The last few months have been a blur of conferences, workshops. I attended a fantastic two week course on sensory ecology in Sweden (read about that here and here), I went to London and presented a poster of my work at the annual meeting of the Association for the Study of Animal Behaviour and have recently returned from the Joint meeting of the British Ecological Society and the Société Française d’Écologie in Lille. Time has been flying by and now Christmas is upon us but I wanted to write at least one more post for 2014 so here it is. These are four facts about my wonderful study species the great tit (Parus major).
My study species.
Every great tit has a unique personality
It’s true, you might think that a bird is just a bird and they are all the same but research has shown that this is not the case. In fact, many species of birds including Great Tits are now known to have distinct personalities and behave differently to one another, just like humans do. Researchers at Groningen University in the Netherlands found that when they exposed adult great tits to a completely new environment which they had never experienced before some birds were confident and bold and explored their new environments quite happily, while others were much more cautious and did not adapt quickly to the unfamiliar surroundings. Further tests have shown that birds which are bold or shy the first time they are tested tend to stay that way in repeated experiments. These results suggest that personality types are probably fixed characteristics which do not easily change. So, for anyone who’s ever said that animals have personalities, you were right. And it’s not just great tits either; research over the past few years has identified distinct personalities in a huge number of species including mammals, birds, insects and even anemones!
Different personalities. Great tits are not all the same. Image credit: Per Tillmann.
City great tits just aren’t as colourful as their countryside cousins
With their bright yellow breast feathers and marked and glossy black plumage great tits are hard to miss at the best of times and are particularly conspicuous during the breeding season when the males are singing their hearts out trying to attract mates. The purpose of the great tits striking colouration is not fully understood but it is likely that females are most attracted to those males which have the brightest and boldest feathers. It is unfortunate then for city birds that their feathers just aren’t as bright as their rural counterparts. A likely explanation for this is that the same carotenoid compound which is used to create the bright yellow colour in great tits feathers is also an anti-oxidant which reduces the physiological stress caused by oxidising pollutants in the environment. As urban birds are known to be exposed to much higher levels of pollutants than rural birds it may be that urban birds are forced to divert carotenoids away from their feathers and use them instead to reduce the levels of stress and cell damage that oxidising compounds can cause. Evidence of this comes from a study at Göteborg University in Sweden which found that the increased oxidative stress faced by urban birds correlated well with reduced levels of carotenoid pigments in their feathers.
Great tits can be incredibly aggressive
They might look cute and friendly but in reality great tits can be incredibly violent, and particularly so during the spring and summer when males are competing for the best breeding territories. During this period male great tits mark their territories by singing at regular intervals and this signal tells other males to move on and find an empty territory of their own. This works most of the time but not always. Sometimes males deliberately invade territories and may attempt to mate with the resident female or even try to force the current territory holder out and take over completely. If this happens the first thing the resident male will do is to sing frequently and loudly in an attempt to show their strength and to drive the intruder away. Should this not work things typically escalate quickly as the resident male flies back and forth across the intruder before coming into full-on physical confrontation. It is not common to see fights in the wild as invaders will usually leave before it comes to actual violence. It does happen sometimes though and you can see the result in these incredible videos.
Great tits sing at higher frequencies in cities than in rural areas
Cities are notoriously noisy places full of cars, people and factories, with aircraft flying overhead and noise from building sites, road repair crews or similar urban development projects. This level of noise is something which wild animals have only had to face in the last century or so, and for species which communicate using sound it could make life in cities very difficult as their vocal signals are easily lost amongst the clatter and din of urban life. Great tits are a good example of a species which might be expected to fare badly in urban habitats as the males rely on communicating by song to defend their territories, show aggression towards rivals and attract mates. To make matters worse, the typical song of a great tit lies in exactly the same frequency range as the background noise of most cities and this means that when a great tit sings its song is quickly swamped by urban noise and cannot be heard by other birds. Yet despite this, great tits are one of the most common song birds seen in city parks and at garden bird feeders so how do they manage to cope with the noise problem? The answer is simple but ingenious. Urban great tits have adjusted their typical song frequency so that they now sing around 350Hz higher. That might not sound like much but experiments have shown that this small adjustments means that the song of urban birds travels above the low-frequency rumble of urban noise and can still be heard by other birds, even at long distances. Genius!
When there are high background noise levels great tits adapt by singing at a higher pitch. Figure from Slabbekoorn and Peet (2003).
References
Every great tit has a unique personality
Dingemanse, N. (2002). Repeatability and heritability of exploratory behaviour in great tits from the wild Animal Behaviour, 64 (6), 929-938 DOI: 10.1006/anbe.2002.2006
City great tits just aren’t as colourful as their countryside cousins
Isaksson, C., Örnborg, J., Stephensen, E., & Andersson, S. (2005). Plasma Glutathione and Carotenoid Coloration as Potential Biomarkers of Environmental Stress in Great Tits EcoHealth, 2 (2), 138-146 DOI: 10.1007/s10393-005-3869-5
Great tits sing at higher frequencies in cities than in rural areas
Slabbekoorn, H., & Peet, M. (2003). Ecology: Birds sing at a higher pitch in urban noise Nature, 424 (6946), 267-267 DOI: 10.1038/424267a
