PPO2012-08 Pitt Island Shag foraging ecology MIKE BELL Wildlife - - PowerPoint PPT Presentation

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PPO2012-08 Pitt Island Shag foraging ecology MIKE BELL Wildlife - - PowerPoint PPT Presentation

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PPO2012-08 Pitt Island Shag foraging ecology MIKE BELL Wildlife Management International Limited, PO Box 607, Blenheim 7240, New Zealand mike@wmil.co.nz Presentation of draft final results to the Department of Conservation CSP Technical Working

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MIKE BELL

Wildlife Management International Limited, PO Box 607, Blenheim 7240, New Zealand mike@wmil.co.nz

PPO2012-08 Pitt Island Shag foraging ecology

Presentation of draft final results to the Department of Conservation CSP Technical Working Group 1 August 2013

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POP2012-08 Pitt Is. shag foraging ecology Specific Objectives Draft final results. Overall Objective To describe the foraging ecology of Pitt Island shags. Specific Objectives 1. To describe the spatial distribution and dive profiling of Pitt Island shag foraging behaviour at the Chatham Islands.

  • 2. To describe the diet of Pitt Island shags at the Chatham

Islands.

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POP2012-08 Pitt Is. shag foraging ecology

  • Endemic to the Chatham Islands
  • Nationally endangered
  • High – Moderate risk from fishing
  • Significant population decline in last

15 years - 729 pairs in 1997, down to 434 in 2011

  • Little known about ecology and

breeding biology Pitt Island shag

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POP2012-08 Pitt Is. shag foraging ecology

  • GPS tracking
  • GPS devices attached to central

back of birds

  • Time depth recorders (TDR’s)
  • TDR’s attached to plastic leg band
  • Birds captured at nest
  • Duel deployment (both GPS and

TDR attached to each bird)

  • Birds need to be recaptured to

recover devices and download data Methods

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POP2012-08 Pitt Is. shag foraging ecology

  • 27 birds caught and devices deployed
  • 17 birds re-caught and devices recovered
  • Birds not recovered due to nest failure, and hence birds no

longer occupying nest sites- 9/10 Predation 1/10 chick death at hatching Results

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POP2012-08 Pitt Is. shag foraging ecology

  • Foraging area data from 15 of the 17 GPS devices recovered
  • 79 individual foraging trips
  • Mean foraging distance 5.2km (range 0.4-18.2km)
  • No difference between NE and Waitangi birds
  • Observed difference between sexes, but unlikely to be a

real difference as influenced by behaviour of one male Results – foraging behaviour

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POP2012-08 Pitt Is. shag foraging ecology Results – foraging range Pt Munning and Te Whakuru

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POP2012-08 Pitt Is. shag foraging ecology Results – foraging range Waitangi

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POP2012-08 Pitt Is. shag foraging ecology

  • High forging site fidelity
  • Individual birds returning to the same areas to forage-

60% of birds feeding in one location only 33% in two locations 7% (one bird) in three locations Results – foraging behaviour

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POP2012-08 Pitt Is. shag foraging ecology

  • Dive data from 10 of the 17 TDR devices recovered
  • 39 full foraging trips, 4 partial trips
  • 6709 dives

Results – diving behaviour

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POP2012-08 Pitt Is. shag foraging ecology

2 4 6 8 10 12 14 16 18

Results – data recovered

16:58 30 Sep 2013 18:04

A12, Female breeding at Point Munning Foraging trip to Okawa Point

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POP2012-08 Pitt Is. shag foraging ecology

2 4 6 8 10 12 14 16 18

Results – data recovered

16:58 30 Sep 2013 18:04

2 4 6 8 10 12 14 16 16:58:19 16:58:29 16:58:39 16:58:49 16:58:59 16:59:09 16:59:19 16:59:29 16:59:39 16:59:49 16:59:59 17:00:09 17:00:19 17:00:29 17:00:39 17:00:49 17:00:59 17:01:09 17:01:19 17:01:29 17:01:39 17:01:49 17:01:59 17:02:09 17:02:19 17:02:29 17:02:39 17:02:49 17:02:59 17:03:09 17:03:19 17:03:29 17:03:39 17:03:49

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POP2012-08 Pitt Is. shag foraging ecology Results – data recovered

2 4 6 8 10 12 14 16 16:58:19 16:58:29 16:58:39 16:58:49 16:58:59 16:59:09 16:59:19 16:59:29 16:59:39 16:59:49 16:59:59 17:00:09 17:00:19 17:00:29 17:00:39 17:00:49 17:00:59 17:01:09 17:01:19 17:01:29 17:01:39 17:01:49 17:01:59 17:02:09 17:02:19 17:02:29 17:02:39 17:02:49 17:02:59 17:03:09 17:03:19 17:03:29 17:03:39 17:03:49

Dive duration Rest period Dive depth

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POP2012-08 Pitt Is. shag foraging ecology Results – dive depth

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Frequency (%) Dive depth (m)

  • Mean dive depth 6.6m; max 24.4m; 90% of dives <13m
  • No difference between the sexes
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POP2012-08 Pitt Is. shag foraging ecology Results – dive duration

  • Mean dive duration 22s, max 69s, most dives <40s
  • No difference between the sexes

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 <5 6-10 11-15 16-20 21-25 26-30 31-35 36-40 41-45 46-50 51-55 56-60 61-65 66-70 Frequency (%) Dive duration (s)

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POP2012-08 Pitt Is. shag foraging ecology Results – dive duration and depth

  • Strong relationship between dive duration and depth

5 10 15 20 25 10 20 30 40 50 60 70 Dive depth (m) Dive duration (s)

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POP2012-08 Pitt Is. shag foraging ecology Results – rest period

  • Mean rest period 19s, no difference between the sexes
  • weak relationship between dive duration and rest period

10 20 30 40 50 60 10 20 30 40 50 60 70 Rest period (s) Dive duration (s)

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POP2012-08 Pitt Is. shag foraging ecology Results – Daily foraging timing

  • All dives during daylight, with no clear daily pattern

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 Frequency (%) Dive start time

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POP2012-08 Pitt Is. shag foraging ecology Results – Foraging efficiency

  • Birds spent an average of 50% of foraging time underwater

per trip (41-70%)

  • No regional or sex difference

5 10 15 20 25 30 35 40 <10 11-20 21-30 31-40 41-50 51-60 61-70 71-80 Frequency (%) Time underwater (%)

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POP2012-08 Pitt Is. shag foraging ecology

Foraging trips Mean trip duration Mean dives/ trip Mean dive duration (s) Mean rest period (s) Mean depth (m) % underwater Okawa Point 19 01:07:14 83 27.5 24.2 9.4 53.4 Te Whakuru I. 3 0:33:25 92 9.0 20.0 2.7 31.7 Waitangi 9 0:53:17 85 22.7 20.3 6.4 51.5 South Coast 3 1:26:03 115 26.3 23.0 8.0 54.1 Port Hutt Bays 5 01:44:52 133 25.2 21.8 6.7 54.7

Results – Foraging area comparison

  • Linked GPS and TDR data – 39 foraging trips
  • Some difference in foraging parameters from different

areas

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POP2012-08 Pitt Is. shag foraging ecology Results – Estimating species foraging range Use foraging parameters to estimate foraging range

  • Foraging range 18km
  • Max dive 25m

Possible to determine overlap with commercial rock lobster fishery

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POP2012-08 Pitt Is. shag foraging ecology

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POP2012-08 Pitt Is. shag foraging ecology Results – Overlap with commercial rock lobster fishery

  • Foraging range covers all coastal waters of the Chatham

Islands.

  • However as 90% of dives <13m, most significant bycatch

risk during January and February when pots set close to shore

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POP2012-08 Pitt Is. shag foraging ecology Recommendations

  • Undertake further foraging studies –
  • Investigate regional differences in foraging behaviour

and efficiency

  • Investigate foraging behaviour and efficiency during
  • ther stages of breeding (i.e. chick rearing)
  • Determine drivers in variable timing of breeding at

different colonies

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POP2012-08 Pitt Is. shag foraging ecology Recommendations

  • Undertake a ecological studies
  • Breeding biology
  • Breeding success and causes of failure
  • Focusing on possible causes of population decline
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POP2012-08 Pitt Is. shag foraging ecology Thanks to landowners in the Chatham Islands who allowed access across their property for us to undertake this research; in particular Bruce Tuanui, Jack Daymond, Jim Murrison, and Abe

  • Neilson. WMIL staff Mark Fraser assisted in the field, and

Kelvin Floyd produced the maps. This project was funded by the Department of Conservation’s Conservation Services Programme (www.doc.govt.nz/mcs ) project POP2012-08 (100% Crown funded). Additional funding was provided by Forest & Bird following a grant from The Mohamed bin Zayed Species Conservation Fund and we are grateful for this support. Acknowledgements