British Ornithological Union 2017

Presentation on the role of spatial and temporal variation in driving seabird foraging behaviour at the British Ornithological Union, March 2017. Here we show that both depth and tide influence foraging behaviour, and that environmental heterogeneity may influence the strength of bio-physical coupling between seabird behaviour and the tide.

Transcript

1. The influence of environmental predictability on foraging behaviour Alice M Trevail, Jonathan A Green, Jonathan Sharples, Jeffrey Polton, John Arnould & Samantha C Patrick @AliceTrevail alice.trevail@Liverpool.ac.uk
2. What drives animal movement? • Widespread variability in movement strategies Individual / Population Ecological processes Population dynamics Ed Schneider Liam Quinn Antarctica.gov.au
3. What drives animal movement? • Widespread variability in movement strategies • Environment can drive movement behaviour Resource availability : foraging habitat selection E.g. hotspots Ed Schneider Liam Quinn Antarctica.gov.au
4. What drives animal movement? • Widespread variability in movement strategies • Environment can drive movement behaviour • Q: How flexible are foraging strategies over time? Respond to resource availability at different time scales? Adapt to predictability? Ed Schneider Liam Quinn Antarctica.gov.au
5. What drives animal movement? • Widespread variability in movement strategies • Environment can drive movement behaviour • Q: How flexible are foraging strategies over time? • Q: Does environment influence flexibility? Heterogeneity : predictability May shape variation between populations Ed Schneider Liam Quinn Antarctica.gov.au
6. Environmental heterogeneity
7. Environmental heterogeneity Spatial variation: Depth Direction of currents Water column structure Resource availability
8. Environmental heterogeneity Spatial variation: Depth Direction of currents Water column structure Resource availability Temporal variation: Tide = predictable 12 hr cycle Speed & direction of currents Prey availability accessibility
9. Environmental heterogeneity & movement Q: How do birds use this space?
10. Environmental heterogeneity & movement Q: How do birds use this space? Q: How does habitat selection change with tide?
11. Environmental heterogeneity & movement Q: How do birds use this space? Q: How does habitat selection change with tide? Q: Does tidal influence vary with spatial heterogeneity?
12. Skomer Puffin Is. Skomer Puffin Island Spatially heterogeneous Hypothesis: More temporal variation in habitat selection Spatially homogeneous Hypothesis: Less temporal variation in habitat selection Bathymetry Longitude Latitude 51.4 N 51.6 N 51.8 N 52 N 52.2 N 52.4 N 6 W 5.5 W 5 W 4.5 W 0 20 40 60 80 100 120 140 Water depth (m) 140 0 10 km Study sites of contrasting heterogeneity
13. Methods: seabird tracking • Study species = Black legged kittiwake • Indicator species in marine policy • GPS loggers (iGotU 120): fix every 2 mins • Multiple trips per individual • Puffin Island: 505 trips, 59 individuals, 6 years • Skomer Island: 22 trips, 10 individuals, 1 year Latitude (°) 4.4 4.2 4 53.3 53.4 53.5 53.6 4.3 4.1 Puffin Island 52 51.9 51.8 51.7 Skomer Island 5.5 5.4 5.3 5.2 Longitude (°) @AliceTrevail
14. 5.6 5.8 5.2 51.6 52 51.8 5.4 Latitude (°N) Depth Longitude (°W) 4.5 W 0 20 40 60 80 100 120 140 Water depth (m) 140 0 Methods: quantifying habitat selection
15. 5.6 5.8 5.2 51.6 52 51.8 5.4 Latitude (°N) Depth Longitude (°W) 4.5 W 0 20 40 60 80 100 120 140 Water depth (m) 140 0 5.6 5.8 5.2 5.4 Depth for GPS points = Used (1) Methods: quantifying habitat selection
16. 5.6 5.8 5.2 51.6 52 51.8 5.4 Latitude (°N) Depth Longitude (°W) 4.5 W 0 20 40 60 80 100 120 140 Water depth (m) 140 0 5.6 5.8 5.2 5.4 Depth for GPS points = Used (1) 5.6 5.8 5.2 5.4 Depth for random points x10 = Available (0) Methods: quantifying habitat selection
17. 5.6 5.8 5.2 51.6 52 51.8 5.4 Latitude (°N) Depth Longitude (°W) 4.5 W 0 20 40 60 80 100 120 140 Water depth (m) 140 0 5.6 5.8 5.2 5.4 Depth for GPS points = Used (1) 5.6 5.8 5.2 5.4 Depth for random points x10 = Available (0) Binomial GLMM Response = Used/Available (1/0) Methods: quantifying habitat selection
18. Can split tidal cycle by: flow rate and tidal height Methods: quantifying tidal variation Tidal height (m) Time Low Water High Water Low Water High Water Prey behaviour Prey accessibility
19. Methods: quantifying tidal variation Tidal height (m) Time Low Water High Water Slack Low Slack Low: • Flow rate = Low • Water height = Low Low Water High Water
20. Flood: • Flow rate = High • Water height = Increasing Methods: quantifying tidal variation Tidal height (m) Time Low Water High Water Low Water High Water Slack Low Flood
21. Slack High: • Flow rate = Low • Water height = High Methods: quantifying tidal variation Tidal height (m) Time Low Water High Water Low Water High Water Slack Low Flood Slack High
22. Ebb: • Flow rate = High • Water height = Decreasing Methods: quantifying tidal variation Tidal height (m) Time Low Water High Water Low Water High Water Slack Low Flood Slack High Ebb
23. Results: Habitat selection Depth (m) Probability of habitat use 0.00 0.25 0.50 0.75 1.00 0 50 100
24. Habitat influences movement Depth (m) Probability of habitat use 0.00 0.25 0.50 0.75 1.00 0 50 100 At species level: Kittiwakes select for shallower water Kittiwake habitat selection
25. Habitat selection varies with tide Depth (m) Probability of habitat use 0.00 0.25 0.50 0.75 1.00 0 50 100 Tide = a predictable 12hr cycle = influences habitat selection Habitat selection by tide state Slack Low Flood Slack High Ebb
26. Habitat selection varies with tide Depth (m) Probability of habitat use Tide = a predictable 12hr cycle = influences habitat selection Selection strongest during flood slack high High flow rate / high water May alter prey fish distribution (Zamon 2003; MEPS) Habitat selection by tide state Slack Low Flood Slack High Ebb 0.00 0.25 0.50 0.75 1.00 0 50 100
27. 0 50 100 0 50 100 Tidal variability varies with colony Depth (m) Probability of habitat use Tide = more influence at Skomer 0.00 0.25 0.50 0.75 1.00 Habitat selection by tide state Slack Low Flood Slack High Ebb Puffin Island; 2016 Skomer Island; 2016
28. 0 50 100 0 50 100 Tidal variability varies with colony Depth (m) Probability of habitat use Tide = more influence at Skomer Strongest selection at different tidal states 0.00 0.25 0.50 0.75 1.00 Habitat selection by tide state Slack Low Flood Slack High Ebb Puffin Island; 2016 Skomer Island; 2016
29. 0 50 100 0 50 100 Tidal variability varies with colony Depth (m) Probability of habitat use Tide = more influence at Skomer Strongest selection at different tidal states Environmental heterogeneity increases flexibility 0.00 0.25 0.50 0.75 1.00 Habitat selection by tide state Slack Low Flood Slack High Ebb Puffin Island; 2016 Skomer Island; 2016
30. Tidal coupling hypothesis (Zamon 2003; MEPS)
31. Tidal coupling hypothesis (Zamon 2003; MEPS)
32. Tidal coupling hypothesis (Zamon 2003; MEPS)
33. Tidal coupling hypothesis (Zamon 2003; MEPS)
34. Tidal coupling hypothesis (Zamon 2003; MEPS)
35. Tidal coupling hypothesis (Zamon 2003; MEPS)
36. However… Geographic variation in response to tidal cycle (Cox et al 2003; MEPS) Tidal height (m) Time Slack Low Flood Slack High Ebb
37. What we’ve learnt Environmental heterogeneity important at this stage
38. What we’ve learnt Environmental heterogeneity important at this stage Response to tidal cycle
39. What we’ve learnt Environmental heterogeneity important at this stage Response to tidal cycle Predictable cues Movement
40. Next steps: Skomer Puffin Is. Rathlin 2017 tracking: Rathlin, Skomer & Puffin To explore a gradient in tidal variability coastal morphology Individual level Inter-annual variability in habitat selection
41. Thanks to Puffin Island field teams, including: Federico de Pascalis, Harriet Clarke, Ruth Dunn, Phil Collins, Louise Soanes & Steve Dodd As well as Skomer wardens, B and Ed, & Ros Green
42. In brief: Flexibility in movement behaviour varies with environmental heterogeneity Thank you for listening! Any Questions? @AliceTrevail alice.trevail@Liverpool.ac.uk