Taiko Research Articles

Stable Isotope Analysis Reveals Feral Cat Diet on the Chatham Islands

Feral cats are significant invasive predators in New Zealand and are widely associated with drastic declines in breeding seabird populations. Suppressing or controlling feral cat populations has been a major conservation focus in large island ecosystems, including Rēkohu (The Chatham Islands). The Chatham Island tāiko (Pterodroma magentae) naturally persists in a single breeding colony after experiencing rapid population declines in the 19th & 20th centuries. A deeper understanding of feral cat ecology and diet is required to ensure control methods maximise conservation benefits. We used stable isotope analysis of feral cat fur, claws, and bone collagen to investigate the ecology and diet of feral cats trapped in the Tuku Nature Reserve on Rēkohu (The Chatham Islands). We predicted that cat diet would be highly specialised among individuals but relatively stable over time. To estimate the relative contribution of available prey to feral cat diets we employed Bayesian mixing models. Standard ellipse areas were used to understand diet stability over time. Our results have implications for the ongoing management of the Chatham Island Taiko.
 Supervised by: Cilla Wehi

Influence of Species-Specific Feeding Ecology on Mercury Concentrations in Seabirds Breeding on the Chatham Islands, New Zealand.

Mercury (Hg) is a toxic metal that accumulates in organisms and biomagnifies along food webs; hence, long-lived predators such as seabirds are at risk as a result of high Hg bioaccumulation. Seabirds have been widely used to monitor the contamination of marine ecosystems. In the present study, we investigated Hg concentrations in blood, muscle, and feathers of 7 procellariform seabirds breeding on the Chatham Islands, New Zealand. Using bulk and compound-specific stable isotope ratios of carbon and nitrogen as a proxy of trophic position and distribution, we also tested whether Hg contamination is related to the species-specific feeding ecology. Mercury exposure varied widely within the seabird community. The highest contaminated species, the Magenta petrel, had approximately 29 times more Hg in its blood than the broad-billed prion, and approximately 35 times more Hg in its feathers than the grey-backed storm petrel. Variations of Hg concentrations in blood and feathers were significantly and positively linked to feeding habitats and trophic position, highlighting the occurrence of efficient Hg biomagnification processes along the food web. Species and feeding habitats were the 2 main drivers of Hg exposure within the seabird community. The Pterodroma species had high blood and feather Hg concentrations, which can be caused by their specific physiology and/or because of their foraging behavior during the interbreeding period (i.e., from the Tasman Sea to the Humboldt Current system). These 2 threatened species are at risk of suffering detrimental effects from Hg contamination and further studies are required to investigate potential negative impacts, especially on their reproduction capability. Environ Toxicol Chem 2021;40:454-472. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Molecular evidence for the identity of the Magenta petrel

A lone petrel was shot from the decks of an Italian warship (the 'Magenta') while it was sailing the South Pacific Ocean in 1867, far from land. The species, unknown to science, was named the 'Magenta petrel' (Procellariiformes, Procellariidae, Pterodroma magentae). No other specimens of this bird were collected and the species it represented remained a complete enigma for over 100years. We compared DNA sequence of the mitochondrial cytochrome b gene from the Magenta petrel to that of other petrels using phylogenetic methods and ancient DNA techniques. Our results strongly suggest that the Magenta petrel specimen is a Chatham Island taiko. Furthermore, given the collection location of the Magenta petrel, our finding indicates that the Chatham Island taiko forages far into the Pacific Ocean (near South America). This has implications for the conservation of the taiko, one of the world's rarest seabirds.

New Genetic Approach to Detecting Individuals of Rare and Endangered Species

Many rare and endangered species are difficult to locate, observe, and study. Consequently, many individuals, breeding pairs, and even populations of such species could remain undetected. Genetic markers can potentially be used to detect the existence of undiscovered individuals and populations, and we propose a method to do so that requires 3 conditions. First, sampling of the known population(s) of the target species must be comprehensive. Second, the species must display a reasonable level of philopatry and genetic structuring. Third, individuals must be able to be caught outside of breeding locations (e.g., at courtship or feeding areas, in flight), and the level of recapture must be reasonably high. We applied our method to the Chatham Island Taiko (Pterodroma magentae), one of the world's most endangered seabirds. We sequenced the Taiko mitochondrial cytochrome b gene and both copies of a fragment of the duplicated domain I of the control region. Twenty-one haplotypes were revealed, including 4 (19%) not found in birds at known burrows. These results suggest there are more burrow groups yet to be located. The species is a pelagic gadfly petrel that inhabits land only in the breeding season during which it is nocturnal and nests in burrows. Taiko burrows are situated in dense forest in a remote area of Chatham Island, and are consequently difficult to locate and study. It is important that all Taiko burrows be discovered to enable monitoring and protection of the birds from exotic predators.

Ancient genetic variation in one of the world's rarest seabirds

The Chatham Island Taiko (Tchaik, Pterodroma magentae) is one of the world's rarest seabirds. In the past there were millions of breeding pairs of Taiko and it was the most abundant burrowing petrel on Chatham Island. The present population consists of just 120-150 birds, including only 8-15 breeding pairs. Surprisingly high genetic variation was revealed by DNA sequencing of almost every known adult Taiko (N=90). Given the massive population decline, genetic variation may have been even larger in the past. Therefore, we investigated past genetic diversity by sequencing regions of the mitochondrial cytochrome b gene in 44 ancient Taiko bones. We identified a total of 12 haplotypes in Taiko. Eight haplotypes were revealed in the ancient DNA: four were unique to the bones and four corresponded to those found in the modern Taiko population. Surprisingly, despite the critically endangered status of the Taiko, no significant reduction in mitochondrial DNA haplotype diversity was observed between ancient samples (N=44) and modern adult Taiko (N=90). The modern population may have however lost four haplotypes present in the ancient populations.

Excess of unpaired males in one of the World's most endangered seabirds, the Chatham Island taiko Pterodroma magentae

The Chatham Island taiko Pterodroma magentae (tchaik) is one of the World's most endangered seabirds with a population size of between 120–150 individuals that includes only 8–15 breeding pairs. Molecular techniques were used to identify the sex of taiko, which is difficult to assign morphologically. Blood samples were obtained from almost the entire known living population and from some birds now thought to be dead. We report an approximately even sex ratio in taiko chicks and adults associated with breeding burrows, but a large male‐biased ratio in non‐breeding adult birds caught on the ground. This finding suggests that unpaired males may be having difficulty in attracting females to burrows and that this situation may be an example of the Allee effect, that reduced density of potential mates acts to decrease population productivity. Identification of the sex of taiko using a molecular technique has important implications for the conservation management of this critically endangered species, including the future transfer of taiko chicks to a predator‐excluded breeding site.

Excess of unpaired males in one of the World's most endangered seabirds, the Chatham Island taiko Pterodroma magentae

Excess of unpaired males in one of the World's most endangered seabirds, the Chatham Island taiko Pterodroma magentae

High mitochondrial and nuclear genetic diversity in one of the world’s most endangered seabirds, the Chatham Island Taiko (Pterodroma magentae)

Interpreting the levels of genetic diversity in organisms with diverse life and population histories can be difficult. The processes and mechanisms regulating this diversity are complex and still poorly understood. However, endangered species typically have low genetic variation as a consequence of the effects of genetic drift in small populations. In this study we examine genetic variation in the critically endangered Chatham Island Taiko (Tchaik, Pterodroma magentae), one of the world’s rarest seabirds. The Taiko has a very small population size of between 120 and 150 individuals, including just 8–15 breeding pairs. We report surprisingly high mitochondrial and nuclear genetic diversity in this critically endangered long-lived species. We hypothesise that the present Taiko population has retained a significant proportion of its past genetic diversity. However, it is also possible that undiscovered birds are breeding in unknown areas, which could increase the population size estimate. Importantly, from a conservation perspective, we show that the high level of variation is unlikely to be maintained in the future since chicks currently being born have only a limited number of the mitochondrial DNA haplotypes found in adults. Reduced genetic variation will mean that our ability to infer past events and the population history of Taiko using genetics could soon be lost and the power to determine, for example, parentage and other close order relationships will be diminished. Therefore, the maintenance of genetic diversity in future generations is an important consideration for conservation management of the Taiko.

Non‐breeding behaviour of Magenta Petrels Pterodroma magentae at Chatham Island, New Zealand

Magenta Petrels Pterodroma magentae were caught at light‐attraction stations on southwest Chatham Island, New Zealand, and most were fitted with transmitters. Of 52 captured since 1993, 71% were males, and all 36 tracked adequately proved to be non‐breeders in the breeding season of capture. Our data indicated no sex bias in their probability of being captured at lights. Males provided 86% of trackings, and 87% of trackings of birds flying over the breeding area were males. Males landed 118 times; females 13 times. Only males were found on the ground, by night and day, apparently unassociated with burrows (three with and ten without transmitters), but subsequently digging burrows (n = 8). Of 19 birds banded as fledglings up to 2000, males were first recaptured nearing 4 years old (at lights and on the ground) and a female nearing 6 years old (in burrow). Among 37 fledglings, the sex ratio was even. Nine tracked males occupied burrows, as did two females, but the latter were older recaptures (10+ and 25+ years old). It appears that only males claimed existing, or dug new, burrows. They then attracted a mate to the burrow by means unknown, but from among females frequenting an inshore courtship area near the colony, or occasionally flying over the colony, at night. Females established in burrows, but then losing their mate, were able to re‐mate there, by calling from near the burrow or by attracting a mate in flight or from the postulated inshore courtship area. Both sexes sometimes took years to pair or re‐mate, possibly reflecting the dearth of available mates.

Coexistence of two species of Halipeurus (Phthiraptera) on Chatham Island taiko (Pterodroma magentae) (Aves)

Feather lice (Phthiraptera) were collected from 14 Chatham Island taiko (Pterodroma magentae). These included two species of Halipeurus (Philopteridae) in the ratio of two H. procellariae to one H. theresae. So far as we know, the regular occurrence of two Halipeurus species on a host is unique. H. procellariae is likely to have been acquired from the taiko's ancestors, but H. theresae probably derives from a secondary infestation through close association of the host with Chatham petrels (Pterodroma axillaris), probably in mixed breeding colonies. From sub‐fossil evidence, Chatham petrels formerly bred on the main Chatham Island, to which P. magentae has, from such evidence, always been restricted.

SUBFOSSIL PETREL BONES FROM THE CHATHAM ISLANDS

SummaryThe breeding community of petrels on the Chatham Islands has previously seemed curiously poor compared to that of analogous stations in the Indian Ocean or South Atlantic (14 species compared with 18 in the Tristan‐Gough group). Examination of subfossil deposits from the Chatham Islands probably dating from the early stages of human colonization which occurred within the last few hundred years reveals remains of at least 20 petrels, all of which except one may well have bred in the past, without including storm petrels, of which two species are still known to breed while others may also have bred in the past. The grand total of at least 21 breeding species, many apparently in vast numbers, would probably make the archipelago the most important breeding station for petrels in the world at the time of the first human colonization. It seems possible that in addition to the present breeding species the following may have bred: at least one endemic species of gadfly petrel, the Magenta Petrel Pterodroma magentae, and local populations of at least two other gadfly petrels, two shearwaters of the genus Procellaria and two of the genus Puffinus and a sooty albatross of the genus Phoebetria. Small populations of these, and perhaps other undetected species as well, may still survive in inaccessible places.