An assessment of the abundance and distribution of the Titicaca Flightless Grebe Rollandia microptera on Lake Titicaca and evaluation of its conservation status

Abstract

Censuses were conducted from 15 June to 6 July and from 15 to 24 October 2003 throughout Lake Titicaca to determine the current distribution and abundance of the Titicaca Flightless Grebe Rollandia microptera. We surveyed 22 of an estimated 25 local population distribution ranges. We defined these as shallow offshore feeding areas in combination with coastal beds of tule-rushes (Schoenoplectus tatora). At this large spatial scale we found variously sized populations of grebes in all 22 of the areas surveyed and a negative correlation between the total area of tule-bed within each area and grebe density. Absolute counts of grebes pooled across all sites produced a total of 2,582 individuals on Lake Titicaca. Given that some sites were either partially surveyed or not surveyed at all we feel that this is an underestimate of the total lake population. Limitations in methodologies used precluded the classification to development stage of approximately 43% of the individuals counted. Among the remaining 57% of the individuals counted we identified 732 mature adults within the total population of Lake Titicaca. When combined with information from other sources and current knowledge of habitat fragmentation our results support the classification of the species in the IUCN Red List as Endangered under criterion C2a. Of 20 local fisherman interviewed on the Bolivian side of Lake Titicaca, 90% confirmed that individuals of Titicaca Flightless Grebe incidentally drown in their fishing nets although responses varied from weekly to monthly estimates of by-catch. Although this study provides the first estimate of the total population of Titicaca Flightless Grebes on Lake Titicaca, a standardized monitoring programme will be required in order (1) to provide a baseline for the interpretation of future population trends in the context of impacts generated by human activities and (2) to aid in future management decisions for the long-term conservation of the species.