Urbanization is a worldwide phenomenon associated with tremendous modifications of natural habitats. Understanding how city dwelling species are affected by those changes is becoming a pressing issue. We presently lack fine scale spatio-temporal studies investigating the impact of urbanization across different life stages and along urbanization gradients. Based on 8 years of monitoring of urban and forest great tits (Parus major), we investigated how city life shapes morphological characteristics at different life stages in the city versus the forest, and within the urban habitat (along naturalness and pedestrian frequency gradients). We found that urban nestlings were significantly smaller than forest ones, but not in lower body condition. Urban breeders showed reduced tarsus, wing and tail lengths compared to forest birds. Within the city, variation in nestling tarsus length and body condition along the naturalness gradient highly depended on the year, with no consistent pattern. For breeders, tarsus length and body condition were positively correlated to the naturalness gradient, although only in 2019 for tarsus, and only in older individuals for body condition. Finally, we found that males had smaller wing lengths in more urbanized parts of the city. These results suggest that urbanization affects morphology early on in development, influencing many morphological attributes. While the mechanisms underlying the urban morphotype remain to be determined, we discuss the potential origins for the documented differences between forest and urban morphotypes, and argue that they most probably result from urban environmental constraints linked to food availability.

城市化是一种与自然栖息地发生巨大变化有关的世界性现象。了解城市居民物种如何受到这些变化的影响正成为一个紧迫的问题。目前，我们缺乏精细的时空研究来研究城市化在不同生活阶段以及沿着城市化梯度的影响。基于对城市和森林大山雀（Parus major），我们研究了城市生活如何塑造城市，森林和城市栖息地（以及自然和行人频率梯度）在不同生命阶段的形态特征。我们发现，城市中的雏鸟比森林中的雏鸟要小得多，但在较低的身体条件下却没有。与森林鸟类相比，城市饲养员的架，翅膀和尾巴长度减少。在城市内部，雏鸟长度和身体状况沿着自然梯度的变化高度依赖于年份，并且没有一致的规律。对于种鸽来说，的长度和身体状况与自然梯度呈正相关，尽管的只在2019年出现，而身体状况仅在年长的个体中出现。最终，我们发现在城市化程度较高的地区，雄性的翅膀长度较小。这些结果表明，城市化在发展的早期就影响了形态，影响了许多形态属性。尽管城市形态类型的潜在机制尚待确定，但我们讨论了森林形态和城市形态之间差异的潜在成因，并认为它们最有可能是由于与食物供应相关的城市环境制约所致。