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Urban Great Tits - the 'Great' divide The Great Tits of Dronfield are about to play their part in an important ecological study. For the past two years I have been studying the song of one of our favourite garden birds, the Great Tit. I have been attempting to find out if the noise we are creating in cities is having an effect on the way they sing to one another; and the answer is yes! Great Tits in noisy places sing at a higher pitch that ones in the quieter countryside. This is incredibly important information; while most people are aware that air pollution and water pollution can have a very bad effect on the local environment, not many people stop to think about noise pollution. You may think that it is fairly hard to cut down on noise pollution, and you would be right. But it is still worth finding out what effect we are having so future developments are planned appropriately. You may also wonder if it really matters - birds sing a little higher, so what? They are not being harmed in anyway, or being put in mortal danger. However, a male Great Tit's song is one of the most precious things he has, here's why.
One of the many Great Tit chicks who hatched last year in the project nest boxes. When a male songbird opens his beak to sing, he does so with two possible intentions. Firstly he has to attract a female. Females are incredibly choosy over who they decide to mate with and who can blame them? They have one chance a year, two if they are lucky, to lay a clutch of eggs in which they invest everything. To give her chicks the best possible chance it is imperative she finds the biggest, brightest, strongest male, which she does by listening to his song. The second reason a male sings is to defend his territory. As well as providing him with food and shelter, territory also plays a part in convincing the female to stick around after her initial attraction. More food around the nest means the parents don't have to work as hard to feed the chicks and increased camouflage has obvious benefits. However, it is not easy to hold onto high-quality territory. Neighbouring males will be analysing his condition and vigour by his song, drawing conclusions on whether he would be able to physically defend his miniature kingdom. If they judge their own song to be superior, they may try to intrude. In a city, where the cacophony of human activity threatens to drown out his song, the male has to take drastic action - he sings a little higher to avoid competition with the low pitch traffic noise. But this change to a very specialised signal may make him seem less threatening to his neighbouring males, or even less attractive to the ladies. If this is the case, then birds from the city will not be able to settle in as well in the countryside, and vice versa for the country bumpkins. Over time, they may in fact end up staying away from each other due to this breakdown in communication which could lead to a divide in the population.
Recording Great Tit song During my project at Aberystwyth University, I have carried out experiments to see what happens when city and country Great Tits hear city and country songs. I found that they do recognise the differences - they behaved much more aggressively when they heard their own song type. My next step is to see if the females can hear these differences between city and country song and to see if they actually care. Again, I'll play them the different types of song to see which ones they are interested in; this is where the Dronfield Great Tits come in. Over the next few months I, along with a lot of help from BTO ringer, Geoff Mawson, will be colour ringing the great tits in Lea Brook Valley. This means that each Great Tit will be caught and given a unique combination of 2 colour rings on one leg so we can tell them apart in the wood. This way, I will be able to tell which male is singing which song, which female mates with which male, and which female prefers which song. There are lots of nest boxes around so we will also be able to keep an eye on how well they are breeding and how many chicks each pair is able to produce. As Great Tits can travel a good few kilometres, you may well see one of our birds on the feeder in your garden. If you do, it would be really helpful if you could note down the colours on its leg (especially which is on top, and which is on the bottom) and let me know (see details below). If you have colour ringed birds nesting in your garden - even better! Hopefully from all of this research we can gain a little more insight into the meaning of one of nature's most beautiful sounds. Emily Mockford
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