Feb 2017
They are the wonders of Nature and so easily spotted around us. Here is all that we need to know about our feathery friends & how we can make their lives a lot more easier and help raise their dwindling numbers too
Archana Misra
Birds are undoubtedly Mother Nature’s most beautiful and joyful creations. Their chirping can soothe even the most irritated of brows and their sight can lift up the lowest of spirits. Unlike most fauna of the wild, almost all bird species can easily get used to human beings and co-habit without causing any threats, provided humans also do not harm them intentionally or unintentionally. This is of high importance in today’s times when the natural habitats of birds are under threat from rapid urbanization as well as use of forest land for cultivation purposes. If we wish to spot a few birds, why should we have to wait for the migratory ones to arrive or plan a vacation in some bird sanctuary? Why can we not improve our surroundings to an extent where at least some birds – like sparrow, mynah, bulbul, weaver bird or even crows and owls—can find a place to live, nest and breed? Why should sighting a house sparrow become a rare feat? The answer is we are not really aware of how we are destroying the survival chances of feathery friends around us, or we even lack knowledge of how we can create conducive environment for them. Thus it is of high importance that we understand the breeding and nesting habits/ requirements of various birds.
Most species breed annually and many small birds raise more than one brood in a year. The timing is related to food supplies since the maximum amount of food needs to be available for the young to fledge successfully, this means that the climate is the main determinant. Since climate varies through the region, so do breeding seasons, although a few species breed throughout the year. Most birds breed immediately prior to the main monsoon, to take advantage to the increase in invertebrates that are the main source of food for the young. Even seedeaters like sparrows and weavers, feed their young on insects. Some reed-bed, sandbank and marshland and ground nesting species also breed before the onset of the monsoon, to avoid getting flooded out. Most large water birds such as cormorants, egrets, pelicans and herons breed during and at the end of the monsoon, as water means food supply to these fish/frog eating birds. Many raptors breed in the winter months, because of the abundance of migratory birds. Birds of the high altitude breed only in the brief summer months.
Signs that Birds are going to Breed
There is such a thing as breeding condition, which means that there are physical changes in the bird's body at the time when the bird is ready to breed. It should be borne in mind that a bird’s plumage can vary according to the time of the year and the sex of the individual. So you need to establish whether you are looking at a bird in breeding plumage or a non-breeding bird in winter plumage. To pinpoint when the bird mating season occurs, watch for: warming temperatures and blooming flowers that show the change of seasons. Territorial birds become more aggressive toward intruders, particularly males; the appearance of bright breeding plumage with fresh, clear markings; increased in bird song, which can help define territories and attract mates; courtship behavior, including elaborate display flights and other bondings; . decrease of large winter flocks or mixed foraging flocks as birds pair off with mates; and collection of nesting materials and the beginning of nest building activities.An interesting behavior is displayed in weaverbird in which the male bird changes colour during the breeding period and starts buildings nests. Then the female visits each nest and selects the best one. Here the courtship takes place and the eggs are layed.
Choosing a Mate
While territories are being claimed, birds try to attract mates. In most species, females choose males based on an assessment of their overall quality and vigor. Males advertise their suitability as a mate by exhibiting bright breeding plumage during courtship displays, by bringing food to females, by demonstrating their nest-building abilities, and by singing, drumming, or calling. Social pair bonds tie males and females of most species together throughout the breeding season, but promiscuity is not uncommon. Even birds that presumably “mate for life,” such as Bluebirds (North America), may not always be faithful. It is possible for nestlings in a single nest to be fathered by different males! Males of some species, such as pheasants (peococks), red-winged blackbird and house wren, can have more than one mate at a time (a mating system called polygyny). Much less commonly, females of some species, such as Wilson’s Phalaropes, may have more than one mate as well (polyandry).
Do birds Mate for Life
If mating for life means one partner in a lifetime to you, then there are very few birds that fit into this category as reproduction is a primary goal of a species. Those birds that do fit this category are the ones that die in their first pair bond, as the surviving bird will attempt to find a new mate, like the sarus (crane). Rather, most pair bonds are formed for a single season. Those birds that pair for a season are referred to as monogamous species. Monogamy is pairing of a male bird with a female bird through a single nesting cycle. Other pair bonds may be formed and last over several seasons. Doves, robins, sparrows, swans, geese, eagles, and some owls are on this list. Why birds mate for life is not as romantic as one may think. When you consider the time needed to migrate, establish territories, incubation and raising young, you will realize that the extra time and energy needed for attracting a mate would minimize reproductive time. The Bald Eagle for example, spends just over a month incubating the eggs and 2 1/2 to 3 months raising their young in the nest. Establishing lifelong pair bonds works to their advantage.
Nesting Behaviour of Birds
Nests provide a safe place for eggs and young birds to develop. Bird nests are extremely diverse, although each species typically has a characteristic nest style. Some birds do not make nests at all and instead lay their eggs in a simple scrape in the ground. Other birds construct nests from natural materials, such as grass, leaves, mud, lichen, and fur, or from man-made materials like paper, plastic, and yarn. Nests can be found almost anywhere – on the ground, in trees, in burrows, on the sides of cliffs, in and on man-made structures, etc. Usually, the female builds the nest, and the male helps her. In some species, though, the male does nothing, and in others, the male builds the nest and the female does nothing. Many birds "glue" their nests together with materials like spider webs, silk, mud, and even their own saliva (spit). Most nest builders like to put soft things inside their nest. However, nests can become home to many other organisms including parasites and pathogens. The excreta of the fledglings also pose a problem. In most passerines, the adults actively dispose the fecal sacs of young at a distance or consume them. This is believed to help prevent ground predators from detecting nests. Young birds of prey however usually void their excreta beyond the rims of their nests. Blowflies of the genus Protocalliphora have specialized to become obligate nest parasites with the maggots feeding on the blood of nestlings. Some birds like cliff swallows, sparrows, baya and weaver bird have been known to choose aromatic green plant material (herbs) for constructing nests that may have insecticidal properties, while others like common waxbills may use materials such as carnivore scat to repel small predators. The great-crested flycatcher puts snake’s skin to ward off enemies
Types of nests
Cup nest: The cup nest is probably the most common bird nest. Its name tells you that a cup nest is shaped like a cup or bowl. Many songbirds built cup nests. These nests can be built in the branches of a tree, like in the crack where one branch joins another: however, some can simply stick the nest right onto the branch of a tree. They use lots of materials that act like sticky glue – mud, rotten wood, dung, spider webs, and caterpillar silk. They sometimes even use their own saliva mixed with food to keep the nest firmly stuck on the branch. Cup nesters use all kinds of materials to build a nest: twigs (tiny branches), grass, leaves, moss; and they use all sorts of materials to keep it from falling apart. Most cup nesters use rough, scratchy material for the outside (this gives protection and camouflages the rest), and put soft, cozy material like moss, fur, feathers, and cotton on the inside. Many cup nesters enjoy nesting very close to the ground in low bushes – sometimes they will even nest in potted plants on a porch. Some of them actually just build their nests on the ground. Sparrows, cardinals, and many other song birds (called passerines), like to nest near the ground, far away from owls, hawks, and Blue Jays that may eat their babies. There are several types of cup nests. A suspended cup nest is attached to the branch at the top and sides but then drops like a bag down below. It really looks more like a vase than a cup. The bird is almost hidden when she warms her eggs. The mother bird can sit down on the branch above the nest and bend down to feed her baby birds. Orioles are very famous for building amazingly long bags that hang far below the branch. The smallest cup nests are made by hummingbirds. They can be as tiny as a thimble, like the Bee Hummingbird's nest. That tiny nest holds eggs that are as tiny as peas. The largest cup nest is probably the stork. An old nest can be nine feet deep and six feet wide. The stork's nest is so big that smaller birds actually make nests in its cracks, holes, and branches.
Adherent nests: Adherent nests adhere (stick) to buildings, trees, cliffs, or other vertical structures. Swallows can build an almost perfectly round nest out of mud. Some species make cup-shaped nests, while others make jug-like nests with little holes in the sides. They put little balls of mud in their mouth and mix it with their saliva, making a special clay. As it dries, it becomes hard. Bird saliva is very good for making glue: in fact, some species of swiftlets make their whole nest out of simply saliva. The male regurgitates (throws up) a long, thin strand of saliva from glands under its tongue. This saliva is used to be made into a half-cup nest which sticks to a cave wall (swiftlets like to build their nests in caves and grottos) and dries quickly.
Pendant: Pendant nests are elongated sac woven of pliable materials such as grasses and plant fibers and suspended from a branch. There are several species that weave pendant nests. Popular species that build pendant include caciques, orioles, oropendolas, sunbirds and weavers.
Platform nests: Platform nests are built mostly by raptors (birds that eat prey, like eagles and hawks). They are usually huge and very, very high up - on the sides of cliffs, maybe, or high up in a big tree. It takes a few months making these nests, adding branch by branch. They often return to the same nest year after year and continue to build it. It is because of this that platform nests get so big: a Bald Eagle's nest, for example, can weigh as much as a ton (about the same weight as a small car). It is so heavy it can sometimes hurt the tree it is built in. A few water birds (like grebes and loons) build platform nests right on the water, where they can float. The nests do not move, though, because they are anchored to plants that are attached to the bottom of the body of water. These birds build nests on water because they do not walk well on land, so they find a shallow (not deep) part of the water to build their nests. Then, they do not walk to their nests - they swim to it. When the babies are ready, they simply jump into the water and begin their aquatic (water) life.
Earth-hole/ burrow nests: Earth-hole nests are nests that are inside the earth. They are burrows (tunnels) on the ground or in the sides of cliffs. They like using abandoned rabbit holes, too. The Burrowing Owl only uses already dug holes for its nest. Puffins, for instance, dig a tunnel that is usually two to three feet long. At the end they make a nest of feathers and grass and lay their eggs. They are able to do this because of their sharp bill and claws. A puffin can work for hours to make its tunnel. Kingfishers, too, digs or burrows its hole. It can burrow up to six feet into the side of a cliff and lay its eggs there.
Ground and mound nests: Many birds nest right on the ground. After carving out a little hole, ground and mound nesters line the nest with grass or other materials. Geese even pick feathers from their breasts and make a nice downy bed for their eggs. Most ducks, geese, pheasants, quail, francolins, and partridges nest on the ground. Penguins nest on the ground, too, pushing rocks around the nest to keep it from washing away with flood waters (most penguins live and nest in Antarctic where there is permanent snow, no flooding). Usually, males make ground nests. The Trumpeter Swan makes a big mound nest, and flamingos make mounds, too. Flamingos make their mounds completely out of mud. They can be up to 18 inches high and 12 to 20 inches in width.
Cavity nests: Like burrows, cavities in trees provide excellent protection. Birds who build cavity nests—like woodpeckers, parrots, hoopoes, and many species of owls—make use of holes in trees or hollow out their own. These cavities allow birds to efficiently heat their eggs and can provide a sturdy shelter in poor weather condition. One interesting behavior is displayed by hornbill. The male seals the female in a cavity with only enough space for it to thrust out its head. Then for the entire period that the female lays eggs, incubates them and the little chicks come out, the male takes care of its female, bringing it food and water from time to time.
Scrape nests: These nests are barely a nest at all – just a small depression in the ground or a pile of dead leaves to lay eggs on. These scrape-nesting birds usually have eggs that match the color of dead leaves or rocks. This is needed because these eggs are in danger of being eaten by animals like rats, raccoons, snakes, and others that eat eggs. Many scrape nesters actually tries to distract creatures that might be dangerous by pretending they have a broken wing and trying to distract it. This makes a predator chase the mother bird, and leave the eggs.
Sphere: The Sphere nest is a roundish structure; it is completely enclosed, except for a small opening which allows access. One notable maker of sphere nest is the thick-billed weaver.
EGG LAYING
The total number of eggs that a female can lay in one nesting attempt varies widely depending on the species. For example, many tropical birds lay clutches of only 2 or 3 eggs. Waterfowl, such as wood ducks, can lay up to 15 eggs in one nesting attempt. Clutch size can also vary widely among individuals of the same species depending on food and calcium availability, latitude, age of the female, weather, and time of year. The size, shape, color, and texture of bird eggs are also extremely variable both within and among species.
INCUBATION
Birds incubate their eggs to keep them at the proper temperature to ensure normal development. Female songbirds usually begin incubation after they have finished laying all of their eggs so that they will hatch at approximately the same time. Other birds, such as herons, cranes, cormorants, and raptors begin incubation as soon as the first egg is laid and therefore their eggs may hatch on different days. Incubation time varies depending on the species, but typically the larger the bird, the longer the incubation period.
HATCHING
Songbirds and most seabirds have altricial young, meaning that the newly hatched birds are blind, featherless, and helpless. Immediately after hatching, altricial birds can do little more than open their mouths to beg for food. They remain in the nest where the parents can feed and protect them while they continue to develop. For the first week of life, most altricial birds cannot control their own body temperature and must be constantly brooded (kept warm) by their parents. By the end of the first week, their eyes are usually open and their feathers are beginning to emerge. During this period, nestlings can experience remarkable growth by doubling their body weight several times! Precocial species, such as ducks, pheasants and many shorebirds, are born fully feathered, mobile, and with eyes open. Incubation periods are longer for precocial birds than altricial birds, allowing for increased embryonic development in the egg, and therefore they have relatively advanced motor and sensory functions at hatching.
FEEDING THE YOUNG
To keep up with the food demands of nestlings, their parents continuously forage for food. This is an extremely dangerous time for both the adult and young birds because the increased activity and begging cries of nestlings can attract predators. After 2 or 3 weeks, most songbirds are usually ready to leave the nest. Other birds, such as raptors, may stay in the nest for as long as 8 to 10 weeks. In contrast, precocial birds spend hardly any time in the nest and are often seen wandering in search of food alongside their parents only hours after hatching.
LEAVING THE NEST
Most birds nest only once a year, but some species, like the American Robin, can breed up to 4 or 5 during a single breeding season. After leaving the nest (fledging) young birds typically remain close to their parents for a short period. During this time, young birds must learn to survive on their own and are very vulnerable to predators and starvation. The first year is the toughest; in nearly all bird species, more than half of the first year birds perish. For birds that do make it to adulthood however, the odds of surviving another year improve greatly.
Main Threats to Nesting & Survival
Loss of habitat: The most critical threat facing threatened birds is the destruction and fragmentation of habitat. The loss of forests, plains and other natural systems into agriculture, mines, and urban developments, the draining of swamps and other wetlands, and logging reduce potential habitat for many species. In addition the remaining patches of habitat are often too small or fragmented by the construction of roads or other such barriers that cause populations in these fragmented islands to become vulnerable to localised extinction.
Pollution: Birds face a number of other threats. Pollution has led to serious declines in some species. The pesticide DDT was responsible for thinning egg shells in nesting birds, particularly seabirds and birds of prey that are high on the food chain. Seabirds are also vulnerable to oil spills, which destroy the plumage's waterproofing, causing the birds to drown or die of hypothermia. Light pollution can also have a damaging effect on some species, particularly nocturnal seabirds such as petrels. Seabirds face another threat in the form of bycatch, where birds in the water become tangled in fishing nets or hooked on lines set out by long-line fisheries. As many as 100,000 albatrosses are hooked and drown each year on tuna lines set out by long-line fisheries.
Hunting & Smuggling: Humans have exploited birds for a very long time, and sometimes this exploitation has resulted in extinction. Hunting pressure can be for food, sport, feathers, or even come from scientists collecting museum specimens. Collection of Great Auk for museums pushed the already rare species to extinction.
Man caused deaths: Birds are also threatened by high rise buildings, power lines and wind farms. The largest source of human-related bird death is due to glass windows. The next largest sources of human-caused death are hunting, house cats, cars and trucks, electric power lines, and pesticides. Birds are also killed in large quantities by flying into communication tower guidelines, usually after being attracted by tower lights. This phenomenon is called ‘towerkill’. The presence of towers may seriously impact endangered species living in the vicinity. Birds can also be killed by heat while flying above solar power plants: in 2015, biologists working for the state of California estimated that 3,500 birds died a single solar plant in the span of a year, "many of them burned alive while flying through a part of the solar installment where air temperatures can reach 1,000 degrees Fahrenheit.”
Nesting Pattern of Some Common Birds
Sparrows and pigeons: The sparrow and pigeon make their nests with grass, leaves, feathers, etc. They make them on trees or in houses, at any safe place. Sparrows use the nest nearly year around. In spring and summer the birds use the nest for raising youngones, up to four broods a season will be raised. In fall and winter it is used for resting in the day and roosting at night. The nest can be located in any available place in buildings, trees, and birdhouses near human habitation.
Bulbul: A bulbul’s nest can be found in hedges and bushes. The nest is cup-shaped. This prevents eggs or baby birds from falling out.
Partridge: The nest is made of dried grass and leaves. The bird uses its beak to make a nest which is hollow inside. The nest is made on the ground in the bushes or in tall grass to keep it safe from enemies.
Weaver bird: The weaver bird uses dry twigs, grass, fine pieces of straw to make a very big and strong nest by pulling the grass in and out. The nest hangs from the branch of a tree. The bird enters and comes out through a tunnel-like opening at the end of the nest.
Tailor bird: The tailor bird makes their nests with long leaves. They stitch two large leaves together with bit of thread, straw and dry twigs. The nest is lined with material like cotton, wool, grass and hair to keep the nest cosy.
Woodpecker: The woodpecker makes holes in the trunks with their chisel-like beaks to make their nests. They use chips of wood to make their nests warm and cosy.
Owl: The owl makes their nests in the hollows of trees or on walls. The nest is lined within, to keep it soft. They put feathers and grass in their nests to keep them warm.
Here are some birds that do not build nests:
The koel is a clever bird. It does not build its own nest. It lays its eggs in the nest of a crow when the crow is away. The crow takes care of these eggs thinking that they are its own eggs. It even feeds the baby birds on hatching.
Cuckoos do not build their own nests. They lay their eggs in nests of other birds.
The penguin too, does not build a nest. It either lays its egg on a platform of stones on the ground or the. male penguin holds the egg between its feet and lower belly and incubates.
(This article has been compiled with the expert guidance of Dr Asad R Rahmani, Senior Scientific Adviser, Bombay Natural History Society (BNHS), and inputs from Renu Singh, conservator of forest, endangered species)
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