To study the influence of inter- and intra-specific interactions on patterns of ecological segregation in nonbreeding habitat, we used geolocators to track year-round movements of congeneric and ...partially sympatric Thick-billed Murres (Uria lomvia (L., 1758)) and Common Murres (Uria aalge (Pontoppidan, 1763)) from seven Canadian colonies during 2007-2011. Locations from 142 individuals were (i) examined for species- and colony-specific spatiotemporal patterns, (ii) mapped with environmental data, and (iii) used to delineate core wintering areas. Compared with Common Murres, Thick-billed Murres dispersed across a wider range of latitudes and environments, had larger winter ranges, and showed greater variation in seasonal timing of movements. These interspecific differences were consistent at two scales: among colonies spanning a wide latitudinal range and at a sympatric colony. Intraspecifically, nonbreeding ecological segregation was more pronounced among colonies of Thickbilled Murres than of Common Murres: colonies of Thick-billed Murres tended to follow distinct movement patterns and segregate by latitude, whereas colonies of Common Murres segregated very little; moreover, the extent of segregation was more variable among Thick-billed Murres than Common Murres. For Thick-billed Murres, rather than complete divergence of winter ecological niche from Common Murres, we found a "widening" of an overlapping niche. This strategy of increased movement flexibility may enable Thick-billed Murres to mitigate competition both intra- and inter-specifically; we propose this movement strategy may have played a role in species divergence.
We report on historical (1978 to 1982) and more recent (1996 to 2000) variation in the nestling diet of Cassin’s aukletPtychoramphus aleuticusbreeding at Triangle Island (southern) and Frederick ...Island (northern), British Columbia, Canada; these islands are influenced by the California and the Alaska Current ecosystems, respectively. Ocean climate conditions off the British Columbia coast varied tremendously between 1978 and 2000. At both colonies, the nestling diet was composed largely of copepods and euphausiids, with fish contributing substantially in some of the warmer years at Triangle Island. The copepodNeocalanus cristatuswas the single most important prey item at both colonies, and Stage V copepodites dominated in all sampling periods. We used a recently published temperature-dependent phenology equation to estimate the timing of peak biomass ofNeocalanusnear Triangle and Frederick Islands. During warm water years (such as 1996 and the El Niño of 1998), the timing and duration ofN. cristatusavailability in surface waters near Triangle Island was early and limited (mismatched) in contrast to cooler years (such as 1999 and 2000), when this prey was available to birds throughout the breeding season (matched). We argue that Cassin’s auklet nestling diet data reflect the temperature-related timing ofNeocalanusprey availability to seabirds in surface waters. Our results support the argument that inadequate overlap of prey availability and predator breeding (i.e. temporal trophic mismatch) is more likely on Triangle Island, where zooplankton peaks often occur earlier and are narrower, than on Frederick Island, where prey peaks are later and more protracted. Poor reproductive performance is the biological consequence of such trophic mismatch for Cassin’s auklet. If the frequency of El Niño-like events increases and if ocean temperatures rise in the future, we predict an increase in the frequency of trophic mismatch events in the northeast Pacific Ocean.
This paper presents time-series information on the diet composition and breeding performance of rhinoceros aukletCerorhinca monocerataat Triangle Island, British Columbia, Canada, during 15 breeding ...seasons between 1976 and 2001. Three shifts in ocean climate occurred within British Columbia during this period (1976–77, 1989–90, 1998–99), allowing us to evaluate associations between marine environmental conditions and the reproduction of this piscivorous seabird. Lipid-rich Pacific sand lanceAmmodytes hexapteruswas the single most important prey delivered to chicks across years (15 yr avg. 38%; annual range 4 to 86%). Interannual variability was high, but in general breeding performance was strongest when 0+ sand lance predominated chick diets. Other annually important prey taxa included Pacific sauryCololabis saira, juvenile rockfishesSebastesspp., Pacific herringClupea pallasiand juvenile salmonidOncorhynchusspp. The dietary importance of these prey also varied seasonally. Marine environmental conditions (evaluated using sea surface temperatures, SSTs) were clearly associated with reproduction of rhinoceros auklet, as both occurrence of sand lance in the diet and the growth rates of chicks diminished as spring SSTs increased (r = –0.680, p < 0.01, and r = –0.697, p < 0.01, respectively). We hypothesized that recruitment to local sand lance populations was temperature dependent. The strong negative relationship between dietary occurrence of 0+ sand lance and spring SST (r = –0.560, p < 0.05), coupled with the lack of a similar relationship for 1+ sand lance (p > 0.20), was consistent with the temperature-dependent recruitment hypothesis. Our data suggest that SSTs could interact with population age structure to affect the recruitment dynamics of Pacific sand lance. We estimated the annual dietary importance of 0+ sand lance to rhinoceros auklets using spring SST and the importance of 0+ sand lance in the diet the previous year.
We used radio-transmitters to study year-round patterns of colony attendance and foraging trip duration of Shy Albatrosses (Thalassarche cauta) at Albatross Island (1995–1997) and Pedra Branca ...(1997), Tasmania, Australia. Colony activity was largely diurnal, and foraging trip, incubation, and brooding shift durations were relatively short throughout the breeding season, consistent with foraging just a few hundred kilometers from the colonies. Shift durations decreased from 2.9 days early in incubation to an average of 24 hr during brooding. Foraging trip durations were similarly short in the first month postbrooding, but then doubled thereafter to approximately 2 days. Attendance and foraging-trip characteristics were similar between years and at both breeding sites. Both early in incubation and late in chick-rearing, females tended to undertake longer foraging trips than males. There was also an increased probability of failure if females spent as much time on the nest as males during incubation. Outside the breeding season, adults were relatively sedentary. Successful parents from Albatross Island forage off southeast Australia for just nine weeks before returning to spend much of the nonbreeding period attending the colony. The close proximity of the feeding and breeding grounds and near year-round presence of adults at the colony reflects locally favorable foraging conditions. Operating within this environment, Shy Albatrosses exhibit breeding, foraging, and provisioning characteristics that represent an extreme within the Diomedeidae. Ecología de Cría y del Período Invernal de Thalassarche cauta en el Sur de Australia: Patrones Anuales de Presencia en la Colonia y Duración de los Viajes de Forrajeo Resumen. Usamos radio-transmisores para estudiar los patrones anuales de presencia en la colonia y la duración de los viajes de forrajeo de Thalassarche cauta en Albatross Island (1995–1997) y en Pedra Branca (1997), Tasmania, Australia. La actividad de la colonia fue mayormente diurna, y los viajes de forrajeo, la incubación y la duración de los turnos para empollar fueron relativamente cortos durante la estación de cría, lo que es consistente con que las aves forrajean a unos pocos cientos de kilómetros de la colonia. La duración de los turnos disminuyó de 2.9 días al principio de la incubación a un promedio de 24 hr durante el período de empollamiento. La duración de los viajes de forrajeo fue similarmente corta en el primer mes luego del período de cría, pero después se duplicó hasta aproximadamente 2 días. Las características de la presencia en la colonia y de los viajes de forrajeo fueron similares entre años y en ambos sitios de cría. Las hembras tendieron a realizar viajes de forrajeo más prolongados que los machos tanto a principios de la incubación como a fines del período de cría de los pichones. También hubo una probabilidad mayor de fracaso si las hembras permanecieron en los nidos durante el período de incubación la misma cantidad de tiempo que los machos. Fuera del período de cría, los adultos fueron relativamente sedentarios. Los padres exitosos de Albatross Island forrajearon en el mar del sudeste de Australia solamente durante nueve semanas antes de regresar a pasar gran parte del período no reproductivo en la colonia. La proximidad de los sitios de alimentación y de cría y la presencia casi completa a lo largo del año de los adultos en la colonia reflejan condiciones locales favorables de forrajeo. En sintonía con el ambiente, T. cauta presenta características reproductivas, de alimentación y de aprovisionamiento que son extremas entre los Diomedeidae.
We used radio-transmitters to study year-round patterns of colony attendance and foraging trip duration of Shy Albatrosses (Thalassarche cauta) at Albatross Island (1995-1997) and Pedra Branca ...(1997), Tasmania, Australia. Colony activity was largely diurnal, and foraging trip, incubation, and brooding shift durations were relatively short throughout the breeding season, consistent with foraging just a few hundred kilometers from the colonies. Shift durations decreased from 2.9 days early in incubation to an average of 24 hr during brooding. Foraging trip durations were similarly short in the first month postbrooding, but then doubled thereafter to approximately 2 days. Attendance and foraging-trip characteristics were similar between years and at both breeding sites. Both early in incubation and late in chick-rearing, females tended to undertake longer foraging trips than males. There was also an increased probability of failure if females spent as much time on the nest as males during incubation. Outside the breeding season, adults were relatively sedentary. Successful parents from Albatross Island forage off southeast Australia for just nine weeks before returning to spend much of the nonbreeding period attending the colony. The close proximity of the feeding and breeding grounds and near year-round presence of adults at the colony reflects locally favorable foraging conditions. Operating within this environment, Shy Albatrosses exhibit breeding, foraging, and provisioning characteristics that represent an extreme within the Diomedeidae.
Satellite telemetry was used to identify the foraging zones of Shy Albatrosses Diomedea cauta breeding at two sites off Tasmania, Australia (Albatross Island in western Bass Strait and Pedra Branca ...to the south) to assess their level of interaction with longline fisheries. Adult birds from both colonies fed locally both in and outside the breeding season. Breeding birds from Albatross Island foraged over the Australian continental shelf or slope waters off northwest Tasmania, while those from Pedra Branca foraged between the colony and the southeastern edge of the continental shelf. The distances travelled by the birds and the duration of their foraging trips varied during the breeding cycle and tended to decrease as eggs approached hatching. Adults which were tracked near the end of the breeding season (March‐April, n= 7 birds) deserted their chicks prematurely, and while dispersing further than incubating or brooding birds, they remained over the continental shelf and slope waters off southeast Australia. Home range analyses indicated 41% overlap between foraging zones of birds during successive breeding stages. Dispersal during the postbreeding period extended the foraging zones with less overlap between individuals (10% for Albatross Island and 19% for Pedra Branca). The recent contraction of the Japanese Southern Bluefin Tuna longline fishery to the south and east coasts of Tasmania has resulted in extensive overlap with adult Shy Albatrosses from Pedra Branca, but appears to pose a minimal threat to adult birds from Albatross Island. Coupled with the concomitant increase in the Australian domestic tuna longlining industry, adult Shy Albatrosses from southern Tasmania (Pedra Branca and the Mewstone) are vulnerable to incidental capture through out their annual cycle.
The diet of shy albatrosses Thalassarche cauta at Albatross Island, Tasmania, was examined quantitatively from 1995 to 1998. Two main sample types were examined: (1) whole stomach contents from ...chicks that had recently died of natural causes; (2) samples of fresh food delivered to chicks by their parents. Fresh food samples were considered most representative of the overall diet composition and, throughout the study, they were predominated by fish (89% by wet mass). Cephalopods, tunicates and crustaceans contributed 10%, < 0.1% and < 0.1% by wet mass, respectively, to the diet. There was little indication of seasonal or inter-annual variation in prey selection, as the composition of the diet was relatively constant through time. Fish from 16 species or families were identified, however, pelagic schooling Jack mackerel Trachurus declivis and redbait Emmelichthys nitidus together accounted for 57% and 80% (by number) of the fish identified in the stomach and fresh food samples, respectively. Cephalopods from 16 species or families were also identified, and here a single species (Gould's squid Nototodarus gouldi), accounted for 66% and 84% (by number) of the cephalopods identified. Both salps Pyrosoma spp. and crustaceans (largely Australian krill Nyctiphanes australis) contributed little by mass, but they occurred frequently and sometimes they accounted for a significant number of the prey items identified. Aspects of the biology and behaviour of the albatrosses and their main prey species combine to indicate that shy albatrosses have a largely predatory foraging nature. Much of their prey can be captured live, at the surface, during the day.
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