Energy Budgets of Wintering Barnacle Geese: The Effects of Declining Food Resources

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. . Wiley and Nordic Society Oikos are collaborating with JSTOR to digitize, preserve and extend access to Ornis Scandinavica. . 1992. Energy budgets of wintering Barnacle Geese: the effects of declining food resources. -Ornis Scand. 23: 451-458.This paper documents the daily activities and feeding rates of Barnacle Geese Branta leucopsis through the autumn and winter in relation to changes in biomass of their food supply. Energy intake and expenditure were estimated and energy surplus or deficit for each month calculated. A net surplus was achieved in the months of October (+ 235 kJ d-1) and November (+ 247 kJ d-1) when most food was available.Geese suffered a net deficit in December (-225 kJ d-1) and January (-113 kJ d-1) when biomass and food quality were lowest. In February, when grass began to grow again, the birds achieved a surplus once again (+ 167 kJ d-'). Body mass changes through the winter were modelled using observed intake rates and estimated energy expenditure. Body mass predictions were consistent with observed mass and body condition changes. It is argued that mass loss in midwinter in this species is enforced by the limited feeding opportunity and declining food supply rather than an adaptive response to reduce predation risk. Geese gain substantial body reserves in autumn prior to this predictable mass loss. As soon as daylength and food biomass allow, lost reserves are replaced and mass increases rapidly in preparation for migration and breeding.

Site fidelity and range size of wintering Barnacle GeeseBranta leucopsis

“…Increased use of alternative feeding sites in February and March corresponds to the period when temperatures are low, day length short and consequently grass growth slow. Barnacle Geese are in negative energy balance during some midwinter months, and tend to lose mass accumulated since arrival in the autumn despite an increase in foraging effort (Owen et al 1992). By this point, grazing will have depleted the food supply at preferred sites which are less susceptible to disturbance or predation, resulting in increased intraspecific competition and consequent range expansion.…”

“…Their diet is predominantly grasses and herbs (Puccinellia maritima, Festuca rubra and Triglochin maritima) and White Clover Trifolium repens stolons on the saltmarsh, and cultivated grasses (mainly Lolium perenne with some Agrostis and Poa spp.) on inland pasture (Owen et al 1992).…”

“…Midwinter movements are more probably due to depletion of local food resources because of slow vegetation growth rates during cold weather (Owen et al 1992. Some birds may then either choose to disperse to a more suitable feeding site, or are forced to do so because of increased competition (Hupp et al 1996).…”

The impact of disturbance on the behaviour and energy budgets of Brent GeeseBranta b. bernicla

“…If none of these options is available, geese may incur an energy deficit and lose weight. 7 By affecting both the intake and expenditure sides of the energy equation, disturbance is potentially an important factor for many goose populations. Snow Geese Chen caerulescens staging in Quebec were estimated to suffer a decrease of 4-51% in daylight foraging time due to disturbance, with a loss of up to 2.9% of hourly metabolizable energy intake and an increase in hourly energy expenditure of up to 5.3%.…”

Density-dependent switches in diet: a likely mechanism for negative feedbacks on goose population increase?

“…These estimates were based on daily metabolisable energy intake and time energy budgets in wild barnacle geese wintering in the Netherlands (Ebbinge et al 1975;Owen et al 1992) and on heart rate and doubly labelled water techniques of exercising barnacle geese (Nolet et al 1992). Our assumption is that the relatively mild-Dutch winter conditions in maritime climate (average January temperature of ca.…”