Bioaccumulation and metabolism of PCBs and DDE in Short-tailed Shearwater Puffinus tenuirostris during its transequatorial migration and in the wintering and breeding grounds

PCBs and p, p\u27-DDE in Short-tailed Shearwater (Puffinus tenuirostris) from Tasmania, Japan and the northern North Pacific were measured. The mean concentrations of PCBs and p, p\u27-DDE found in the bind from Tasmania were 14 and 20ng/g in chicks and 150 and 89ng/g in adults respectively, on wet weight basis. The values of both the chemicals were found to be lower in chicks than in adults, and the degree of disparity in chemical levels between chicks and adults is greater in PCBs than in p, p\u27-DDE. Reflecting this, the DDE/PCB ratios were higher in chicks (1.3) than in adults (0.60). This is likely due to the greater accumulation of PCBs during the period of stay in the northern North Pacific feeding ground than in the southern South Pacific ones. The shearwaters from Japan and the northern North Pacific seem to be post-fledgling or yearlings, since their DDE/PCB ratios (1.1 and 1.2) were found to be nearly the same as those in chicks (1.3) from Tasmania. It is known that two types of metabolic enzymes (PB and MC type) are mainly associated with the PCB metabolism in higher animals. When compared the PCB compositions in the shearwaters from Japan and Tasmania, some members of PCBs metabolized mainly by the MC type enzyme systems were found to decrease or disappear in the bird from Japan, indicating that the activity of the MC type enzyme systems in the shearwater increased more than that of the PB type enzyme systems during the transequatorial migration of the bird

CHICK GROWTH AND MORTALITY OF SHORT-TAILED SHEARWATERS IN COMPARISON WITH SOOTY SHEARWATERS, AS A POSSIBLE INDEX OF FLUCTUATIONS OF AUSTRALIAN KRILL ABUNDANCE (Ninth Symposium on Polar Biology)

A semi-lunar rhythm appeared to be in the chick weight-growth curve of the Short-tailed Shearwaters (Puffinus tenuirostris) and exactly found in feeding of the Sooty Shearwaters (Puffinus griseus) to their chicks before desertion by parents. These rhythms may be caused by periodicity in the availability of the krill, especially Australian krill (Nyctiphanes australis), the main food for chicks of both shearwaters. Comparing the chick growths in Tasmania with their mortality occurrences in Japan in over a four year study of the Short-tailed Shearwaters, the best growth year of 1980 corresponded to a low mortality year, while a poor growth year of 1984 was situated at the peak of a mass mortality period of 1983-1985 in Japan. In the worst growth year of 1986, the mass mortality did not occur along Japan but Australia and the island of Guam. Therefore, the growth of chicks at the breeding site in Tasmania and mortality occurrences in Japan, Australia and Guam have a mutual relation, and they could be governed by the annual fluctuations in abundance of krill in Australian regions

Individual consistency in migratory behaviour of a pelagic seabird

Many animals migrate between breeding and wintering areas; however, whether each animal behaves consistently in space and time between consecutive years is less well understood. Furthermore, previous breeding state (successful or failed) is often not considered when attempting to understand consistent individual differences in behaviour that are likely to impact upon the subsequent behaviour. Between 2006 and 2010, we used geolocators to track the migratory movements of a pelagic seabird, the streaked shearwater Calonectris leucomelas, with individuals (N=46) being followed for two years or more, including 23 birds that had chicks in two seasons and 23 birds in just one season. All individuals, except for one bird, migrated to the same broad wintering areas, and their migratory route as well as the centre of wintering distribution did not change in relation to the previous breeding outcomes. Migration schedules (dates of departure from the breeding colony, southward and northward migrations, and first return to the colony) did not differ significantly between years for individuals that had chicks during both years, while failed individuals left the breeding colony and appeared to start the southward migration at an earlier date than the previous successful year. Nonetheless, the timing of the southward migration was consistent within individuals, including both males and females, over successive years regardless of the previous breeding outcome, and also the timing of first return back to the colony for females that had chicks in the both previous years and eggs in the both following season. This may imply the existence of individual-specific broad time schedules, possibly a circannual rhythm, though ecological conditions might affect the exact timing of the actual departure event. Our results present evidence for high levels of individually consistent behaviour for this pelagic seabird outside the breeding season

Gender Identification by Calls and Body Size of the Streaked Shearwater Examined by CHD Genes

Like most seabirds Streaked Shearwaters Calonectris leucomelas have sexually monomorphic plumage. Researchers have conveniently identified gender in the field by means of two types of calls, associated with dimorphism in body size. By molecular sexing analysis using the chromo-helicase-DNA-binding (CHD) genes, we determined the gender of Streaked Shearwaters in relation to call types and body size. We recorded the type of calls, measured body dimensions and collected non-invasive samples (buccal cells or feathers) of Streaked Shearwaters at two breeding islands. As obvious amplification to identify gender by polymerase chain reaction (PCR) could not be obtained at high rates using a known universal primer pair, we developed two new primer pairs to identify gender in this species; this enabled us to identify the gender of all of the samples. Without exception all males gave high-pitched calls, whereas all females gave low-pitched calls. Molecular evidence also confirmed morphometric differences between males and females. We, therefore, conclude that Streaked Shearwaters exhibit sexual dimorphism in body size and call type. Males are significantly larger than females, and males give high calls whereas females give low calls

Foraging areas of streaked shearwaters in relation to seasonal changes in the marine environment of the Northwestern Pacific: inter-colony and sex-related differences

As the spatial distribution of marine organisms is often affected by seasonal changes, pelagic seabirds may change their foraging areas in response to seasonal changes in the marine environment. Here, we examined the foraging area of streaked shearwaters Calonectris leucomelas, breeding at Sangan (SA) and Mikura Islands (MK), Japan, from spring to summer during pre-laying and incubation periods. Those colonies are located at the north and south of the Northwestern Pacific’s Kuroshio-Oyashio transition area where high seasonal temperature changes are observed, and where, consequently, birds may show comparable responses to such changes. Our results showed that streaked shearwaters from both colonies shifted their foraging areas northwards as the season progressed. The seasonal shift of foraging areas appeared to coincide with the movement pattern of pelagic fishes that migrate northward in association with the increase in water temperature. However, the pattern of seasonal movement differed between the 2 colonies; shearwaters from SA moved their foraging area along the coastal area of the Kuroshio-Oyashio transition, while those from MK moved along the Kuroshio Extension. Our results also indicated sex-related differences in this general pattern: females showed clear seasonal changes in foraging area, while males did not. During the pre-laying period males returned to the colony frequently to defend their nests or mates, and spent less time at sea. Our results suggest that streaked shearwaters changed their foraging areas in response to seasonal changes in the marine environment, although colony location and sex-related differences in reproductive roles may constrain the birds’ responses to seasonal change

Basal and field metabolic rates of Streaked Shearwater during the chick-rearing period

The energetics of adult Streaked Shearwaters Calonectris leucomelas during the chick-rearing period were examined on Awa Island, Japan, in 2008 and 2009. Basal metabolic rates (BMR) were quantified using an open-flow respirometry system and field metabolic rates (FMR) were quantified using a doubly labelled water (DLW) method. In addition, we used activity loggers to estimate time allocations for different activities at sea. BMR was 0.0124 kJ g(-1) h(-1) (+/- 0.0153, N=4) on average and corresponded to 54% of the value predicted from allometric equations. FMR was 0.0634 kJ g(-1) h(-1) (+/- 0.0331, N=3) and was equivalent to 5.1 times BMR, which was higher than values reported for albatrosses (2-4 times BMR). Shearwaters made 50.3 landings a day (+/- 9.8, N=12) and spent 44.8% (+/- 8.0, N=12) of their time sitting on the water. They landed on water approximately twice as often as albatrosses (which have been well-studied using DLW), but they both spent similar proportions of their time on water. Frequent landings at sea, and frequent takeoffs, may generate incremental energetic expenses because of the use of flapping flight; therefore, the Streaked Shearwater's relatively high FMR may be related to its high number of landings