BEFORE THE CANTERBURY REGIONAL COUNCIL AT OAMARU Under the Resource Management Act 1991 In the Matter of Proposed Plan Change 3 to the Waitaki Catchment Water Allocation Regional Plan STATEMENT OF EVIDENCE OF ANN-KATHRIN VERENA SCHLESSELMANN IN SUPPORT OF SUBMISSIONS BY THE LOWER WAITAKI RIVER MANAGEMENT SOCIETY INC. Acting Solicitor: Richard Reeve Wilkinson Rodgers Lawyers PO Box 803 Dunedin 9054 Fax: 03 474 0922 / Ph. 03 477 9844 [email protected] BACKGROUND 1. My name is Ann-Kathrin Verena Schlesselmann. 2. I have been asked to give evidence on behalf of the Lower Waitaki River Management Society Inc. in support of its submission opposing certain features of Proposed Plan Change 3 to the Waitaki Catchment Water Allocation Regional Plan. 3. I hold a Bachelor of Science in Biology (2011) from the University of Auckland and a Postgraduate Diploma in Wildlife Management from the University of Otago (with Distinction; 2014). I was awarded both graduate and post-graduate awards. 4. I am a member of the Ornithological Society of New Zealand and the New Zealand Ecological Society. 5. I previously worked as a scientific staff member for the Landesbund für Vogelschtz in Bayern e.V., one of the leading non-governmental conservation organisations in Germany, for one year. As part of my work, I was providing advisory statements on the development of wind farms as well as being involved in various monitoring and research programmes of endangered bird species in Bavaria (Eagle owl Bubo bubo, Red kite Milvus milvus and Peregrine falcon Falco peregrinus). 6. I have also worked for over a year on a casual basis for the Department of Conservation (DOC; Science & Capability Christchurch; Terrestrial Ecosystems), particularly on bird monitoring programmes. 7. In September 2014, I commenced a Master of Science in Wildlife Management at the University of Otago on the conservation genetics of black-fronted terns (Chlidonias albostriatus). 8. As part of my Masters research, from October 2014 to mid-January 2015, I caught black-fronted terns in breeding colonies in the braided rivers of the South Island. I have been to 30 different black-fronted tern colonies in 22 different rivers, including the Waitaki River, and searched many other 1 braided rivers for colonies. In total I have caught over 300 individuals during this field season. 9. I have also been reporting to local DOC area offices on black-billed gull (Larus bulleri) colonies and have taken note on other braided river bird species at the sites I visited. 10. I have read the Code of conduct for Expert Witnesses and agree to comply with it. This evidence is within the area of my expertise. I have not omitted to consider material facts known to me that might alter or detract from the opinions that I express. SCOPE OF EVIDENCE 11. In my evidence, I assess the potential effects on braided river birds as a result of the proposed Plan Change 3, in particular the change to the allowed minimum flow, as follows: 11.1. I provide a general overview of the braided river bird species breeding in the Lower Waitaki River; 11.2. I describe the threat status of black-billed gulls, black-fronted terns and white-fronted terns and their respective populations on the lower Waitaki River; 11.3. I determine the significance of the lower Waitaki River as habitat for native birds using two classification systems; 11.4. I detail the ecology of, and major threats to, braided river specialist birds such as black-fronted terns and black-billed gulls as well as white-fronted terns; 11.5. I assess the potential impacts of the change in minimum flow on braided river birds in regard to risk of predation and/or disturbance and weed encroachment. 2 THREATENED BIRD SPECIES BREEDING IN THE LOWER WAITAKI RIVER 12. Twenty-six species of water birds were recorded on the Lower Waitaki River during surveys in October and November 2010 commissioned by Meridian Energy Ltd (Boffa Miskell 2011). In 2012, the conservation status of New Zealand birds was reviewed (Robertson et al. 2013); based on this review, six of the recorded species are currently classified as At Risk and a further six as Threatened (Table 1). Table 1 Maximum water bird counts from five replicate surveys October/November 2001, 2005 and 2005, Lower Waitaki River (from the evidence of M. Sanders1, NBTC hearing 2009 and Boffa Miskell 2011). Threat classification as per Robertson et al. 2013. Species At Risk in bold and species Threatened in bold and italic. Highest threat classification underlined. Species Black shag Little shag Spotted shag White-faced heron Black swan Feral goose Mallar/grey duck Grey teal Australasian shoveler Pradise shelduck New Zealand scaup NZ pied oystercatcher Pied stilt Black stilt Hybrid stilts Banded dotterel Wrybill Spur-winged plover Black-backed gull Black-billed gull Red-billed gull 1 Max. Count 2001 Max. Count 2005 Max. Count 2010 41 25 39 47 50 33 3 67 611 84 49 99 4 67 333 3 4 43 41 18 7 65 430 44 9 28 12 37 188 0 2 54 95 67 1 83 773 69 5 77 7 50 200 0 0 103 55 41 6 4 0 224 6,305 2,109 70 6,383 1,002 273 7,402 3,965 120 162 262 Threat Classification Naturally Uncommon Declining Declining Nationally Critical Nationally Vulnerable Nationally Vulnerable Nationally Critical Nationally Vulnerable M. Sanders 2009. Statement of evidence. Environment Canterbury resource consents hearing for the North Bank Tunnel Concept. 3 Species Black-fronted tern White-fronted tern Caspian tern Variable oystercatcher Turnstone Bar-tailed godwit Unidentified ducks Bittern Total Max. Count 2001 Max. Count 2005 Max. Count 2010 712 791 783 1,327 1,585 3,194 20 14 13 1 2 0 0 2 0 2 0 2 0 0 2 0 0 1 12,677 11,269 17,687 Threat Classification Nationally Endangered Declining Nationally Vulnerable Recovering Nationally Endangered 13. The most notable change of that review was upgrading black-billed gulls from Nationally Endangered to Nationally Critical, the highest threat classification. The criterion used for this classification is the very highongoing or predicted decline (>70%), and the qualifier is recruitment failure (Robertson et al. 2013). 14. Similarly, the criterion for classifying black-fronted terns as Endangered is based on the estimation of 1,000-5,000 mature individuals and a predicted decline of 50-70%. The qualifiers are recruitment failure and sparsity, meaning that the species’ occurrence is in typically small and widely scattered populations (Townsend et al. 2008). 15. White-fronted terns are classified as Declining due to a predicted decline of 10-50% and an estimated 20,000-100,000 mature individuals. The qualifier however is data-poor, meaning that confidence in the listing is low due to only poor data being available (Robertson et al. 2013, Townsend et al. 2008). 16. The threat classification system described above is specific to New Zealand and only takes populations in New Zealand into account. The IUCN Red List Categories and Criteria classifies species at risk of global extinction taking the worldwide distribution into account (BirdLife International 2012). In terms of those criteria, five bird species from those recent counts are considered world-wide threatened: 4 Black stilt: Critically Endangered Black-fronted tern: Endangered Black-billed gull: Endangered Bittern: Endangered Wrybill: Vulnerable 17. The justification for the classification of black-billed gulls and black-fronted terns is again the recent rapid population reductions, which specifically in the case of black-fronted terns are predicted to continue in the future due to on-going threats (Birdlife International 2012). THE IMPORTANCE OF THE LOWER WAITAKI RIVER FOR BLACK-BILLED GULLS, BLACK-FRONTED TERNS AND WHITE-FRONTED TERNS 18. Nationwide surveys for black-billed gulls and white-fronted terns were carried out by the Ornithological Society of New Zealand in 1995 and 1997 including on the lower Waitaki River (Powlesland 1998). 19. These surveys show that the majority of black-billed gulls, approximately 70%, breed in Southland, 25% in Otago and Canterbury, and the remainder in other areas in New Zealand. In 1995 and 1997, the lower Waitaki held ca. 2.2% and 2.5%, respectively, of the global population of black-billed gulls. Black-billed gull colonies have already disappeared from other rivers in Canterbury (Maloney 1999) and are in a state of decline of approximately 4.5% per year (i.e. 76% in three generations) on the lower Waitaki (Evidence of R. McClellan – NBTC hearing 20092). 20. In the same nationwide surveys, the largest population of white-fronted terns was found both times in the Waitaki. The river supported 20% and 36% of the population in 1995 and 1997 respectively, which indicates that it is an important stronghold for this species. 21. The lower Waitaki is also a significant stronghold for black-fronted terns. No nationwide surveys have been undertaken, but the population is 2 R. McClellan 2009. Statement of evidence. Environment Canterbury resource consents hearing for the North Bank Tunnel Concept. 5 estimated to consist of 7,000–10,000 individuals including immature birds (Keedwell 2002; O’Donnell & Hoare 2011). Therefore, based on the surveys of 2001, 2005 and 2010, 7.1%, 7.9% and 7.8% of the worldwide population of black-fronted terns was found in the Waitaki, using the optimistic population estimate of 10,000 individuals. 6 THE SIGNIFICANCE OF THE LOWER WAITAKI AS BIRD BREEDING HABITAT 22. The braided rivers of New Zealand are an internationally rare habitat type, and the ecosystem has been classified as Endangered using the IUCN Red List Criteria (Holdaway et al. 2012). They contain distinctive communities contributing to global biodiversity. 23. There are two ways in which to classify the significance of the Lower Waitaki for native birdlife: 23.1. The assessment of the significance of braided rivers for indigenous birds in Canterbury published by the Environment Canterbury (O’Donnell 2000): The objective was to rank habitats for their significance for birds in the context of the Resource Management Act 1991 (RMA) based on a specifically developed classification system. 23.2. The Important Bird and Biodiversity Area (IBA) programme by BirdLife International (Forest & Bird 2014): The IBA programme uses a set of standard criteria for identifying sites based on the IUCN red list threat rankings and a set of population parameters (numbers of birds present based on their threat status) to identify internationally important sites. 24. In the Environment Canterbury assessment, the Waitaki River was ranked in the highest category for habitat significance and in the third highest category for threatened species. Of 272 sites examined, 36 were classified as nationally significant and 33 as internationally significant. The Waitaki was considered significant on a national and international level. Regarding the diversity of habitats present it was ranked as one of the top two of a total of 41 braided river sections and its habitat significance was ranked in the highest category (O’Donnell 2000). 25. The Waitaki River has also been identified as an IBA site based on the criterion that threshold numbers of several globally threatened species are present (Forest & Bird 2014). 7 26. Both the regional ranking and an assessment applying globally used criteria identified the Waitaki as a habitat of international significance for water birds. This is mainly due to the substantial populations of threatened birds being present and for some of which the Waitaki is an important stronghold. BREEDING ECOLOGY OF TERNS AND GULLS 27. Braided river specialists are generally not present in the river all-year around, but use rivers for breeding during September-December. The breeding season coincides with periods of high rainfall and snow melt providing optimal higher flows (Duncan et al. 2008). They move to the coast after the breeding season in January. 28. Black-billed gulls nest in very dense colonies varying in size from a hundred to several thousand nests (McClellan 2009). Colony sites often change from year to year, which is thought to be a result of sites becoming unsuitable due to vegetation cover (McClellan 2009). In 48 black-billed gull colonies in Southland, McClellan (2009) found that weed cover was generally very low (<5%). Incubation occurs for 20–24 days and chicks fledge at ca. 26 days (Heather & Robertson 1996). 29. Black-fronted terns nest as loose colonies of varying size in areas of low weed cover. Colonies range in size from a few nests to several hundred. Colony sites can change from year to year depending on the availability of suitable habitat (Keedwell 2005). Black-fronted terns incubate for ca. 25 days and chicks fledge at ca. 30 days old. 30. White-fronted terns also nest in colonies on river beds, sand dunes or cliffs. They are commonly found closer to the sea and do not breed as far inland as the two other species. The incubation period is approximately 35 days and chicks fledge after 50 days (Mills 2013). 31. All three species will lay replacement clutches if eggs are lost early on in the breeding season; however black-fronted tern breeding colony 8 monitoring has indicated that early established nests have better incubation success than later ones (Woolmore et al. 2008). 32. As all these species breed in colonies, their distribution is patchy and can vary from year to year. For example, in 2010 black-billed gull breeding colonies were observed near the mouth of the river and in two different sections above Black Point (Boffa Miskell 2011). During aerial surveys in the past breeding season 2014/15, the only breeding colony was observed 800 m upstream of the SH 1 bridge (R. McClellan, pers. comm.). THREATS AND THEIR EFFECTS ON BRAIDED RIVER BIRDS 33. The two major threats (among others) to all three species are: 33.1. Predation and/or disturbance – primarily by introduced mammalian predators (Keedwell 2005, Sanders & Maloney 2002, McClellan 2009), but also native avian predators (Steffens et al. 2011) – leads to reduced productivity and survival. Past video studies have shown that cats, hedgehogs, stoats and other mammals are the main cause of mortality at nests. Furthermore, a single predator can cause the desertion of a whole colony (Keedwell 2005, O’Donnell et al. 2010). 33.2. Habitat loss and/or degradation through weed encroachment (McClellan 2009). 34. The reduction of river flow affects both of these factors by increasing the accessibility of breeding colonies on islands to mammalian predators and facilitating weed invasion (O’Donnell & Hoare 2011). Islands are thought of as providing some safety from mammalian predators (McClellan 2009). 35. Although it is often claimed that any water will deter mammalian predators, this does not necessarily hold up. A trial aimed at investigating the relationship between flow and breeding success of black-fronted terns at island and bank sites found overall higher breeding success on islands (Boffa Miskell & Urtica Consulting 2007). The following year, the same breeding colony in the Tekapo River had very low breeding success, with 9 most nests being abandoned (Woolmore et al. 2008). Low flows around islands (< 3 cumecs) do not always protect birds on islands. 36. In an analysis of 326 counts of black-fronted terns in South Island rivers from 1962-2008, significant declines of populations were detected over this period, particularly in rivers characterised by low flows (O’Donnell & Hoare 2011). On the basis of these results, it is predicted that if flows were reduced significantly on higher-flow rivers (such as the Waitaki), the rate of population decline would accelerate. 37. In the case of black-fronted terns, breeding success is generally quite low and highly variable among individual colonies due to predation and desertion. In the Tasman River, hatching success, i.e. the proportion of nests that hatched at least one egg, varied between 20% and 70% over five seasons (Cruz et al. 2013). In the Ohau River, hatching success varied over three seasons from 40% and 60% (Keedwell 2005). Only a proportion of hatched chicks survive to fledging. In the Tasman River, no monitored chicks survived to fledging in three seasons and in the other seasons, it averaged 25%. 38. Similar variable breeding success was found for black-billed colonies in Southland with 0 - 0.88 fledglings per nest from over 5,000 nests (McClellan 2009). Breeding success was influenced both by colony size and location, with colonies on islands being on average more successful. 10 IMPACTS OF CHANGED MINIMUM FLOW ON BRAIDED RIVER BIRDS 39. This assessment of possible impacts on braided river birds by the proposed change in minimum flow is based on the following: Section 42A report (PPC3 WCWARP: s42A Report) Section 32 Assessment for PPC3; Ecology reports by Ryder Consulting in PPC3; Herein-referred-to evidence by Diana Robertson for the Hunter Downs Irrigation Scheme. 40. It is recognised that flows under 100 cumecs are rare (1 in 15 years) and that flows under 150 cumecs occur for some days almost every year (less than 10% in a year overall). Further, the flushing flows will remain the same. Risk of Disturbance and Predation 41. The proposed change in minimum flow would allow flows to be lowered to 102 cumecs during September–December, which is the breeding period of braided river birds. This raises several concerns in relation to disturbance and/or predation of breeding colonies: 41.1. The river sections downstream of Black Point would be most affected by the lower flows. Robertson reports white-fronted tern, black-fronted tern and black-billed gull colonies downstream of Black Point. Further, black-billed gulls and black-fronted terns do not necessarily nest again where they previously nested, instead choosing new sites based on available bare gravel patches. Therefore, the increased risk of predation or disturbance during low flows affects all three species as well as other braided river bird species, which are not nesting in colonies. 41.2. Given a minimum breeding time of 46 days and the fact that a single predator can cause a whole colony to desert, colonies on islands are at risk if these islands become more accessible to mammals under low-flow conditions (like the islands described by Robertson para. 3.16-3.17). Access by mammals would negatively influence overall 11 productivity of the species. All three colony breeding species are currently in decline, particularly black-billed gulls. 41.3. Robertson reports that there are still numerous islands present at 100 cumec flows, including some with fast flowing water around them. How many are “numerous” islands, and do these offer suitable breeding habitat (i.e. low weed cover)? Although islands may still be present, it is not necessarily a given that birds will choose to breed on them. In the present writer’s experience of visiting black-fronted tern colonies throughout the South Island, the presence of suitable habitat was more important than simply the presence of islands. Studies of black-billed gull colonies in Southland have also shown this (McClellan 2009). Weed Encroachment 42. Sanders1 (para. 31) in his evidence regarding NBTC states that the overall trend in vegetation pattern over the last 70 years in the Waitaki River has been towards increasing tall and shrubby exotic vegetation and decreasing bare gravel areas. Vegetation is continuing to encroach under current vegetation control and water flow regimes including the flushing flows. 43. Sanders1 (para. 29) also reports on the typical succession of exotic herbaceous species such as lupins, trapping silt and creating more stable substrate, which in turn facilitates colonisation by shrubby species like gorse and broom. 44. The continuing loss and degradation of breeding habitat for black-billed gulls, black-fronted terns and white-fronted terns is very concerning. McClellan’s study of Southland black-billed gull colonies showed that lower growing vegetation such as lupins (woody weeds were extensively controlled) were forcing birds to nest closer to the waterline, which in turn made them more prone to flooding (McClellan 2009). 45. If flows in the Waitaki are low, there is an increased risk of the establishment of exotic herbs and shrubs, depriving birds of breeding sites and causing them to nest in suboptimal habitat. Further, vegetation also 12 provides cover for predators which increases the risk of predation and disturbance (Evidence by G. Pickerell). 46. The continuous establishment of weeds will need to be countered with increased weed control of both woody and herbaceous species. Past analysis of available habitat for Southland black-billed gulls has shown that removing shrub vegetation leads to replacement by grass/herb vegetation. This is still unsuitable as breeding habitat (McClellan 2009). Aerial spraying of woody species in particular has no benefit for braided river birds, as dead vegetation is left behind instead of bare gravel patches. CONCLUSIONS 47. The Waitaki River is a nationally and internationally important breeding site for multiple threatened species. It is also the population stronghold for two tern species. 48. The main reason for black-fronted terns and black-billed gulls being classified respectively, as Endangered and Critically Endangered is recruitment failure leading to a declining population. 49. The major threats to black-billed gulls, black-fronted terns and whitefronted terns are predation and/or disturbance by predators and loss and/or degradation of breeding habitat. Both of these threats are linked to river flow. 50. The timing and magnitude of lower flows is critical to these species. The risk of predation and/or desertion of breeding colonies at lower flows directly affects overall population productivity. Further, overall degradation and/or loss of breeding habitat will exacerbate current population trends. ________________________ Ann-Kathrin Schlesselmann Date: 30th April 2015 13 REFERENCES BirdLife International 2012. The IUCN Red List of Threatened Species. Version 2014.3. http://www.iucnredlist.org accessed 30th April 2015. Boffa Miskell 2011. North Bank Tunnel: Waitaki River Bird Surveys, 2010. Prepared for Meridian Energy Ltd by Boffa Miskell Ltd. Boffa Miskell and Urtica Consulting 2007. North Bank Tunnel Concept: Blackfronted tern trial: Effects of flow and predator control on breeding success. Prepared for Meridian Energy by Boffa Miskell Ltd and Urtica Consulting. Cruz J, Pech RP, Seddon PJ, Cleland S, Nelson D, Sanders MD, Maloney RF 2013. 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