Thursday, June 13, 2013

Creating an Urban Oasis for Migratory Species

Over the last few years, we have cultivated a relationship with the NYC Audubon, resulting in biweekly Birding Tours of the park during migration. We've been delighted as our Audubon Guide Gabriel Willow teaches us about the avian life of NYC, and helps us spot some of these magnificent creatures up close. Now Gabriel shares his experiences in the park.

By Gabriel Willow

Bryant Park, like other green spaces around NYC, provides a welcoming oasis for migratory birds. However, the city as a whole is a challenging gauntlet for the thousands of cuckoos, kingfishers, woodpeckers, flycatchers, thrushes, vireos, warblers, tanagers, buntings, grosbeaks, sparrows, orioles, and other species who fly to and from tropical regions every Spring and Fall.  In fact, crossing through NYC may be the biggest challenge of the entire journey, second only perhaps to having to cross the Gulf of Mexico without stopping, or encountering severe storms.

Imagine yourself a small songbird, on the wing at about 5,000 feet.  You have been flying at night to avoid predators, and possibly to navigate with the help of the stars, following their patterns and the earth’s magnetic field for hundreds or even thousands of miles.  You have been flying from the forests of South America or Mexico or the Dominican Republic or Cuba, bound for the great deciduous forests of Appalachia, or the Hudson River Valley, or the vast boreal forests of Canada.  You follow the stars and the Atlantic coastline, on a path known as the Atlantic Flyway.  The coastline and flyway make a sharp bend to the East near the confluence of the Hudson River and the Atlantic.  This turning point is a crucial resting spot and was once a rich network of rivers, islands, tidal marshes, hardwood forests, and grasslands.

From U.S. Fish and Wildlife Service
This richness made the area popular with human settlers as well, both Native American and European. They all left their mark on the landscape, but the pace of change accelerated enormously in the 19th and 20th centuries: rivers were dredged and deepened; marshes were dredged or filled; forests were felled. And finally, buildings sprouted higher and higher over the landscape, filling the sky with a glassy obstacle course and disorienting lights.

Migratory birds following their ancestral flight paths have to contend with less and less habitat, which means less food and shelter when they stop to rest and feed, and now they have to navigate these confusing and dangerous canyons of stone, concrete and glass.  Research by NYC Audubon and others show that these birds are suffering as a result.  Many fly into reflective glass windows, which look to a bird like the trees or sky they reflect.  Injury or death are the result.  Migrating birds are also disoriented by the bright lights that illuminate cities, possibly because they obscure the starlight needed to navigate, or simply because the lights are confusingly bright.  Birds will often circle a brightly lit structure for hours, like moths at a porch light, using up precious energy stores needed to continue their journey, or even perishing from exhaustion.

While Bryant Park provides a rare patch of trees and grass in Midtown Manhattan, the many birds we see there during the migration season may be refugees of a sort, landing exhausted at dawn after circling the Empire State Building and other brightly lit buildings in the area.  Nearby Times Square must be one of the brightest places they encounter in their entire journey.

I recently spent several nocturnal hours on the observation deck at the Empire State Building, until it closed at 2 AM.  There was an incredible swirl of movement in the bright floodlights around its spire, which at first looked like insects but in fact were dozens, or perhaps hundreds, of songbirds: thrushes, warblers, buntings, and grosbeaks.  There were at least 20 species.  From this bird’s-eye location, high above the city, the most prominent patch of habitat, the only visible green space, was Bryant Park.  It gave me a sobering new perspective on why we find so many migratory birds in the park.

Photo by Gabriel Willow

Recent studies are giving us a clearer picture of the threat all of these lights and glass pose to migratory birds.  It appears that the single largest mortality factor for birds passing through urban areas is collisions with buildings (in more rural settings it is depredations by feral and outdoor cats).  A conservative estimate puts the number of birds killed annually by striking windows nationwide at 100 million.  NYC Audubon has been collecting data on these casualties, and helping birds injured by collisions, through its Project Safe Flight.  Injured birds are rehabilitated and released; dead birds provide important data points in tracking the relative impact of individual buildings.

There are solutions: working with building owners to reduce light pollution and save energy by dimming nighttime lighting, particularly during migratory seasons.  New types of glass are being developed that are more visible to birds by reflecting UV light, which can be seen by birds but not by humans.  The challenge now is to encourage the use of this glass by building developers.  NYC Audubon is reaching out to building owners to help mitigate light pollution through its Lights Out NY program, and has published guidelines on bird safe building techniques.  We need help in collecting data, ascertaining which buildings pose the greatest threat, and helping injured birds.  Project Safe Flight needs volunteers!  Please contact PSF Coordinator Adriana Palmer at apalmer@nycaudubon.org if you are interested.

Our challenge is to make NYC and other cities as hospitable an environment as possible to migratory birds and other species.  Otherwise urban settings will only be home to non-migratory species, such as House Sparrows and Rock Pigeons, that have evolved or been bred to live alongside humans.  As more and more of humanity lives in an urban setting, increasingly our only exposure to nature, to other types of life-forms, comes through these familiar species.  It is a limited palette of the spectrum of life on the planet; soon a child might be forgiven for thinking birds consist largely of flocks of house sparrows and pigeons.  This would be a real loss, and an avoidable one.  With thoughtful planning and urban design, and sensitivity to the needs of other species, we can modify our urban landscape slightly to make it less of a challenge and more of an inviting landscape for migratory species.

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