Tag Archives: Birds

Why do pigeons thrive better inside cities than any other bird?

Pigeons are common in cities because buildings more closely resemble their natural nesting sites.

Rock doves nest on the side of cliffs. Not in trees or shrubs.

Human buildings provide lots of ledges for nesting.

Combine that with the fact that they’re harmless, (so we don’t kill them for being pests) not tasty (so we don’t kill them for food) and their natural predators cannot hunt well in cities (falcons end up nose diving into walls using their usual tactics, larger predators avoid humans) and you’ve got the perfect combination for a species to cohabit our cities with.

Seagulls are also very common in cities in the UK for the same reason.

Why are bats believed to be blind?

The bats, also known as flying foxes, are creatures of night, just like the owls. They primarily feed on fruits, nectar and insects. The insectivorous species play an important role in the regulation of insects in the planet. It will be astounding to know that a bat can eat nearly thousand insects in one hour. There are many interesting misconceptions about bats, most probably having originated from their nocturnal lifestyle. These include their propensity for sucking blood and the habit of getting tangled in people’s hair etc.

However, the most popular one of all those false assumptions is that the bats are blind. This concept has even contributed the saying “blind as a bat” to English and its versions in other languages. The phrase is used to denote a person with poor eyesight. However, contrary to the popular belief, bats are not blind. There are more than a thousand species of bats, and all of them have fairly good vision although their hearing power outclasses the sight. They are sensitive to the variation in light levels and they use this prospect to determine the time to get active for hunting.
Bats are primarily divided into two categories; Mega bats (megachiroptera) and Micro bats (microchiroptera). The former, lower in number, are larger species in the family and have large eyes. They use eyesight to hunt and navigate without hurdles. However, the micro bates, which constitute for around 70% all bats, have small eyes and rely on the technique called echolocation for hunting and flight without obstacles. Also referred to as second sight and sonar sight of bats, echolocation is like a biological RADAR system. Bats are capable of producing high frequency waves. They emit these signals and listen to the sound waves bounced off any prey or obstacles in their path. This auditory information is then converted into a visual map in their brain, helping them see in dark. The thing that is subject to debate is whether this feature evolved after their ability to fly or not. However, even micro bats use vision to detect the objects outside the range of echolocation. The function only works between ten and twenty meters.
Bats don’t have great ability to distinguish between colors. However, they have much better sight than humans in certain conditions like low light. The most probable reason for the evolution of belief that they are blind must be their pattern of flight in night. Bats move rapidly in the dark, occasionally just grazing against us, which may prompt us to believe they don’t know where they are going.

You might also like:

Why vultures don’t get sick from eating rotten meat?

The humans can barely stand the smell of rotting flesh, let alone think about eating it. The mere thought will bring us a sick feeling. Many animals on the other hand, eat dead meat without any problems. And when it comes to the case of vultures, it is nothing short of incredible. They have no qualms about eating carrion that has been decaying for quite a while. In fact, they prefer to have such a kind of meal. Vultures can feed on dead animals in any stage of decomposition. Though they are known to prefer mammal carrion, they would also eat carcasses of reptiles, fishes and other birds. The vultures usually locate their food with sight or smell.
The decayed meat is playing ground for different kinds of bacteria that are dangerous to human body. These include the bacillus anthraces, which are known for causing anthrax. These bacteria are poisonous to most of the creatures. Studies have found out that the stomach of vultures is filled with two species of bacteria, both very dangerous. The first one is the flesh-degrading fusobacterium, which causes blood infections and the other one is clostridium, which can produce deadly botulism toxins. These are also found on the face of the birds. Yet, vultures seem fine with it. The question is how do they do it?
The major part of the vultures’ ability to eat decaying carrion can be attributed to the highly acidic character of the gastric juices in their body. These juices are so strong that they will kill most of the deadly bacteria before they can get into intestines and begin their activities. To get a clearer picture, you would like to know that the stomach acids of vultures are 10 to 100 times stronger than those in humans. While the human gastric juices have acidity around 2 on the pH scale, the vultures’ is close to zero. That is, the digestive system of the vultures is very harsh compared to humans or any other scavengers.
It seems that the vultures have developed a strong digestive system over the years, especially considering they are spending their whole lives near rotten flesh. It is also apparent that they have built some tolerance to the deadly clostridia and fusobacteria. Interestingly, these bacteria seem to help the digestion in the birds by breaking down the rotten flesh. The immunity towards these toxic bacteria appears to have evolved over thousands of years. However, there are things that even vultures can’t stand. Lead and certain drugs, which are incidentally fine to humans, are toxic to them.

You might also like:

Why are some animals and birds albino (without color)? And why albinos are few in number?

Sometimes an offspring can have a trait which is unlike the traits of both parents. The information about traits is in the form of DNA in genes, one of which may completely hide the effect of another gene and thereby become a dominant gene. A gene whose effect is eclipsed by a dominant one is known as a recessive gene.
Albino peacock
The rule of heredity mandates that whenever a dominant and a recessive gene pair together, the dominant gene controls the trait. In rare cases, however, a recessive gene overshadows the dominant one and causes an offspring to have traits that neither parent has. Every so often, the new trait results from a mutation, i.e. change in the DNA contained in gene. (DNA is just four basic chemicals or bases–A, C, T and G–strung together like steps on a spiral staircase). The change occurs when DNA makes copy of itself, wherein the whole or small section of the DNA is rearranged. As a result, a different DNA message is passed along to the offspring.
One example of mutation is albinism, a condition in which a bird, animal or a human being is unable to make a substance called melanin. It is this pigment which in different concentrations gives coloration to the eyes, skin, hair, and feathers. Lacking melanin, albino organisms are usually colorless and appear snow-white. In the wild, albino birds and animals can not stay as safe as other members of their species. Normal birds and animals, using a combination of various colors, provide themselves which elaborate and highly effective disguise. They have evolved an uncanny likeness to elements of their environment such as leaves, rocks, grass and pebbles to avoid being noticed by predators. Albino types are easily noticed, and so cannot hold out for long. On the other hand, an albino predator (such as snake) is easily noticed by its prey, which makes a hasty and timely retreat. A snow-white peacock, shown above, has its own problem. It cannot attract a female, due to absence of the bright purple, blue and green feathers. This explains why albinos are few in number. In evolution, their condition stands to their disadvantage in many ways.

Additional reading:
Albinism (Wikipedia)

Related posts:

Relative to its body size which bird lays the largest egg?

The ostrich is clearly ruled out. It weighs about 140 kilograms, but the 1.4 kilogram egg is not exceptional in relation to the size of the bird. The egg is just 1% of bird’s own body weight. The chicken-sized kiwi of New Zealand holds the record in the bird world for laying the largest egg in proportion to the female’s size.
A 1.8 kilogram kiwi produced an egg that weighed nearly 0.450 kilogram — 25% of her own weight. The male incubated the egg in a moss-lined nest in a burrow. Considering the egg’s size, the incubation period lasted 75 to 80 days.

Additional reading:
Kiwi (Wikipedia)

Related posts:

How do hummingbirds manage to hover in mid-air?

If there were a beauty prize for birds, the hummingbird would undoubtedly claim the first position. These birds, native to the North, South and especially Central America are Nature’s fire-flashing jewels. Their plumage is so brilliant that naturalists have given them the names of precious stones viz. Topaz hummingbird, Ruby-Throated hummingbird, Amethyst-Throated hummingbird, Fork-Tailed Emerald hummingbird etc. The brilliance of their feathers is produced by each barbule (a part of feather) which breaks up light like a prism.
Upside down hummingbird
Hummingbirds are the smallest of all birds and some of them are no larger than a medium-sized insect, weighing only about two to four grams. Yet this minute bird has the same parts of the body as any other bird: a heart, a stomach and a liver. Hummingbirds have special, vibrant way of flying, which produces a buzzing sound similar to that of bumblebees. Their wings beat so fast (50 to 70 times a second) that they become almost invisible to our eyes. Not only that, the hummingbird can also fly up, down, sideways, backwards and even upside down. (See photo above.)
The reason they can achieve such exceptional flight patterns is that they can rotate their wings in a circle, creating power on the upstroke as well as downstroke. They are the only birds which can hover in mid-air. While hovering, the wings act like an oscillating helicopter blade with a steep angle of attack, forcing the air downward with both up and down strokes. This unique method of flight allows them to draw from flowers the nectar, which they collect as avidly as any insect.

Additional reading:
Hummingbird (Wikipedia)

Related posts:

Why do some birds migrate thousands of miles?

Given the fact that on long and arduous journeys they have to expend must energy and encounter great dangers one wonders why some birds migrate thousands of miles. The reason is: birds must move about in search of food, and as soon as the supply is exhausted in one place, they must go to another where food is abundant.

Besides, in some regions like Europe and Eurasia seasonal climatic and ecological changes occur that may require the birds to move away if they are to survive. This is the most obvious and perhaps the most important advantage provided by migration. By flying hundreds and sometimes thousands of kilometers, birds can trade bitter cold and long nights of northern winters for the gentler warmth and sunlight of southern climates. Conversely, in the summer they can escape the scorching heat of the south and enjoy the long cool days of northlands. The evidence that migration achieves these benefits is found in the avian species of India. Out of 1,301 species, only 41 are endemic. The rest are migratory or seasonal visitors.

Additional reading:
Bird migration (Wikipedia)

Related posts:

Which birds have the most and the least feathers?

Birds vary in the number of feathers they have, according to species, size, age, sex, metabolism, health and season. Notwithstanding these factors, however, adult birds of given species taken at a given time of the year can still have different number of feathers. In general, whistling swan (photo below) has the highest number of feathers, with total 25,216 counted on one bird. Nearly 80% of these were on the head and long neck.
Whistling swan
On the other end of the extreme is ruby-throated hummingbird, with a feather count of only 940 on one specimen. Actually, the hummingbird possesses more feathers per gram of body weight than swan.

Additional reading:
Tundra swan (Wikipedia)

Related posts:

Is hummingbird the smallest bird? How small is it?

Bee Hummingbird
There are more than 300 species of hummingbird and they vary in size; though only a few are more than 15 retentiveness long. The smallest (shown here in actual size) is the bee hummingbird, which is a native of Cuba. An average adult male measures only 5 centimeters in total length, half of which is taken up by the bill and tail. This tiny flier weighs only 1.6 grams. It builds a thimble-size nest and its egg is less than 1 centimeter in length.

Additional reading:
Bee Hummingbird (Wikipedia)

Related post(s):

Why can’t we see in the dark like cats and owls?

In order to see, the eye must receive light; and darkness is the absence of light. Most of the objects we see around us are visible by reflected light — reflected sunlight or reflected artificial light. Since darkness is the absence of light, there is no light in the darkness to be reflected from chairs, tables, or people to our eyes, and therefore we can not see these objects.
Cats and owls can see in the dark because they have special kinds of eyes. It is true that cats and owls can see better in partial darkness than we can, because the pupils of their eyes can open wider and receive more light than our eyes can. You have probably noticed that it is difficult to see objects inside a house when you have just come in from the bright sunlight. After you have been in the house a little while, your eyes adapt themselves to the dimmer light, and you can see perfectly well. It is true, too, that our eyes become somewhat accustomed to the dark after a while. If you go out of the lighted house on a dark night, you find that after ten or fifteen minutes you can see much better than when you first left the house.

Additional reading:
Eye (Wikipedia)

Related posts: