| Tony
D. Williams, Simon Fraser University Assessing habitat or site quality for migrating shorebirds: use of plasma metabolite analysis
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Recent studies have shown that analysis of plasma metabolites (in particular triglycerides and glycerol) can provide information on both the rate and direction of mass change (or fattening) in captive migratory birds. Consequently, it has been (suggested that plasma metabolite profiles might be used to determine mass-change or fattening rates in different subpopulations of birds from different habitats, or in relation to different climatic conditions, or anthropogenic disturbances. For example, we have shown that plasma metabolite analysis can reveal systematic variation in fattening rates at a landscape-level (at different stopover sites) in free-living birds. The main aim of this proposed project is to investigate the validity and usefulness of plasma metabolite analysis as a tool to assess and monitor habitat quality and to provide information on the relative importance of different stopover sites used by migratory western sandpipers (Calidris mauri) in the Northwest Straits/Georgia Basin region. Each year birds will be mist-netted during spring and fall migration at 4-5 stopover sites varying in the size of populations of sandpipers they support: small (< 2000 birds), medium (5-7000) and large (>10000) sites. All birds will be blood sampled, aged and sexed and body mass and fat score will be recorded. Individuals or populations with high fattening rates (indicative of high quality sites) will be defined as those with high residual (mass-specific) plasma triglyceride levels and low residual plasma glycerol. Using captive birds we will also investigate the robustness of the fattening vs. metabolite relationship to changes in nutrient composition of the diet. We will confirm or corroborate assessments of habitat quality based on metabolite analysis using data on two other indirect measures of site quality: a) ‘health’ or condition of subpopulations of birds using different sites (assessed by body mass, fat score, and hematological indices of immune function, and b) species composition and availability of potential invertebrate prey at each site, assessed using invertebrate sampling of sediment core samples, fecal analysis and observations of foraging birds. Marine wetlands (mudflats, salt marshes) are essential habitats for large populations of migratory shorebirds, yet they are one of the most highly threatened habitats in the Pacific north-west. Western sandpipers, one of the most abundant shorebirds using the Georgia Basin region, have been identified as a key indicator species for monitoring the health of these marine habitats. In addition, determining which habitat types and locations are appropriate for acquisition, and evaluation of the effectiveness of protecting estuaries, is an important management goal of Environment Canada. This project therefore deals with a key indicator species of marine habitats, and addresses a major requirement of conservation and management planning in the Northwest Straits/Georgia Basin region. |
| Publications resulting from this research |
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Seaman, D., T.D. Williams, R.W. Elner and C.G. Guglielmo. 2003. What can physiology tell us about stopover site habitat quality for migrating western sandpipers? Proceedings of the Georgia Basin/Puget Sound Research Conference, Vancouver, Canada. (PDF) Seaman, D. 2003. Landscape Physiology: Plasma metabolites, fattening rates and habitat quality in migratory western sandpipers. Master's Thesis, Simon Fraser University. Seaman, D.A., Guglielmo, C.G., Elner, R.W. & Williams, T.D. (2006). Landscape-scale physiology: site differences in refueling rates as indicated by plasma metabolite analysis in free-living, migratory sandpipers. The Auk 123; 563-574. (PDF) Seaman, D.A., Guglielmo, C.G. & Williams, T.D. (2005). Effects of physiological state, mass change, and diet on plasma metabolite profiles in the western sandpiper (Calidris mauri). Journal of Experimental Biology 208: 761-769. (PDF) |
| Management Implications |
| The Western Sandpiper is a small migratory shorebird that utilizes the Puget Sound's mudflats as stopover feeding and resting sites during its biannual migration between Arctic breeding grounds and wintering grounds from California to Peru. It feeds on marine invertebrates occurring on exposed intertidal mudflats and recent work has shown these birds are great indicators for determining the health of these marine habitats. Research by Seamans and Williams at Simon Frasier University, funded by the SeaDoc Society, has shown that metabolites in the blood, such as triglycerides, can be used to tell us how much weight birds put on at specific sites. Weight gain is critical for helping these birds make long migrations between breeding and non-breeding areas. This research has shown that there are different fattening rates between shorebird stopover sites and also at specific sites from season to season or year to year. Clearly birds fatten faster at some sites compared to others. Interestingly enough, sites have historically been judged to be important to shorebirds based on the numbers of birds present. Thanks to this SeaDoc – funded research, we now know that birds still utilized some sites, even if they aren't great for fattening, suggesting fattening rate is just one factor in determining the importance of a site. Loss of habitat and declining habitat quality have been identified as a cause for declines in many of Puget Sound's marine birds and this new technique will help improve our ability to identify and conserve important habitat for migratory shorebirds. |