USGS · 5221669
No abstract available.
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C. A. Mitchell, Donald H. White, T. E. Kaiser. 1981. Reproductive success of great blue herons at Nueces Bay, Corpus Christi, Texas. https://pubs.usgs.gov/publication/5221669
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—Double-Crested Cormorants ( Nannopterum auritum ) and Neotropic Cormorants ( Nannopterum brasilianum ) are thought to be expanding their populations across Texas. This expansion is cause for a concern for both fish stocking and fisheries management in public waters. To examine the historic and current populations and distributions of cormorants, we first evaluated the temporal and spatial patterns of cormorants in Texas. Also, because cormorants are thought to depredate public fisheries, we conducted a small observational field study to assess cormorant presence and behavior at lakes relative to fish stocking. We compiled Christmas Bird Count (CBC) data for both species over a period of fifty years (1970 to 2019). We assessed changes in detection rates at CBCs among years as evidence of population trends during the winter, and changes in distance from the Gulf Coast of CBCs reporting cormorants for evidence of changes in distribution. Our results suggest that winter populations of Double-Crested Cormorants are relatively stable, with no meaningful change in distribution. In contrast, Neotropic Cormorants appear to be both increasing in number and expanding their range. Our assessment of cormorant abundance and behavior at stocked and unstocked lakes from December through February revealed a significant difference in detections among the stocked lakes during pre- and post-stocking but no significant difference among the control lakes.
No abstract available.
The Golden Eagle (Aquila chrysaetos) is a large, apex predator that occurs at low densities, has a long life span, experiences delayed maturity, has low reproductive rates, and has no natural predators (Watson 1997, Kochert et al. 2002). Golden Eagles are sensitive to anthropogenic driven landscape changes in land cover and land use (Hunt 2002, Kochert and Steenhof 2002). Landscape level alterations, such as encroachment of woody vegetation in eagle foraging areas, may result in decreased abundance of suitable prey or interfere with the eagle’s ability to see or capture prey. Currently, there is substantial concern for Golden Eagle conservation due to widespread anthropogenic changes to landscapes across much of the species distribution (U.S. Fish and Wildlife Service 2013). In particular, the rapid expansion of wind energy development has led to heightened concerns for Golden Eagle conservation, as the species is susceptible to mortality through collision with turbines (Hunt 2002, U.S. Fish and Wildlife Service 2013). This has resulted in a recent increase in research to develop a better understanding of the species’ ecology.