Banner Photo: Monk Parakeet by Camilla Cerea

Birds’ adaptation to the human-built environment is not a recent shift in behavior. Between 14,500 to 10,500 years ago, early humans in eastern Jordan began managing wetlands, a practice that in turn encouraged birds to stay rather than migrate.

We tend to view the increasing urbanization of the environment as detrimental to birds, and indeed, habitat loss is the principal reason for the decrease in bird numbers and species. However, in very specific instances, some birds can coexist with the urban environment in beneficial ways – beneficial to them, and to the humans who enjoy them.

What Makes an Urban Bird?

Researchers have described urban-tolerant birds as tending to 1) be smaller, 2) be less territorial and longer-lived generalists in terms of food sources, 3) have larger clutches, and 4) have higher dispersal ability. Other characteristics associated with urbanization include tree- or structure-nesting (rather than ground), and preference for habitats of lower elevations.

Data from eBird were combined with a measure of urbanization (night-time lights) to calculate an Urban Association Index (UAI). Out of 3,768 species studied across 11 continents, there are five species present in the most urban areas – can you guess them? Rock Pigeon, House Sparrow, Barn Swallow, Osprey, and Peregrine Falcon. Of species present in at least ten cities, one of the top five species with the highest UAI was the Monk Parakeet. Of these ubiquitous urban species, only 3 are native to North America: Barn Swallows, Ospreys, and Peregrine Falcons.

Here are some adaptive behaviors of these urbanites

Rock Pigeons

Rock Pigeons that live in the country (and yes, they do) typically eat twice a day, filling their crops each time and digesting between feedings. Urban Rock Pigeons are completely opportunistic, always on the lookout for food.

House Sparrows

House Sparrows in urban settings have a shorter flight initiation distance, or flushing behavior, than their counterparts in more rural environments. Increased food availability/predictability, increased competition, and a reduced presence of predators in urban habitats may lead to bolder behavior.

Barn Swallows

The name says it all. This bird is known to nest in buildings under the eaves, and under bridges and docks. Barn Swallows are rarely found in natural areas such as cliff crevices or shallow caves. The only North American Barn Swallow population that still regularly uses caves as nest sites is in the Channel Islands off the California coast. Research suggests that Barn Swallows evolved around the time that humans were creating more structures in which, conveniently, Barn Swallows could nest. The reproductive success rate has been found to be higher in Barn Swallow nests in close proximity to humans, as opposed to those built in empty structures. Humans may provide implicit protection from predation.

Ospreys

The Osprey is another bird that now commonly nests in human-made structures, many constructed just for Osprey use. One study of Ospreys in central California found that of 34 occupied nests, only 4 were in trees (either dead or living), and none of those four were successful (with a nest collapse killing nestlings in 2 instances). Since the 1990s, the Forest Preserves of Cook County have placed 20 nesting platforms in the area, and in 2021 there were 14 nesting pairs. Friends of the Chicago River have installed 5 platforms along the river.

Fun fact! Smaller birds, including House Sparrows and Monk Parakeets, sometimes nest in an Osprey’s nest.

Peregrine Falcons

The Peregrine Falcon is the City of Chicago’s official bird. But would the Peregrine live here if Chicago (as we know it) wasn’t Chicago? Peregrine Falcons nest on cliffs from about 25 to 1,300 feet high. In locations without cliffs, nest sites include electricity transmission towers, quarries, silos, skyscrapers, churches, and bridges. Urban Peregrines produce more fledglings and experience overall higher nesting success than rural Peregrines, likely due to the wide variety of prey available. Chicago now has 20 breeding pairs, starting with one pair in 1988.

Peregrine Falcon and Rock Pigeon Chris Saladin/Audubon Photography Awards

Fun fact! The most commonly consumed prey of urban Peregrine Falcons is the Rock Pigeon.

Monk Parakeets

The Monk Parakeets of Chicago’s Hyde Park have become part of the city’s popular narrative. Introduced in the US in the 1960s through the pet trade, and first noticed in Hyde Park in the 1970s, the population grew quickly and then decreased somewhat, with birds dispersing to other parts of the city. Monk Parakeets build their own nests of sticks and branches, so they don’t compete with other birds for nesting sites. The nests can be elaborate communal structures that maintain the birds’ heat in winter. Monk Parakeets feed on a wide variety of seeds, fruits, and flowers, and during Chicago winters, they frequent backyard feeders. However, their numbers locally and nationally have been declining recently, without clear evidence as to why.

Fun fact! One, disputed, theory on the decrease in Hyde Park Monk Parakeets blamed the introduction of the Peregrine Falcon. (Would the falcon be a match for the parakeet’s beak?)

Although many species of birds have adapted well to the urban environment, urbanized birds do have increased exposure to poisons, air/noise/light pollution, outdoor cats, increased heat due to climate change, and other stressors. Reducing the risks of these hazards will enable these birds to continue to live successfully among urban humans.

Sources:

Birds have been adapting to human activity for millennia. 2024.

Traits shaping urban tolerance in birds differ around the world. Neate-Clegg, MHC, et al., 2023, Current Biology 33, 1677–1688.

Urban tolerance does not protect against population decline in North American birds. Petrenko, J, et al., 2024, Biology Letters.

Urban birds.

House Sparrow (Passer domesticus) escape behavior is triggered faster in smaller settlements. Garcia-Arroyo, M, et al., 2023, Scientific Reports 13, 2545.

Did barn swallows evolve thanks to humans? Frey, D. 2018. The Wildlife Society.

The relationship between nest location selection of Barn swallows (Hirundo rustica) and human activity and residence. Kim, M, et al., 2023, Scientific Reports 13, 23008.

Habitat use and reproductive success of ospreys in central interior California. Airola, J, et al., 2022, California Fish and Wildlife Scientific Journal, 108.

The osprey has made a comeback in Cook County. Green, M. 2021.

https://www.vims.edu/bayinfo/ospreycam/about_ospreys/

https://www.allaboutbirds.org/guide/Peregrine_Falcon/lifehistory