Urban Home Range, Dispersal, and Social Behaviors of South Texas Harris’s Hawks

Harris’s Hawks (Parabuteo unicinctus) are a social raptor species that form cooperative groups to hunt, breed, and defend territories. In chapter 2, I evaluated the effectiveness of Apple AirTags, a Bluetooth tracking device, for tracking Harris's Hawks in the Rio Grande Valley, Texas. I estimated a 95% KDE home range of 618 ha for five adults and 694 ha on average for five juveniles. Logistic regression models showed hawks selected for fragmentation in their 95% KDE ranges (P=0.013), and a higher percentage of roads in the 50% KDE ranges (P= 0.04). In chapter 3, I used AirTags to document dispersal and exploratory movements of Harris’s Hawks. I found adults travel significantly longer when making exploratory movements (P=<.01), and hawks fitted with AirTags in areas with higher percent imperviousness were significantly more likely to be right censored from the study (P=0.02). In chapter 4, I analyzed 296 h of behavioral observations on 28 Harris’s Hawk groups and census data on 110 group collected from 2018-2024. I found the average group sizes of the Rio Grande Valley Harris’s Hawks were 2.72 ± 1.0. Perching near (<100m) or with (<5m) other group members was significantly influenced by an interaction between group size, season, and urbanization. During the nonbreeding season, larger groups in urban areas perched together more often, while smaller groups perched together less often. This pattern reversed during the breeding season. Cooperative hunting only consisted of 2% of total observation time and lacked coordination, suggesting that it is not a primary foraging tactic in this population.