Saturday, March 2, 2013
Australasian Bittern Botaurus poiciloptilus (Wagler, 1827) Order: Ciconiiformes Nationally Endangered/Endangered Family: Ardeidae Other names: Matuku, Boomer, Bunyip, Black-backed or Brown bittern, Bull-bird (English), Avetoro Australiano (Spanish), Butor d’Australie (French), Australische rohrdommel (German) Geographical variation: One species. Plumage does vary but this is not thought to be geographical. Bitterns are extremely cryptic and rarely seen. This is due to a combination of factors, including their secretive/evasive behaviours, crepuscular habits, inconspicuous plumage and the inaccessibility of their habitat. As a result, their presence is most commonly discerned through hearing the distinctive ‘booming’ call of the males during the breeding season. Despite this, many an enthusiast has been treated to a sighting in areas where birds are more conspicuous, such as wetland/farmland edges, dykes, drains and even roads. Such sightings never disappoint, as bitterns can be behaviourally fascinating; with interesting copulation rituals, booming postures and their infamous ‘freeze’ stance. Identification [74 cm, weight: males 1400g and females 900g] Bitterns are large, stocky birds, with streaky dark-brown and beige plumage on their thighs, chest, breast, and throat; with dark brown along the back and neck. The head is dark except for pale beige around the cheek, forming either a pale superciliary- or eye-stripe. Plumage varies greatly but does not appear to be related to region, season or sex. Some authors have suggested age may explain some variation (Heather & Robertson,1996); with juveniles possessing a more ‘buffy’ plumage, which darkens as they mature, and then may pale again as the bird ages (Teal, 1989). However, this still hasn’t been confirmed and there have been so few opportunities to age birds that it is currently not relied upon in the field. Voice: Bitterns produce a sequence of distinct ‘Wooom’ calls known as ‘booms’. These calls are thought to be produced by males only. Each call sequence consists of several individual booms, ranging from 1-10 booms per sequence (bps), with a mean of 3 bps . These sequences are often repeated at regular intervals that appear consistent to individual birds. The function of these calls is assumed to be related to breeding as their production is almost entirely limited to the breeding season. Booms are commonly preceded or interceded with gasps or inhalations. Females are largely silent but are said to produce a bubbling noise when they return to the nest (Marchant, 1990; Soper, 1958; Teal, 1989) and a nasal ‘kau’ call when alarmed (Teal, 1989). Birds in flight have been reported to produce profound, resonant ‘kau kau’ calls or a more nasal single ‘kau’ call (Teal, 1989) Distribution and habitat Found throughout New Zealand, as well as parts of Australia and New Caledonia (BirdLife International, 2011). Studies in Whangamarino wetland, New Zealand suggest bittern mostly inhabit mineralised and semi-mineralised wetlands (Ogle and Cheyne, 1981), although they are often spotted foraging in drains and wetland/farmland edges. Population The New Zealand population is thought to have <900 individuals (Heather and Robertson, 1996) but accurate numbers are not available. Australia is thought to have < 1000 individuals and New Caledonia <50 (BirdLife International, 2012) Threats and conservation As 90% of wetlands are now gone in New Zealand (Cromarty and Scott, 1996; Ausseil et al., 2010), habitat loss is expected to be the largest threat to bittern populations. A review of related bittern species by O’Donnell (2011) suggested that predators, poor water quality, and reduced food availability may also be contributing to a population decline. Despite the likelihood that bittern are in decline, there is currently no information regarding the extent of this decline. More research is required to understand the relationship between bittern population changes and potential threats. Breeding The cryptic nature of bitterns has resulted in a deficit of information regarding breeding behaviour. Egg laying is thought to take place from August to December, peaking in November. Nestlings are usually reported between September and February, and expected to fledge from November to May (O’Donnell, 2011). Behaviour and ecology Bitterns are extremely sensitive to disturbance. When approached they either a) try to steal away silently before they have been detected or b) adopt a still posture, commonly known as the ‘freeze’ or ‘surveillance’ pose. This stance involves standing with an erect neck and bill. It allows the bird to blend perfectly into most wetland environments, whilst maintaining good surveillance of its surroundings. If an observer continues to approach a bittern that is in freeze stance, the bird will eventually take flight laboriously, or occasionally will flatten its chest completely to the ground, effectively disappearing from view in the blink-of-an-eye. When foraging, bitterns often stalk along wetland/water edges slowly, taking prey opportunistically. In areas where prey are abundant they have been observed slowly moving towards prey items until they are close enough to take their prey in a discreet, steady manner without needing to lunge or swipe. Food Australasian bitterns are opportunistic feeders. They are thought to feed predominantly on fish; but are also known to forage on eels, spiders, insects, molluscs, annelids, crustaceans, reptiles and amphibians (Teal, 1989; Whiteside, 1989). Web links http://www.nzbirds.com/birds/matuku.html http://www.birdlife.org/datazone/speciesfactsheet.php?id=3767 http://www.doc.govt.nz/conservation/native-animals/birds/wetland-birds/australasian-bittern-matuku/facts/ http://www.iucnredlist.org/apps/redlist/details/106003767/0 http://bird.net.au/bird/index.php?title=Australasian_Bittern http://www.teara.govt.nz/en/wetland-birds/3 http://www.doc.govt.nz/conservation/land-and-freshwater/wetlands/arawai-kakariki-wetland-restoration-programme/ http://en.wikipedia.org/wiki/Australasian_Bittern References Ausseil, A.-G. E., Chadderton, W. L., Gerbeaux, P., Stephens, R. T. T., & Leathwick, J. R. (2010). Applying systematic conservation planning principles to palustrine and inland saline wetlands of New Zealand. Freshwater Biology, 9999(9999). BirdLife International. (2012). Species factsheet: Botaurus poiciloptilus.Available at http://www.birdlife.org/datazone/speciesfactsheet.php?id=3767 [Accessed 11 July 2012]. Cromarty, P., & Scott, D. (1996). A directory of wetlands in New Zealand. Department of Conservation, Wellington, 395. Heather, B., & Robertson, H. (1996). The Field Guide to the Birds of New Zealand: Penguin Books (NZ) Ltd. Marchant, S., and Higgins, P. J. (Eds) (1990). ‘Handbook of Australian,New Zealand and Antarctic Birds. Vol. 1: Ratites to Ducks.’ (Oxford University Press: Melbourne.) 1056 - 1061 O Donnell (2011). Breeding of Australasian Bittern (Botaurus poiciloptilus) in New Zealand. Short Communication. Emu. 111, 197-201 Ogle, C. C., & Cheyne, J. (1981). The Wildlife and Wildlife Values of the Whangamarino Wetlands (No. Fauna Survey Unit Report No. 28). Wellington: New Zealand Wildlife Service. Soper, M. F. (1958). A Bittern’s nest. Notornis 8, 50–51. Teal, P. J. (1989). Movement, habitat use and behaviour of Australasian bittern (Botaurus stellaris poiciloptilus) in the lower Waikato wetlands. Masters thesis, Waikato University. Whiteside, A. J. (1989). The behaviour of bitterns and their use of habitat. Notornis, 36, 89-95. Breeding ecology facts tab Social structure: Mostly solitary. Female-only incubation and brood-care (Heather and Robertson, 1996)) Breeding season: August – May, peaking in November and December (O’Donnell, 2011) Maximum number of successful broods per season Observations so far suggest Australasian bittern produce only one brood per season. However rare successful second clutches may be possible, as they have been observed in more well-studied, closely-related species (e.g. Botaurus stellaris, Mallord et al., 2000). Nest type: raised or floating platform Nest description: A platform usually surrounded by water and made from broken raupo, reeds, rushes and/or woody vegetation (O’ Donnell, 2011). Nest height above water Mean of 5 nests = 0.43m (Teal, 1989) Clutch size Minimum: 3 Mean: 4 Maximum: 6 Mean egg dimensions (mm) 51 x 37mm Egg colour: Olive-brown Egg laying dates August- December (with median records in November (O’Donnell, 2011)) Interval between eggs in a clutch (days) 24 - 48 hours (Soper, 1958) Incubation behaviour: female only (Heather and Robertson, 1996) Incubation length (days) c. 25 (Heather and Robertson, 1996) Nestling type: Altricial (Kushlan and Handcock, 2005) Nestling period: Length unknown but nestlings have been recorded from September – February (O Donnell, 2011) Age at fledging approximately 7 weeks (Heather and Robertson, 1996) Age at independence (days) unknown Age at first breeding (years) unknown Maximum longevity (years) unknown Maximum dispersal (km) unknown References Heather, B., & Robertson, H. (1996). The Field Guide to the Birds of New Zealand: Penguin Books (NZ) Ltd. Kushlan, J. A., and Hancock, J. A. (2005). Herons. (Oxford University Press:New York.) Mallord, J. W., Tyler, G. A., Gilbert, G., & Smith, K. W. (2000). The first case of successful double brooding in the Great Bittern Botaurus stellaris. Ibis, 142(4), 672-675. Ogle, C. C., & Cheyne, J. (1981). The Wildlife and Wildlife Values of the Whangamarino Wetlands (No. Fauna Survey Unit Report No. 28). Wellington: New Zealand Wildlife Service. O Donnell (2011). Breeding of Australasian Bittern (Botaurus poiciloptilus) in New Zealand. Short Communication. Emu. 111, 197-201 Soper, M. F. (1958). A Bittern’s nest. Notornis 8, 50–51.
Tuesday, July 17, 2012
Thursday, July 12, 2012
Wednesday, July 11, 2012
The peek-a-boo bittern by Nicola Toki after an interview with Peter Langlands - Bittern Researcher 12 July 2012 Published on www.stuff.co.nz
Monday, June 11, 2012
Botaurus poiciloptilus Status_ne_offStatus_dd_offStatus_lc_offStatus_nt_offStatus_vu_offStatus_en_onStatus_cr_offStatus_ew_offStatus_ex_off Summary Classification Schemes Images & External Links Bibliography Full Account Taxonomy Assessment Information Geographic Range Population Habitat and Ecology Threats Conservation Actions View Printer Friendly Taxonomy [top] Kingdom Phylum Class Order Family ANIMALIA CHORDATA AVES CICONIIFORMES ARDEIDAE Scientific Name: Botaurus poiciloptilus Species Authority: (Wagler, 1827) Common Name/s: English – Australasian Bittern Assessment Information [top] Red List Category & Criteria: Endangered C1 ver 3.1 Year Published: 2009 Assessor/s: BirdLife International Reviewer/s: Garnett, S., Butchart, S., Bird, J. Contributor/s: Herman, K., O'Donnell, C., Blyth, J., Tzaros, C., Bell, B., Garnett, S., Holmes, T., Miskelly, C., Loyn, R., Wakefield, B., Watson, D., Burbidge, A., Jaensch, R., Barré, N., O'Connor, J., Sherley, G., Ford, H., Christidis, L. Justification: This species is listed as Endangered because it has a very small and rapidly declining population owing to loss and degradation of its wetland habitats. Urgent action is a priority to halt declines in Australia. History: 2008 – Endangered 2006 – Endangered 2004 – Endangered 2000 – Vulnerable 1996 – Endangered 1994 – Endangered Geographic Range [top] Range Description: Botaurus poiciloptilus occurs in the wetlands of southern Australia, New Zealand and New Caledonia (to France). In Australia the population is now estimated to number not more than 1,000 mature individuals15. Consecutive atlas censuses in Australia have shown a marked decrease in reporting rate; the species was recorded in 260 10-minute grid squares in 1977-1981, 142 grid squares in 1998-2003, and just 61 in 2003-200816. The declining reporting rate was particularly pronounced in the Riverina (63%), Tasmania (>90%), and south-west Australia (>90%). This decline in reporting rate is thought to represent a genuine population decline over the period. In Australia, most birds are in the Murray-Darling basin and adjacent coastal areas. In Western Australia, the population was estimated to contain up to 100 pairs in 19807, but it is now much reduced, with the largest concentration in the Albany and Lake Muir wetlands. There have been no confirmed records from the Swan Coastal Plain since 1992 and surveys conducted in 2007 and 2008 found that half the wetlands that supported the species in 1980 now retained no suitable habitat17. There are now only occasional records from Queensland5 and there appears to have been no great influx to remnant wetlands after the recent drought, as might have been expected if they were more common inland. In South Australia, breeding is confined to the south-east, however, loss of suitable habitat at Bool Lagoon, arguably the key site in Australia for this species, and other wetlands in the area due to changes in regional drainage, has probably had a large impact in last 10-20 years13. It is now known from just one site, Hirds Swamp, in Victoria18. In Tasmania the species is now recorded from only handful of sites and several of the major lakes that it once occupied have been dry for some years. In New Zealand, the estimated population was between 580-725 individuals in 19806; numbers may be greater, given the lack of targeted survey work, and the large size of suitable swamps9. In New Caledonia and Uvea, there have been just two recent records of single calling males, and the population is not thought to exceed 50 individuals1,3. Countries: Native: Australia; New Zealand Present - origin uncertain: New Caledonia Range Map: Click here to open the map viewer and explore range. Population [top] Population: In New Zealand, the estimated population was between 580-725 individuals in 1980 (Heather and Robertson, 1997). The population on New Caledonia is not thought to exceed 50 individuals. Following apparently rapid declines, the Australian population is now thought to number fewer than 1,000 mature individuals (R. Loyn in litt. 2008). Population Trend: Decreasing Habitat and Ecology [top] Habitat and Ecology: It has fairly specific habitat preferences, preferring shallow, vegetated freshwater or brackish swamps where there is a mixture of short and tall emergent sedges and rushes4. It has been recorded in paddies in the Murray Darling basin, but it is not thought to use such habitats for breeding18. It usually lays four eggs. It feeds, mostly at night, on fish, eels, frogs, freshwater crayfish and aquatic insects6. The population seems to increase rapidly in good years and decline rapidly in poor ones12. Systems: Freshwater; Marine Threats [top] Major Threat(s): In Australia and New Zealand, the main threats are wetland drainage for agriculture, as well as changes brought about by high levels of grazing and salinisation of swamps2,4,5. In Australia, the species appears able to adapt to the availability of ephemeral wetlands, but is likely to be particularly sensitive to the destruction of drought refugia. Loss of these habitats may explain its decline in Western and South Australia5. The Murray-Darling basin, a former stronghold of the species, has suffered consecutive droughts in recent years and over-extraction of water is an ongoing problem14,15. Shooting and flying into powerlines are additional contributory causes2, but hunting pressure is very low11. Conservation Actions [top] Conservation Actions: Conservation Actions Underway In Australia, Bool Lagoon and Lake Muir are managed specifically for the species5. In Australia, recent initiatives by the Threatened Bird Network to survey Painted Snipe Rostratula benghalensis australis will contribute to the information on the distribution of this species10, 18. Conservation Actions Proposed Complete field surveys to determine current global distribution, status and key sites for conservation1,5,8. Develop methods for assessing population trends5. In New Zealand, determine factors that may be limiting populations8. In New Caledonia, obtain legal protection of representative, low altitude habitats1. Protect remaining sites against drainage or salinisation. Rehabilitate former breeding sites5. Citation: BirdLife International 2009. Botaurus poiciloptilus. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2.
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Thursday, May 10, 2012
Hi all - yes I am still working on bitterns- data sets are being analysed on a national level at present by myself and I understand DOC- so to all who contributed sightings up to 2010- thanks . I will be releasing some informal reports this year and am working on a scientific paper on an analysis of bittern mortality-injury records in New Zealand.DOC updated their web page last year with a threatened species profile on bittern which Colin O'Donnell and myself contributed to - about time given the Nationally Threatened status of the species! At present I am keen on any bittern records ( not already sunmitted to me) from Canterbury in the last two years ( back to June 2010) for a research report I am working on at present. All sightings will be acknowledged. Thanks Peter