BRANTA — Steven Portugal

Seasonal variability in body composition, physiology and energetics of Barnacle Geese (Branta leucopsis)

Institution: University of Birmingham, UK
Supervisors: PJ Butler
Details: PhD 2008 (Expected)

Address: Biosciences, University of Birmingham, Edgbaston, Birmingham, West Midlands, B15 2TT, UK Email

Subject Keywords: migration, heart rate, abdominal temperature, data loggers, metabolic rate, body composition
Species Keywords: Barnacle Goose Branta leucopsis

 

Abstract

Svalbard barnacle geese are migratory birds, breeding in the high Arctic and wintering 1500km south in western Scotland. During their time in Svalbard, the geese have to breed and moult, before laying down sufficient fat reserves to survive the return journey south. Just prior to and during their autumn migration, the geese undergo a period of hypothermia (Butler & Woakes, 2001), which rather than aid with fat deposition prior to departure, would appear to play a more important role with its utilization during the migratory period and with its replacement once migration is complete and the birds have reached their wintering grounds. Captive barnacle geese show a distinctive annual cycle in body mass and composition that coincide with important annual events in their wild counterparts. Significant mass increases are observed prior to moult in July and migration in September, and, although not as dramatic as that observed in wild geese, the captive birds also show a drop in abdominal temperature (Tab) during late-September and early October, despite not undergoing the actual physical act of migration. This study uses heart rate data loggers to estimate year round field metabolic rate in the captive barnacle geese, to examine the relationship between metabolic rate, and the observed changes in body mass, composition and T­­ab. Because of the variation in mass etc, suitable calibrations of the relationship between heart rate and oxygen consumption were made at appropriate times throughout the year. The hormone melatonin was studied to determine what role it plays in the regulation of body mass, composition and Tab­ in response to various environmental stimuli, in particular day length, light intensity, and temperature. This study also examines non-invasive techniques for the analysis of body composition in birds, in particular the use of body condition indexes and morphological characteristics, and isotope dilution techniques using deuterium oxide.
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