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.
Species-specific responses by ground-nesting predators and river flows in
the braided Tasman River of New Zealand. Biological Conservation 167:
363-370.
Duncan MJ, Hughey KFD, Cochrane CH, Bind J 2008. River modelling to better
manage mammalian predator access to islands in braided rivers. In:
Sustainable hydrology for the 21st century, Proceedings of the 10th BHS
National Hydrology Symposium Exeter.
Forest & Bird 2014. New Zealand Seabirds: Important Bird Areas and
Conservation. The Royal Society Forest & Bird Protection Society of New
Zealand, Wellington, New Zealand. 76 pp.
Heather BD, Robertson HA 1996.The Field guide to the birds of New Zealand.
Penguin Books, Auckland, New Zealand. pp. 335-337.
Holdaway RJ, Wiser SK, Williams PA 2012. Status Assessment of New Zealand's
Naturally Uncommon Ecosystems. Conservation Biology 26: 619-629.
Keedwell RJ 2002. Black-fronted terns and banded dotterels: Causes of
mortality and comparisons of survival. Unpublished PhD thesis. Massey
University, Palmerston North, New Zealand. 194 pp.
Keedwell RJ 2005. Breeding biology of black-fronted terns (Sterna albostriata)
and the effects of predation. Emu 10: 39-47.
Maloney RF 1999. Bird populations in nine braided rivers of the Upper Waitaki
Basin, South Island, New Zealand: changes after 30 years. Notornis 46: 243256.
Mills JA 2013. White-fronted tern. In: Miskelly CM (ed.). New Zealand Birds
Online. http://www.nzbirdsonline.org.nz accessed 30th April 2015.
14
McClellan RK 2009. The ecology and management of Southland’s black-billed
gulls. Unpublished PhD thesis. University of Otago, Dunedin, New Zealand.
264 pp.
O’Donnell CFJ 2000. The significance of river and open water habitats for
indigenous birds in Canterbury, New Zealand. Environment Canterbury
Unpublished Report U00/37. Environment Canterbury, Christchurch, New
Zealand.
O'Donnell CFJ, Hoare JM 2011. Meta-analysis of status and trends in breeding
populations of black-fronted terns (Chlidonias albostriatus) 1962-2008.
New Zealand Journal of Ecology 35: 30-43.
O’Donnell, C.F., Sedgeley, J.A., van Hal, J. (2010). Variation in house cat (Felis
catus) predation sign at a black-fronted tern (Sterna albostriata) colony.
Notornis 57: 43-47
Powlesland R 1998. Gull and tern survey 1998. OSNZNews 88: 3-9.
Robertson HA, Dowding JE, Elliott GP, Hitchmough RA, Miskelly CM, O’Donnell
CFJ, Powlesland RG, Sagar RG, Scofield RP, Taylor GA 2013. Conservation
status of New Zealand birds, 2012. New Zealand Threat Classification Series
4. Department of Conservation, Wellington, New Zealand. 22 pp.
Sanders MD, Maloney RF 2002. Causes of mortality at nests of ground-nesting
birds in the Upper Waitaki Basin, South Island, New Zealand: a 5-year video
study. Biological Conservation 106: 225-236.
Steffens, K.E., Sanders, M.D., Gleeson, D.M., Pullen, K.M., Stowe, C.J. (2011).
Identification of predators at black-fronted tern Chlidonias albostriatus
nests, using mtDNA analysis and digital video recorders. New Zealand
Journal of Ecology 36: 48-55.
Townsend AJ, de Lange PJ, Duffy CAJ, Miskelly CM, Molloy J, Norton DA 2008.
New Zealand Threat Classification System manual. Department of
Conservation, Wellington, New Zealand. 35pp.
Woolmore C, Anderson S, Kimber D 2008. Black-fronted tern nesting success at
the Ruataniwha Wetlands and Tekapo/Ohau river Islands. 2007-2008
Breeding Season Notes. Project River Recovery Report 2007/04.
Department of Conservation, Twizel, New Zealand. 18 pp.
15