Why do Birds Abandon their Nests with Unhatched Eggs
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During breeding season, most birds will stay in or near their nests to protect their eggs and their hatchlings. However, from time to time, you may notice an abandoned nest and wonder why the bird has fled.
Why Birds May Abandon Their Eggs
Birds do not abandon their nests for no reason. They are dedicated parents and will do what they can to protect their young. But there are some instances in which the birds may feel as though abandoning the nest is their only choice. Let’s take a look at why this might happen.
1. It’s Discovered Parasitic Eggs in its Nest
Not all birds want to raise their own young. In fact, some are brood parasites. This is when a bird lays its eggs in another bird’s nest, fooling the host into raising their young. Oftentimes, parasitic chicks will kill their host siblings in order to take all of the food and survive.
Some common brood parasites in North America are the cowbird, the cuckoo, and the black eagle. When searching for a nest in which to lay their eggs, these birds will choose one where the host’s eggs are similar in appearance. In some cases, they may even evict host eggs to make way for their own, fooling the parents into believing they’re raising their own young.
Sometimes, host birds will notice that their nest has been parasitized and will abandon it. They’ll move elsewhere and start all over again. But in other instances, host birds will try to evict the parasitic egg and continue to take care of the current nest.
2. It’s Gone Off to Feed and Will Return Later
Birds don’t stay in their nests indefinitely. While they are there a lot of the time, taking care of their eggs and the chicks once they hatch, they also need to source food and nest materials. Normally, birds can leave their eggs for up to half an hour without incubating them, which gives them plenty of time to run their errands.
On top of this, many bird species won’t actually start incubating their eggs until they have finished laying. A lot of females might only lay one egg a day over the course of several days. During this time, they won’t spend a lot of time at the nest in order to make it less obvious to predators and parasitic birds.
Once an egg is laid, it can be left for up to fourteen days before it needs to be incubated which gives the birds plenty of time to lay their entire clutch. If you don’t see a bird at the nest, this may be the reason.
3. It Felt Threatened
Unfortunately, birds have a significant number of predators. During nesting season, they will assess the situation if they feel threatened, and if it’s serious enough, they’ll abandon their nest in order to start a new one elsewhere.
The bird will determine the number of eggs in the nest and whether they will survive the predatory attack. If they deem it unlikely, they’ll flee. However, this isn’t something they take lightly, in most cases, a minor scare won’t send them packing and it needs to be something that makes them feel very threatened.
In domestic gardens, there are lots of potential threats including humans. Many of us also have pets such as cats and these pose a significant risk to nesting birds. Where possible, it is helpful to our feathered friends if you can keep your pets inside during mating season.
Other animals such as raccoons, snakes, and squirrels, can all cause problems for birds. If you have a bird box then there are pieces of equipment you can buy to make it more difficult for these predators to get in. These include things like metal pieces to cover entrances which will prevent squirrels from chewing their way in or smooth poles to stop snakes from slithering up.
If there are raccoons in your garden, it’s a good idea to keep things clean and tidy. Make sure you keep the lids on your trash cans and never leave food lying around. You can attach predator guards to your bird boxes which will make it more difficult for raccoons to access the eggs.
4. Nest Has Become Infested with Mites
It’s very normal for bird nests and birds to have mites. The two species have developed something of a relationship in that the mites rely on the birds for a blood meal while the birds have evolved strategies to cope with the mites. Some birds will emit a scent similar to citronella which repels the mites while others use methods like dusting and sunbathing.
Mites can live either within the nest material or on the bird itself, sometimes burrowing into the skin, particularly around the feet, legs, and beak.
What’s amazing is that the most common type of mite to attach to birds, haematophagous, have coincided their own breeding period with that of birds. They’ll require a blood meal around every six weeks, but for the rest of the year, they can go without food.
Keeping your nest boxes clean is a good way to eliminate serious mite infestations, but research cannot conclude whether this is beneficial to the birds. In fact, there is some suggestion that the presence of a few mites is a good thing. However, in cases where the nest has become so overrun with mites that it’s impossible to coexist, there may be a chance that the bird will leave.
5. Excessive Noise
Studies have shown that too much noise or light can seriously interfere with the breeding habits of birds. Within this research, it was discovered that birds dwelling in forest locations are more susceptible to excessive noise than those that reside in open spaces. But that doesn’t mean that common garden birds are immune to loud noises.
For example, things you do in your garden that may seem harmless such as mowing the lawn or playing loud music, could cause birds to flee their nests.
In one sad example of humans interfering with bird reproduction, as many as 3000 eggs were abandoned because of the noise from a drone. And this isn’t the only instance of humans impacting birds’ decisions to leave their nests. One study has shown that birds are ten times more likely to flee because of noise and stress caused by humans.
It’s thought that one of the reasons a bird will abandon its nest due to noise is because the sounds in the environment limit the birds’ ability to communicate. For example, the birds are no longer able to effectively hear sounds from other birds alerting them to predators. What’s more, it’s been demonstrated that baby birds born in noisy environments do not develop as well and have a lower chance of survival. It’s then up to the mother to decide whether the reward outweighs the risk.
6. Eggs were Infertile
During mating season, not all female birds will successfully find a mate. However, they may still lay unfertilized eggs. Think about the chicken eggs we eat, these are all laid without fertilization.
One species that lays unfertilized eggs is the pigeon. However, the female doesn’t necessarily know right away that the eggs are not viable, so she will still incubate them for a period of time. It is only when she realizes that they aren’t going to hatch that she’ll abandon them.
Some birds such as the zebra finch or budgie will realize that the eggs are no good and toss them out of the nest before laying another clutch.
There may also be a reduced chance of hatching as a result of inbreeding. This is more common in smaller bird communities, and when the eggs don’t hatch, the parents will abandon the nest.
7. Bird Became Ill or Died
Birds are vulnerable to sickness and death from many places. In a lot of cases, the bird may have fallen victim to a predator. They may also be hit by a car or have flown into a window which is why it’s really important to ensure that your windows are more visible to birds because as many as a billion birds die this way each year in the USA.
When birds die, it’s not uncommon for their partner to abandon the nest and this may also be the case should one of the pair become sick. If one bird is sick, the partnership, which relies on both birds equally contributing, will not survive. It won’t be possible for one bird to take care of the eggs and raise the young alone, so they have no choice but to abandon them.
8. It’s Misplaced It’s Nest
Birds are smart animals, but there may be times that they misplace their nest and can no longer locate it. This usually happens when the nest has been interfered with. For example, if it is blown away during a storm.
How to Tell If a Mother Bird Has Abandoned Her Eggs?
It is very easy to see a nest filled with eggs and no parents around and to assume that the nest has been abandoned. But keep in mind some of the things we have discussed in this article, including the very real possibility that the birds have simply left temporarily to search for food or to wait to lay further eggs.
If you are concerned that a nest is abandoned then there is nothing you can do other than monitor it for a few weeks. It’s a good idea to check on the nest every three to four days but try to avoid doing this when the birds are likely to be most active. Females will typically lay first thing in the morning and will return to the nest for the night, so these are not good times to check.
When looking at the nest, make a note of how many eggs there are and whether any have hatched. If the bird is returning daily to lay a new egg, this will be evident.
If after around four weeks, you notice no changes in the nest and no parents have returned, then there is a very good chance that it has been abandoned. This time frame allows for the potential two weeks that eggs can be left before incubating as well as two week for nesting.
Can You Raise Abandoned Bird Eggs?
Finding an abandoned nest can be an emotional thing for many people. The idea of those eggs hatching without parents around is heartbreaking and this leads many people to want to raise the eggs themselves.
However, raising eggs is not only incredibly challenging, but it may even be illegal. Native birds are protected under the Migratory Bird Treaty Act, and it is an offense to interfere with the nest in any way, including the removal of eggs. There are wildlife rescuers that have permits to remove eggs and tend to nests, but even they would have a hard time raising a wild bird egg.
Let’s imagine that you do remove the eggs and try to raise them, you have to consider the potential that the parents left because the eggs were not viable. In this case, your chances of success are going to be slim to none.
If the birds do somehow hatch then it’s highly unlikely that they’ll survive since humans simply aren’t equipped to provide them with the right diet. Wild birds regurgitate their food for their young and that’s something that we just cannot do. Not to mention that throwing in worms every day just isn’t enough, and many birds need other things like fruits.
How Long Can a Bird Egg Survive Without Being Kept Warm?
Incubation is important for bird eggs as the warmth ensures that the embryo develops correctly. However, since birds don’t always lay their entire clutch in one go, it’s not uncommon for them to wait to incubate until they have finished laying. This could take place over four or five days.
When the egg is initially laid, the embryo inside doesn’t have any vital organs, so there’s no immediate need to keep it warm. In most cases, it can go 48 hours without being incubated, but there are cases where birds will leave their eggs up to 14 days before they start to incubate.
But once that process of incubation begins, it can’t be stopped again. Both mother and father birds will play a role in keeping the egg warm, and how this works depends on the species. In many cases, the birds will take turns keeping the eggs warm.
If they do stop incubating, then the eggs will likely not survive more than a few hours since the embryos will now have their vital organs, and in order for these to develop properly, they need to be kept warm.
