The Moorhen (Gallinula chloropus)

A common sight on Denis today is the Moorhen (Gallinula chloropus). This species will be familiar to most readers (see photos in sidebar) as it has a wide global distribution. It is native to Seychelles and Denis – Fryer recorded the species present on Denis in 1905 and Stoddart described them as common around the marshy areas on the island in 1977. I don’t recall seeing them when I visited Denis in 1998 but Hill (2002) recorded their presence.

When I commenced regular visits to Denis in December 2005, as part of my current work, moorhens were an uncommon sight on the island. In fact it would be more accurate to state that they were not commonly heard and rarely seen. The last 3 years however have seen an explosion of the population with birds and their chicks a common sight all round the island. They are of course very appealing to the guests around the hotel but numbers have reached such a level that they are now considered a pest around the vegetable gardens and hydroponic tunnels as they like to eat the new buds and impact upon production. Concern has also been raised in some quarters that they may be an aggressive competitor to the Seychelles magpie robin, as both are ground feeders, though as yet there is no substantive evidence to support this.

The reason for the population explosion is doubtless directly related to the removal of alien predators from the island, cats in 2000 and rats in 2002, as the moorhen being a ground nesting bird is particularly prone to their attentions. I observed a similar population explosion on Cousine Island in the past. When I started working there in 1993 moorhens were scarce and very timid with perhaps only 3-4 on the island. It soon became apparent that the birds were timid because they were on occasion still trapped for food by workers on the island. We stopped this practice and then (perhaps also linked with the eradication of feral chickens, construction of various ponds and emplacement of standpipes around the island) over the next couple of years the population on the island rocketed. I ringed a lot of birds at the time and monitored the population. As the numbers increased conflicts between neighbouring territories became common place with regular fighting and several observed incidents of infanticide where adults would raid the neighbouring territory and kill the chicks there!

Later as presumably all available territories were occupied we had periodic spates of emigration when whole generations of sub-adults would leave the island apparently en masse. We received confirmed records of birds I had ringed turning up on Cousin and Praslin as well as anecdotal sightings of ringed moorhens as far away as Fregate and Mahe!

Inter-territory fights are starting to become more commonplace now on Denis also and they can be quite vicious and prolonged. I was able to take a few photos of a fight last week and though blurred, they nevertheless communicate the intensity of the conflict quite well (see sidebar).

I have not ringed any Moorhens on Denis – too many other more important issues to follow – so it will be harder to assess but I expect we may soon have groups of sub-adults exiting the island in search of new homes. It may be worthwhile to contact our nearest neighbours on Bird and Aride islands and ask them to keep a look out for sudden influxes of birds.