Développement de la population nicheuse de Héron cendré

Abstract

Le Héron cendré nouvellement installé en Camargue niche surtout dans les marais. La première nidification a été observée en 1964, mais ce n’est qu’à partir de 1968 que l’on peut parler d’une population nicheuse. Les recensements annuels montrent la crois sance constante de cette population (tab. I). Une nidification tardive d’une partie de la population a été observée en 1972 (fig. 1), et l’architecture des nids a été étudiée. Le sud de la France représente une étape migratoire et un lieu d’hivernage très importants pour les populations de Hérons cen drés d’Europe centrale et du Nord. 65,5 % des reprises provenant de la Suisse et de l’Allemagne laissent à penser que la population camarguaise trouverait son origine dans ces deux pays.The Camargue is the breeding ground of eight European breeding species of Ardeidae, Cattle Egret and Grey Heron being the most recent additions to the list. Grey Herons were first discovered breeding in 1964, but only established themselves as a breeding population in 1968. During the intermediate years 1965 - 1967 there was no evidence of further nesting. Annual censuses have shown a steady expansion of the population in the Camargue since 1968 (Table I). Delayed breeding recorded in 1972 was probably caused by exceptional climatic conditions in April and May (Figure 1). The composition of 110 nests has been examined, and six types of nest construction have so far been determined (Table II). No detailed study has yet been made of the prey taken by Grey Herons in the Camargue, but it would appear that fish is the predominant food. The south of France is situated on a direct south-westerly migration route for populations in central and northern Europe, and is an important wintering ground as well as a port of call for passage migrants. Ringing recoveries show that 65.5 % of birds recovered in the south of France between 1921 and 1970 came from Switzerland or Germany. This fact, together with the fact that there have been recoveries from one or other of these two countries in every month of the year, may suggest that the new breeding population in the Camargue is of Swiss or German origin, unless there is some change in the trend of movement of Grey Herons in Europe