Or specifically: great tit personalities! While the idea that other animals have their own characters may seem a tad anthropomorphic, on a fundamental level it is not that strange a thought that certain individuals of a species will, for example, be more aggressive than others. If such behaviour is consistent across time and contexts, then that can be quite objectively described as a character trait.
Of course, the basic concept that animals can have their own personalities will be no surprise to many pet owners, but it raises many questions: what species have personalities? While a dog may be expected to, does a mouse? A lizard? A snail? What factors lead to an individual having a certain personality, and in turn, how does having that personality affect that individual’s behaviour?
For the last few decades, personalities have been studied across a range of animals, from mammals to birds and fish[1–6]. Across these species, one common finding has for instance been that individuals vary along a “shy–bold” spectrum, a seemingly simple value that determines many aspects of their behaviour. Exposed to a changed or new environment, “bold” individuals would be more explorative or aggressive, while “shy” ones would be more careful and passive. In a natural context, the “bold” behaviour can be seen as a “high risk–high reward” strategy: these individuals might encounter things like new territories or food sources, but they are also more prone to encountering and falling prey to a predator. Both extremes have their own benefits, and the “best” strategy will depend on many environmental factors. Since environments are rarely stable, it then makes perfect sense that a population will contain different individuals: in some years or areas, one type may thrive, while in other contexts the other will.
Although my own research does not directly focus on these character traits, the birds I work with do possess them still (in fact, one species, the great tit Parus major, has been a very common study subject for research on personalities), which can sometimes be quite noticeable. Below, I will detail two specific cases involving some particularly noteworthy individuals.
The first time a bird’s personality really struck me was when visiting a certain nestbox for a routine check regarding nest progression. Peeking into the nestbox, I could see that the female great tit was inside, incubating her eggs. When simply approaching the box, or otherwise when carefully moving a bird aside if having to check for incubated eggs or hatched chicks underneath, some of these birds will attempt to escape from the box, while others will fan their feathers and make loud noises (at an impressive volume for such a small bird) to try and repel you. Not only did this particular bird stay completely silent initially, she continued to be surprisingly calm even when I gently grabbed her to investigate the colour-rings on her legs. Instead of trying to either get away or get me to go away, she instead appeared to pull downwards, seemingly only desiring to get back to incubating her eggs.
Weeks later, performing another routine check on some other nest, the bird in that box behaved in the exact same unusual manner; behaviour I hadn’t encountered in dozens of other nests besides the one mentioned before. When I looked at the identifying colour-rings on her legs, those looked somewhat familiar, and once I checked my earlier notes I could confirm: it was indeed the same bird as before, now attempting a second brood after the first one had fledged.
The next year, I had all but forgotten about those encounters, when I once more found myself holding a particularly dedicated mother-bird, an individual seemingly more interested in incubating her eggs than her own wellbeing. I wasn’t able to verify her identity until I got home and looked at last year’s data, but of course: it was the same bird again! Her behaviour was so unique it had essentially been possible to identify her on that basis alone.
The second case offered an interesting glimpse at the underlying mechanisms for these character traits. This involved an unringed male great tit, who we tried to catch in order to give him rings so that we could recognize him in the future. Using a simple trap that prevents escape from the nestbox after a parent bird enters it to feed the chicks, he was successfully caught, and all seemed fine. As soon as I took him from the box however, from the very first touch, he screamed, in a terrible manner. This was not the normal shouty hissing call used to repel potential predators I heard so many times, but something that appeared to indicate the bird was in some kind of pain.
As I turned the bird in my hand, I looked for any external injuries, but could find none. In addition, it didn’t appear to matter how I held the bird or where I touched it, the screaming persisted. The situation only slightly improved over the following minutes as I proceeded to ring and measure him as normal. Once done, I immediately released him, but stayed around to look for any unusual behaviour that might indicate some underlying issue after all. However, he simply flew to a nearby tree and adjusted his feathers a bit, all calmly and in complete silence. Whatever had been the issue, it appeared to have been restricted to being handled.
Last summer, on what I remember being a particularly sunny morning, I was again patiently waiting near a box full of hungry great tit chicks, hoping to catch the father bird there. On a prior visit, we had already seen that this particular bird had an aluminium ring around one leg, indicating he was ringed as a chick in our study area, but had not been ringed as a parent yet (at which point they receive one or more colour-rings).
As you will have guessed from the way this story has been going, when he was caught the little thing started screaming awfully, as soon as my hand as much as approached him. Having encountered this behaviour before and now knowing it may not mean anything, I continued to treat this fellow like any other bird, though once again checking (and failing to find) any injuries or issues.
While the previous case of a bird with a recognizable personality concerned the same individual, I knew that could not be the case here: after all, the previous bird shouting as if his life depended on it had expressly been given colour rings already; that had been the reason for handling him at the time. This bird only had the aluminium ring, though the unique code on that did allow me to trace back where he had been born the year before. Turns out, yes, he was indeed born in that nest where I had captured the first shouting bird last year. Whether learned or genetically encoded, the adage “like father, like son” can apparently also be true in birds..!
-  Gracceva G, Herde A, Groothuis TG, Koolhaas JM, Palme R, Eccard JA (2014) Turning Shy on a Winter’s Day: Effects of Season on Personality and Stress Response in Microtus arvalis. Ethology 120(8): 753–767.
-  Michelena P, Sibbald AM, Erhard HW, McLeod JE (2009) Effects of group size and personality on social foraging: the distribution of sheep across patches. Behavioral Ecology 20(1): 145–152.
-  Cole EF, Quinn JL (2014) Shy birds play it safe: personality in captivity predicts risk responsiveness during reproduction in the wild. Biology letters 10(5): 20140178.
-  Sasaki T, Mann RP, Warren KN, Herbert T, Wilson T, Biro D (2018) Personality and the collective: bold homing pigeons occupy higher leadership ranks in flocks. Philosophical Transactions of the Royal Society B: Biological Sciences 373(1746): 20170038.
-  Toms CN, Echevarria DJ, Jouandot DJ (2010) A methodological review of personality-related studies in fish: focus on the shy-bold axis of behavior. International Journal of Comparative Psychology 23(1).
-  Sneddon LU (2003) The bold and the shy: individual differences in rainbow trout. Journal of Fish Biology 62(4): 971–975.