Journal Articles
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Item Larger foraging area means greater fisheries interaction risk for juvenile yellow-eyed penguins in their sub-Antarctic range(Springer-Verlag GmbH, 2025-12-01) Muller CG; Chilvers BL; French RK; Battley PFSeabird foraging success is crucial for individual survival and therefore also for recruitment, breeding success, and population stability. However, there is limited information on the movements of juvenile seabirds, including penguins. This study investigates the foraging range of juvenile yellow-eyed penguins from Enderby Island, in the sub-Antarctic Auckland Islands, and their overlap with protected areas where commercial fishing is prohibited. Two juvenile penguins were tracked using GPS-Argos tags, and their movements were compared to those of breeding adults. Juveniles travelled up to 275.2 km from the colony, significantly farther than the maximum 46.7 km for breeding adults. Juveniles also used a much larger foraging area of 18,027 km2, compared to 738 km2 for adults. Only 7% of juvenile foraging occurred within the protected area, highlighting their potential vulnerability to commercial fishing activities. Juveniles had a 17% overlap with commercial fishing areas, compared to 4% for adults. The extensive foraging range and low overlap with protected areas suggest that juveniles are at higher risk of encountering threats, which may contribute to higher mortality rates. These findings underscore the need for conservation efforts to investigate and address threats in the broader foraging areas used by juveniles. Future research should track additional juvenile penguins and study prey availability to support effective conservation strategies for this endangered species.Item Bone marrow fat content analysis confirms starvation as a cause of death for Australasian bitterns (Botaurus poiciloptilus) in New Zealand(Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2025-03-20) Williams EM; Jarman T; Battley PF; Briskie JWildlife managers conserving threatened species rely on information about causes of population declines. Finding carcasses to record cause of death, sickness or injury in a timely manner is challenging. We used fat content in bone marrow from deceased Australasian bitterns (Botaurus poiciloptilus) to determine whether birds had starved by comparing results among 34 bitterns where the cause of death was assigned via independent autopsies. Fat content was near zero in the eight specimens that died of starvation. Many other specimens had depleted fat content, 17 of which were recorded as dying from impact trauma. This evaluation provided confidence to interpret our database of 126 Australasian bittern mortality records evaluated via autopsy or observation. The most common causes of death were impact trauma (56.3%; mainly vehicles and powerlines) and starvation (17.5%) with a further 5.8% having characteristics of both starvation and impact trauma raising the issue of whether starvation contributed to the deaths of individuals where impact trauma was the primary cause of death or vice versa. Although this dataset is biased by specimens more easily observed by the public, the occurrence of starved/near starved bitterns is of conservation concern and indicates wetland food supplies are likely under stress.Item Avian Influenza Virus Surveillance Across New Zealand and Its Subantarctic Islands Detects H1N9 in Migratory Shorebirds, but Not 2.3.4.4b HPAI H5N1(John Wiley and Sons Ltd, 2025-04) Waller SJ; Wierenga JR; Heremia L; Darnley JA; de Vries I; Dubrulle J; Robinson Z; Miller AK; Niebuhr CN; Melville DS; Schuckard R; Battley PF; Wille M; Alai B; Cole R; Cooper J; Ellenberg U; Elliott G; Faulkner J; Fischer JH; Fyfe J; Hay L; Houston D; Keys BC; Long J; Long R; Mattern T; McGovern H; McNutt L; Moore P; Neil O; Osborne J; Pagé A-S; Parker KA; Perry M; Philp B; Reid J; Rexer-Huber K; Russell JC; Sagar R; Ruru TT; Thompson T; Thomson L; Tinnemans J; Uddstrom L; Waipoua TA; Walker K; Whitehead E; Wickes C; Young MJ; McInnes K; Winter D; Geoghegan JLHighly pathogenic avian influenza (HPAI) virus subtype H5N1 has never been detected in New Zealand. The potential impact of this virus on New Zealand's wild birds would be catastrophic. To expand our knowledge of avian influenza viruses across New Zealand, we sampled wild aquatic birds from New Zealand, its outer islands and its subantarctic territories. Metatranscriptomic analysis of 700 individuals spanning 33 species revealed no detection of H5N1 during the annual 2023–2024 migration. A single detection of H1N9 in red knots (Calidris canutus) was noted. This study provides a baseline for expanding avian influenza virus monitoring in New Zealand.Item Predicting resilience of migratory birds to environmental change.(National Academy of Sciences, 2024-05-07) Lisovski S; Hoye BJ; Conklin JR; Battley PF; Fuller RA; Gosbell KB; Klaassen M; Benjamin Lee C; Murray NJ; Bauer S; Kareiva PThe pace and scale of environmental change represent major challenges to many organisms. Animals that move long distances, such as migratory birds, are especially vulnerable to change since they need chains of intact habitat along their migratory routes. Estimating the resilience of such species to environmental changes assists in targeting conservation efforts. We developed a migration modeling framework to predict past (1960s), present (2010s), and future (2060s) optimal migration strategies across five shorebird species (Scolopacidae) within the East Asian-Australasian Flyway, which has seen major habitat deterioration and loss over the last century, and compared these predictions to empirical tracks from the present. Our model captured the migration strategies of the five species and identified the changes in migrations needed to respond to habitat deterioration and climate change. Notably, the larger species, with single or few major stopover sites, need to establish new migration routes and strategies, while smaller species can buffer habitat loss by redistributing their stopover areas to novel or less-used sites. Comparing model predictions with empirical tracks also indicates that larger species with the stronger need for adaptations continue to migrate closer to the optimal routes of the past, before habitat deterioration accelerated. Our study not only quantifies the vulnerability of species in the face of global change but also explicitly reveals the extent of adaptations required to sustain their migrations. This modeling framework provides a tool for conservation planning that can accommodate the future needs of migratory species.Item Variable breeding success and its implication in the conservation of endangered yellow-eyed penguin (Megadyptes antipodes) at the New Zealand subantarctic Auckland Islands(John Wiley and Sons, Inc., 2024-04-19) Muller CG; Chilvers BL; French RK; Battley PFKnowledge of breeding success is essential for conservation, as it is required for monitoring populations and survival trends. Seabird reproductive success can be negatively affected by prey availability, marine-based stochasticity, extreme weather events, individual breeders' performance and direct threats such as disease, predation and fisheries interactions. The endangered yellow-eyed penguin (Megadyptes antipodes) is declining in mainland New Zealand, however, little is known about its breeding success in the subantarctic where the majority of the species breeds. Yellow-eyed penguin breeding success data were collected from a total of 167 nests on subantarctic Enderby Island, Auckland Islands, New Zealand, from the 2015 to 2017 breeding seasons. This included egg and chick mortality and fledging rates, plus a wider sample of the fledgling condition of 276 chicks. Fledging success was higher than in mainland New Zealand in some years, although chicks were smaller and lighter on average, highlighting the need for more information on juvenile survival probabilities in the subantarctic. Breeding success measures were similar in 2015 and 2016, but a large egg mortality in 2017 caused a significant reduction in breeding success that year. Such variability requires more investigation into the correlates of breeding success, including possible stressors such as foraging success, adverse weather and environmental effects, and pathogens. These results demonstrate the need for ongoing monitoring of yellow-eyed penguin breeding success across the subantarctic in order to establish baselines for normal variation and to determine whether anthropogenic (manageable) factors may be contributing to low productivity. This research highlights an important consideration for endangered species conservation; that breeding success may not be consistent over time, or across a species' entire range. Additional monitoring of all breeding populations should be carried out to ensure up-to-date information is available to inform conservation management decisions for the species.Item High dispersal ability versus migratory traditions: Fine-scale population structure and post-glacial colonisation in bar-tailed godwits.(John Wiley and Sons Ltd, 2024-07-06) Conklin JR; Verkuil YI; Lefebvre MJM; Battley PF; Bom RA; Gill RE; Hassell CJ; Ten Horn J; Ruthrauff DR; Tibbitts TL; Tomkovich PS; Warnock N; Piersma T; Fontaine MC; Hansen MMIn migratory animals, high mobility may reduce population structure through increased dispersal and enable adaptive responses to environmental change, whereas rigid migratory routines predict low dispersal, increased structure, and limited flexibility to respond to change. We explore the global population structure and phylogeographic history of the bar-tailed godwit, Limosa lapponica, a migratory shorebird known for making the longest non-stop flights of any landbird. Using nextRAD sequencing of 14,318 single-nucleotide polymorphisms and scenario-testing in an Approximate Bayesian Computation framework, we infer that bar-tailed godwits existed in two main lineages at the last glacial maximum, when much of their present-day breeding range persisted in a vast, unglaciated Siberian-Beringian refugium, followed by admixture of these lineages in the eastern Palearctic. Subsequently, population structure developed at both longitudinal extremes: in the east, a genetic cline exists across latitude in the Alaska breeding range of subspecies L. l. baueri; in the west, one lineage diversified into three extant subspecies L. l. lapponica, taymyrensis, and yamalensis, the former two of which migrate through previously glaciated western Europe. In the global range of this long-distance migrant, we found evidence of both (1) fidelity to rigid behavioural routines promoting fine-scale geographic population structure (in the east) and (2) flexibility to colonise recently available migratory flyways and non-breeding areas (in the west). Our results suggest that cultural traditions in highly mobile vertebrates can override the expected effects of high dispersal ability on population structure, and provide insights for the evolution and flexibility of some of the world's longest migrations.Item Global flyway evolution in red knots Calidris canutus and genetic evidence for a Nearctic refugium(John Wiley and Sons, Ltd, 2022-04) Conklin JR; Verkuil YI; Battley PF; Hassell CJ; ten Horn J; Johnson JA; Tomkovich PS; Baker AJ; Piersma T; Fontaine MC; qu YPresent-day ecology and population structure are the legacies of past climate and habitat perturbations, and this is particularly true for species that are widely distributed at high latitudes. The red knot, Calidris canutus, is an arctic-breeding, long-distance migratory shorebird with six recognized subspecies defined by differences in morphology, migration behavior, and annual cycle phenology, in a global distribution thought to have arisen just since the last glacial maximum (LGM). We used nextRAD sequencing of 10,881 single-nucleotide polymorphisms (SNPs) to assess the neutral genetic structure and phylogeographic history of 172 red knots representing all known global breeding populations. Using population genetics approaches, including model-based scenario-testing in an approximate Bayesian computation (ABC) framework, we infer that red knots derive from two main lineages that diverged ca. 34,000 years ago, and thus most probably persisted at the LGM in both Palearctic and Nearctic refugia, followed by at least two instances of secondary contact and admixture. Within two Beringian subspecies (C. c. roselaari and rogersi), we detected previously unknown genetic structure among sub-populations sharing a migratory flyway, reflecting additional complexity in the phylogeographic history of the region. Conversely, we found very weak genetic differentiation between two Nearctic populations (rufa and islandica) with clearly divergent migratory phenotypes and little or no apparent contact throughout the annual cycle. Together, these results suggest that relative gene flow among migratory populations reflects a complex interplay of historical, geographical, and ecological factors.Item Diet plasticity and links to changing foraging behaviour in the conservation of subantarctic yellow-eyed penguins (Megadyptes antipodes)(John Wiley and Sons, Ltd, 2022-05-17) Muller CG; Chilvers BL; French RK; Battley PF1. Diet is a key factor affecting seabird foraging behaviour, ultimately influencing survival, breeding success and long-term population viability. The density and distribution of prey species in the marine environment are influenced by many factors including climate effects such as El Niño southern oscillation and climate change that alter water temperature. 2. While poor quality diet has been implicated as a contributing factor in the decline of some mainland New Zealand yellow-eyed penguin (Megadyptes antipodes) populations, little is known about their diet in the subantarctic where the majority of the species breeds. 3. Blood and feather samples (n = 63) were collected for stable isotope analysis of diet from 25 individual birds breeding on subantarctic Enderby Island, Auckland Islands, New Zealand, from 2015 to 2018. 4. Diet data were analysed by factors such as breeding year, sex and foraging behaviour. Stable isotope analysis demonstrated significant changes in diet during each year of the study, which included both El Niño and La Niña conditions. 5. Diet during El Niño conditions comprised lower trophic level prey, which were more benthic, and found closer to shore than diet during La Niña. 6. Coupled with the reported variable breeding success of yellow-eyed penguins in the subantarctic, variable diet suggests prey availability is likely to be a limiting factor in some years. Prey availability is therefore expected to be a major influence on survival and breeding success of this endangered species in the future, particularly if the effects of climate change become more pronounced. 7. This research highlights an urgent conservation need to identify prey species utilized by the southern population, along with their distribution in time and space, and therefore also the effect of diet on long-term population stability.Item Shorebirds wintering in Southeast Asia demonstrate trans-Himalayan flights(Springer Nature Limited, 11/12/2020) Li D; Davidson G; Lisovski S; Battley PF; Ma Z; Yang S; How CB; Watkins D; Round P; Yee A; Srinivasan V; Teo C; Teo R; Loo A; Leong CC; Er KMany birds wintering in the Indian subcontinent fly across the Himalayas during migration, including Bar-headed Geese (Anser indicus), Demoiselle Cranes (Anthropoides virgo) and Ruddy Shelducks (Tadorna ferruginea). However, little is known about whether shorebirds migrate across the Himalayas from wintering grounds beyond the Indian subcontinent. Using geolocators and satellite tracking devices, we demonstrate for the first time that Common Redshanks (Tringa totanus) and Whimbrels (Numenius phaeopus) wintering in Singapore can directly fly over the Himalayas to reach breeding grounds in the Qinghai-Tibet Plateau and north-central Russia, respectively. The results also show that migratory shorebirds wintering in Southeast Asia can use both the Central Asian Flyway and the East Asian-Australasian Flyway. For Redshanks, westerly-breeding birds crossed the Himalayas while more eastern breeders migrated east of the Himalayas. For Whimbrels, the individual that crossed the Himalayas was probably from a different breeding population than others that migrated coastally up the East Asian-Australasian Flyway. The minimum required altitude of routes of trans-Himalayan Redshanks were no higher on average than those of eastern migrants, but geolocator temperature data indicate that birds departing Singapore flew at high elevations even when not required to by topography, suggesting that the Himalayan mountain range may be less of a barrier than assumed.Item Differences in body composition between urban and rural Mallards, Anas platyrhynchos(1/01/2020) Jarman TE; Gartrell BD; Battley PFAnthropogenic feeding of wildlife provides a valuable opportunity for people to engage with animals, but such feeding has the potential to be detrimental to the species involved. Ducks are frequently fed at urban ponds globally, yet the health impacts of an urban lifestyle for birds are poorly documented. We studied urban and rural Mallards (Anas platyrhynchos) in the Manawatū-Whanganui region (New Zealand). Mallards are opportunistic omnivores that have a phenotypically flexible gastrointestinal system. As urban Mallards consume considerable amounts of low-fibre, high carbohydrate foods via anthropogenic feeding, we predicted that urban Mallards would have smaller gastrointestinal tract organs and higher fat levels than rural ducks. We compared gross body composition of Mallards in a modified environment with high levels of feeding by humans and in rural habitats. We also evaluated other health-associated aspects including fat deposit size, liver fat content and haemosiderin (liver iron deposit) levels. Contrary to predictions, urban birds had larger gizzards and caeca and were no fatter than rural birds; rural birds additionally had larger pectoralis major muscles. These differences are probably associated with broader ecological and behavioural factors than with the provision of anthropogenic food per se [in particular the presence of hard foods (acorns and nuts) for urban birds, and higher flight activity of rural birds]. Longer caeca in urban birds could, however, relate to immunity rather than microbial fermentation of cellulose. Overall, while the nature of the local environment does affect Mallard physiology, no detrimental effects of urban living were evident in this study.