Friday, 5 March 2010

The surprising moorhen

Moorhens breed every year in my local park and, for moorhens, they are quite tame and allow close approximation. In the countryside moorhens are more difficult to see, their loud "kirr-up!" call, often giving away their presence while they feed in marginal vegetation of canals and rivers. Moorhens are unusual in several ways. First, contrary to most birds, females compete for males, engage in female-female fighting and initiate courtship. In most bird species, females carry most if not all of the burden of parental care, they make energy-rich eggs, do most or all of the incubation and in several groups they protect and or feed the chicks for some time after hatching. No surprise then that males compete for such good assets and female are quite choosy as to which males should father their offspring!
Incubating moorhen
In contrast, Moorhen males are devoted dads and carry out most of the incubation and tending of the chicks. Some males, those with good fat reserves are better at incubating than others. Small males then to accumulate more fat reserves, and females fight to pair with those small fat males. There are also male fights but they are for territorial defence, instead of fighting for access to females.
An adult searches for food while a young chick begs on the water edge
Both males and females tend the chicks, which are quite mobile from birth, but need feeding and are shown what to eat by their parents. The other unusual habit of Moorhens is that chicks from the first brood often stay around in their natal territory and help feed their siblings from the second (or third) brood. This cooperative breeding is also found in Swallows and Long-tailed tits in the UK. As territory availability is very constrained due to aggressive territory defence during the summer, young first-brood moorhens are forced to stay in the parental territory and cannot easily disperse. The more food resources are available in their natal territory, the more likely is that first brood chicks will help raise their siblings and the more effort they put into it. Helpers can make a difference in the number of surviving chicks for the second brood and also reduce the parent burden when feeding the second brood.
Courting pair just before mating. A young chick was in their nest nearby.
A tiny chick still in the nest with its parents
More mobile chicks follow one of their parents
These fledglings were chased up the tree by an adult
Pair of moorhens foraging on frozen pond
References
Eden, S.F. (1987) When do helpers help? Food availability and helping in the moorhen, Gallinula chloropus Behavioral Ecology and Sociobiology, 21: 191-195. Here.
Petrie M (1983) Female moorhens compete for small fat males. Science 220: 413-415.

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