Censussing distribution and population of birds along upland rivers using measured ringing effort: A preliminary study

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Abstract
A standardized ringing scheme was used to assess spatial and temporal trends in populations of Dippers Cinclus cinclus, Kingfishers Alcedo athis and Grey Wagtails Motacilla cinerea along streams in upland Walesduring 1986/7and 1987/8. Catches per unit effort of Dippers and Grey Wagtails on streams with pH >6 did not differ significantly between the two years, whilst an increased catch of Kingfishers in the second year was significant at P = 0.06. Successful breeding by Kingfishers in 1987 might explain the difference. Spatial patterns in the catch per unit effort of Dippers closely reflected population abundance as recorded by another census method, an indication that standardized ringing gave a quantitative estimate of real abundance. Differences in catch rate suggested that Dippers were scarce along acidic streams. Kingfishers catches occurred least along streams of steep slope, but they were also infrequent on streams with suitable slope which had pH <7. Grey Wagtail catches did not vary in relation to slope or altitude, although catch rate in one year could be related to stream pH. These aspects of distribution were consistent with previous studies and further indicate that standardized ringing detected real trends in bird numbers. We conclude that standardized waterways ringing, if undertaken during and after the breeding season, could support the Waterways Bird Survey in a way similar to the relationship between the Constant Effort Scheme and Common Birds Census. The method might also be suitable for collecting data on the distribution and abundance of river birds where demographic information is also required. Some practical and theoretical limitations are discussed, however.