Showing papers by "The Lodge published in 1988"

Patterns in bird populations along the Omo River in Ethiopia

Abstract: Summary The distribution and abundance of bird species along the Omo River in southwestern Ethiopia were recorded during October and November 1984. The 800 kilometre river ‘transect’ was divided into four sections defined by vegetation, geology, river quality and altitude. Bird populations in each section were treated as temporal communities and census results were analysed for patterns in species richness, taxonomic mix and percentages of ‘widespread’ and ‘local’ species. Results suggest that community gradients exist for bird populations along the river system. In certain bird families, species were added along the gradient. In others, one species seemed to replace another or was correlated with a decrease in abundance of a similar species in the same family. Species diversity and abundance of birds increased along the river. This trend was most notable in the heron and kingfisher families. This preliminary research suggests that bird populations along the Omo River have patterns of distribution and abundance suitable for the study of complex gradients. By conducting species counts along other rivers, a better understanding of this aspect of community ecology may be gained. RESUMEE La distribution et le nombre d'especes d'oiseaux ont ete releves le long de la riviere Omo, dans le sud-ouest de l'Ethiopie, en octobre et novembre 1984. Le secteur de la riviere, long de 800 km, a ete partage en 4 troncons caracterises par la vegetation, la geologie, la qualite de la riviere et l'altitude. Les populations d'oiseaux dans chaque troncon furent considerees comme des communautes temporaires et les resultats des recensements furent etudies aux points de vue de la richesse en especes, de leur melange et du pourcentage d'especes locales et ubiquistes. Les resultats montrer-aient qu'il existe des gradients dans les communautes d'oiseaux le long de la riviere. Dans certaines families d'oiseaux, les especes s'ajoutaient les unes aux autres selon l'endroit. Dans d'autres, une espece semblait en remplacer une autre, out sa presence semblait relieea la diminution d'une espece similaire de la měme famille. La diversite et l'abondance des especes augmentaient au long de la riviere. Cette tendance etait plus sensible dans les families de herons et de martins-pěcheurs. Cette recherche preliminaire suggere que les populations d'oiseaux le long de la riviere Omo ont un schema de distribution et d'abundance interessant pour mener une etude de gradients complexes. Effectuer des comptages sur d'autres rivieres pourrait amener une meilleure comprehension dans l'ecologie des communautes.

An evaluation of current methodology for monitoring changes in the breeding populations of Guillemots Uria aalge

Abstract: The agreement between the population trends in different census plots was studied at 9 Guillemot colonies. At 4 small colonies the entire colony was counted each year so that the trends for the whole colony were known. Marked differences were found among plots at 6 colonies. The implications o this, in terms of extrapolating results from study plots to whole colonies, are discussed. It is concluded that a random method of plot selection is to be preferred when establishing new schemes and that a gradual changeover to random plots should take place at those currently monitored colonies where plots were not originally selected in this way.