Dissertation/Thesis Abstract

Ecology of Rare and Abundant Raptors on an Oceanic Island: The Sharp-Shinned Hawk and Red-Tailed Hawk in Puerto Rico
by Gallardo, Julio C., Ph.D., Mississippi State University, 2018, 163; 10842547
Abstract (Summary)

Reliable estimates of species abundance, distribution, and population trajectories are critical in conservation and management. However, for many tropical species that information is missing. We conducted Sharp-shinned Hawk (SSHA) searches during the breeding seasons of 2013, 2014, and 2016 in eight montane forest reserves and their adjacent private lands of Puerto Rico. Further, we developed a maximum entropy model (MaxEnt) of the SSHA’s potential distribution using the following environmental variables: aspect, canopy closure, elevation, rainfall, slope, and terrain roughness. Elevation accounted for 89.8% of model fit, predicting the greatest probability of occurrence (> 60%) at elevations above 900 m. The model estimated 0.6%Puerto Rico (56.1 km 2) has the greatest probability of occurrence. We developed a periodic population matrix model to describe the influence of early life stages on population growth of the Red-tailed Hawk (RTHA) in eastern Puerto Rico. Our results suggest that the RTHA population has an average annual population increase of 5%, with rates differing between highlands (λh = 1.05) and 27% lowlands (λl = 1.27). Adult survival was the most important population growth parameter, with more effect in highlands (elasticity = 0.86) than in lowlands (elasticity = 0.53). Sensitivity of λ to changes in nestling survival was greater than for other life-stages (sensitivity lowlands = 0.46, sensitivity highlands = 0.48). I developed an open population N-mixture model to estimate abundance, availability, and detection probability of RTHA in the Luquillo Mountains and western Cordillera Central. The abundance estimates were 0.05 RTHA/ha, with an availability of (&phis;) = ~1 RTHA/per survey point and a detection probability (r) = ~0.25. In Luquillo Mountains, abundance was positively influenced by slope and elevation. In the western Cordillera Central, abundance of RTHA was constant across elevation, slope, and canopy closure. Detection probability decreased with increasing slope and wind conditions and showed a gradual small negative decrease with slope with reduced winds conditions. My findings are a contribution to our knowledge of how population traits and ecological constraints imposed by insular environments are influencing distribution, abundance, and population dynamics of raptors to propose management or conservation schemes.

Indexing (document details)
Advisor: Vilella, Francisco J.
Commitee: Belant, Jerrold L., Leopold, Bruce D., Rush, Scott A.
School: Mississippi State University
Department: Wildlife and Fisheries
School Location: United States -- Mississippi
Source: DAI-B 80/01(E), Dissertation Abstracts International
Subjects: Wildlife Conservation, Ecology, Conservation biology
Keywords: Accipiter striatus venator, Buteo jamaicensis jamaicensis, Caribbean islands, Maximum entropy model, Open population n-mix model, Seasonal population matrix
Publication Number: 10842547
ISBN: 978-0-438-31421-4
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