Pigeon Boldness and Escape Tactics as Early Warning Indicators of Urbanization Processes in a High Altitude Neotropical City

Urbanization drastically alters bird communities, creating an urgent need for practical indicators to monitor species colonization and decline. We investigated whether the boldness of pigeon species—measured by Alert Distance (AD), Flight Initiation Distance (FID), and escape tactics (escape mode and site)—as well as abundance, are related to urban colonization history and ecological opportunities, with the aim of using them in monitoring programs for the colonization or disappearance of birds in cities. In the high-altitude Neotropical city of La Paz, Bolivia, we assessed five pigeon species in 15 urban green spaces, quantifying abundance and escape behaviors and relating them to several environmental metrics. The invasive Rock Pigeon (Columba livia ) exhibited the greatest abundance and boldness, escaping primarily by walking along the ground and preferring impermeable areas. The Eared Dove (Zenaida auriculata) showed intermediate abundance and boldness but a wider habitat uses than the Rock Pigeon. The recently urbanized Spot-winged Pigeon (Patagioenas maculosa) showed the lowest abundance and boldness, predominantly escaping by flying to elevated perches, demonstrating a strong dependence on tree cover. The Bare-faced Ground Dove (Metriopelia ceciliae) was only present in one green area, and the Picui Ground Dove (Columbina picui)was totally absent from our counts, likely indicating a process of decline within the city. Generalized linear mixed models show that body mass did not align with boldness, as suggested by theory; rather, boldness 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.