Post mating the building of nest is the next important process in a birds Lifecycle. In some cases like Baya weaver and in Barbets etc this is done before mating and is a criteria for the female to agree to pair. The nests of birds come in different sizes and shapes. Some are built fresh, Some are reused by the same bird, some by different bird, Some are excavated and so on. In this article we will visit the common shapes and types of nests. There may be a few variations in each type dependent on the species needs.
Open Cup: This is a CUP shaped nest where the sides are equally to or greater than the width at the mouth of nest. They are open at the mouth with no roof. The structure is made up of coarse exterior and a soft interior . The materials used are Grass, veins, leafs petioles that are densely woven together to form a structure with thick sides. It is hidden using dead or green leaves or Moss bound using spider web or hair. They are constructed over an open branch to look like a knot or in a fork of a tree. There are variations to this basic structure in terms of materials used, size, placement etc. but the basics remain same. Birds like Flycatchers, Fantails, Pipits, Larks, Shrikes etc. build this type of nest
Open Bowl (Saucer) : Similar to the OPEN CUP but the width is greater than the height of the sides. So it has a Saucer shape . It is loosely woven with number of gaps for ventilation and is generally untidy work compared to an OPEN CUP. These nests are also built with same materials like Grass and fine pliable woody material. They are not camouflaged and are found open on branches in any position, in bushes and in cavities of trees. In some cases like Drongo’s they are hung like a hammock between two small branches. These nests are open to predation and harmed by strong wind. But nature has adapted the birds in such a manner that the eggs laid in this types of nest are pigmented and well camouflaged. Once the chicks hatch they grow faster and spend relatively less time in the nest compared to the ones in OPEN CUP nests
Platform: It is a no frill nest built by birds on mounds on ground or on tree. The building material use are Twigs and in some cases of aquatic birds some creepers. The twigs are laid one upon another in an interlocking position in a Lattice like fashion to form a basic sturdy platform. They are reusable nests and birds like raptors and herons keep adding twigs on the nest after laying eggs to increase the size and make it sturdier. No attempt is made to camouflage the nest as it is built in community nesting area where hundreds of birds of similar size have built the nest. The numbers offer protection from predators .
Woven Balls: These nests are built exclusively from dried grass and veins. The material is woven into beautiful ,intricate structures that have more height than width. The entrance to the nest is usually at Bottom or at side of the top of the nest. The nest is built over hanging a water body on a thorny shrub like Baya Weavers or hanging in midst of large tree canopy at a great height like in Broadbills. This is to prevent the predators from reaching the nest. This structure also provides protection from rain and wind. It is also well ventilated at the same time providing optimal insulation to the eggs.
NO Nest : As the name suggests there are birds that lay eggs on the ground or on cliff tops and do not build any nest for insulating or protecting them. These eggs are usually pigmented , coloured and patterned to match the ground where they are laid . this offers camouflage to the eggs. The chicks here too grow faster compared to chiscks that are laid on the nests. Example of birds that have no nests are Nightjar, Ground dwellers like Thicknee, Falcons etc.
Nest Scrape: Similar to no nest but there is a small depression in the ground to hold the egg. this depression is made by scrapping the sand, stones debris away. The scraping is done by using both feet. If the bird moves in circle while scraping it make a circular depression and if it remains straight and scrapes in one direction then it makes an elongated depression. The interiors can be padded with leaves and soft materials to protect egg and provide camouflage . In some cases the dropping of birds and small stones are kept around the depression to protect the eggs. The eggs here too are well camouflaged with patterns and colours. Example of birds that do this kind of nesting : ground dwellers like fowls, Lapwing, Thicknee
Holes : As the name suggests these are holes or cavities that are used by birds for nesting. There are three categories here basis the origin of hole
- Natural Hole : Birds that cannot excavate a hole or cannot find an old existing excavation use the holes that occur naturally without their effort. These holes can be formed by broken tree branches, rotten barks, Gaps in Rocks and Cliffs, hollow stumps etc. They usually have a chamber below the entrance to house the egg and prevent it from falling out. They are some times modified a bit to accommodate the birds need . The entrance is kept as small as possible so that only the bird can enter and making it difficult for large predators. Examples of birds that use this kind of nests are Owls, Barbets, Hornbills etc. Hornbills go to an extreme step when they will plaster the entry of the nest with the female hornbill and eggs inside the nest. There will be a very small window through which the male will keep giving food for the female and the chicks. Only once the chicks are ready will the hornbills break open the plaster and let the female and chicks come out. Man maade crevices and holes that are abandoned are also used by birds like Barn owl. In some ducks the mammal burrow that has been abandoned is used. The interiors are usually not lines but the eggs are laid on soft interiors on Leaves, Wood chips and other soft material.The major consideration in these nests is protection from Elements like Water & wind. A bolt hole at the top of captivity is necessary so that the chicks can escape when they sense danger.
- Excavated Hole : These are holes made by Birds on Wood ( Woodpecker and Barbets) or on Sand ( Bee-eaters, Kingfishers, Crab plovers).They are usually of a uniform Tube like structure with a Flattened floor or a chamber in the end. In case a larger species evicts a small species then it will re-modify the nest as per its needs. The wood holes are made in the upright trunk , Branch or stumps usually on the underside to provide protection from rain and camouflage from predators. The entrance to the nest is usually at the top with the cavity dropping down parallel to the trunk or branch. These holes are excavated using the beaks as chisel . The holes take upto three weeks to make .The beaks are strong and as the Keratin layer is replaced regularly the wear and tear on the beak is minimal ( for more details on Woodpeckers abilities pls visit http://ogaclicks.com/wordpress/woodpecker-adaptation-ka-boss/). As the excavation happens the wood chips are carefully collected and deposited far away from the nest site . This is to avoid leaving any signs for predators to know that there is a nest nearby. Some wood chips can be used to layer the insides of the nest and absorbs any water collected. Both male & female take part in excavating the nest.
- Tunnel : These are holes made in sand by birds like Bee-eaters, Kingfishers etc. These tunnels are made on the sides of termite mounds, river banks, Erosion gulley, Sink hole and sometimes near a Mammal burrow. The tunnels are small and not enough for the free movement of the adult bird. They are about 1.5 meters deep on average and can go upto 3 meters. They have an upward incline to prevent water from entering them, and towards the end they level off. This is where the eggs are laid. As these tunnels are easily accessed by predators like Monitor lizard and other reptiles, the adult bird will defecate and regurgitate at the entrance of the tunnel giving it a very foul smell. The chicks will also come out and defecate the excreta on the tunnel walls . The chemicals in these waste make the predator avoid such smelly places.
Mud-pellet : These are nests built with mud ( high clay content) that can be made into smooth paste and will easily adhere and bind to each other, bake hard in the sun and air to provide effective insulator shelter. The Mud pellets are formed in the mouth of the bird by mixing saliva and water with the mud. It starts to set into shape as the bird takes it to the Nesting site . They are laid carefully in rows , on top of each other like a brick layer. As one row gets completed the next starts on top of it and this process continues till the nest reaches a desired shape and size. These nests are either built in walls and roofs of human settlements or in wild on the tree trucks , cavities ,rock walls and caves. The Swallows, Swifts and Martins build such innovative nests
The nest is made up of Mud, sometimes mixed with peat and other decomposing plant material. They are situated on ground and raise to a height of about 50 cm with a concave top. This is unlined and big enough to hold one egg. Birds which build this type of nest are Flamingos and Gannets. , The raised nests allow the birds to roam freely withoutn trampling on the eggs . The hard baked Turrets are used annually by these birds ,might not be same pair but they get used by the species. Manmade Turrets are also placed in breeding areas and the sight of them is believed to make the birds that were finding it difficult to breed get into breeding mode
Saras Crane sitting on its nest built on the man made bunds in the agricultural field
The nest building is done by Bothe partners usually. In some cases it is only the male that does the nest building as a process to attract the females. The nest is camouflaged with leaves and other articles to protect it from predators. In some case the nest is built near the dwellings of aggressive beings like Honey bees, Wasps, Ants etc. This will dissuade any predator from approaching the nest.
Spot billed pelican Collecting twigs for nest building
The nest are used for breeding and in some case as a regular Roosting place and for protect tion from elements like rain. The nests of large birds get reused Annually by same pair or others from same species. It is common to see two or three species fight to evacuate the nest . Common Myna is known to be very aggressive in this behaviour .