As top predators, hawks, eagles, falcons, and other raptors are often the first species to be affected by a range of environmental pressures; therefore, they play an essential indicator role in the health of our ecosystem. Researching the population trends of raptors provides a cost-effective and efficient means to detecting environmental change (i.e. habitat degradation and development, prey base decline, pollutants, climate change, and human disturbance), allowing us to take conservation action that is driven by scientific data. Serving as natural rodenticides and insecticides, raptors also play an important role in helping maintain balance in the natural world. For millennia, countless cultures have revered birds of prey as representatives of strength, freedom, and the power of nature. Today, however, their ability to survive is being threatened ever more. We at HawkWatch International work to ensure birds of prey are able to survive and thrive in the habitats they live, in order to maintain an environment that sustains human and wild animals alike.
What makes a raptor?
The word "raptor" comes from the Latin word "rapere," which means to seize or plunder. Today, the word is used to describe a group of birds also known as "birds of prey." All birds share some common traits, such as feathers, wings, laying eggs, and being warm-blooded; however, there are certain characteristics that set raptors apart from other birds. Raptors have these specialized adaptations:
|1. Exceptional vision
(to see prey from afar)
|2. Sharp talons
(to catch and hold prey)
|3. Hooked upper bill
(to tear apart food)
There are around 450 species of raptors worldwide. In North America, we have about 34 common diurnal (active during the day) and 20 common nocturnal (active at night) raptors. Diurnal raptors include: eagles, hawks, falcons, kites, Northern Harrier, and Osprey. Only owls are nocturnal raptors.
The Raptor Lifecycle
Fall migration, spring migration, summer nesting, and wintering make up the annual lifecycle of raptors. Understanding these predators during each phase paints the most accurate picture regarding their conservation status and needs. Many North American raptors make a daunting migration journey twice a year, with several flying as far south as South America, and as far north as Alaska. They spend the spring and summer in northern areas where they nest and rear young. During the winter, food supplies become scarcer and the birds fly to more southern latitudes where food is more abundant. There, they spend the winter before returning north to start the cycle over again.
As raptors migrate in the fall towards wintering grounds, and in the spring towards their nesting territory, they exert a tremendous amount of energy, often times covering thousands of miles within a matter of weeks. They navigate numerous borders and habitats, often facing multiple threats along the way. For scientists, migration serves as the most optimal time to keep tabs on overall population numbers, which over time can alert us to a decline in numbers of a particular species.
Spring is a critical time for all animals. Raptor nests typically hold 2-4 eggs, unlike songbird clutches that are typically made up of more than 4 eggs. If a nest does not fail entirely, as is always possible, it is likely that only 1-2 nestlings will successfully fledge from the nest. Many factors act as barriers to nestling survival, including human disturbance, low prey availability, and competition for increasingly limited nesting territory due to encroachment from human development.
Winter is the most harrowing time for raptors. The majority of young birds negotiating their first winter do not survive. Competition for resources looms large at a time when those resources are most scarce. Typically not social, raptors often concentrate in specific prey-rich locations during winter, returning each year if proven to be beneficial. These wintering habitats are therefore crucial to raptor population health, and require protection and management.
How do they migrate?
- Thermals: When the sun heats the surface of the Earth, warm air rises like bubbles from boiling water. Raptors utilize these thermals of warm air to soar and gain altitude.
- Updrafts: In mountainous areas, certain winds strike a ridge and are deflected upward, giving raptors an "updraft" that provides lift for raptors, and a near effortless flight.
- Leading Lines: During migration, raptors often follow geographical features that "lead" them south or north such as coastlines and mountain ridges.
- Obstacles: Raptors do not like to fly over large bodies of water because thermals do not develop over water, and there is nowhere to land if they tire during a water crossing flight.
What Do They Eat?
Raptors are birds of prey that eat other animals. Their diet includes small mammals (mice, gophers, rabbits, etc.), fish, reptiles, and amphibians. Some will even chase after birds (including other raptors) and eat them. Many raptors will also eat insects they catch in mid-air. Raptors are at the top of their food chain. When raptors eat prey that has been exposed to poisons, they can get sick and die.