An investigation into the impact of urbanization on home range size, dispersal patterns, and body condition of a kin-structured songbird, the black-crested titmouse (Baeolophus atricristatus)

Abstract Anthropogenic changes to landscapes alter avian behavior and survival. Depending on the life-history and behavioral plasticity of the species, population demographics may shift. To assess the influence of urbanization on avian home range, dispersal patterns, and body condition, we studied a kin-structured passerine, the black-crested titmouse ( Baeolophus atricristatus , BCTI) in urban areas of San Marcos, Texas. Between 2017 and 2019, we color-banded and monitored 36 urban BCTI families to assess factors that influence home range size, and 48 families to examine if mass, sex, or other factors influence dispersal behavior. Urban BCTI home range size was (mean ± SD) 9.11 ± 5.06 ha and was positively correlated with the percentage of impervious surface cover within the home range. Limited dispersal (when juveniles establish a territory adjacent to their father’s) was negatively influenced by fledging date, as well as by sex and mass-rank, indicating heavier male-biased philopatry. We compared body conditions of adult and nestling BCTI from a rural population in San Marcos (2013–2015) to results from this urban study. BCTI nestling and adult body condition did not differ between urban and rural populations nor among year or fledge date, but adult males had a higher body condition in both populations. Overall, urban BCTI construct kin-structured neighborhoods but to a lesser extent than rural populations, indicating that urban environments may disrupt kin-selected behaviors that benefit family flocks.