Sunday, July 25, 2010

The magpie's tale

The wonderful Iberian Azure-winged Magpies Cyanopica cooki are now busy getting around in gangs of youths and adults, making their presence felt with their raucous cries. They are a species of open, savannah-type woodland and their native habitat in Iberia is the Stone Pine Pinus pinea woodland.

For some time we hadn't realised the importance of these pine woods and many thought that they were largely introduced. True, many coastal pine woods have been planted but we know that they have been there for millennia. In our excavations at Gorham's Cave in Gibraltar we have found charcoal remains of Neanderthal camp fires. The charcoal belonged to the Stone Pine and we have found such remains in all the archaeological levels, the oldest being around 50 thousand years old. So coastal Stone Pine woods, in warm climate and sandy soils, have been around for a long time creating spectacular Mediterranean savannah landscapes.

For a long time too we had been under the mistaken impression that pine woods were not the natural formations in Iberia that had instead been dominated by oak woods. But the reality is that wherever we look in archaeological and lake pollen sites, the natural vegetation of large areas of Iberia was pine dominated. When we find Azure-winged Magpies today in oak dehesas (managed parkland) we are seeing them in secondary habitats; they are habitats that suited them because they had a similar structure to their native pine woods (not too dense to make closed forest which they don't like).

The other great misconception that was prevalent when I started birdwatching was that the Iberian Azure winged Magpies were not native here. Instead the colourful birds had been brought back by Portuguese mariners from China and escaped. We were looking at feral birds. How else could we explain a small range in south-west Iberia and a larger one in China, Korea and Japan, and nothing in-between?
Then we found the fossil remains of the Azure-winged Magpies in our caves too, along with the Stone Pine charcoal, going back 40 thousand years. Everyhting changed overnight. These magpies had been here all along!
Since then genetic studies of the Iberian and East Asian birds have revealed a separation that is probably over two million years old and the differences between them warrant giving them species status. So we have the Eastern Azure-winged Magpie C. cyanus and the Iberian one.
...and it helped us understand something else that we had been suspecting for a while - that the mid-latitude belt between Portugal and China had once been a vast belt of savannah that was broken down when the deserts of Central Asia, Arabia and the Sahara expanded.

Today, these beautiful, intelligent and social birds occupy the medium-sized crow job in the open woodland. Where the trees become too dense, they are gone and it is the Jay Garrulus glandarius (below) that takes over.
...and where trees are to few the Black-billed Magpies Pica pica and Jackdaws Corvus monedula rule (below).

But the Iberian Azure-winged Magpie will always have a place in my heart - because of its social character, antics, intelligence, and because they taught me a huge lesson in biogeography!