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
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).