CBC Chat Forum Thread

AuthorTopic: Follow that Stonechat! Why?
Noel Elms Follow that Stonechat! Why?posted at 13/12/2012 19:53:38




At one time or another in our birding lives, many of us will have been told ď if you want to find a Dartford Warbler, first find a StonechatĒ or words to that effect. Taking that advice has enabled many to connect with their first Dartford Warbler but just why there is such a well-proven association between the two species has intrigued me over a number of years. Zamora et al (1992) published the results of a study in Spain suggesting that Dartford Warblers and other gleaner-feeding species followed Stonechats in order to benefit from the Stonechatís greater vigilance leading to the early detection of potential predators. It was also suggested that this association offered no benefit to the Stonechat, could be considered parasitic and just a single follower reduced the Stonechatís feeding success rate by half due to frequent changes of the chatís lookout perch in attempts to lose the follower.

While Dartford Warbler is the most frequently recorded associate of Stonechats, Urquhart (2002) notes that Common Whitethroat, Lesser Whitethroat, Willow Warbler, Meadow Pipit, Tree Pipit, Linnet, Goldfinch, Lesser Redpoll, Yellowhammer, Reed Bunting, Great Tit, Coal Tit, Wren and Dunnock have all been recorded as associates at one time or another. My own observations have recorded the most frequent associates, after Dartford Warbler, as Common Whitethroat, Willow Warbler and Wren in that order with just single records of Yellowhammer and Reed Bunting.

It has been suggested to me in personal conversation that 'bush top' species may well disturb prey into the view of 'low cover' gleaner-feeders below but I wonder how often this would be caused by a bird which tends to remain fairly motionless on an isolated perch for measureable periods. Stonechats don't seem to join in the feeding frenzy that may be taking place below them and continue to watch for much larger prey items either aerial or exposed on the ground (though they will indulge in 'aerial gleaning' i.e. taking smaller prey items from foliage while hovering). May be a 'chicken and egg' situation here but I argue that Stonechats evolved to hunt from an exposed perch thus also evolved to become vigilant if they were to pass on their genes, which leads back to the conclusion of Zamora et al  that birds feeding by intensive foraging are more effective as a group but they need to have a lookout.

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