summaryTropical forests are disappearing very rapidly, so there is often not time for thorough quantitative studies. It therefore becomes increasingly important to use rapid, reliable and informative methods which are also adjusted to tropical logistic constraints. In this paper we use data from seven dry and semi-humid temperate forest patches in Bolivia and three humid, temperate forests in Ecuador to estimate the efficiency, potential biases and the amount of information obtained by the 20-species list method, which we applied in a rapid assessment of avian species richness. Even when used without any standardizations, 20-species lists produce more data than simple species lists, particularly on the amount of survey effort, the order of species richness, the relative abundances of species and the α-diversity index. This approach precludes comparisons with lists from other sites. However, when applied with standardization of area, altitude and effort, the method is neither easier to use nor superior to point counts (based upon vocalizations) in combination with dawn chorus tape-recordings. In species-poor habitats, it is more appropriate to use lists of fewer species. The method is recommended due to its simplicity and the increased quantity of information produced, but it requires a reasonable amount of observer competence and is therefore unfit for use by people ignorant of local avifaunas.

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Of the world's five flamingo species, the rarest and least known are the Puna Flamingo (Phoenicoparrus jamesi) and the Andean Flamingo (P. andinus). These two species coexist with the more common Chilean Flamingo (Phoenicopterus chilensis) throughout much of their range. We conducted four simultaneous surveys from 1997 to 2001 (two in summer and two in winter) to estimate the distribution and abundance of all three species in Argentina, Bolivia, Chile, and Peru, at a regional scale. Of 224 wetlands surveyed, 179 had flamingos; 63% of these were in the high Andes (above 4000 m), 25% were in the puna (3000 to 4000 m), and the remainder were in lowlands (below 3000 m). Maximum counts were 64 000 Puna Flamingos (summer 1998), 34 000 Andean Flamingos (summer 1997), and 83 000 Chilean Flamingos (winter 1998). In summer, Puna Flamingos congregated at wetlands in the high Andes, with 50% of the population in just three lakes: Colorada, Grande, and Vilama. Andean Flamingos were more uniformly distributed across a broader elevational range (2500 m), and Chilean Flamingos showed a heterogeneous distribution pattern. In winter, all species moved to lower latitudes within the high Andes and to lower altitudes on the central plains of Argentina. The most important nesting wetlands were Colorada, in Bolivia, for the Puna Flamingo, Surire and Atacama, in Chile, for the Andean Flamingo, and Surire for the Chilean Flamingo. We recommend continued monitoring through simultaneous summer surveys, and a conservation strategy that considers the large spatial and temporal scales at which these species operate, including their seasonal migrations.

Desde el año 1996 al 2003, mediante métodos de observación directa, caminatas y capturas con redes niebla, realizamos un inventario y obtuvimos datos sobre la historia natural, gremios tróficos y patrones de migración de la avifauna de la ciudad de La Paz (Bolivia). Registramos 136 especies de aves en 30 localidades de estudio. Las familias más representativas fueron Tyrannidae, Emberizidae y Furnariidae con 19, 16 y 15 especies, respectivamente. Registramos 18 especies de aves acuáticas y dos especies (Tachuris rubrigastra y Phleocryptes melanops) de passeriformes especialistas de totorales. Dos especies de furnáridos (Cranioleuca henricae y Upucerthia harterti) fueron endémicas bolivianas. Detectamos 57 especies en alguna categoría de migración. Movimientos altitudinales inusuales fueron observados para cinco especies (e.g. Pitangus sulphuratus, Pyrocephalus rubinus). Diecinueve especies fueron consideradas raras (e.g. Lesbia nuna, Poospiza boliviana). Los insectívoros y frugi-granívoros son los gremios tróficos mas representativos entre comunidades. El valle de la ciudad de La Paz es una ruta obligatoria para muchas aves migrantes latitudinales (boreales y australes) y altitudinales, que provienen del Altiplano por el oeste y las especies de Yungas por el este.

Since our paper on the efficiency and biases of 20-species lists (Poulsen et al. 1997) went to press we have recognized a further two biases in the method, after discussions with C. Rahbek. We remarked in our paper that the abundance curves were behaving rather strangely and that “the importance of these phenomena needs to be investigated in more detail”. The behaviour may be due to the method setting constraints on the highest possible frequency, namely the number of times a species occurs in 20-species lists. This could affect the calculation of the expected abundances and hence the a-index. Another bias must be the indirect way of determining the relative abundances, ignoring the true number of individuals. A species with many individuals will be given the same relative abundance as a species with very few individuals if both species occur in the same number of 20-species lists. We do not know the importance of these constraints but recommend that the method is not used until the results of a current computer modelling study examining its efficiency (S. Herzog and M. Kessler pers. comm.) are known.