| Summary: | From the examination of some 654 Ruffs killed in the north of Senegal, we conclude that sex and age ratios fluctuate widely within the year. Sex-ratio has an average of 2.2 females for 1 male between August and January, but are as high as 4.1 females for 1 male in February-March. In April, large numbers of females are still present while males have already left Senegal. Percentages of immature birds also fluctuate within the year : 0% in August, 6% of the females and 22% of the males in September. A maximum of immature birds is reached in October with 50% of the females and 63% of the males. Between December and March, young birds account for about 31% of the females and 41% of the males. Adult females leave Senegal somewhat earlier than young ones and these represent 42% of the females in April. Fluctuations in the composition of Ruff populations may be due either to the stop-over of birds which will fly further south later, or to some kind of segregation based on sex or age in different feeding grounds. (Résumé d'auteur)
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