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1 September 2012 Asymmetries in Mobbing Behavior Among Nuclear Flockmates
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Tufted Titmice (Baeolophus bicolor) and Carolina Chickadees (Poecile carolinensis) often occur together in mixed species flocks during the non-breeding season and, as nuclear species, often initiate mobbing bouts. We compared the mobbing behavior of Tufted Titmice and Carolina Chickadees and, specifically, their tendency to approach five potential predators. We exposed flocks of chickadees and titmice to study skins of five species of raptors in 2008; raptors were categorized as either low-threat (rarely preying on chickadees or titmice) or high-threat (more likely to prey on chickadees or titmice). We noted the distance of closest approach by titmice and chickadees during trials, and whether a chickadee or titmouse spent more time within 5 m of the raptor. Titmice were more likely to remain within 5 m of both low (p  =  0.0008) and high-threat (p  =  0.0015) raptors. Titmice approached low-threat raptors closer than chickadees (p  =  0.014). There was no difference in the mean distance of closest approach by chickadees and titmice during high-threat trials (p  =  0.34). Titmice generally approached and remained closer to raptors during mobbing bouts than chickadees, possibly because larger titmice (∼ 21 g) are more likely targets of aerial predators than smaller chickadees (∼ 11 g). Titmice may be willing to take greater risks because the potential benefits (reduced risk of predation) are greater if mobbing causes potential predators to leave an area.

Jason R. Courter and Gary Ritchison "Asymmetries in Mobbing Behavior Among Nuclear Flockmates," The Wilson Journal of Ornithology 124(3), (1 September 2012).
Received: 30 September 2011; Accepted: 1 April 2012; Published: 1 September 2012

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