Rice fields and waterbirds are an example of a synergy that can occur between agriculture and conservation. This connection is especially relevant during the farming period, when nesting waterbirds need to obtain resources to cover their energy requirements and those of their chicks in rice fields. However, new farming techniques may potentially put fulfilling this role at risk. Studies on how species use rice fields to feed during this critical period are essential to understand waterbird population dynamics and to optimize conservation measures. At present, several species of colonial birds in l’Albufera de València (Spain) that depend on trophic resources available in rice fields have decling populations and decreases in productivity. We therefore assessed trophic niche segregation in the diet of chicks of a waterbird community composed of seven species through stable isotope analyses of carbon (δ¹³C) and nitrogen (δ¹⁵N) obtained from chick blood and tissue samples of potential prey. According to trophic niche widths, chicks of Black-headed Gull Chroicocephalus ridibundus and Gull-billed Tern Gelochelidon nilotica showed a similar diet, although Gull-billed Tern had a major trophic specialization. The Western Cattle Egret Bubulcus ibis fed its chicks in a wider range of different habitats, with organisms located at the base of the food chain and with a greater importance of terrestrial prey than other species. Conversely, the Glossy Ibis Plegadis falcinellus had a more differentiated diet, mostly in freshwater habitats and mainly consuming odonates. Grey Heron Ardea cinerea, Little Egret Egretta garzetta and Squacco Heron Ardeola ralloides showed overlap between their niches, largely explained by the presence and abundance of cyprinid fish and odonates in their diets. Our results suggest a less important role than expected of Red-swamp Crayfish Procambarus clarkii, and a more important role of odonates despite being a less energy-rich prey. In conclusion, the diet of generalistic species of waterbirds in this study suggests that their trophic niches can overlap when relative prey abundance is high.

中文翻译：

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使用稳定同位素解开地中海湿地群落水鸟的饮食组成和生态位分离

稻田和水鸟是农业和保护之间可能发生协同作用的一个例子。这种联系在农耕期间尤为重要，此时筑巢的水鸟需要获取资源来满足它们和稻田中雏鸟的能量需求。然而，新的农业技术可能会使履行这一角色面临风险。研究物种在这一关键时期如何利用稻田觅食对于了解水鸟种群动态和优化保护措施至关重要。目前，l'Albufera de València（西班牙）依赖稻田中可用营养资源的几种殖民地鸟类种群数量减少，生产力下降。¹³ C) 和氮 (δ ¹⁵ N) 从潜在猎物的小鸡血液和组织样本中获得。根据营养生态位宽度，黑头鸥Chroicocephalusridibundus和鸥嘴燕鸥Gelochelidon nilotica 的雏鸟表现出相似的饮食，尽管鸥嘴燕鸥具有主要的营养专长。Western Cattle Egret Bubulcus ibis在更广泛的不同栖息地喂养雏鸟，这些生物位于食物链的底部，与其他物种相比，陆地猎物的重要性更高。相反，Glossy Ibis Plegadis falcinellus 的饮食更加分化，主要生活在淡水栖息地，主要食用齿类。灰鹭Ardea cinerea, Little Egret Egretta garzetta和 Squacco Heron Ardeola ralloides在它们的生态位之间表现出重叠，这主要是由于它们饮食中存在和丰富的鲤科鱼类和 odonates。我们的研究结果表明，红沼泽小龙虾Procambarus clarkii 的作用不如预期的重要，而尽管是一种能量较少的猎物，但齿科动物的作用更重要。总之，本研究中一般水鸟物种的饮食表明，当相对猎物丰度高时，它们的营养生态位可以重叠。