IT IS not just human males who seduce prospective paramours with expensive gifts while bringing home cheap trinkets for their long-term partners. Some male birds do it too.
Great grey shrikes mate for life and raise offspring each breeding season. But the males also sneak away and mate with other females. To charm both long-term partners and mistresses the males offer gifts of food.
To test whether the males put more effort into their dalliances than their 鈥渕arriages鈥�, Piotr Tryjanowski at Adam Mickiewicz University in Poznan, Poland, and Martin Hromada at the University of South Bohemia in Cesk茅 Budejovice, the Czech Republic, recorded gifts made by 22 male shrikes to their partners and mistresses. They found that the average energy content of a gift to a mistress was 75 kilojoules, while gifts given to partners averaged about 19 kilojoules. Males often caught lizards, voles and other birds for their mistresses, which required six times as much effort to catch as the insects that they gave their partners (Animal Behaviour, vol 69, p 529). 鈥淚t is like a saying in Polish,鈥� says Tryjanowski. 鈥淎rtificial jewellery to the wife and real diamonds for the mistress.鈥�
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