. Bonner zoologische Beiträge : Herausgeber: Zoologisches Forschungsinstitut und Museum Alexander Koenig, Bonn. Biology; Zoology. 38 V. Goutner extermination of their eggs and young ones was applied, partly for 1980 and intensively for 1981: the eggs and nestlings of these birds, found in the study area, were destroyed until the adults left. Observations were made on feeding birds at the feeding grounds in combination with sampling at the same sites for the study of available food. This combination usually gives a good description of the wader diets (Goss-Custard 1973). Quantitative food sampl
. Bonner zoologische Beiträge : Herausgeber: Zoologisches Forschungsinstitut und Museum Alexander Koenig, Bonn. Biology; Zoology. 38 V. Goutner extermination of their eggs and young ones was applied, partly for 1980 and intensively for 1981: the eggs and nestlings of these birds, found in the study area, were destroyed until the adults left. Observations were made on feeding birds at the feeding grounds in combination with sampling at the same sites for the study of available food. This combination usually gives a good description of the wader diets (Goss-Custard 1973). Quantitative food sampling was carried out monthly from April to July 1980, at an important feeding area (7 in Fig. 1). For this purpose, an appropriate landing net was used. The frame base inserted in the substrate was 27 cm long (similar to the width of the avocet bill scooping at feeding, Hamilton 1975). Five samples were taken, scraping the bottom to a depth of 2 cm, along five non-intersecting runs, each of 10 m in length, in area 30 x 30 m and in water of depth 10—20 cm. The material was sieved and the organisms preserved in 10 °/o formalin for Figure 1. Map of the seaward part of the Evros delta. The numbers are references to the text. , Results 1. Population and movements The avocet population changes, for the breeding seasons of 1980 and 1981, are shown in Fig. 2. This population arrived from elsewhere earlier in the season and was not constituted of birds remaining to winter after breeding. Some birds departed after mid-March; most of the remainder gathered on islets 1 and 2 in Drana (Fig. 1). Although breeding activity started in about mid-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Zoologisches Forschungsinstitut und Museum Alexander Koenig. Bonn : Das Forschungsinstitut
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