Trumpeter Swan Food Habits, Forage Processing, Activities, And Habitat Use
Authors(s): J. R. Squires
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Publication Date: 0000-00-00
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Location: Laramie WY
Abstract: Wintering swans selected wide (mean 37m, range 10-91m ), low velocity (mean 0.06m/sec., range 0-0.27 m/sec) streams, that supported a greater biomass of macrophytes and tubers compared to random sites. On wintering areas, both plant senescene and herbivory were significant forces in reducing macrophyte biomass. Swan herbivory removed 16% of total macrophytes on Fish Creek. On the National Elk Refuge, trumpeter swan herbivory removed 42% of the foliage and 285 of the tubers of Potamogeton pectinatus. The dominant macrophytes present on Wyoming winter ranges included, Chara spp. (24.3%0, Elodea canadensis (25.6%), Myriophyllum exalbescens (18.8%), and Potamogeton pectinatus (25.3%). Ninety percent of the diet of wintering swans was composed of Chara spp. (36.8%), Elodea canadensis (29/6%), and Potamogeton pectinatus tubers (23.4%). Chara spp. and Elodea canadensis were eaten approximately in proportion to their abundance on winter ranges. Potamogeton pectinatus tubers accounted for only 0.5% of the biomass of aquatic plants present on wintering areas, yet comprised 23.4% of the diet. Swans ate more tubers (38.5%, P=0.1) in the spring compared to winter. Based on the true metabolizable energy (TMEn), digestive efficiency, and nutritional characteristics (protein and NDF), the winter and spring foods in declining order of quality were: Potmogeton pectinatus tubers, Elodea canadensis, Chara spp., Myriophyllum exalbescens, and Ceratophyllum demersum. The average throughout time for all forages was 239 min. Swans passed food quickly with low digestive effiiency. Swans increased their feeding time from 29.6% in the winter to 44.5% in the spring. During the winter, swans fed little in the morning (0.169) and increased their feeding rate throughout the day until night, when they fed at their highest rate (0.494). Wintering swans reduced feeding at a high rate throughout the day and night suggesting spring-use areas were important in establishing endogenous reserves for reproduction. Although endogenous reserves affect swan productivity (Anderson-Harild 1981, Bacon and Anderson-Harild 1989, Beekman 1991), the quality of nesting territories was also an important factor affecting swan productivity. Productive pairs occupied nest sites with a greater macrophyte biomass compared with nonproductive pairs. Females of productive pairs also appeared to take shorter recesses from incubation and incubated longer compared to females of nonproductive pairs. Invertebrate biomass did not differ between productive and nonproductive pairs.
Keywords: National Elk Refuge, Jackson Hole, Teton County, Fish Creek, habitat, animal, bird, Aves, ornithology, swan, water bird, waterfowl, Anatidae, trumpeter swan, food, forage, Olor buccinator, population, nest, nesting
| BIBLIOGRAPHY ID | 1465 |
| REF TYPE | Thesis |
| AUTHORS | J. R. Squires |
| PUB DATE | 0000-00-00 |
| DATE STR | 0000-00-00 |
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| DOC TITLE | Trumpeter Swan Food Habits, Forage Processing, Activities, And Habitat Use |
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| LOCATION | Laramie WY |
| ACADEMIC DEPT | Wyoming Cooperative Fish and Wildlife Research Unit |
| UNIVERSITY | University of Wyoming |
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| KEYWORDS | National Elk Refuge, Jackson Hole, Teton County, Fish Creek, habitat, animal, bird, Aves, ornithology, swan, water bird, waterfowl, Anatidae, trumpeter swan, food, forage, Olor buccinator, population, nest, nesting |
| ABSTRACT | Wintering swans selected wide (mean 37m, range 10-91m ), low velocity (mean 0.06m/sec., range 0-0.27 m/sec) streams, that supported a greater biomass of macrophytes and tubers compared to random sites. On wintering areas, both plant senescene and herbivory were significant forces in reducing macrophyte biomass. Swan herbivory removed 16% of total macrophytes on Fish Creek. On the National Elk Refuge, trumpeter swan herbivory removed 42% of the foliage and 285 of the tubers of Potamogeton pectinatus. The dominant macrophytes present on Wyoming winter ranges included, Chara spp. (24.3%0, Elodea canadensis (25.6%), Myriophyllum exalbescens (18.8%), and Potamogeton pectinatus (25.3%). Ninety percent of the diet of wintering swans was composed of Chara spp. (36.8%), Elodea canadensis (29/6%), and Potamogeton pectinatus tubers (23.4%). Chara spp. and Elodea canadensis were eaten approximately in proportion to their abundance on winter ranges. Potamogeton pectinatus tubers accounted for only 0.5% of the biomass of aquatic plants present on wintering areas, yet comprised 23.4% of the diet. Swans ate more tubers (38.5%, P=0.1) in the spring compared to winter.
Based on the true metabolizable energy (TMEn), digestive efficiency, and nutritional characteristics (protein and NDF), the winter and spring foods in declining order of quality were: Potmogeton pectinatus tubers, Elodea canadensis, Chara spp., Myriophyllum exalbescens, and Ceratophyllum demersum. The average throughout time for all forages was 239 min. Swans passed food quickly with low digestive effiiency.
Swans increased their feeding time from 29.6% in the winter to 44.5% in the spring. During the winter, swans fed little in the morning (0.169) and increased their feeding rate throughout the day until night, when they fed at their highest rate (0.494). Wintering swans reduced feeding at a high rate throughout the day and night suggesting spring-use areas were important in establishing endogenous reserves for reproduction. Although endogenous reserves affect swan productivity (Anderson-Harild 1981, Bacon and Anderson-Harild 1989, Beekman 1991), the quality of nesting territories was also an important factor affecting swan productivity. Productive pairs occupied nest sites with a greater macrophyte biomass compared with nonproductive pairs. Females of productive pairs also appeared to take shorter recesses from incubation and incubated longer compared to females of nonproductive pairs. Invertebrate biomass did not differ between productive and nonproductive pairs. |
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| URLADDRESS | http://uwadmnweb.uwyo.edu/fish_wild/abstracts/squires_j/index.html |
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Posted on
Sun, July 31, 2011
by Beringia South