As with most animals, birds' lives include the vital task of producing offspring. Before that, each has to find a suitable partner. In the world of birds, the competition between males in chasing females is vigorous. The females are very choosy in selecting healthy "other halves", to ensure that their offspring will in turn have the best chance to prosper. For successfully courtship, the males must employ a range of strategies to attract the opposite sex.
Female birds may prefer a brightly-coloured partner with shimmering feathers, as the plumage is an indication of the male's health. In the long history of evolution, colourful males are therefore selected while the females are often drab.
To enhance the "handsome" strategy, some birds display their vivid feathers in dances. Superb Bird-of-paradise (Lophorina superba) of New Guinea rainforest and Victoria's Riflebird (Ptiloris victoriae) of Australia are among the experts in this.
Peafowl is another bird we are all familiar with, and cannot be missed out. The peacock (males) spread their tail feathers in courtship. A long tail, bright and symmetrical feathers with numerous eyespots all indicate health and fitness, and are more attractive to the females.
Female birds are also attracted to loud and lasting songs. It may be even better if the melody is complicated, signifying a strong, enduring and experienced singer. Asian Koel (Eudynamys scolopaceus) is a common bird in Hong Kong. You can often hear its "Ko-el" song at dawn in spring; it's simple but repeated often for long periods, surely demonstrating stamina.
Some birds do more than just sing. The courting ritual of Domestic Pigeon (Columba livia) includes straightening the neck, puffing up the neck feathers, and chasing the female while making cooing noises. Eurasian Tree Sparrow (Passer montanus), on the other hand, chatters and hops around its partner in a cute manner like a wind-up toy.
Some birds impress the other halves by dancing, and some couples may even dance together. For example, Bridled Tern (Onychoprion anaethetus) can dance a "tango", while Black-winged Stilt (Himantopus himantopus) performs a "ballet". The grebes' dance is most amazing: the pair swing their heads in rhythm, then paddle rapidly to "run" on water! Their movements are rapid, and if one cannot follow the footsteps of the other, then the matching fails!
Some males will prepare courtship gifts, or special courtship grounds. A male bowerbird builds a complex structure called a bower on the ground, using twigs and branches decorated with collected fruits, leaves, flowers, feathers, shells and even human items such as coins, plastic pieces and buttons. After visiting several bowers, a female will choose the most impressive architect as its mate.
A male may also choose a simpler option, like grebes – which apart from dancing will donate algae as building material. The larger the algae the more charming to the female.