The Indian Mynah (Acridotheres tristis) – a growing problem…

In my post of February 17th I recorded that a Magpie robin chick had been attacked in its nest by four Mynah birds working in unison! The male did his best to defend the chick but it was this territory that had lost the female only a day or two before. As such the male was alone and whilst he fought with two birds the other two swooped on the nest to attack the chick! The chick was saved by the intervention of Catherina who fortunately was working in the territory at the time and ultimately she has taken it into her care in order to raise it by hand. This kind of cooperation between the mynahs speaks to their high intelligence. I recall in the mid-nineties seeing four mynahs working together on Cousine island to drive a Fairy tern (Gygis alba) from its egg which they then promptly broke and consumed.

The mynah bird appears to be the main problem that faces the magpie robins on Denis with at least two other nests known to have been destroyed by mynahs and at least one chick fatality that suggested mynah involvement.

The Indian or Common Mynah (Acridotheres tristis) is an introduced or Invasive Alien Species (IAS) to Seychelles. Its native range is central and southern Asia and it is widely distributed throughout the Indian subcontinent. It is believed to have been introduced to Seychelles via Mauritius in the late 18th century either as caged bird or possibly as an early and misguided attempt to control crop pests.

The mynah is a highly intelligent and adaptable bird and exploits all terrestrial habitats in the central archipelago from reef flats exposed at low tide to the highest peaks. Though predominantly a ground feeder, the mynah is able to exploit diverse local and temporary food sources. In Seychelles they have been identified as competitors with (for nest sites and food) and/or predators of (chicks and eggs) threatened endemic land birds such as the magpie-robin, Seychelles white-eye (Zosterops modesta) and Seychelles Scops owl (Otus insularis).

Since its introduction the species has spread progressively throughout the central archipelago. Its date of arrival on Denis is not clear but was sometime in the 20th Century as Fryer did not record the bird on the island in either of his visits (1905, 1908) but Stoddart did record it as present during his visit in 1977. Today at a very rough estimate there are some 300 – 400 mynahs on Denis. They can be best seen in the late afternoon feeding on the runway when as many as 150 birds may be seen at one time spread across the entire length of the strip.

The problem now is how do we go about controlling the mynah population? This is far from easy for various reasons. The mynah population has been controlled in the past on Denis using poison. This was done in 2002 in tandem with the rat eradication project that year. The birds were habituated to being fed in a certain location over a period of several days and then the food source was poisoned. This was very effective but was only possible at that time because the island had no rare native birds. Today particularly with the Magpie robin and Fody (and to a lesser extent the Warbler and Flycatcher) we cannot risk using poison for fear of killing one of these rare birds either by direct or secondary exposure to poison. The other options are trapping or shooting but these too bring difficulties.

Traps cannot be left unattended as again non-target species may be caught; as such trapping methods used must be i). ones that do not inflict injury or harm in the process of capture, and ii). must be permanently manned such that non-target birds can be promptly released; and again the mynah’s extraordinary intelligence also comes into play. Whilst working on Cousine Island in the 90’s I instituted a bounty system on the island such that staff were paid SR100 for each mynah they caught. SR100 was worth a lot more then than it is today and consequently staff devoted quite a lot of time and effort to the capture of the birds. In particular I recall Mme. Juliana Souffe catching birds using a simple walk-in pull-string trap that she baited with open papaya fruit. She set the trap up across a track from the kitchen where she spent several hours a day and when a bird went in she simply pulled the string and bagged a bird! After initial success however this method ceased to work. The birds worked out the link of the string to the trap – so Juliana changed the string to a transparent nylon fishing line and latterly buried it from the trap under the sand but the birds still worked it out. What was particularly alarming however was that birds did not just learn to avoid the trap and resist the temptation of the mouth-watering fruit inside – an adaption that one could perhaps expect. Rather they worked out that the string and not the trap was the dangerous item… so they would happily enter a trap which had no line attached and feast on the papaya but would not enter a trap which had a line attached…. now that is frighteningly intelligent!!!

Shooting poses other problems. Firstly it can be very difficult to get permission for a firearm, even an air rifle; secondly the mynahs work it out!! On Cousine we got permission for an air rifle in 1995 and initially were able to shoot a few mynahs. Then however after awhile if you walked around with the rifle you never saw a mynah, but when you didn’t have the gun you saw them everywhere! In other words they had associated the gun with the danger rather than just the human! We could of course seek help from the military or a police unit to get a marksman over with a 2.2 rifle but such activity is not compatible with a hotel resort in full operation – so what to do?

We have actually identified a company in Australia that makes a specialised mynah trap which has certain features which are supposed to overcome the wits of these brainy birds. So I have asked the island owners to order a couple so we can try them out. Let’s hope we can get them in the not too distant future and that they may prove effective in gradually getting the mynah population under control!