Interactions between coot (Fulica atra) and submerged macrophytes: the role of birds in the restoration process

Abstract

Interactions between coot (Fulica atra) and submerged macrophytes: the role of birds in the restoration process. Perrow, M.R.; Schutten, J.; Howes, J.R.; Holzer, T.; Madgewick, F.J.; Jowitt, A.J.D. Published in: Hydrobiologia Link to publicationCitation for published version (APA): Perrow, M. R., Schutten, J., Howes, J. R., Holzer, T., Madgewick, F. J., & Jowitt, A. J. D. (1997). Interactions between coot (Fulica atra) and submerged macrophytes: the role of birds in the restoration process. Hydrobiologia, 242/243, 241-255. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractGrazing by herbivorous birds is often cited as an important factor in suppressing macrophyte development in shallow lakes undergoing restoration, thus delaying the attainment of the stable clear water state. Development and succession of macrophyte communities and size, diet and grazing pressure of coot (Fulica atra) populations upon macrophytes, were monitored over the seasonal cycle at ten shallow lakes of varying nutrient status, in the Norfolk Broads in eastern England. In spring, territorial breeding birds were at relatively low density and included only a small proportion of macrophytes in their diet, resulting in low grazing pressure on macrophytes. In summer, there was a significant relationship between macrophyte cover and bird density, illustrating the importance of macrophytes in the dispersion phase for birds following breeding. Macrophytes comprised the bulk of bird diet where they were available and the consumption of macrophytes was up to 76 fold higher than in spring. However, losses to grazing in both periods were negligible when compared to potential growth rates documented in the literature. Grazing experiments at two biomanipulated lakes confirmed that birds were not responsible for limiting macrophytes during the spring colonisation phase or in the summer growth period. During the period of autumnal senescence and over the winter months where some macrophyte species remain available, e.g. as developed individuals or dormant buds, grazing by birds may conceivably have an impact on the development and structure of macrophyte populations in subsequent growing seasons.The relative importance of bird grazing compared to other factors limiting the development of macrophytes...

The impact of bird herbivory on macrophytes and the resilience of the clear-water state in shallow lakes: a model study

“…the relative change of macrophyte biomass compared to the situation without birds, has been used in many field studies with exclosure experiments (e.g. Perrow et al, 1997;Hilt, 2006;Hidding et al, 2010). The outcomes of these experiments were extremely variable, with bird impact ranging from zero or a few percent difference to 100% difference (i.e.…”

“…Perrow et al, 1997;Wood et al, 2012).The amount of macrophyte biomass that is grazed by coots, G (g dry weight m -2 d -1 ), is modelled with a Holling type II functional response as…”

“…Some studies found that herbivory by birds decreased macrophyte biomass severely, even up to 100% (Sondergaard et al, 1996;Hilt, 2006;Wood et al, 2012;Bakker & Nolet, 2014), while others found that the removed biomass is compensated by macrophyte regrowth (Mitchell & Wass, 1996;Perrow et al, 1997;Hansson et al, 2010). This apparent contradiction may arise from the varying conditions under which these studies have been conducted, such as the macrophyte and the bird species under consideration, or the experimental set-up (Perrow et al, 1997;Bakker et al, 2013). A recent meta-analysis of all available field studies demonstrated that the impact of herbivory by birds on aquatic plants increases with bird biomass density, offering the first proof that birds systematically reduce macrophyte biomass when present at sufficient densities (Wood et al, 2012).…”

“…It has been hypothesized that the impact of grazing birds on macrophytes varies with the nutrient status of the lake (Perrow et al, 1997;Weisner et al, 1997;Hansson et al, 2010;Bakker & Nolet, 2014). Possible mechanisms for this could be that under eutrophic conditions plants have a higher nutrient content relative to their carbon content, making them more preferred food (Bakker & Nolet, 2014), and that plants have less tolerance to grazing due to increased periphyton growth on the macrophytes (Weisner et al, 1997;Hilt, 2006;Hidding et al, 2010).…”

Restoring macrophyte diversity in shallow temperate lakes: biotic versus abiotic constraints

“…Experiments where macrophytes were transplanted in restored lakes showed that herbivores (large fish and waterfowl) strongly reduced macrophyte biomass (Lauridsen et al, 1993;Sondergaard et al, 1996;Lauridsen et al, 2003b;Irfanullah & Moss, 2004;Van de Haterd & Ter Heerdt, 2007;Moore et al, 2010). However, Perrow et al (1997) and Strand & Weisner (2001) found no significant reduction due to herbivory by fish and birds in restored lakes of the biomass of macrophytes that had developed spontaneously, whereas Hilt (2006) found a more than 90% reduction of P. pectinatus vegetation through grazing. Even if the herbivores do not completely prevent the colonisation of macrophytes, they may retard the vegetation development.…”