Fairy Tern Research Articles

Observations of chick feeding rates and parental defensive responses to disturbance at nests in the critically endangered New Zealand fairy tern/tara iti (Sternula nereis davisae)

ABSTRACT The New Zealand fairy tern/tara iti (Sternula nereis davisae; NZFT) is New Zealand’s most endangered bird, with approximately 40 individuals remaining. Due to previous poor breeding success, this species is on the brink of extinction. Nest failures occur because of adverse weather, predation, and potentially nest disturbance. We observed parental behaviour of 11 nesting pairs from November 2020 to January 2021 at three sites: Mangawhai, Waipu and Pakiri. Overall, avian predator disturbance was low at all nests, and most disturbance events were by interactions between conspecifics. Responses to conspecific disturbances were lowest for the three closely nesting pairs and highest for the three solitary nests. We measured the frequency of chick feeding and found feeding rates varied considerably between nests. Defensive response rates and feeding rates varied between nests but we found no relationship between the proportion of responses to disturbance and feeding rates. We found no relationship between feeding rate and tidal state. This could be due to our small sample size and the duration of our observation period (30 min). We urge future researchers to increase observation period time. With an understanding of feeding rates and disturbance, informed decisions can be made to support the conservation of NZFT.

Drivers of colony failure in a vulnerable coastal seabird, the Australian Fairy Tern (Sternula nereis nereis)

Context Understanding breeding success and site threat profiles is critical to conservation planning, particularly for species of conservation concern. Regular surveillance is fundamental to observing spatiotemporal changes at breeding colonies. Still, it can be challenging for species with broadly distributed, unpredictable populations susceptible to various threats. In these cases, cooperative networks and citizen science programs offer an opportunity to support monitoring and conservation efforts. Aims This study aimed to assess the outcomes, threats and sources of breeding failure at Australian Fairy Tern (Sternula nereis nereis) colonies. Methods Through collaborative surveillance, this study identified the outcomes and threats at 77 monitored colonies over five breeding seasons between 2017/18 and 2021/22. The leading causes of nest failure were then considered against the Recovery Plan for the Australian Fairy Tern to understand how the observed threats compare with the identified risks in this plan. Key results Nearly half (48%) of all colonies failed, with predation (32%) and inundation (27%) being the biggest causes of failure. At least 10 native and four invasive/domestic species contributed to the mortality of eggs, chicks, and/or adults or complete colony failure. Disturbance, including off-road vehicles, was identified as a recurring threat, impacting at least 30% of colonies. Conclusions These identified threats have the potential to drive population-level effects and were consistent with those identified under the Recovery Plan. Implications This study highlights the importance of developing practical solutions, including habitat protection, the control of invasive species and education programs to safeguard colonies and boost breeding success.

Data‐driven counterfactual evaluation of management outcomes to improve emergency conservation decisions

AbstractMonitoring is needed to assess conservation success and improve management, but naïve or simplistic interpretation of monitoring data can lead to poor decisions. We illustrate how to counter this risk by combining decision‐support tools and quantitative counterfactual analysis. We analyzed 20 years of egg rescue for tara iti (Sternula nereis davisae) in Aotearoa New Zealand. Survival is lower for rescued eggs; however, only eggs perceived as imminently threatened by predators or weather are rescued, so concluding that rescue is ineffective would be biased. Equally, simply assuming all rescued eggs would have died if left in situ is likely to be simplistic. Instead, we used the monitoring data itself to estimate statistical support for a wide space of uncertain counterfactuals about decisions and fate of rescued eggs. Results suggest under past management, rescuing and leaving eggs would have led to approximately the same overall fledging rate, because of likely imperfect threat assessment and low survival of rescued eggs to fledging. Managers are currently working to improve both parameters. Our approach avoids both naïve interpretation of observed outcomes and simplistic assumptions that management is always justified, using the same data to obtain unbiased quantitative estimates of counterfactual support.

Structured phylogeography and restricted gene flow among populations of Fairy Tern (Sternula nereis) across Australasia: implications for the endangered New Zealand population

The Fairy Tern Sternula nereis is an Australasian tern that breeds in Australia, New Caledonia and New Zealand, with the last having the smallest breeding population, listed as ‘Threatened – Nationally Critical’ by the New Zealand Department of Conservation. Here, we investigate the genetic relatedness and level of endemism (gene flow) of the New Zealand Fairy Tern S. n. davisae population compared with the larger breeding populations in Australia, S. n. nereis, and New Caledonia, S. n. exsul, using the NADH subunit 2 (ND2) region of the mitochondrial DNA. We found that the three main populations (n = 86) were genetically distinct, with a different fixed haplotype restricted to New Zealand (n = 15) and New Caledonia (n = 16), and that the estimated gene flow was low to zero, indicating no interbreeding between the populations. The current genetic evidence is consistent with observations of morphological and behavioural differences among the populations, and we suggest continued independent management of the population in New Zealand and further surveys and independent management of the New Caledonia population.

A long tern view: distribution of small terns (Sternula) in Western Australia and implications for their conservation

Recent observations confirm the Indo-Pacific Little Tern Sternula albifrons sinensis has been extending its breeding range in Western Australia in recent years, following a pattern documented in other tern and noddy species on the western coast of Australia. Nesting Indo-Pacific Little Terns have been recorded annually as far south as North West Cape since 2016. A similar southward shift in breeding range may have occurred during the last interglacial period and it is hypothesised that Little Terns isolated at the Houtman Abrolhos Islands during the following glacial period gave rise to the Australian Fairy Tern Sternula nereis nereis. The Australian Fairy Tern subsequently colonised the continental shelf from Dampier, Western Australia to the south-eastern states and then New Zealand as sea levels rose again during the Holocene. The two former sibling species are now sympatric between Dampier and North West Cape and interbreeding and hybridisation have the potential to occur in that area. Most jurisdictions require populations to be defined at the species or subspecies level in order to be listed and managed as threatened. However, relying on such taxonomic criteria has the potential to obscure the management of threats faced by each inter-breeding population unit. Approaches that identify and protect the sub-structure of superspecies and meta-populations might be more effective in the longer term.

Feeding ecology of a threatened coastal seabird across an inner shelf seascape

Feeding studies provide important information about animals and the environments in which they live. Yet little is known about the diet of the Australian Fairy Tern Sternula nereis nereis, despite the species being listed as threatened (Vulnerable) and in need of research. This study investigated the dietary composition of this bill-loading seabird, at three colony sites of an inner shelf seascape (two marine and one estuarine) using non-invasive digital photography and direct observations (number of observations [n] = 9854). Small surface schooling, inshore spawning fishes were the most important prey at all sites. Blue Sprat Spratelloides robustus, hardyheads (Atherinidae spp.), and garfishes Hyporhamphus spp. dominated the diet, contributing ≥75% of all prey at each site. The abundance of these fishes, whose spawning period overlapped the Fairy Tern breeding season in south-western Australia (October to February), is likely an important factor influencing the location of Fairy Tern colonies. Multivariate statistical analyses showed that dietary composition differed significantly among colony sites, breeding seasons, between courtship and chick feeding, and time of day. Blue Sprat, Beaked Salmon Gonorynchus greyi, and flyingfishes (Exocoetidae spp.) were present in greater proportions at Rottnest Island and Penguin Island (marine sites) than at Point Walter (estuarine). In contrast, hardyheads, Tailor Pomatomus saltatrix, and Yelloweye Mullet Aldrichetta forsteri were more common at Point Walter. Garfishes were around twice as important at Penguin Island than the other sites. Differences in habitat and fish species assemblages at each site may explain the observed spatial trends in dietary composition, while environmental factors, e.g. sea surface temperature and freshwater discharge, and natural interannual variability may explain the observed temporal trends in diet. Fish donated for courtship were ∼21% (12 mm) longer than those provisioned to chicks and the composition of prey in the diet of Fairy Terns differed between courtship and chick feeding at both Point Walter and Penguin Island. Differences in prey handling capabilities and nutritional requirements of adult females and chicks may explain these differences. Dietary composition differed significantly among diurnal periods at Point Walter and Penguin Island, with the greatest differences observed between morning and afternoon periods. At least 30 prey species were recorded, suggesting a degree of feeding opportunism. However, the large proportion of Blue Sprat, particularly at marine colony sites, highlights a potential vulnerability of Fairy Terns to changes in prey availability during their breeding period.

Using meta-population models to guide conservation action

Biodiversity conservation is limited by resources, data, and time for execution. To maximize efficacy, it is best if conservation plans are strategically evaluated for cost, feasibility, and likely impact prior to implementation. We present a framework to systematically examine the likely impact of proposed conservation plans for threatened taxa. As a case study of this framework we use the national Action Plan for Seabird Conservation in New Zealand and 27 threatened seabirds identified for conservation interventions. To evaluate impact, we applied a recently developed seabird meta-population viability analysis model (seabird mPVA) that employs the most current population and adjustable demographic data to assess threatened seabird viability at a global scale under various management scenarios. This publicly available, web-based tool is intended to meet the needs of threatened seabird managers at the initial phase of conservation planning. We used the seabird mPVA to model population trends and potential seabird viability gains from conservation actions that include: bycatch mitigation, invasive species removal, and seabird translocation prescribed in the action plan for individual species. Our model’s ranking of New Zealand seabirds by current quasi-extinction vulnerability roughly correlated with the seabirds’ IUCN Red List status and New Zealand Threat Classification System. We found modeled conservation impact of proposed actions and assigned priority to be generally positively correlated, but variable in magnitude. If all prescribed conservations actions were implemented, our model predicted significant mitigation of quasi-extinction risk for nine species (Antipodean Albatross, Auckland Island Shag, Black-fronted Tern, Fairy Tern, Rough-faced Shag, Northern Royal Albatross, Pitt Island Shag, Stewart Island Shag, Yellow-eyed Penguin). This approach, and our model, can be adapted to other taxonomic groups to provide a consistent framing for the prioritization of species for conservation investment and predictions about the benefits of specific conservation actions for those species.

Social facilitation for conservation planning: understanding fairy tern behavior and site selection in response to conspecific audio-visual cues

Simulated social facilitation techniques (e.g. decoys and call playbacks) are commonly used to attract seabirds to restored and artificially created nesting habitats. However, a lack of social stimuli and conspecific cueing at these habitats may limit the use of these sites, at least in the short term. Therefore, testing the effectiveness of simulated audio-visual cues for attracting gregarious birds is important for conservation planning. In this study, we (1) assessed whether call playback and decoys were associated with an increased likelihood of Australian fairy terns Sternula nereis nereis visiting potentially suitable nesting habitats; (2) tested their behavioral response to different cues; and (3) documented whether social facilitation had the potential to encourage colony establishment. A full cross-over study design consisting of all possible pairings of decoy and call playback treatments (control [no attractants], decoys, call playback, both decoys and playback), allocated as part of a random block design, was undertaken at 2 sites. Linear modeling suggested that call playback was important in explaining the time spent aerial prospecting as well as the maximum number of fairy terns aerial prospecting, although this only appeared to be the case for 1 of the 2 sites. Decoys, on the other hand, did not appear to have any effect on time spent aerial prospecting. The results from this study suggest that audio cues have the potential to encourage site selection by increasing social stimuli, but attractants may be required over several breeding seasons before colonies are established.

Applying a values-based decision process to facilitate comanagement of threatened species in Aotearoa New Zealand.

Ko koe ki tēnā, ko ahau ki tēnai kīwai o te kete (you at that, and I at this handle of the basket). This Māori (New Zealanders of indigenous descent) saying conveys the principle of cooperation-we achieve more through working together, rather than separately. Despite decades of calls to rectify cultural imbalance in conservation, threatened species management still relies overwhelmingly on ideas from Western science and on top-down implementation. Values-based approaches to decision making can be used to integrate indigenous peoples' values into species conservation in a more meaningful way. We used such a values-based method, structured decision making, to develop comanagement of pekapeka (Mystacina tuberculata) (short-tailed bat) and tara iti (Sternula nereis davisae) (Fairy Tern) between Māori and Pākehā (New Zealanders of European descent). We implemented this framework in a series of workshops in which facilitated discussions were used to gather expert knowledge to predict outcomes and make management recommendations. For both species, stakeholders clearly stated their values as fundamental objectives from the start, which allowed alternative strategies to be devised that naturally addressed their diverse values, including mātauranga Māori (Māori knowledge and perspectives). On this shared basis, all partners willingly engaged in the process, and decisions were largely agreed to by all. Most expectations of conflicts between values of Western science and Māori culture were unfounded. Where required, positive compromises were made by jointly developing alternative strategies. The values-based process successfully taha wairua taha tangata (brought both worlds together to achieve the objective) through codeveloped recovery strategies. This approach challenges the traditional model of scientists first preparing management plans focused on biological objectives, then consulting indigenous groups for approval. We recommend values-based approaches, such as structured decision making, as powerful methods for development of comanagement conservation plans between different peoples.

Persistent organic pollutants in sea bird eggs from the Indian Ocean's Mascarene Basin

We report the concentrations of persistent organic pollutants (POPs) in seabird eggs from St. Brandon's Atoll, a tropical island system in the western Indian Ocean. Ten eggs each of sooty terns (Onychoprion fuscatus), fairy terns (Gygis alba), and common noddies (Anous stolidus) were collected from the atoll. For a terrestrial reference, we analysed three feral chicken (Gallus gallus domesticus) eggs from the same location. Sooty tern eggs contained the highest mean concentrations of three chemical classes: ƩCHL3 (0.21 ng/g wm; wet mass), ƩPCB10 (1.5 ng/g wm), and ƩPBDE6 (1.1 ng/g wm). Fairy tern eggs contained the highest mean concentrations of HCB (0.68 ng/g wm) and ƩCHB5 (0.83 ng/g wm). The chicken eggs contained the highest mean concentrations of ƩDDT3 (2.6 ng/g wm), while common noddy eggs contained the highest mean concentrations of ƩHCH2 (0.5 ng/g wm). We surmise that the differences in chemical composition between species reflect different pollutant compositions in prey from the bird's different foraging ranges. The sooty terns foraging offshore contained higher POPs concentrations than the nearshore-foraging common noddies. Fairy tern eggs contained intermediate concentrations, commensurate with their intermediate foraging. Inter-island differences in contaminant concentrations were seen between eggs of the common noddies from St. Brandon's Atoll and Rodrigues Island, 520 km to the south-east. Concentrations of contaminants found in this study were lower than values quantified by other studies, making St. Brandon's Atoll an ideal reference site to monitor background concentrations of POPs in the tropical Indian Ocean.

Inferred predation of Fairy Tern eggs by Ruddy Turnstones at Rottnest Island, Western Australia, an internationally significant shorebird site

Ruddy Turnstones Arenaria interpres have been identified as egg-predators at seabird and shorebird colonies, including gull and tern colonies in the tropics and Northern Hemisphere. The Australian Fairy Tern Sternula nereis nereis is a threatened (Environment Protection and Biodiversity Conservation Act 1999: Vulnerable) coastal seabird, whose breeding behaviour and ecology expose it to a wide range of threats. This study describes inferred predation on Fairy Tern eggs at a small breeding colony on Rottnest Island, Western Australia, by Ruddy Turnstones, a previously unsuspected predator for thisspecies. Unlike the behavioural response shown towards Silver Gulls Larus novaehollandiae and Australian Ravens Corvus coronoides, which includes collective group defence and dive-bombing, Fairy Terns showed a lack of aggression towards Turnstones within the colony. The lack of a behavioural response suggests that the Terns did not recognise the Turnstones as predators, which may increase the risk of egg-predation. This study suggests that we should be alert to threats from unsuspected predators, which have the potential to reduce the breeding success of this Vulnerable tern.

Application of a novel banding technique and photographic recapture to describe plumage development and behaviour of juvenile Fairy Terns

The Australian Fairy Tern Sternula nereis nereis is a seabird that breeds along the coast and whose small populations are dispersed over vast stretches of the Australian seaboard and nearshore islands. In recent years, citizen science programs have been developed to bolster monitoring efforts to better understand breeding success and identify site threat profiles. The development of protocols that facilitate the collection of consistent measurements is important for long-term monitoring of this threatened (Vulnerable) species. This study describes plumage development and age-related behaviour in juvenile Australian Fairy Terns using direct observations and photographic recapture of individually marked birds. This information may be used as the basis for the development of a field ageing guide, enabling the collection of standardised information on colony demographics and juvenile development. A temporary colour-banding study was trialled by painting nail varnish onto 15 Australian Bird and Bat Banding Scheme (ABBBS) incoloy bands, avoiding the need to band nestlings with additional readable or PVC colour-bands. The varnish remained intact, albeit chipped, on four surviving birds that were resighted ≤80 days after banding, enabling the identification of individuals away from the colony site, without the need for recapture. The temporary marking of ABBBS bands using nail varnish offered an effective short-term solution for identifying individual juvenile Fairy Terns in the field and for describing plumage changes over a period of c. 3 months.

The secret life of Fairy Terns: breeding chronology and life history observations of Sternula nereis nereis in south-western Australia

This research describes the breeding ecology, behaviour and substrate preferences of the Australian Fairy Tern, Sternula nereis nereis, in four colonies around Perth, Western Australia between 2018 and 2020. Extensive field observations, supported by a bird banding study and sunrise to sunset video recording were used at colony and roosting sites to determine the processes of mating, colony formation, egg-laying and incubation periods, post-hatching care and breeding success (fledglings per pair). At a colony in North Fremantle, the median nest spacing was 0.71m (mean± s.e.= 0.89±0.05m), which increased over time. Birds establishing nests within a week of the first eggs being laid selected sites with significantly higher percentage beach shell cover (73.5±4.5%) than those laying later in the season (58.2±7.9%) and on average, birds selected sites with higher shell cover (64.9±2.8%, n=114) than a random sample of sites within the colony (53.7±4.4%, n=44). Incubation periods ranged from 17 to 26 days (n=86, mean=21±0.17 days). Incubation shift duration was highly variable, with both sexes contributing, almost equally to the care of the brood (mean=1.27±6.11h). Chicks fledged 21–23 (mean=22±0.21, n=10) days following hatching, with all banded juveniles leaving the colony site within 8 days of fledgling. The information gained from this research helps inform conservation strategies for this vulnerable species, where management interventions are frequently necessary to prevent population decline.

Seasonal movements and metapopulation structure of the Australian fairy tern in Western Australia

The Australian fairy tern metapopulation in Western Australian is distributed over an extensive stretch of coastline (≤2500km). Using mark–recapture and coordinated community-based resightings of marked birds, this study reveals important insights into the seasonal movement, interchange and key locations used by Australian fairy terns. The Western Australian metapopulation consists of a widely distributed, partially migratory spring/summer-breeding population and a smaller, winter-breeding, sedentary population on the Pilbara coast. The spring/summer-breeding population winters, primarily, around the northern islands of the Houtman Abrolhos, before migrating to breeding areas as far south as Point Malcolm on the eastern south coast and as far north as the Ningaloo coast (Exmouth). Thus, in Western Australia, Australian fairy terns from the same population reproduce in both tropical and temperate marine regions. Associations between birds, persisting over multiple seasons, suggest that group adherence may be an important behavioural trait of these small terns. Based on the recent use of breeding sites and the likely spatial extent of exchange of breeding adults and natal recruits, seven ‘neighbourhoods’ are proposed, which likely represent the best units to underpin a conservation strategy for this threatened coastal seabird. The combination of small population size, strong area fidelity and the potential for strong group adherence among individuals are important considerations for the development of effective conservation strategies in Western Australia. Maintaining the Australian fairy tern population size within the suggested management units is critical for the long-term conservation of this species.

Species limits and English names in the genus Gygis (Laridae)

The alpha taxonomy of the genus Gygis is controversial, with limited molecular studies contradicting distributional and phenotypic evidence that two Pacific forms, larger candida and smaller microrhyncha are separate species. This paper reviews evidence from the subfossil record, morphology, distribution and hybridisation, and vocalisations to conclude that Gygis comprises three biological species, nominate alba in the Atlantic, and two Pacific species. It also reviews historical English vernacular names and proposes ‘fairytern’ as a group name for these members of the newly recognised subfamily Gyginae. This name maintains popular tradition but requires a minor exception to some current naming conventions. Proposed English names are Atlantic Fairytern, Common Fairytern, and Little Fairytern. The name White Tern should now apply only to the historical single species, and Fairy Tern remains for Sternula nereis.

Perfluoroalkyl substances (PFAS) in tern eggs from St. Brandon's Atoll, Indian Ocean

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic fluorinated compounds of concern for human and environmental health. There is no data on PFAS concentrations in marine bird eggs from the Western Indian Ocean. We analysed eight PFAS in eggs of fairy terns (Gygis alba), sooty terns (Onychoprion fuscatus), and common noddies (Anous stolidus) from St. Brandon's Atoll. Fairy tern eggs contained the highest concentrations, followed by sooty terns and common noddies. Perfluoroundecanoic acid (PFUdA) had the highest mean concentration (2.3 ng/g wm), followed by perfluorooctane sulfonic acid (PFOS) (2.0 ng/g wm), and perfluorononanoic acid (PFNA) (0.93 ng/g wm) in fairy tern eggs. Concentrations of all PFAS were lower than values found in literature. PFOS and PFOA concentrations were three orders of magnitude lower than toxicity reference values and levels of lowest-observed-adverse-effect-level concentrations. Eggs from St. Brandon's would be useful to monitor background changes on a regional and perhaps global scale.

Cat Gets Its Tern: A Case Study of Predation on a Threatened Coastal Seabird.

Simple SummaryFeral cats living completely independently of people are, unequivocally, agents of wildlife decline, which is linked to the local extinction of numerous bird, mammal and reptile species worldwide. However, evidence of the impact of pet and semi-feral (stray) cats on wildlife is somewhat limited, possibly due to the rapidity with which predation events occur. This study highlights the impact of a semi-feral cat on a threatened seabird colony of Australian Fairy Terns, Sternula nereis nereis, in Mandurah, south-western Australia. Evidence for significant predator-induced mortality, the alteration of the natural behavior of nesting birds in response to a persistent predator, and the complete reproductive failure of 111 nests—due, largely, to predation by a single, desexed, semi-feral cat—is presented. Trap-neuter-release was proposed as a humane response to tackle cat overpopulation but it fails to address the recurrent depredations on native wildlife that occur post-release. This case-study demonstrates that desexed, free-roaming cats remain a significant threat to wildlife and can lead to swift population declines and the local extirpation of native species.Domestic cats have a cosmopolitan distribution, commonly residing in urban, suburban and peri-urban environments that are also critical for biodiversity conservation. This study describes the impact of a desexed, free-roaming cat on the behavior of a threatened coastal seabird, the Australian Fairy Tern, Sternula nereis nereis, in Mandurah, south-western Australia. Wildlife cameras and direct observations of cat incursions into the tern colony at night, decapitated carcasses of adult terns, dead, injured or missing tern chicks, and cat tracks and scats around the colony provided strong evidence of cat predation, which led to an initial change in nesting behavior and, ultimately, colony abandonment and the reproductive failure of 111 nests. The death of six breeding terns from the population was a considerable loss for this threatened species and had the potential to limit population growth. This study highlights the significant negative impacts of free-roaming cats on wildlife and the need for monitoring and controlling cats at sites managed for species conservation. It also provides strong evidence against the practice of trap-neuter-release programs and demonstrates that desexed cats can continue to negatively impact wildlife post-release directly through predation, but also indirectly through fundamental changes in prey behavior and a reduction in parental care.

Keeping it regular: Development of thermoregulation in four tropical seabird species

The thermoregulatory capacity of a species can determine which climatic niche it occupies. Its development in avian chicks is influenced by numerous factors. Furthermore, it is suggested that altricial chicks develop their thermoregulatory capacity post-hatching, while precocial chicks develop aspects of this in the egg. We investigated the development of thermoregulation of four co-occurring seabird species in the Seychelles; namely white, ground-nesting white-tailed tropicbirds (Phaethon lepturus) and tree-nesting fairy terns (Gygis alba); and dark plumaged, tree-nesting lesser noddies (Anous tenuirostris) and ground- and tree-nesting brown noddies (A. stolidus). White-tailed tropicbirds have semi-altricial chicks, while the remaining species have semi-precocial chicks. Cloacal temperatures (Tb) were measured at five day intervals from newly hatched chicks and compared over time, and with adult Tbs. Initial Tbs of all chicks, except fairy terns, were lower than those taken when chicks were older. Brooding cessation generally coincided with feather development, as did an increase in Tb. Mean chick Tb was significantly lower than mean adult Tb for all species, but only white-tailed tropicbird and brown noddy chicks in tree nests differed significantly from mean adult Tb when chick Tb at five day intervals were considered. There was a significant interactive effect of nest site and age on brown noddy chick Tb, but chick colour did not have a significant effect on Tb. However, brown noddy chicks on dune crests maintained a constant Tb sooner than chicks in tree nests. Our results demonstrate that tropical seabird species have a more delayed onset of thermoregulatory capabilities when compared with those in temperate environments, perhaps as nest sites are less thermally challenging. Nest microhabitats and behavioural thermoregulation, are likely more important during early chick development for these species.

Seagull Lake, Western Eyre Peninsula, South Australia: A Saline Lake to Benefit from Climate Change?

As a result of climate change, salt lakes on Eyre Peninsula are predicted to have shorter hydroperiods. Already there are salinity increases due to land use changes, so major decreases in biodiversity are expected. The likely situation is different however for the few lakes receiving waters via marine springs, with Seagull Lake, 20 km south of Streaky Bay, the best example. It has been thoroughly surveyed as a base to assess future changes. This lake originated about 6000 years ago as a marine bay, since occluded by coastal dunes. Its waters are a balance between meteoric sources, groundwater and marine water via springs with seasonal fluctuations due to input variations and evaporation. A conceptual model closely matched field observations. Presently the main lake varied in salinity seasonally from 75 to 200 g/L, with the spring virtually constant at 37–40 g/L. Plants in the lake and its palustrine margins numbered 25 species arranged into 18 floristic associations. Of particular interest are the marine alga Acetabularia peniculus in the floodout lakelet from the spring, the vulnerable shrub Tecticornia flabelliformis at limited suitable habitat locations on the lake floor margins and the alga Achanthes breviceps in the soaks on beach rock. Invertebrates number 37 species, of which 17 are marine, confined to the springs, including two cnidarians, two polychaetes, four crustaceans and eight molluscs. The lake itself supports a few widespread continental saline species, and other freshwater-derived invertebrates in the peripheral lakelets. A fish, Leptatherina presbyteroides, lives permanently in the main spring and spreads to the lake in winter. Thirty-nine species of birds have been seen on the lake including regular species like the Banded Stilt, Red-capped Plover and Red-necked Stint. Sea Gulls and Fairy Terns breed on the lake islands. We postulate that with decreased rainfall and sea level rise, the marine springs will deliver more water to the lake, making it permanent and of lower salinity. But ultimately with evaporation of these new waters, the lake will eventually become a salt flat. Plant distribution will be severely disrupted, with the palustrine herblands moving landwards, Sarcocornia quinqueflora likely to overwhelm the vulnerable Tecticornia flabelliformis, and Zostera? mucronata of the spring expanding its domain initially but ultimately retreating back to the spring. Invertebrate and bird diversity will initially increase, but as the lake becomes a salt flat diversity will finally decrease towards zero.

Foraging ecology and choice of feeding habitat in the New Zealand Fairy TernSternula nereis davisae

SummaryNo published information is available on the foraging ecology and choice of feeding habitat of New Zealand’s rarest breeding bird: the New Zealand Fairy Tern (NZFT)Sternula nereis davisae. To address this gap, we conducted an assessment of the largest remaining breeding population at Mangawhai Harbour, Northland, New Zealand, during the chick-rearing period of the 2010/2011 breeding season. We combined visual tracking of birds with prey surveys and stable isotope analyses, and we present the first quantitative assessment of NZFT foraging. We recorded 405 foraging dives that show NZFT foraging habitat includes the water edges, shallow channels, and pools on the tidal flats of mangrove-lined (Avicennia marinavar.resinifera) parts of the estuary; tidal pools on mud- and sandflats in the mid-estuary and lower harbour; the shallow margins of the dredged main channel in the lower harbour; the oxbow lagoons on the sand spit; and coastal shallows. Our study identifies the mangrove-lined highly tidal and shallow mid-estuary and the lagoon on the sand spit as foraging hotspots for the Mangawhai breeding population of the NZFT. The prey survey employed a seine-net sampling method at identified NZFT foraging sites and yielded 4,367 prey-sized fish of 11 species, two of which had not previously been reported in Mangawhai Harbour, as well as numerous shrimps. The most abundant fish were gobies of the genusFavonigobius. Our stable isotope results highlight gobies as the most important prey for NZFT chick rearing, also indicating that flounderRhombosoleasp. contribute to NZFT diet. We raise the possibility that shrimps may also constitute a substantial diet component for NZFT, potentially providing up to 21% of diet mass for adult birds. While our results provide a first basis to understanding the feeding ecology of NZFT during their breeding season in order to facilitate conservation planning, further research is required to address inter-annual variation and to identify key foraging grounds for this Critically Endangered bird at other breeding sites.