Wednesday, June 3, 2015
Please help us find our missing bittern! By Emma Willams PhD researcher on bittern 4 June 2015 Last Spring we put transmitters on six male Australasian bitterns at Lake Whatumā, near Waipukurau, Hawkes Bay. When the breeding season finished in January, and the water levels on the lake dropped, all six bitterns left the area. We have been able to re-find five of these birds but the sixth bittern, Tama Tomoana, is still missing! Can you help us find him? We’re asking anyone with access to telemetry gear to check any wetlands, streams, farm ponds, drains and small lakes in their area. We believe he is still in the Hawkes Bay area but in reality he could be anywhere in the country. Recently an Australasian bittern carrying a satellite transmitter in Australia travelled 550 Km, across two state borders, within 11 days!…We don’t know if our bitterns travel the same distances. We’re assuming that Tama could be anywhere! Join the national hunt…and if you find him please contact Emma on 0272462274,firstname.lastname@example.org.
Wednesday, April 29, 2015
Colin DOC Technical Series Latest publication March 2015 38. (Botaurus poiciloptilus) in New Zealand. C. O’Donnell and E. Williams 2015. DOC Technical Series 38. 40 p. (PDF, 4,143K (opens in new window)) Summary: There is an urgent need for conservation managers to undertake inventory and monitoring programmes for the endangered Australasian bittern (Botaurus poiciloptilus; matuku) in New Zealand. Such programmes can be used to determine the distribution and relative abundance of Australasian bitterns nationally; identify significant habitats, sites and populations to enable their protection and implement conservation management; measure the response and effectiveness of management practices; and measure the health of wetlands. This report describes four protocols for the inventory and monitoring of Australasian bitterns, and also provides a guide to choosing the most appropriate method for a particular objective. The protocols build on previous methods that have been developed in other countries, testing and adapting them for New Zealand conditions, and extending them through the use of automatic recording approaches, which allow efficient sampling in remote and inaccessible locations. The protocols represent current ‘best practice’, but further refinements will likely be made in the future.
Sunday, January 18, 2015
Update from the New Zealand bittern research team: This season, as well as monitoring bitterns at key wetlands nationally, the bittern team has been busy calibrating our monitoring methods. Our aim has been to see how the number of bitterns detected with each method compares with the actual number of bitterns present at the site. To do this we’ve needed to capture as many bitterns as possible at one site (Lake Whatumā). Each captured bittern has been marked through the attachment of a radio transmitter. The attachment of these transmitters enables us to re-find and identify marked birds even when they’re hidden in the dense Raupo. Bitterns are difficult to catch due to their cautious nature and the inaccessibility of their natural habitat. A few bitterns have been caught before in New Zealand, but only by firing a net gun onto the bird from a helicopter - something that is very risky for the bird as well as expensive. To avoid having to use these intrusive methods we’ve been trialling some capture methods that have been used on closely related bittern species overseas. This is the first time in New Zealand that Australasian bitterns have been studied intensively like this. As very little is known about bitterns we are hoping that data from this study can also answer questions like: Where do bitterns go after the breeding season? What habitat types are important to bitterns for feeding and breeding? How big are home range sizes? And do bitterns come back to the same sites every year to breed? These are important questions that no one has the answers for yet. Once answered, this knowledge will be used to identify and manage sites that are important for bitterns, helping us to help prevent the extinction of this fascinating Endangered bird. This season our work was partly funded through the Arawai Kakariki Project and a Ducks Unlimited NZ grant.
Thursday, November 20, 2014
Automatic sound recorders have picked up at least three booming bitterns at the Maori Lakes in the O Tu Wharekai Conservation Area this spring. For bitterns in Canterbury the raupo beds are a critically important habitat for the last remaining 50-7
Monday, April 21, 2014
For the third year in a row ( 2012-2014) bitterns have returned to the mouth of the Avon River. It is very pleasing to have such a rare bird within Christchurch City. In 2012 I assisted the Christchurch City Council/Andrew Crossland and other park rangers with a systematic survey of the lower Avon River and adjacent reed and raupo beds in the adjoining Avon-Heathcote River with the pleasing result of five birds being found. This result makes the mouth of the Avon River one of the five most important wintering sites for bitterns within Canterbury.
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.