It can be alarming for bird watchers and nature lovers to find an empty bird’s nest that once held hatchlings or nestlings. There are several reasons why baby birds may disappear from their nest before they are ready to fledge.
Predators
One of the most common reasons for baby birds disappearing from the nest is predators. Birds have many natural predators, including cats, snakes, raccoons, squirrels, rats, hawks, crows, jays, owls, grackles, and others. These predators may raid bird nests and carry off eggs or baby birds to eat.
Some common bird nest predators include:
- Cats – Domestic and feral cats are prolific hunters of birds, and regularly raid low nests in shrubs and trees.
- Snakes – Rat snakes and other climbing snakes can climb into nests and eat eggs and nestlings.
- Raccoons – With their dexterous paws, raccoons can access many nest sites and prey on eggs and babies.
- Squirrels – Squirrels raid nests for eggs and young birds to eat.
- Rats – Rats are agile climbers and will eat bird eggs and young.
- Hawks – Birds of prey like Cooper’s hawks and sharp-shinned hawks specialize in catching small birds, including young ones in nests.
- Crows & Jays – Intelligent and opportunistic, crows and jays eat eggs and raid nests for nestlings.
- Owls – Powerful nocturnal hunters, owls love prey like small nestling birds.
- Grackles – These blackbirds consume eggs and baby birds in nests.
Birds have evolved to reproduce rapidly to offset losses from frequent predation. But high predator populations near urban areas and habitat fragmentation can decimate nests in some local bird populations.
Weather Events
Severe weather can also cause baby birds to disappear from their nest. Powerful storms, high winds, hail, tornadoes, and hurricanes can blow nests out of trees and destroy them. Nestlings may be displaced or perish in extreme weather.
Torrential downpours can flood nests, chilling the nestlings and killing them. Baby birds have poor temperature regulation early in development.
Hot, dry weather can also overheat bird nests, especially dark, enclosed ones like cavities. The babies may die from hyperthermia.
Nest Parasites
Parasites can also infest bird nests and kill nestlings. Bird nests provide a warm, moist environment that parasites thrive in. Some common nest parasites include:
- Mites – Microscopic mites feed on the blood of nestlings and can weaken and kill them.
- Maggots – Fly larvae (maggots) may hatch in a nest and consume nestlings alive.
- Fleas – Fleas suck blood from developing nestlings.
- Ticks – Ticks also feed on baby bird blood.
A heavy parasite load drains resources needed for nestlings to grow. It can result in anemia, weakness, and death. Bird parents may intentionally abandon a nest if parasites overwhelm the nestlings.
Disease
Various avian diseases can strike nestling birds and kill some or all of a brood. Diseases like salmonellosis, trichomoniasis, aspergillosis, avian pox, and avian malaria can rapidly spread through a nest. Nestlings have immature immune systems and limited reserves to combat serious infection.
Often the dead nestlings disappear from the nest as the parents dispose of the carcasses. They do this to prevent further disease transmission to remaining brood members.
Starvation
Starvation is another cause of disappearing nestlings. Parents may struggle to find enough food to keep up with the demands of fast-growing chicks. Adverse weather can inhibit insect hatches and other food sources.
If the parents cannot adequately provision the nestlings, the weaker chicks may starve first. Parent birds may remove dead chicks from the nest in this situation.
Competition in the Nest
In some bird species, stronger siblings will push weaker ones from the nest or even kill them. This reduces competition over limited resources from the parents. The dead chicks may be removed by parents or fall from the nest.
Nestmate competition is especially prevalent when food is scarce or there are parasitic nestlings like cuckoos or cowbirds present.
Smaller Broods
While the disappearance of nestlings is often tragic, it is not always detrimental to the whole brood. Having fewer baby birds to feed may improve survival odds for the remaining chicks in the nest.
With less competition over finite resources, the remaining nestlings can grow stronger and healthier. So, a smaller brood size may actually be beneficial if food is limited or if parasites are present.
Nest Abandonment
Sometimes adult birds may outright abandon a nest with babies still inside. This usually only happens when the nest is so heavily infested with parasites, diseased, or experiencing starvation that the parents cannot save it.
By abandoning doomed nestlings, the parents can focus energy on starting a new, healthy brood that breeding season.
Fledging
Of course, not all empty nests represent tragedy. As baby birds grow, they reach an age where they are ready to leave the nest. This is called fledging. Fledglings will leave the nest a few days before they can fly well.
So, an empty nest often means the babies have successfully left to continue their development out in the surrounding branches. Birds fledge at different ages depending on species, from 2 weeks to 2 months old.
Premature Fledging
Unfortunately, some nestlings may fledge too early if they are startled or the nest is disturbed. This can happen from predators, weather events, human interference, etc. Prematurely fledged birds often do not survive long away from the nest.
What You Can Do
If you find an active nest with babies that then disappears, here are a few things you can try:
- Remove predators – Keep pets indoors and use deterrents or exclusion devices to humanely keep away proble predator species.
- Provide shelter – Offer alternative nesting sites or shelters if weather destroyed the original nest.
- Reduce parasites – Clean out old nests and nest boxes to prevent parasite buildup.
- Improve habitat – Provide bird feeders with nutritious foods to help parent birds nourish nestlings.
- Limit disturbances – Avoid visiting nests often or doing work near the nest to prevent premature fledging.
- Contact a rehabilitator – If you find a fledgling in need of help, contact a wildlife rehabilitator right away.
When to Intervene
It can be difficult to know when to intervene if baby birds disappear from a nest you are monitoring. Here are some general guidelines on when to take action:
- Healthy nests – Allow normal predation/fledging if the nest seems otherwise healthy.
- Starvation – Consider supplemental feeding if adults are struggling to find food.
- Bad weather – You may intervene for displaced nestlings if you can safely return them.
- Abandoned babies – Try to contact a rehabilitator if adults abandon nestlings.
- obviously injured birds – Carefully intervene if baby birds need medical aid.
Use your best judgment, and always contact an expert for advice when possible. Avoid directly handling baby birds unless absolutely necessary.
Preventing Disappearances
To help prevent baby birds from disappearing from nests before fledging:
- Keep cats indoors – Cats should be kept inside to prevent predation.
- Deter predators – Use predator guards, bamboo poles, wire mesh, or plastic guards to prevent access to nests.
- Site nest boxes carefully – Choose locations away from prevailing winds, rains, and strong sunshine.
- Clean nest boxes – Keep nest boxes free of old nesting material and parasites between seasons.
- Limit use of pesticides – Chemicals can reduce insects that parent birds need to feed to nestlings.
- Provide emergency shelters – Having some empty nest cups or boxes out provides alternate sites if needed.
Taking some simple precautions can help minimize risks to baby birds in nests in your yard. Always respect nature and avoid unnecessary interference though. The best thing you can do for nests is providing quality bird habitat.
Conclusion
Baby birds disappear from nests for a variety of reasons, many of them natural and unavoidable. Predators, severe weather, parasites, disease, starvation, competition, and early fledging can all lead to nestlings disappearing before they are ready. However, not all cases require intervention. It is best to leave healthy, viable nests be. Keep cats indoors, use deterrents for problematic predators, improve habitat quality, reduce nest disturbances, and contact experts for advice. With care and vigilance, you can help minimize risks to nesting birds in your yard.
