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Feeding Habits of Swans
most of the translocated swans return to the original places the following year.
N American Swans
1) Agricultural plants
- High carbohydrates
2) Wetland plants
- Lower carbohydrates than ag. ｐlants
- Some high water & high fiber content
3) Animal matter
- High protein
- Swans eat tubers, seeds, ….
- Foraging swans go to find pondweeds.
(Earnst & Rothe 2004)
- Eelgrass or Wild celery (Vallisneria spp.)
- Widgeon grass (Ruppia spp.)
- Muskgrass or Skunkweed (Chara spp.)
Eelgrass or Wild celery
Muskgrass or Skunkweed
- Management for recreation
- Low enforcement
from <200 (1935) to 2200 (1993) .
(Baskin 1993, Squires & Anderson 1995)
from 200 (1955) to 5300 (1987), 12600 (1999).
(Conover & Kania 1994, USGS Website 2001)
increased since 1940s, Western 50000(1958),
60000 (2005). (Eastern 100000)
(Sherwood 1960, ADFG Website 2005)
USGS Website 2001
Noordhuis et al. 2002.
Mute & Bewick’s swan
(21-34%: Mitchell & Wass 1995)
- Eat a lot.
- Possible to destroy ecosystem in wetlands.
- And compete with other animals.
1) Significant damage to aquatic plants.
2) Conflict with other shorebirds.
Mitchell & Wass 1996.
Slow down the succession of wetlands.
- Black-necked swan might play an important role as a regulator of aquatic plant biomass to cause a delay in ecological succession (Corti & Schlatter 2002).
- 40% of N and 75% of P in a wetland (Post et al 1998).
- Prefer places with
high food densities & low competition.
Swans visit high food density patches at a higher frequency.
Strong negative correlation b/w the number of swan-days and the number of goose- and wigeon-days (reduction in the food supply).
Food supply decrease make smaller flocks and graze at several different sites. (Klaassen et al. 2006).
- aquatic plants waste grains.
Bewick’s swan: max depth is 0.89m, but prefer shallower water like <0.45m.
Nolet et al. 2006
(New Zealand: Mitchell & Wass 1996)
(Noordhuis et al. 2002)
Badzinski et al. 2006.
When different herbivores with similar food requirements live within the same ecosystem, the animal may not compete but form a grazing succession, where the feeding activity of one group improved conditions for other species present (Vesey-Fitzgerald 1960, Jarman & Sinclair 1979, Mddock 1979).
Destroyer or Succession regulator.