The word “raptor” is derived from the Latin word “rapere,” which means “to seize.” Raptors are birds of prey that feed on live captured prey or on carrion. Typically, birds of prey have to kill things to make a living! Raptors may be diurnal, meaning they feed during the daytime, or nocturnal, meaning they feed at nighttime.
Raptors have three characteristics setting them apart from all other birds:
Raptors are predatory animals and are often on top of the food chain in most places where they live. Thus, raptors are bellwethers of ecosystem health. For this reason, the study of raptors in the wild and in captivity is like a window into the lives of all living things in our environment.
Very poorly, if at all. Raptors in general have a very poorly developed sense of smell. They rely heavily on their eyesight and, in the case of owls and a few diurnal raptors, their hearing. Some raptors, such as Great Horned Owls, feed on skunks and it is to their advantage not to have a sense of smell.
Almost 250 miles per hour. The Peregrine Falcon is the fastest animal on the planet. A Peregrine Falcon trained for falconry was clocked diving at 242 miles per hour by fitting her with a small electronic device to measure her descent rate. See the video here.
Falcons often fly thousands of feet up in the sky while hunting and migrating. Falcons trained for our “falcon-cam” project in 2012 have flown to heights of over 11,000 feet above sea level.
In most raptors, females are larger than males — a characterstic difference between the sexes, known as “size sexual dimorphism.” Female raptors tend to be about a third larger in size than the males, and in some species, such as Golden Eagles, females can weigh twice the amount of males. Coloration differences common in songbirds and waterfowl are also rare between the sexes in raptors, with the American Kestrel being one of the few raptor species in which this occurs. American Kestrel males have blue-gray colored wings, while the females have a duller, brown colored wing. As a rule, raptor males and females are best distinguished by their size difference.
A significant size difference exists between male and female raptors so that they are able to hunt different prey items and thus utilize two niches of the same shared territory. One explanation for this is that having a smaller male is more advantageous during the breeding season. Female raptors spend most of their time sitting on the nest when their offspring are very young, while the male goes off and hunts throughout the day. A male raptor’s prey base tends to occur in higher quantities than the female’s, since smaller organisms make up more of the biodiversity than larger organisms. For example, there are more ground squirrels than antelope in a given ecosystem, so there will be a greater number of small meals provided for the chicks while they are still young. When the nestlings begin to grow larger and are better able to regulate their body temperature, the female will leave the nest to begin hunting as well, since the young require more nourishment, and a broader range of prey can be hunted by the two parents.
Many raptors show a high nest territory fidelity preference, but not necessarily a fidelity to a past mate. For example, if a pair of eagles successfully raises offspring at a territory this year, they will likely return again next year to the same territory. If both the male and female arrive at the same site, at the right time, they will likely pair up again for the new breeding season. If one is late, they will be replaced if there are other suitors in the area. The first to arrive back at the territory, either the male or female, does not repel other eagles of the opposite sex in the hopes of the past year’s mate returning. The tardy mate from the previous year may attempt to reclaim their territory, and eject the interloper, but this is not done by the opposite sex mate which arrived first. It is well agreed upon that raptors will return to their nest site year after year and reestablish their original pair bonds upon arrival; although it is unclear as to how strong this bond is in comparison to nest fidelity.
Often eagles, and many other species of raptors, are seen locking their feet together and spinning towards the ground. This is not a friendly interaction but has oftentimes been misinterpreted as mating or courtship. Each raptor is sinking their talons into the foot of the other raptor as they spin earthward, which is painful and potentially life threatening should the wounds become infected since this would debilitate a mate’s ability to hunt and support its young. This type of fighting is commonly referred to as ‘crabbing’. Eagles do however perform aerial courtship displays with the male and female exchanging food mid-air. Often, the male dives and rises near the female, doing his best to impress her with his aerial flying abilities.
A fledgling is a young bird that is able to jump out of the nest but has not yet learned to fly. Fledglings are often mistaken for injured birds due to their vulnerability on the ground and inability to fly very well. During this stage the parents continue to feed and care for their young, who are usually able to fly within a few days time. Young birds often jump out of the nest early after weighing the pros and cons of being in a nest vs. being on the ground, since raptors such as owls often get crowded in the small nests that they take over, and can be exposed to aerial predators such as eagles and other owls. Fledglings are often exposed to dangers on the ground such as foxes, other raptors, and humans, but this period of fledgling is a necessary part of a bird’s life.
Our resident raptors and patients are provided a diverse diet, including rats, mice, chick, chicken, quail, and rabbit. Fish is also provided for species such as Bald Eagles and Osprey. Our raptors are provided a whole diet, including the bones and feathers, this ensures that natural mechanisms such as crop cleaning take place. By allowing feathers to pass through a bird’s crop, this portion of the digestive system is purged of many disease-causing bacteria.
The crop is an expanded, muscular portion of the digestive tract located by the gullet. This enlarged part of the esophagus is used for softening or storing food for a limited period of time before passing it through the rest of the digestive process. After a meal, the crop will be filled with food and appear as a bulging area at the top of the bird’s chest. Most raptors, except for owls, have a crop, although owls will still store food in a similar region of their esophagus.
Raptors process their food in order to retrieve the essential nutrients and separate bones or feathers from everything else by forming a pellet or casting in their muscular stomach known as the gizzard. This way, indigestible materials like bones, feathers, and fur, can be regurgitated in a compact casing. Owls are best known for their pellets, since they are less likely than other raptors to digest bones, thus their pellets are formed in such a way that ornithologists can dissect the pellets to learn about an individual bird’s diet. Other raptors, such as hawks and falcons, form pellets or castings full of similar indigestible materials, and dispose of them in their usual nesting or perching sites.
Their carnivorous diet usually means that raptors do not require any water to remain hydrated, since meat contains a substantial amount of water. They do enjoy the occasional bath.
Our main goal in wildlife rehabilitation is to help an injured or sick raptor make a full recovery so that it can be released back into the wild, but sometimes that is not an option. Complications such as shattered joints, bones that do not heal properly, or significant head trauma are all issues that can affect the outcome of a rehab case. When a raptor is not able to be released, yet a good quality of life is still ensured, the bird becomes a candidate for education programs. Raptor centers around the country often apply to care for birds that need to be placed in a safe captive environment. Our resident raptors were all previously brought into other rehabilitation centers and were deemed un-releasable due to debilitating injuries, so they now reside with us as our education birds.