A Field Validation of Plasma Metabolite Profiling to Assess Refueling Performance of Migratory Birds

Abstract

Plasma metabolite profiling offers a potential means to assess stopover refueling performance of migratory birds from a single capture. However, this method has not previously been validated where site quality has been determined independently using analysis of capture data. We captured and blood sampled six passerine bird species refueling at known high-quality (BASE) and low-quality (TIP) sites at Long Point, Ontario, Canada. Plasma triglyceride, an indicator of fat deposition, was higher at the BASE in three early-season species: the hermit thrush, the American robin, and the white-throated sparrow. Plasma B-OH-butyrate, an indicator of fasting and lipid utilization, was lower at the BASE in the same three species. Plasma glycerol was lower at the BASE in American robins, and plasma phospholipid did not differ between sites. No metabolite suggested better conditions at the TIP in any species. Regression of size-corrected mass on time of day also indicated better refueling performance at the BASE in some species, but metabolite profiling was generally more sensitive to site differences. The relationship between plasma glycerol and triglyceride was U-shaped, indicating high glycerol production during both lipolysis (as was previously known) and rapid fat deposition. Our results confirm the validity of metabolite profiling to assess stopover habitat quality and individual performance in refueling migrants.

Leukocyte profiles indicate nutritional, but not moulting stress in a migratory shorebird, the Common Snipe (Gallinago gallinago)

“…Totzke et al 1999;Quillfeldt et al 2004). Low levels of total proteins and triglycerides are often characteristic of short periods of food deprivation and covary with size-corrected body mass of birds (Boismenu et al 1992;Dawson and Bortolotti 1997;Guglielmo et al 2005). Also, plasma triglyceride concentrations have been widely used as indicators of mass gain and refuelling performance in shorebirds (Williams et al 1999;Seaman et al 2005).…”

Recent advances in understanding migration systems of New World land birds

“…In addition, recent applications of plasma metabolite analyses hold promise for evaluating avian refueling performance during en route stops. Plasma metabolite and stable-isotope analyses are currently being used as tools to assess and monitor habitat quality and to provide information on the relative importance of different stopover sites used by migratory birds , Guglielmo et al 2005, Cerasale and Guglielmo 2006. Finally, for soaring migrants, including many raptors, which do not depend heavily upon lipids to fuel their migrations, understanding other potential limiting factors such as the availability of roosting sites for large numbers of individuals is needed to better understand how habitat loss en route may affect the conservation status of these species (Bildstein 2006).…”

Landbird Migration in the American West: Recent Progress and Future Research Directions

“…In particular, applications of established techniques (mist-netting and associated analyses) to previously unstudied areas, and use of an important and novel technique (plasma metabolite sampling), have contributed to a growing body of literature pertaining to stopover ecology and habitat suitability (Wang et al 1998, Kelly et al 2002a, Cerasale 2004, Carlisle et al 2005b, Guglielmo et al 2005, Paxton et al 2007b.…”

“…An emerging technique, plasma metabolite profiling, enables investigators to make among-site and between-season comparisons of fuel deposition rate with reduced sample size requirements (Guglielmo et al 2005). With this technique, circulating levels of blood metabolites such as triglycerides, glycerol, and ß-hydroxybutyrate together reflect rates of mass change in individuals at the time of collection of the blood sample.…”