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Vol. 48 No. 6, 2009
Effects
of Vegetative Cover Changes on the Carrying Capacity of Migratory
Shorebirds in a Newly Formed Wetland, Yangtze River Estuary, China
Zhen-Ming Ge1,2,*, Xiao Zhou1,2, Tian-Hou Wang1, Kai-Yun Wang1, Enle Pei3,4, and Xiao Yuan3,4
1School
of Life Sciences, Shanghai Key Laboratory of Urbanization and
Ecological Restoration, East China Normal University, Shanghai 200062,
China
2Faculty of Forest Sciences, University of Joensuu, P.O. Box 111, FI-80101 Joensuu, Finland
3Department of Wildlife Protection Administration, Shanghai 200233, China
4Chongming Dongtan Bird Nature Reserve, Shanghai 202150, China
Zhen-Ming Ge, Xiao Zhou, Tian-Hou Wang, Kai-Yun Wang, Enle Pei, and Xiao Yuan (2009) The
Jiuduansha wetland is a shoal which formed in the Yangtze River estuary
during the 1940s. Shorebird surveys were conducted at Jiuduansha
wetland in 2004-2005 during the spring (northerly) and autumn
(southerly) migration seasons. Over 6000 individuals of 25
shorebird species were recorded at the wetland during spring and 3000
birds during autumn. Their preferred roosting habitat was the
bare mudflat and bulrush (Scirpus × mariqueter and S. triqueter)
zones. The carrying capacity of the wetland for shorebirds based
on the available foraging resources of medium-sized macrobenthos was
estimated during the spring and autumn of 2006. Thirty species of
macrobenthos were identified and defined as potentially appropriate
food for shorebirds at Jiuduansha, comprised mostly of mollusks,
crustaceans, and annelids (polychaetes). The total standing
benthic invertebrate crop was 1973.64 kg ash free dry weight (AFDW) in
spring and 1557.28 kg AFDW in autumn. We calculated that this
could theoretically support about 1.51 × 106 bird-days (the number of
birds present) in spring and 1.20 × 106 bird-days in autumn.
However, field surveys in 2006 indicated that only 10% of the standing
crop of biomass was available to shorebirds, and that the actual
carrying capacities were about (0.15 and 0.12) × 106 bird-days in
spring and autumn, respectively. Actual shorebird abundances at
Jiuduansha were significantly lower than the theoretical carrying
capacity. Furthermore, satellite imagery from 1998-2006 indicated
that an introduced species of smooth cordgrass Spartina alterniflora
has rapidly spread, invading the bare mudflat and bulrush zones.
This has reduced the availability of suitable high-tide roosting
habitat, and may be the key factor, rather than food availability,
limiting use of the area by shorebirds. We provide
recommendations for the management of Jiuduansha wetland to benefit
shorebirds and other waterbird species.
Key words: Recently formed wetland, Shorebirds, Macrobenthos, Change in vegetative cover, Spartina alterniflora.
*Correspondence: Tel and Fax: 86-21-62233012. E-mail:zmge@bio.ecnu.edu.cn
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