Impacts of Mute Swans (Cygnus olor) on Submerged Aquatic Vegetation in Illinois River Valley Backwaters

Stafford, Joshua D.; Eichholz, Michael W.; Phillips, Adam C.

doi:10.1007/s13157-012-0316-6

Cited by 11 publications

(6 citation statements)

References 25 publications

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“…By any estimate, these values are clearly lower than rates reported in aquatic systems, where herbivores have been shown to consume between 30-80% of primary production on average (Lodge 1991, Cyr and Pace 1993, Burkepile 2013, Gruner and Mooney 2013. At the highest extremes, large aquatic herbivores can consume well above 100% of annual primary production (Heinsohn et al 1977, Preen 1995, Masini et al 2001, Skilleter et al 2007) (Conover and Kania 1994, Allin and Husband 2003, O'Hare et al 2007, Tatu et al 2007, Hidding et al 2009, 2010a, 2010b, Gayet et al 2011, Wood et al 2012b, Stafford et al 2012) and diversity (95%) in grazed plots (Qvarnemark and Sheldon 2004) productivity, modifying geomorphology, altering nutrient cycling and transport of organisms.…”

Section: Impact On Aquatic Vascular Plant Abundance and Species Compomentioning

confidence: 84%

Assessing the role of large herbivores in the structuring and functioning of freshwater and marine angiosperm ecosystems

et al. 2015

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While large herbivores can have strong impacts on terrestrial ecosystems, much less is known of their role in aquatic systems. We reviewed the literature to determine: 1) which large herbivores (> 10 kg) have a (semi‐)aquatic lifestyle and are important consumers of submerged vascular plants, 2) their impact on submerged plant abundance and species composition, and 3) their ecosystem functions. We grouped herbivores according to diet, habitat selection and movement ecology: 1) Fully aquatic species, either resident or migratory (manatees, dugongs, turtles), 2) Semi‐aquatic species that live both in water and on land, either resident or migratory (swans), 3) Resident semi‐aquatic species that live in water and forage mainly on land (hippopotamuses, beavers, capybara), 4) Resident terrestrial species with relatively large home ranges that frequent aquatic habitats (cervids, water buffalo, lowland tapir). Fully aquatic species and swans have the strongest impact on submerged plant abundance and species composition. They may maintain grazing lawns. Because they sometimes target belowground parts, their activity can result in local collapse of plant beds. Semi‐aquatic species and turtles serve as important aquatic–terrestrial linkages, by transporting nutrients across ecosystem boundaries. Hippopotamuses and beavers are important geomorphological engineers, capable of altering the land and hydrology at landscape scales. Migratory species and terrestrial species with large home ranges are potentially important dispersal vectors of plant propagules and nutrients. Clearly, large aquatic herbivores have strong impacts on associated species and can be critical ecosystem engineers of aquatic systems, with the ability to modify direct and indirect functional pathways in ecosystems. While global populations of large aquatic herbivores are declining, some show remarkable local recoveries with dramatic consequences for the systems they inhabit. A better understanding of these functional roles will help set priorities for the effective management of large aquatic herbivores along with the plant habitats they rely on.

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Section: Impact On Aquatic Vascular Plant Abundance and Species Compomentioning

confidence: 84%

Assessing the role of large herbivores in the structuring and functioning of freshwater and marine angiosperm ecosystems

et al. 2015

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“…Simultaneously, the growth rate of aquatic plants in temperate rivers declines after the spring period of growth [12], [22]; thus plants experienced the highest grazing pressures when they were senescing and thus their capacity for compensatory growth was low [12], [22]. This led to substantial reductions in plant abundance as have been reported for other aquatic ecosystems [50], [51], [52]. The positive relationship between swan biomass density and species evenness in the peak-phase, suggested grazing of the more naturally-abundant species [29].…”

Section: Discussionmentioning

confidence: 91%

Understanding Plant Community Responses to Combinations of Biotic and Abiotic Factors in Different Phases of the Plant Growth Cycle

et al. 2012

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Understanding plant community responses to combinations of biotic and abiotic factors is critical for predicting ecosystem response to environmental change. However, studies of plant community regulation have seldom considered how responses to such factors vary with the different phases of the plant growth cycle. To address this deficit we studied an aquatic plant community in an ecosystem subject to gradients in mute swan (Cygnus olor) herbivory, riparian shading, water temperature and distance downstream of the river source. We quantified abundance, species richness, evenness, flowering and dominance in relation to biotic and abiotic factors during the growth-, peak-, and recession-phases of the plant growth cycle. We show that the relative importance of biotic and abiotic factors varied between plant community properties and between different phases of the plant growth cycle. Herbivory became more important during the later phases of peak abundance and recession due to an influx of swans from adjacent pasture fields. Shading by riparian vegetation also had a greater depressing effect on biomass in later seasons, probably due to increased leaf abundance reducing light intensity reaching the aquatic plants. The effect of temperature on community diversity varied between upstream and downstream sites by altering the relative competitiveness of species at these sites. These results highlight the importance of seasonal patterns in the regulation of plant community structure and function by multiple factors.

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“…For instance, aquatic plant cover was on average 79% lower, mean shoot density was 76% lower and canopy height was 40% lower in areas of the Chesapeake Bay grazed by swans (Tatu et al, 2006). In mid-continental American wetlands, Mute Swan effects on above-ground plant biomass could not be demonstrated after only 2 years of swan exclusion, but they were found to reduce below-ground plant biomass significantly, probably forecasting a future effect on above-ground biomass (Stafford et al, 2012). In other areas, emergent plants could potentially be uprooted by the swans (Chaichana et al, 2011).…”

Section: Impactsmentioning

confidence: 94%

“…Being such large herbivorous waterbirds, Mute Swans can potentially overgraze aquatic plants, generating conflicts with various stakeholders such as those managing habitats for other species, including hunters and fish farmers. Mute Swan feeding activity can reduce plant biomass substantially, in some cases leaving only bare sediment, and can also influence species dominance relationships within plant communities (Tatu et al, 2006;O'Hare et al, 2007;Sandsten and Klaassen, 2008;Gayet et al, 2011cGayet et al, , 2012Stafford et al, 2012). For instance, aquatic plant cover was on average 79% lower, mean shoot density was 76% lower and canopy height was 40% lower in areas of the Chesapeake Bay grazed by swans (Tatu et al, 2006).…”

Section: Impactsmentioning

confidence: 99%

Invasive birds: global trends and impacts

2020

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This 381-paged book covers the biology, ecology, impact and management of 34 common alien invasive species, with reviews on the history and context of avian introductions and invasions in five major regions (Oceania, Africa, Europe (including the Middle East, Asia and South America)), as well as management challenges and the potential of citizen science for monitoring alien birds. The book pitches at the introductory level and is ideal for readers to gain a quick and comprehensive view of the current status of global avian invasions. It has brought the records and research of avian invasion one step ahead of other alien invasive animal taxa. Many chapters contain distribution maps and data tables on the diet and morphology of the species, providing a good reference for the species and its management issues. Each chapter also contains a rich list of references that could help readers dive further into the topic.

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Impacts of Mute Swans (Cygnus olor) on Submerged Aquatic Vegetation in Illinois River Valley Backwaters

Cited by 11 publications

References 25 publications

Assessing the role of large herbivores in the structuring and functioning of freshwater and marine angiosperm ecosystems

Assessing the role of large herbivores in the structuring and functioning of freshwater and marine angiosperm ecosystems

Understanding Plant Community Responses to Combinations of Biotic and Abiotic Factors in Different Phases of the Plant Growth Cycle

Invasive birds: global trends and impacts

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