Tits assess risk from predator from its shape

Submitted by Looduskalender EN on Fri, 02.12.2016 - 11:09
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Science news from the Year of the Great Tit edited by Marko Mägimarko.magi@ut.ee University of Tartu Bird Ecology department
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Tits as well as birds of prey gather at birdfeeders and this forces the tits to be constantly on watch. Distinguishing a dangerous bird of prey from a harmless species is vitally important.  While taking to flight  is crucial if a dangerous bird of prey approaches it is not necessary to waste energy in vain  if it is harmless.

From what do the tits recognize the birds of prey that are dangerous to them? The question might seem strange at first but finding an answer has been a real challenge to scientists and because of that until now relatively poorly studied. Evidently it works by way of the birds’ sight but what precisely are the details tonte in the raptor?

Precisely to this question – are the tits that visit the feeding tables scared by the shape of the bird of prey and how important is the plumage colour – a study carried out in the Czech Republic attempted to find an answer. One of the participants in the study was Killu Timm, postgraduate student of animal ecology at Tartu University,. As bird of prey a sitting female sparrowhawk figure was used since the sparrowhawk is the most common and dangerous visitor  for the tits using the birdhouse. The figure was placed near the birdfeeder and the feeding behaviour of the tits was monitored.

The size, eyes, beak, feet, claws, tail and wings of the figures used were typical of a sparrowhawk but the shape was varied with three different plumage colourings – one coloured typically as a sparrowhawk with striped belly pattern, a sparrowhawk shape coloured like a robin, and in addition also a sparrowhawk figure checked in purple and white-which  is a  plumage pattern that does not occur in birds in nature and accordingly should not raise any immediate sense of danger in the tits.

Nii näevad välja raudkullid rasvatihasena ja punarinnana. Edukaim maskeering on siiski ruuduline, sest seda ei oska tihased karta.

So sparrowhawks look as great tits and robins. The most successful disguise however was the chequer because the tits did not know to fear it at all. / Photo: Killu Timm

On seeing the last described figure the great tits and blue tits continued to visit the birdhouse since the unusual colour combination dominated over the morphological characteristics of the bird itself.  Two plumage variations – the one similar to a robin and the sparrowhawk shape without belly pattern were avoided like the figure reminding of a real sparrowhawk, It shows that figures with plumage pattern within the limits of those occurring in nature and with a shape similar to a bird of prey are seen as possible threats. It cannot be ruled out that the great tits judged the shape with a red breast to be a male sparrowhawk or that the red colour was seen as a warning colour.

It was also found that blue tits visited the birdfeeder more often than the great tits which points to less shyness or a smaller ability to connect the robin and the shape without belly stripes with a sparrowhawk. A greater motivation of blue tits to visit the birdfeeder is however more probable because – being socially lower in the hierarchy than great tits  - they must put more at risk to obtain food.

The changes in the ´behaviour of great tits on feeding indicate that for identifying a bird of prey certain colours of plumage details may be important but do not have a decisive importance. The tits may take a decision relying on other characteristics too. The figure of a sitting sparrowhawk is judged to be completely harmless only when it has an unusual colouring different from the natural.

Veselý P, Buršíková M, Fuchs R, 2016. Birds at the Winter Feeder do not Recognize an Artificially Coloured Predator. Ethology 122: 1–8. DOI: 10.1111/eth.12565