How Great tits fool their nosy neighbours...
03 Mar 2014
Great tits (Parus major) cover their eggs with loose hair before incubation, but scientists were not quite sure why... until now. The hypothesis supported by research published in the open access journal BMC Evolutionary Biology suggests it might in fact be nosy neighbours!
The tits cover the eggs before they are sensitive to temperature, and they leave them uncovered later on when the eggs are more vulnerable to predators. The birds are clearly hiding their eggs – but what would cause them to go to the trouble?
Pied flycatchers (Ficedula hypoleuca) use the number of eggs great tits have to work out where the most discerning birds choose to live, rather than searching for a good habitat themselves. But for the great tits, having competitors around the place brings down their hard-earned territory.
Scientists wanted to see if the great tits were hiding their eggs to signal that they’re poor quality birds, and therefore worse decision-makers, to discourage undesirable flycatchers from moving in next door. They thought that the great tits would put more effort into hiding their eggs if they thought there were pied flycatchers around, so they observed the nesting behaviour of the great tits when they had placed a pied flycatcher decoy and played their calls, and when they did the same using a non-competing species, a waxwing. By measuring the weight of hair the great tits collected and photographing the nest 24 hours after the experiment, they found that great tits collected more hair in the presence of a pied flycatcher decoy. (Photographs at https://www.dropbox.com/sh/47pz2eww9p6xohw/I_X_1crSgu, please credit Olli Loukola)
Olli Loukola from the University of Oulu says: “We found out that tits put more effort in bringing in new hair to cover the eggs when they thought there was a pied flycatcher around. This provides strong evidence that species being used as information source may develop adaptations against ‘information parasites’”.
The researchers coined the phrase ‘information parasites’ to describe the pied flycatchers, and others who use this tactic - using other species as an information source, rather than going to the effort themselves. In this case, rather than doing a costly search for a good territory (and anyone who has tried househunting knows how time-consuming that can be!), the flycatchers just use information about the quality of great tits in the area to make their decision. They say that this will open up exciting avenues for research into these strategies.
Loukola says: “Our study opens up a previously uncharted territory of co-evolution. Arms race between the information users and sources in different populations may involve a variable series of adaptations and counter-adaptations leading to ever more intricate patterns of social information use”.
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Notes to Editor
Active hiding of social information from information-parasites
Olli J Loukola, Toni Laaksonen, Janne-Tuomas Seppänen and Jukka T Forsman
BMC Evolutionary Biology 2014, 14:32
Article available at the journal website
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