Young birds sometimes fall out of their nests before they are ready to fledge. There are several reasons why this can happen, both natural and human-caused. Understanding the causes of premature fledging can help people protect bird populations and individual birds.
Normal Fledging
Fledging is when young birds leave the nest and learn to fly. The age at fledging varies by species, but is often between 12-17 days old for songbirds. Nest departure is a normal part of development. As the nestlings grow, their wings strengthen and they gain independence. The parents encourage fledging by spending less time at the nest and withholding food. This stimulates the young birds’ desire to venture out and develop foraging skills. Fledglings usually remain near the nest where their parents continue to care for them.
Premature Fledging
When birds fledge too early, before they can fly or care for themselves, it is called premature fledging. These fledglings end up on the ground, often in danger. Common causes of premature fledging include:
Weather
Severe storms or prolonged cold and wet conditions can dislodge chicks from the nest. Heavy winds may blow nests out of trees or damage nests and habitat. Young birds forced out by storms are often too weak or undeveloped to survive.
Disturbance
Loud noises, human activity, or predators near nests may startle chicks into jumping or falling from the nest before ready. Nests located near roads, trails, construction sites, or other busy areas are more prone to this. The parents may even take overactive chicks out of the nest if the disturbance is prolonged.
Injury/Illness
Sick or injured chicks may have seizures or lose their balance and stumble out of the nest. Nests infested with parasites can also lead to premature fledging. Weak, starving nestlings may wander in search of food.
Sibling Rivalry
Older, larger chicks may sometimes push smaller or weaker siblings from the nest in order to reduce competition for food from the parents. This is more likely to occur in species prone to siblicide.
Predation
Predators such as cats, raccoons, raptors, or snakes may raid nests and knock out chicks. Even if the predator does not eat them, the fall may be fatal. The parents may also permanently abandon a nest after it has been disturbed by predators.
Structural Problems
Poor nest placement, construction, or disrepair can cause chicks to fall out if the nest tips or collapses. Loose materials may also detach and knock chicks from their nest. This happens more often after storms or long periods of use.
Fledging Accidents
Misjudging distance or hitting obstacles during early flight attempts leads to some fledglings falling. These normal errors of youth become dangerous if the bird ends up on the ground. Collision with windows and fences is another common mishap.
Risks to Fledglings
Grounded fledglings face many perils, including:
– Starvation – Unable to forage or be fed by parents
– Exposure – Small bodies lose heat rapidly
– Predators – Easy targets on the ground for many animals
– Vehicles – Getting hit by cars when on roads or parking lots
– Human Interference – People may unknowingly disrupt the parents’ care
Without quick rescue, most downed fledglings do not survive more than a day or two. Cats in particular can be a major threat to these vulnerable birds.
Why Do Birds Fall Out of Nests?
There are several common reasons why baby birds become displaced from their nests before they are ready to fledge:
Severe Weather
Storms can knock birds out of their nests or blow the entire nest out of the tree or off a ledge. High winds and heavy rain can dislodge nests. Young birds may be bounced out or lose their grip if the nest is shaking in the wind. Cold temperatures can also lead to premature fledging. Babies may wander from the nest in search of warmth if they are exposed without adequate insulation and parent warming.
Predators
Many animals prey on baby birds in nests. Raccoons, snakes, cats, crows, jays, and owls are common bird nest predators. They may physically remove or eat chicks from the nest, causing any remaining to fall out as well. Some predators, like raccoons, also damage or destroy the nest in the process of raiding it, ejecting the chicks.
Human Activity
Loud noises, direct interference, or proximity to human habitats can result in premature fledging. Construction, landscaping, tree-trimming, vehicles, sporting events, pets, music, etc. may startle and disorient chicks. They may stumble from the nest or leap out instinctively to escape perceived danger. Nests located on or near human structures and activity are at the most risk.
Nest Problems
Faulty nest construction or disrepair can compromise the integrity of the nest, leading to accidental falls. Blown down nests, detached materials, holes, collapses, insufficient support or cup shape may all put chicks at risk of falling out. Poor nest site selection like low, exposed branches can also be a factor. Young nestlings have limited mobility and grasping strength to right or save themselves.
Misjumping
As baby birds grow, they become increasingly mobile, active, and curious about the world outside the nest. Some may wander too close to the edge or misjudge distance and accidentally tumble out. This happens most often with top nests but can occur with cavity nestlings that get wedged in an opening. Uncoordinated babies testing their wings may also misjump.
Inexperienced Parents
First-time nesters may choose suboptimal sites or build unstable nests that put their young at greater risk of falling. Younger birds may also be more easily stressed by disruption leading to nest abandonment. Poor parental care can also result in displaced babies if the adults stop attending or feeding the nest frequently.
Siblings
Older, larger nestmates may sometimes push out smaller weaker ones. This rival reduction helps direct more parental resources towards the competitive stronger chicks. Intentional forced fledging occurs in some predatory bird species like eagles and hawks. For songbirds, it more commonly occurs indirectly through competition.
Illness/Injury
Sick or injured babies may have seizures or loss of balance and involuntarily fall from the nest. Young birds weakened from parasites, starvation or dehydration may also lose their grasp on the nest and tumble out. Nestmates may help push out dying chicks to try to prevent contagion.
Undeveloped Senses/Reflexes
New hatchlings have limited vision, coordination, and ability to right themselves or cling to the nest cup. Very young nestlings may accidentally wriggle, roll, or back out of the nest. Their grasping reflex has not yet fully developed to hang on. These helpless chicks rarely survive falling from the nest before 7-10 days old.
Cause | Description |
---|---|
Severe weather | Wind, rain, cold can knock chicks from nests or detach nests from branches |
Predators | Animals like cats, raccoons, snakes eat/remove chicks causing others to fall out |
Human activity | Noises, interference, and proximity to people can startle chicks into prematurely fleeing nest |
Nest problems | Poor construction, disrepair, location can cause structural collapse and accidental falls |
Misjumping | Wandering, curious, testing wings can lead chicks to misjudge and fall out |
Inexperienced parents | First-time nesters make more nest errors that put young at risk |
Siblings | Older chicks may forcibly eject smaller/weaker competitors |
Illness/Injury | Sick babies may have seizures, loss of balance, or be pushed out by others |
Undeveloped senses/reflexes | Very young nestlings may accidentally back/roll out before grasping reflex develops |
Conclusion
Premature fledging from nests is dangerous and often fatal for young birds. However, there are measures we can take to help protect bird families and rescue fallen chicks. Being mindful of nests, reducing disturbance and predators in the area, and properly monitoring vulnerable babies can help prevent many unnecessary nest falls. Quickly reuniting or rehabilitating downed fledglings before parents abandon them increases their chances of survival. With compassionate action and care, we can make a big difference for these fragile young birds just starting their lives.