Abstract:
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Urbanization represents a multi-dimensional ecological ‘filter’ for birds determined by a myriad of variables that can change
over time. Birds colonising an urban system or staying in a habitat that has been recently urbanised need to overcome both
the extrinsic (e.g. food predictability, human activities, and inter-specific interaction) and intrinsic filter variables, ranging
from genetic to behavioural changes and/or adjustments. An increasing body of knowledge has identified the behavioural
component as crucial for individuals facing the spatiotemporal dynamic urban filters, often after other traits and mechanisms
have played their role. Through both developmental (i.e. variability in the expression of genes during ontogeny) and
activation plasticity (i.e. alteration of behaviour as a result of individual experience), studies have shown that the identification
of cues in novel systems—often determined by extrinsic factors—and learning processes, among other factors, have
important impacts on decision-making and innovation. The latter are crucial behavioural traits for thriving in urban settings.
Thus, we propose an integrative mechanistic framework based on the process experienced by birds who reach a city
and manage to persist in the novel system (becoming urban ‘utilisers’) or those that dwell in an urbanised region who
increase their fitness through behavioural responses and adaptations, leading to population persistence (becoming
‘dwellers’). Future field research efforts ought not only to widen the range of focal species, regions, and temporal scales of
studies, but also to assess behavioural responses in highly urbanised settings, given that much of our knowledge comes
from studies performed in urban greenspaces. Additionally, experimental studies are needed to complement the evidence
from field research and to determine causal links. |