Kamiński Maciej, Janiszewski Tomasz, Indykiewicz Piotr, Nowakowski Jacek J, Kowalski Jarosław, Dulisz Beata, Minias Piotr
Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Lodz, Banacha 1/3, 90-237, Lodz, Poland.
Department of Biology and Animal Environment, Faculty of Animal Breeding and Biology, UTP University of Science and Technology, Mazowiecka 28, 85-084, Bydgoszcz, Poland.
Front Zool. 2021 Jan 29;18(1):7. doi: 10.1186/s12983-021-00388-y.
Nesting in large aggregations provides several important advantages for colonially breeding birds. However, it also imposes certain costs, associated with facilitated pathogen transmission and social stress. The cost-benefit ratio is not similar for all the birds in a colony and it might be mediated by nest density. To investigate the influence of nest density on cell-mediated immune function and on physiological condition of nestlings, we arranged a cross-fostering experiment in three breeding colonies of black-headed gulls Chroicocephalus ridibundus. First, we exchanged eggs between plots of high and low nest density. Afterwards, we performed phytohaemagglutinin (PHA) skin test and we measured blood haemoglobin concentration in nearly 350 nestlings from experimental (exchanged) and control (non-exchanged) groups.
We found that PHA response was lowest in high nest density control group, indicating that depressed immune function of offspring, likely caused by social stress, can be considered as a cost of colonial breeding. Contrastingly, body condition of nestlings was the poorest in low density control group.
Nestlings hatched and raised in high nest density plots did not have higher blood haemoglobin concentration in comparison to other study groups. Furthermore, they were affected with depressed cell mediated immune function, which is possibly driven by combined maternal (corticosteroid hormones deposited in yolk) and environmental (elevated social stress) effects. These results indicate that breeders from high nest densities do not benefit by rising offspring in better quality, in terms of immune function and body condition, although, in the light of previous studies, high nest densities are occupied by birds of higher individual quality, than low density areas. Our study provides a novel insight into the mechanisms of density-dependence that govern fitness of colonially nesting birds.
大量聚集筑巢为群居繁殖的鸟类带来了几个重要优势。然而，这也带来了一定成本，与病原体传播便利和社会压力相关。对于一个鸟群中的所有鸟类来说，成本效益比并不相同，它可能由巢密度介导。为了研究巢密度对雏鸟细胞介导免疫功能和生理状况的影响，我们在黑头鸥（Chroicocephalus ridibundus）的三个繁殖群体中安排了一项交叉寄养实验。首先，我们在高巢密度区和低巢密度区之间交换了鸟蛋。之后，我们对来自实验（交换）组和对照组（未交换）的近350只雏鸟进行了植物血凝素（PHA）皮肤试验，并测量了它们的血液血红蛋白浓度。
我们发现高巢密度对照组的PHA反应最低，这表明后代免疫功能低下，可能是由社会压力导致的，可被视为群居繁殖的一种成本。相反，低密度对照组雏鸟的身体状况最差。
与其他研究组相比，在高巢密度区孵化和饲养的雏鸟血液血红蛋白浓度并没有更高。此外，它们受到细胞介导免疫功能低下的影响，这可能是由母体（蛋黄中沉积的皮质类固醇激素）和环境（社会压力增加）的综合作用驱动的。这些结果表明，尽管根据先前的研究，高巢密度区被个体质量高于低密度区的鸟类占据，但从免疫功能和身体状况来看，高巢密度区的繁殖者养育出的后代质量并没有更好。我们的研究为控制群居筑巢鸟类适应性的密度依赖性机制提供了新的见解。
