Reproductive stages effects on nest morphology and reproductive success of Yellow-legged Gull on Oued Charef Dam Island, Northeast Algeria

Understanding how reproductive stages influence avian reproduction is essential for predicting species’ responses to environmental variability. While much research has focused on temperate ecosystems, studies in semi-arid and Mediterranean environments remain scarce. In these regions, reproductive stages defined by key environmental conditions such as rainfall patterns and food availability are often less predictable and more strongly influenced by resource availability than by temperature. This study presents the first in-depth investigation of how reproductive stages affect nest morphology and reproductive success in a Yellow-legged Gull population inhabiting the small island of Oued Charef Dam, northeastern Algeria. Reproductive activity was monitored across four distinct stages: early breeding, mid-breeding I, mid-breeding II, and late breeding. Key nest morphological traits (external and internal diameters, nest depth) and reproductive parameters (egg size, volume, and weight; clutch size; hatching and breeding success) were measured throughout these stages. My findings reveal significant variation in nearly all traits across reproductive stages, with the lowest values observed during early breeding and the highest reproductive investment occurring in late breeding. Clutch size was the only trait that did not vary significantly. Multivariate analyses, including Principal Component Analysis (PCA) and Redundancy Analysis (RDA), showed that reproductive stages explain a substantial proportion of the variation in both nest structure and reproductive traits, highlighting a gradient of increasing reproductive investment from early to late stages. These results underscore the importance of breeding stage timing in shaping reproductive strategies in unpredictable environments and provide valuable baseline data for an under-studied region. In the context of climate change and increasing environmental uncertainty, understanding how birds adjust their breeding investment across reproductive stages is critical for informing future conservation strategies.