The importance of fruit to Swainson’s thrushes, Catharus ustulatus, during fall migration : a field test of plasma metabolite analysis
Graduation Date
2007
Document Type
Thesis
Program
Other
Program
Thesis (M.S.)--Humboldt State University, Wildlife, 2007
Committee Chair Name
Matthew D. Johnson
Committee Chair Affiliation
HSU Faculty or Staff
Keywords
Pacific Ocean--Humboldt Bay, Plasma metabolite, Swainson’s thrush, Migration, Humboldt State University -- Theses -- Wildlife
Abstract
I evaluated the hypothesis that fruit availability significantly influences stopover habitat quality for fall migrating Swainson's Thrushes (Catharus ustulatus) in coastal northern California. I analyzed plasma metabolites (triglycerides, β-hydroxy-butyrate, and glycerol) to assess the condition of Swainson's Thrushes during migration in two habitats: a native dune forest with abundant fruit (the Lanphere Dunes unit of the Humboldt Bay National Wildlife Refuge) and a riparian habitat with a significantly lower abundance of native fruits (Mad River County Park). In both habitats I collected blood samples from birds captured in mist nests and quantified dominant vegetation and fruit abundance in September and October, 2005 and 2006. I used stepwise ANCOVA to examine the difference in plasma metabolite concentrations between each habitat while controlling for confounding variables. In support of the hypothesis, β-hydroxy-butyrate concentrations were significantly higher in birds captured at Mad River County Park than birds caught at Lanphere Dunes, and fruit availability and diversity was lower at Mad River County Park than Lanphere Dunes. Concentrations of triglycerides and glycerol were not statistically different between the sites. Metabolite concentrations were significantly correlated with several covariates. Triglycerides were positively correlated with minutes since sunrise, date, fat score, and weight. β-hydroxy-butyrates were positively correlated with fat score but negatively correlated with minutes since sunrise. Plasma glycerol was positively correlated with fat and molt. Further work should couple plasma metabolite analysis with other techniques, such as radio telemetry or sampling of insect abundance, to more fully examine stopover habitat quality.
Recommended Citation
Leist, Amy J., "The importance of fruit to Swainson’s thrushes, Catharus ustulatus, during fall migration : a field test of plasma metabolite analysis" (2007). Cal Poly Humboldt theses and projects. 1522.
https://digitalcommons.humboldt.edu/etd/1522
https://scholarworks.calstate.edu/concern/theses/2514np128