Trip reports

Indoor Meeting- an island odyssey

Indoor Meeting- an island odyssey

Friday, 15 April 2011

Al Venables came to speak at our indoor meeting on Friday 15th April. I straightaway learnt something new. The fact that there are two kinds of islands: inshore and oceanic. Inshore islands used to be attached to the mainland. They only became islands as sea levels rose after the end of the last ice age. Our own Skomer and Skokholm are examples. This is why, as well as all the birds and seals, they also have their own subspecies of short-tailed field vole. The voles made the journey across a land bridge, but were cut off when the rising sea made an island.

Oceanic islands, on the other hand, were never attached to any mainland, but have always been separate and apart. On islands like this the only wildlife is that which can arrive by sea or air, so no voles or indeed other land mammals. (Of course, the arrival of man on many oceanic islands was quickly followed by the inevitable rats, dogs, cats, and often foxes, weasels or whatever else we thought it good to bring along. But that is another story...)

After a look at our Welsh favourites, the inshore Skomer and Skokholm, Al took us further afield to find some oceanic islands. First stop the Macaronesians.- the proper collective name for the Canaries, Azores and Madeira. The bird of particular interest here; the humble chaffinch. Many of us will have been to some of these islands, and if you have you may well have seen the chaffinches there. Remarkable for being the same, yet different to our own here in the UK. Much more blue and green in colour, and also more pink rather than the British brick red version. This is the island impact. Evolution in action and made more obvious by the isolation of the populations there from mainland birds leading to the differences we can see today. It has only relatively recently been discovered, by DNA testing, that the chaffinch left mainland Spain, made first stop at the Azores, and finally reached the Canaries via Madeira. By contrast the blue tit, also a separate and different looking bird to ours, came to the Canaries via North Africa, not Europe at all.

Al then took us on to other islands, Mauritius - home of the dodo, now known to have been a type of Pigeon. Pigeons are notable for being big island colonisers. Madeira and the Canaries have their own endemic species, as do many of the Pacific islands. We stopped in at Ascension and San Miguel islands on our way to Hawaii. Of course, it is not possible to look at these islands and not see the destruction to the local, unique wildlife caused by man and all his followers, the aforementioned rats, cats, dogs, etc. Some of what Al had to tell us was both gruesome and shameful. However, we came away on a positive note. There are alien species eradication programmes underway on many islands. Where there are island groups, sometimes where one has been decimated, others still have populations that can be used to try re-introduction. Much is lost forever, but much may yet be restored. A most interesting and thought provoking evening.