Behavioural Ecology Research Group, Center for Natural Sciences, University of Pannonia, Veszprém, PO Box 1158, 8210, Hungary.
MTA-PE Evolutionary Ecology Research Group, University of Pannonia, Veszprém, PO Box 1158, 8210, Hungary.
Sci Rep. 2021 Dec 17;11(1):24161. doi: 10.1038/s41598-021-03504-4.
Rapidly increasing urbanisation is one of the most significant anthropogenic environmental changes which can affect demographic traits of animal populations, for example resulting in reduced reproductive success. The food limitation hypothesis suggests that the shortage of high-quality nestling food in cities is a major factor responsible for the reduced reproductive performance in insectivorous birds. To study this explanation, we collected data on the parental provisioning behaviour of urban and forest great tits (Parus major) in three years that varied both in caterpillar availability (the main food of great tit nestlings) and in reproductive success of the birds. In all years, urban parents provisioned caterpillars in a smaller proportion to their nestlings, but the total amount of food per nestling (estimated by the volumes of all prey items) did not differ between habitats. In the two years with much lower reproductive success in urban than forest habitats, urban parents had higher provisioning rates, but provided more non-arthropod food and brought smaller prey items than forest parents. In the year with reduced habitat difference in reproductive success, urban parents were able to compensate for the scarcity of caterpillars by provisioning other arthropods rather than non-arthropod food, and by delivering larger preys than in the other years. Specifically, in this latter year, caterpillars provisioned by urban pairs were cc. twice as large as in the other two years, and were similar in size to caterpillars provisioned in the forest broods. These results show that although urban great tit parents can provide the same quantity of food per nestling as forest parents by reducing their brood size and increasing the per capita feeding rates for nestlings, they cannot compensate fully for the scarcity of high-quality preys (caterpillars) in poor years. In some years, however, favourable conditions for urban caterpillar development can greatly reduce food limitation in cities, allowing urban birds to achieve higher reproductive success. We suggest that urban green areas designed and managed in a way to facilitate conditions for phytophagous arthropods could improve habitat quality for urban birds.
快速的城市化是最重要的人为环境变化之一，它可以影响动物种群的人口特征，例如降低繁殖成功率。食物限制假说认为，城市中高质量雏鸟食物的短缺是导致食虫鸟类繁殖性能下降的主要因素。为了研究这个解释，我们在三年的时间里收集了城市和森林大山雀（Parus major）的亲鸟育雏行为数据，这些数据在毛虫供应（大山雀雏鸟的主要食物）和鸟类繁殖成功率方面都有所不同。在所有年份中，城市亲鸟提供的毛虫在其雏鸟中的比例较小，但每个鸟巢雏鸟的总食物量（通过所有猎物的体积估计）在栖息地之间没有差异。在城市栖息地繁殖成功率比森林栖息地低得多的两年中，城市亲鸟的育雏率更高，但提供的非节肢动物食物更多，并且携带的猎物比森林亲鸟小。在繁殖成功率降低的一年，城市亲鸟能够通过提供其他节肢动物而不是非节肢动物食物来补偿毛虫的稀缺，并且通过提供比其他年份更大的猎物来补偿毛虫的稀缺。具体来说，在最后一年，城市亲鸟提供的毛虫大小约为其他两年的两倍，与森林巢中的毛虫大小相似。这些结果表明，尽管城市大山雀亲鸟可以通过减少雏鸟数量和增加每个雏鸟的人均喂食率来为每个雏鸟提供与森林亲鸟相同数量的食物，但它们不能完全补偿劣质年份高质量猎物（毛虫）的稀缺。然而，在某些年份，城市毛虫发育的有利条件可以大大减少城市中的食物限制，使城市鸟类能够实现更高的繁殖成功率。我们建议以促进植食性节肢动物生存条件的方式设计和管理城市绿地，可以改善城市鸟类的栖息地质量。
