14 DAY TRIAL // Sometimes, the war of the sexes can get out of control. Parents can abandon their offspring just to have a little more sex. Males for spreading their genes, and females to get more varied genes.
In the case of the penduline tit (Remiz pendulinus), a European species, this could mean that one in three clutches of eggs are abandoned, as found by a new research. This is a paradoxical way of improving sexual fitness, by abandoning the nest. Males and females can have sex with up to seven different partners during a breeding season and their attitude towards the eggs varies with the different clutches. During the breeding season, over 50 % of all clutches are cared for by the female, and up to 20 % by the male; the rest, about 30 %, are abandoned.
The tit males get rid of their duties by often fleeing the nest before the egg-laying is complete, whilst females sometimes hide their eggs from the males so she can flee, too, before he realizes how many eggs have been laid. The abandoned males in many cases flee the nest. "If you are a penduline tit your perfect partner is one that is happy to stay home and look after the kids, whilst you go off and find a new partner," said Dr Tamas Sz?kely from the University of Bath (UK) who collaborated with researchers from E?tv?s University (Hungary) and University of Groningen (Netherlands).
"But whilst this is great for you, for your partner it is not so good. They end up having to stick around and rear the kids, which means they miss out on the opportunity to have more chicks themselves. It also increase their risk of being taken by predators while incubating the eggs or feeding the young."
"What is unusual about the penduline tit breeding system is that in one in three cases both males and females are willing to abandon the nest, even though the clutch will perish as a result. This could be said to be reminiscent of Hollywood life-styles with plenty of mating opportunities that may lead to neglect for the family at home."
"We have shown that over the course of the breeding season desertion enables the parents to produce a greater number of offspring, improving their reproductive success over those more willing to stay home. Interestingly, however, the sexes play the same strategy; whatever is good for the male is harmful for his female, and vice versa. Neither the males nor females are saints."
Childcare varies enormously throughout the bird kingdom. In polygamous species (one male mates with a harem), the female care for the offspring alone (like in pheasants and peafowl). In most songbirds and raptors, both parents care for the young although the female takes the bulk of care, while in some species like nandu, cassowaries, phalaropes, lily-trotters or buttonquails, males accomplish all of the childrearing. "As far as we know this willingness for both sexes to abandon the nest for the sake of new mates is unique. Our findings reveal an intensive conflict between males and females over care that has affected the behavioral evolution of this species", said Dr Sz?kely from the University's Department of Biology & Biochemistry.
