Pigeon Species Boldness as a Tool for Monitoring Urbanization Processes

Urbanization drastically alters bird communities, creating an urgent need for practical in-dicators to monitor species colonization and decline. We investigated whether avian boldness, measured by Alert Distance (AD), Flight Initiation Distance (FID), and escape tactics such as escape mode and site, is better related to urban colonization history and ecological opportunities than morphological variables such as body mass. In the high-altitude Neotropical city of La Paz, Bolivia, we assessed five pigeon species in 15 ur-ban green spaces, quantifying abundance and escape behaviors and relating them to sev-eral environmental metrics. The invasive Rock Pigeon exhibited the greatest abundance and boldness, escaping primarily by walking to the ground and preferring impermeable areas. The Eared Dove showed intermediate abundance and boldness but a wider habitat uses than the Rock Pigeon. The recently urbanized Spot-winged Pigeon showed the lowest abundance and boldness, predominantly escaping by flying to elevated perches, demon-strating a strong dependence on tree cover. The Bare-faced Ground Dove was only present in one green area, indicating a process of disappearance in the city, and the Picui Ground Dove was totally absent from our counts, probably due to physiological limitations. Gen-eralized linear models confirmed that body mass did not explain AD or FID, rather, bold-ness was more related to the timing and ecological opportunities for urban colonization in relation to environmental factors. Combining behavioral metrics (AD, FID and escape mode) with population censuses offers a low-cost, highly sensitive tool for monitoring urban wildlife dynamics and guiding biodiversity-friendly urban planning.