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Until the advent of electronic tagging technology, the inherent difficulty of studying swift and powerful marine animals made ecological information about sharks of the family Lamnidae difficult to obtain. Here we report the tracking of movements of white sharks by using pop-up satellite archival tags, which reveal that their migratory movements, depth and ambient thermal ranges are wider than was previously thought.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. SUMMARY(1) We studied age-specific breeding success of western gulls (Larus occidentalis) on south-east Farallon Island, California in relation to annual variation in food abundance, 1983-89. We assessed yearly reproductive performance on the basis of clutch initiation date, clutch size, hatching and fledging success, and the number of chicks raised to independence. We categorized age of parent into three groups: young, middle-aged and old.(2) Mature birds initiated breeding earlier and laid larger clutches; they fledged more chicks than younger birds as a result of hatching a greater proportion of their eggs and fledging a greater proportion of their hatched chicks. The oldest birds generally did not differ from middle-aged in breeding performance. The difference in reproductive performance between young and mature birds was most apparent during years when food availability was reduced.(3) Timing of breeding influenced reproductive performance independently of parental age; reproductive performance decreased throughout the breeding season. Within-season reductions in reproductive performance were most apparent for young breeders and individuals with small clutches or broods.(4) Breeding performance varied significantly among years independently of age of the study animals. Food availability accounted for part of the yearly variation in breeding success.(5) We suggest that clutch/brood size reflects individual quality. Age-specific breeding success in western gulls is best explained by previous breeding experience and individual quality. Age and reproduction in gulls & Parker 1975). The trade-off between current and future reproductive success has been the focus of much detailed research. However, few studies have provided unequivocal support for increasing reproductive effort with age because other variables intercorrelated with parental age may directly influence reproductive success without invoking an agespecific life-history strategy (Nur 1984; Reid 1988). Age-specific breeding performance may improve with previous breeding experience and foraging efficiency, or be a statistical artefact of individual variation if only high quality animals survive to the oldest ageclasses (see Coulson & Porter 1985; Coulson & Thomas 1985a).Much of the literature concerning age-specific reproductive performance is based upon colonially nesting seabirds relative effects of parental age are not well understood due to confounding by timing of breeding and yearly resource abundance.We studied age-specific reproductive performance in relation to food availability from 1983 t...

All birds have fundamentally similar patterns of plumage succession. Thus Humphrey and Parkes (1959) proposed a system of nomenclature (the H-P system), based on homologies, that has become standard for molt studies in North America. However, presumably analogous similarities in pattern between first basic and definitive basic plumages have obscured homologies. Many plumages conventionally known as “first basic” are better considered as novel first-cycle plumages that lack homologous counterparts in subsequent cycles. Consequently, current nomenclature does not consistently reflect between-species homologies. Howell and Corben (2000b) proposed that traditional juvenal plumage can be considered an unambiguous starting point for a terminology that better reflects presumed homologies in basic plumages; alternate and other nonbasic plumages may not necessarily be homologous between species. Four underlying strategies of increasing complexity incorporate all known patterns of plumage succession: the Simple Basic Strategy, the Complex Basic Strategy, the Simple Alternate Strategy, and the Complex Alternate Strategy. We review inconsistency in the H-P system; explain the four underlying strategies; and discuss how one can identify homologies (if any) between plumages in first and subsequent cycles and among taxa. Many species have novel plumages added into their first plumage cycle; we argue that existing terminology for these plumages is unsuitable and we term them formative plumages attained by preformative molts. Finally, we provide examples of how this modified H-P system can be applied to diverse taxa of birds while reflecting the homology underlying all basic plumage cycles. Our revision validates the flexibility and utility of the H-P system.El Problema del Primer Plumaje Básico: Una Revisión de las Homologías de la Muda y del PlumajeResumen. Todas las aves tienen patrones de sucesión del plumaje fundamentalmente similares. De este modo, Humphrey y Parkes (1959) propusieron un sistema de nomenclatura (el sistema H-P), basado en homologías, el cual ha sido de uso común en estudios de muda de plumaje en Norte América. Sin embargo, supuestas similitudes análogas entre el primer plumaje básico y el plumaje definitivo básico han confundido las homologías. Muchos plumajes convencionalmente conocidos como “primer básico” son considerados mejor como plumajes originales del primer ciclo que carecen de contrapartes homólogas en los ciclos siguientes. Consecuentemente, la nomenclatura actual no refleja las homologías entre especies. Howell y Corben (2000b) propusieron que el tradicional plumaje juvenil puede ser considerado como un punto de partida inequívoco para una terminología que refleje mejor las homologías presuntas en los plumajes básicos; los plumajes alternos y otros plumajes no básicos pudieran no ser homólogos entre especies. Cuatro estrategias de creciente complejidad incorporan todos los patrones conocidos de sucesión de plumajes: La Estrategia Básica Simple, La Estrategia Básica Compleja, La Estrategia Alterna Simple, y La Estrategia Alterna Compleja. Examinamos ciertas inconsistencias en el sistema H-P; explicamos las cuatro estrategias subyacentes, y discutimos cómo se pueden identificar homologías (cuando existen) entre los plumajes del primer ciclo y de los ciclos siguientes, y entre taxa diferentes. Muchas especies tienen plumajes originales adicionales en su primer ciclo de plumaje; sostenemos que la terminología actual para estos plumajes es inadecuada y los denominamos como plumajes formativos, logrados por mudas preformativas. Finalmente, damos ejemplos de como este sistema H-P modificado puede ser aplicado a diversos tipos de aves y al mismo tiempo reflejar la homología subyacente a todos los ciclos de plumajes básicos. Nuestra revisión valida la flexibilidad y utilidad del sistema H-P.

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Three time series of pelagic bird abundance collected in disparate portions of the California Current reveal a 90% decline in Sooty Shearwater (Puffinus griseus) abundance between 1987 and 1994. This decline is negatively correlated with a concurrent rise in sea‐surface temperatures; Sooty Shearwaters have declined while sea temperatures have risen. There is a nine‐month lag in the response by shearwaters to changing temperatures. The geographical scale of our study demonstrates that the decline of Sooty Shearwaters is not a localized phenomenon, nor can it be ascribed to a short‐term distributional shift. The Sooty Shearwater is the numerically dominant species of the California Current System (CCS) in summer (austral winter), with an estimated population in the late 1970s of 5 million individuals. If the observed warming of the waters of the California Current System is an irreversible manifestation of a changing global climate, then the impact upon Sooty Shearwater populations seems likely to be profound.