The appearance of a Caspian Tern at Rudyard Lake on Friday gave us the possibility of a twitching trip to see a species that neither of us has ever seen in the UK let alone in Staffordshire. Rudyard Lake is less than 50 miles away and Caspian Tern is a genuinely rare species in the UK; there have been only eight previous records in Staffordshire and this was the first since 1999.
We didn’t go!
It didn’t take more than a few seconds to realise that there wouldn’t be much sense in spending time and money chasing off to see a species that we can see almost every day in the Algarve. We do enjoy seeing and watching Caspian Terns but the only reason to have gone would have been to add a tick to a list.
We realise that we are lucky to be so familiar with Caspian Terns. In Tavira we sometimes see one come into what is effectively the town centre, fishing in the Gilão River. Although they don’t breed in the Algarve, there are usually a few to be found throughout the year either in the Ria Formosa or at Castro Marim. These birds are almost certainly from the breeding population around the Baltic Sea many of which winter in West Africa. We see them on their way south in the spring and on their way back later in the year but many stay in the Algarve through the winter and a few, presumably sub-adult non-breeders, spend the summer with us. We know of only one record of a colour-ringed bird in the Algarve: a bird seen by Ray Tipper on 30th September last year at Castro Marim that had been ringed just 91 days earlier as a nestling in Sweden.
Apart from in Portugal, we have also seen Caspian Terns in Finland, Costa Rica, South Africa, various parts of Africa and in several US states - they are widely distributed around the world also breeding in China, Australia, New Zealand and elsewhere. It is the world’s largest tern, almost the size of a Lesser Black-backed Gull and its striking large red bill makes it unmistakeable.
In Britain there have been more records in July than in any other month, which is perhaps a bit surprising. The assumption is that these birds are also from the Baltic population although there is a record of a bird ringed in North America being found in Yorkshire back in 1939.
Perhaps surprisingly Caspian Tern is regarded as monotypic; as yet there are no recognised sub-species although no doubt someone somewhere will be working on that! It is reported that birds from North America, the Red Sea and the Persian Gulf are somewhat smaller than European ones, while birds from South America and Australia average larger.
The Rudyard Lake bird stayed throughout the weekend and was apparently last seen flying out to the north early on Monday afternoon.