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We studied the breeding success of resident Bald Eagles (Haliaeetus leucocephalus) over a 20-year period along the Pit River drainage in northern California. In 258 nesting attempts at 10 intensively studied nesting territories, 0.31 to 1.65 young were produced per year per occupied territory (mean = 0.97), with average nesting success of 62%. Nineteen individually banded breeding adult Bald Eagles produced from zero to 36 young during their lifetimes, and birds remained on their territories for 1-16 years following capture as adults. We calculated a 90% annual survival rate for breeding adults from our sample of 19 birds, with longevity of one banded eagle at 22 years. Eagles that bred on a territory for a greater number of years did not produce a greater number of young annually on average than other breeding birds. Larger males, as evidenced by body mass at capture, produced significantly more young over their lifetimes than smaller males. This same relationship did not hold for females, however. Seven banded pairs of adults remained together on their territories for 3-15 years. Reproduction decreased significantly following replacement of a breeding adult on a territory, and this effect continued for 2-3 years following replacement. Key words: Bald Eagle, Haliaeetus leucocephalus, lifetime reproductive success, longevity, mate fidelity, reproductive ecology, survival. Estudiamos el exito de crianza de individuos de Haliaeetus leucocephalus que residen en los alrededores del Rio Pitt en el Norte de California durante un periodo de mas de 20 anos. De 258 intentos de anidacion evaluados en diez territorios de anidamiento estudiados intensamente, se produjeron anualmente 0.31 a 1.65 crias por territorio ocupado (media = 0.97), con una tasa promedio de exito de 62%. Diez y nueve aguilas individualmente anilladas engendraron de cero a 36 crias a lo largo de toda su vida, y dichas aves permanecieron en sus territorios de uno a 16 anos despues de haber sido capturadas ya como adultos. Calculamos una tasa de supervivencia anual de adultos de 90% a partir de una muestra de 19 aves, que incluyo un aguila anillada cuya longevidad fue de 22 anos. Las aguilas que criaron en un mismo territorio durante mucho tiempo no produjeron anualmente un promedio mayor de crias que otros adultos. Los machos mas grandes, evidenciados por el peso corporal en el momento de su captura, produjeron significativamente mas crias durante toda su vida que los machos mas pequenos. Sin embargo, esta misma relacion no tuvo lugar para las hembras. Siete parejas anilladas de adultos permanecieron juntos en sus territorios de tres a 15 anos. La reproduccion decrecio significativamente despues del reemplazo de un adulto de crianza de un territorio, y este efecto continuo durante 2 a 3 anos despues de dicho reemplazo.

The article discusses a amphibian population dynamics study regarding identification of Foothill Yellow-Legged Frogs, Rana Boylii, which are found in streams and rivers in California and Oregon, using photographic pattern recognition. It reveals that males Rana frogs are identified by their swollen and darkened thumb base or nuptial pads. It also mentions that use of chin mottling patterns were studied during examining mating strategy and movement ecology in Rana.