Scientists make startling observation about behavior shifts in iconic hawk species: 'High risk'

Scientists have observed dramatic changes in the migration patterns of red-tailed hawks as rising global temperatures and increased urbanization have prompted the birds to adapt.

What's happening?

Red-tailed hawks in Colorado and other states have altered their migratory habits over the past several decades. The birds now seem to prefer to ride out the winters at home or travel shorter distances rather than heading farther south, explained Savanna Henning in the Vail Daily. Henning is a Walking Mountains Foley Graduate Fellow in natural science education and writes a science column for the local outlet.

Warmer temperatures and milder winters in particular are contributing factors, leading some hawks to stay in areas that historically they would have left for the season. In a 2020 post, the Beaverhill Bird Observatory explained that from 1975 to 2011, "the winter range of red-tailed hawks moved northward at a rate of 6 [kilometers] per year [nearly 4 miles] in western North America." And their adaptability doesn't end there.

Henning cited a study from the University of Colorado in noting that the development of wild spaces seems to be at least partly beneficial to this versatile species. Expanding the built landscape has "[created] more of the edge habitat that red-tailed hawks seek out for hunting," as the birds leverage the height of new construction to their advantage when hunting for the small mammals that inhabit adjacent forested grounds.

Still, even the resilient red-tailed hawk can be vulnerable to the threats that urbanization can pose. "Hawks are at high risk of collision with automobiles, wind turbines, power lines, and aircrafts," according to Henning. The use of rodenticides is another danger to the birds as they navigate cityscapes and increased proximity to human activity while searching out their next meal.

Why are these changing migration patterns concerning?

The hawks' migratory shifts have the potential to cause ecological imbalances, such as food shortages in the habitats where a higher number of birds end up staying longer than usual. This could also lead to a "rampant overabundance of rodents and other mammals … in their traditional winter territories," per Beaverhill.

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Controlling rodent populations and other pests is one of the benefits that hawks offer humans, reducing not only crop damage but also the use of harsh pesticides. The raptors can also help curtail the spread of rodent-borne diseases. Changes in where and when the birds hunt could lead to an increase in pollutants and pathogens in affected areas.

What can be done to look out for the hawks?

Henning's column underscores the importance of stepping up observation and tracking efforts so that researchers can learn more about these emerging bird behaviors. Citizen scientists, she says, "can help participate in long-term efforts to monitor changes to red-tailed hawk and other raptor populations" by using an app to record sightings.

To address the root causes driving shifts in migration of not only red-tailed hawks but many other animals, individuals can take action at home to reduce the heat-trapping pollution that is warming wintry habitats. By coordinating at the wider community level, the use of innovations like electric vehicles and solar power has the chance to make a real impact.

On another note, avoiding the use of harsh pesticides to cope with rodent populations can help protect hawks and humans from increased pollutants in water and food systems.