I am currently engaged in doing some writing about Blue Tits. This has involved understanding the range of forms of this popular little bird. It turns out there are at least eight forms of Blue Tits that can be described as separate species, and more than 20 sub-species. They are all a bit different from each other. The ones we are familiar with are limited to the British Isles and are the sub-species Cyanistes caeruleus obscurus. The ones on most of the European continent are Cyanistes caeruleus caeruleus. However, I will not go into the 20 or so other Latin names here, but I am hoping to publish a book about it during next year.
It seems that all species of tits originated in China, and the ancestors of Blue Tits dispersed across Asia, Europe and finallycolonised North Africa many thousands of years ago. Then there were a series of ice ages during which the ancestors apparently went extinct leaving the only surviving Blue Tits in North Africa. Some of these Blue Tits found their way to the Canary Islands and became isolated there. Others found their way to Southern Europe. From here they dispersed north as the climate warmed up and Blue Tits became common in most of temperate mainland Europe. Some of these birds probably moved into British territory before the land bridge at Dover disappeared about 10,000 years ago, rendering Britain a mass of islands occupied by a limited number of plant and animal species, one of them would become the sub-species of Blue Tit mentioned above.
Meanwhile the Canary Island’s Blue Tits on the different islands were changing in colour, measurements and song. There are now at least 4 species and 1 sub-species on different islands. Also as Blue Tits moved east into what we know as Russia, their diet was changing which resulted in these ones becoming almost white forming yet another species, namely the Azure Tit, some of which gave rise to a species near Pakistan called the Yellow-Breasted Tit. However, I am focussing on just Blue Tits, and my conscience would not let me write about a bird that I had not seen, so I had to visit the Canary Islands to see these ancient and rare Blue Tits that appeared before the British Isles became islands. In short, Canary Blue Tits are brighter in colour, shyer, the blue bits are darker and their songs are all different. The Blue Tits on the different islands have different coloured backs - all for now.
Dr. Martyn Stenning