warm-water divers – spatial distribution of dive activity in chick-rearing snares penguins...
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Spatial distribution of dive activity in chick-rearingSpatial distribution of dive activity in chick-rearingSnares penguins Snares penguins Eudyptes robustusEudyptes robustus
Thomas MatternThomas Mattern11, Katrin Ludynia, Katrin Ludynia22, Dave Houston, Dave Houston33 & Lloyd Davis & Lloyd Davis11
11 Department of Zoology, University of Otago, Dunedin, NZ Department of Zoology, University of Otago, Dunedin, NZ22 Research &Technology Research &Technology CentreCentre ( (BüsumBüsum), CAU Kiel, Germany), CAU Kiel, Germany
33 Department of Conservation Department of Conservation, Wellington, NZ, Wellington, NZ
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The Snares Islands
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The Snares Islands
THE SNARES THE SNARES (48°S, 166°E)
- ca. 120 km south of South Is.
- surface area: < 3.6 km²
- supports extensive populations of seabirds, including the Snares penguin
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Snares Penguin (Eudyptes robustus)
STATUS:- endemic to the Snares (IUCN: vulnerable)
- 25.000-30.000 pairs- population stable (unlike other NZ eudyptids)
no historic changes in prey availability
DIET: DIET: (Mattern 2006)(Mattern 2006)
- KrillKrill (~60% of food load)(~60% of food load)
- - SquidSquid (~20%)(~20%)
- FishFish (~20%)(~20%)
Primarily Primarily juvenile juvenile stagesstages
Associated Associated to primary to primary productionproduction
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Beneficial oceanographic features
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Beneficial oceanographic features
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Male penguin foraging (incubation)
Long trips: Long trips: - 12-16 d12-16 d- 150+ km from island150+ km from island
Destination:Destination:Subtropical Front Subtropical Front (STF) – convergence (STF) – convergence zonezone
Reason:Reason:Predictable, elevated Predictable, elevated productivity in early productivity in early springspring
chl a concentrationchl a concentration16-23. 10. 200316-23. 10. 2003
Mattern et al., IPC5 Ushuaia, 2004Mattern et al., IPC5 Ushuaia, 2004
But too far away But too far away when feeding chickswhen feeding chicks
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GPS logger deployments
1. Field work periods:- October/November 2003 & 2004
2. earth&Ocean GPS-TDlogs- geographic position after each dive- dive depth (resolution: ~0.1m) - temperature (~0.01°K)
3. Number of penguins equipped:- 2003: 8 females (chick guard)- 2004: 16 females (chick guard)
4. Deployment period: - both years: 2-4 days (ca. 1-2 foraging trips)
1 s interval
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Basic foraging parameters
n = 5 birds n = 14 birds
114.6 ± 23.3 km vs. 127.5 ± 39.9 km
71.9 ± 16.2 km vs. 76.6 ± 22.9
31.7 ± 4.9 h vs. 36.9 ± 11.4 h
Travel distance:
Max. Range:
Trip duration:
t=-0.81, p=0.434
t=-1.29, p=0.221
t=-0.47, p=0.649
2004/052003/04
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2003/04 2004/05
Spatial Analysis
n = 5 birds n = 14 birds
1. Linear extrapolation of tracks
2. Assign position to each dive
3. Analysis grid (0.04° x 0.04°)
4. Calculate means of dive parameters for each cell
5. Visualize via contour plots
DIVE PARAMETERS:DIVE PARAMETERS:
1.1.Horizontal speed Horizontal speed (consecutive dive events: distance / time interval)(consecutive dive events: distance / time interval)
2.2.Duration of diveDuration of dive
3.3.Maximum depth Maximum depth (greatest depth reached during dive)(greatest depth reached during dive)
4.4.Repeated Maximum Depth dive? Repeated Maximum Depth dive? (max depth±10% of preceding dive)(max depth±10% of preceding dive)
5.5.Ambient temperature at depths 5-10m Ambient temperature at depths 5-10m (from sensor records)(from sensor records)
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2003/04 2004/05
No of birds / grid cell
n = 5 birds n = 14 birds
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2003/04 2004/05
No of birds / grid cell
n = 5 birds n = 14 birds
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Horizontal speed
2004/052003/04
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Dive duration
2004/052003/04
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Max depth
2004/052003/04
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Repeated Maximum Depth
2004/052003/04
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Ambient temperature (5-10m)
2004/052003/04
SENSOR FAILUREno temperature data
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Results in a nutshell
Within 50 km radius: • High horizontal speeds• Short, shallow dives• Cool water
TRAVELLING
Outside 50 km radius: • Low horizontal speeds• Long, deep, RMD dives• Warm water
SEARCHING/FEEDINGPenguins seek Penguins seek warmerwarmer waters to forage waters to forage
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A rule of thumb in foraging ecology
Cold water stands for high productivity:
“UPWELLING”
Then... Why forage in warm waters?
(e.g. Humboldt Current, Benguela Current)(e.g. Humboldt Current, Benguela Current)
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Why forage in warm waters?
Tasm
an C
urre
nt
South
land
Curre
nt
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Why forage in warm waters?
SST (mean, Oct – Dec 2004)
MODIS/Aqua
** **
MODIS/Aqua
SST (mean, Oct – Dec 2003)
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Why forage in warm waters?Why forage in warm waters?
MODIS/Aqua
** **
MODIS/Aqua
Chl a (mean, Oct – Dec 2003)Chl a (mean, Oct – Dec 2003) Chl a (mean, Oct – Dec 2004)Chl a (mean, Oct – Dec 2004)
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High effort in colder conditions
SST (spring)SST (spring)Chl a (spring)Chl a (spring)
MODIS/Aqua
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SST, productivity & body condition
MODIS/Aqua BCI: residuals from regression of body mass vs. bill length
MODIS/Aqua
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Why forage in warm waters?Why forage in warm waters?
Tasman Current:Tasman Current:Nutrient rich and Nutrient rich and warmwarm Central Tasman WaterCentral Tasman Water
With the current: With the current: horizontal transport of horizontal transport of ... nutrients... nutrients... planktonic prey... planktonic prey
NotNot UPWELLING UPWELLINGbut ratherbut rather
““SIDEWELLING”SIDEWELLING”
Snares penguins areSnares penguins areWarm-water diversWarm-water divers
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Thank you...
… the Snares penguins for their cooperation and endurance
… our friends and collegues Ursula Ellenberg and Alvin Setiawan for their invaluable help in the field
… Pete McLelland (Department of Conservation, Invercargill) for the permits to work on the Snares
… Gerrit Peters for designing the loggers and quick answers to stupid questions