- Nest cameras have been set up in cities across the United States to give viewers an intimate look into the nesting activities of urban-dwelling birds of prey like eagles, falcons, hawks, and owls. These raptors represent a rare instance of wildlife thriving amidst the hustle and bustle of areas densely populated by mankind.
- Raptor researchers Clint W. Boal and Cheryl Dykstra are co-authors of Urban Raptors: Ecology and Conservation of Birds of Prey in Cities, a new book that explores the science of how these birds of prey have adapted to city life and what humans can do to support them.
- Mongabay spoke with Boal and Dykstra about the urban raptor species discussed in the book, what kinds of unique threats the birds of prey face in cities, and how important these urban populations are to overall raptor conservation.
On April 30, a pair of bald eagle mates in Washington, D.C. named Mr. President and The First Lady welcomed their newly hatched eaglet Victory to the world. Just a few days later, on May 3, Victory’s sibling Valor emerged from the shell, another new addition to an eagle family whose nest is perched high in a Tulip Poplar tree at the U.S. National Arboretum.
Eagle lovers around the world not only had the opportunity to watch the eaglets first appearance in the world, but will be able to continue watching them as they grow thanks to the D.C. Eagle Cam Project, which has provided a live feed of the eagle’s nest since the 2016-2017 nesting season.
This is just one of numerous nest cameras that have been set up in cities across the United States to give viewers an intimate look into the nesting activities of urban-dwelling birds of prey like eagles, falcons, hawks, and owls. These raptors represent a rare instance of wildlife thriving amidst the hustle and bustle of areas densely populated by mankind.
Raptor researchers Clint W. Boal and Cheryl Dykstra are co-authors of Urban Raptors: Ecology and Conservation of Birds of Prey in Cities, a new book that explores the science of how these birds of prey have adapted to city life and what humans can do to support them.
“We hope that readers come away with a greater understanding and appreciation of birds of prey and their role in our urban ecosystems,” Dykstra told Mongabay. “Urban areas can provide great conservation opportunities for some raptors, but their abundance in cities can disguise the fact that their natural habitats may be decreasing or disappearing.”
Mongabay spoke with Boal and Dykstra about the urban raptor species discussed in the book, what kinds of unique threats the birds of prey face in cities, and how important these urban populations are to overall raptor conservation.
Mongabay: Can you share with us one of your favorite stories from the book about people encountering urban-dwelling birds of prey?
Clint W. Boal: It isn’t in the book, but one of my favorite memories of urban raptor work was of a Cooper’s hawk nest placed in a tree in the courtyard between apartments in an apartment complex in Tucson, Arizona. The residents of the complex knew about the hawks, as we had put up a sign advising people not to walk under the nest, and some residents came out to watch us band them. Some people were interested in the hawks, some not so much, but basically, everyone knew about them and that as long as they didn’t walk under the tree, the adults would leave them alone.
One day, a resident contacted me to tell me that the nestlings had left the nest and were on the ground in the courtyard. She was concerned in that her son, who if I remember correctly was 9 or 10 years old, refused to come into the house for dinner; he had been sitting out in the courtyard all afternoon, literally hours, watching the fledgling hawks to make sure no one bothered them and to protect them from cats and dogs. The mom wanted me to talk to her son to assure him the fledglings would be all right and the adults would watch after them. That is the kind of passion these birds can stir in people and that was an experience that young man would not have had were it not for the hawks choosing to nest outside his apartment.
Mongabay: Do we have any population estimates for birds of prey in urban areas? Why is it important for us to understand these populations? Are they important to urban ecosystems?
Cheryl Dykstra: Researchers have very few population estimates for urban raptors other than urban peregrine falcons in eastern North America. However, some urban raptor populations are denser than those of their neighbors in more natural areas, and other urban raptors have smaller home ranges than rural birds — both of which suggest high-quality urban habitat. Compared to rural birds, some urban raptors reproduce at higher rates but others have similar or lower success. Little is known about comparative survival rates and even less about immigration and emigration.
Yet all of these population parameters are critical to understanding population dynamics of urban birds and whether the urban areas represent population sinks or sources. Some urban areas may be “ecological traps,” areas where the environment seems high-quality to the animal, but in reality circumstances such as high mortality or lack of breeding sites cause the population to be unsustainable. Studying raptor population dynamics is important for understanding how raptors fit into urban ecosystems, which are recombinant biological communities—that is, communities made up of native and nonnative species that do not normally live together in the wild. In different cities, different species come together to form a variety of communities depending on the native habitat, climate, particulars of the built environment, and anthropogenic disturbances. The complexity and variety of these interacting communities, combined with the adaptability of different raptor species, make urban birds of prey both challenging and fascinating to study.
Mongabay: We see plenty of “eagle cams” and the like — it seems people love to see these birds of prey roosting on rooftops and other urban settings. But do birds of prey face any unique or significant threats in cities? Are they well protected?
CWB: Good question. Even though several species are choosing to occupy and nest in urban settings, there are a suite of risks they face. Collisions with windows are quite common not just for raptors but for all birds. A substantial threat is secondary poisoning; poisons may be placed out for rats or pigeons and other ‘nuisance’ animals. When these animals become poisoned they become much easier for raptors to capture and consume. The raptor then can succumb to the poison as well. Again, this is a really substantive issue in many areas. Many raptors hunting along roadways can get struck by vehicles; this seems to be an especially prevalent problem for owls. Raptors can become entangled in nets, such as those on batting cages or soccer goal posts. And raptors can become trapped in man-made structures as well. I once had to rescue a great horned owl that had gone down a chimney and, because of the narrowness, couldn’t fly back up and out.
Mongabay: Is the existence of urban-dwelling raptors important to the conservation status of these birds?
CWB: I think so, at least in part. Birds of prey experienced heavy persecution in the 1800s and early 1900s. For most species, the persecution didn’t really subside until they became protected under the Migratory Bird Treaty Act in 1972. Once the raptors were federally protected from persecution, it was much less likely for people to shoot them or harass them. This, I believe, was the first step toward some raptors habituating to human presence and activities and taking advantage of urban settings.
Mongabay: Why were they persecuted by Europeans who were settling in North America? And when and how did they bounce back?
CWB: This is really a long story and some of it is speculative. In a nutshell, over 2000 years ago some raptors were trained to be hunting ‘tools’ in the art of falconry in Asia and the Middle East. From about 1100 to 1300, European nobility returning from the Crusades brought the art back with them. Falconry became an art and sport of the ruling class, and was also used as a means to acquire game. Some of the earliest game laws are centered on falconry. However, following the invention of firearms, which made hunting easier, and the rebellions against the ruling class, such as the French Revolution, raptors became 1) seen as a competitor for game animals and 2) symbolic of royalty. This, presumably, resulted in a pattern of persecution brought to North America by early European settlers.
Persecution was intense. There are stories and photographs of literally hundreds of raptors shot from the sky daily over migration points like Hawk Mountain in Pennsylvania in the early 1900s. Our own national symbol, the bald eagle, had bounties placed on it, some of which were not removed until 1940. In the 1940s and 1950s, researchers and game managers began to question this practice and the role raptors served in ecological communities. Research conducted by Frank and John Craighead and by Paul Errington led to a better understanding of predator-prey ecology. This resulted in reduced persecution for some species considered as ‘mousers’ but bird hunting hawks were still actively persecuted. In the 1960s we started becoming aware of the influence of DDT which was causing several raptor species, such as peregrine falcons and ospreys, to decline dramatically. This led to the Endangered Species Act in the 1970s, which originally included bald eagles and peregrine falcons, and inclusion of all other raptors on the already existing Migratory Bird Treaty Act. This was all probably at the nadir of many North American raptor populations, after which the population trajectory became positive and species were able to bounce back.
Mongabay: Are there certain kinds of raptors that thrive in cities? Conversely, are there any that particularly shun urban areas?
CWB: Yes, and we cover this in some detail in the book. Those that occupy cities tend to be 1) generalists in their behaviors and 2) those that normally occupy woodlands and forests, such as Cooper’s hawks and red-shouldered hawks, or some cliff nesting species like the peregrine falcon. Species that are specialized in food habits or occupy open prairies, such as ferruginous hawks, would not normally be in an urban area. There are exceptions, though. For example, burrowing owls are an open country species that does very well in vacant lots in urban areas.
Mongabay: What do birds of prey living in cities eat, primarily? Have they had to adapt their diet at all, or made any other adaptations, to living in cities?
CD: Raptors that can live in cities tend to be generalists and also somewhat flexible in terms of diet. Urban development alters the populations of many small animal species and these effects are transferred up the food chain to the top predators, including raptors. Populations of some disturbance-sensitive prey species decrease in urban areas, but other, more-tolerant species increase, including some “pests” such as rats and pigeons. Populations of some “desirable” prey species, such as birds that utilize birdfeeders, may also increase in urban areas.
Some urban raptors shift their diet to take advantage of the more available prey. For example, urban owls catch more nonnative rats than do owls in rural areas. Bird-specialists, such as Cooper’s hawks and peregrine falcons in North America, and northern goshawks in Europe, can eat very well with all the avian prey in cities. Some other species may shift their diets to include more birds when they inhabit urban areas. Raptor species that scavenge exclusively or even occasionally find abundant food at urban waste disposal areas and as road-kills.
Mongabay: What do you hope people take away from this book? And what impact do you hope the book has on conservation efforts for these birds? Do you make any recommendations in the book for how we can better protect urban raptors?
CD: We hope that readers come away with a greater understanding and appreciation of birds of prey and their role in our urban ecosystems. Urban areas can provide great conservation opportunities for some raptors, but their abundance in cities can disguise the fact that their natural habitats may be decreasing or disappearing. Urban raptors need suitable food sources and nesting areas, as well as protection from persecution, poisons, and other anthropogenic sources of mortality. In the book, we and our co-authors recommend preservation of remnant natural areas and other nesting sites, and maintenance of prey habitat and numbers. We encourage environmental education and continued efforts to reduce human-raptor conflicts in urban areas. Finally, we suggest important avenues of research that will allow us to better understand urban raptor ecology and conservation.
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