The Maori Lakes - a high country stronghold for bittern

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

5 birds in the region

Bitterns return to the mouth of the Avon River

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.

Bittern fact sheet by Emma Williams

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.

Bitterns at Avon- Heathcote

Hi all- I am working on photo identification of birds on lower Avon River. There are at least 7 bitterns there. An eighth bird was sighted in the reeds on the lower Heathcote. This is a very signficant event with almost a fifth of Canterburys bittern population at one site. Yet I am concerned that the birds are vulnerable to predation and sighted three feral cats working the reed beds and noticed several cat predated mallards and one wounded mallard in the reeds. The Christchurch City Council has been notifed and hopefully a trapping program will be underway as most of the bitterns are concentarted in a small area. Also as the site is next to a busy highway the chance of road-kill is quite high as bitterns and cars don't mix. Also there is a Bittern conservation page on Facebook- "Bittern Conservation - New Zealand" If anyone makes any sightings or has any photos I would be interested- langlands@xtra.co.nz Regards Peter Langlands

spot the bittern ?

Spot the bittern !- photo taken today- Friday 13 th July 2012 at mouth of Christchurch's Avon River- for the first time in living memory there were three bitterns on the Avon Rivers' margin this morning . Not a bad start to Friday 13th !

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

Hands up who has been lucky enough to see a bittern in New Zealand? (Puts her hands down - with accompanying sad face.) New Zealand is a stronghold for the makatu or Australasian bittern, but even so, we only have around a thousand left. This is exacerbated by the fragmentation of their habitat and the way they are scattered across the landscape, meaning it's harder for them to find each other across wide areas, and easier for tiny populations of them to get knocked out by chance events or predators. Bitterns are masters of disguise. They have beautifully marked feathers that match their wetland reedy surroundings, and when in danger, they engage in a rather bizarre tactic of adopting a "freeze" position - standing straight and still in the raupo or reeds, pointing their bill to the sky and simply disappearing into the landscape. A friend of mine recently told me that she spent a couple of hours crouched in a wetland on the West Coast hoping to see a bittern, and when she gave up and moved away, one flew up out of the reeds next to her. The strong legs of the bittern mean they eject themselves out of the reeds like a jack-in-the-box so I imagine she got quite a fright! If you haven't seen a bittern, you may have heard one. Like the kakapo, they "boom". The males blow themselves up like a bullfrog and make a low-resonance booming noise that can apparently be heard for up to two kilometres. Given the bittern's incredible camouflage, the booming is often the only way to know that they are present in an area. If you're keen to find out if you have bitterns in your 'hood, listening out at dawn or dusk from now until November is a good way to find out. Bitterns are the apex predator of the wetland, so if your wetland has bitterns it's a good sign you have a healthy, well-functioning ecosystem. The bitterns eat young eels, fish, frogs, freshwater crayfish and insects. Where did all the bitterns go? In the space of 150 years, New Zealand has managed to drain and destroy 90 per cent of our wetlands, which are home to a huge range of native wildlife, including bitterns. Add in the mix the impact of predators and the odd roadkill death and you've got a recipe for a declining population. It's not all bad news though. Occasionally people give bitterns a helping hand, as in the case of Bitty the bittern, who spent a week or so in the Whangarei Bird Rescue Centre, who was fed, housed and then released back into a wetland to get on with his life. Or the story of the young bittern nestling who wandered into a chookhouse and spent three months living alongside his chook "mates".