Birds of Prey are scientifically known as Raptors, the apex predator of the bird world, living on an all meat diet.
They do not eat berries & seeds & are 100% carnivorous!!
Feeding on a whole range of prey from other birds, insects & rodents all the way up to deer & even monkeys.
Keeping them at the top of their game they have evolved a whole array of adaptations from their sharp beaks, to
their sharp eye sight, all the way down to their extremely sharp talons!
We have all heard the phrase of "I'm watching you like a hawk" & this is because of their long- rang vision,
estimated to be around six times better than our own. This is all down to the structure of their eyes. Taking up a
huge proportion of their skull & in the case of an Owl, it can make up to 5% of their total body weight, when you
look at an Owl you can actually see though the lens as it looks like a glass dome over the eye, ideal for capturing
light. With their eyes being so large they are held in place, by being fixed to the socket which leaves them with very
little or in case of an Owl no degree of movement at all!
But its what is at the back of a Raptor's eye that makes them
so special. The Retina the most sensitive part of the eye has a
small dip in it this is call the Fovea. Within the Fovea is
where all the rods and cones are contained; Rods are
responsible for vision in low light levels known as scotopic
vision. Owls have 1,000,000 rod cells per square millimetre
where we only have 200,000 rod cells per square millimetre.
Where as the Cones are active at higher light levels;
(photopic vision) we have 3 types of cone sells sensitive to
red, blue or green light which allows us to see in colour but
Raptors have an extra cone for tetrachromatic colour vision.
This extra cone expands the visible light spectrum, allowing
them to see ultraviolet frequencies. It is not seen to been
used in all species of Raptor but Kestrels use this
adaptation to their full advantage. Urine reflects ultraviolet
& rodents leave a trail of urine behind them wherever they go, so they can simply follow the trail until they
spot the movement of a mouse then stoop down and grasp their prey.
However Raptors are so highly evolved they don't just have one Fovea they have two! The Centralis Fovea & the
Temporal Fovea; which gives them triangular vision. The Centralis Forvea is used to centralise its victim detecting
the slightest bit of movement; this means a Raptor see you most clearly when they turn their heads about 40
degrees to one side. Also explaining why falcons spiral towards their prey. Although it's not the most direct route
they can stay fixed on with full focus while continuing to gain more speed by staying streamlined. Where if they
were to fly directly at their prey turning their head to stay focused they would lose around 50% of the speed
everytime they turn their head. The Temporal Fovea is used for binocular vision. Like us their eyes are forward
facing with a giving them total of 170' field of vision, with around 45- 55' overlapping for the binocular vision.
Raptors have a 200 degree neck rotation & in the case of owls a staggering 270 degrees!
Raptors have excellent hearing. Owls have the best hearing of all animals, due to the location of their ears. Hidden behind a layer of feathers
(the auriculars or ear coverts) is used to funnel sound to the ear opening; a small hole (the external auditory
meatus) this is a canal into the middle ear. They have one on each side of their head however what's interesting
about them is that their asymmetrical on the left its just behind the eye above the beak line and the right is below
the beak line With ears at different level causes sound to hit them at different times so they are not only able to hear which direction the sound is coming from like us, but to pinpoint the exsact location.
Owl take hearing to a whole other level.Owls have around 95,000 nerve cells within the saccule giving them the
ability to hear sounds 10 times fainter than we can detect. This is down to the placement of their ear like other
raptors they are asymmetrical but they also have other adaptations such as large ear openings, but unlike other
species of raptor they have a skin flap forming the outer ear which are hidden by deep, tightly packed, soft feathers. An owls facial disk feathers are the most important part of an owls hearing, without their disk feather they would not be able to hunt so effectively by night. They are arranged like parabolic dishes, which traps sound & focus the
sounds into the ears so by slowly moving their head they can create a 3D picture with their hearing alone. Species
such as the Ural Owl have have an extremely large facial disk (the bigger the disk the better the hearing) this is
because the prey they hunt in generally hidden by 8 inches of snow, if the mouse or lemming stops they can tune
in to its organs moving. Before puncturing through the snow and grasping their prey.
Raptors beaks are set apart from all other birds they are strong, curved, with sharp edges. They use their beaks to
plumb feathers & fur from their prey, cut & tear their food, to eat, and to feed their young along with drinking,
courtship, fighting & defence, preening & shuffling around their eggs . Even though Raptor beaks all share certain
characteristics, there is some variation in beak size, shape, and function among the different raptor species; such as falcons they have a sharp triangular- shaped ridge at the the front of beak know as the tomial tooth which they use
to kill their prey effectively, by biting its neck and severing the vertebrae.
The beaks structure is composed of two jaws the Upper Mandible (Maxilla) and the Lower Mandible (Mandibular); built up internally by a complex three dimensional network of Trabeculea (boney spicules) seated in soft connective tissue & surrounded by a hard outer layers of Keratin know as Rhamphotheca.The Maxilla is supported by a three
pronged bone called the Intermaxillary. The upper prong of this bone is embedded into the forehead, while the two
lower prongs are attached to either sides of the skull. At the base of the Maxilla there is a thin sheet of nasal bones
this is attacked to the skull at the nasofrontal hinge, which gives mobility to the Maxilla allowing it to slide forward
and backward enabling the beak to opening exceptionally wide; which is ideal for swallowing prey such as mice
whole.The Mandibular is supported by a compounded bone composed of two distinct Ossified Plates (Rami) joined at the distally (the point furthest from the point of attachment to the body) making the bone V- shaped, attached
on either side of the head to the Quadrate bone. At the proximal (where the appendage joins the body) of the Rami
is where the jaw muscles are attached which allow the bird to open and close their beak. These muscles are usually weak in most species of bird however in Raptors they are extremely strong ideal for aim in biting, holding on the their prey & crushing bones
What makes a bird of prey a bird of prey? The fact they eat meat? Nope, all birds eat some form of meat or protein;
even humming birds they will often take aphids & other small insects. It's the way they use their feet; every bird
have six functions for their feet whatever it may be; running, swimming, climbing, scratching etc it always adds up
to six. Where birds of prey have seven functions for their feet, they use their feet to kill!
All Raptors have four toes, three forward & one backwards or in the case of owls & Osprey their third toe has the
ability to rotate backwards giving better grip around its prey. Each toe ends with a shape talon; the outer layer of the talon is made up of keratin, with a central quick of blood which enables continual growth, keeping them long and
sharp even after everyday wear & tear. The back talon also know as the hallux, is often longer than the other three
forward faceing talons. When a raptor catches its prey, the raptor will typically push the large hallux through its
prey. Perigrines often use the hallux to rake down the back of its prey when coming into contact at high speed,
slicing it's prey open.
The legs & upper side of the feet are are covered in yellow or gray scales or what we call booted (covered in feather). The skin on the base of the foot is covered with spicules (1000's of small lumps) which gives good grip onto their
prey & perching; but their main function is they cause reaction the second the fur, scales or feather of their prey
comes into contact with these sensitive spicules their feet slam shut. The toes work on a sort of ratchet system &
with each contraction the talon are driven deeper & deeper crushing and stabbing its prey until it ceases to struggle. The advantage of the ratchet system is that it enables the bird to exert a massive amount of grip which, can be
maintained even if the muscles are relaxed. The disadvantage is that sometimes the bird has difficulty unlocking the ratchet and it can be involuntarily locked into the object of its attentions, which is not a happy state of affairs if
you’re a buzzard locked into a rabbit when a fox comes into view.
Feathers & Wing Shape:
Feathers first evolved from scales during the Jurassic Period over 150 million years ago. Therapods - a family of
carnivorous dinosaurs that walked on their hind legs had began to evolve feathers due to climate change the earth
began to get colder and through natural selection Therapods evolved feather to keep them warm but feathers didn't look as they do today. They started life similar to the down feathers we find on birds today they are a fluffy feathers
located close to the body, underneath the contour feathers to help insulate a bird and keep it warm; that's right the
T- Rex was fluffy! But over many more millions of years they evolved further, contour feathers & flight feathers had formed. Contour feathers cover the bird’s body. They give the raptor a sleek, streamlined shape when it is flying &
keep the body dry when it is raining; they are stiff, flexible & very strong yet lightweight. Flight feathers are on the
wings and tail; these feathers are shaped to fan the air giving the bird lift to help the bird get off the ground, move
about in the air & land safely. The tail feathers also help the bird steer and stop. Though Therepods had not yet
mastered powered fight smaller species began to use their feathers to glide through trees giving them an added advantage of being able to cover more ground easily & attack their prey from above. But over many more millions of year their wings evolved further & adapted shape to suite styles of flight.
Today's Raptors have also evolved different shaped wings to suite their style of hunting. The three main groups are Broad-winged, Short-winged and Long-winged.
Broad- winged such as Buzzards, Eagles & Vultures have a long, broad wing, with finger tip like edges; ideal for capturing the hot air of a thermal allowing them to get height with very little effort allowing them to search for prey over large areas.
Short - winged such as Goshawk & Sparrow Hawk the true hawks or scientifically known as Accipiters. They have short stubby round wings & a long tail for quick take-off speeds, sprinting ability & agility ideal for hunting in forests.
Long- winged these are the falcons, they have long narrow pointed stiff wings without slots. These wings give high speed and fast, level flight; giving them the ability to catch fast moving aerial prey.
Feathers are composed of B- keratin. Scales and feathers develop in a similar fashion. Feathers are incredibly strongand yet are incredibly flexible. To allow both lift & forward movement, feathers can bend at almost a right angles. Feathers are made of a shaft, called the rachis and the vanes on either side. Vanes are made of barbs that are arranged side by side up the shaft of the feather. Barbules grow from the barbs, which have tiny hooks that interlock in a similar way to hook & loop fasteners. The short bare part at the base of the shaft is called the calamus. If viewed crossways, the calamus is basically hollow. There is an opening at the very tip of the base where the blood
supply entered the feather when it was growing. Once a feather is fully grown, the supply of blood is sealed off and the feather itself becomes “dead,” similar to the ends of human nails. On most flight feathers, the vanes are of unequal length. This gives feathers the ability to twist under air pressure. The large flight feathers are attached to bone by connective tissue, and have little or no down at the base. All other feathers are attached to muscles below the skin. Because birds are covered by feathers, they do not feel things on their skin in quite the same way people do. Their feathers do transmit sensations of pressure and the skin itself is quite sensitive. The area of skin around the beak (called the cere) is sensitive to touch, and the tongue is good at feeling textures. Even though a raptor’s feet are pretty tough and scaly looking, they are sensitive to touch too. It is important to note that birds of prey do NOT enjoy being petted or stroked. Birds take care of their feathers every day by preening them with their beak. This keeps them in the right place and also spreads oils on them from the preen gland above the bird’s tail. The oils from the preen gland help the feathers stay shiny and resist ultra violet radiation from the sun. They may be important for making vitamins (vitamin D). This is why pet birds can look scruffy, if their owners stroke them too much and rub the special oils out of the feathers.
Owls have specially adapted plumage to effectively eliminate sound while flying; allowing them to hunt their prey with acoustic stealth. The three main attributes that combine to give an owl silent flight are:
Combed stiff feathers along the leading edge of the wing feathers also known as barbs; these feathers break up sound & turbulence, unlike the hard trailing edge of the conventional wing that gives the wing its acoustic signature.
Fine tattered fringe feathers on the trailing edge of the wing feathers, this feature allows air to pass through easily & break up the pressure waves we hear as sound.
Layers of velvety down feathers cover the wings, body & legs; the thickness of the layers of feathers & the roughness of each feather assist to absorb sound frequencies.
Owls manage to fly so silently thanks to the special build of their flight feathers. The leading edge of the primary flight feathers has stiff fringes that reduce turbulence, while the trailing edge has soft, frayed-like edges to reduce remaining turbulence. Downy feathers throughout the wings also help dampen sound. Owl feathers are so great at reducing turbulence for silent flight that researchers have looked into mimicking the feather structure to improve airplane wings, fan blades and other items.
It's popularly thought that owls can turn their heads completely around, but though these birds are fascinating creatures of the night, they aren't poltergeists. However, the myth came from somewhere, and it's because owls can turn their necks by 135 degrees in either direction, giving them a total of 270 degrees of movement. Because they can't roll their eyes in their head, they have to have extra neck movement to see around them. The adaptation comes with twice as many vertebrae in their neck as the average bird, and special blood vessels to keep circulation moving even when twisted around
Owls use filoplumes, small hair-like feathers on their beaks and feet, to feel out food when they catch and eat it. The filoplumes are short and have a few small barbs at the tips. These help the owl better sense vibration and pressure, letting the owl know what is going on and how to react with objects it holds.
The zygodactyl feet of owls are structured so that two toes face backward and two toes face forward, which gives them an excellent grip when resting on a tree branch. The structure also allows for an outer toe to swivel forward or back when needed. Generally, owls have three toes facing forward and one backward when flying, and they swivel their outer front toe to the back when clutching prey or perching for a solid grip.
Though owls have keen vision, they rely greatly on their hearing when hunting. Owls have ears that are placed asymmetrically on their heads (and many species also have asymmetrically sized ears) which allows them the ability to triangulate the location of sound and perfectly pinpoint the source. When a sound is equally loud in both ears, the owl knows it has zeroed in on both the source and distance.
Owls gulp down their prey but they can't digest everything. So, they regurgitate the parts they can't process, including bones, scales and fur. These pellets tell the story of what local owls have been dining on, as scientists (and middle school kids) can easily pick out and identify the various bones of prey species.