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Selection of foraging micro-habitat on the Little Egret (Egrette garzatta L.) in the Reserve Tour du Valat Camargue, Southern France

Timmer, J. (1985) Selection of foraging micro-habitat on the Little Egret (Egrette garzatta L.) in the Reserve Tour du Valat Camargue, Southern France. Master's Thesis / Essay, Biology.

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Abstract

The study related in this report was conducted in may through october 1984 in the Camargue, the delta of the river Rhone, on the french Mediterranean coast. It is an alluvial plain, bounded to the North by young tectonic hills, to the East by the main branch of the Rhone and to the South and West by the Mediterranean Sea. A concise overview of the region's geological development and subsequent modification by man is given by Blondel and Isenmann (1981). Insight into the Camargue's importance for the European avifauna is afforded by the same source. All work was done at the biological station Tour du Valat, which is part of the private reserve of the same name, found ed in 1954 by Dr. Lukas Hoffmann. Following the terminology used by Blondel and Isenmann (1981), the reserve is situated in the "fluvio-lacustrine Camargue", a landscape formed by recent fluvial action and transgressions. The station's main effort is directed towards understanding of the ecological functioning of wetland systems, especially those factors limiting the distribution and abundance of Ciconiiform wading birds. One of the remarkable achievements made, which is of great importance to this study, is the successfull attempt to establish a colony of tree-breeding Ardeidae on the grounds of the reserve (Hafner, 1982). The numerically dominant species of Ardeid in the colony, as in the whole of the Camargue, is the Little egret (Egretta garzetta L.). It is certainly the one bird species studied in most detail at Tour du Valat. Detailed descriptions of the bird's feeding ecology and behavior are to be found in Hafner (1977) ,Hafner, Boy and Gory (1982) and Hafner and Britton (1983). The study subject originally aimed at was a continuation of the work done by Harro Reeders (1983) On the prey available to E. garzetta in the marshes of Ligagneau, on the East bank of the Rhone. This, however, proved not to be feasible because in 1984 no birds bred in the colony there and the marshes themselves were largely dry. The aim of the study eventually conducted is the achievement of a general insight in the factors influencing E. garzetta's choice of foraging habitat on a micro patch scale and the interrelationship between these factors. The relevance of such a study is to gain knowledge needed for management of wetlands with regards to E. garzetta's requirements. For that reason, much of the effort was concentrated on the artificial marshes next to the station, which are very close to the Tour du Valat heron colony and therefor of great potential value to the colony at times of high food demand. Moreover, being former rice fields, they allow more precise manipulation of micro habitat than do the natural marshes, thus allowing an experimental approach in the longer run. The improvised nature and limited timespan are not ideally suited to the complexity and novelty of the matter at issue. However, an effort was made to analyze the data available in such a way as to indicate the possibilities of a similar study if conducted on a longer term. The work was done as a project in the biology "Doctoraal" programme at the Rijksuniversiteit Groningen, The Netherlands Supervisors were Prof. Dr. Rudolf Drent, Department of Zoology at the said university, and Dr. Robert Britton and Dr. Heinz Hafner, both of the Station Biologique de la Tour du Valat, Le Sambuc, Camargue, France.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:48
Last Modified: 15 Feb 2018 07:48
URI: http://fse.studenttheses.ub.rug.nl/id/eprint/10206

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