[show abstract][hide abstract] ABSTRACT: Ocean-scale monitoring of pollution is challenging. Seabirds are useful indicators because they travel over a broad foraging range. Nevertheless, this coarse spatial resolution is not fine enough to discriminate pollution in a finer scale. Previous studies have demonstrated that pollution levels are higher in the Sea of Japan and South and East China Seas than Northen Pacific Ocean. To test these findings in a wide-ranging animal, we GPS-tracked streaked shearwaters (Calonectris leucomelas) from four islands in Japan and measured persistent organic pollutants (POPs) in the oil of their preen glands. The POPs did not change during 6 to 21 days when birds from Awashima were foraging only in the Sea of Japan, while it increased when they crossed to the Pacific through the Tsugaru Strait and foraged along the eastern coast of Hokkaido where industrial cities occur. These results indicate that POPs in the oil reflect relatively short-term exposure. Concentrations of POPs displayed greater variation among regions. Total polychlorinated biphenyls were highest in birds foraging in a small area of the semi-closed Seto Inland Sea surrounded by urbanized coast, p,p'-DDT was highest in birds foraging in the East China Sea, and total hexachlorocyclohexanes were highest in birds foraging in the Sea of Japan, and all were lowest in birds foraging in the Pacific. This distribution of POPs concentration partly agrees with previous findings based on mussels, fish, and seawater, and possibly reflects the mobility and emission sources of each type of POP. These results highlight the importance of information on the foraging area of highly mobile top predators to make them more effective monitors of regional marine pollution.
[show abstract][hide abstract] 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. · 0.65 Impact Factor
[show abstract][hide abstract] 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.
[show abstract][hide abstract] ABSTRACT: Understanding how prey capture rates are influenced by feeding ecology and environmental conditions is fundamental to assessing anthropogenic impacts on marine higher predators. We compared how prey capture rates varied in relation to prey size, prey patch distribution and prey density for two species of alcid, common guillemot (Uria aalge) and razorbill (Alca torda) during the chick-rearing period. We developed a Monte Carlo approach parameterised with foraging behaviour from bird-borne data loggers, observations of prey fed to chicks, and adult diet from water-offloading, to construct a bio-energetics model. Our primary goal was to estimate prey capture rates, and a secondary aim was to test responses to a set of biologically plausible environmental scenarios. Estimated prey capture rates were 1.5±0.8 items per dive (0.8±0.4 and 1.1±0.6 items per minute foraging and underwater, respectively) for guillemots and 3.7±2.4 items per dive (4.9±3.1 and 7.3±4.0 items per minute foraging and underwater, respectively) for razorbills. Based on species' ecology, diet and flight costs, we predicted that razorbills would be more sensitive to decreases in 0-group sandeel (Ammodytes marinus) length (prediction 1), but guillemots would be more sensitive to prey patches that were more widely spaced (prediction 2), and lower in prey density (prediction 3). Estimated prey capture rates increased non-linearly as 0-group sandeel length declined, with the slope being steeper in razorbills, supporting prediction 1. When prey patches were more dispersed, estimated daily energy expenditure increased by a factor of 3.0 for guillemots and 2.3 for razorbills, suggesting guillemots were more sensitive to patchier prey, supporting prediction 2. However, both species responded similarly to reduced prey density (guillemot expenditure increased by 1.7; razorbill by 1.6), thus not supporting prediction 3. This bio-energetics approach complements other foraging models in predicting likely impacts of environmental change on marine higher predators dependent on species-specific foraging ecologies.
PLoS ONE 01/2013; 8(11):e79915. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Long-lived animals sometimes skip one or more breeding seasons; however, little is known about their movements and activities during such ‘sabbatical’ periods. Here we present novel data on year-round movements and activities of two male black-tailed gulls Larus crassirostris during a sabbatical year. We compare the data with those in a year when they bred and with those of two other breeding males. The year-round migration routes of two sabbatical males were consistent with those of the breeding males: they returned to the breeding area but did not visit the colony in the sabbatical year. They landed more frequently on water (a potential index of foraging effort) during the non-breeding autumn and winter prior to the sabbatical year than before breeding. Sabbatical gulls may forage more intensively to recover body condition immediately after breeding.
Journal of Avian Biology 01/2013; 44(6):603-608. · 2.02 Impact Factor
[show abstract][hide abstract] ABSTRACT: Identifying areas of high species diversity and abundance is important for understanding ecological processes and conservation planning. These areas serve as foraging habitat or important breeding or settlement areas for multiple species, and are often termed ‘hotspots’. Marine hotspots have distinct biophysical features that lead to their formation, persistence, and recurrence, and that make them important oases in oceanic seascapes. Building upon a session at the North Pacific Marine Science Organization (PICES), this Theme Section explores the scales and mechanisms underlying hotspot formation. Fundamentally, understanding the mechanisms of hotspot formation is important for determining how hotspots may shift relative to ocean features and climate change, which is a prerequisite for determining management priorities.
Marine Ecology Progress Series 01/2013; 487:177-183. · 2.55 Impact Factor
[show abstract][hide abstract] 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. · 1.55 Impact Factor
[show abstract][hide abstract] 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. · 1.55 Impact Factor
[show abstract][hide abstract] 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
KeywordsFeeding ecology-Foraging behavior-Sex-specific behavior-State-dependent decision-Streaked shearwater
Journal of Ethology 04/2012; 28(2):313-321. · 1.00 Impact Factor
[show abstract][hide abstract] 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.
[show abstract][hide abstract] 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. · 1.00 Impact Factor
[show abstract][hide abstract] 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.
[show abstract][hide abstract] 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.
[show abstract][hide abstract] ABSTRACT: When rearing chicks, seabirds increase their daily energy expenditures during commuting flights between foraging areas and breeding colonies, owing to the heavy food loads. At this time, parents are expected to enlarge the size of their energy-supplying organs in response to the increased energy demands but reduce their total body mass to minimize the energetic cost of flight. The changes in body components of 40 incubating and chick-rearing rhinoceros auklets (Cerorhinca monocerata) were examined. Chick-rearing auklets did not have larger energy-supplying organs and breast muscles than incubating ones. However, chick-rearing auklets had greater ash composition, but smaller lipid contents, of breast muscles than incubating ones, whereas the former had a mass of water and protein similar to the latter. Male and female auklets lost a mean of 32.6 and 32.1 g in body mass between incubation and chick-rearing stages, mainly via loss of lipid reserves, which consequently reduces flight costs by 9.9 and 9.1%, respectively. Performance of commuting flight could be improved through changes in breast muscle compositions and reductions in total body mass. Although auklets did not enlarge their energy-supplying organs, their body conditions could be maintained within the same phase between the breeding stages.
Canadian Journal of Zoology 02/2011; 80(9):1549-1555. · 1.50 Impact Factor
[show abstract][hide abstract] ABSTRACT: By manipulating meal size and frequency in an alcid, the rhinoceros auklet (Cerorhinca monocerata (Pallas, 1811)), we examined two hypotheses: (1) poorly fed chicks allocate resources preferentially to developing organs essential for fledging, and (2) intermittently fed chicks deposit more lipids than regularly fed ones. Chicks were fed normal (NORMAL; 40–80 g, mean meal mass in a normal year), small (LOW; 26–54 g, half of NORMAL), or large (HIGH; 80–160 g, twice as much as NORMAL) amounts of sandlance (Ammodytes personatus Girard, 1856) every day or the large meal (80–160 g) every 2 days (INTERMITTENT). Chicks fed more food grew faster. The HIGH group had the greatest fledging mass and shortest fledging period. The wingspan and brain mass of fledglings did not differ among groups. The heart, liver, and breast muscle at fledging were 15%–25% smaller in the LOW group than in the NORMAL group but did not differ between the NORMAL and HIGH groups. The total lipid was 43% greater in the HIGH group than in the NORMAL group, and that of the LOW group was 38% smaller. The INTERMITTENT group had a similar lipid mass to the NORMAL group. Chicks feeding on small meals seemed to maintain the growth of organs essential for fledging, while chicks feeding on large meals seemed to deposit a surplus as lipid rather than allocate more to the development of organs.
Canadian Journal of Zoology 02/2011; 83(11):1476-1485. · 1.50 Impact Factor
[show abstract][hide abstract] ABSTRACT: The physiological state of parent birds combined with the value of their clutch may affect the intensity of their nest defense. In colonially breeding birds, nest-defense intensity may also be affected by the behavior of neighbors. We investigated individual variation in the nest-defense intensity among colonial Black-tailed Gulls (Larus crassirostris Vieillot, 1818) over 2 years. Only 30%–40% of males attacked a decoy of an egg predator (Large-billed Crow (Corvus macrorhynchos Wagler, 1827)), and the other males and females rarely attacked. Males attacking the decoy had higher levels of plasma testosterone than males that did not attack. Each male’s, but not female’s, nest-defense intensity was consistent throughout the incubation period and also across years. The intensity was not related to egg-laying date, clutch size, or age of offspring. The intensity was likely to be higher when individuals had one or more neighbors, representing higher nest-defense intensity in the year where gulls had larger number of adjacent neighboring nests (5.23 nests), but this trend was not observed in the year where they had smaller number of the neighboring nests (3.73 nests). Thus, in addition to testosterone levels, behavior of neighbors also influences the nest-defense intensity.
Canadian Journal of Zoology 01/2011; 89(10):938-944. · 1.50 Impact Factor
[show abstract][hide abstract] 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·kg–1), 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.
[show abstract][hide abstract] ABSTRACT: Testosterone affects male sexual-, aggressive-, and parental-behaviors in bird species. To understand the breadth of the proximate contribution of testosterone to breeding behaviors in male Black-tailed Gulls Larus crassirostris, sexual behaviors, aggressive behaviors against egg-predators and conspecifics, and chick-provisioning behavior of five testosterone-implanted males (T-males) were observed and compared with those of three control males (placebo-implanted; C-males). T-males showed significantly higher levels of courtship and copulation behaviors than C-males. The levels of aggressiveness against egg-predators and against conspecifics, and the rate of feeding of chicks did not differ between T- and C-males. These results suggest that sexual and mating behaviors in male Black-tailed Gulls may be affected by testosterone, while aggressive- and feeding-behaviors are affected by certain ecological factors, such as individual age, or a necessity for high levels of feeding by males, rather than by testosterone.