Analysis of variation of rainfall in space, time and amounts, and its attendant effect on the ecosystem is vital in arid and semi-arid environments where the resource is scare, highly variable and unpredictable. In this study, we analyse the characteristics of rainfall in the Sultanate of Oman using data recorded between 1977 and 2003. The data is divided into six geomorphic compartments to represent the various topographic regions in Oman. The average yearly rainfall varies from a low of 76.9 mm in the interior region to a high of 181.9 mm in the Dhofar Mountains, with an average of 117.4 mm for the whole country. Mann-Kendall statistics show a negative but insignificant rainfall trends for the datasets. In northern Oman, the main rainfall season occurs between December and April and that accounts for 57.8-82.9% of the annual rainfall. February and March record the highest rainfall accounting for 35.3 to 42% of the yearly rainfall. The Dhofar Mountains and surrounding areas in southern Oman are dominated by the khareef season in July-August, which produces 44.3 to 67.5% of the rainfall in that area. The number of days of light rainfall (<10 mm per day) is the most dominant and accounts for 66-95% of the rain. Rain in excess of 50 mm per day is rare in Oman (0.4 and 2.9%), but when it does occur can result in serious consequences such as flash flooding, human catastrophes and land degradation. Rainfall records indicate that Muscat and surrounding areas are susceptible to tropical cyclones and catastrophic rainfall (>100 mm rainfall per day) approximately every 50 years.
Long-distance migratory species often include multiple breeding populations, with distinct migration routes, wintering areas and annual-cycle timing. Detailed knowledge on population structure and migratory connectivity provides the basis for studies on the evolution of migration strategies and for species conservation. Currently, five subspecies of Bar-tailed Godwits Limosa lapponica have been described. However, with two apparently separate breeding and wintering areas, the taxonomic status of the subspecies L. l. taymyrensis remains unclear. Here we compare taymyrensis Bar-tailed Godwits wintering in the Middle East and West Africa, respectively, with respect to migration behaviour, breeding area, morphology and population genetic differentation in mitochondrial DNA. By tracking 52 individuals from wintering and staging areas over multiple years, we show that Bar-tailed Godwits wintering in the Middle East bred on the northern West-Siberian Plain (n = 19), while birds from West Africa bred further east, mostly on the Taimyr Peninsula (n = 12). The two groups differed significantly in body size and shape, and also in the timing of both northward and southward migrations. However, they were not genetically differentiated, indicating that the phenotypic (i.e. geographical, morphological and phenological) differences arose either very recently or without current reproductive isolation. We conclude that the taymyrensis taxon consists of two distinct
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