This post was first published by the Cornell Lab of Ornithology and with their with permission it is being reposted here.
Not Just Sparrows and Pigeons: Cities Harbor 20
Percent of World’s Bird Species
By Andrea Alfano
Rock Pigeons, House Sparrows, and
European Starlings are widely known as “city birds,” and with good reason.
These three species (plus Barn Swallow) occur in more than 80 percent of cities
according to the first-ever global study of biodiversity in
urban areas, published earlier this year in Proceedings
of the Royal Society B. But there’s more to cities than this narrow cast of
avian urbanites: cities also retain more of their region’s native diversity
than previously thought, according to the study’s analyses of bird and plant
census data. So take heart, your next city stroll has much more to offer than
just a few ubiquitous species.
In fact, at least 2,041 species—20
percent of all known bird species—live in the world’s cities, according to the
research. Unlike previous studies, which have focused on single cities or
regions, this study spanned six continents, compiling data on birds from 54
cities and plants from 110 cities. The researchers themselves hailed from North
America, Europe, Australia, and South Africa.
House Sparrows are one of the most
successful species to adapt to living in urban environments, but a surprising
20 percent of the world’s species can be found in urban areas. Photo
courtesy of Madhusudan Katti.
“One of the big paradigms of urban
ecology is that the biota of the world’s cities is homogenized,” said lead
author Myla Aronson, a researcher at Rutgers University and a Cornell
University alum. “But we showed that at the global scale, cities are primarily
retaining the unique composition of their geographic location.”
This means that although there are a
few species that can truly be considered ubiquitous “city birds,” they are in
the minority—a finding that wouldn’t have been possible without the global
scope of this study. In fact, the list of species that you can find across 80
percent of the world’s cities amounts to just the four species mentioned above.
The full list of birds found in cities includes nearly three-quarters of all
bird families. Cities even provide habitat for rare species, including a total
of 36 bird species identified by the IUCN
Red List as threatened with extinction, the
study said.
For many people, this remarkable
diversity is often overshadowed by the notion that humans have almost entirely
forced nature out of cities. A recent study by a different group showed that many urbanites fail to notice increases in
biodiversity even when they happen.
“If you’re not particularly
connected with nature, it’s easy to just not see what’s there,” said Karen
Purcell, project leader for a Cornell Lab project called Celebrate Urban Birds. Purcell aims to change this “biodiversity blindness” by
encouraging people to learn about and look for just 16 bird species that are commonly found in cities. It’s intended as a manageable introduction to the amazing
diversity that can be found in cities.
Formerly on the endangered species
list, Peregrine Falcons are increasingly common in cities and are one of 16
species tracked by our Celebrate Urban Birds citizen-science project. Photo courtesy of Laura
Erickson.
For many city-dwellers, knowledge of
just these few species leads them to become more aware of urban biodiversity in
general, and encourages them to take pride in their city’s non-human life in
addition to its human culture.
“We want to get that bug into people
to watch,” said Purcell.
Urbanites are right to realize that
cities are by no means ideal habitats for birds. Many species still manage to
survive in them, but only around 8 percent as many species are found in cities
as in the non-urban areas surrounding them. That’s why part of the goal of
Celebrate Urban Birds is to inspire people living in cities to take action to
support their urban biodiversity.
“Providing native vegetation is
something that not only city planners can do, but that people can also do on a
smaller scale,” said Frank La Sorte, a researcher at the Cornell Lab and an
author of the urbanization study.
Cities with the least amount of
urban land cover have the highest densities of bird species, according to the
study. Parks and community gardens filled with native plants play an important
role in maintaining bird species, but providing even small patches of vegetation, like hanging basket plants or container gardens, can help
to attract birds to urban areas.
As of now, cities cover only 3
percent of the Earth’s terrestrial surface, but this doesn’t mean that the
effects of urban greening efforts are insignificant. It’s not only the size of
a city that affects biodiversity—location is important too.
“People tend to settle in regions
that are already very species-rich because these are often the best areas in
terms of climate and agricultural activities,” said La Sorte.
Cities may only take up 3 percent of
the Earth’s land cover, but they are currently home to more than half of the
world’s human population. This makes increasing awareness of biodiversity in
cities even more crucial, because people can’t care about or protect things
that they don’t notice. But actions as simple as participating in a citizen
science project like Celebrate Urban Birds can open one’s eyes to biodiversity
for a lifetime
“Once you see, you don’t ever stop
seeing,” said Purcell.
For more on biodiversity in urban
areas:
- see the study in Proceedings of the Royal Society B, and its companion study on plants in urban areas
- try out the Celebrate Urban Birds citizen-science project
- get some advice on Urban Gardening for Birds from Celebrate Urban Birds
- read our movie review of Birders: The Central Park Effect
reposted from:
The Cornell Lab of
Ornithology blog:
