warm-water divers – spatial distribution of dive activity in chick-rearing snares penguins...

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

The Snares Islands

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

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

Beneficial oceanographic features

Beneficial oceanographic features

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

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

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

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)

2003/04 2004/05

No of birds / grid cell

n = 5 birds n = 14 birds

2003/04 2004/05

No of birds / grid cell

n = 5 birds n = 14 birds

Horizontal speed

2004/052003/04

Dive duration

2004/052003/04

Max depth

2004/052003/04

Repeated Maximum Depth

2004/052003/04

Ambient temperature (5-10m)

2004/052003/04

SENSOR FAILUREno temperature data

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

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)

Why forage in warm waters?

Tasm

an C

urre

nt

South

land

Curre

nt

Why forage in warm waters?

SST (mean, Oct – Dec 2004)

MODIS/Aqua

** **

MODIS/Aqua

SST (mean, Oct – Dec 2003)

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)

High effort in colder conditions

SST (spring)SST (spring)Chl a (spring)Chl a (spring)

MODIS/Aqua

SST, productivity & body condition

MODIS/Aqua BCI: residuals from regression of body mass vs. bill length

MODIS/Aqua

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

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