DIVING IN! Quantifying the underwater behavior of Christmas Shearwaters on Kure Atoll ILANA NIMZ MARS 6040: SEABIRD ECOLOGY

Transcription

1 DIVING IN! Quantifying the underwater behavior of Christmas Shearwaters on Kure Atoll ILANA NIMZ MARS 6040: SEABIRD ECOLOGY

2 Rationale: Underwater behavior is a mystery! Christmas (Chocolate) Shearwaters (CHSH, Puffinus nativitatis) Tuna Bird foraging guild (Harrison et al. 1983) Aquatic morphology (Kuroda 1954, Hertel and Ballance 1999) Underwater behavior unknown Qualitative observations of frequent deep diving (L. Spear p.c. via Gochfeld et al. 1999) No published tagging studies

3 Objectives Quantify foraging behavior of CHSH from Kure Atoll, Papāhanaumokuākea Marine National Monument (PMNM) 1) Basic dive parameters: Depth, duration, frequency Surface time 2) Temporal: Hourly Dive Frequency 3) Physiology: Behavioral ADL (badl)

4 Methods: Dive Analysis Use data from Time-Depth-Recorders Profiles summarized with R package divemove (Luque 2007) Comparable to other shearwater TDR studies (Dean 2012, Shoji et al. 2016) 1) Basic Summaries: -Max, mean, med: depth & duration -Post dive intervals (PDI) 2) Temporal: Number of dives per hour 3) badl: PDI slope change (TDR)

5 Results 1: Dive Summaries 8 birds 33 bird-days Range 3-8 days 1,519 dives Maximum Depth Range: m Maximum Duration Range: s Avg Depth: 3 m Med Depth: 2 m Avg Duration: 5 s Med Duration: 3 s

6 Proportion of Dives Proportion of Dives Results 1: Dive Summaries More frequently diving short and shallow 45% dives < 2 m 53% dives 1-3 s Dive Depth Frequency Dive Duration Frequency % 99% 95% 99% Depth (m) Duration (s) Deepest + longest dive: 24.1 meters, 31 seconds

7 Dive Depth (m) Results 1: Dive Summaries Dive Depth vs. Duration r=0.91 R² = Dive Duration (s) Linear increase of depth with duration

8 Proportion of Dives Results 2: Temporal Dive frequency during each hour Hour of Day Civil Twilight: 6:35 ± 8 min 21:06 ± 2 min

9 PDI ( s ) Results 3: Physiology Surface recovery time relative to duration Dive Duration (s) Overall badl estimated at s Individual variation 6-19 s

10 Conclusions 1) Capable of deep diving More frequently short and shallow Deeper dives are longer 2) Dive more in the evening Less to carry in stomach while foraging Less digested when provisioning chicks 3) badl Estimated at ~16 s Individual variation Small dataset

11 Next Research Steps Integrate diet data Barfs from 5 tagged birds Link prey items to last recorded diving behavior Infer minimum foraging Use flight speed information with time elapsed between last dive and tag retrieval at colony (Spear and Ainley 2008) Shearwater comparison range

12 References Dean, B. (2012). The at-sea behaviour of the Manx shearwater. Ph.D. Thesis, University of Oxford, Oxford, United Kingdom. Gochfeld, M., Gochfeld, D. J., Minton, D., Murray, B. G., Pyle, P., Seto, N., Burger, J. (1999). Metals in feathers of Bonin petrel, Christmas shearwater, wedge-tailed shearwater, and red-tailed tropicbird in the Hawaian Islands, northern Pacific. Environmental Monitoring and Assessment, 59(3), Harrison, C. S., Hida, T. S., & Seki, M. P. (1983). Hawaiian Seabird Feeding Ecology. Wildlife Monographs, 85, Hertel, F., & Ballance, L. (1999). Wing Ecomorphology of Seabirds from Johnston Atoll. The Condor, 101(3), Kuroda, N. (1954). On the classification and phylogeny of the order Tubinares, particularly the shearwaters (Puffinus), with special considerations on their osteology and habitat differentiation. Published by author, Tokyo, Japan Luque, S. P. (2007). Diving behaviour analysis in R. R News, 7(3), Shoji, A., Dean, B., Kirk, H., Freeman, R., Perrins, C. M., & Guilford, T. (2016). The diving behaviour of the Manx Shearwater Puffinus puffinus. Ibis, 158(3), Mahalo! DLNR- Cynthia Vanderlip, Matt Saunter, Naomi Worcester David Golden, Michelle Hester, Dr. David Hyrenbach