Leg flags versus colour rings: a comparison of marking methods using a small shorebird, the St Helena Wirebird

To understand the behaviour, life-history and demography of animals it is often necessary to mark individuals in some way to tell them apart from conspecifics. It is important to choose the most effective method of doing this as it will allow the number of study animals to be minimized. Plastic colour rings have been used to mark birds for many years, and more recently, leg flags engraved with numbers or letters have become available. Engraved leg flags may have some advantages over colour rings; however, we are not aware of any comparison of the effectiveness of these two techniques. As part of a conservation-focused demography project, St Helena Wirebirds, Charadrius sanctaehelenae, were either marked with one leg flag or three colour rings, and the ease of resighting was investigated in the natural habitat of the plovers. Results showed that there was a lower probability of correctly identifying the engraved numbers on the leg flag than the combination of colour rings, when controlling for confounding factors. Both the distance from the subject to the observer and the duration of the trial reduced the probability of correct identification. Although these results may differ between species and habitats, it is anticipated that they will help researchers to select appropriate marking techniques.