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Migratory Birds - Birds of Prey

 

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Many different types of birds kill in order to eat. Some eat rodents; others eat fish, worms or other living creatures. However, birds that use their beaks in order to hunt do not necessarily fall into the category of 'birds of prey'.

 

 

Griffon VultureGriffon Vulture (Nikon D800)

 

What is a Bird of Prey?

Roughly speaking, a common characteristic among all birds of prey is their ability to seize, carry and even kill the spotted prey with their feet. They are also equipped with keen vision, powerful talons and a strong arched beak that is extremely sharp along the edges.

 

Greater spoted eagleWhite-Tailed Eagle(Nikon D800)

 

Are the kingfisher or the crested lark birds of prey? (See answer below)

King Fish After Catching Turtle
Kingfisher After Catching Baby Turtle (Canon sx40 HS)

 

Crested larkCrested Lark catching its food (Nikon D800)

Answer - No, neither the kingfisher nor the crested lark are considered birds of prey. While both feed on living creatures, they do not seize and kill their prey with talons.

Birds of prey, also known as raptors, are not to be confused with other meat eating birds.

 

Predetor
Steppe Buzzard (19)

 

Day and Night Raptors

Birds of prey are divided into two main groups, the diurnal (day flying) and the nocturnal (night flying) birds of prey.

The day-flying raptors include a few families - among them are:

  • Accipitridae: hawks, eagles, buzzards, harriers, kites and old world vultures (birds of this family can be found in all continents except Antarctica)
  • Pandionidae: the osprey (a fish eating bird of prey)
  • Sagittariidae: the secretary bird (unique to Africa)
  • Falconidae: falcons and caracaras (making up the majority of the day-flying birds of prey).

 

Black-Winged-KiteBlack-Winged-Kite (Canon sx40 HS)

 

The night-flying raptors – the owls - are members of the order Strigiformes and are classified within the following two families:

  1. Strigidae: (true owls or typical owls)
  2. Tytonidae (barn owls)

 



 

Day-Flying Birds of Prey

Predetor
Steppe Buzzard (20)

Sight

Sharp vision is a necessity in the world of the birds of prey. Their eyes are so large that they occupy most of their skull. We actually see only about one eighth of the real size of the eyes. For visualization purposes, if the proportion between our eyes to our body was the same as it is for the Falcon, then our eyes would be the size of a basket ball.

Because raptors' eyes are so big, not much room is left for muscles. As a result they have a limited ability to rotate their eyes, only some 10 degrees or so, but nature compensated them in other ways.

predetor face
Steppe Buzzard (21)

When we humans are exposed to sudden extreme change of light, we need to wait until our pupil will adjust to the new conditions. Raptors, on the other hand, have the ability to instantly control the adjustment at will. Moreover, this can be done on each pupil independently.

 

Predetor
Steppe Eagle (22)

Unlike humans that can process about 24 pictures a second, raptors can process 70 to 100. This places them at a level that allows them to react instantly to even the slightest movement of a potential prey. Raptors have the ability to see through some of the ultra violet spectrum of light as well. This enables them to also detect urine traces of rodents, thus knowing where to concentrate in the search for food.

 

Predetor
Common Buzzard (23)

Generally speaking, the density level of the photoreceptors in the eye corresponds to the level of visual acuity. The ratio connection of the photoreceptors to the nerves determines the resolution of the picture that is seen.

 

Predator
Common Buzzard

While humans have about 200,000 receptors per sq. mm, the common Buzzard, for example, has within the same area about 1 million receptors. Birds also have a higher ratio connection of photoreceptors to the nerves than humans have. Raptors' eyes have a mechanism that can magnify the center of the picture they focus on by around 40 percent.

With all the characteristics above, no wonder some of the day-flying raptors have the ability to spot prey from hundreds of meters, and sometimes from a few kilometers, and why some of the owls have the ability to see almost in total darkness.

 

Predetor
Common Buzzard

The eyes of diurnal birds of prey are located on both sides of the head; they have keen sight especially for long distances and the ability to see about 270 degrees at the sides without moving their head and about 90 degrees in front.

 

Black Winged Kite Kestrel
Black Winged Kite (Canon sx40 HS) Kestrel

 

Hen-Harrier
Hen-Harrier, flying over Gamla. See more information about birds of prey in Gamla.

 

 

Feet

Apart from their sharp vision, which is estimated to be about 3 to 5 times stronger than human vision, the feet of birds of prey are their main tools for survival.

 

Predetor-talones

 

Raptors have 4 toes that are scaled on the upper side like the leg itself. On the underside the skin is bumpy, which allows the bird to have a better grip on the prey when captured. Generally, the middle toe points forwards and the rear toe points backwards. The other 2 toes have some flexibility moving sideways as needed.

There are some differences among the raptors, depending on each one's “specialization”.

Marsh Harrier, seconds after seizing a fish that is still being held in its talons

The osprey for example has particularly rough skin on the underside of the toe in order to be able to hold a slippery fish better. He can also maneuver his toes into a position where 2 point forward and 2 point backward, for the same purpose.

Bird hunters, such as falcons and some hawks, have particularly longer middle toes with bumpier underside skin on the toe in order to have a better grasp around the body of the prey.

The talons are the tools that the raptors use to seize and kill their prey. They are made of keratin, which is the same as our finger and toe nails. 

The raptor will usually aim to seize its hunt at the head. Once it has succeeded, it drives the sharp talons strongly into the prey until it kills it.  In some cases the grip on the prey is so strong and the talons penetrate so deep that the raptor has difficulties to release them. The talons grow continuously throughout the raptor's life. Wear and tear keeps their size adjusted.

 

Beak

As with the talons, the raptor's beak is made of keratin. Their beak is curved and sharp at the edges in order to allow them to cut the flesh of the hunt. Each type of raptor's beak has a slightly different shape depending on their “specialization”.   

predetor-beak
Steppe Buzzard (24)

Apart from falcons and vultures, birds of prey usually do not kill their prey with their beaks. Those who do, have an exceptionally strong beak. The American Black Vulture, for example, is capable of killing a piglet with its physically powerful bill. The beaks of such raptors, due to intensive use, require cleaning and refining, which is taken care of by rubbing them against hard surfaces.

 

Hearing

Located on both sides of the head, diurnal raptors' ears are not big. Although the hearing ability of birds of prey is finer than ours, day-flying raptors do not usually use their hearing to trace their prey.

 

Night-Flying Birds of Prey

The owls are characterized by un-proportionally big heads compared to the size of their short strong bodies, short necks and short tails. Their food includes rabbits, insects and rodents.

Unlike diurnal (day-flying) raptors, most of which have excellent peripheral vision due to having their eyes positioned on two sides of the head, the nocturnal owls have, like humans, both of their eyes in front. The eyes focus together on the same object allowing 3 dimensional image perception. However they have a very limited peripheral vision and, like us, rely almost completely on their binocular vision.

Eagle-owlEagle Owl

 

Similar to other raptors, the size of the eyes in the sockets is so big that it limits the mobility of the eyes since there is not much room left for muscles. Consequently, their horizontal sight is limited but they are compensated with the ability to turn their head some 270 degrees horizontally and some 180 degrees vertically. Also, for the same reason - inadequate eye movement - owls fail to see motionless prey clearly from very short distances after it is killed. Touch sensitive feathers located on both sides of its beak, as can be seen in the picture above, compensate them for this disadvantage, thus allowing them to feel and sense food.

A very common mistaken belief is that owls can see in complete darkness. This is not correct. If there is no light at all, owls will see nothing, same as humans. The truth of the matter is that there is seldom, if at all, a night of total darkness.

Nature supplied the owls with 2 strong tools to help them locate a possible prey in the dark, keen eyes and an excellent sense of hearing.

Eagle-owl-talonesTalons of Eagle Owl

 

The owl’s beak is strong, short, facing downwards and hooked at its end, perfectly designed to grip and tear the prey. It is curved strongly downwards thus allowing the owls a clear field of vision.

While the owl’s main tool for hunting is his feet, it is able to kill a prey by a sharp swift hit of his beak, at the back of the hunt's skull.

The owl’s nostrils are located at the top, near the base of the beak. Basically owls are not granted with a strong sense of smell but their hearing is acute. Owl’s hearing range is wider than humans. An owl can pinpoint its potential prey in dark, without use of sight, but by hearing alone.

 

Hearing

The ears of the owl are not level with each other. For example, the barn owls’ left ear is positioned higher than the one on the right. Having a disk like shape that can be changed at will, the face, acting like a radar, can direct sound more efficiently into the ear’s openings.
When a sound is produced by the prey, the owl can point toward the prey’s direction precisely because of the time difference that the sound is perceived in the ears due to their uneven distances from the prey. 

The moment the owl senses the time difference of sound heard in the ears, it moves the face until the noise is heard simultaneously in both of them. At this point the direction from where the movement was heard is locked and the potential hunt is doomed. Studies show that an owl can detect a time difference of about 30 milliseconds. Studies also revealed that the area in the brain that is responsible for hearing is much more complex in owls then it is in other birds.
The owl’s ability to adjust the direction of its flight instantly, together with its silent flight owing to the structure of its feathers, give the prey no chance.

 

The ecological importance of the birds of prey has been known for a while. The activity of owls, as well other types of raptors, helps reduce the expansion of reptiles and rodents that are usually harmful for agriculture.

 

 

 
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