Category Environtal Studies

          There are around 4000 species of mammal. Some spend their whole lives swimming in the ocean, while others never venture into the water. Most have fur or hair on their bodies at some time in their lives. Some walk on two legs and some on four. What all mammals have in common, however, is that they are warming blooded and breathe air. Mammal mothers feed their young on milk from their mammary glands. Mammals also have lungs, a heart with four chambers and well-developed brains.

Mammal, (class Mammalia), any member of the group of vertebrate animals in which the young are nourished with milk from special mammary glands of the mother. In addition to these characteristic milk glands, mammals are distinguished by several other unique features. Hair is a typical mammalian feature, although in many whales it has disappeared except in the fetal stage. The mammalian lower jaw is hinged directly to the skull, instead of through a separate bone (the quadrate) as in all other vertebrates. A chain of three tiny bones transmits sound waves across the middle ear. A muscular diaphragm separates the heart and the lungs from the abdominal cavity. Only the left aortic arch persists. (In birds the right aortic arch persists; in reptiles, amphibians, and fishes both arches are retained.) Mature red blood cells (erythrocytes) in all mammals lack a nucleus; all other vertebrates have nucleated red blood cells.

          Except for the monotremes (an egg-laying order of mammals comprising echidnas and the duck-billed platypus), all mammals are viviparous—they bear live young. In the placental mammals (which have a placenta to facilitate nutrient and waste exchange between the mother and the developing fetus), the young are carried within the mother’s womb, reaching a relatively advanced stage of development before birth. In the marsupials (e.g., kangaroos, opossums, and wallabies), the newborns are incompletely developed at birth and continue to develop outside the womb, attaching themselves to the female’s body in the area of her mammary glands. Some marsupials have a pouchlike structure or fold, the marsupial that shelters the suckling young.

          The class Mammalia is worldwide in distribution. It has been said that mammals have a wider distribution and are more adaptable than any other single class of animals, with the exception of certain less-complex forms such as arachnids and insects. This versatility in exploiting Earth is attributed in large part to the ability of mammals to regulate their body temperatures and internal environment both in excessive heat and aridity and in severe cold.

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          Birds show extraordinary variety and ingenuity in the nests they build. An untidy mound of sticks, simply dropped on top of one another, is all that a mute swan requires. House martins, on the other hand, literally build their homes. They skim over puddles and ponds, picking up little pieces of mud, which are built up into round-walled structures on the sides of buildings. Cuckoos, of course, are renowned for the fact that they use other birds’ nests in which to lay their eggs. They are able to mimic the size, shape and colour of the host-bird’s eggs to some extent, so that the additional egg is not immediately obvious.

          It should come as no surprise that hummingbirds, our smallest birds, make the smallest nests. Hummingbirds build on top of tree branches, using plants, soft materials and spider webs. Ruby-throats decorate theirs with flakes of lichen. Anna’s hummingbirds may lay eggs before a nest is completed, continuing to build the sidewalls during incubation. Most impressive is how these nests stretch. Hummingbirds usually lay a pair of eggs the size of black beans inside a nest about the diameter of a quarter. As the babies grow, the nest expands, keeping things tight and cozy.

          Orioles are the seamstresses of the bird world. Their iconic pendant nests dangle from outermost tree branches. The nests are impossible to miss among the barren winter branches and nearly as impossible to spot, surrounded by leaves, during the breeding season. Orioles use whatever material is available to stitch their bag nests: long grasses, twine, even horsehair. The nests are lined with soft materials such as plant fibers, feathers or animal wool. The Altamira oriole of extreme south Texas and Central America constructs one of the longest dangling nests, which can hang down more than 2 feet.

          It’s the exception rather than the rule, but a few species of birds get away with building hardly any nest at all! This doesn’t mean they are haphazard in their approach to laying eggs, though. Beach nesting birds (including black skimmers, many species of terns, and piping, Wilson’s and other plovers) lay eggs in shallow depressions scraped out in the sand. The remarkable thing about the eggs of these species is their cryptic camouflage coloration. Eggs are often speckles and match the sandy granules of the makeshift nests. Sometimes these birds will line the shallow scrape with shells or sand to add to the camouflage. As beaches get more developed, some of these beach nests have adapted to laying eggs on nearby rooftops.

          Huge colonies of murres and guillemots nest on rocky coastal cliffs. Most lack any structural nests, instead laying eggs that are extra pointy on one end. This shape helps the eggs pivot around the point instead of rolling over the edge. These ledge nesting sites are also more protected from predators. Cliff nesters aren’t found only on coasts. Lots of species, including condors, ravens and falcons, use cliffs, but they build stick nests in the crevices.

         Some waterbirds, including many ducks, nest in upland grasslands far from water. Others, such as loons, grebes, coots and gallinules, nest directly on top of the water. Eggs will sink, so the birds build floating platform nests out of cattails, reeds, other aquatic vegetation, or mud. They anchor the nests to emergent vegetation to conceal them and to keep them from drifting away.

          Holes in trees and cacti are nest cavities; underground nests are burrows. Burrowing owls in Florida will sometimes dig their own burrow, while the burrowing owls in the west usually rely on spots excavated by prairie dogs, badgers, tortoises or other diggers. Other underground nesters include bank swallows, belted kingfishers and Atlantic puffins.

          It is hard to say officially whoop lays the first eggs each year, but my pick for favorite nest is the great horned owls. Sure, many species can begin nesting in January in southern states, but it is still winter in the nothern states when great horned owls start incubating their eggs in nests made of sticks, often in trees. It’s essential that these owls get an early state on nesting, because the species is slow to hatch and fledge. It is remarkable to think of the owls sitting on eggs as snow piles up during frigid nights.

          The grand champion nest-builder is… the bald eagle! In 1963, an eagle’s nest near St. Petersburg, Florida, was declared the largest at nearly 10 feet wide, 20 feet deep and over 4,400 pounds. That nest was extreme; most bald eagle nests are 5 to 6 feet in diameter and 2 to 4 feet tall. Nest construction can take three months. Eagles typically use the same nest year after year, adding to it each season.

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          When they first hatch from the egg, baby birds are called nestlings. At this stage, many of them have no feathers. Blind and helpless, they are completely dependent on their parents for food and protection. As their feathers grow, they become fledglings, with open eyes and hearty appetites. When the fledglings have all their feathers and are strong enough, they are ready to learn to fly and begin to be independent.

          Fledging is the stage in a flying bird’s life between hatching or birth and becoming capable of flight. This term is most frequently applied to birds, but is also used for bats. For antiracial birds, those that spend more time in vulnerable condition in the nest, the nestling and fledging stage can be the same. For precocial birds, those that develop and leave the nest quickly, a short nestling stage precedes a longer fledging stage.

          All birds are considered to have fledged when the feathers and wing muscles are sufficiently developed for flight. A young bird that has recently fledged but is still dependent upon parental care and feeding is called a fledgling. People often want to help fledglings, as they appear vulnerable, but it is best to leave them alone. The USA National Phenology Network defines the phenophase (or life cycle stage) of fledged young for birds as “One or more young are seen recently departed from the nest. This includes young incapable of sustained flight and young which are still dependent on adults.”

          In many species, parents continue to care for their fledged young, either by leading them to food sources, or feeding them. Birds are vulnerable after they have left the nest, but before they can fly, though once fledged their chances of survival increase dramatically.

          One species, the ancient murrelet, fledges two days after hatching, running from its burrow to the ocean and its calling parents. Once it reaches the ocean, its parents care for it for several weeks. Other species, such as guillemots and terns, leave the nesting site while they are still unable to fly. The fledging behavior of the guillemot is spectacular; the adult leads the chick to the edge of the cliff, where the colony is located, and the chick will then launch itself off, attempting to fly as far as possible, before crash landing on the ocean.

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          Birds are specially adapted for flight, whether skimming short distances between branches or flying for weeks at a time above the oceans. The shape of their wings gives a clue to the kinds of flight they make. Birds’ bodies need to be light enough for flight. The large surface area of their wings pushes air downwards as they flap to lift the bird. At the same time, birds need immensely powerful chest muscles to move their wings. Feathers are the ideal covering —they are light but strong and flexible. In flight, they can lie flat against the bird’s body to reduce wind resistance.

          Flying is possible for birds because of their strength, speed, weight and the way their bodies are created with parts such as wings. These are adaptations, or special and different features, that are designed to help birds fly. There are many different birds with different ways of flying.

          When you look outside, you probably see lots of different birds flying and soaring from place to place. Their wings flap and help them to fly high in the air. Then, their wings spread out in a strong, straight line to continue soaring.

          Birds’ bodies are usually lighter in weight than other animals. This is a necessary adaptation that helps them fly. Gravity is an invisible force that pulls heavier objects down toward Earth more than lighter objects. Therefore, the light weight of birds makes it easier for them to move up into the air since less gravity is working against them.

          Birds’ weight is also focused toward the center of their bodies. They don’t have too much weight on the sides, front and back of their bodies. This gives them the balance they need to fly.

          Your bones are thick and heavy. However, birds’ bones are hollow, or empty, on the inside, which causes less weight. They also have very light feathers. Mother birds lay eggs instead of carrying babies in their bodies, which helps them to stay lighter in weight as well. Additionally, birds have beaks instead of heavy teeth and noses; this also helps to reduce their weight.

          Have you ever walked around with a heavy, full stomach from eating too much? This causes you to feel heavier. Birds, on the other hand, eat lightweight foods such as berries, seeds and light meats that digest very quickly. Their bodies also get rid of wastes quickly so that they’re not too weighed down to fly.

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          Some male and female birds of the same species have very different plumage, with the male usually being more brightly coloured to attract females. Other species show little or no difference between the sexes. As well as having different plumage, birds may make displays to each other during the breeding season. Some dance in elaborate curving patterns, spread their feathers and strut, or sing. Male birds may fight to defend their territories during nesting.

          Once a budgie is a few weeks old, you will be able to tell the sex of the bird by looking at its cere (the nose and nostril area). In normal circumstances, a hen’s is brown, and a cock’s is blue. The hen’s cere becomes enlarged and scaly during the breeding season, and the male’s becomes a darker shade of blue. Simple!

          But there are a few complications. Hens sometimes have a light blue cere, when their breeding hormone levels are low. It will also be this colour, or white with just a hint of blue, if the bird is ill. In the wild the female’s cere is light blue, turning brown during the nesting season. In young hens, the cere is a light blue with white around the nostrils.

          Cock birds, although nearly always sporting a blue cere, may have a brown or brownish-pink one if his breeding hormones dip, or if he is ill. An ill male may develop a yellow-greenish tinge around the nostrils too. In immature cock budgies the cere is a blueish pink or light purple.

          Some budgie types are harder to sex. Albino, Lutino and Mottled birds, for example, have off-white, light pink or bluish pink ceres, and males of some of the pied varieties have light pink, blueish pink or white ones. With hundreds of variations on the basic types mentioned in the Budgie types section , there is always a chance that your bird will have an ‘ambiguous’ cere colour. In 90% of cases, however, the brown-or-blue rule applies.

          In spite of these complications, cere colour is still the easiest way of sexing budgies. There are a few gender-related differences in voice and behaviour, too; but these are not as consistently ‘male’ and ‘female’ as cere colour. If you inherit an adult bird of unknown sex and with an ambiguous cere, watch out for bonding behaviour – any excessive head-bobbing is likely to be a male and any excessive squawking, rather than chirruping and singing, is probably female.

          Many snakes throw themselves along the ground in waves that pass from head to tail. They have hundreds of pairs of ribs and strong muscles to enable them to do this, while their scales grip the ground. North American sidewinders, however, move as their name suggests, by throwing their coils sideways along the ground. Snakes have four ways of moving around.  Since they don’t have legs they use their muscles and their scales to do the “walking”.

Serpentine method:  This motion is what most people think of when they think of snakes.  Snakes will push off of any bump or other surface, rocks, trees, etc., to get going.  They move in a wavy motion.  They would not be able to move over slick surfaces like glass at all.  This movement is also known as lateral undulation.

Concertina method:  This is a more difficult way for the snake to move but is effective in tight spaces.  The snake braces the back portion of their body while pushing and extending the front portion.  Then the snake drops the front portion of their body and straightens a pulls the back portion along.  It is almost like they through themselves forward.

Sidewinding: This is a difficult motion to describe but it is often used by snakes to move on loose or slippery surfaces like sand or mud.  The snake appears to throw its head forward and the rest of its body follows while the head is thrown forward again.  (See picture.) 

Rectilinear Method:  This is a slow, creeping, straight movement.  The snake uses some of the wide scales on its belly to grip the ground while pushing forward with the others.

Picture Credit : Google