Digestion by Barnacle Geese in the Annual Cycle: The Interplay Between Retention Time and Food Quality

Abstract

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Does agricultural food provide a good alternative to a natural diet for body store deposition in geese?

“…Each sample consisted of at least 10 droppings. Retention time of food in the digestive tract was 2.3 hours during staging in April (Prop and Vulink 1992). Therefore, care was taken to collect only fresh droppings produced from geese which spent at least three hours in the local feeding habitat.…”

“…Therefore, care was taken to collect only fresh droppings produced from geese which spent at least three hours in the local feeding habitat. Dropping samples are suitable because more than 60% of ingested food leaves the gut undigested (Prop and Vulink 1992) and they provide a representative isotopic signature of the diet mix. Moreover, we found good correlation between isotopic signatures of droppings and the respective food plants (G. Eichhorn, unpublished data).…”

Distribution of Barnacle GeeseBranta leucopsisin Relation to Food Resources, Distance to Roosts, and the Location of Refuges

“…For instance, the Barnacle Goose Branta leucopsis requires food containing more than 15% crude protein to meet nitrogen requirements (Prop & Deerenberg 1991, Amano et al 2004. Furthermore, waterfowl have food retention times as short as a few hours (Prop & Vulink 1992, McKay et al 1994, which is reflected by a high throughput and defecation rate (Owen 1980). Such a digestive system requires a high ingestion rate and only allows for easily digestible components (Karasov 1990).…”

Migration timing and stopover selection for barnacle geese Branta leucopsis

“…Therefore, geese have to time their migration to follow the wave of food availability and quality in stopovers along the migration flyway, and this phenomenon is called "green wave hypothesis" (Owen, 1980). For example, barnacle geese (Branta leucopsis), which form the focus of this study, are highly selective herbivores and depend on forage of high nutritious plants (Prop & Vulink, 1992). Likewise, using field data, van der Graaf (2006) demonstrates that along the North-Atlantic flyway there is a successive wave of the nutrient biomass of barnacle geese and they utilize the stopover sites at the moments of peak nutritional quality.…”

“…Barnacle geese are highly selective herbivores (Prop & Vulink, 1992), and they prefer to eat the parts of a plant with the highest nutritional quality (Black et al, 2007). The green wave hypothesis has been successfully tested for this species using direct field measurements of plant biomass and quality at selected field sites (van der Graaf et al, 2006).…”