Academic literature on the topic 'Sooty shearwater'

Burrowing seabirds are vulnerable to extirpation by introduced predators such as rats, but much evidence of predation is circumstantial. On Taukihepa, an island off southern New Zealand, two possible predators exist with sooty shearwaters (Puffinus griseus): the weka (Gallirallus australis), a large rail, and the ship rat (Rattus rattus), both introduced to the island. It was expected that chick predation would be principally by weka, the much larger of the two predators. To measure losses of sooty shearwater chicks to weka or rats, nests were monitored with burrow-scopes at six sites in the summers of 2003–04 and 2004–05. In three of the sites rats were removed on 4-ha grids by trapping. In the other three sites rats were not trapped. In addition, weka were removed from all six sites in 2005. Concurrent diet analysis of weka and rat stomachs was undertaken as well as stable isotopic analysis (δ13C, δ15N) of samples from rats and weka. These were compared with possible prey items including sooty shearwaters. Additional stable isotope samples were taken from Pacific rats (Rattus exulans), a small rat species present with weka and sooty shearwaters on nearby Moginui Island. Weka diet comprised ~40% of bird remains by volume and calculations using Isosource, an isotopic source portioning model, estimated sooty shearwaters contributed 59% (range: 15–71%) of weka diet during the sooty shearwater chick-raising period. Ship rats, in contrast, had very depleted δ13C isotope signatures compared with sooty shearwaters and bird remains contributed <9% of diet by volume, with Isosource calculations suggesting that ship rats consumed more passerine birds (mean: 30%; range 5–51%) than sooty shearwaters (mean 24%; range: 0–44%). In both summers, more chicks were lost on sites from which rats had been removed than on control sites. When weka were removed in 2005, fewer chicks were lost than in 2004 and significantly fewer weka-killed chicks were found on weka-removal sites than on non-removal sites. Weka were the principal predator of sooty shearwater chicks, depredating an estimated 9.9% of nests. Combining several techniques quantified the loss and identified the principal predator of a seabird in decline.

The distribution and abundance of seabirds was documented at sea in the Gulf of Carpentaria in December 1990 and November 1991. Of the 17 species recorded, only the crested tern, least frigatebird, brown booby and streaked shearwater were widespread. The first three species were seen mainly in coastal waters; streaked shearwaters were seen only in the central north-western gulf. The common tern, roseate tern, little tern, sooty tern, black-naped tern, common noddy and greater frigatebird were either sparsely distributed or uncommon. The list includes five terrestrial species. The distribution of the seabirds is discussed in relation to proximity to breeding and roosting sites, food availability, the effects of discards from prawn trawling, and water currents.

Marine predator–prey interactions are often influenced by oceanographic processes that aggregate prey. We examined density distributions of seabirds and prey fish associated with the Columbia River plume to determine whether variation in plume size (i.e., volume or surface area) or location influences predator–prey interactions. Common murre (Uria aalge), sooty shearwater (Ardenna grisea), and forage fish, including northern anchovy (Engraulis mordax) and juvenile salmon (Oncorhynchus spp.), occurred disproportionately in plume waters relative to adjacent marine waters. Water clarity, an indicator of plume-influenced waters, was a significant predictor of seabird and prey densities throughout the survey area. Murres occurred within 20 km of the plume center of gravity, whereas shearwaters occurred ∼100 km north of the plume center of gravity, concurrent with the highest densities of prey fish. Global indices of collocation were relatively low between murres and prey compared with the high values between shearwaters and prey. Seabird densities were negatively correlated with plume size, suggesting that seabirds concentrate in the plume to maximize foraging effort. We conclude that variation in Columbia River plume size and location influences predator distributions, which increases predation pressure on prey, including threatened salmonid species.

Breeding colonies of sooty shearwaters ('muttonbird', tïtï, Puffinus griseus) on mainland New Zealand have declined in recent years. New data on burrow occupancy and colony productivity for seven sooty shearwater breeding colonies on the coast of Otago, New Zealand for the 1996–97 and 1997–98 breeding seasons are presented and analysed as part of a five-year data set. Detection of a burrow's occupants using a fibre-optic burrowscope may underestimate absolute occupancy rates, but is still of value in the analysis of trends. Detection probabilities estimated by the novel use of mark–recapture models corresponded with those of previous studies of the technique's accuracy. Mainland declines are associated with a lack of control of introduced mammalian predators at most mainland colonies superimposed on a global pattern of decline in the species' abundance. Large numbers of recovered carcasses and an absence of burrow activity at two small mainland colonies show the decline to extinction of these colonies over the five years of collecting data. At one mainland colony with intensive predator control, survival rates and parameter variances are comparable with those found on a predator-free offshore island. All other mainland colonies showed negligible breeding success. There was a significant positive relationship between egg survival and an index of relative adult survival, with an apparent threshold below which few eggs hatch. Adult survival during the breeding season is likely to be the most important parameter in maintaining a colony's viability.

Rakiura Maori continue a centuries old harvest of titi chicks (sooty shearwater, Puffinus griseus) which is governed primarily by Traditional Ecological Knowledge (TEK). The sustainability of titi harvesting is of high cultural, social and ecological importance. Some commentators view contemporary use of TEK as insufficient to ensure sustainability because it is no longer intact, too passive, and/or potentially inadequate to meet new ecological and technical challenges. Such assertions have been made in the absence of detailed description of TEK and associated social mechanisms. This thesis describes Rakiura Maori TEK practices and management systems that are in place and asks whether such systems are effective today, and whether they will remain effective in future. Ecological, social and cultural factors are intertwined in cultural wildlife harvests so the methodology used was a combination of quantitative ecological methods and semi-directive interviews of 20 experienced harvesting elders. The research also used ecological science to evaluate potential harvest monitoring methods and to determine what sets the limits on harvest. These ecological studies focused on harvesting by four families on Putauhinu Island in 1997-1999. Harvest is divided into two parts. In the first period (�nanao�) chicks are extracted from breeding burrows during daytime. In the second period (�rama�) chicks are captured at night when they have emerged from burrows. Nanao harvest rates only increased slightly with increasing chick densities and birders� harvest rates varied in their sensitivities to changing chick density. Although harvest rates can only provide a general index of population change a monitoring panel, with careful selection of participants, may be the only feasible way to assess population trend and thereby harvest sustainability or the resource�s response to changed management. Rakiura Maori harvesting practice constitutes common property resource management based on birthright and a system of traditional rules. Protection of island habitat and adult birds, and temporal restricitions on harvest are considered most important. Legislation and a belief system of reciprocity and connection to ancestors and environment aid enforcement of the rules. Ecological knowledge is learnt through observation, hands-on experience and storytelling. Younger Rakiura Maori now spend less time harvesting which puts pressure on the transmission of knowledge. Paradoxically, use of modern technology for harvesting aids transfer of essential skills because it is easier and faster to learn, thereby contributing to the continuance of a culturally important harvest. Limits on harvest are passive, with the numbers of chicks taken determined by the time spent harvesting and processing. Processing is more limiting during the rama period. Future innovations that decrease the time to process each chick during rama could greatly increase the total number of chicks caught. Recently introduced motorised plucking machines decrease the time required to pluck each chick. However, on Putauhinu Island, use of plucking machines did not increase the number of chicks harvested, indicating social mechanisms were also limiting. Elders identified changing values between the generations, which may reduce the future strength of social limitations on harvest pressure. Global climate change may reduce the predicability of traditional knowledge. Rakiura Maori have identified this risk and sought to examine ecological science as a tool to complement traditional knowledge for monitoring harvest sustainability. Climate change, declining tītī numbers and potential changes in technology or markets all threaten the effectiveness of current social limits to harvest. Rakiura Maori have previously shown the ability to adapt and must look to add resilience to their institutions to ensure we keep the titi forever.

The sooty shearwater (also known as the muttonbird, Titi, Puffinus griseus) is a long-lived super-abundant, burrow nesting petrel, harvested by Rakiura Maori from breeding colonies, located in southern New Zealand. The harvest is culturally defining and enormously important for Rakiura Maori. The work in this thesis contributes to the Kia Mau te Titi Mo Ake Tonu Atu Research Project being undertaken by Rakiura Maori and the University of Otago, towards assessing ongoing sustainability of the harvest and future threats. Analyses of eight muttonbirder harvest records spanning, 1938 to 2004, show that harvest rates demonstrate, systematic commonalities in seasonal patterns and broad-scale consistency in trends of chick abundance and quality across harvested islands. If co-ordinated and well replicated, harvest records offer Rakiura Maori a low-cost and effective monitoring tool of sooty shearwater reproductive success and long-term population abundance. Hunt tallies provide additional evidence of a dramatic reduction in sooty shearwater abundance from the late 1980s that was also detected by counts from boats off the western seaboard of the USA. A conservative estimate of overall decline in hunt success across diaries, for the period 1972 to 2004, is 1.89 % (CI₉₅ 1.14 to 2.65) per annum, a total reduction of 39.2%. The harvesting records show a sooty shearwater mortality event occurred just prior to the 1993-breeding season at the same time as a severe negative anomaly in both the Pacific Decadal Oscillation and Southern Oscillation Indices. The hunting diaries show a decoupling of chick size with harvest success in the early 1990s. This resulted from a decline in harvest success and an increase in its variability, while chick size remained correlated with changing chick abundance and maintained its pre-1990 average. Long- lived seabirds maintain high survival by skipping breeding and abandoning breeding attempts when oceanic conditions deteriorate, increasing variability in chick abundance is also evidence of pressure on adult survivorship. The multiple diaries confirm these were major demographic events not confined to a single island. My survival estimates for The Snares and Whenua Hou were very high 0.952 (0.896-0.979) compared to earlier estimates for this species. Transience at the colonies is high due to the presence ofjuvenile and pre-breeding birds. Both naturally high survival and the large number of transient pre-breeders indicate sooty shearwater are more resilient to harvest than earlier survival models suggested. There was no evidence for directional change in sooty shearwater breeding phenology over 49-years of harvest. Climate fluctuation/change is therefore apparently not altering egg-laying. Peak fledging occurred fairly consistently in the 2nd of May (IQR = 2.91 days). Yearly variability in emergence occurs primarily due to provisioning and localized fledging conditions. Larger chick size was strongly correlated with delayed fledging and is consistent with the traditional ecological knowledge of the birders. There was no evidence for chicks becoming smaller or that years with starving chicks were more common, so increasing mismatch of breeding with optimal forage was not indicated. The past proportion of birders over the last 20 years (1985 - 2005) has been ~2% all of Rakiura Maori. Approximately 376 birders participated in the 2006 season with an estimated of overall harvest intensity 19.4% (CI₉₅ = 13.8 - 24.2%) and a total catch of 381,000 (CI₉₅ = 262,257 - 487,186) chicks. This study found evidence that catch rates reduced with increasing birder competition partially mitigating effects on harvest pressure. The combined effects of potential climate change on bird abundance and increased harvester competition suggests that the proportion of Rakiura Maori whom choose to bird is likely to decrease as tallies reduce and cost recovery becomes more difficult. Rakiura Maori have for many years cherished and maintained their islands and implemented protective measures to safeguarded titi breeding habitat. Future harvest management will have additional issues to contend with, but Rakiura Maori are necessarily confronting these issues as the titi culture rests on the maintenance of their taonga. The information presented in this thesis shows that combining science and traditional knowledge is a powerful tool for managing harvest sustainability.

This chapter begins by illustrating how the author saw a Sooty shearwater while standing on a boat with no land on the horizon. The bird reminds the author of the freedom a child-body has. Other pelagic species also move the author. Working as a naturalist aboard a small boat in the Gulf of California one winter, after hours on deck staring at water, the author spotted a Xantus's murrelet. The author loves sea birds because of their differences from “regular” land-based birds. But preference is for the many species of pelagic birds who hide their lives on land. The ones like prions who bury themselves to lay an egg, whose chicks hunker in the dark until fledging or trundle out to sea before they can even fly. These birds know how dangerous earth can be.