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). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds 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.915,000-1,400,000 individuals (Wetlands International 2015). The European population is estimated at 330,000-498,000 pairs, which equates to 660,000-997,000 mature individuals (BirdLife International 2015).
The overall population trend is uncertain, as some populations are decreasing, while others are increasing or have unknown trends (Wetlands International 2015). In Europe the population is estimated to be declining moderately rapidly (BirdLife International 2015, EBCC 2018).
The species is found across most of Europe and central Asia, though it also winters in parts of southern Asia (e.g. northern India). Colonies can also be found scattered throughout Africa, from Tunisia and Egypt in the north and a few colonies in central Africa down to South Africa. Nesting colonies are also found in southern Australia and New Zealand, with individuals wintering in eastern and northern Australia (del Hoyo et al. 1992).
Behaviour The majority of this species is fully migratory although some populations may only undergo local dispersive movements (del Hoyo et al. 1992). It breeds between April and September in Europe, in all months of the year in Africa (peaking during the long rainy season) and from November to March in Australasia, nesting either in solitary, dispersed pairs or in loose colonies (forming only where safe nesting sites are few and feeding areas are extensive) (del Hoyo et al. 1992, Fjeldså 2004). After breeding (from August to October), adults may disperse locally to large lakes and reservoirs to undergo a flightless moulting period, during which gatherings of hundreds of individuals (occasionally even greater than 10,000) may form (del Hoyo et al. 1992, Fjeldså 2004). During the winter the species largely remains solitary, especially when feeding, but temporary congregations of up to 5,000 individuals may form in some areas (Snow and Perrins 1998, Fjeldså 2004).
Habitat Breeding The species breeds on fresh or brackish waters with abundant emergent and submerged vegetation, showing a preference for non-acidic eutrophic waterbodies with flat or sloping banks and muddy or sandy substrates, usually 0.5-5 m deep and with large areas of open water (del Hoyo et al. 1992, Snow and Perrins 1998). Suitable habitats include small pools or lakes, backwaters of slow-flowing rivers and artificial waterbodies (e.g. reservoirs, fish-ponds, gravel pits and ornamental lakes) (del Hoyo et al. 1992). In Australia the species also utilises swamps, reservoirs, lagoons, salt-fields, estuaries and bays, and in tropical Africa and New Zealand it may breed on montane, subalpine and alpine lakes up to 3,000 m (Marchant and Higgins 1990, del Hoyo et al. 1992). Non-breeding The species overwinters on large exposed ice-free lakes and reservoirs, moving to sheltered coastal inshore waters less than 10 m deep, such as brackish estuaries, deltas, tidal channels and tidal lagoons during cold spells (del Hoyo et al. 1992, Snow and Perrins 1998, Fjeldså 2004). In addition, it frequents large saline lakes in Australia (Marchant and Higgins 1990).
Diet Its diet consists predominantly of large fish as well as insects, crustaceans (e.g. crayfish, shrimps) and molluscs, occasionally also adult and larval amphibians (del Hoyo et al. 1992). The species's invertebrate consumption is highest during the breeding season (del Hoyo et al. 1992).
Breeding site The nest is a platform of aquatic plant matter either floating on water and anchored to emergent vegetation or built from the lake bottom in shallow water (del Hoyo et al. 1992). Typical nest sites include reedbeds or flooded thickets as well as more open sites such as floating mats of water-weed or kelp fronds (Fjeldså 2004).
In the past, New Zealand colonies experienced considerable declines with the introduction of exotic fish species, likely due to increased competition for food resources and a subsequent loss of productivity. However, this population now appears to be increasing (Llimona et al. 2018), suggesting this is no longer a significant threat even to this small percentage of the Australasian subspecies. Hunting for food and the plume trade has previously been a significant threat however, it no longer occurs at significant levels.
Conservation Actions Underway
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 Fjeldså 1997).
Conservation Actions Proposed
The following information refers to the species's European range only: the conservation of this species relies on the protection of lake habitats, limiting water-based recreation at key sites and enhancing nesting habitat in predator-free environments. Key international sites should be identified and protected. Evaluate the potential of the species as a keystone indicator of wetland health (O'Donnel and Fjeldså 1997). Enforce mitigation measures to reduce bycatch. Implement strict legislation on the transportation of oil to reduce the risk of future spills.
Text account compilers
Calvert, R., Hermes, C., Malpas, L., Martin, R., Stuart, A., Butchart, S., Elliott, N., Ekstrom, J., Ashpole, J, Fjagesund, T.
BirdLife International (2020) Species factsheet: Podiceps cristatus. Downloaded from http://www.birdlife.org on 25/05/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 25/05/2020.