Vanishing falcons: The mysterious decline of the American Kestrel

North America’s smallest falcon, the American Kestrel, has been at the center of a perplexing scientific mystery for some time now. Researchers across the continent have confirmed a worrying decline in kestrel populations, but identifying the exact cause of their disappearance has proved to be a challenging task. 

A new study published in the Journal of Raptor Research provides a detailed report on the current status of the American Kestrel across various regions. The authors of this vital research, David M. Bird and John A. Smallwood, highlight the complexity of the issue by pointing out that not all kestrel populations are encountering the same obstacles. Some populations are dwindling, others are stabilizing, and a few groups are even rebounding.

Much more research is needed 

The investigation suggests that multiple causes may be contributing to the varying trends in different kestrel populations. Importantly, the researchers emphasize the need for a closer examination of the kestrel’s life cycle, particularly periods outside the breeding season, which they believe has been understudied.

In their exploration of potential contributing factors, Bird and Smallwood present a range of crucial research pathways. These include examining the impact of the Cooper’s Hawks on kestrel distribution and survival, investigating the effects of habitat degradation in the kestrel’s wintering grounds (which often extend beyond U.S. borders), and assessing changes in habitat quality on their breeding grounds.

The experts also recommend examining the impacts of climate change on the availability of prey species for the kestrels, with an emphasis on the importance of grasshoppers as a prey species. Further, the paper calls for research into the possible impacts of rodenticides and pesticides on the health of kestrel populations.

Broader implications of the study

While some theories regarding the kestrel’s decline are put to rest in this study – for instance, the West Nile virus and competition for nesting cavities from European starlings are no longer seen as significant threats – the research shines a light on the broader implications of the falcon’s plight. Raptors, including the American Kestrel, serve as bioindicators, reflecting the overall health of the ecosystems they inhabit.

For their investigation, the researchers largely depended on the contribution of citizen scientists. Four types of data spanning 38 to 55 years were analyzed, including the Breeding Bird Survey, Christmas Bird Count, migration data from two sites located along flyways in the east, and nest box monitoring programs. 

According to Smallwood, the nest box monitoring programs have “generated an invaluable database that allows us to examine not only population trends but also lots of aspects of kestrel behavior and ecology.”

The researchers found that declines in kestrel populations were recorded in 23 of 25 bird conservation regions, with the mid-Atlantic region bearing the brunt of this downward trend. Surveys across Canada reflected similarly high rates of decline. Population increases were observed in only three of these conservation regions, including the Chihuahuan Desert. 

Kestrel decline is a wake-up call 

The intricate interplay of factors causing the decline of the American Kestrel shines a spotlight on the complex realities of conservation. Smallwood emphasizes the gravity of the findings: “The population’s marked decline should be a wake-up call. Something is out of kilter across North American ecosystems, and the problem could be much more widespread than for just this remarkable species.”

The factors contributing to the kestrel’s decline highlight how our actions are impacting wildlife. While no single issue stands as the unequivocal culprit, the cumulative effect of various human activities is making survival increasingly challenging for the American Kestrel.

Despite the stark picture painted by these findings, the experts argue that the scenario is not all doom and gloom. The magnitude of the kestrel’s decline may be lessening, meaning extinction is not the only possible outcome. Instead, we might witness a gradual thinning of the kestrel population across the landscape, resulting in fewer sightings of these falcons.

More about the American Kestrel 

The American Kestrel (Falco sparverius) is the smallest and most common falcon in North America. It’s a bird of prey known for its striking plumage and agility in flight.

Despite their small size, American kestrels are known for their boldness. They’re capable of taking on prey larger than themselves, and are known to fiercely defend their nests against intruders.

Physical characteristics

Kestrels are small compared to other raptors. They typically measure about 9 inches in length, with a wingspan of around 22 inches. They have a slender body and long, narrow wings, and their tail is also long with a notable black band near the end. Males have blue-gray wings, while the wings of females are reddish brown. Both sexes have a distinctive double black stripe on their faces.

Habitat and distribution

The American Kestrel can be found throughout the Americas, from Alaska and Canada all the way down to the southernmost tip of South America. These birds inhabit a wide range of habitats, including meadows, grasslands, deserts, and even urban and suburban areas. They can often be seen perched on telephone wires or fence posts.

Behavior and diet

Kestrels are carnivorous birds that eat a variety of small animals. Their diet consists of insects, lizards, small mammals, and small birds. They have a keen eyesight and often hover in the air before diving to catch prey on the ground.

Reproduction

American Kestrels are cavity nesters, often taking over old woodpecker holes or natural tree cavities for their nests, though they’ll also use nesting boxes if available. The female lays a clutch of about 4-5 eggs, which both parents help to incubate. The chicks are altricial, meaning they hatch in a helpless state and require parental care.

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