Horned Grebe Podiceps auritus breeds in both the Palearctic (from Iceland and the Baltic to Kamchatka, wintering from the North Sea to the Caspian Sea and off E Asia) and the Nearctic (from C Alaska to C Canada and NW & NC USA, wintering from the Aleutian Islands south to California and from Nova Scotia south to Texas; Llimona et al. 2014). It is currently listed as Least Concern, because when last assessed it was not thought to approach the thresholds for Vulnerable under any of the IUCN Red List criteria.
Globally, it has an extremely large range in both the breeding season (>16 million km2) and in winter (>4 million km2), and hence does not approach the thresholds for Vulnerable under the range size criteria (B and D2). Its population size is also very large (239,000–583,000 individuals; Wetlands International 2012), and hence does not approach the thresholds for Vulnerable under the population size criteria (C and D1). Therefore, the only potentially relevant criterion is A, which relates to reductions in population size. Until recently, the population was thought to be declining slowly, but not sufficiently rapidly to approach the threshold for listing as Vulnerable under criterion A (at least a 30% decline over ten years or three generations, whichever is longer).
New data collated from across Europe for the European Red List of Birds (BirdLife International 2015) indicate that the species has declined significantly in recent years. A combination of official data reported by 27 EU Member States to the European Commission under Article 12 of the EU Birds Directive and comparable data from other European countries, provided by BirdLife Partners and other leading national ornithologists, suggests that the European population has declined overall by 25–30% over the last three generations (21.3 years, based on a generation length estimated by BirdLife to be 7.1 years). Consequently, the species is now classified as Near Threatened at European level (BirdLife International 2015).
Based on the latest population estimates (Wetlands International 2012), however, Europe holds <10% of the global population, with a similar proportion in Asia; the trend of the E Asian population is unknown, but numbers recorded wintering in Caspian Sea are apparently declining.
Globally, its status depends on trends in North America, which holds >80% of the global population, and where it has undergone a large and statistically significant decrease (76% decline between 1966–2005, based on data from Breeding Bird Survey (BBS) and/or Christmas Bird Count (CBC); Butcher & Niven 2007). In 2009, the species was designated as being of special concern in Canada (which holds >90% of the North American breeding range), owing to a significant decline caused by threats including wetland degradation, nest predation and oil spills (COSEWIC 2009). The precise rate of decline varies according to whether the BBS or CBC data are used, and whether trends are calculated using over the long-term or short-term, but overall it is highly likely that the population has declined by >30% over the last three generations (COSEWIC 2009). On this basis, the species appears to qualify for uplisting to Vulnerable under criterion A.
Comments on this proposal are welcome, along with any data regarding recent trends in other regions, and any additional information about the threats currently affecting this species across its range.
BirdLife International (2015) European Red List of Birds. Luxembourg: Office for Official Publications of the European Communities. http://www.birdlife.org/datazone/info/euroredlist
Butcher, G.S. & Niven, D.K. (2007) Combining data from the Christmas Bird Count and the Breeding Bird Survey to determine the continental status and trends of North America birds. National Audubon Society, New York, NY, USA. http://www.audubon.org/bird/stateofthebirds/CBID/report.php
COSEWIC (2009) COSEWIC assessment and status report on the Horned Grebe Podiceps auritus, Western population and Magdalen Islands population, in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 42 pp. www.sararegistry.gc.ca/status/status_e.cfm
Llimona, F., del Hoyo, J., Christie, D.A., Jutglar, F., Garcia, E.F.J. & Kirwan, G.M. (2014). Horned Grebe (Podiceps auritus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) (2014). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. www.hbw.com
Wetlands International (2012) Waterbird Population Estimates: 5th edition. wpe.wetlands.org