The main advantage of sexual reproduction is that combining genes from two parents greatly enhances the genetic diversity of the next generation. Sex literally provides the variation on which natural selection operates.
This might seem a long way from the sex life of plovers, but bear with me. If the main advantage of sex – with all its distracting angst and aggression – is to create diversity, it stands to reason that promiscuity should be the norm. All other things being equal, you should have sex with many different individuals to increase the likelihood that at least some of your offspring will survive, whatever hurdles are presented by an ever-changing world.
Because humans are largely monogamous, we tend to forget this fundamental premise of sex. But it is humans who are unusual; most animals and plants are promiscuous. For example, more than 90 per cent of mammals are polygamous. Monogamy is thought to have evolved among humans because it benefited males to remain with their partners to protect their offspring, largely from infanticide by other males.
Birds too are unusual in being largely monogamous. This results from the high degree of parental care needed to raise a brood of chicks to independence. Of course we now know that many birds are only socially monogamous; like humans, both sexes might seek out extra-pair mating opportunities but remain with a social partner for the sake of the children. Such cuckoldry only adds further tension to an already tricky partnership.
この記事は African Birdlife の January - February 2021 版に掲載されています。
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この記事は African Birdlife の January - February 2021 版に掲載されています。
7 日間の Magzter GOLD 無料トライアルを開始して、何千もの厳選されたプレミアム ストーリー、9,000 以上の雑誌や新聞にアクセスしてください。
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EXPLORING NEW HORIZONS
Keith Barnes, co-author of the new Field Guide to Birds of Greater Southern Africa, chats about the long-neglected birding regions just north of the Kunene and Zambezi, getting back to watching birds and the vulture that changed his life.
footloose IN FYNBOS
The Walker Bay Diversity Trail is a leisurely hike with a multitude of flowers, feathers and flavours along the way.
Living forwards
How photographing birds helps me face adversity
CAPE crusade
The Cape Bird Club/City of Cape Town Birding Big Year Challenge
water & WINGS
WATER IS LIFE. As wildlife photographer Greg du Toit knows better than most.
winter wanderer
as summer becomes a memory in the south, the skies are a little quieter as the migrants have returned to the warming north. But one bird endemic to the southern African region takes its own little winter journey.
when perfect isn't enough
Egg signatures and forgeries in the cuckoo-drongo arms race
Southern SIGHTINGS
The late summer period naturally started quietening down after the midsummer excitement, but there were still some classy rarities on offer for birders all over the subregion. As always, none of the records included here have been adjudicated by any of the subregion's Rarities Committees.
flood impact on wetland birds
One of the features of a warming planet is increasingly erratic rainfall; years of drought followed by devastating floods. Fortunately, many waterbirds are pre-adapted to cope with such extremes, especially in southern Africa where they have evolved to exploit episodic rainfall events in semi-arid and arid regions. But how do waterbirds respond to floods in areas where rainfall - and access to water - is more predictable? Peter Ryan explores the consequences of recent floods on the birds of the Western Cape's Olifants River valley.
a star is born
It’s every producer’s dream to plan a wildlife television series and pick the right characters before filming.
