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Ecology of Rare and Abundant Raptors on an Oceanic Island the Sharp-Shinned Hawk and Red-Tailed Hawk in Puerto RicoGallardo, Julio C 10 August 2018 (has links)
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 km2) has the greatest probability of occurrence. We developed a periodic population matrix model to describe 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 (ϕ) = ~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 to 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.
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Red-Tailed Hawk Home Range, Habitat Use, and Activity Patterns in North-Central Puerto RicoLlerandi-Roman, Ivan C 13 May 2006 (has links)
I determined abundance, movement and activity patterns of the Red-tailed Hawk (Buteo jamaicensis jamaicensis, RTHA) in Río Abajo Forest, Puerto Rico and surrounding lands during 2003-2004. Captive-reared Puerto Rican Parrots (Amazona vittata, PRPA) are scheduled for release in Rio Abajo Forest in 2006. Annual density of RTHAs (0.90 RTHAs/km2) was similar to the Caribbean National Forest (CNF; 1.29 RTHAs/ km2). RTHAs annual survival was high (0.89), and birds maintained compressed territories around the Rio Abajo Forest. Home ranges were 91% smaller than estimates reported for CNF, yet similar to those in North America. Approximately 98.3% of RTHA locations occurred outside the Río Abajo Forest boundaries. RTHAs exhibited random macrohabitat use patterns in north-central Puerto Rico. However, within their home ranges, RTHAs selected fragmented habitats with high patch and edge density, and avoided large tracts of dense closed canopy forest. Encounters between RTHAs and PRPAs may increase as parrots venture beyond the boundaries of Rio Abajo Forest.
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