Building a nest. The black-capped weaver .
By Augustine Kayuni
Without going into a special school a pair of harmerkop collects different materials comprising more than 10,000 sticks to build a 1.5 meter nest which is said to very strong to accommodate a full grown man meanwhile an African fish eagle build a long lasting bowlike nest measuring 2 meters wide with its wall standing about 1.5 meters.
Being a natural product of a biological nesting behavior, a nest may be defined as a structure chosen or built by a bird for laying eggs and sheltering its chicks.
On the other side, nesting behavior is an instinct among expectant parents caused by the increase estrogen and other primary sexual hormones which are responsible for the development and regulation of the female reproductive system and secondary sex characteristics.
Just like many other birds of Africa, crown eagle breed mainly at the end of a raining season or at the beginning of dry season especially from July to November, to make preparation for the arrival of their chicks parents work hard to build a good nest.
In the tropical savannah forest of Africa, Crown eagles take not less than five months to build a new nest from the scratch but they may start to repair an existing on three months before laying eggs.
Scientists say it is common for an eagle pair to use a nest for more than five years and, unlike several other species of eagles, crowned eagle pairs rarely build more than one nest for alternate use.
Crowned eagle build very large nests, but it is credited for having one of largest nest among eagles because their nest may measure 1.5 meters across and go down 50 centimeters deep but those which a rebuilt usually after several years of usage, may measure up to 2.5 meters across and up to 3 meters deep.
Without attending any technical school, know which materials are capable of withstanding deferent weather condition, so the nest may consists of both dead and fresh branches.
Crowned eagles are known of using additional materials such as fresh leaves and animal dung to strengthen their nest meanwhile in the savannah of Africa the martial eagle takes a year to build a nest with a diameter of 1.5 meter which lasts for several years when it is 2 meters deep.
In the savannah different animals find a safe place for their newborns but different species of birds use unique skills to build nests for their chicks, it may appear an abnormal act before human’s eyes.
From the point of views scientists say maternal nest building behavior is is regulated by the hormonal actions of estradiol, progesterone and others which rise the importance of shelter to offspring survival and reproductive success.
Scientists go further by saying birds build nest from a knowledge which is passed from one generation to another through genetic materials, it is a genetic memory is a memory present at birth that exists in the absence of sensory experience, and is incorporated into the genome over long spans of time.
Among avian, they may be smaller but weaver birds build nests which are so complex whereby each species of these birds use different talent, skill and technique to design and construct a nest which meets different geographical conditions.
The Red billed buffalo weaver is a small bird weighing about 65 grams which tend to live in dry Savannah’s and sparse woodlands in a small family group or flock, and the prefer to pick crickets, locusts, grasshoppers, caterpillars, beetles, weevils, wasps, bees, ants, flies, and spiders behind a herd of herbivorous such as buffaloes.
A Red billed buffalo weaver leads a polygamous life which allows him to dominate three females in a nest which has one to eight chambers, these are social weavers whereby a lower ranking male control fewer females.
Although females do not tolerate other male partners in their chambers, among Red billed buffalo weavers it is the body power which decides the number of chambers and females, in some colonies lower ranking males may join hands to protect their position against aggressiveness behaviors from a superior male.
Usually weaver birds dominate the savannah of Africa where they stay in colonies but some species of weaver birds lead monogamous life, the Black capped social weaver which is found in Somalia, Ethiopia, Kenya and Tanzania.
Some species like thick billed weavers live in a large colony consisting of more than one hundred individuals, this specie allow polygynous which provide a male bird to control two to six females.
Usually it is the female Red billed buffalo weavers which build the nest on thorny twigs which allow the builder to divide it into two chambers and hanged from a thorny branch of an acacia tree.
The White browed sparrow weaver are active throughout a year building ten to sixty U shaped nests which hang from branches of trees, unlike other designs, the roosting birds have their nest built with two opposing doors while breeding birds stay in nests with one opening.
The White browed sparrow weaver are found in savannah of Africa where they build their nest on leeward side of a tree meanwhile the Grey capped social weaver are known to lead a social life which allow monogamous life whereby a nest is built by the whole family.
This specie builds their nests with two entrance whereby one door is closed few days before eggs are laid and opened few day before the chicks are fledged, meanwhile the Black capped social weaver leads monogamous life whereby a pair works together to build a nest with its two downward door.
Some weaver birds have specific season for building their nests, Speke’s weavers which are found in Somalia, Ethiopia, Kenya and northeastern Tanzania build their nest shortly after rain season in the savannah whereby a structure measuring from 24 to 26 millimeters long and 15 to 17 millimeters wide is built.
The tropical savannah forest around mount Kilimanjaro is always marked by oval nest built by the male Taveta weaver birds, like other weavers male use their long claws and strong bills to weave a complex structures which are hanged from an acacia tree.
Weaver birds are named after their nesting behavior and it is amazing that these birds, using only their beak to weave something so intricate and so consistent that one could never reproduce it with our hands, this ability makes these birds to be architect, construction engineer and a site foreman of their buildings On the other weaver birds are known for their bright colours which are used by male to attract breeding partners, some specie in a special strategy whereby the Yellow crowned bishop adapts a distinctive yellow and black plumage.
Among White winged widow-bird during breeding season male male’s yellow plumage turns dark and he gains more white feathers while others like the male of Red collared widow-bird remove parts of their feathers.
Other birds which build nests are Goliath heron which dwells in wetlands and build by using a structure from different materials with a diameter measuring 1.5 meter while in the same environment a Shoebill build a large nest with a diameter measuring up 1.7 meter.
In the savannah secretary bird build an almost flat nest with a diameter measuring 2.5 meter and 30 centimeter deep while Kori bustard build a nest measuring up to 4 meter wide with hallow measuring from 300 to 450 millimeters deep.
Scientists say bird build nests in round and oval shapes to enable thermal regulation during nesting and provide shelter for eggs during brooding a period in which parent bird sit to incubate due to the influence of parental brain