Category Biology

Which are the birds of prey?

The birds which feed on other animals are called the birds of prey. They catch and feed on animals that are usually smaller than themselves. They may catch their prey anywhere on the ground, in air or in water. Not all birds bother to choose their prey. Some even feed on the flesh of dead animals. Do you know which the birds of prey are?

Among the common birds of prey are: buzzards, eagles, falcons, harriers, hawks, kestrels, vultures and wood peckers. Owls also catch smaller animals and feed on them but they are put in a different category. Most of the birds of prey are brown-coloured. They are found on all the continents except Antarctica. They kill their prey with their strong sharp talons, and pluck and tear the flesh with their narrow, hooked beaks. These birds normally swallow huge chunks of food and regurgitate the pellets of indigestible matter.

The birds of prey attack in two ways. Kestrel hunts by hovering over open ground, and then plunging down on its prey before it can escape. Falcon stoops or dives its head first at its prey and catches it in its talons. Eagles are powerful and soaring birds.

Some eagles hide in a tree and wait for their prey to wander into a clearing. Carrion eaters soar on outstretched wings at considerable heights for hours together and peering down for animals already dead or one about to die. In contrast to it the small birds of prey like the sparrow hawk dash at high speed through trees to spring surprise on a small creature. The birds of prey also kill with their feet. Although some use the beak for the purpose, yet the sharp, curved talons of the feet are the main killing weapons. The rear and inner talons are usually larger than the middle or outer one. These help the bird to exert a strong pincer grip on the prey.

The birds of prey hunt a variety of animals such as rabbits, hares, grouses, fishes and many other birds. 

How do the fishes smell things?

          It may be surprising to note that fishes can smell things just like other creatures. And like other animals they have noses for this purpose.

          There are two pairs of nostrils in a fish. Each nostril has two openings which are called pits. One opening is in the front, and the other directly behind it. The two are separated by a small flap. However, the location of the nostrils may vary from species to species. 

          When a fish is under water, a current of water enters from the front pit and comes out through the rear one. As the water flows inside, it stimulates the sense cells which enable the fish to catch the smell. Many fishes have a keen sense of smell. They can detect even the faintest smells.

          In fact, the sense of smell may be important to a fish in helping it find its way home. Some fish could distinguish between the water of two creeks through smell. But if their noses are plugged, they get lost. To prove this fact some researchers had performed certain experiments. In one experiment a large number of salmon fish were taken out of their home stream. Half of them had their noses plugged; the other half did not. The fishes with plugged noses got lost and the rest half could find their way back home again. Anglers use peculiar scented fish-food to attract them.

          Apart from the sense of smell the fishes have other sensory perceptions also such as the sense of touch, taste, hearing and seeing. 

How do the plant seeds get dispersed?

               One of the major differences between animals and plants is that animals can move whereas plants cannot. They remain static at one place even though they grow vertically horizontally depending on their growth pattern. But how do these plants spread their seeds to grow at different places? It is interesting to note that nature helps them in this activity and this process is termed as dispersion of seeds. 

               There are mainly four agents responsible for the dispersion of seeds, viz. air, water, birds and animals, and the plants themselves.

               When the dispersion is carried out by the plants themselves the process is called dehiscence. In dehiscence (or dispersion by explosion), a seed-containing structure such as a pod, bursts shooting the seeds into the air. These seeds land up at a distance depending upon the weight of the seed and the force with which they are thrown. Some of the plants that disperse their seeds in this manner include plants of the pea, mustard, and balsam family.

               Air is also an effective dispersing agent for the seeds. Lightweight seeds fly from one place to another along with the wind. Some grass seeds have been detected at heights of more than a thousand metres. Lightweight orchid seeds are carried away by air to great distances from their parent plants. Seeds of some plants, such as dandelion and cattail, have puffy hair that helps them float through the air and land up elsewhere. The seeds of maple, ash and box elder have wing like structures to move like small helicopters in the wind and thus get dispersed. 

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How did the first bird evolve?

            It seems strange but true that the first species of birds originally evolved from reptiles about 140 million years ago. The evolution of birds followed the same course as that of any other species — in a slow and gradual process. They originated from reptiles to develop to its present form passing through different stages. The first bird was called archaeopteryx which was of the size of a crow. The existence of this bird is supported by fossil records. But what are the distinct features that classified it as a bird? 

            Though in appearance it was quite like a reptile and had teeth like a lizard and a long bony tail, yet in many other ways it had different characteristics from that of a reptile. Its head was balanced upon a long, thin and probably flexible neck. It had feathers instead of scales. These distinct features made it a bird and not a reptile and that is why archaeopteryx came to be known as the first bird on earth.

            It was different from the modern day birds in many other important ways. It could not fly properly for any considerable distance as it was not able to flap its wings very hard and probably used them for gliding as well as sailing through the air. It had a small poorly developed breast-bone. It had claws on its wings and was a warm-blooded bird. 

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Why are stripes a boon to the zebras?

            Zebra is a member of the horse family. But as compared to other members of this family it stands apart because of its striped coat. Each animal has its own special pattern of stripes.

            Today we have three species of zebra that have survived over the ages. The most commonly found is Equus quagga – known either as the common zebra or as the plains zebra. It inhabits eastern and southern Africa – south of Ethiopia. The other species is Equus grevy which is found in Somalia.

            It is the largest of all zebra species and has numerous thin stripes and very large ears. The third surviving zebra species is called the mountain zebra or Equus zebra. It has numerous narrow stripes and is found in the mountains of Namibia (South-West Africa) and Angola. At one time, there existed a species called quagga which had stripes only on its head but is now extinct.

            Since all the species have parallel black or brown stripes on white background, it is not off the mark to assume that the stripes must in some way be helpful for these grazing animals. Although a number of theories have been advanced to explain this phenomenon, none gives a very convincing explanation. According to one theory, the stripes create a ‘dazzle pattern’ and thus help the zebra to hide from its enemies by blending with the ‘shadow-sunlight’ patterns where it lives. Since lion is its main enemy, this physical characteristic helps to protect it. Some other researchers have suggested that the stripes are disruptive, and create confusion in singling out an individual zebra when they are bunched together due to the overlapping of their outlines. This helps in protecting them as a lion finds it difficult to single out a potential victim.

            Zebras are grazing animals; some roam around open grassy plains whereas others live in rough mountains. They usually live in small bands. They are noted fighter, and it is difficult to tame or train them.

            The gestation period of different zebras varies from 300 to 390 days. Usually one young is born at a time although twins are also a possibility. 

Which fish keeps its eggs in its mouth?

          There is a peculiar species of sea-fish that keeps its eggs in its mouth. It is the catfish found in the Atlantic Ocean off the east coast of America. The most surprising fact about it is that instead of the female, the male takes on the responsibility of looking after the future family. After the eggs are laid and fertilized, the male quickly puts them into his mouth. They completely fill its mouth and prevent it from eating. It carries them around for a month. During this period it is unable to take its food, and lives off the food reserves built up before the spawning. Moreover, his motherly role does not end even after the hatching of eggs. For two more weeks, the youngsters swim into his mouth to hide when any danger threatens them. 

               There are seven kinds of fishes which are called catfish and are found in eastern and central North America. Some species, like the flathead catfish and blue catfish, can even weigh more than 45 kg. The catfishes live near the bottom of slow-moving rivers and lakes. They have four pairs of barbels around their mouth. These barbels look like the whiskers of a cat and hence they are called catfishes. The barbels are quite sensitive and help the catfish feel its way around and find food.

          The electric catfish is one variety which uses electrical discharges to stun and capture other fishes. Its electric organs lie just under the skin and cover its body and part of the tail. A large catfish may even produce a current of 350 volts.

          Another kind of catfish called Wels catfish grows to huge sizes in muddy-bottomed lakes in central Europe. Some specimens grow up to 9 feet in length and some others compete with Arapaima which is claimed to be the largest fresh water fish in the world.