At WCS’s Bronx Zoo, a group of WCS birders have been surveying the grounds for nesting wild birds. Their goal: to find out how the Zoo’s 265 acres, an important rest stop along the mid-Atlantic flyway and a green oasis in the midst of the big city, provides for breeding birds, and which species it attracts.

The birders are turning up some surprising finds, like wood ducks, warbling vireos, and black-crowned night herons. What’s even more surprising is where they’re finding them—singing in trees on the Bison Range, swimming through the once blighted Bronx River, even nesting in exhibit signage. Below, WCS publicist John Delaney leads a birding tour of the Zoo.

Q&A with Nancy Clum, Curator of Ornithology

Nancy Clum

For seven years, Nancy Clum has kept an eye on the Bronx Zoo birds—both in the exhibits, and on the outside. Inspired by the bird-watching of another curator, William Beebe, who documented the wild birds breeding in the park 106 years ago, Nancy initiated the Bronx Zoo Breeding Bird Survey in June. The survey catalogs all of the species seen displaying breeding behaviors—courting, serenading, nesting, and feeding chicks. Below, she discusses how the park’s birdlife has changed over the century and why to many birds, the Zoo is still a good place to raise a family.

What made you want to begin counting nesting birds?
A WCS librarian mentioned to me a long list of birds that nested in the zoo during Beebe’s time, in the early 1900s. I wanted to see how things had changed. The zoo’s original habitat was farmland or pastureland. It’s very different now. The area around the zoo has become more and more developed, which makes its parks green islands of wildlife habitat.

Chad Seewagen, a biologist in our department, also began the NY Bird Monitoring program a few years ago. He started looking at the quality of the parks as stopover sites for birds migrating through the area. The breeding bird survey expands on this work by looking at how the parks attract birds that nest in the area.

Is your survey similar to William Beebe’s work in 1904?
Beebe was a very accomplished field naturalist. He recorded 62 species in the park. So far we’ve found about 50. But our survey is much more formal—we categorize our birds as confirmed breeders, probable breeders, or possible breeders. These groupings depend on what we see the bird doing—singing, nesting, in a pair, with fledglings, etc.

How do your results differ?
There were bluebirds, shrikes, and meadowlarks in Beebe’s day. Those are birds that we don’t see here anymore. They’re grassland species. Many grassland species are also experiencing global declines due to diminishing habitat.

Today, we record mallards and a greater number of egrets. These were in the area 100 years ago, but not at the zoo. Back then, there was no reason for these species to come to the park, since the surrounding area was so much less developed. Now the reverse is true. The park is some of the last best habitat left.

The zoo is made up of lots of different habitat types. Does this contribute to the diversity of birds that live here?
Yes. We have divided zoo grounds into 8 distinct blocks. Blocks like Astor Court are very developed with lots of infrastructure. Others are very forested, and we also have the Bronx River. Exhibit areas like those within the Zoo Loop tend to be more open, while Wild Asia is more forested. So we certainly expect to see a variety of species within these habitats.

Which part of the zoo are you monitoring?
I’m over in Wild Asia. There’s a lot of turf over there, and some forest species that I haven’t seen in other parts, like red-eyed vireos or wood pewees. It’s really pleasant just to walk around the river, and through Wild Asia, where the monorail goes around. There’s not a lot of infrastructure. And there are very tall trees with species that nest way up in the canopy. I see red-tailed hawks there all the time. But I haven’t seen them nesting yet. That’s another question the survey has raised—just because a bird is breeding here doesn’t mean it is breeding successfully. Eventually, we’ll start to look at nesting success rates for the species we are monitoring.

Is the summer the best time to see breeding birds in this area?
For most species, but not all. For example, owls start breeding in late winter and early spring, and their offspring fledge in August. So we will have to do an owl survey later in the summer.

In the fall, when all the leaves are down, we’ll do a nest survey. By spotting and identifying nests in a tree, we’ll get a better idea of how many birds there are of the different species, at least for those that are nesting in deciduous trees.

What’s the most memorable bird story from your time at the zoo?
A couple years ago, we had a ring-necked pheasant hanging around the grounds. We’d find him up on Astor Court, following around a female pheasant on exhibit. They were different species but he was very focused on her. Visitors would say, “Your bird is out,” and we’d say, “No, it’s not ours!”