The effects of colony size interacting with extra food supply on the breeding success of the White Stork (Ciconia ciconia)
Djerdali, Sofía | Guerrero Casado, José | Sánchez Tortosa, Francisco
In the present study, we evaluated the effect of distance to food from rubbish dumps and colony size on White Stork breeding success. Waste from poultry farms is expanding in the study area and is commonly used by the White Stork as a new food resource, which may explain the increase in the number of breeding Storks in the region. The study was carried out at 24 sites, including 88 different colonies of White Stork in northern Algeria, Sétif (36°09′N, 05°26′E; 900 m.a.s.l.); over a 4-year period (2002–2005) with considerable variation in rainfall. Nests were monitored at different distances from 30 rubbish dumps emanating largely from chicken farms. Results of the General Linear Mixed Models (GLMM) showed that breeding success of White Stork was dependent upon distance to dumps, recording the highest values in nests close to these places with food supply. There was a highly significant interaction between the year and the distance to the rubbish dumps. That is, reproductive success was higher when there was extra food in all years except in 2002, which could be due to the very low rainfall during spring 2002. Also, we found a significant interaction between colony size and distance to a rubbish dump. Results suggest that White Stork breeding success was also affected by natural food resources, since bigger colonies may deplete natural prey sooner, which is more evident in dry years.
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