干旱区生态环境知识资源中心

Analysis of the mean date of first captures and median arrival dates of spring migration for 34 species of birds at Eilat, Israel, revealed that the earlier a species migrates through Eilat, the greater is the inter-annual variation in the total time of its passage. Birds arrive during spring migration in Eilat in four structured and independent waves. The annual fluctuation in the initial arrival dates (initial capture dates) and median dates (median date of all captures), not including recaptures, did not depend on the length of the migratory route. This implies that migrants crossing the Sahara desert depart from their winter quarters on different Julian days in different years. We suggest that negative correlations between the median date of the spring migration of early and late migrants depends upon the easterly (Hamsin) wind period. Moreover, we believe that the phenology of all birds during spring migration in Eilat is possibly also determined by external factors such as weather conditions on the African continent or global climatic processes in the Northern hemisphere. Orphean Warblers (Sylvia hortensis) show a strong negative correlation (rs = -0.502) of initial capture date with calendar years, whereas other species such as Barred Warbler (S. nisoria; rs = -0.391) and Spotted Flycatcher (Muscicapa striata; rs = -0.398) display an insignificant trend. The Dead Sea Sparrow (Passer moabiticus) and Red-Backed Shrike (Lanius collurio) are positively correlated regarding initial arrival date and medians of spring migration.