Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The global population is estimated to number c.190,000-290,000 individuals (Wetlands International 2015), while national population estimates include: c.10,000-100,000 breeding pairs, c.1,000-10,000 individuals on migration and c.50-1,000 wintering individuals in China; < c.100 breeding pairs, < c.50 individuals on migration and c.1,000-10,000 wintering individuals in Japan and c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Russia (Brazil 2009). The European population is estimated at 27,700-47,900 pairs, which equates to 55,400-95,800 mature individuals (BirdLife International 2015).
The overall population trend is decreasing, although some populations have unknown trends (Wetlands International 2015). This species has undergone a small or statistically insignificant increase over the last 40 years in North America (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007). In Europe the population size is estimated to be increasing (BirdLife International 2015).
This species can be found in western Canada, north-west U.S.A., eastern Russia, north-east China and northern Japan, wintering from Japan and Korea through the Aleutian Islands to California (both U.S.A.), and off eastern the U.S.A. south to Florida. It can also be found in eastern Europe, west and west-central Asia wintering from the North Sea, Black Sea and Caspian Sea (del Hoyo et al. 1992).
Behaviour This species is fully migratory and breeds from April or May to June or August (del Hoyo et al. 1992) in isolated solitary pairs (Fjeldsa 2004), sometimes also nesting in loose colonies (del Hoyo et al. 1992) of up to c.20 pairs (Snow and Perrins 1998). Post-breeding adults undergo a flightless wing-moulting period (Fjeldsa 2004) after which they migrate south either singly or in small loose flocks, with concentrations of over 2,000 individuals occurring at favoured staging sites (del Hoyo et al. 1992). During the winter the species typically feeds singly and rarely aggregates into flocks (Fjeldsa 2004). Habitat Breeding The species breeds on small (less than 3 ha), shallow (less than 2 m deep) inland waters with abundant emergent vegetation (e.g. reedbeds), and stretches of open water, showing a preference for waters in forested areas or in shrub tundra further to the north (del Hoyo et al. 1992, Fjeldsa 2004). Suitable habitats include small pools and lakes, backwaters of large rivers, pools cut off from the sea in estuaries (del Hoyo et al. 1992) and coastal lagoons (Fjeldsa 2004). In coastal locations the species often makes foraging flights to inland lakes or offshore areas, and if foraging at sea it shows a preference for sub-tidal locations down to a depth of 15 m with sand or gravel substrates, scattered rocks and patches of seaweed (Fjeldsa 2004). Non-breeding When moulting, on passage or during the winter the species frequents large inland lakes (del Hoyo et al. 1992, Fjeldsa 2004) or shallow coastal areas (Fjeldsa 2004) with abundant fish stocks (del Hoyo et al. 1992), often considerable distances from the shore, amongst islands in archipelagos or over drop-off zones (Fjeldsa 2004). When foraging at sea the species shows a preference for sub-tidal locations down to a depth of 15 m with sand or gravel substrates, scattered rocks and patches of seaweed (Fjeldsa 2004). Diet Its diet consists predominantly of invertebrates (Snow and Perrins 1998) such as adult and larval aquatic insects (e.g. water beetles, water bugs and dragonfly larvae), crayfish and molluscs (Konter 2001), although fish are also be important locally or seasonally (del Hoyo et al. 1992). Breeding site The nest is a floating platform of plant matter anchored to submerged or emergent vegetation (del Hoyo et al. 1992). The species typically breeds in isolated pairs with more than 50 m between neighbouring nests (Fjeldsa 2004), although in some cases (e.g. on predator-free islands of floating vegetation attached to emergent vegetation beds) semi-colonial nesting may occur (Fjeldsa 2004).
The introduction of large fish, such as the non-native Rainbow Trout, to many inland waterbodies for freshwater fisheries and recreational fishing has resulted in greatly increased resource competition for invertebrate and smaller fish prey (HELCOM Red List 2013). The productivity and suitability of waterbodies used by the species is also thought to be impacted by the expansion of timber plantations throughout the boreal zone, however, the impacts of this are presently unknown. The species is also highly susceptible to bycatch in gillnets, with tens to hundreds caught annually in the Baltic Sea (Zydelis et al. 2013). This is considered likely to be the driver of a very rapid decline over the past few decades in the Baltic Sea (Skov et al. 2011) but represents only a small part of the global wintering range. Bycatch is also a threat in North American coastal waters.Red-necked Grebes were among the species most severely impacted by the Exxon Valdez oil spill, demonstrating little recovery in numbers within three years (Day et al. 1997). However, its very large range places only a small proportion at risk of direct mortality in a single incident. Persistent organochlorine pollution has been documented to reduce egg viability dramatically in the past, thus greatly reducing reproductive success (De Smet 1987), but bans on the use of such compounds has reduced the threat this poses to populations. Many freshwater sites throughout the breeding range have become eutrophied through the effects of agricultural run-off and large-scale freshwater fisheries, the impact of which is unknown. It is considered to be at relatively high risk of collision with wind turbines and other offshore infrastructure due to undertaking nocturnal flights and having only low manoeuvrability (Garthe and Hüppop 2004), although the effect of this on the population has not been quantified. The species has also been recognised as a species of high vulnerability to climate change in a full life-cycle assessment in America (Culp et al. 2017), but actual impacts presently unknown.
Conservation Actions Underway
CMS Appendix II. Bern Convention Appendix II. The following information refers to the species's European range only: The species was included in the Grebes Status Survey and Conservation Action Plan published in 1997 (O'Donnel and Fjeldsa 1997).
Conservation Actions Proposed
The following information refers to the species's European range only: Key breeding and wintering sites should be identified and protected. In addition, boats near nesting areas should be restricted to minimise disturbance of incubating or brooding adults and prevent damage to nests. Research should be undertaken on the wintering and non-breeding activities of the species (Stout and Neuchterlein 1999). The enforcement of strict legislation on oil transportation would help reduce the risk of spills in the future and measures to reduce the impact of bycatch should be enforced. Impact assessments should be undertaken for wind energy development.
Text account compilers
Calvert, R., Stuart, A., Ekstrom, J., Ashpole, J, Fjagesund, T., Butchart, S., Hermes, C., Hibble, R., Malpas, L.
BirdLife International (2019) Species factsheet: Podiceps grisegena. Downloaded from http://www.birdlife.org on 22/09/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/09/2019.