Avian Species Saturation at a Long-Term Ringing Station

a Never-ending Story?

Abstract

The number of observed species is an index of the relative value of the site to be protected in relation to other sites. To date, most analyses pertaining to species richness have focused on breeding populations and sites. However, avian migratory bottlenecks are no less important for conservation and management purposes. Here we present an example with the use of bird ringing conducted at Eilat, Israel, between the years 1984-2000. We hypothesized that because Israel is located at the juncture of the three continents, we will have new species every year. During the 17 years, 139, 354 individuals of 268 species were ringed. The average of total birds ringed per year was 8197.3 and the average number of species was 113. Of 268 species ringed, 205 (76.5%) were passage migrants, 41 (15.3%) breeding species, and 22 (8.2%) were accidentals. We found a significantly positive correlation (r²=0.857, P=0.014) between the number of species caught each year and the number of operational net days. The number of species recorded annually correlated significantly with the number of individuals caught and the cumulative number of recorded species increased logarithmically throughout the study period. The greatest increase was recorded between the first and second years. Changes in the number of new species decreases non-significantly over the study period. Further, when the difference between the first and the second year is removed this relation is non-significant. It means that chances to catch new species for Eilat are always the same. In conclusion, a ringing station can expect to catch the largest proportion of species within the first three years of activity and then to catch two to three new species annually, i. e., at Eilat we should expect to catch 20 new species during the upcoming decade.