., whether they come to your mealworm feeder or not), or find the dead parent.
Bluebird parents work as a team during nesting season. Females build the nest pretty much by themselves, but depend on their mate to help protect the nest site from predators like House Sparrows, help feed hungry babies in the nest, and feed juveniles for about a month after they fledge. Male bluebirds do not incubate eggs or brood young, but they do feed and protect young, and bring food to the female while she is incubating/brooding, so she can keep the eggs/young warm (especially important during wet or cold weather as very young nestlings can not regulate their own temperature) and protect them.
Sometimes people think one or both parents are missing, when in fact they ARE around! Remember bluebirds lay one egg a day (sometimes skipping a day) and do not spend much, if any, time on the nest until incubation begins. Even then, especially during warm weather, they may be away from the box for extended periods of time. Some males perch on a box, others hang out in trees and are less visible, especially during incubation (perhaps to avoid drawing attention to the nest site). To check for activity, wedge a blade or grass or tiny twig in the entrance hole and check back later to see if it is still there. If the eggs have hatched, parents should be in the box at least every hour or two to feed during the day.
If one of the pair does disappear, it's possible that the remaining parent may find a new mate. That depends on how many unattached bluebirds there are in the area. Sometimes they find a new partner within hours, in a day, sometimes it takes weeks, sometimes it doesn't happen. A lone male may sing forlornly all day long. The new mate may or may not help care for the young. A new male may feed the existing female, or just stuff himself at a mealworm feeder.
On occasion, males are somewhat or very aggressive towards the young of another male (they may swoop at them, chase them or try to prevent the female from feeding, and in one case, the new male removed a small nestlings from the box (but the landlord saw it happen, found and returned the baby to the box and it did survive.) If the second or third brood is affected by a lost parent, the younger siblings may pitch in.
Here are some possible scenarios:
Either Parent Lost:
If a male or female are lost when the nestlings are very small, the lone parent will have difficult caring for them.
If the nestlings are fully feathered (and better able to regulate their own temperature), a widow/widower may be able to successfully fledge all or some of them.
If the babies have fledged (left the box), one parent can care for them, but it is a load. Supplemental feeding can really help, especially during the first week. Occasionally, after fledging a female will leave and pair up with a different male, leaving the original male behind to tend to the fledglings. The male will feed them for about 30 days, after which they can feed themselves. If the male is lost after fledging, the female will do the same, and the young may be okay, but the chicks are very vulnerable once they are out in the world.
If it is a second or third brood, fledglings from a prior brood may help out. If a new female or male comes onto the scene, it is possible they may help or hurt the babies. Unhatched eggs may be abandoned, or a new nest built on top of them. See more info on feeding . See more info on widows/widowers.
Nest sanitation may suffer (especially if female disappears), so consider a nest change if it gets bad.
If a male is lost during egg laying, and the female does not find a new partner, she will likely abandon the nest. However, do not rush to clean out the box until you are absolutely CERTAIN the nest is abandoned. (see cleaning.)
If a male is lost during incubation, the female may successfully go it alone (?) but it will be more difficult without assistance. If she does find a new partner, she may successfully fledge the young.
There are reports of females successfully fledging young that are about 1 week old on their own.
Sometimes the female finds a new mate - the new male may or may not help feed the young (if he does, probably significantly less than the original male. (Meek and Robertson 1991)
If the female is lost during egg laying or before hatching, nothing can be done about the eggs. (See "Can I incubate eggs?") If the male finds a new mate, and she chooses the same box, she may remove the old eggs or cover them with nesting material before laying her own. if you are 100% SURE she is lost, you can remove her eggs. Do NOT do it if you are not sure!
If the female is lost when the nestlings are very young (unfeathered), odds are not too good, as the male does not brood young nestlings. Even if you help with feeding, the babies may get chilled and die. However, I have seen one report of babies surviving when the male disappeared just two days after hatching.
If the female is lost when the nestlings are closer to fledging (at least older than 7 days old), they may make it. I have read of a clutch of 4 that were 10-12 days old surviving with just a male parent when there was plenty of food available.
If the male finds a new female, she may be indifferent to existing nestlings or kill them, or she may feed them (especially if they are not too young or too old.)
If the babies have already fledged, and the male finds a new female, she may distract him from caring for the previous brood.
What you can do to help:
Let the remaining parent raise the young. Nestlings are usually better off with their natural parents. Only a bird can properly teach their young to hunt for food and find water, sing, and defend themselves from the dangers of the natural world.
Eggs: You can NOT incubate abandoned eggs (see why). Do NOT remove eggs from a nest unless you 100% certain they have been abandoned. Do not "foster" eggs into another nest. This can overload the parents, and if incubation has already begun in one nest, they will be out of synch for hatching.
Supplemental Feeding: You CAN help by offering supplemental food (mealworms, chopped raisins, suet crumbles, dogwood berries). This enables the parent to spend more time feeding, brooding and protecting the young. Most bluebirds have to be trained to come to a feeder. A variety of food is best for nestling health and development. If offering mealworms (which can be calcium depleting), dust with calcium. See feeding.
Note: Nestlings of a single parent are lower weight and less likely to fledge, especially if there are more than 4 nestlings. (EKE)
A study by Petit 1991 showed that widowed female Prothonotary Warblers were only able to provide 70% of the food that two adults could provide.
Protect from House Sparrow Attack: If you have House Sparrows in the area, you can always protect eggs and young by putting up a sparrow spooker.
Monitor: In this situation, it is okay to check on the babies once a day to make sure they are okay (monitor VERY carefully after day 13 to avoid premature fledging).
Nest Change: Fecal sacs may pile up in the nest because the parent is focused on feeding. If it gets bad, you can do a nest change.
In a true emergency - i.e., BOTH parents gone, or one parent not feeding at ALL (e.g., for more than two hours of daylight) and babies are cold and listless and are not gaping (not to be confused with older nestlings which hunker down when box is opened), contact a wildlife rehabber specializing in songbirds. Nestlings can live 24 hours without food, after that, time is of the essence.
Fostering: If you are a monitor with many boxes, and have another nestbox with babies of almost or just the same age (within a day or two - ideally the fostered chick is slightly older since it is stressed already), and both parents are dead or only the male remains with very young nestlings (no feathers), you can attempt to foster orphaned nestlings in with another brood. If you don't have many boxes, call another bluebirder or your State/local bluebirding organization to see if someone else can help foster. (This is another reason why it's useful to keep good monitoring records.) This places a load on the parents of the other brood though, so supplemental feeding is a good idea. No more than 5-6 chicks should be in one nest to avoid exceeding the natural capacity of parents to care for the nestlings. Thus chicks may have to be split up between nests. The parents will not discriminate against the fostered young. (Leonard 1995.)
Do not put abandoned eggs into the nest of another bird of the same or different species. For them to hatch at the same time they would have to be at the same stage (e.g., incubation had not begun yet in both nests, or incubation was at the same stage.) Also, increasing the clutch size puts a big load on the parents who will have to feed the young.
Do not put a dehydrated nestling in a foster net - it will die without being re-hydrated. Get it to a wildlife rehabber who knows how to properly rehydrate it without killing it.
Plug up the box after fledging for a couple of days if a widowed female does not pay attention to newly fledged young and only seems interested in starting a new brood with a new mate. Fledglings depend on thir parent(s) for food for 30 days after leaving the nest.s
Gowaty, Patricia Adair and Jonathan H. Plissner. 1998. Eastern Bluebird (Sialia sialis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/381 doi:10.2173/bna.381
Petit, Lisa J. 1999. Prothonotary Warbler (Protonotaria citrea), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/408
A bird does not sing because he has an answer. He sings because he has a song. - Joan Walsh Anglund, A Cup of Sun, 1967
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