Falcon survival rates surprise scientists amid their decline

North America’s smallest falcon, the American Kestrel, has captivated bird watchers and biologists for generations. Its striking plumage and swift, graceful flight add beauty to skies across the continent.

Yet, despite the kestrel’s visibility and wide distribution from Alaska to Argentina, this tiny raptor has experienced a steady and troubling decline in population since the 1970s.

Scientists have searched for decades to pinpoint the cause. Theories range from habitat loss to pesticide use, but no single factor explains the pattern across all regions. In the Northeast, where kestrel numbers have dropped most sharply, the mystery has deepened.

A new study published in the Journal of Raptor Research brings a rare spark of clarity. It finds that fledgling kestrels in this region are surviving at higher-than-expected rates, which offers an unexpected twist to the ongoing search for answers.

Tracking falcon survival rates

The research involved a comprehensive assessment of kestrel survival. For the first time, researchers tracked both juvenile and adult kestrels across multiple seasons, including winter. This matters because previous studies primarily focused on the nesting season alone.

Breeding kestrels face many known challenges. Raising chicks demands energy, coordination, and suitable nesting habitat. But only a portion of the population actually breeds each year. Many younger birds – those still learning to hunt and navigate – do not yet breed.

These juveniles, along with adults during migration and winter, form blind spots in kestrel research. The current study begins to fill those gaps, offering a more complete picture of the annual life cycle of kestrels.

Falcon survival against the odds

​Dr. Mercy Melo and a team of scientists from Hawk Mountain Sanctuary, The Smithsonian, and the University of Massachusetts Amherst designed a bold field experiment.​

The experts equipped 202 kestrels with lightweight radio transmitters between 2021 and 2023. The team tagged 146 fledglings from across the Northeast United States and 56 adult birds from both Pennsylvania and Florida.

These transmitters recorded each bird’s movements for six months. This time window captured the critical early weeks when juveniles first leave the nest, as well as the overwintering period for adults.

Historically, kestrels experience their highest mortality during these months, especially juveniles who must suddenly survive without parental support.

Yet the findings upended that expectation. Despite lacking experience in how to forage and avoid danger, many fledglings survived remarkably well.

“Our study documented very high survival rates for juveniles across the eastern states, with some sites even boasting one hundred percent survival,” said Dr. Melo. This phase of post-nesting independence had never before been studied so closely, and the data bring both relief and new questions.

Human hazards are the biggest threats

In contrast to the encouraging news about juveniles, adult kestrels faced steeper odds – especially those overwintering in Pennsylvania. These birds showed significantly lower survival rates than their Florida counterparts.

Human-related hazards emerged as the top threats. Confirmed causes of death in adults included collisions with vehicles and entrapment in buildings, both frequent dangers for birds navigating developed landscapes.

This difference between regions suggests winter falcon survival depends not just on climate, but on how much risk the environment imposes. Urbanization, road networks, and even the design of buildings can spell danger for kestrels hunting in low-light winter conditions.

Florida, with its warmer temperatures and possibly fewer urban threats, offered safer overwintering options.

These adult deaths shift focus away from fledglings as the weak link in kestrel survival. Instead, they suggest that certain overwintering regions may present survival bottlenecks, especially for adults already worn down by breeding or migration.

Current data on falcon survival

While the survival rates of fledglings in their first few weeks is promising, their fates after leaving the nesting area still remain unknown.

Once these young birds dispersed beyond the transmitter’s range, they were no longer trackable. This means their survival during migration and overwintering is still a mystery.

However, by confirming that fledgling survival at early stages is higher than assumed, the study helps redirect attention.

If juveniles are doing well in the Northeast, other stages of the life cycle – especially adult migration and wintering – may be where declines are most acute. These findings sharpen the questions that future studies should ask.

“Understanding the factors influencing the American Kestrel population decline will help kestrels but will also improve our understanding of other declining species,” said Dr. Melo. For example, grassland songbirds, which share many habitats with kestrels, face similar pressures and may benefit from similar research.

Deeper significance of the study

American Kestrels may be small, but they play a large ecological role. As top predators of insects, rodents, and small birds, they help regulate populations across open landscapes. The consequences of their decline ripples outward, affecting the balance of local ecosystems.

Moreover, their wide range and relative visibility make them excellent indicators of environmental change. When kestrels struggle, it signals trouble not just for raptors but for entire ecological communities. This is especially true in open habitats, such as prairies, grasslands, and farmlands, where biodiversity is shrinking fast.

“We hope this article entices researchers to adopt collaborative approaches across geographical regions,” said Dr. Melo. That call reflects the study’s deeper significance: kestrels won’t be saved by isolated efforts.

Their survival hinges on better cooperation among scientists, conservationists, and policy-makers who can act across regions and seasons.

A story of falcon survival

This study doesn’t answer every question, but it shifts the compass. The research shows that fledgling kestrels in the Northeast may not be as vulnerable as previously believed.

The study also highlights that adults, particularly those overwintering in human-dominated landscapes, face growing threats.

As research continues, tracking kestrels throughout all life stages – and across all landscapes – will be key. Understanding their migration paths, habitat choices, and human-made hazards will help explain the long-term trends.

The kestrel’s story is still evolving, but this study has brought it into sharper focus. With each new discovery, researchers are getting closer to understanding how this colorful falcon might survive against the odds.

The study is published in the Journal of Raptor Research.

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