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In Conversation with Ornithologist and Author Scott Weidensaul on Bird Migration

Central Park is located along the Atlantic Flyway, a major migratory route for birds extending from South America to Greenland—making it a well-known bucket list location for many birders and non-birders alike. In an average year, an ambitious birder can spot about 200 species of birds in the Park, many of them migrants.

Whether you’re a dedicated birder who never leaves home without your “bins” or a casual observer who simply appreciates a V-formation of geese flying overhead, you’ve witnessed the wonder of migration. Bird migration might seem routine—a seasonal, natural occurrence—but what’s going on in the sky is spectacular. To better understand this phenomenon, we talked with nature writer and bird researcher Scott Weidensaul, whose new book A World on the Wing: The Global Odyssey of Migratory Birds explores bird migration and the science behind it.

Book jacket depicting a flock of migratory birds against a backdrop of distant, snow-capped mountains.

Rebecca Pou: We’re in the middle of spring migration season in Central Park. Can you talk about the migrant birds that visit big cities like New York and stop by urban greenspaces like Central Park?

Scott Weidensaul: The fact that Central Park attracts so many migrants at all is astounding, but you must look at it from a bird's perspective. If you're a young bird like a small songbird on your first migration, the light from the metropolitan area—the whole megalopolis up and down the east coast and in places like Chicago and Houston and Dallas—tends to draw you in. They’re migrating after dark and navigating using starlight. The urban light pollution pulls them in. They've been flying all night. Daylight comes, they look around, and it's just a sea of concrete and buildings. Then you have this enormous green oasis right in the middle of Manhattan. All the urban parks in the New York area are tremendous places for migrant birds.

Now, every once in a while, you'll get one that really surprises people like the snowy owl that showed up in Central Park. Snowy owls in New York City are not that unusual. What's unusual is to have them in the middle of Manhattan. Although interestingly, snowy owls are one of the species I studied. We track them with GPS transmitters, and we've had some of our tagged snowy owls fly through the middle of New York City, through the middle of Manhattan, in the past. We had one that landed on a 58-story skyscraper next to Madison Square Garden a couple of years ago, at two o'clock in the morning, looked around, and kept going.

What was odd about the Central Park snowy owl was that it spent a day or two in the Park. That's a very enclosed place for a snowy owl. Even the open areas of the Park—the meadows and fields and such—are a very hemmed-in environment for a tundra animal that lives where there are no trees at all. On the other hand, the rooftops in Manhattan probably give them a great view and I suspect more snowy owls go through Manhattan and stay up on the rooftops at night than people realize.

The owl is seen perched on the far end of a branch with the blurred image of large building in the background.

This winter’s snowy owl, a species that hadn’t been recorded in the Park since 1890, delighted Park-goers for an entire day in the North Meadow and continued to appear in the following weeks. Photo by David Lei

Was the snowy owl sighting as rare as it seemed, or was it just more likely to be spotted with the growing popularity of birding?

It's probably both of those things. I think it is unusual for a snowy owl to end up spending any amount of time, especially on the ground, in Central Park. But certainly the number of people in the Park and the number of birders in the Park make it much more likely that if a rare bird, like a snowy owl, shows up for a brief period that somebody is going to spot it, somebody is going to get a picture of it, and word is going to get out immediately through social media—which happened this time.

I was really impressed by the fact that everybody was so respectful of the owl in Central Park. That is sadly not always the case. Snowy owls are naturally—especially young birds like that one apparently was—pretty approachable. People love them a little too much. They get a little too close sometimes.

Many migratory birds eat insects that have evolved with native plants. “By working with plants, indirectly and directly,” says Lisa Kozlowski, a member of the Central Park Conservancy’s Natural Areas team, “we’re making contributions toward birds. We work very hard to maintain diversity—we have over 400 species of native plants.”

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You mentioned that light might be part of the reason birds are attracted to the City and then see the Park. At the Central Park Conservancy, we try to do things to make the Park attractive to both people and wildlife. Like we leave snags [dead or dying trees] in the woodland habitats and prioritize bird- and pollinator-friendly plants. What’s in the Park that attracts birds, other than it being a habitat?

The fact that it’s an oasis is what's drawing them there. And I think you've touched on something that we have only recently realized is a really important step that we should be taking for bird conservation. Because we know now from radar data and from eBird data how many birds are being drawn into urban areas just because of light pollution, urban parks and urban greenspaces turn out to be incredibly important for conservation.

A lot of these birds that are attracted to urban areas are young birds on their first migration. It's critical to keep them in the population so the populations don't decline further. [Since 1970, the North American bird population has declined by 29%, amounting to the loss of three billion birds. Birds face many threats, and changing climate patterns, habitat loss, and building collisions add to the inherent difficulty of long-distance migration.]

And so whatever we can do in urban parks to improve and restore bird habitat by, as you say, planting native species that produce lots of insect food and lots of fruit and berries for them at that critical time of the year, providing weedy, tangley, thickety habitat for them, lots of escape cover for them, providing areas of water for them, is vital. We could potentially get much more bang for our conservation buck if we put more money and more effort into improving bird habitat in urban parks and urban greenspaces than protecting pristine areas in more rural or wilderness areas. Not to say that's not also important but given how many birds are getting drawn into urban areas, if we can find a way to balance creating bird habitat with providing for human recreation, that's going to be really important.

And so good on the Conservancy for doing that. You're way ahead of it.

A male red-winged blackbird perches on a rock overlooking the Pool.

Red-winged blackbirds are one of the earliest migrants to arrive in the Park and many nest here and stay through the summer. They can often be found near bodies of water, like this male at the Pool.

I also want to touch on the bird-safe glass movement. The City recently passed a measure requiring new construction in New York City to use bird-safe glass. And the Conservancy has incorporated bird-safe glass into recent projects. What does a bird-friendly urban environment look like?

I think bird-safe glass is a huge step because we've known for years that something like two billion birds die every year in the United States from window collisions. It’s a huge problem. It's a very dispersed problem. If you think about every building out there getting at least a couple of birds thumping into the windows on a regular basis, it adds up tremendously. I really respect the fact that New York has taken that significant step, and I hope it leads a lot of other urban areas to incorporate bird-safe glasses as a building design requirement.

Blackburnian Warbler Ursula Mitra 2020

The height of spring migration in the Park occurs in late April and May. Park visitors can spot neotropical migrants, such as Blackburnian warblers, that have flown to New York City all the way from Latin American and the Caribbean. Photo by Ursula Mitra

What can birders and Park visitors do to be good stewards to birds in the Park?

Consider yourself an ambassador for birds and monitor your own behavior. Don't do anything boorish. If you have an opportunity to share the birds you're looking at with somebody who happens to be walking by, do so. Often when I'm birding, I carry a second pair of binoculars with me so if I run into somebody and we're looking at a cool bird and they seem even the least bit interested, boom, here's a pair of binoculars, take a look. Recognize that every person you share those birds with, every person that you pull into this, you let them see a little bit of how amazing the world of birds and bird migration are. That’s another vote for birds. That's another voice for birds out there, and we can use all the help we can get.

A couple use their binoculars in a woodland setting.

Birding, Scott says, “had a long reputation as being a super nerdy thing to do. And I think a lot of people who were birders kind of kept that to themselves. But it's almost cool these days. A lot of people who never gave it a thought before found themselves stuck inside and in need of connection to the outside world.”

Just to circle back to what we said before, visitors should relish the fact that Central Park is such an important waystation for so many migratory birds. [Central Park co-designer Frederick Law] Olmsted did not intend that to be the case when he designed Central Park, but it’s remarkable how well the Park serves as a life raft for so many birds.

My hat is off to the Conservancy and everyone working to improve the habitat there. It’s only going to become more important for migratory birds as the years go by. Relish it, enjoy it, celebrate it with as many people as you can, pass the word, and keep up the good work.

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