Human disturbance of <scp>B</scp>ewick's <scp>S</scp>wans is reflected in giving‐up net energy intake rate, but not in giving‐up food density

Gyimesi, Abel; Franken, Marycha S.; Feige, Nicole; Nolet, Bart A.

doi:10.1111/j.1474-919x.2012.01253.x

Cited by 17 publications

(11 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The observed result that bird herbivory was associated with smaller changes in plant abundance relative to most other taxa may be linked to inequalities in the movement ability of these taxa. Birds are highly mobile consumers which can, and frequently do, move between foraging sites in response to changes in site profitability (Nolet et al, 2001;Gyimesi et al, 2012;Wood et al, 2013). At foraging sites where plant abundance becomes substantially depleted birds, unlike the other taxa in our study, can abandon the site and fly elsewhere.…”

Section: Discussionmentioning

confidence: 87%

Herbivore regulation of plant abundance in aquatic ecosystems

et al. 2016

View full text Add to dashboard Cite

Herbivory is a fundamental process that controls primary producer abundance and regulates energy and nutrient flows to higher trophic levels. Despite the recent proliferation of small-scale studies on herbivore effects on aquatic plants, there remains limited understanding of the factors that control consumer regulation of vascular plants in aquatic ecosystems. Our current knowledge of the regulation of primary producers has hindered efforts to understand the structure and functioning of aquatic ecosystems, and to manage such ecosystems effectively. We conducted a global meta-analysis of the outcomes of plant-herbivore interactions using a data set comprised of 326 values from 163 studies, in order to test two mechanistic hypotheses: first, that greater negative changes in plant abundance would be associated with higher herbivore biomass densities; second, that the magnitude of changes in plant abundance would vary with herbivore taxonomic identity. We found evidence that plant abundance declined with increased herbivore density, with plants eliminated at high densities. Significant between-taxa differences in impact were detected, with insects associated with smaller reductions in plant abundance than all other taxa. Similarly, birds caused smaller reductions in plant abundance than echinoderms, fish, or molluscs. Furthermore, larger reductions in plant abundance were detected for fish relative to crustaceans. We found a positive relationship between herbivore species richness and change in plant abundance, with the strongest reductions in plant abundance reported for low herbivore species richness, suggesting that greater herbivore diversity may protect against large reductions in plant abundance. Finally, we found that herbivore-plant nativeness was a key factor affecting the magnitude of herbivore impacts on plant abundance across a wide range of species assemblages. Assemblages comprised of invasive herbivores and native plant assemblages were associated with greater reductions in plant abundance compared with invasive herbivores and invasive plants, native herbivores and invasive plants, native herbivores and mixed-nativeness plants, and native herbivores and native plants. By contrast, assemblages comprised of native herbivores and invasive plants were associated with lower reductions in plant abundance compared with both mixed-nativeness herbivores and native plants, and native herbivores and native plants. However, the effects of herbivore-plant nativeness on changes in plant abundance were reduced at high herbivore densities. Our mean reductions in aquatic plant abundance are greater than those reported in the literature for terrestrial plants, but lower than aquatic algae. Our findings highlight the need for a substantial shift in how biologists incorporate plant-herbivore interactions into theories of aquatic ecosystem structure and functioning. Currently, the failure to incorporate top-down effects continues to hinder our capacity to understand and manage the ecological dynamics of habitats ...

show abstract

Section: Discussionmentioning

confidence: 87%

Herbivore regulation of plant abundance in aquatic ecosystems

et al. 2016

View full text Add to dashboard Cite

show abstract

“…higher giving‐up densities) (Gyimesi et al . ). Indeed, food biomass is relatively high at these disturbed sites before the Bewick's Swans arrive in the area in autumn (i.e.…”

Section: Discussionmentioning

confidence: 97%

Lower foraging efficiency of offspring constrains use of optimal habitat in birds with extended parental care

Nolet

Gyimesi

Lith

2014

Ibis

Self Cite

View full text Add to dashboard Cite

After reproducing successfully, birds with extended parental care form family groups. Despite being the dominant social unit, such family groups have been reported to switch to alternative habitat earlier than adults without offspring, with potential negative carry‐over effects for the next breeding season. Here we test a proposed mechanism for this earlier habitat switch, namely a low foraging efficiency in juveniles. Such a test is best performed under controlled conditions because in the field families may occupy food patches of a different quality than singles or pairs without young. We studied this mechanism in Bewick's Swans Cygnus columbianus bewickii, which trample (or ‘treadle’) for food buried in the sediment. The gross intake rate of juveniles was as low as 60% of that of adults, depending on the burial depth of the food. Trampling effort did not differ between age classes, but differences in intake rate were related to body size, suggesting that larger or heavier birds were trampling more efficiently. Corresponding giving‐up densities in the field were calculated to be c. 60% higher for juveniles than for adults. Our findings are consistent with the hypothesis that the lower foraging efficiency of juveniles may be responsible for the segregation of family groups from adults without offspring.

show abstract

“…This metric was obtained from the DigitalGlobe high resolution imagery produced in January 2012 and offered by Google Earth™. The distance from human settlement may influence guild abundances because of its effect on bird site permanency (Glover et al, 2011;Gyimesi et al, 2012;Peters and Otis, 2007).…”

Section: Habitat Variablesmentioning

confidence: 99%