The nest building in the birds is an innate behavior. Depending upon the condition of the young after the hatching from the egg the birds are classified into two types.
1. Precocial: the young of these birds are quite conscious and are able to leave their nests and survive out of the nest. Ex. Hen
2. Altricial: the young of these birds are very weak and they cannot survive out of the nest. Their skin is naked and the eyes are closed.the nests of these birdsa re generally build very high above the ground.
Nest building is a unique and beautiful character in the the birds.the nest building is the safest way to provide the protection to the eggsand the developing ypung ones. For safety the nests are build inaccessible, well armoured, camouflaged and in some cases they are build in colonies.
The nest building has a very close relationship with the copulation. The oesstrogen can induce the nest bilding in the birds. Primarily the nest building has benn suggested to arrive in the birds due to sex fidgeting, which is veery common before and after the mating. The nest is first the sex site.
The male and females of birds may equlally or unequally take part in the nest bilding. Von tyen and Berger classified the birds in 6 categories depending upon the part played by either of the sexes of the birds. According to them the birds are of following 6 types.
1. Both males and the females equally contribute to build the nest. Ex. Wood pecker
2. The materials are brought by the females and the males build the nest. Ex frigate birds
3. The building materials are brought by the males and the females build the nest.ex pigeion
4. The entire nest building is dome by the femae alone unaided by the male. Ex, humming birds
5. The entire nest building is done by the male unaided by the females. Ex beaver birds
6. The materials are brought by both the sexes but the nest building is done by the females. Ex. Crow
The way of nest buildimg varies greatly according to thte type of the materials used.
Nest building is instinctive character in birds, which is guided by the brain and may improve with experience. The young birds are found to buiod coarse nests as compared to the mature ones.the methods of building nests varies greatly. The most elabi\orate method is the tying of the grass to the branches of the trees.
Site of nest building:
The site for nest building selected to be very familiar. For ex.
1. The eagles living on high altitudes build their nests at bery high altitudes among the open cliff faces
2. Arboreal birds build their nests among the branches and leaves of the trees. Ex beaver bird
3. The ground birds build their nests on the ground. Ex hen
4. Water birds build their nests around water, ex heron
There are many birds which build their nests in a surrounding different from their original habitat. For ex the bee eater is not a ground bird but horizontall tunnels in the earth banks. Some ducks are found to build their nests on the ground.
Types of nests:
The types of nests vary greatly from species to species and show a great diversity.
a. Some ground bords may just scrap a little of the earth and lay their eggs in the depression and cover them with the soil or the vegetation.
b. Some ground birds build their early nests on the ground and the later ones on the small bushes.
c. Some birds nest in old holes and crevices which they line with soft materials.
d. Some birds build tunnels in the earth banks.
e. Som birds may build cup of grasses on the fork of the branches.
f. Most woodpeckers excavate a nest cavity in dead or living trees. They first bild a horizontal entrance with small edges few cm in length. After thet the vuild vertically downwardsand carefully remove all the shsvings. The woodpecker use the same tunnel to rear the next brood ommediately.
g. The tailor birds sew the hanging leaves of the branches together woth the fibers to form a cup like structure.
h. The weaver birds or the bayas make a basket like nest with lling thin entrance tube. The egg chamber is the wodest part. In bayas when the incomplete nest is like an upside down cup the female baya chose their mates, the male then completes the basket downwards. The bayas use their nests for only one generation and they build a new nest everytime the nedd to lay eggs.
i. The old nest of the bayas may be used by the other species of the birds like sparrow and white throated munnia.
j. The hornbills chose a deep hollow in the tree tthen the hen bird descend in the hollow. She builds up the wall from inside till the mouth to leave a small hole from where she can have the food brought by the males, the building materials consists of her own droplings
k. The abandoned nests of the wood peckers are used by many other species of the birds like blue birds.
l. The king penguins holds the single egg on the top of its feet and incublate likewise.
m. Special or colonial nestings:
i. About 13% of all the birds in the world and 93% of all the marine birds nest in the colonies.
ii. The habit may have developed probably fo the safety or due to limited nesting sites provided by islands and the cliffs.
iii. According to Von tyne and Berger these social nesting may involve:
1. Members of the same species
The nests of these types may be of two types:
I. Communal nesting: here one to four couples of the birds build a common nest in which all the females lay the eggs. Incubation of the eggs and the feeding of the young ones is done by all the adults. Ex hen
II. Cooperative nests: in this flocks of hundred or more pairs of birdsbuuild the nest and each pair has their own nestsing chambers.
2. Two or more species mixed together.
Mixed colonies my be of different types:
I. Large numbers of two or more species nest together in an area. Ex. Terns, herons, frigates.
II. One or more pairs of species living in the midst of large colony of other species.ex. skuas with penguins.
III. A number of small birds in close associatin with large birds. Ex,. Hose sparrow building their nests inside the osprey’s nests.
IV. Different genera of birds building their nests in close proximity. Ex myna, king crow.
Nest parasitism:
A) Obligate parasites: no nests are build by such species. They neither incubate their egg nor they care for their young ones. They lay their eggs in the nests of the other species called fosters or the hosts. Obligate parasitism is found in 5 different families.
1) Cuculidae: cuckoo family
2) Indicatoridae: honey guiders
3) Analidae: block headed duck of SA
4) Ploceidae: weaver bird family
5) Icteridae: troupial family.
B) Non obligate parasites: they are those species which incubate their eggs or care for their young ones but either frequently of rarely. They lay one or more eggs in the nest of other birds.
The parasites are of two types:
i) Nest parasites: they are those birds which unsurp the nests of other species and lay their eggs and incubate their eggs their only. Ex. Yellow tailed hornbill
ii) Egg parasite: they some times lay their eggs in the nest of the other species. Ex crow
Conclusion: the survival of any species of the animal depends upon itw reproductive success.
For the success the birds exihibit a high degree of care to their young ones. The chief form i
