In much the same way that we have different styles of houses, birds too have different types of nests. Similarly, features unique to the climate – air-conditioners in hot climates, double glazing and under-floor heating in colder climes – are replicated in the construction of nests.
Clearly birds have neither fans nor heaters, but they do choose sites and materials adapted to their individual environmental niches. In this article we will focus on just a few of the remarkable ‘homes’ created by our avian cousins.
The ones which come to mind first, based on the sheer intricacy of their design, have to be the nests of the various weaver species. As the name suggests these nests are constructed by the intertwining of pieces of grass until a ball-shaped nest emerges. Made solely by the males, the finished work is inspected by passing females, who will either accept or reject the nest. If not one of the females is suitably impressed by his handiwork, the male will tear down the nest and start over. Wow! Talk about dedication! If, on the other hand, a female accepts his efforts, she will start to line the nest with feathers and other soft materials in preparation for egg-laying.
The record for the largest nest constructed by a pair of birds goes to the appropriately named hamerkop. These birds, with their unique hammer-shaped heads, construct their arboreal mansion in a tree close to water. The nest starts as a V-shaped cup in the fork of a tree with the sides gradually being built up around an internal cavity. The roof is a masterpiece of engineering, constructed with one bird inside the nest and the other on the outside. Collectively they add a matrix of twigs, reeds and grass, creating a platform close to a metre thick. The internal chamber is then lined with mud which insulates the eggs and hatchlings, while the parents are out frogging. Artistic external decorators, they may adorn the nest with bones, tortoise shell, cardboard, rags, string or anything else they can lay their beaks on. The finished structure can weigh up to 50kg and be 1.5m wide. Tenants, or squatters (depending on how you choose to look at it!) such as owls or geese will take up residence atop this palatial structure. Imagine, a condominium sans rent!
Many birds use holes in trees or river banks as nesting spots. Bee-eaters excavate their own burrow by digging with their bills and removing the loosened material with a bicycling action of their feet. The tunnel goes back approximately one metre into the bank, ending in an oval egg-chamber with a spoon-shaped floor. The chamber is unlined and has a narrow lip separating it from the tunnel. It would seem these birds like to change neighbours often, as they create a new nest each season.
Birds such as the white-crested and Retz’s helmetshrikes make considerable use of spiders’ silk in their nests. Collecting the web on their characteristic bristle-like facial feathers, they then utilise it to plaster the outside of the nest until it is smooth. The nest is also attached to the branch on which it sits with cobweb. The delicate and beautifully-coloured sunbirds also use spider-web silk in their nest construction. They use it to cement together the dry leaf matter that constitutes the rest of the nest.
Doves are lazy-day builders; their nests consisting of little more than a collection of twigs and grass, situated in a tree or other suitable structure. They have poor house-keeping and sanitation standards too. Unlike most other passerines – who will remove the chicks’ faecal sacs – doves utilise the chicks’ excreta to cement the flimsy nest together, one can only assume in an attempt to support the family’s increasing weight.
Aquatic birds, such as African jacanas and red-knobbed coots, favour ‘house-boat’ style residences. Constructed from floating vegetation, these nests are free-floating to ensure they do not flood if the water level rises. When the parents are not in attendance, they will cover the eggs with more plant material in an attempt to conceal them from would-be predators.
So, whether their chosen residence is a tailor-made high-rise, large or small, apartment or river-side mansion, rented or owned, birds also employ the motto, “Wherever I lay my head, that’s my home!”