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LC
Eurasian Bittern Botaurus stellaris

Justification
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.

Taxonomic source(s)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: #http://www.aerc.eu/DOCS/Bird_taxa_of _the_WP15.xls#.
Cramp, S.; Perrins, C. M. 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.

Population justification
The global population is estimated to number c.110,000-340,000 individuals (Wetlands International 2006), while national population estimates include: c.100-10,000 breeding pairs, c.50-1,000 individuals on migration and c.50-1,000 wintering individuals in China; < c.1,000 wintering individuals in Korea; < c.100 breeding pairs and < c.50 wintering individuals in Japan and < c.100,000 breeding pairs and < c.1,000 individuals on migration in Russia (Brazil 2009).

Trend justification
The overall population trend is decreasing, although some populations have unknown trends (Wetlands International 2006).

Ecology
Behaviour Populations breeding on the Atlantic coast of Europe, in the Mediterranean and in South Africa are largely sedentary due to the relatively mild winters (Newbery et al. 1996) (although they may make local dispersive movements related to rainfall) (Hancock and Kushlan 1984). Continental populations are mainly migratory however (Newbery et al. 1996, Kushan and Hancock 2005) with a marked post-breeding dispersal of immatures (Kushan and Hancock 2005). The species breeds from March to June in Eurasia and during the rains from September to January in South Africa (del Hoyo et al. 1992). It usually nests solitarily although males are polygamous and may mate with up to five females nesting on a large wetland site (del Hoyo et al. 1992). The species remains solitary throughout the year (del Hoyo et al. 1992) (although migratory individuals may travel in small flocks) (Kushan and Hancock 2005), and is mainly crepuscular in its activities (Kushan and Hancock 2005). Habitat Breeding The species has highly restrictive breeding habitat requirements (del Hoyo et al. 1992). It shows a strong preference for quiet lowland marshes around lakes and rivers (less than 200 m above sea-level) (Kushan and Hancock 2005) with extensive dense young reedbeds of Phragmites spp. (e.g. with 1- 3 years worth of new growth (Marion et al. 2000, Puglisi et al. 2005) but still maintaining some old or dead stems (del Hoyo et al. 1992)) that are flooded but are fairly shallow (del Hoyo et al. 1992) (less than 30 cm deep) (Newbery et al. 1996), have few fluctuations in water-level (del Hoyo et al. 1992), have low acidity (Kushan and Hancock 2005)and are surrounded by clear open areas (del Hoyo et al. 1992) of deeper water is maintained into the driest part of the breeding season (Gilbert et al. 2005). Breeding adults are more attracted to unfragmented (Puglisi et al. 2005) reedbeds over 20 ha in area, although smaller sites with networks of reed-fringed waterways or open wetland habitats with a number of small reedbeds (Newbery et al. 1996) (greater than 100 m) (Gilbert et al. 2005) over a wide area may also be used (Newbery et al. 1996). The species avoids saline waters (Kushan and Hancock 2005) but is equally abundant in fresh or brackish habitats (del Hoyo et al. 1992) (e.g. in estuarine or delta marshes) (Snow and Perrins 1998), and may occasionally nest in stands of rushes Scirpus spp. (del Hoyo et al. 1992) or Papyrus spp. if reeds are unavailable (Kushan and Hancock 2005). Non-breeding The species frequents a more varied range of habitats outside of breeding season, foraging on rice-fields, watercress beds, gravel pits, fish farms, ditches, sewage farms (del Hoyo et al. 1992), small ponds and wet grassy areas (Kushan and Hancock 2005) as well as marshes and reedbeds (del Hoyo et al. 1992). It also forages in running water (e.g. streams) when still waterbodies freeze during the winter (Hancock and Kushlan 1984). Diet Its diet varies depending on the site and season although it predominantly takes fish (particularly cyprinids and eels) and amphibians as well as adult and larval insects, spiders, crustaceans, molluscs, snakes, lizards, birds, nestlings and small mammals (del Hoyo et al. 1992). Breeding site The nest is a pad of reeds and other vegetation (Kushan and Hancock 2005) constructed close to or floating on water (del Hoyo et al. 1992) amidst dense reedbeds (del Hoyo et al. 1992, Kushan and Hancock 2005). Although it is a solitary nester, breeding densities from 2 per 100 ha to 100 per 100 ha may occur depending on the quality of the habitat (Kushan and Hancock 2005), nests sometimes being placed close together in areas where the species is particularly numerous (Hancock and Kushlan 1984). Management information Breeding adults in Europe may be more attracted to unfragmented (Puglisi et al. 2005) reedbeds over 20 ha in area, although smaller sites with networks of reed-fringed waterways or open wetland habitats with a number of small reedbeds over a wide area may also be used (Newbery et al. 1996). There is evidence that females in Britain preferentially nest in locations surrounded by less scrub but more vegetated open water, with a higher proportion of Phragmites spp. than other plant species, and in areas where deeper water is maintained into the driest part of the breeding season (Gilbert et al. 2005). The European Action Plan for this species recommends raising water levels, harvesting and burning reeds, cutting invasive scrub, or digging out reedbeds on a rotational compartmental basis as methods of slowing reedbed succession (Newbery et al. 1996). It also recommends the regular cutting of small areas of reedbed to maintain Phragmites spp. monocultures (Newbery et al. 1996), to provide a range of multi-age reed stands (Kushan and Hancock 2005) and to favour the retention of water levels in spring and summer (promoting rapid growth, preventing a build-up of reed litter and providing foraging sites) (Newbery et al. 1996). Large-scale reed cutting should be prohibited in the late-winter however (Kushan and Hancock 2005). Wetlands should also be managed to enhance the carrying capacity of fish and eel populations (thus increasing food resources for bitterns) (Noble et al. 2004, Self 2005, Gilbert et al. 2007). In Britain it was found that suitable habitats should be provided for all fish life stages (including spawning, refuge and overwintering), the movement of fish throughout reedbeds should be promoted (e.g. by changes in hydrological management regimes and sluice design) (Noble et al. 2004) and issues relating to water quality, zooplankton and macrophyte community structures should be addressed (Self 2005).

Threats
The species is threatened mainly by the loss of Phragmites reed marshes (Kushan and Hancock 2005) owing to habitat alteration through drainage (Kushan and Hancock 2005), direct destruction (del Hoyo et al. 1992), changes in traditional management (e.g. changes to reed harvesting regimes) (Marion et al. 2000), sea level rise and salt water intrusion (Newbery et al. 1996), the effects of wave action from boat traffic at the edge of open water (Marion et al. 2000), and pollution (del Hoyo et al. 1992, Marion et al. 2000) (either eutrophication which modifies fish populations within reedbeds or pesticides which may reduce the species's survival) (Marion et al. 2000). Disturbance from humans during the nesting period is also a threat (Newbery et al. 1996, Marion et al. 2000, Kushan and Hancock 2005) (e.g. disturbance from reed cutting (Kushan and Hancock 2005), noisy recreation and water-sports (Newbery et al. 1996, Marion et al. 2000, Kushan and Hancock 2005), motor vehicles and hunting (Kushan and Hancock 2005)). The hunting of adults and collecting of eggs and chicks still occurs in some areas (del Hoyo et al. 1992), and the species may suffer high mortalities in very cold winters (especially in sedentary populations) (Marion et al. 2000).

Related state of the world's birds case studies

References
Brazil, M. 2009. Birds of East Asia: eastern China, Taiwan, Korea, Japan, eastern Russia. Christopher Helm, London.

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

Delany, S.; Scott, D. 2006. Waterbird population estimates. Wetlands International, Wageningen, The Netherlands.

Gilbert, G.; Tyler, G. A.; Dunn, C. J.; Smith, K. W. 2005. Nesting habitat selection by bitterns Botaurus stellaris in Britain and the implications for wetland management. Biological Conservation 124: 547-553.

Gilbert, G.; Tyler, G. A.; Dunn. C. J.; Ratcliffe, N.; Smith, K. W. 2007. The influence of habitat management on the breeding success of the Great Bittern Botaurus stellaris in Britain. Ibis 149: 53-66.

Hancock, J.; Kushlan, J. 1984. The herons handbook. Croom Helm, London.

Kushlan, J. A.; Hancock, J. A. 2005. The herons. Oxford University Press, Oxford, U.K.

Marion, L.; Ulenaers, P.; van Vessem, J. 2000. Herons in Europe. In: Kushlan, J. A.; Hafner, H. (ed.), Heron conservation, pp. 1-31. Academic Press, San Diego.

Newbery, P.; Schäffer, N.; Smith, K. 1996. European Union Bittern Botarus stellaris Action Plan.

Noble, R. A. A.; Harvey, J. P.; Cowx, I. G. 2004. Can management of freshwater fish populations be used to protect and enhance the conservation status of a rare, fish-eating bird, the bittern, Botaurus stellaris, in the UK? 11: 291-302.

Puglisi, L.; Adamo, M. C.; Baldaccini, N. E. 2005. Man-induced habitat changes and sensitive species: a GIS approach to the Eurasian Bittern (Botaurus stellaris) distribution in a Mediterranean wetland. Biodiversity and Conservation 14: 1909-1922.

Self, M. 2005. A review of management for fish and bitterns, Botaurus stellaris, in wetland reserves. Fisheries Management and Ecology 12: 387-394.

Snow, D. W.; Perrins, C. M. 1998. The Birds of the Western Palearctic vol. 1: Non-Passerines. Oxford University Press, Oxford.

Further web sources of information
Detailed species account from Birds in Europe: population estimates trends and conservation status (BirdLife International 2004)

Detailed species account from Birds in Europe: population estimates, trends and conservation status (BirdLife International 2004)

European Union Species Action Plan

Explore HBW Alive for further information on this species

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

Species factsheet from HeronConservation - The IUCN-SSC Heron Specialist Group

Text account compilers
Ekstrom, J., Butchart, S., Malpas, L.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2014) Species factsheet: Botaurus stellaris. Downloaded from http://www.birdlife.org on 31/10/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 31/10/2014.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Bittern (Botaurus stellaris) 0

Key facts
Current IUCN Red List category Least Concern
Family Ardeidae (Herons)
Species name author (Linnaeus, 1758)
Population size mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 8,150,000 km2
Country endemic? No
Links to further information
- Additional Information on this species
- Projected distributions under climate change