Waste not, want not. This certainly applies to the Western scrub jay, a songbird that likes to store its worms or nuts in the ground for later. Although there are always competitors in the offing, it’s not easy to rob a scrub jay.
With the help of clever tricks, like hiding its food in the shade or reburying it, it tries to lead its competitors up the garden path. It does this not only if another bird is watching, but also if the other bird can only hear it. This has been discovered by Gert Stulp, a PhD student at the University of Groningen, during his final-year project for an MSc in Behavioral and Cognitive Neurosciences.
Stulp used three different test situations to prove his hypothesis that scrub jays were also aware of sounds. He used seven Western scrub jays, grey-blue birds that are slightly bigger than a blackbird, native to California. The birds were placed in pairs in spacious cages which could be partitioned down the middle. In the first test, one of the birds was taken out of the cage and the other was able to hide worms in peace, without other birds or people around. It was given the choice between a basin of soft earth and one of aquarium gravel. The contents of the first basin made no noise when the bird dug in it, the second did. In this setup, all seven scrub jays showed a strong preference for the ‘noisy’ basin.
In the second setup, the jays were visited by a competitor. The competitor could watch what the other bird was doing through the see-through partition. This time, too, the birds buried their worms most often in the basin of gravel. In the third setup, the birds were again visited by another jay. This time the partition was not see-through, although they could still hear each other. The birds now buried more food in the basin with the ‘quiet’ earth. This experiment reveals that scrub jays not only use clever tricks when competitors are watching, but also if they are only eavesdropping.
Gert Stulp (1983) gained a BSc in Artificial Intelligence and an MSc (with distinction) in Behavioral and Cognitive Neurosciences at the University of Groningen. The final-year project for his MSc, investigating the ‘hiding behaviour’ of scrub jays, was conducted at the University of Cambridge (UK) and was supervised by experimental psychologist Professor Nicola Clayton and behavioural biologist Simon Verhulst (University of Groningen). Stulp is currently a PhD student in evolutionary psychology. He is researching the relationship between physical characteristics and reproductive strategies in humans.
More information: Gert Stulp: tel. 050-363 6326, e-mail: G.Stulp rug.nl
Western scrub-jays conceal auditory information when competitors canhear but cannot seeGert Stulp, Nathan J. Emery, Simon Verhulst, and Nicola S. ClaytonBiol Lett 2009;5 583-585
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