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Risk it, even if you’re a shy great tit!

By Paul Robinson - 14 May 2014 9:59:1 GMT
Risk it, even if you’re a shy great tit!

A hen great tit feeds her 4 young here, but what would she and her partner give up in order to keep her offspring alive and kicking? - Parus major image; Credit: © Shutterstock

As research grows in the new area of "animal personalities," the main drive is to investigate its effect on survival and evolution. All animals are now supposed to have slight behavioural differences that constitute a personality, but shynesss and boldness are the prime subjects of the work. Flexibility in behaviour is important, so how are the characteristics maintained through the generations?

It's possible that bold animals have a high productivity but survive less well, while shy lives give you less results but tend to prolong your life. However, the shy lifestyle could keep you alive long enough to breed, for example. Bold individuals would otherwise tend to produce more offspring. A wild population of Parus major, the personable great tit, were given novel environmental stimuli to cause them to react within the shy/bold axis of responses.

Caution over a novel object will cause birds to stop nesting or feeding their young or several other critical events in their career. This bird often uses nest boxes in gardens but remains completely wild, hiding in nearby vegetation and successfully keeping the young hidden when they make their first flights. Attaching a novel object to the top of their nest box would certainly interrupt normal behaviour. Resumption of normality was the measure used by Ella F. Cole and John L. Quinn of Oxford University and University College, Cork. They publish today in the Biology Letters of the Royal Society under the title - Shy birds play it safe: personality in captivity predicts risk responsiveness during reproduction in the wild.

A 40 minute trial period ensued after the "threatening" black and white flag (about 15x10cm) was placed on their box while females were on their nest, incubating eggs. Only females were observed, as males weren't seen on the nest during the incubation period. Non-returners were recorded as those ladies who failed to return before the flag was removed. Before the nesting, the females had been fitted with leg rings containing passive integrated transponders (PIT.) After the nestlings were 8 days old, for those where breeding was successful, the females wre captured again and their body measurements recorded so that they could be assessed for fitness.

The females took significantly longer to return when the flag had been placed outside their nest. 9 of the 43 females failed to return within 40 minutes and they tended to have lower scores in another exploration experiment than the returners. An EB score was given to each bird during the previous winter. This entailed measuring exploration behaviour of a novel environment (="EB") during the previous winter. This meant these birds were a little less than wild, having been assayed for 8 minutes and 11 activities and movement variables measured. This EB was also found to be repeatable, so it seemed to represent a small part of each animal's personality.

The females would normally have spent 10 minutes foraging for food. Staying away longer represents their dedication to more selfish survival rather than caring for their nestlings and eggs. 90% remained away from the novel stimulus for longer than 10 minutes, with the non-returners representing 21% of birds. Whether these females were more shy in every eventuality would be an interesting experiment, but they seemed to prioritise survival over their "reproductivity." Shy birds could possibly take longer to return to nests, but as average duration of these trips is not related to the pre-measure EB score, that argument seems unfounded.

Field-based support for EB's (exploration behaviour) links to risk responses in the environment tends to indicate personality is a true factor in animal survival strategy. Great tits are now using human-dominated areas to a much greater extent than before. It's possible that many rare and extinct species have been unable to adapt in this way with a variety of risky responses to our interference and removal of their resources.