Gómez-López Guillermo, Martínez Félix, Sanz-Aguilar Ana, Carrete Martina, Blanco Guillermo
Department of Evolutionary Ecology, National Museum of Natural Sciences (MNCN), Spanish National Research Council (CSIC), José Gutiérrez Abascal 2, 28006 Madrid, Spain.
Escuela Internacional de Doctorado, Universidad Rey Juan Carlos (URJC), Tulipán s/n, 28933 Móstoles, Madrid, Spain.
Curr Zool. 2022 Jun 11;69(3):227-235. doi: 10.1093/cz/zoac046. eCollection 2023 Jun.
Variation in offspring sex ratios is a central topic in animal demography and population dynamics. Most studies have focused on bird species with marked sexual dimorphism and multiple-nestling broods, where the offspring sex ratio is often biased due to different individual or environmental variables. However, biases in offspring sex ratios have been far less investigated in monomorphic and single-egg laying species, and few studies have evaluated long-term and large-scale variations in the sex ratio of nestling vultures. Here, we explore individual and environmental factors potentially affecting the secondary sex ratio of the monomorphic griffon vulture . We used information collected at three breeding nuclei from central Spain over a 30-year period (1990-2020) to analyse the effects of nestling age, parental age, breeding phenology, conspecific density, population reproductive parameters, and spatial and temporal variability on nestling sex. Sex ratio did not differ from parity either at the population or the nuclei level. No significant between-year differences were detected, even under highly changing conditions of food availability associated with the mad-cow crisis. We found that tree nesting breeders tend to have more sons than daughters, but as this nesting behavior is rare and we consequently have a small sample size, this issue would require additional examination. Whereas further research is needed to assess the potential effect of breeder identity on nestling sex ratio, this study contributes to understanding the basic ecology and population dynamics of Griffon Vultures, a long-lived species with deferred maturity and low fecundity, whose minor deviations in the offspring sex ratio might imply major changes at the population level.
后代性别比例的变化是动物种群统计学和种群动态学的核心主题。大多数研究都集中在具有明显两性异形和多雏鸟窝的鸟类物种上，在这些物种中，由于个体或环境变量的不同，后代性别比例往往存在偏差。然而，在单态和单卵产卵物种中，后代性别比例的偏差研究得要少得多，很少有研究评估雏鸟秃鹫性别比例的长期和大规模变化。在这里，我们探讨了可能影响单态兀鹫后代第二性别比例的个体和环境因素。我们利用在30年期间（1990 - 2020年）从西班牙中部三个繁殖核心收集的信息，分析了雏鸟年龄、亲代年龄、繁殖物候、同种密度、种群繁殖参数以及空间和时间变异性对雏鸟性别的影响。在种群或繁殖核心水平上，性别比例与胎次均无差异。即使在与疯牛病危机相关的食物供应高度变化的条件下，也未检测到显著的年份间差异。我们发现，在树上筑巢的繁殖者往往儿子比女儿多，但由于这种筑巢行为很少见，因此我们的样本量较小，这个问题需要进一步研究。虽然需要进一步研究来评估繁殖者身份对雏鸟性别比例的潜在影响，但这项研究有助于理解兀鹫的基本生态学和种群动态，兀鹫是一种成熟延迟、繁殖力低的长寿物种，其后代性别比例的微小偏差可能意味着种群水平的重大变化。
