Courtship is a social behaviour in which there is an interaction between the male and female members of a species leading to mating and reproduction. Courtship evolved due to the fact that very large number of sperms is produced which must search and fertilise few ova leading to competition among sperms.
Since males possess sperms, they must compete with one another in order to win over the female to fertilise her ova which are a limited resource. The gametic selection has translated into sexual selection among males and females, leading to male-male competition and female choice. Courtship display is an extension of this male-male competition in which males evolved various devices and techniques to persuade female to reproduce.
IN DROSOPHILA
Courtship behaviour in vinegar fly (Drosophila) was described by Bastock & Manning (1968). Male and female come together within 2 mm of each other and then male circles around her. Female is discriminatory and wrongly approaching males are kicked off. Male vibrates one wing during circling which stimulates the female.
Vibration of the wing produces sound as well as air current which act on the antenna of female. This is followed by touching with front tarsi and genitalia licking. Mating occurs after about 3 minutes by male mounting the female. Often mounting occurs but mating is unsuccessful. Courtship of wingless male is not accepted by female.
IN 3-SPINED STICKLEBACK FISH
Three-spined stickleback fish (Gasterosteus aculeatus) is found in ponds and rivers of Europe. Male is bluish-black in colour with bright red belly while female is silvery in colour. Male finds a place in sandy bottom where there are weeds. Male builds a tunnel-like nest in sand among weeds and defends territory around the nest. Then male swims near the surface over the nest to invite females.
Other males are attacked and chased away aggressively. Male swims upward from below and stabs the female from below with his dorsal spine. When response of female is positive both of them swim in zig-zag fashion towards the nest. If female likes the nest it enters inside and male follows.
Male places his head against the tail fin of female and quivers, which provokes the female to release eggs. Male then deposits his sperms over the eggs and female is chased away. Male then swims again to the surface to solicit another female. Up to 5 females can be made to lay eggs in his nest by the male. Male then guards the eggs and oxygenates them by fanning with fins till they hatch.
IN BIRDS
Courtship behaviour has evolved in birds to the highest level in which auditory as well as visual displays are used by males to impress females. Shape, size and colour of feathers have evolved for displaying and dancing.
Singing generally has evolved in male birds living in dense forests where there is limitation of visual distance but sound can travel to long distances. For example, males of cuckoos, starling, lapwings, larks, grackles, nightingales and bulbuls are accomplished singers and use these auditory stimuli to attract females.
Some birds imitate other animals to impress females, e.g. grackles, parakeets, starlings, magpies and shrikes. Lyre bird of Australia is a celebrated mimic whose male can imitate the sounds of mobile phones, alarm clocks, tweets of reversing vehicles and bike engines only to impress female of his extraordinary capabilities.
Nest building is also used as a means of visual stimulus to attract female. In weaver birds and bower birds male builds a nest and invites females to inspect it. If female likes the nest mating occurs. In the case of oropendolas (Zarhynchus) it is the female that builds the nest and invites males into it.
Feather display by male is a common phenomenon in birds’ courtship, e.g. birds of paradise, peacock, pheasants, grouse etc. in which length and brilliance of feathers is the deciding factor to attract female as well as to warn other intruding males.
Dancing is also a stimulus used by males to woo females in a large number of species of birds. Dancing and cooing in pigeons and doves is a courtship behaviour. Peacocks and birds of paradise males not only display their feathers but also dance and show different tactics to attract females.
Aerial displays in flight and aerobatics have been recorded in pigeons, kites, buzzards and doves. In buzzard (Buteo) male and female hook their claws and fly in circles before mating. Lek birds such as grouse clear an area of weeds in the forest where all males and females of the area gather. All males dance and display their feathers in this mating arena, while the females passively watch the proceedings. Mating takes place after several hours of dancing.
In the case of crested grebe (Podiceps cristatus) both male and female come together and do head-shaking ceremony after which both carry out diving displays. Then both rise vertically to the surface of water and do penguin dance after which nest material is exchanged. Mating takes place after a considerably long courtship display.
Jackson’s whydah (Drepanoplectes jacksoni) male prepares a display arena by clearing grasses and then dances around the central grass tuft and jumps into air frequently while the female watches. Mating takes place but female raises her family alone without any help from male.
Lesser florican jumps above the tall grasses and floats down with outstretched wings and tail, loudly calling all the time. Females are attracted by this display.
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