Thursday, October 25, 2018

Birds Startled by Moving Sticks

Do animals – like humans – divide the world into things that move and things that don’t? Are they surprised if an apparently inanimate object jumps to life?

Yes – according to scientists at the universities of Exeter and Cambridge.

The researchers tested how jackdaws responded to moving birds, moving snakes and moving sticks – and found they were most cautious of the moving sticks.

The study, using remote-controlled objects placed in jackdaws’ nests, will help scientists understand how birds perceive potential threats.
Credit:  University of Exeter

“Although as humans we see the divide between animate an inanimate objects as an intuitive one, we’ve had very little evidence that wild animals also see the world this way,” said lead author Dr Alison Greggor, formerly of the University of Cambridge and now at the San Diego Zoo Institute for Conservation Research.

“Laboratory studies have shown that human infants and a few other species discriminate between animate and inanimate objects.

“This ability is assumed to have evolved to support social interactions, but its role for wild animals has never been examined.

“Our work extends the potential function of this ability beyond the social realm. It might therefore be a more common ability than previously thought.”

By placing remote-controlled objects in jackdaws’ nests, the researchers tested how the birds assessed possible threats to their offspring.

Jackdaws were startled by any movement, producing alarm calls, but they delayed longest in entering their nest box after encountering an “inanimate” object that moved (ie the remote controlled stick).

This suggests they recognised the movement as unexpected and delayed entering the nest in order to gather more information about the situation.
Experimental stimuli on movement tracks. The birds (a) were freeze-dried specimens found freshly dead in the local area. The birds, a chaffinch (Fringilla coelebs) and a dunnock (Prunella modularis), are similarly sized, non-threatening species that jackdaws commonly encounter. The snakes (b) were rubber toys that mirrored the patterning of two forms of a local snake species: the melanistic and the male wild-type adder (Vipera berus). The sticks (c) were found around the study sites. All stimuli could be hooked up to a hidden motor and moved along the tracks with a remote control when the fishing wire (pictured) was attached to the motor. The tracks for each stimulus are the same size (20 cm).
Figure 1.
Credit: University of Exeter

Dr Alex Thornton, of the Centre for Ecology and Conversation on the University of Exeter’s Penryn Campus in Cornwall, added: “There is still a great deal we do not understand about some of our common bird species.

“Dedicated field experiments, such as ours, can yield insights into their minds, revealing more about how they understand the world.”

The paper, published in the journal Royal Society Open Science, is entitled: “Wild jackdaws are wary of objects that violate expectations of animacy.”

Contacts and sources:     .
University of Exeter

Citation: Wild jackdaws are wary of objects that violate expectations of animacy.
Alison L. Greggor, Guillam E. McIvor, Nicola S. Clayton, Alex Thornton.Royal Society Open Science, 2018; 5 (10): 181070 DOI: 10.1098/rsos.181070   .

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