What’s This Post About?
Birds’ are spectacular creatures that are capable of a lot of things. However, one of their features that people do not often notice is their eyes.
It is said that birds’ eyes are proportionately larger than the size of their bodies which essentially means that birds’ eyes are bigger than those of other mammals and humans.
A bird’s eyes are their most inconspicuous and functional feature. They help them see what’s going on around them and allow them to use monocular vision that enables them to focus on an object that isn’t in their line of sight but more to their side.
Some commonly known birds with large eyes are Owls, Eagles, Osprey, Tube-nose Seabirds, Penguins, Woodcock, Hummingbirds, Loons, and Vultures. It’s not rare to see a bird with huge eyes in your backyard. Most of them are pretty familiar to most of the states across the U.S.
Which Birds Have Big Eyes?
If you’re an avid bird watcher, then there’s a good chance that you’ve probably come across some bird species that have spectacularly big eyes. And this may have left you wondering whether what you saw is common or not.
Well, to address your curiosities, there are various birds with big eyes among the widespread species of birds that may or may not visit your backyard. In the United States, many birds can be found with large orbs, varying in both size and color.
Keep reading to find out more about birds with eyes.
1. Owls
Owls can be mostly discovered in all parts of the world except Antarctica; North America alone is home to nineteen other species of owls.
An owl’s eyes are vast, even for birds of prey, at 2.2 times the average size of same-sized birds. They are also strikingly binocular, with a 50-70% field overlap.
Did You Know?
In total, there are 200 different species of owls across the globe.
Their retinae are packed even more densely with photoreceptors (mostly all Rods) than their diurnal (daytime) relatives, with close to 60,000 receptors per mm2.
The Rod cells only contain one type of photopigment (called rhodopsin) instead of three, and they cannot transduce color by combined activation.
Instead, they are vastly more responsive to the presence of light through a process of signal amplification, wherein a single unit of rhodopsin can lead to a large and fast cascaded reaction.
This way, rod cells can respond to a tiny amount of photons. Owl eyes do have very few cone cells, which respond poorly in low light.
Fun Fact
Unlike most birds, some owls are nocturnal beings and hoot during the nighttime.
This iridescent structure lies behind the retina. It works by reflecting light through the retina along the light path, thereby making a limited number of photons available to photoreceptors for a sort of ‘second attempt’ at activation.
Lastly, one exciting thing that makes an owl’s vision different from other birds is its binocular vision. They can look at an object with both of their eyes at the same time. This gives owls the ability to judge height and distance.
2. Osprey
They are a diverse species. They breed throughout most of the northern Palearctic, with smaller populations in southwestern Europe and outlying islands.
They further range throughout most of the Nearctic from North Central Alaska to northern coastal Mexico (Nayarit), Cuba, Bahamas, and off Belize, and throughout the Middle East.
Fun Fact
Ospreys are also known as Fish Hawks because of their unusual appetite for fish.
Ospreys have a vision that is well adapted to detecting underwater objects from the air. The intense focus of their eyesight is due to a variety of factors.
These birds have big eyes for their size, and the eye is shaped like a tube which helps them produce a larger image in the back of their heads.
If a bird has many receptors, its ability to distinguish individual objects at a distance also increases significantly, especially when, as in Osprey, each receptor is attached to a single ganglion. They also have fovea with far more rods and cones than the human fovea.
There is a large number of receptors in the retina, which determines the degree of visual acuity. This provides them with spectacular long-distance vision. In general, ospreys have distance vision 6 to 8 times better than humans.
3. Wandering Albatross
Albatross is a shorebird; they only visit the shores to breed and end up spending most of their life drifting near to the surface of the oceans.
Their eyes are sharp, which aids them with their vision. The retina in their eye, gigantic celulares, has also been found in other birds like Manx shearwater, great shearwater, Kerguelen petrel, broad-billed prion, and common diving-petrel.
Did You Know?
The tubes in their bodies help them flush out the salt from their digestive system.
Their enhanced vision is characterized by the presence of distinctive cells grouped and usually more prominent than those found in the rest of its retina and morphologically look the same as the retina cells seen in cats.
The location and cellular morphology of the eye area suggest a function in detecting items in their line of vision field below and around the bill.
It is not concerned mainly with high spatial resolution but may assist in spotting prey near the sea’s surface as a bird hovers low over it.
4. Penguins
Penguins have taken a different path by evolving powerful lenses to compensate for a flat cornea adapted to swimming underwater. Among penguins, where the structure of the eye itself fails to adapt, perception, learning, and instinct may come into play.
Did You Know?
The Emperor Penguins are the tallest among all the penguins with a height of 120 cms.
A penguin’s eyes are modified to see clearly both when on the ground and underwater. They have binocular vision, which means that they can focus on one object with both of their eyes.
Penguins are sensitive to violet, blue, and green wavelengths of light, including ultraviolet light.
5. Woodcock
Woodcock is a brown colored bird with light brown lines running down its entire body. They are long-billed birds of damp and dense woodlands, allied to the snipes in the water-bird family Scolopacidae.
The woodcock is a game bird: it is often seen crouched among dead leaves, camouflaged by its buffy-brown, patterned plumage. A woodcock remains motionless until almost stepped upon and then takes off in a splurting motion.
Fun Fact
Woodcocks freeze when they sense a threat from the environment.
Its eyes are positioned farther back on the head than any other bird. A woodcock has a 360° field of vision which helps them look around and stay vary from predators.
An American woodcock probably has the most extensive visual field view of any bird, 360° on the horizontal axis and 180° on the vertical axis.
6. Humming Birds
Hummings birds are vividly colored dazzling birds with sharply pointed beaks native to southern America.
They inhabit regions where they find forests and open woodlands with plenty of flowers and meadows. Hummingbirds are stark-colored birds with sharp and pointy beaks.
If you’re an avid bird watcher, you may have noticed that these tiny birds have big eyes in proportion to their body weight, which also outweighs their brain mass. This is why they have an outstanding vision; they can see colors that humans typically can’t see.
Their vision is unique because there is a second fovea for enhanced sideways viewing in their eyes. In addition, the optic nerve in their eye carries messages from the eye to the relevant parts of the brain.
Fun Fact
They are the smallest among the migratory birds.
Birds, like mammals, have tiny blind spots lacking photoreceptors. The eye fiber is a poorly known structure made up of folded tissue that extends from the retina.
It is densely packed with blood vessels and appears to keep the retina nourished. It may help protect the retina from blinding light and aid in detecting and tracking moving objects.
Due to light absorption by melanin granules, a slight warming of eye nerves has been claimed to increase their eyes’ functionality metabolic rate.
This is thought to enhance nutritional release into the blood vessels, which are then absorbed by the retina of birds for increased nourishment.
Another layer that helps with hummingbirds’ vision is a layer situated behind the retina, containing many tiny capillaries. These provide oxygenated pressure to the retina while draining deoxygenated blood.
The melanin present in their eyes gives the inner eye its dark color and aids in preventing confusing light.
7. Loons
Four species of loons exist in the northern hemisphere including the Common Loon, the Arctic Loon, the Yellow-Billed Loon, and the Red-throated Loon.
The Common Loon is found in north of Wisconsin, Michigan, Minnesota, and Canada, whereas the other three species are found in the north of Canada and Alaska.
Did You Know?
Loons can stay underwater for about five minutes.
Loons are powerful, streamlined birds with red eyes, greenish-black head, long tapered beak, and black and white checkerboard plumage.
If you want to spot a loom out in the wild, you can purchase the Gosky Binoculars to help you spot these birds without having to put in much effort.
10X power magnification and large field of view, specially designed for outdoor activities
8. Hawks
Birds of prey, or ‘raptors’, are loosely defined as predatory birds that use their feet to kill. Raptor vision is legendary and has been shaped primarily by the pressures of prey pursuit and capture.
Some of these adaptations are obvious, such as the enormous relative size of raptor eyes —approximately 1.4 times greater than average for same-size birds—and a binocular orientation of bird eyes.
Other adaptations are seen on the cellular level. Multiple foveae are hallmarks of diurnal birds of prey, many of whom must combine panoramic sight with a stereoscopic vision for attacking target directly from a flight.
Did You Know?
Vultures have excellent sense of smell and sight.
These hawks also have a meager retinal convergence ratio, meaning that the photoreceptors don’t have to share as many nerve fibers as is typical, even for birds.
In other words, hawks tend to have a considerable number of photoreceptors and ganglion cells, which maximizes optical resolution.
Still, other adaptations involve the complex interaction of several working parts within their eyes.
For example, the shape of the deep central fovea may increase the size of the retinal image (and therefore the spatial resolution) independently from the number and spacing of photoreceptors.
The tremendous visual acuity of hawks, falcons, eagles, and their kin comes at a cost. With their cone-rich retinae and very low convergence ratios, diurnal birds of prey must trade-off brightness sensitivity as a consequence.
As light intensity decreases, raptor vision loses its edge—and in shallow light, their niche is overtaken by their silent, nocturnal brethren.
9. Eagles
About 60 species of eagle are from Eurasia and Africa. Outside of this area, just 14 species can be found—2 in North America, 9 in Central and South America, and 3 in Australia.
An eagle’s eye is one of the most powerful in the animal kingdom. Their vision is believed to be 4 to 8 times better than that of the typical human. Although an eagle weighs just 10 pounds (4.5 kg), its eyes are about the same size as a human’s.
Did You Know?
There are about 60 species of Eagles.
Light first passes through its cornea and then is refracted when passed through the cornea because it has a curved convex shape. The structure of its eyes helps an eagle to target its prey.
The layers of the cornea in raptors contain Anterior limiting lamina, Substantia, Posterior limiting lamina, Posterior epithelium (endothelium), all of which work together to give hawks an outstanding vision to target their prey.
Eagles have large transparent lenses that can change shape. The purpose of the lens to change shape is so eagles can quickly focus on an object accurately. The sclera is made of 15 small bones that give the eye its form and function to protect its inner structures.
The presence of rod and cone cells in the retina is more noticeable. The fovea of the retina of the eagle has one million cells compared to in humans. Eagles have huge eyes that take up more than half of their head.
Keep Reading!
In conclusion, the birds mentioned above with big eyes are full of surprises, and you may find many interesting facts and valuable information daily about them.
The interesting positioning of various cells combined with their vision can depend on other factors, such as weather conditions, changing seasons, light, etc.
Are you interested in knowing more about birds? Read this interesting post on birds with short legs – I bet you would be surprised.
You will be amazed to read about birds that have short legs. Continue reading to add to your knowledge about these fascinating birds.
By
David A. Swanson
Bird Watching USA
My name is David and I'm the the founder of Bird Watching USA! I started Bird Watching with My father-in-law many years ago, and I've become an addict to watching these beautiful creatures. I've learnt so much over about bird watching over the years that I want to share with the world everything I know about them!
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