by Cathy Blumig

"They fly at night?"

That was the most common reaction I got from people when I told them I was going birding, at night, on the Empire State Building (ESB). That some birds migrate at night was a revelation for many people, and it was one of the reasons I wanted to organize an activity centered on nocturnal migration. Then I learned about Dr. Robert DeCandido and some of the research on nocturnal migration that he had conducted from the 86th floor observation deck of the Empire State Building.

Dr. DeCandido has a PhD in Ornithology and had collected data about nocturnal migration from the ESB under the auspices of the Hawk Mountain Sanctuary. This sounded like a wonderful opportunity to learn about nocturnal migration, and I was delighted when Dr. DeCandido agreed to meet with NJ OWL members to watch an evening flight.

We met Bob, often called "Birding Bob," in the lobby of the ESB at 5 o'clock on October 10, 2006. Everyone had purchased their tickets to the 86th floor observation deck beforehand, and we had the extra clothes that we'd need for the cooler environment up top. After some cursory introductions we headed up the escalator, Bob at the front, to make our way through security and up the elevators to the 86th floor.

It became apparent that Bob was a celebrity of sorts among the ESB staff. Virtually everyone we passed would call out, "Hey Bird Man! Where you been?" Some would explain how they had seen birds circle the building's tower on one night or another. Or they would describe how some birds had landed on the building, or if they had spotted a peregrine falcon making the rounds. It was apparent that, because of Bob's work and his amazing ability to share his enthusiasm for his research and birds, that he had revealed a special feature of this famous building that they probably wouldn't have known about otherwise. It was great to see.

When we finally reached the 86th floor we assembled against one of the walls outside the ESB gift shop and discussed some general information about bird migration. First, why do so many bird species migrate at night? Bob explained that a night environment offers a number of advantages for many species of migrant birds. For one, it is comparatively more humid at night than it is during the day, so birds lose less water while they are flying. For another, the cooler night air helps to keep birds from overheating. It made me think back to when I was on the cross country team in high school and how much easier it was on my body to train at night during the summer as opposed to the middle of the day.

The situation is different for large, soaring birds such as hawks and vultures that mostly migrate during the day. These birds don't constantly flap their wings when they migrate, as warblers and thrushes do, so they don't lose as much water or generate as much body heat while they fly. Instead, Bob explained, they ride the rising columns of air (thermals) that are created during the day and only occasionally flap their wings.

Bob discussed some of the hazards that birds encounter while migrating. A major problem is loss of habitat. Quality habitat for migrant birds is essential in order for them to be able to rest and forage during their long journeys. Without these places, it becomes much more difficult for birds to successfully complete their travels, and they are more likely to perish. Imagine if you had to drive from New Jersey to Miami with only three rest areas, two restaurants and no motels along the way and you get an idea of the hardships that migrant birds face when, each year, another piece of their habitat is carved up for strip malls and other developments.

Also free-ranging cats, whether they are well-fed pets or feral, kill many birds. (Conservative estimates place bird mortality caused by cats to be at least 1 million birds each day in the US.) They also kill prey items such as meadow voles and other small mammals that would otherwise be available to migrant birds such as hawks and owls to eat.

Then there was the question of collisions with skyscrapers. Bob explained that certain types of skyscrapers and certain environmental conditions appear to make tall buildings more of a hazard to nocturnal migrants than do others. For example, the World Trade Center was probably a greater hazard for migrants than the ESB because of all the reflective glass that adorned the outside of that building.

Collisions with the ESB appear to be influenced by certain environmental conditions. For instance, foggy nights with light winds appear to increase the likelihood of collisions. It was a relief to learn that during Bob's autumn research in 2004 he was only able to document seven birds dying as a result of hitting the building. It's unfortunate that even those birds died, but when you consider that more than 10,000 birds had been counted flying safely past the ESB during that time that's not too bad. Bob feels that more research is needed in this area to understand the specifics of what causes birds to collide with buildings so that mortality can be kept to a minimum in areas with tall buildings.

Although the evening wasn't the migration blowout we hoped for (the northwest winds didn't quite kick in to the extent we needed them to), it was fascinating nonetheless. Along with the bat that we saw occasionally flying around the ESB tower, and the moths that flittered by (what were they doing all the way up there?), we had the chance to observe peculiarities of avian flight that many of us hadn't seen before. For instance, I didn't expect that the lights from the ESB would washout the plumage of each bird to the extent that it did, which made it difficult to identify individual species. Even Bob would only go so far as to characterize a bird as being a warbler or thrush, etc. based on how it flew, though he might describe an individual bird as being a "probable" rose-breasted grosbeak if that's what it appeared to be. Most of the birds we saw appeared to be thrushes of some kind. The other curious thing was how some birds negotiated the ESB tower. A couple of times we'd see a bird circle the tower, apparently drawn to the light. Bob said at other times he had observed repeated circling of the tower by flocks of birds usually on overcast nights with light winds. The birds we observed seemed to only circle once, take a break and then continue on unharmed.

NJ OWL members look out across Manhattan and points beyond in search of nocturnal migrants.

More bizarre were the birds that flew backwards. Bob explained that facing into the wind gave the bird better control rather than being pushed along haphazardly. In this way, they could safely maneuver the tower and fly on.

These maneuvers aside, for me the star of the show was the peregrine falcon. Several times we watched it perch near the tower and then fly out in an attempt to pick off the very migrants we had come to watch. Mostly the peregrine missed - except for once. It had flown high above the tower and then zeroed-in on an individual bird, what Bob suspected was a rose-breasted grosbeak. We thought it had missed again until we saw the probable grosbeak fluttering helplessly in the peregrine's talons. It's not wise to play favorites when you're studying wildlife, but I wished the falcon had nabbed a less appealing bird, like a European starling. Still, the falcon had to eat, and it certainly earned the meal.

When we finally left the 86th floor and stepped out on to 5th Avenue I looked up at the ESB and thought about all we had seen that night. Thanks to Bob I now had a broader understanding of the intricacies of nocturnal migration, and I doubted if I would ever look at the ESB in the same way again.