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.

Family/Sub-family Ardeidae

Species name author (Linnaeus, 1758)

Taxonomic source(s) AERC TAC (2003), Cramp and Simmons (1977-1994), Dowsett and Forbes-Watson (1993), Sibley and Monroe (1990, 1993)

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

110,000 - 340,000

unset

18,100,000 km²

No

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

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 winters⁶ (although they may make local dispersive movements related to rainfall)⁴. Continental populations are mainly migratory however^{2, 6} with a marked post-breeding dispersal of immatures². The species breeds from March to June in Eurasia and during the rains from September to January in South Africa¹. It usually nests solitarily although males are polygamous and may mate with up to five females nesting on a large wetland site¹. The species remains solitary throughout the year¹ (although migratory individuals may travel in small flocks)², and is mainly crepuscular in its activities². Habitat Breeding The species has highly restrictive breeding habitat requirements¹. It shows a strong preference for quiet lowland marshes around lakes and rivers (less than 200 m above sea-level)² with extensive dense young reedbeds of Phragmites spp. (e.g. with 1- 3 years worth of new growth^{3, 11} but still maintaining some old or dead stems¹) that are flooded but are fairly shallow¹ (less than 30 cm deep)⁶, have few fluctuations in water-level¹, have low acidity² and are surrounded by clear open areas¹ of deeper water is maintained into the driest part of the breeding season⁸. Breeding adults are more attracted to unfragmented¹¹ reedbeds over 20 ha in area, although smaller sites with networks of reed-fringed waterways or open wetland habitats with a number of small reedbeds⁶ (greater than 100 m)⁸ over a wide area may also be used⁶. The species avoids saline waters² but is equally abundant in fresh or brackish habitats¹ (e.g. in estuarine or delta marshes)⁵, and may occasionally nest in stands of rushes Scirpus spp.¹ or Papyrus spp. if reeds are unavailable². 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 farms¹, small ponds and wet grassy areas² as well as marshes and reedbeds¹. It also forages in running water (e.g. streams) when still waterbodies freeze during the winter⁴. 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 mammals¹. Breeding site The nest is a pad of reeds and other vegetation² constructed close to or floating on water¹ amidst dense reedbeds^{1, 2}. 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 habitat², nests sometimes being placed close together in areas where the species is particularly numerous⁴. Management information Breeding adults in Europe may be more attracted to unfragmented¹¹ 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 used⁶. 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 season⁸. 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 succession⁶. It also recommends the regular cutting of small areas of reedbed to maintain Phragmites spp. monocultures⁶, to provide a range of multi-age reed stands² 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)⁶. Large-scale reed cutting should be prohibited in the late-winter however². Wetlands should also be managed to enhance the carrying capacity of fish and eel populations (thus increasing food resources for bitterns)^{7, 9, 10}. 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)⁷ and issues relating to water quality, zooplankton and macrophyte community structures should be addressed¹⁰.

Threats The species is threatened mainly by the loss of Phragmites reed marshes² owing to habitat alteration through drainage², direct destruction¹, changes in traditional management (e.g. changes to reed harvesting regimes)³, sea level rise and salt water intrusion⁶, the effects of wave action from boat traffic at the edge of open water³, and pollution^{1, 3} (either eutrophication which modifies fish populations within reedbeds or pesticides which may reduce the species's survival)³. Disturbance from humans during the nesting period is also a threat^{2, 3, 6} (e.g. disturbance from reed cutting², noisy recreation and water-sports^{2, 3, 6}, motor vehicles and hunting²). The hunting of adults and collecting of eggs and chicks still occurs in some areas¹, and the species may suffer high mortalities in very cold winters (especially in sedentary populations)³.

References 1. del Hoyo et al. (1992). 2. Kushan and Hancock (2005). 3. Marion et al. (2000). 4. Hancock and Kushlan (1984). 5. Snow and Perrins (1998). 6. Newbery et al. (1996). 7. Noble et al. (2004). 8. Gilbert et al. (2005). 9. Gilbert et al. (2007). 10. Self (2005). 11. Puglisi et al. (2005).

Further web sources of information

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

European Union Species Action Plan

Text account compilers Stuart Butchart (BirdLife International), Jonathan Ekstrom (BirdLife International), Lucy Malpas (BirdLife International)

IUCN Red List evaluators Jeremy Bird (BirdLife International), Stuart Butchart (BirdLife International)

Recommended citation BirdLife International (2010) Species factsheet: Botaurus stellaris. Downloaded from http://www.birdlife.org on 9/9/2010

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.

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