Birds and Biodiversity

March 2006

Birds and Biodiversity: A Conversation with Dr. Chris Filardi

Orinthologist Dr. Christopher Filardi joined the Museum’s Center for Biodiversity and Conservation in the summer of 2005. He spends much of his time conducting biodiversity research in the Pacific region, and he is now also coordinating scientific content for the CBC’s Spring Symposium, Conserving Birds in Human-Dominated Landscapes: Weaving a Common Future.

Together with Dr. Robert Moyle of the Museum’s Department of Ornithology, you recently published a paper in the journal Nature that attracted a lot of attention—can you explain why its findings are important?

For a long time islands were regarded by scientists as natural laboratories for understanding the diversification of life. Darwin’s observations in the Galápagos islands shaped his theory of evolution by natural selection.

The many thousands of islands spanning the tropical Pacific, where I conduct my research, support an amazing array of unique animal communities. Yet islands have generally been considered evolutionary “dead ends”; after animals and plants emigrated from the mainland, it was believed that they became so specialized for island life that they could not leave or compete in species-rich continental settings. Today, with the use of new molecular technologies, we have revisited these prevalent assumptions about diversity on islands. Our new data for monarch flycatchers shows that animals can spread from island to island, giving rise to an explosion of new species, and can even colonize the mainland again. These patterns suggest that widely dispersed islands and archipelagoes can actually serve as engines of evolution and sources of new biological diversity.

Does this new finding have implications for how conservation decisions and actions are determined?

Absolutely. I suspect that the emphasis will shift from thinking about islands as icons of the evolutionary past to embracing the important role that islands play in generating global biodiversity. Oceanic islands may be far more critical in this regard than we’ve ever realized.

Tell us a little about the upcoming symposium Conserving Birds in Human-Dominated Landscapes: Weaving a Common Future.

Scientists and conservation practitioners have tended to focus their efforts on imperiled birds found in wild landscapes. What we’ve spent less time on is conserving the birds, and bird communities, that live among us, in landscapes that are dominated by humans. It happens that these landscapes—cities and suburbs, agricultural and industrial areas—harbor some of the most exceptional patterns of bird diversity on Earth.

New York City is an exceptional example of this. Despite our immense impact on the lower Hudson Valley, you can find an incredible diversity of birds here. Unlike the wild areas that conservationists have traditionally focused on, in developed landscapes we don’t have the luxury—or the burden, depending on how you look at it—of conserving historic patterns of diversity, because those have been erased. Although what we have now is essentially a very muted subset of those species found here historically, there is also opportunity. The focus of the symposium in April is to identify and showcase unique possibilities for conserving birds in the areas that we inhabit and use most intensively. This requires understanding how our behavior impacts patterns of bird diversity.

One of the most obvious ways humans have impacted bird diversity is the introduction of alien species. In the late 1800s, there was a movement to introduce all the birds mentioned in Shakespeare’s plays into Central Park. Most of these introductions did not work, but one did—the European starling. Today, starlings are entrenched across North America and compete directly with many native species.

We have also impacted bird populations by paving the way for overabundance. Historically, brown-headed cowbirds lived where American bison lived, following them and feeding in the wake of the great herds. With the eradication of the large bison herds and the introduction of domestic cattle, brown-headed cowbirds have greatly expanded their range. Significantly, brown-headed cowbirds are brood parasites—they don’t build their own nests but drop their eggs in other birds’ nests for them to raise to the detriment of the host’s offspring. Host birds where bison historically ranged had some defenses in place, but when the cowbird’s range expanded, they came into contact with many birds that were naïve—in an evolutionary sense—to brood parasites, and unwittingly raise a great number of cowbirds while their own species’ outputs plummet.

The good news is that many aspects of human-dominated landscapes also appear to nurture or attract some fairly spectacular and, in some cases, rare birds. Certain raptors thrive in cities; for example, here in New York, peregrines are nesting and raising offspring atop skyscrapers and on bridges, feeding primarily off of a wealth of pigeons. Central Park is a key stopover site for neo-tropical migratory birds such as warblers, vireos, and tanagers. We believe there is a lesson here – that some types of human activity can maintain or attract significant bird diversity. With this in mind, a central objective of the April symposium is to identify and capitalize on unique opportunities for invigorating bird diversity in cities and the wide array of other human-dominated landscapes.

What can people do in their everyday lives to help conserve bird diversity?

Not surprisingly, agriculture has huge implications for birds, as it does for all of biodiversity. Buying seasonal produce at a farmers market supports local farmers that are part of a landscape mosaic that is usually much friendlier to bird diversity than large monocultures. Choosing shade-grown, organic coffee is another way to support alternative agricultural systems that are less damaging to wildlife. Biologists report finding significantly fewer bird species in coffee fields cleared of all native growth. Traditional shade-grown coffee plantations require few or no chemical pesticides or fertilizers—the leaf litter replenishes the soil nutrients and birds discourage pests.

Anyone with a yard, terrace, or roof deck can create a local “hotspot” for biodiversity by planting (or leaving in place) native trees and shrubs that provide nesting areas and protective cover for birds. Controlling non-native bird predators such as domestic cats is also an important part of maintaining or creating native habitats. Free-roaming domestic cats are responsible for killing perhaps hundreds of millions of birds each year. Many groups, including the Humane Society and the American Bird Conservancy, maintain that keeping your cat inside makes for a healthier and happier feline as well.

Finally, partly because we tend to conserve what we care about—and also because it’s a lot of fun—learn about the birds that live in your area. Introduce a child or friend to the annual cadence of the lives of birds – the ebb and flow of migration and breeding, the shifts in behavior that allow tiny songbirds to survive a harsh northeastern winter, or the meter and meaning of birdsong on a spring morning. Within the cityscape of New York, this is a great activity for kids. Central Park has been a reckoning point for my own children’s growing awareness of the diverse world around them, and we have reveled in the comings and goings of the Park’s many resident and migrant birds. Along these lines, the Center for Biodiversity and Conservation has produced a wonderful Kid’s Guide to the Birds of Central Park, which is freely available from the Center on our website or by request.

Thank you, and we’ll see you at the symposium.

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