Yutaka Watanuki

Publications (58)117.69 Total impact

• Article: Heavy metal pollution in Japanese seabirds.

  Chihiro Ishii, Yoshinori Ikenaka, Shouta M M Nakayama, Yuya Suzuki, Yutaka Watanuki, Yuji Watanabe, Masa-aki Fukuwaka, Yared B Yohannes, Yusuke K Kawai, Mayumi Ishizuka
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  ABSTRACT: It is reported that seabirds accumulate high levels of metals, prompting concerns regarding poisoning. The present study investigated the accumulation patterns of metals in tissues among four species of seabirds (Fratercula corniculata, Uria lomvia, Puffinus tenuirostris, and Fulmarus glacialis). Furthermore, we focused on Slaty-backed Gulls, which accumulated high levels of cadmium and mercury, and compared the areal differences. Geographic variation of metal levels could also contribute to differences in metal accumulation levels in these bird species. Therefore, the concentrations of metals in seabirds are considered to reflect their habitat. There are differences in the accumulation pattern among the seabird species. The high accumulation of metals could affect seabirds even if they do not show any symptoms.
  The Japanese journal of veterinary research 02/2013; 61 Suppl:S75-6. · 0.46 Impact Factor
• Article: Accumulation of plastic-derived chemicals in tissues of seabirds ingesting marine plastics.

  Kosuke Tanaka, Hideshige Takada, Rei Yamashita, Kaoruko Mizukawa, Masa-Aki Fukuwaka, Yutaka Watanuki
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  ABSTRACT: We analyzed polybrominated diphenyl ethers (PBDEs) in abdominal adipose of oceanic seabirds (short-tailed shearwaters, Puffinus tenuirostris) collected in northern North Pacific Ocean. In 3 of 12 birds, we detected higher-brominated congeners (viz., BDE209 and BDE183), which are not present in the natural prey (pelagic fish) of the birds. The same compounds were present in plastic found in the stomachs of the 3 birds. These data suggested the transfer of plastic-derived chemicals from ingested plastics to the tissues of marine-based organisms.
  Marine pollution bulletin 01/2013; · 2.63 Impact Factor
• Article: Effect of interannual variations in sea-surface temperature on egg-laying parameters of black-tailed gulls (Larus crassirostris) at Teuri Island, Japan

  Naoki Tomita, Yasuaki Niizuma, Masaoki Takagi, Motohiro Ito, Yutaka Watanuki
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  ABSTRACT: Sea-surface temperature (SST) directly and indirectly affects the distribution and abundance of prey species for seabirds, so we expect variation in SST to be associated with variation in seabird life history traits. In black-tailed gulls (Larus crassirostris) at Teuri Island in northern Hokkaido, Japan, we investigated the diet of the gulls prior to egg laying in 2004 and 2005, and examined the influences of SST in March or April, when the gulls congregate in the colony, on egg-laying parameters using 13years of data (1992–2004). The gulls fed on krill (Thysanoessa inermis) and fish prior to the egg laying. Mean first egg dates and clutch sizes were significantly and quadratically related to SST anomalies in March, but were not influenced by SST anomalies in April. There was no significant effect of SSTs in either March or April on egg volume. Sea-surface temperature anomalies in March of the years of early laying (−1 to 1°C) were higher than those in 2001 (−2.2°C), but lower than those in 1992 (+1.2°C) and 2004 (+1.1°C). Thysanoessa inermis congregates to spawn at the sea surface, when SSTs rise 3−4°C. Thus, a mismatch between food availability and the timing of egg production in the gulls could have occurred in these 3years. This study suggests that SST fluctuations prior to laying are important in breeding success of black-tailed gulls.
  Ecological Research 04/2012; 24(1):157-162. · 1.57 Impact Factor
• Article: Seasonal changes of the at-sea distribution and food provisioning in rhinoceros auklets

  Tomohiro Deguchi, Akihiko Wada, Yutaka Watanuki, Yuichi Osa
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  ABSTRACT: Central-place foraging seabirds increase food-loads and decrease meal frequency when they forage in areas that are distant from the breeding colony. In 2001–2002, we studied the seasonal changes in at-sea distribution, food-load mass, meal frequency, and fledging mass in rhinoceros auklets (Cerorhinca monocerata), which forage in coastal waters during the day and feed their chicks at night. In both years, greater numbers of auklets were observed flying in northern waters that are more distant from the colony in June (65km) and July (65–66km) than in May (38–47km). In July of both years, many auklets flew northward across the transect set 65–120km north of the colony at sunrise; the birds returned south again at sunset, indicating that they foraged in waters outside the study area. This seasonal northward movement of the foraging area may reflect the migration of their main prey item, the Japanese anchovy (Engraulis japonicus), which move with the Tsushima Warm Current flowing from the southern Sea of Japan. Food-load mass did not increase seasonally. In both years, the estimated daily meal frequency was lower in July than in May or June, partly because of the increased foraging distance in July. Late-hatched chicks also displayed lighter fledging masses than early chicks in both years. We suggest that late breeders are required to forage at great distances for longer periods, which may result in decreased meal frequency and lighter fledging mass of their chicks.
  Ecological Research 04/2012; 25(1):123-137. · 1.57 Impact Factor
• Source

  Available from: Daisuke Ochi

  Article: Foraging trip decisions by the streaked shearwater Calonectris leucomelas depend on both parental and chick state

  Daisuke Ochi, Nariko Oka, Yutaka Watanuki
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  ABSTRACT: Parents of albatross and shearwater species employ a dual foraging strategy, feeding their chicks quickly in repeated short trips and then restoring their own fuel reserves during longer trips. A decline in parental body condition is believed to trigger longer trips, but chick body condition and age may also play a role. To investigate these factors in the little-studied streaked shearwater Calonectris leucomelas, we monitored the nest attendance of 17 pairs on Mikura Island in 2005 using an automated identification system. We also monitored body mass changes and meal masses of 5 of the 17 pairs using an automated weighing system. Although the birds did not show a clear dual foraging pattern, trip duration varied widely from 1 to 15days. On average, the birds fed chicks 67.6g during nighttime meals at 2.74-day intervals. Since meal mass did not depend on trip duration, feeding efficiency (meal mass delivered per unit trip duration) decreased as trip duration increased. Parents accumulated more energy reserves when they took longer trips. Parents appeared likely to initiate longer trips when their body condition declined or chick body condition recovered. KeywordsFeeding ecology-Foraging behavior-Sex-specific behavior-State-dependent decision-Streaked shearwater
  Journal of Ethology 04/2012; 28(2):313-321. · 1.18 Impact Factor
• Article: Accelerated growth rates in late-hatched Rhinoceros Auklet Cerorhinca monocerata chicks depend on food conditions and growth stage: an experimental approach

  Fumi Hirose, Kentaro Kazama, Motohiro Ito, Yutaka Watanuki
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  ABSTRACT: In some bird species, the survival of chicks hatching later in the season is lower than those hatched earlier due to increased risk of predation and a seasonal decline in feeding conditions. To reduce these risks, it might be advantageous for late-hatched chicks to grow faster and hence fledge at younger age. In this experimental study, the growth rates of early- and late-hatched Rhinoceros Auklet Cerorhinca monocerata chicks were compared under average and poor food supplies in captivity. Controlling for potentially confounding effects of chick mass at 10 days old, chick age and nest-chamber temperature, late-hatched chicks had higher wing growth rate than early-hatched chicks before attaining the minimum wing length required for fledgling under both average and poor food supplies. After attaining the minimum wing length, however, late-hatched chicks had a lower fledging mass, indicating a potential cost that could diminish the early advantage of fast wing growth.
  Ibis 01/2012; 154(2):296-306. · 2.43 Impact Factor
• Article: Consistent individual variations in aggressiveness and a behavioral syndrome across breeding contexts in different environments in the Black-tailed Gull

  Kentaro Kazama, Yasuaki Niizuma, Yutaka Watanuki
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  ABSTRACT: Individual behaviors of animals do not evolve separately; they do so in association with other behaviors caused by single shared genetic or physiological constraints and/or favored by selection. Thus, measuring behavioral syndromes—suites of correlated behaviors across different contexts—leads to a better understanding of the adaptive significance of variations in behaviors. However, relatively few studies have examined behavioral syndromes in wild animal populations in changing environments. We investigated a potential behavioral syndrome across antipredator nest defense, territorial defense, chick provisioning, and mating behaviors of male Black-tailed Gulls Larus crassirostris in two successive years under different conspecific territorial intrusion risks and food conditions. Males that presented high levels of antipredator nest defense (aggressive antipredator defenders) against a crow decoy (crows are egg predators) defended their territories against conspecific intruders more frequently than did other males (nonaggressive antipredator defenders), independent of the risk of intrusion. Aggressive antipredator defenders also fed their chicks more frequently than nonaggressive males, but only in a year of low food availability. Taken together, this indicates that males show consistent aggressiveness regardless of breeding context (antipredator and territorial defense), but can regulate food provisioning according to food availability.
  Journal of Ethology 01/2012; 30(2):279-288. · 1.18 Impact Factor
• Article: Intraspecific Kleptoparasitism, Attacks on Chicks and Chick Adoption in Black-tailed Gulls (Larus crassirostris)

  Kentaro Kazama, Yasuaki Niizuma, Yutaka Watanuki
  Waterbirds 01/2012; 35(4):599-607. · 0.76 Impact Factor
• Article: Physical and chemical effects of ingested plastic debris on short-tailed shearwaters, Puffinus tenuirostris, in the North Pacific Ocean.

  Rei Yamashita, Hideshige Takada, Masa-aki Fukuwaka, Yutaka Watanuki
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  ABSTRACT: We investigated the plastics ingested by short-tailed shearwaters, Puffinus tenuirostris, that were accidentally caught during experimental fishing in the North Pacific Ocean in 2003 and 2005. The mean mass of plastics found in the stomach was 0.23 g per bird (n=99). Plastic mass did not correlate with body weight. Total PCB (sum of 24 congeners) concentrations in the abdominal adipose tissue of 12 birds ranged from 45 to 529 ng/g-lipid. Although total PCBs or higher-chlorinated congeners, the mass of ingested plastic correlated positively with concentrations of lower-chlorinated congeners. The effects of toxic chemicals present in plastic debris on bird physiology should be investigated.
  Marine pollution bulletin 10/2011; 62(12):2845-9. · 2.63 Impact Factor
• Source

  Available from: Akiko Kato

  Article: Oxygen Store and Diving Capacity of Rhinoceros Auklet Cerorhinca monocerata

  Maki Yamamoto, Akiko Kato, Yasuaki Niizuma, Yutaka Watanuki
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  ABSTRACT: Alcids dive longer than are predicted by their body size alone, but the physiological mechanisms that explain their excellent diving capabilities are poorly understood. In this study, we estimated the oxygen stores of Rhinoceros Auklets Cerorhinca monocerata, medium-sized alcids that attained depths down to 62 m within 2.5 min. Hematocrit was 43.9±2.8%, hemoglobin concentration was 17.2±4.6 g·100 ml-1, and blood volume was 12.7±1.9% of their body mass. Myoglobin concentration in breast muscle (1.8±0.3 g·100 g-1) was higher than that in leg muscle (1.2±0.2 g·100 g-1). Rhinoceros Auklets have higher blood volume, hemoglobin and myoglobin concentrations, as do other flying/diving seabirds (other alcids and cormorants), than flying/non-diving seabirds (terns and kittiwakes). The oxygen store of Rhinoceros Auklets was estimated at 54.5 ml·kg-1. Using the average oxygen consumption rate of diving seabirds (1.01 ml·s 1·kg1), we calculated their theoretical aerobic dive limit (TADL) as 53.9 s. Nearly half of their dives (47.2%) exceeded their TADL, because an overestimation of their oxygen consumption rate during diving resulted in an underestimation of TADL.
  ORNITHOLOGICAL SCIENCE 08/2011;
• Source

  Available from: Rei Yamashita

  Article: The relationship between pink salmon biomass and the body condition of short-tailed shearwaters in the Bering Sea: can fish compete with seabirds?

  Kanako Toge, Rei Yamashita, Kentaro Kazama, Masaaki Fukuwaka, Orio Yamamura, Yutaka Watanuki
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  ABSTRACT: Seabirds and large fishes are important top predators in marine ecosystems, but few studies have explored the potential for competition between these groups. This study investigates the relationship between an observed biennial change of pink salmon (Oncorhynchus gorbuscha) biomass in the central Bering Sea (23 times greater in odd-numbered than in even-numbered years) and the body condition and diet of the short-tailed shearwater (Puffinus tenuirostris) that spends the post-breeding season there. Samples were collected with research gill nets over seven summers. Both species feed on krill, small fishes and squid. Although the mean pink salmon catch per unit effort (in mass) over the study region was not related significantly with shearwater's stomach content mass or prey composition, the pink salmon biomass showed a negative and significant relationship with the shearwater's body mass and liver mass (proxies of energy reserve). We interpret these results as evidence that fishes can negatively affect mean prey intake of seabirds if they feed on a shared prey in the pelagic ecosystem.
  Proceedings of the Royal Society B: Biological Sciences 01/2011; 278(1718):2584-90. · 5.41 Impact Factor
• Source

  Available from: Kentaro Kazama

  Article: Factors affecting individual variation in nest-defense intensity in colonially breeding Black-tailed Gulls (Larus crassirostris)

  Kentaro Kazama, Yasuaki Niizuma, Kentaro Q. Sakamoto, Yutaka Watanuki
  Canadian Journal of Zoology 01/2011; 89(10):938-944. · 1.21 Impact Factor
• Article: Scaling of swim speed in breath-hold divers.

  Yuuki Y Watanabe, Katsufumi Sato, Yutaka Watanuki, Akinori Takahashi, Yoko Mitani, Masao Amano, Kagari Aoki, Tomoko Narazaki, Takashi Iwata, Shingo Minamikawa, Nobuyuki Miyazaki
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  ABSTRACT: 1. Breath-hold divers are widely assumed to descend and ascend at the speed that minimizes energy expenditure per distance travelled (the cost of transport (COT)) to maximize foraging duration at depth. However, measuring COT with captive animals is difficult, and empirical support for this hypothesis is sparse. 2. We examined the scaling relationship of swim speed in free-ranging diving birds, mammals and turtles (37 species; mass range, 0·5-90,000 kg) with phylogenetically informed statistical methods and derived the theoretical prediction for the allometric exponent under the COT hypothesis by constructing a biomechanical model. 3. Swim speed significantly increased with mass, despite considerable variations around the scaling line. The allometric exponent (0·09) was statistically consistent with the theoretical prediction (0·05) of the COT hypothesis. 4. Our finding suggests a previously unrecognized advantage of size in divers: larger animals swim faster and thus could travel longer distance, search larger volume of water for prey and exploit a greater range of depths during a given dive duration. 5. Furthermore, as predicted from the model, endotherms (birds and mammals) swam faster than ectotherms (turtles) for their size, suggesting that metabolic power production limits swim speed. Among endotherms, birds swam faster than mammals, which cannot be explained by the model. Reynolds numbers of small birds (<2 kg) were close to the lower limit of turbulent flow (∼ 3 × 10(5) ), and they swam fast possibly to avoid the increased drag associated with flow transition.
  Journal of Animal Ecology 10/2010; 80(1):57-68. · 4.94 Impact Factor
• Article: Individual differences in nest defense in the colonial breeding Black-tailed Gulls

  Kentaro Kazama, Yutaka Watanuki
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  ABSTRACT: Abstract Often in colonial seabirds, all colony members are believed to defend against nest predators and experience equal nest predation risk. However, the variation of defense behavior among members and its reproductive consequences are largely unknown. We investigated (1) individual variation in the nest defense of breeding Black-tailed Gulls Larus crassirostris against a natural egg predator, the Jungle Crow Corvus macrorhynchos and (2) how this behavioral variation affects an individual’s own nest predation risk and that of their neighbors. Results were compared between 2 years where crow attack levels were manipulated to average 5 and 22 times normal rates (“low” and “high” predation risk years, respectively) by the placement of varying numbers of artificial nests containing unguarded eggs at the perimeter of the gull colony. In both years, 23–38% of parents, mostly males, showed “aggressive” defense behavior (strikes or chases) against crows and decoys. Other “non-aggressive” gulls showed no defense. In the year of low predation risk, intrusion rates by crows (landing within 0.5 m of an individual gull’s nest) were similar for aggressive and non-aggressive gulls. In the year of high predation risk, however, the rates of intrusion for aggressive gulls (4%) and for non-aggressive gulls with an aggressive neighbor (37%) were significantly lower than for non-aggressive gulls without an aggressive neighbor (76%). These results indicate that aggressive individuals reduce nest predation risk for themselves and conspecific neighbors in a colonially breeding species.
  Behavioral Ecology and Sociobiology 01/2010; 64(8):1239-1246. · 3.18 Impact Factor
• Article: Scaling of swim speed and stroke frequency in geometrically similar penguins: they swim optimally to minimize cost of transport.

  Katsufumi Sato, Kozue Shiomi, Yuuki Watanabe, Yutaka Watanuki, Akinori Takahashi, Paul J Ponganis
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  ABSTRACT: It has been predicted that geometrically similar animals would swim at the same speed with stroke frequency scaling with mass(-1/3). In the present study, morphological and behavioural data obtained from free-ranging penguins (seven species) were compared. Morphological measurements support the geometrical similarity. However, cruising speeds of 1.8-2.3 m s(-1) were significantly related to mass(0.08) and stroke frequencies were proportional to mass(-0.29). These scaling relationships do not agree with the previous predictions for geometrically similar animals. We propose a theoretical model, considering metabolic cost, work against mechanical forces (drag and buoyancy), pitch angle and dive depth. This new model predicts that: (i) the optimal swim speed, which minimizes the energy cost of transport, is proportional to (basal metabolic rate/drag)(1/3) independent of buoyancy, pitch angle and dive depth; (ii) the optimal speed is related to mass(0.05); and (iii) stroke frequency is proportional to mass(-0.28). The observed scaling relationships of penguins support these predictions, which suggest that breath-hold divers swam optimally to minimize the cost of transport, including mechanical and metabolic energy during dive.
  Proceedings of the Royal Society B: Biological Sciences 11/2009; 277(1682):707-14. · 5.41 Impact Factor
• Article: Transport and release of chemicals from plastics to the environment and to wildlife.

  Emma L Teuten, Jovita M Saquing, Detlef R U Knappe, Morton A Barlaz, Susanne Jonsson, Annika Björn, Steven J Rowland, Richard C Thompson, Tamara S Galloway, Rei Yamashita, [......], Mohamad P Zakaria, Kongsap Akkhavong, Yuko Ogata, Hisashi Hirai, Satoru Iwasa, Kaoruko Mizukawa, Yuki Hagino, Ayako Imamura, Mahua Saha, Hideshige Takada
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  ABSTRACT: Plastics debris in the marine environment, including resin pellets, fragments and microscopic plastic fragments, contain organic contaminants, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, petroleum hydrocarbons, organochlorine pesticides (2,2'-bis(p-chlorophenyl)-1,1,1-trichloroethane, hexachlorinated hexanes), polybrominated diphenylethers, alkylphenols and bisphenol A, at concentrations from sub ng g(-1) to microg g(-1). Some of these compounds are added during plastics manufacture, while others adsorb from the surrounding seawater. Concentrations of hydrophobic contaminants adsorbed on plastics showed distinct spatial variations reflecting global pollution patterns. Model calculations and experimental observations consistently show that polyethylene accumulates more organic contaminants than other plastics such as polypropylene and polyvinyl chloride. Both a mathematical model using equilibrium partitioning and experimental data have demonstrated the transfer of contaminants from plastic to organisms. A feeding experiment indicated that PCBs could transfer from contaminated plastics to streaked shearwater chicks. Plasticizers, other plastics additives and constitutional monomers also present potential threats in terrestrial environments because they can leach from waste disposal sites into groundwater and/or surface waters. Leaching and degradation of plasticizers and polymers are complex phenomena dependent on environmental conditions in the landfill and the chemical properties of each additive. Bisphenol A concentrations in leachates from municipal waste disposal sites in tropical Asia ranged from sub microg l(-1) to mg l(-1) and were correlated with the level of economic development.
  Philosophical Transactions of The Royal Society B Biological Sciences 08/2009; 364(1526):2027-45. · 6.40 Impact Factor
• Source

  Available from: Charles André Bost

  Article: Scaling of soaring seabirds and implications for flight abilities of giant pterosaurs.

  Katsufumi Sato, Kentaro Q Sakamoto, Yutaka Watanuki, Akinori Takahashi, Nobuhiro Katsumata, Charles-André Bost, Henri Weimerskirch
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  ABSTRACT: The flight ability of animals is restricted by the scaling effects imposed by physical and physiological factors. In comparisons of the power available from muscle and the mechanical power required to fly, it is predicted that the margin between the powers should decrease with body size and that flying animals have a maximum body size. However, predicting the absolute value of this upper limit has proven difficult because wing morphology and flight styles varies among species. Albatrosses and petrels have long, narrow, aerodynamically efficient wings and are considered soaring birds. Here, using animal-borne accelerometers, we show that soaring seabirds have two modes of flapping frequencies under natural conditions: vigorous flapping during takeoff and sporadic flapping during cruising flight. In these species, high and low flapping frequencies were found to scale with body mass (mass(-0.30) and mass(-0.18)) in a manner similar to the predictions from biomechanical flight models (mass(-1/3) and mass(-1/6)). These scaling relationships predicted that the maximum limits on the body size of soaring animals are a body mass of 41 kg and a wingspan of 5.1 m. Albatross-like animals larger than the limit will not be able to flap fast enough to stay aloft under unfavourable wind conditions. Our result therefore casts doubt on the flying ability of large, extinct pterosaurs. The largest extant soarer, the wandering albatross, weighs about 12 kg, which might be a pragmatic limit to maintain a safety margin for sustainable flight and to survive in a variable environment.
  PLoS ONE 02/2009; 4(4):e5400. · 4.09 Impact Factor
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  Available from: PubMed Central

  Article: Can ethograms be automatically generated using body acceleration data from free-ranging birds?

  Kentaro Q Sakamoto, Katsufumi Sato, Mayumi Ishizuka, Yutaka Watanuki, Akinori Takahashi, Francis Daunt, Sarah Wanless
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  ABSTRACT: An ethogram is a catalogue of discrete behaviors typically employed by a species. Traditionally animal behavior has been recorded by observing study individuals directly. However, this approach is difficult, often impossible, in the case of behaviors which occur in remote areas and/or at great depth or altitude. The recent development of increasingly sophisticated, animal-borne data loggers, has started to overcome this problem. Accelerometers are particularly useful in this respect because they can record the dynamic motion of a body in e.g. flight, walking, or swimming. However, classifying behavior using body acceleration characteristics typically requires prior knowledge of the behavior of free-ranging animals. Here, we demonstrate an automated procedure to categorize behavior from body acceleration, together with the release of a user-friendly computer application, "Ethographer". We evaluated its performance using longitudinal acceleration data collected from a foot-propelled diving seabird, the European shag, Phalacrocorax aristotelis. The time series data were converted into a spectrum by continuous wavelet transformation. Then, each second of the spectrum was categorized into one of 20 behavior groups by unsupervised cluster analysis, using k-means methods. The typical behaviors extracted were characterized by the periodicities of body acceleration. Each categorized behavior was assumed to correspond to when the bird was on land, in flight, on the sea surface, diving and so on. The behaviors classified by the procedures accorded well with those independently defined from depth profiles. Because our approach is performed by unsupervised computation of the data, it has the potential to detect previously unknown types of behavior and unknown sequences of some behaviors.
  PLoS ONE 02/2009; 4(4):e5379. · 4.09 Impact Factor
• Article: PROXIMATE FACTORS DETERMINING AGE AND MASS AT FLEDGING IN RHINOCEROS AUKLETS (CERORHINCA MONOCERATA): INTRA- AND INTERYEAR VARIATIONS

  Tomohiro Deguchi, Akinori Takahashi, Yutaka Watanuki
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  ABSTRACT: En los álcidos, la tasa de crecimiento y la fecha de eclosión de los pichones parecen afectar la edad y la masa de éstos al momento de emplumar. Se hipotetiza que los mecanismos responsables son: (1) existencia de una longitud del ala crítica para la supervivencia de los volantones, (2) sincronización del emplumamiento para diluir el riesgo de depredación y (3) aprovisionamiento parental variable de acuerdo al momento del apareamiento. Para elucidar los efectos de la tasa de crecimiento y la fecha de eclosión sobre la edad y masa de los volantones y para poner a prueba estas hipótesis mecanísticas, medimos el crecimiento de los pichones y los períodos de emplumamiento en la especie Cerorhinca monocerata en la isla Teuri entre 1995 y 2000. Un análisis de regresión lineal múltiple mostró que las variaciones intra-anuales de la edad y masa de los volantones se podían explicar por la tasa de crecimiento o la fecha de eclosión en cinco de los seis años. Los pichones que crecieron más rápido emplumaron a menor edad y con mayor peso y los que eclosionaron más temprano emplumaron a mayor edad y con mayor peso. En consecuencia, no se observó una correlación aparente entre la edad de emplumamiento y la masa en cinco de los seis años. Análisis de la variación interanual mostraron una correlación negativa entre la edad de emplumamiento y el peso, lo que indica que las tasas de crecimiento (y no las fechas de eclosión) tuvieron un efecto importante. La longitud del ala al momento de abandonar el nido fue independiente del crecimiento en términos de peso. Más del 80% de los pichones emplumaron cuando alcanzaron un estrecho rango de longitud del ala (130–150 mm), presumiblemente porque permanecieron en sus nidos hasta que alcanzaron la longitud crítica del ala. En cinco de los seis años los pichones no sicronizaron el momento de emplumamiento con relación al momento de eclosión. Los pichones que eclosionaron más tarde alcanzaron pesos pico menores y a menor edad, lo que podría indicar que sus padres disminuyeron las tasas de aprovisionamiento cuando los pichones todavía eran jóvenes. Sugerimos que la existencia de una longitud del ala crítica para la supervivencia de los volantones y de aprovisionamiento parental variable de acuerdo al momento del apareamiento podrían ser mecanismos determinantes de las relaciones entre la edad y el peso de los volantones al momento de emplumar.
  The Auk 01/2009; · 2.16 Impact Factor
• Article: VARIATION IN FORAGING AND PARENTAL BEHAVIOR OF KING CORMORANTS

  Akiko Kato, Yutaka Watanuki, Isao Nishiumi, Maki Kuroki, Peter Shaughnessy, Yasuhiko Naito
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  ABSTRACT: We studied sexual and individual differences in foraging and parental behavior of King Cormorants (Phalacrocorax albiventer) during the brood-rearing period at Macquarie Island. King Cormorants exhibit sexual dimorphism in size, with males being 16% heavier than females. Females foraged mainly in the morning and males in the afternoon. Five females were shallow divers (1.9 to 6.8 m), and seven females were deep divers (19.6 to 28.0 m); males dived deeper (15.6 to 44.2 m) than both groups of females. The amount of time spent on the bottom (“bottom time”) relative to the dive cycle was higher for shallow-diving females (x̄ = 40 ± SD of 13%) than for males (x̄ = 26 ± 4%) and deep-diving females (x̄ = 27 ± 3%). Total daily dive time and bottom time per day did not differ significantly among groups because shallow-diving females dived more often (x̄ = 211 ± 81 dives per day) than males (x̄ = 68 ± 21) and deep-diving females (x̄ = 70 ± 7). Provisioning rate, trip duration, and proportion of time at sea did not differ significantly for males, deep-diving females, and shallow-diving females. Females, especially shallow divers, compensated for their shallow and short dives with more frequent dives. Consequently, male and female King Cormorants provisioned their chicks at similar rates despite large individual variation in foraging behavior.
  The Auk 01/2009; · 2.16 Impact Factor