Urbanisation constitutes one of the most rapid human-induced environmental changes, developing at the expense of natural and semi-natural habitats. It often implies alterations of many abiotic and biotic factors and contributes to create new environmental conditions, including temperature, food resources, competition and predation. Despite increasing empirical evidence of intra-specific divergence in phenotypic traits (e.g., physiological, behavioural or morphological) between urban and rural individuals, such patterns have often remained disconnected from the underlying mechanisms involved. In the current study, we tested for divergence in functional morphological traits that are related to feeding ecology (i.e., bill morphology, body mass and condition) and/or to the locomotory performance in escaping from predators (i.e., wing, tarsus and tail morphology, body mass and condition) along a chronological gradient of urbanisation (old urban, recent urban and rural areas), using the New Zealand fantail, an endemic insectivorous passerine species. We found divergences in phenotypic traits related to bill morphology along the urban–rural gradient: birds inhabiting the old urban area had stubbier bills (i.e., shorter, deeper and wider bills) than those inhabiting the recent urban and rural areas. We did not detect any difference in locomotion-related morphological traits. Our results suggest the urbanisation-induced alteration in food resources may drive morphological divergence in bird populations. We emphasized the need for mechanistic and experimental studies, with a particular focus on resource-based mechanisms, to identify more precisely the morphological responses of urban populations to changes in food composition, and the resulting implications for communities in urban ecosystems.

城市化是人类引起的最快速的环境变化之一，以牺牲自然和半自然栖息地为代价。它通常意味着许多非生物和生物因素的改变，并有助于创造新的环境条件，包括温度、食物资源、竞争和捕食。尽管越来越多的经验证据表明城市和农村个体之间表型特征（例如，生理、行为或形态）的种内差异，但这种模式往往与所涉及的潜在机制保持脱节。在目前的研究中，我们测试了与摄食生态（即喙形态、体重和状况）和/或逃避捕食者（即翅膀、跗骨和尾巴形态、体重和状况）沿着城市化的时间梯度（旧城区、近代城市和农村地区），使用新西兰扇尾，一种地方性食虫雀形目物种。我们发现沿城乡梯度与喙形态相关的表型特征存在差异：居住在旧城区的鸟类的喙比居住在最近的城市和农村地区的鸟类更粗（即更短、更深、更宽）。我们没有检测到与运动相关的形态特征有任何差异。我们的研究结果表明，城市化引起的食物资源变化可能会导致鸟类种群的形态差异。我们强调需要进行机械和实验研究，特别关注基于资源的机制，