Low incidence of leg and foot injuries in colour-ringed marsh tits Poecile palustris

Marking birds with individually identifiable metal leg-rings (bands) is a common research tool, and the additional use of plastic colour-rings has facilitated numerous studies of bird ecology, yet there is limited information for the impact of these methods on individuals and populations. Despite generally being considered to have a negligible effect upon birds, recent literature shows that leg rings can cause injuries to some passerines. This creates an ethical problem and may also bias research results by influencing individual behaviour and survival. The incidence of leg injuries was monitored on colour-ringed and unringed Marsh Tits over 12 years. The overall incidence of permanent injury did not differ between ringed and unringed birds, but six out of 404 colour-ringed birds (1.5%) carried a leg or foot injury, which was significantly greater than the background rate (0.2%) among 515 unringed birds. However, some injuries on ringed birds were temporary and/or may have been unrelated to the rings, although one fatality and two serious injuries were recorded, probably resulting from colour-rings becoming caught on thorns or other objects. Although ring-related injuries were very rare, it is recommended that ringers studying Marsh Tits try to minimise the number of rings on each leg.