Plasma Metabolite Levels Predict Individual Body-Mass Changes in a Small Long-Distance Migrant, the Garden Warbler

Abstract

ABstRacr.-Change in body mass is an important measurement in many studies addressing changes in energy stores or condition. Usually, change in body mass is measured in birds caught twice, but this has a number of drawbacks (e.g. low number of retraps, retraps not representative of all first captures, adverse effects of first capture on body-mass development). Therefore, we investigated whether plasma metabolites correlate with body-mass change, and which metabolites could be used to predict body-mass change in birds caught once. In an experiment, 20 Garden Warblers (Sylvia borin) were given different amounts of food to induce stable, increasing, and decreasing body masses. Most of the eight plasma metabolites we examined were significantly correlated with the change in body mass between early morning and midday, the time of blood sampling, but not with body mass or various measures of activity. Metabolites that are known to characterize resorption were elevated in birds gaining body mass and metabolites characteristic of fasting were elevated in birds losing body mass. Triglycerides and fi-hydroxy-butyrate together explained 61% of the variation in body-mass change (triglycerides alone 44% and fi-hydroxy-butyrate alone 51%). These metabolites may be used to predict body-mass change in birds caught once, provided that the reliability and sensitivity of this method are checked in field tests.

Effects of physiological state, mass change and diet on plasma metabolite profiles in the western sandpiperCalidris mauri

“…Numerous studies in captive passerines have shown that plasma metabolite concentrations reflect the physiological state of a bird in relation to fattening or fasting (DeGraw et al, 1979;Jenni-Eiermann and Jenni, 1994;Totzke and Bairlein, 1998). Jenni-Eiermann et al (2002b) showed that certain plasma metabolites (triglyceride and β-OH-butyrate) reflect seasonally changing metabolic processes among different life cycle stages (molt, migration, oversumering) in captive red knot (with birds on a similar diet to our high-fat diet).…”

“…feeding vs fasting; Jenni-Eiermann and Jenni, 1994;Williams et al, 1999;Jenni and Schwilch, 2001), patterns of fuel utilization (Gannes, 2001;Jenni-Eiermann et al, 2002a) and inter-population or inter-site variation in fattening rates (Schaub and Jenni, 2001;Guglielmo et al, 2002). Direct validation of the use of plasma metabolite profiles to predict mass change in free-living birds will require independent assessment of fattening rates, which is difficult because of the problems associated with multiple recaptures of individuals, as outlined above (but see Guglielmo et al, 2005).…”

High glucose concentrations are associated with symptoms of mild anaemia in Whiskered Terns: consequences for assessing physiological quality in birds

“…Jenni-Eiermann and Jenni 1994). Although glucose plasma concentrations are often kept within a narrow range, low concentrations of glucose are usually recorded during fasting periods (Jenni-Eiermann and Jenni 1994;Alonso-Alvarez and Ferrer 2001).…”

A comparative study of some haematological and biochemical parameters between two species from the Anatidae family within migration season

“…The higher values found in Northern shoveler (144.6 mg/dl) and European teal (126 mg/dl) compared to non-migratory birds, e.g. Black-necked swan (Cygnus melanocoryphus), 90 mg/dl (Artacho et al, 2007), may be due to elevation of triglyceride levels in migratory birds since they constitute the important source of energy mobilized from the fat deposits in order to permit them to migrate (Jenni-Eiermann et al, 2002;Jenni-Eiermann & Jenni, 1994).…”