Nature Notes February 2017
I nearly missed the deadline for these Nature Notes. The reason was that I was too pre-occupied with writing my book, due to come out later this year on Blue Tits. I am embarrassed to say that NN had slipped my mind until the all-vigilant Editor contacted me to see what had happened. Therefore, I hope you will forgive another note about Blue Tits? It is winter, and Blue Tits are on my mind, so let’s think for a moment about what Blue Tits do in the winter, and how they survive.
Blue Tits are described as partial migrants. That means that part of the Blue Tit population migrates and the other part is sedentary. There are good reasons for that. All but four native trees in Britain are deciduous, so woodlands become bare and draughty and food for small birds is hard to find. Beech nuts are a favourite food for Blue Tits at this time, but these can be scarce. Additionally, Male Blue Tits have often already selected the cavity in which they would like to breed during the following summer, so they stay behind and defend it vigorously from other animals. Meanwhile, female Blue Tits are free to search for food wherever they want to. Most territorial male Blue Tits are more than one year old and dominant to yearlings. Therefore, the Blue Tit yearling males and females of any age disperse south and west, to find milder and safer places to spend the winter. These are often Reed-beds and people’s gardens. So the marauding Blue Tits that you see at your feeders are mostly females and some yearling males.
The Blue Tits that end up in Reed-beds do so because insects like to hibernate in the hollow stems of Reed and other large grasses. Blue Tits can be seen peeling them open to find lunch. The Reed-beds are also dense and sheltered from winter weather and provide some protection at night for roosting. Older males, meanwhile, are lunching on such things as insect eggs, spiders and seeds. In order to cope with the switch from insects to seeds, the winter beaks of Blue Tits become shorter and wider, more like the seed-eating Finches. Male Blue Tits that have obtained a breeding cavity, sing loudly from the beginning of January to declare their ownership of a territory. Their song can sound like ‘see – see – tu-tu-tu’ or something similar, it can be quite variable. You can hear it right now in Lake Wood, a focal location for the natural history I am writing about in my book – to be called ‘The Blue Tit’.
Dr. Martyn Stenning