Walking through the woods the other day, I was saddened to see some bird eggs that had fallen out of a nest. I wondered why they had fallen out, so I asked how birds protect their eggs.
Like any other animal, birds have to reproduce. To protect the eggs until they hatch, most birds construct a nest. The major purpose of the nest is to shelter the eggs from harsh weather and protect the eggs from predation.
If you want to know more about how birds protect their eggs, please read on.
Which animals are threats to bird eggs?
The main threats to bird’s eggs are predation from other birds, reptiles, and mammals. Bird eggs are a great snack for many animals as they are very nutritious. Eggs found on the floor have normally been disturbed by an animal as birds build their nests so that they don’t fall out. Eggs don’t fall out of nests on their own.
Many mammals will eat bird eggs. Stoats, weasels, pine martens, and polecats are part of the Mustelidae family, and all have been known to feed on eggs.
I often see foxes in my area and have noticed them running with eggs in their mouths, taking them away from local chicken farms. Foxes don’t climb trees, so tree nesting birds are safe. However, ground-nesting birds can be a prime target.
Rats will eat almost anything, and bird eggs make a tasty treat for them when they find them. I have also seen squirrels feeding on eggs at the bottom of trees, presumably after pushing the eggs out of the nest.
Other birds will also feed on eggs. Crows will actively search for nests and eggs to feed on, as will other members of the Corvidae family, such as magpies, rooks, and jays. They either eat the eggs in the nest or carry them in their bills.
Cuckoos are also a threat to eggs in the nest. Cuckoos are known as brood parasites. While they do not feed on eggs, the cuckoo lays one of their eggs in another bird’s nest and removes one that the other bird has laid. Once the cuckoo hatches, they will push out the other eggs and birds from the nest.
Snakes also feed on bird eggs. Rat snakes, corn snakes, and fox snakes all feed on eggs as part of their diet. Rat snakes find the nest by watching the birds return home at different times of the day. While most snakes are active during the day, rat snakes will raid the nest at night.
There are many kinds of threats that can cause harm to the nest and the young. Eggs can be affected by extreme temperatures, whether very hot or cold. If the temperature suddenly changes, the eggs may fail to hatch.
Eggs can also be lost out of the nest and fall to the ground, although this only happens if they are disturbed by a predator.
Fires can lead to the widespread destruction of bird eggs in affected areas. In areas where large wildfires occur, large amounts of eggs can be wiped out instantly, leading to a noticeable drop in population.
The impact of climate change has not spared the birds and the nesting process. The climatic conditions observed in recent years are not conducive to an optimal nesting process, and the birds are finding it difficult to adapt to the changes. Some birds may no longer access their usual building materials for their nest due to deforestation, leaving them to seek alternatives.
Do birds defend their eggs?
When they are confronted with a predator, birds are willing to protect their eggs. However, the ability to defend the eggs depends on how determined and strong the predator is. If the predator is too strong, the bird will give up on its eggs and seek another area to make a nest.
Birds will not defend their eggs to the detriment of their own health and can often be seen making another nest when disturbed. If the bird thinks that it won’t be able to defend its young, then it will move on.
Although birds may leave the nest, they often come back to the first nest to check on the eggs or their offspring. The bird comes back, hoping that the nest is not already destroyed and some eggs have survived. Unfortunately, if a predator has been in the nest, nothing is normally left.
Difference between tree-nesting and ground-nesting birds
While many birds make their nests in trees, others build their nests on the ground. Birds that nest in trees provide excellent protection to their young from terrestrial animals. Eggs are protected from any predators which cannot climb the tree.
However, it can also mean that the nest could be more vulnerable to harsh conditions such as storms. Birds that nest in trees usually build stronger nests that are also waterproof to protect the eggs, but in the case of severe weather, a nest higher up can be at risk.
A significant number of birds build their nest on the ground. These include shorebirds and the American Avocet, Sandpiper, and American flamingo. These birds use various strategies to protect their eggs. Some will hide their eggs in clumps of grass, while others lay eggs that match their surroundings.
An example is the Killdeer which scrapes the ground until it is suitable for the female to lay its eggs. This bird uses the camouflage strategy to protect the eggs. Similarly, the American Bitterns camouflage the eggs in the wetlands, as their nests are hard to spot.
Research by Jeroen Renerkeens in the Netherlands found out that the oil secreted by the waders’ preen glands changes during spring, and this plays a critical role in protecting the eggs during ground-nesting. The scent of the eggs is weaker to protect them from mammals that use their noses to find them.
When do birds nest?
The breeding season is when the birds have their eggs or young. Birds that have the most success will lay their eggs when food is abundant.
Crossbills feed on spruce cones, and their breeding season starts in February to take advantage of this. Kestrels will breed in April when small rodents are abundant, while sparrowhawks take advantage of young songbirds in May.
In most of the birds in North America, spring is the start of the nesting season. Ken Keffer, a naturalist and environmental educator, gives the horned owl nest, which starts nesting in January, at least in the Southern States.
How can you help birds to nest?
There are many ways to help nesting birds. If you have a pet cat, try to keep them away from the nest. Always ensure that your cat is wearing a bell. It is estimated that domestic cats kill up to 4 billion birds a year. Eggs are also particularly vulnerable to predation by cats.
You can provide birds with pieces of dry material such as soft leaves, twigs, and grass stems. These can be placed on a flat surface for the birds to take. The pieces provided should be no longer than a few inches to avoid entanglement.
When you provide a nest to birds, stay away from it as much as possible and do not keep on returning. Try not to disturb the birds as this may frighten them away, leaving their eggs behind. Binoculars and cameras are probably the best way to view nesting birds.