Parents may adapt their offspring sex ratio in response to their own phenotype and environmental conditions. The most significant causes for adaptive sex-ratio variation might express themselves as different distributions of fitness components between sexes along a given variable. Several causes for differential sex allocation in raptors with reversed sexual size dimorphism have been suggested....

Little is known about the magnitude of the effects of lead shot ingestion alone or combined with poisons (e.g., in bait or seeds/granules containing pesticides) on population size, growth, and extinction of non-waterbird avian species that ingest these substances. We used population models to create example scenarios demonstrating how changes in these parameters might affect three susceptible s...

Gastric motility in the Great Horned Owl (Bubo virginianus) has been the subject of few previous studies. A gastroduodenal contraction sequence beginning with the glandular stomach (proventriculus), then the muscular stomach (gizzard), and lastly the duodenum was observed radiographically by Reed and Reed (1928) and Kostuch and Duke (1975). Contractions arise near the isthmus in the muscular st...

Structural elements for breeding such as nests are key resources for the conservation of bird populations. This is especially true when structural elements require a specific and restricted habitat, or if the construction of nests is costly in time and energy. The availability of nesting-platforms is influenced by nest creation and persistence. In a Mediterranean forest in southeastern Spain, n...

Raptor biologists have successfully used backpack-type harnesses to attach transmitters a wide range of raptor species for research. As part graduate research project with Gray Hawks (Buteo plagiatus) in south Texas, we attached 58 individuals and experienced problems seven birds removing the all females covering solar panels OrniTrack-10 GPS-GSM transmitters, preventing them from functioning p...