Barrow’s Goldeneye (Bucephala islandica): revise global status?

BirdLife species factsheet for Bucephala islandica:


Barrow’s Goldeneye (Bucephala islandica) occurs mainly in the western montane region of North America, with smaller numbers in eastern Canada and Iceland. While some populations (e.g. in Iceland) are sedentary, others migrate in winter to estuaries and salt water along the Pacific coast of North America (del Hoyo et al. 1992). Barrow’s Goldeneye breeds on interior freshwater lakes and rivers in open or wooded country. Nests are placed in tree-holes or natural crevices, but also in artificial nest boxes (Eadie et al. 2000). In summer, it feeds mainly on insects and plant material, while the winter diet consists mainly of molluscs and crustaceans (del Hoyo et al. 1992).

Across its range, the species is hunted; harvesting rates are assumed to be sustainable, but might affect populations locally (Eadie et al. 2000). Moreover, old-growth forest with large or dead trees is converted for agro-industry plantations (Eadie et al. 2020). The subsequent loss of available nesting sites may have caused increased chick mortality due to greater distances separating nest holes from water (Eadie et al. 2000, Environment Canada 2013). Further threats include oil spills and exposure to pollutants in wintering grounds, which overlap with industrialised seaways such as the Gulf of St. Lawrence or Vancouver (Eadie et al. 2000).

Barrow’s Goldeneye is currently listed as Least Concern, with the population assumed to be increasing over the last few decades (BirdLife International 2020). Following the recent reassessment of North American birds by Partners in Flight (PiF) (2019), we have reviewed the new information, particularly regarding population trends. This has allowed us to reassess Barrow’s Goldeneye against IUCN Red List Categories and Criteria. As the PiF data are long-term trends (1970-2014), we have also used data from the North American Breeding Bird Survey (Sauer et al. 2017) to assess more recent trends over the period relevant to the Red List. Having completed this review, Barrow’s Goldeneye appears to warrant a change in Red List status. Therefore, we present here our reassessment against all criteria for the species.

Criterion A – Partners in Flight do not give a rate of population change for this species, but describe the population trend between 1970 and 2014 as uncertain or slowly decreasing (Partners in Flight 2019, see also Panjabi et al. 2019). Long-term trends from the North American Breeding Bird Survey (Sauer et al. 2017) are statistically non-significant due to data deficiency and therefore less conclusive. Sauer et al. (2017) report a large, though non-significant, decline of 56% between 1966 and 2015, assuming a constant rate of decline. However, the confidence intervals for this value range from 85% decline to 10% increase between 1966 and 2015.

Sauer et al. (2017) also hold historical year by year records, and so we can extrapolate population trends for any three generation period. Based on a generation length of 6.5 years (Bird et al. 2020)*, three generations ago is approximately 2000. Therefore, we can extrapolate the trends between 2000 and 2015 to 2020, in order to estimate the population trend over the past three generations. Between 2000 and 2015 the population has been, in general, decreasing with a non-significant, estimated annual decrease of 1.26% (4.91% decrease to 1.65% increase) (Sauer et al. 2017). Extrapolating the reduction to 2020, the rate of decline would amount to 22.2% (63.0% decrease to 38.3% increase), although this number is non-significant. Accounting for the large statistical uncertainty of the population trend, we can tentatively assume that the species is approaching the threshold for listing as Vulnerable (reduction of 30% over three generations). Year-by-year trends from Sauer et al. (2017) indicate that declines have been approaching the threshold of 30% over three generations since at least 1988 and are continuing at a similar rate to the present day.

Given these worrying trends, and the potentially large population crash over the last three generations, the species potentially warrants uplisting to a higher threat category than Least Concern. The data presented by the North American Breeding Bird Survey appear to suggest that the species could warrant listing as Near Threatened based on the rate of population decline over the last three generations, but the data deficiency highlighted for the species in the North American Breeding Bird Survey does make it difficult to accurately assess recent trends. Therefore, we request any further comments or information regarding recent population trends for the species. In the absence of this though, it may be appropriate to list the species as Near Threatened, approaching the threshold for listing as threatened under Criterion A2abcde+3bcde+4abcde.

Criterion B – The species’s range is far too large to warrant listing under this criterion (Extent of Occurrence [breeding] = 16,900,000 km2; Extent of Occurrence [non-breeding] = 21,400,000 km2). Barrow’s Goldeneye may be considered Least Concern under this criterion.

Criterion C – Partners in Flight estimate the population size to be 180,000 mature individuals (Partners in Flight 2019). Wetlands International (2018) report a global population of c.135,000-175,000 mature individuals. This is far too large to warrant listing as threatened, and Barrow’s Goldeneye may be considered Least Concern under this criterion.

Criterion D – The species’s population size and range are far too large to warrant listing as threatened, and Barrow’s Goldeneye may be considered Least Concern under this criterion.

Criterion E – To the best of our knowledge no quantitative analysis of extinction risk has been conducted for this species. Therefore, it cannot be assessed against this criterion.

Therefore, Barrow’s Goldeneye potentially warrants uplisting to Near Threatened, approaching the threshold for listing as threatenedunderCriterion A2abcde+3bcde+4abcde, but it is difficult to estimate recent trends based on the available information. We therefore request any further information about the magnitude of recent trends.

Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of its Red List status. Therefore, please make sure your comments are relevant to the discussion outlined in the topic. By submitting a comment, you confirm that you agree to the Comment Policy.

*Bird generation lengths are estimated using the methodology of Bird et al. (2020), as applied to parameter values updated for use in each IUCN Red List for birds reassessment cycle. Values used for the current assessment are available on request. We encourage people to contact us with additional or improved values for the following parameters; adult survival (true survival accounting for dispersal derived from an apparently stable population); mean age at first breeding; and maximum longevity (i.e. the biological maximum, hence values from captive individuals are acceptable).

An information booklet on the Red List Categories and Criteria can be downloaded here and the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here

References

Bird, J. P.; Martin, R.; Akçakaya, H. R.; Gilroy, J.; Burfield, I. J.; Garnett, S.; Symes, A.; Taylor, J.; Şekercioğlu, Ç. H.; Butchart, S. H. 2020. Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology online first view.

BirdLife International 2020. Species factsheet: Bucephala islandica. http://www.birdlife.org (Accessed: 04 March 2020).

del Hoyo, J.; Elliot, A.; Sargatal, J. 1992. Handbook of the Birds of the World, Vol. 1: Ostrich to Ducks. Lynx Edicions, Barcelona, Spain.

Eadie, J. M.; Savard, J. L.; Mallory, M. L. 2000. Barrow’s Goldeneye (Bucephala islandica), version 2.0. In: Poole, A. F.; Gill, F.B. (eds.) The Birds of North America. Cornell Lab of Ornithology, Ithaca, NY, U.S.A. https://doi.org/10.2173/bna.548 (Accessed: 05 December 2018).

Panjabi, A. O.; Easton, W.E.; Blancher, P. J.; Shaw, A. E.; Andres, A. B.; Beardmore, C. J.; Camfield, A. F.; Demarest, D. W.; Dettmers, R.; Keller, K. H.; K. V. Rosenberg; Will, T. 2019. Avian Conservation Assessment Database Handbook, Version 2019. Partners in Flight Technical Series No. 8. pif.birdconservancy.org/acad_handbook.pdf

Partners in Flight. 2019. Avian Conservation Assessment Database, version 2019. http://pif.birdconservancy.org/ACAD

Sauer, J. R.; Niven, D. K. ; Hines, J. E.; Ziolkowski, Jr, D. J.; Pardieck, K. L.; Fallon, J. E.; Link, W. A. 2017. The North American Breeding Bird Survey, Results and Analysis 1966 – 2015. Version 2.07.2017 USGS Patuxent Wildlife Research Center, Laurel, MD, U.S.A.

Wetlands International. 2018. Waterbird Population Estimates. wpe.wetlands.org. (Accessed: 05 December 2018).

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6 Responses to Barrow’s Goldeneye (Bucephala islandica): revise global status?

  1. H Glyn Young says:

    Arni Einarsson, Director Myvatn Research Station and guest professor, University of Iceland responded to IUCN SSC Threatened Waterfowl Specialist Group as follows:

    I have been monitoring the Icelandic BGO population for a very long time (1975 to present) with detailed counts in the main breeding and wintering area of Myvatn and Laxá. There are fluctuations, but no long-term trends that would prompt a change in listing status.

    Here is a link to a report in Icelandic with the most recent data. Spring numbers on p.25, moult numbers on p.34.
    http://nna.is/wp-content/uploads/2020/02/1902-Ástand-fuglastofna-%C3%AD-Þingeyjarsýslum-árið-2018_compressed1.pdf

  2. H Glyn Young says:

    Graham Sorenson
BC Projects Coordinator
Birds Canada/Oiseaux Canada
    responded to IUCN SSC Threatened Waterfowl Specialist Group as follows:

    Thank you for reaching out about Barrow’s Goldeneye, and I am glad the Birds Canada 20-year survey can help with this important IUCN decision. Below is a table from our soon-to-be-submitted manuscript with the Barrow’s Goldeneye results. Trend data is in percent change per year and decline was significant for the Pacific Coast (all BC outer coast), but not for the Salish Sea. The final trend is from 12-year trend data from the same survey published by Crewe et al.* Barrow’s Goldeneye data is based on December to February surveys for each year to capture the wintering population on the BC coast.

    Salish Sea Pacific Coast Salish Sea (Crewe et al. 2012*)
    Trend LCI UCI Trend LCI UCI Trend
    -2.37 -4.88 1.31 -8.15 -14.87 -0.60 -4.30

    We plan to submit this paper (below) next week, so it could be cited as “Manuscript submitted for publication”. I will be sure to share the manuscript when it is available in case it can be referenced for Barrow’s Goldeneye or other waterbirds that we include.

    Ethier, D.M., P.J.A. Davidson, G. Sorenson, C. Jardine, D. Lepage, K. Barry, K. Devitt, D.W. Bradley. (2020). Twenty years of coastal waterbird trends suggest regional patterns of environmental pressure in British Columbia, Canada. Manuscript in preparation.

    * Crewe, T., Barry, K., Davidson, P. & Lepage, D. 2012. Coastal waterbird population trends in the Strait of Georgia 1999– 2011: Results from the first 12 years of the British Columbia Coastal Waterbird Survey. British Columbia Birds 22: 8–35.

  3. H Glyn Young says:

    Jean-Pierre L Savard, Scientist Emeritus, Environment Canada
    responded to IUCN SSC Threatened Waterfowl Specialist Group as follows:

    Comments on Barrow’s Goldeneye status
    As we understand now, there are at least four distinct populations of Barrow’s Goldeneye (Pearce et al. 2014*): one wintering and breeding in Iceland (2000 birds), one in eastern North America (5000), one in Alaska (?; possibly around 4-10 000?) and one large one wintering along the Pacific Coast mostly southern Alaska, British Columbia, Washington State and up to California. Eadie et al. (2000) estimated the population at 100 000 to 150 000 but better estimates are likely available. The population for Alaska is uncertain as survey results combine Barrow’s and Common Goldeneyes and the % of each species is unknown. Also, Pearce et al. (2014)* indicated that there was a genetically distinct population in Alaska but its wintering distribution needs to be determined. There are probably more reliable estimates available for Alaska since our review in 2000 (Eadie et al. 2000). I would not trust any of the population estimates or trends derived from BBS results. I do not know on what data the PIFF assessment relied on for Barrow’s Goldeneye but I suspect that it could be based on BBS results as it is not an appropriate method to monitor Barrow’s Goldeneye trends and it yields unreliable estimates.

    Listing as Near Threatened based on the rate of population decline over the last three generations is an unjustified conclusion based on unreliable data. 1) the technique used (BBS), does not monitor well Barrow’s Goldeneye and likely yields spurious results; 2) Even when assuming the technique adequate, the results are not significant and highly variable. I see no reason here to change status based on the BBS data presented. Also, it addresses only 1 of the 4 populations.

    There is better and more reliable information available: Waterfowl surveys have been conducted regularly in British Columbia and that data should provide some estimates of trends and/or fluctuations in population size (see Sean Boyd and André Breault). Christmas Bird Count Results are available for several wintering areas along the Pacific Coast and should provide useful abundance indices if analyzed adequately.

    *Pearce, J. M., J. M. Eadie , J.-P. L. Savard , T. K. Christensen , J. Berdeen , E. Taylor , S. Boyd , A. Einarsson, and S. L. Talbot, 2014. Comparative population structure of cavity nesting sea ducks. Auk 131: 195-207.

  4. Red List Team (BirdLife International) says:

    Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested by so many people in commenting. The window for consultation is now closed. We will analyse and interpret the new information and post a preliminary decision on this species’s Red List status on this page in early July.

    Thank you once again,
    BirdLife Red List Team

  5. Red List Team (BirdLife International) says:

    The following comment was received via email from Michel Robert and Christine Lepage on 29th June. The information was taken into account during preliminary decision-making and is thus posted here for transparency:

    I know the eastern population of Barrow’s Goldeneye from having studied it during the 2000s, but I am not familiar with the recent trend of this population. I therefore asked my colleague Christine Lepage (waterfowl biologist at the Canadian Wildlife Service in Quebec; copied) to provide me with the most recent information on this subject. She referred me to the following report, which BirdLife International Red List Team should probably consult.

    Canadian Wildlife Service Waterfowl Committee. 2020. Population Status of Migratory Game Birds in Canada. November 2019. CWS Migratory Birds Regulatory Report Number 52.

    The report is available here: http://publications.gc.ca/collections/collection_2020/eccc/CW69-16-52-2019-eng.pdf

    Christine told me that the first sentence of section 6.9.1 is wrong, but the rest of the information is correct. Therefore, based on the 2017 winter survey, the eastern population of Barrow’s Goldeneye population would number about 7700 individuals, and it seems on the rise.

    Christine is also responsible of the Eastern Waterfowl Breeding Pair Survey conducted in Quebec (where most of the eastern population of Barrow’s Goldeneye do breed) and data from this survey indicate a positive trend for 1990-2019.

  6. Red List Team (BirdLife International) says:

    Preliminary proposal

    In informing the following decision, multiple factors were considered. Firstly, despite fluctuations in the Icelandic population, long-term trends (compiled over 1998-2018; Kolbeinsson et al. 2019) are likely not showing significant declines as previously considered. An annual decline rate of 4.3% (1999-2011), measured for the British Columbia Coastal Waterbird Survey however does translate to over 50% decline within a 3-generation period (19.5 years; Bird et al 2020), albeit declines at Salish Sea are not as significant (Crewe et al. 2012, G. Sorenson in litt. 2020). Furthermore, the species is suggested to have four distinct populations (Pearce et al. 2014), with the Partners in Flight (PiF 2019) and the American Breeding Bird Survey (Sauer et al. 2017) likely unrepresentative of the overall population. The eastern population of Canada is moreover considered to be increasing (latest survey recorded a 30% increase in 2017) with the western Canadian population showing long-term stability (Canadian Wildlife Service Waterfowl Committee 2020). Thus, taking into consideration the unsubstantiated declines beyond any localised reductions and fluctuations, as well as large uncertainty in data used for the initial forum topic, our preliminary proposal for the 2020 Red List would be to keep the Barrow’s Goldeneye as Least Concern.

    There is now a period for further comments until the final deadline in mid-July, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from the initial proposal.

    The final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021 (information on the IUCN Red List update process can be found here), following further checking of information relevant to the assessments by both BirdLife and IUCN.

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