Last month’s Nature Notes may have seemed a bit depressing, so this month I have resolved to write in a more positive tone. I am currently writing a book on Blue Tits. These fascinating little birds never cease to cheer me up as they are so cheerful and resourceful. The colours of Blue Tits are similar to those of Plant Earth as seen for space; blue for the oceans, yellow for the deserts, green for the forests, black for the deepest water and white for the snowy regions such as the Poles.
Blue Tits are one of the few birds actually increasing in number throughout their European range. Their ancient history is fascinating. Their ancestors almost certainly came from China, and spread across Asia to Europe and Africa. Then a series of ice ages and other climatic extremes caused the ancestors to go extinct, isolating the remaining Blue Tits in North Africa. From there they colonised the Canary Islands where they diversified but remained isolated. They then colonised Europe from Africa and spread north and east, back into Asia and Russia where they lost most of their colour except for black white and blue and became Azure Tits. Some of these in Asia developed a band of yellow across their breasts to become Yellow-Breasted Tits.
Meanwhile in Europe the Blue Tits spread across Spain, France Italy and the entire European mainland and then crossed the English Channel to the British Isles. They are even now making their way up through Finland and Norway a little further each year. One even reached Shetland and another the Faroe Islands recently. One of the secrets of the Blue Tit’s success is their adaptability. They readily come to bird tables and nest in the nest-boxes we make for them. They also use other structures like letter boxes, drain pipes and even a boxy ash tray at the University of Sussex where I work.
One other indication of their adaptability is the way they learned to open milk bottles during the last century when milk came in glass bottles and were delivered to everyone’s doorstep. They just took the cream as this portion of the milk does not contain much lactose which they cannot digest. They do not like skimmed milk as it makes them ill.
Another reason for their success is their ability to time their breeding to coincide with the spring flush of moth caterpillars to feed their babies.
Dr. Martyn Stenning