724_Final Report.pdf - North Pacific Research Board

More documents

Recommendations

Info

polychaetes (Petersen et al. 1998, Lovvorn et al. 2003). Steller’s eiders have been reported to consume a diverse diet of invertebrates, suggesting they are non-selective foragers (Petersen 1980, Petersen 1981, Bustnes and Systad 2001). During the nesting season, eiders feed on insects, insect larvae, seeds, and plant materials in tundra ponds resulting in a diet higher in carbohydrates (Petersen et al. 2000, Fredrickson 2001). In our experiment, the simulated pseudo diet 5 consisted of 50% clam and 50% mussel and was well estimated using the model and FA subsets indicating that two species of bivalves can be distinguished from each other. However, the simulated pseudo diets and actual diets were comprised of only five diet items. Thus, further work is needed to examine the FA profiles of clams, amphipod, polychaetes and other diet items of wild eiders. For interpretation of the time frame that the estimated diet represents, results from our captive study to estimate diets of wild eiders should be applied with caution. For example, Day 0 eider biopsies indicate that if the diet had been constant for 10 weeks, the estimated relative proportion of diet items using QFASA are very accurate. However, without knowing that the diet had been constant for 10 weeks, a dietary percentage of 20% could mean that (1) the diet item was truly 20% of a constant diet, (2) the proportion of that diet item was much greater (perhaps 50%) up until 3-4 weeks prior to biopsy sampling and had not been consumed at all after that, or (3) the proportion of that diet item increased over the last 3-4 weeks but was not consumed before then. Thus, the exact quantitative proportions in diet do indeed represent a perhaps unknown integrated period and may be less meaningful than detecting shifts in diet. That is, sampling birds at arrival on breeding grounds over time can detect shifts in diets at staging areas and possibly wintering areas over time, which would provide meaningful information about changes in relative abundance of prey at these areas over time. In conclusion, we advise researchers to apply our QFASA results with some caution in that the captive eider CCs, turnover rates, and FA subsets may require further consideration in application to wild birds. We stress that further work is required to calculate complete turnover rates of FAs from a natural diet, investigate the sensitivity of CCs and FA subsets to diets, and of the model to the CCs and FA subsets used. However, despite this sensitivity our study showed that QFASA accurately estimated Diet 1 and accurately indicated diet switches in captive eiders, and that diets can be estimated over an extended time period. Thus, our understanding of diet can be back-tracked to more than a month in a feeding eider. Regardless of model limitations, this study provides an important basis for further validation studies and interpretation of adipose tissue FA data from wild populations. Applying minimally invasive QFASA techniques to determine the diets of spectacled and Steller’s eiders during different life history stages will provide information about their diets and help identify critical habitats to support conservation of these threatened breeding populations. 45
There is still much work to be done in this realm of research and we feel that our project has made a significant contribution. We are currently investigating the use of yolk FAs as a proxy for determining maternal diets of spectacled eiders and differences in FA signatures between infertile and fertile spectacled eider eggs (funding provided by National Park Service Coastal Marine <strong>Research</strong> Grant and U.S. Fish & Wildlife Service). Further research projects conducted in both captive and wild populations will increase our knowledge of how FAs are processed and metabolized in captive and wild birds. This information will further our understanding of how CCs and FA subsets are affected by diet and physiology, further our understanding of diets and habitat associations in marine birds, and improve our QFASA techniques to determine diets of predators. 46
Page 1 and 2: NORTH PACIFIC RESEARCH BOARD PROJEC
Page 3 and 4: TABLE OF CONTENTS STUDY CHRONOLOGY
Page 5 and 6: snails (Petersen et al. 1998, Lovvo
Page 7 and 8: een employed in eiders to evaluate
Page 9 and 10: CHAPTER 1. Validating quantitative
Page 11 and 12: Abstract Fatty acid (FA) signature
Page 13 and 14: migration, or how the diets of juve
Page 15 and 16: were switched to Diet 3 which consi
Page 17 and 18: 16:1n-7, 18:0, 18:1n-9, 18:1n-7, 18
Page 19 and 20: The diets of captive eiders were es
Page 21 and 22: Calibration coefficients (CCs) and
Page 23 and 24: Discussion The results from this ca
Page 25 and 26: appropriate for estimating a consum
Page 27 and 28: Ideally, captive studies should mim
Page 29 and 30: Acknowledgments Financial support w
Page 31 and 32: Federal Register. 1997. Endangered
Page 33 and 34: Raclot, T., Groscolas, R., and Cher
Page 35 and 36: Table 2. Sum of the squared errors
Page 37 and 38: Figure 5. QFASA estimates using the
Page 39 and 40: Figure 2. 2nd discriminant function
Page 41 and 42: Figure 4. proportion proportion 1.0
Page 43 and 44: Appendix 1. Fatty acid (FA) subsets
Page 45 and 46: CONCLUSIONS The results from this c
Page 47: we incorporated into our calculatio
Page 51 and 52: ACKNOWLEDGEMENTS Funding was provid
Page 53 and 54: Harrison, N.M. 1984. Predation on j
Page 55: APPENDIX A: ASLC Fact Sheet 52

724_Final Report.pdf - North Pacific Research Board

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?