Les chevaliers combattants Philomachus pugnax L. dans le Nord du Sénégal : composition des populations par sexe et classes d'âge

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