Modelling the potential non-breeding distribution of Spoon-billed Sandpiper Calidris pygmaea

SummaryThe Spoon-billed Sandpiper Calidris pygmaea is a ‘Critically Endangered’ migratory shorebird. The species faces an array of threats in its non-breeding range, making conservation intervention essential. However, conservation efforts are reliant on identifying the species’ key stopover and wintering sites. Using Maximum Entropy models, we predicted Spoon-billed Sandpiper distribution across the non-breeding range, using data from recent field surveys and satellite tracking. Model outputs suggest only a limited number of stopover sites are suitable for migrating birds, with sites in the Yellow Sea and on the Jiangsu coast in China highlighted as particularly important. All the previously known core wintering sites were identified by the model including the Ganges-Brahmaputra Delta, Nan Thar Island and the Gulf of Mottama. In addition, the model highlighted sites subsequently found to be occupied, and pinpointed potential new sites meriting investigation, notably on Borneo and Sulawesi, and in parts of India and the Philippines. A comparison between the areas identified as most likely to be occupied and protected areas showed that very few locations are covered by conservation designations. Known sites must be managed for conservation as a priority, and potential new sites should be surveyed as soon as is feasible to assess occupancy status. Site protection should take place in concert with conservation interventions including habitat management, discouraging hunting, and fostering alternative livelihoods.Field surveys in Russian non-breeding grounds were supported by RSPB, MHS and NABU. Field surveys in Gulf of Mottama partly supported by BBC Wildlife Fund. Satellite tagging data collection partly supported by The Biodiversity Investigation, Observation and Assessment Program (2019 - 2023) of the Ministry of Ecology and Environment of China, RSPB and a private donor. Bangladesh Spoon-billed Sandpiper Conservation Project’s fieldwork in Meghna Estuary (2015 - 2016) supported by RSPB. Data collection by EL partly supported by Basic research program (budgetary funds), projects number АААА-А19-119022190168-8 and АААА-А19-119021990093-8). PT supported by Moscow State University Grant for Leading Scientific Schools "Depository of the Living Systems" in the MSU Development Program framework. TBL was funded by the Natural Environment Research Council UK, and the IAPETUS Doctoral Training Partnership

Eggs in the Freezer: Energetic Consequences of Nest Site and Nest Design in Arctic Breeding Shorebirds

Birds construct nests for several reasons. For species that breed in the Arctic, the insulative properties of nests are very important. Incubation is costly there and due to an increasing surface to volume ratio, more so in smaller species. Small species are therefore more likely to place their nests in thermally favourable microhabitats and/or to invest more in nest insulation than large species. To test this hypothesis, we examined characteristics of nests of six Arctic breeding shorebird species. All species chose thermally favourable nesting sites in a higher proportion than expected on the basis of habitat availability. Site choice did not differ between species. Depth to frozen ground, measured near the nests, decreased in the course of the season at similar non-species-specific speeds, but this depth increased with species size. Nest cup depth and nest scrape depth (nest cup without the lining) were unrelated to body mass (we applied an exponent of 0.73, to account for metabolic activity of the differently sized species). Cup depth divided by diameter2 was used as a measure of nest cup shape. Small species had narrow and deep nests, while large species had wide shallow nests. The thickness of nest lining varied between 0.1 cm and 7.6 cm, and decreased significantly with body mass. We reconstruct the combined effect of different nest properties on the egg cooling coefficient using previously published quantitative relationships. The predicted effect of nest cup depth and lining depth on heat loss to the frozen ground did not correlate with body mass, but the sheltering effect of nest cup diameter against wind and the effects of lining material on the cooling coefficient increased with body mass. Our results suggest that small arctic shorebirds invest more in the insulation of their nests than large species

Effect of age at release on the post-release survival of head-started Spoon-billed Sandpipers

Headstarting, in which eggs are taken from the nests of wild birds, incubated artificially and the chicks reared in captivity before release to the wild, has been conducted since 2012 on the subarctic breeding grounds of the Critically-Endangered Spoon-billed Sandpiper Calidris pygmaea in an attempt to increase the production of fledged juveniles. We used resightings of individually-marked head-started juveniles after they had moved away from the natal release site to assess differences in post-release survival of birds released at the same site on the same date in relation to differences in the age at which they were released. There was an unexpected significant tendency for survival to decrease with increasing age at release, both for survival beyond the period immediately after release and also to one year old. This effect of age at release is likely to be causal because multiple logistic regression analyses indicated that potential confounding effects of year of release and hatching date did not have statistically significant effects when included in models along with age at release. The mechanism underlying the effect of age at release is unknown, but possible explanations include increased stress or risk of disease or injury of individuals kept captive for longer periods. Our results suggest that releasing all juveniles at the typical age at fledging of wild birds (ca. 17 days) would improve post-release survival substantially. Possible further research could include experiments in which groups of juveniles matched for hatching date and other covariates are released at different ages in the same year and correlative studies of the condition and health of captive juveniles in relation to previous avicultural interventions and the duration of time in captivity.BirdsRussia, Royal Society for the Protection of Birds, Wildfowl and Wetlands Trust, Mangrove Conservation Fund and other donors provided financial support for headstarting and associated studies

Evaluating the Impact of Headstarting on the Critically Endangered Spoon-Billed Sandpiper Calidris pygmaea

Peer reviewed: TrueFunder: Wildfowl and Wetlands Trust (WWT)Funder: Royal Society for the Protection of Birds (RSPB)Funder: Mangrove Conservation Fund (MCF)Headstarting is a conservation approach that suggests offering an advantage to a population by improving egg production, survival of embryos and/or juveniles. In this article, we are providing the quantitative data obtained during 10 years for different stages of headstarting (production of eggs per pair, hatching and fledging rates) and the resulting impact (survival to maturity, philopatry rate, sex ratio, apparent survival, growth/decline rate) on the local population of the critically endangered spoon-billed sandpiper. We have shown that headstarting gains are reduced over time from fledging to long-term recruitment to the local breeding population. The possible reasons for this reduction are suggested and discussed. The unexpected finding was a drastic difference in sex ratios of the new recruits, which was about even for headstarting, but strongly male-biased for wild-reared birds. We suggest this happens due to increased mortality of female chicks in nature. We have also shown only headstarting could stop the global decline of the species, particularly once the suggested improvements are implemented and the number of pairs involved is scaled up. Headstarting also had a significant social effect due to the involvement of increasing numbers of people both in the local communities in Chukotka and from many countries on the flyway into searching for marked birds and learning about waders, raising awareness about ecological problems on the East Asian–Australasian Flyway. Thus, it has made the need for conservation actions on the flyway more obvious and sensible.</jats:p

Mismatch-induced growth reductions in a clade of Arctic-breeding shorebirds are rarely mitigated by increasing temperatures

In seasonal environments subject to climate change, organisms typically show phenological changes. As these changes are usually stronger in organisms at lower trophic levels than those at higher trophic levels, mismatches between consumers and their prey may occur during the consumers’ reproduction period. While in some species a trophic mismatch induces reductions in offspring growth, this is not always the case. This variation may be caused by the relative strength of the mismatch, or by mitigating factors like increased temperature-reducing energetic costs. We investigated the response of chick growth rate to arthropod abundance and temperature for six populations of ecologically similar shorebirds breedingin the Arctic and sub-Arctic (four subspecies of Red Knot Calidris canutus, Great Knot C. tenuirostris and Surfbird C. virgata). In general, chicks experienced growth benefits (measured as a condition index) when hatching before the seasonal peak in arthropod abundance, and growth reductions when hatching after the peak. The moment in the season at which growth reductions occurred varied between populations, likely depending on whether food was limiting growth before or after the peak. Higher temperatures led to faster growth on average, but could only compensate for increasing trophic mismatch for the population experiencing the coldest conditions. We did not find changes in the timing of peaks in arthropod availability across the study years, possibly because our series of observations was relatively short; timing of hatching displayed no change over the years either. Our results suggest that a trend in trophic mismatches may not yet be evident; however, we show Arctic-breeding shorebirds to be vulnerable to this phenomenon and vulnerability to depend on seasonal prey dynamics.</p

New estimates of the size and trend of the world population of the spoon-billed sandpiper using three independent statistical models

A single formal estimate of the size of the world population of the Critically Endangered Spoon-billed Sandpiper Calidris pygmaea has been published. This used a Lincoln-Petersen method, which combined a global mark-resighting analysis with a scan survey to estimate the proportion of birds with individual marks observed at a post-breeding moult and migration stopover site in Jiangsu Province, China. We report nine further repetitions of this procedure, which we call Method A, giving ten world population estimates in all, during the 6-year period 2014–2019. Four of these estimates use scan surveys from Jiangsu in the post-breeding adult moult period and six are from the non-breeding season (November–February) at three widely-separated sites in Bangladesh, Myanmar and South China. The weighted mean world population size at the end of the breeding season, based upon all ten surveys, was 490 mature individuals (95% C.L. 360–620) and 773 individuals of all ages (95% C.L. 569–978), which is similar to the single previous Method A estimate (420 mature individuals), but considerably more precise. We also report results from two independent but low-precision methods: one based upon published non-breeding season counts and the non-breeding season localities of satellite-tagged birds (Method B) and the other based upon mark-recapture analysis of birds marked as unfledged chicks and recaptured as migrating juveniles (Method C). These two methods gave estimates within the range 471 to 922 mature individuals, depending upon assumptions. The trend of Method A population size estimates with time during the short study period was a decline at a mean rate of 8% per year, but this did not differ significantly from zero (no change). The precision of this estimate of population trend was low, but its rate is of similar magnitude to the 9% per year decline during 2009–2016, derived from surveys of the local population at the most important known non-breeding season site in Myanmar. Hence, although the rapid population decline indicated by surveys of breeding populations observed prior to 2009 (mean 26% decline per year) has probably slowed as a result of conservation efforts, our results indicate that the species should continue to be listed as Critically Endangered.We thank the students of Nanjing Normal University who have helped in the ringing of Spoon-billed Sandpipers and other shorebirds in Jiangsu Province, China: Zhao Fangzheng, Ge Xiaohui, Hu Dongfang, Liu Wei, Zhang Yi, Chen Peng, Tai Deyun, Wu Yuhao, Xu Xue, Yao Wenjia, Wang Hao, Qian Nven; We thank the researchers from the Jiangsu Academy of Forestry: Ding Jingjing, Wang Xuan. We are grateful to the China Bird Banding Center, which supports the banding programme in China. Data collection was partly supported by The Biodiversity Investigation and Assessment program (2019–2023) of the Ministry of Ecology and Environment of China. Research and conservation work by BirdsRussia in Chukotka and Kamchatka was supported by RSPB, NABU, MHS, WWT, Chukotka administration and many other funding sources. The work of E. Lappo was partly supported by Basic Research Program (budgetary funds), project No.0148-2019-0007. Russian authors are thankful to all BirdsRussia team members, including numerous volunteers from abroad, who helped with nest searching and supported the catching and individual marking of birds. Svetlana and Roman Belogorodtsevy and other people of Meinypil’gyno are thanked for their help during our fieldwork. Richard Hearn, Kane Brides and Pyae-Phyo Aung made valuable contributions to the fieldwork. We thank all the surveyors and photographers who have undertaken surveys or sent in records of marked birds and Vivian Fu, Ding Li Yong and Paul Insua-Cao for detailed advice on past survey locations. We thank Nicola Crockford and Christoph Zöckler for advice and comments. We are grateful to Paul Howey of Microwave Telemetry Inc. for developing the miniature satellite tags used in this study and responding to our requests for variations of the design. We thank the (Animal Welfare) Ethics Advisory Committee of the Royal Society for the Protection of Birds for scrutinising our application to attach satellite tags to Spoon-billed Sandpipers