European penduline tit
From The Economist
Aug 9th 2007
Abandoning offspring in search of new sexual conquests works—at least, for tits...
Researchers...studied the behaviour of a small bird called the European penduline tit... These birds are noted for the elaborate covered nests—which hang like bags from the branches of trees—that the males build to attract females. Investment in establishing a family is thus shared between the males, who provide the accommodation, and females, who supply the eggs.
After eggs have been laid, it is usual for either the male or the female penduline tit to leave their partner to raise the chicks. Between 50% and 70% of the time, it is the female who nurtures and provides for the brood but the male assumes this role in between 5% and 20% of nests.
[Here's the harsh part:]
Curiously, though, in between 30% and 40% of cases both parents desert the clutch...
They found that, over the course of the breeding season, deserting the nest once eggs had been laid boosted the number of descendants produced by the bird that fled. Whether male or female, the more often a bird deserted its clutches, the more mates it had and the more eggs were laid...
[Assuming that this behavior is genetically determinied, the next generation might have even more adults who abandon their offspring!]
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