Browsing by Author "Phalan, Ben"
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- Acoustic monitoring of anurans and birds in tropical biomesPublication . Barros De Araújo, Carlos; Lima, Marcos Robalinho; Albuquerque, P.; Alquezar, Renata D.; Barreiros, M.; Jardim, M.; Gangenova, E.; Machado, R. B.; Phalan, Ben; Roos, A. L; Rosa, G. L. M.; Saturnino, N.; Simões, Cássio Rachid; Torres, I. M. D.; Varela, Diego; Zurano, Juan Pablo; Marques, P. A. M.; Dos Anjos, LuizPassive acoustic monitoring (PAM) is increasingly popular in ecological research, but recording and analyzing large amounts of data is still a critical bottleneck for the long-term monitoring of multiple species. We evaluated how temporal and spatial sampling effort affects species diversity estimates using a set of 14,045 1-min recordings from various neotropical birds and anuran communities. Our goals were to evaluate (i) the daily vocal activity cycle of birds and anurans, (ii) the effect of temporal structure (e.g., number of minutes listened each hour; continuous versus intermittent recordings) on determining the species composition, and (iii) the species–area relationship, and how the number of recorders affects species richness estimates. Based on sampling coverage and completeness, we (iv) evaluate manual inspection schedules for birds and anurans across four biomes of Brazil. We found marked diel variation in vocal activity between taxonomic groups, indicating that birds and anurans are more efficiently detected during early periods of the day and night, respectively. For proper diversity estimates, biomes with higher biodiversity required longer inspecting periods and a larger number of replicates, irrespective of taxa. Although fewer recordings per hour are less informative than full-hour sampling, species diversity is better estimated when inspected minutes are interspersed over longer periods than inspecting minutes recorded over shorter timespans. Based on our findings, we recommend how to set PAM programs over highly diverse ecosystems.
- Age-related variation in foraging behaviour in the wandering albatross at south georgia : No evidence for senescencePublication . Froy, Hannah; Lewis, Sue; Catry, Paulo; Bishop, Charles M.; Forster, Isaac P.; Fukuda, Akira; Higuchi, Hiroyoshi; Phalan, Ben; Xavier, José C.; Nussey, Daniel H.; Phillips, Richard A.Age-related variation in demographic rates is now widely documented in wild vertebrate systems, and has significant consequences for population and evolutionary dynamics. However, the mechanisms underpinning such variation, particularly in later life, are less well understood. Foraging efficiency is a key determinant of fitness, with implications for individual life history trade-offs. A variety of faculties known to decline in old age, such as muscular function and visual acuity, are likely to influence foraging performance. We examine age-related variation in the foraging behaviour of a long-lived, wide-ranging oceanic seabird, the wandering albatross Diomedea exulans. Using miniaturised tracking technologies, we compared foraging trip characteristics of birds breeding at Bird Island, South Georgia. Based on movement and immersion data collected during the incubation phase of a single breeding season, and from extensive tracking data collected in previous years from different stages of the breeding cycle, we found limited evidence for age-related variation in commonly reported trip parameters, and failed to detect signs of senescent decline. Our results contrast with the limited number of past studies that have examined foraging behaviour in later life, since these have documented changes in performance consistent with senescence. This highlights the importance of studies across different wild animal populations to gain a broader perspective on the processes driving variation in ageing rates.
- Foraging behaviour of four albatross species by night and dayPublication . Phalan, Ben; Phillips, Richard A.; Silk, Janet R. D.; Afanasyev, Vsevolod; Fukuda, Akira; Fox, James; Catry, Paulo; Higuchi, Hiroyoshi; Croxall, John P.We integrated information from satellite transmitters, GPS loggers and wet/dry activity loggers to compare the at-sea behaviour of 4 sympatric albatross species by night and day: wandering Diomedea exulans, grey-headed Thalassarche chrysostoma, black-browed T. melanophrys and light-mantled sooty Phoebetria palpebrata (in total, 350 foraging trips by 101 individuals). Trip duration, distance and maximum range varied more within species between stages (incubation, broodguard and post-brood) than between species at the same stage, implying that reproductive constraints are more important than interspecific competition in shaping foraging behaviour. Wandering albatrosses spent more time on the water in fewer, longer bouts than other species. The proportion of time spent on the water was similar among the 3 smaller species. The partitioning of foraging activity between day and night varied little between species: all landed and took off more often, but spent less time overall on the water during the day than at night. This supports observations that albatrosses forage most actively during daylight, even though many of their fish and squid prey approach the surface only at night. Albatrosses were more active on bright moonlit nights, seem to have no fixed daily requirement for sleep, rest or digestion time on the water, can navigate in darkness, and are probably unhindered by the slight reduction in mean wind strength at night. They are probably less active at night because their ability to see and capture prey from the air is reduced and it is then more energy-efficient for them to rest or to catch prey using a ‘sit-and-wait’ foraging strategy.
- Foraging strategies of grey-headed albatrosses Thalassarche chrysostoma: Integration of movements, activity and feeding eventsPublication . Catry, Paulo; Phillips, Richard A.; Phalan, Ben; Silk, Janet R. D.; Croxall, John P.We identified a range of foraging strategies adopted by grey-headed albatrosses Thalassarche chrysostoma rearing chicks at Bird Island, South Georgia, by simultaneously using satellite telemetry, wet/dry activity recorders and stomach temperature loggers. The albatrosses foraged mostly over oceanic waters, probably associated with the Polar Front north of South Georgia, and also over shelf-slope waters around the Antarctic Peninsula. After leaving the colony, birds commuted to areas with predictable prey concentrations, where they remained for several days. During search periods, birds landed more often and had a higher intake rate, but spent the same proportion of time in flight as on commuting days. Although intake rates were particularly high in shelf-break waters around the Antarctic Peninsula (only one individual foraged in this area), prey were also consumed in reasonable quantities during commuting flights. While at sea, birds spent most (81%) of the day flying, and most (94%) of the night resting on the water. A considerable proportion (26% by mass) of prey was consumed during darkness. The majority of prey were detected and captured during search flights, but 35% were located while sitting on the sea surface. Many ingestion events (up to 27% of the overall food intake) showed temperature signatures characteristic of fluids, suggesting that albatrosses may feed on gelatinous and rapidly digested prey (e.g. salps and jellyfish) much more often than previously suspected. Diet samples delivered to the chicks comprised mostly squid (particularly Martialia hyadesi) and Antarctic krill Euphausia superba.
- Senescence effects in an extremely long-lived bird: The grey-headed albatross Thalassarche chrysostomaPublication . Catry, Paulo; Phillips, Richard A.; Phalan, Ben; Croxall, John P.Studies attempting to document reproductive or other pre-lethal senescence effects in wild birds typically face an array of problems, including flaws in statistical analyses, non-adaptive philopatry to deteriorating environments, confounding effects arising from cohort heterogeneity and differential death rates of phenotypes and the frequent pairing of old birds to younger mates. Furthermore, recent studies suggest that birds could maintain a high level of physical fitness until old age, before being struck by a catastrophic illness leading quickly to their demise. The presence of terminally ill individuals in most datasets (and their greater incidence in older age categories) may therefore provide a false impression of progressive senescence in cross-sectional analyses. This study was designed explicitly to avoid all the known pitfalls linked to the demonstration of progressive senescence in wild populations, and involved one of the very longest-lived bird species.We show that, during incubation, old (aged 35 years and over) male grey-headed albatrosses Thalassarche chrysostoma make longer foraging trips, and have lower daily mass gains, than experienced mid-aged individuals (aged up to 28 years). This is, to our knowledge, the first report documenting reduced foraging performance with old age. Hatching and breeding success of pairs composed of two old individuals were reduced in comparison to mid-aged pairs. Overall results were very similar when analyses were repeated using only individuals known to have survived 1 or 2 years beyond field measurements (hence probably not suffering from the effects of an advanced terminal illness). We conclude that extremely long-lived individuals usually experience some degree of general physical deterioration, leading to reduced foraging and breeding performance, long before their final demise.