How food supply in rubbish dumps affects the breeding success and offspring mortality of cattle Egret Bubulcus ibis?

Abstract

The objective of this study was to evaluate the effect of food supply in garbage dumps on the reproductive fitness of Cattle Egret Bubulcus ibis and offspring losses. A total of 236 nests were monitored during two distinct periods of 2 years for each: 146 nests during a period without food supply in dumps (1998–1999) and 90 with food supply in dumps (2007–2008). The study was carried out in the colony of El-Kseur in the Lower Soummam Valley (northeast Algeria). For the entire study period, the mean of clutch size, average number of hatched chicks, productivity, and breeding success varied significantly between years (Kruskal–Wallis test: p < .05). Also, the average calculated losses for eggs, chicks, and total offspring vary significantly (Chi2 test: p > .0001). The clutch size and the number of hatched chicks per nest were highest during the period with food supply in garbage dump (respectively: 3.46 ± 0.86; 2.85 ± 1.11), compared to the period when cattle egrets feed in natural or agricultural habitats (3.04 ± 0.87; 2.54 ± 1.03). However, productivity and breeding success were highest during the period without food supply (respectively: 2.11 ± 1.16 fledging’s/nest; 0.70 ± 0.35) than in the period with food supply (1.14 ± 0.91; 0.35 ± 0.30). While egg losses were substantially similar between the two study periods, chick’s mortality (59.9%) and total offspring losses (36.7%) were higher during the period with food supply. The generalized linear mixed model (GLMM) analysis indicated a large negative effect of food supply in dumps on the productivity, on the chick’s losses; and a positive effect on the total offspring losses ( p < .001). Also, feed in dump garbage revealed a significant negative effect on the breeding success linear mixed model (LMM, p = .01). However, no significant effects (GLMM, p > .05) of food supply in dumps were noted on average clutch size, the mean number of hatched chicks per nest, and egg losses.

Age-Specific Demographic Response of a Long-Lived Scavenger Species to Reduction of Organic Matter in a Landfill

“…Yet, feeding in landfills though is hazardous, and may only provide low-quality and polluted food, with the associate risk of exposure to solid waste ingestion (e.g., plastic, rubber, glass or metals) and pathogens [32][33][34][35]. In addition, in some ecological systems and species, feeding on landfills could have a detrimental effect on chick and juvenile survival since individuals of these ages are more susceptible than adults to the abovementioned risks (e.g., [36,37]. Nevertheless, for long-lived scavengers such as vultures, the overall trade-off seems to be positive, as current evidence supports the idea that landfills represent an important food source that may partially support some populations [27,30,[38][39][40].…”