Does the Urban Environment Act as a Filter on the Individual Quality of Birds?

Phenotypic divergences of birds are common between urban and natural habitats can result from different selective pressures or maladaptation to the city. No uniform patterns were observed, especially concerning markers bird health, such as, for example, telomere length. Telomeres involved in maintaining genome integrity naturally shorten with age, but environmental stressors accelerate their attrition. Thus, length be an indicator individual quality. Some studies showed that breeders had longer telomeres than forest individuals. Two hypotheses explain this result: (1) younger forests breeders, (2) cities act as a filter on individuals only high-quality successfully reproduce. In context, we compared age category (molting pattern) morphological physiological characteristics Great Tits before during breeding. differences body condition observed. However, smaller shorter captured winter. Urban birds, These results highlight potentially favor birds. decrease winter reproduction city suggest higher cost forest.