Target Species of the Biornis-Aesthetope Avian Habitat Green Roof

Lower Manhattan, NY, USA

The following excerpts, stories, and facts have been provided by the following institutions and compiled here as notes: -New York City Audubon Society -Scott Edwards of the Ornithology Department at Harvard University -Viviana Ruiz-Gutierrez of the Ornithology Lab at Cornell University

In cities, humans have inadvertently created an environment that in intrinsically hazardous to the wildlife with which we share this plant. With the rebuilding of lower Manhattan, we have an opportunity to improve this record.

The building plans for the World Trade Center site combine lit towers above a labyrinth of reflective glass below. This combination as currently proposed will produce a mini environmental disaster on the Eastern Flyway costing the lives of several thousand birds a year. Species already stressed will be hit hard every migration season.

Most New Yorkers don’t know that their city is on a flight path for millions of migratory birds. Twice a year hundreds of species of birds, many of whom are experiencing long-term population declines, travel thousands of miles on their extraordinary journeys to and from breeding and wintering ground in the western hemisphere. These amazing animals navigate from areas as far south as South and Central America, to as far north as Canada, using a variety of cues to keep them on course.

These migrations have always been dangerous, but have become even more perilous as birds navigate through and around our cities. It is estimated that 100 million birds are killed every year in the United States alone through collisions with buildings. Second only to habitat loss as a cause of declining populations, some experts believe the number is even higher, perhaps as many as one billion killed annually. The height of tall buildings in NYC, the frequent use of reflective or simply transparent glass, and the illumination of these structures, is a major component of injury and mortality for birds.

Project Safe Flight

1.Lights Out New York. Turn out external lights of tall buildings between midnight and 6AM and shield interior lights as well. Most species migrate at night and can be disoriented by illuminated structures.

2.Make Glass Visible. Reduce mortality rates from glass strikes during the day.

3.Volunteer Network. Rescue injured and stunned birds; participate in outreach and education programs.

4.Promote Research. Field volunteers continue to collect and report data for analysis. ***

Exactly what is bird-friendly building design? Ideally they would feature less windows that permit people to see out, while being opaque and non-reflective from the outside. Window blinds, interior light regimens and external landscaping are all elements to consider.

Quick Facts: How to Create a Viable Urban Rooftop Bird Habitat

1.Primarily, the roof will serve as a “refueling station” for migrating birds. Migrating birds look for large areas of green space and reflections, which indicate pools of water. Therefore we will need to provide a maximum surface area of green space, as well as at least 6 foot-diameter pools of water (these pools can be as shallow as a “kiddy pool”).

2.Hierarchy of species within the Tree is recommended. Bird habitats in the Tree provide kestrel perching platforms at the top, owl niches at the sides in the middle section of the Tree, and berry bushes at the base for a Barn Swallow colony.

3.Pigeons are likely to come in large numbers and the amount of avian excrement produced will be intolerable; therefore we have designed to attract birds of prey, which will scare away pigeons and other bird-pests. The presence of diurnal raptors (kestrels, hawks), as well as owls, is guaranteed to prevent pigeons from occupying the roof. Maintaining a balance between the number of raptors and owls with the number of songbirds will be important; but with monitoring, this is totally feasible. Owl decoys have been used for centuries in Europe to scare away pigeons.

4.Birds love structural complexity. Such complexity is achieved in the Tree by using the tetrakaidocahedra (14-sided polyhedron) as a structural unit. The structure that bubbles take when packed, the tetrakaidocahedra can efficiently support the amorphous Tree form while fulfilling its programmatic agenda as perching space.

5.For a good foraging habitat, birds need to inspect the feeding grounds from a sheltered look-out area at a high elevation, and descend into a broad, open meadow with unobstructed space. The Tree is the look-out place and the meadow is the open area for foraging.

6.Smaller birds like to bathe themselves in dust, so we provide a small sand box area.

Selected Bird Species and Fun Facts:

Peregrine Falcons

Peregrine mate for life, but if one of the pair dies, then remaining falcon will choose another mates. Usually peregrines live 8 to 12 years, but some NYC falcons are almost 20 years old. The peregrine is the fastest bird known. It sits motionless on a high perch and soars across open areas to look for a bird to catch. The peregrine folds its wings and dives straight down at 200 miles per hour, catching the prey from above in its talons and killing it by breaking its beck with its hooked beak. This dive is called a stoop. Peregrines will take ducks, including some that are bigger than they are.

Historically peregrine falcons nested on the New Jersey Palisades, the cliffs across the Hudson River from Upper Manhattan and the Bronx. During the mid 1900s a few pairs nested on the artificial cliffs on New York City’s skyscrapers and bridges. But the by 1960s peregrines disappears east of the Mississippi River.

When scientists looked for a reason, they found that there was so much of the insecticide DDT in the bodies of all birds of prey that mother birds couldn’t make normal eggs. The eggshells were so thin that sitting on the eggs for hatching crushed them.

To save the peregrines, the United States government put them on the Endangered Species List and stopped DDT from being used. (N.G-W., NYC Audubon)

American Kestrels

Like most New Yorkers, the American kestrel has learned to live among buildings. In most places the kestrel nests in tree cavities or nest boxes. In the city it nests most often in the nooks and crannies of apartment or office buildings. Instead of perching on the roadside telephone wires in open country, it perches on rooftop television antennas in the city. In NYC, buildings replace cliffs, ledges replace trees for nesting, and food sources shift more to rodents and less to large insects.
Unfortunately, the American kestrel population is declining despite the fact that an estimated 15 pairs of kestrel nest in NYC. Many more migrate through and even winter in the City. The most likely cause of decline is the loss of open areas. It is hoped that the selection of the American kestrel [as the NYC Audubon Society symbol] will increase awareness of this beautiful bird and show, at least in this one case, how man and nature have learned to coexist. (R.G., NYC Audubon)

Every living thing, or organism, serves a role in their ecosystem, where they have a position in a food chain. A food chain describes how energy, or food, moves from one organism to another. There are many food chains because most organisms can get their energy from more than once source. The food chain that includes the American kestrel involves the Masked Shrew (a secondary consumer) which eats the grasshopper (a primary consumer) which eats grass (a producer), which produces its own food through photosynthesis (which takes sunlight, water, and CO2 to turn it into sugar and oxygen). The American Crow scavenges on the prey of the kestrel, and mushrooms decompose the organic matter leftover from the crow and kestrel into nutrients for plants. (C.H., NYC Audubon)

Owls

Owls cannot roll their eyes in their sockets. They look around by turning their heads up, down or sideways. With their extra-flexible necks, owls can turn their heads about ¾ of the way around. It is a myth that thye can turn their heads all the way around—that’s impossible!

The “ear tufts” on some owls’ heads are not ears, only feathers. Their ears are hidden on each side of the head, slightly behind the eyes. In many species of owl, the ears are different on each side (one is placed high, and other is place further forward). The facial disks (ring of feather around the owl’s eyes) also help hearing. They channel sound directly to the ears. So, by turning and tilting its head, an owl can pinpoint the exact location of its prey. For an owl to be a successful hunter, it needs to be able to surprise its prey. So owls have developed “silent flight”. The outer feathers of each wing have tiny serrations on their edges. These soft edges let air pass through silently when an owl flies. Owls swallow their prey whole, by they cannot digest fur, feathers, or bones. Several hours after eating, an owl coughs up a slimy little package called an “owl pellet”. A pellet contained the fur, feather, claws, teeth, and complete skeleton of the owl’s prey. (D.D., NYC Audubon)