Effects of seasonality, isolation and patch quality for habitat selection processes by mute swans Cygnus olor in a fishpond landscape

Abstract

Foragers in patchy environments do not only select sites for single patch characteristics, but also have to consider the local environment of such patches. We studied habitat selection by mute swans Cygnus olor in a wide and heterogeneous fishpond region (the Dombes, eastern France). In this study, we considered fishpond isolation, resource quality within fishponds and breeding status of mute swans during both summer and winter. Mute swans did not select aquatic habitat randomly within the landscape. During summer, the population spread preferentially on medium to large fishponds, in subregions with numerous or closely related waterbodies, without generating a clumped distribution of birds. In addition to a positive effect of local fishpond number (2 km radius), breeding birds also responded positively to fishpond size. Non‐breeders selected fishponds mainly according to their size. Intraspecific territoriality did not appear to limit the presence of non‐breeders (i.e. moulting flocks), since both breeders and non‐breeders could coexist on the larger fishponds. During winter, mute swans used medium to large reflooded fishponds after summer drainage. The surrounding aquatic environment of fishponds played a minor role in determining flocking, compared to actual patch quality. Flocking occurred on large fishponds that had reflooded after having dried the summer before, whatever the agricultural cultivation practiced in the summer following drainage. The results suggest that geographical aspects should be taken into account when considering the potential impact of this expanding species within such ecosystems, and also in more general management policies dealing with aquatic habitats for waterbird populations.

The role of season and social grouping on habitat use by Mute Swans (Cygnus olor) in a lowland river catchment

“…Freshwater habitats offer both abundant plant food and security for cygnets from terrestrial predators during the breeding period, making them attractive breeding habitats and therefore territories (Birkhead & Perrins 1986). Lakes in particular are known as a key breeding habitat for swans and so the preference we observed of territorial birds for lake habitat was expected (Birkhead & Perrins 1986, Tuite et al 1984, Gayet et al 2011b. Territorial individuals continued to exhibit a preference for river habitat even during periods of high flow in winter, presumably because of the need to defend it from other pairs due to the strong competition for territories among swans (Scott 1984).…”

“…Nonterritorial swans are highly mobile and are observed to move between feeding sites frequently, whereas territorial groups typically exhibit a high fidelity to a particular area (Birkhead & Perrins 1986, Holm 2002, Gayet et al 2011b. Management which manipulates the relative quality of the grazed and adjacent habitats may be effective in shifting non-territorial groups away from the grazed area at any time (Vickery et al 1994, but is only likely to be effective for territorial groups if carried out before nest-site selection, because after this time movement will be highly restricted due to the low dispersal ability of the young (Birkhead & Perrins 1986).…”

Invasive birds: global trends and impacts

“…The Mute Swan can use a wide variety of wetland habitats: slow-flowing rivers, fluvial canals, lakes, fishponds, coastal marine habitats, gravel pits and urban ponds, with farmland also important for grazing (Kirby et al, 1994;Rees et al, 1997;Petersen, 2000;Rowell and Spray, 2004;Fouque et al, 2007). Although habitat use may vary markedly with the time of year and the swans' breeding status (Gayet et al, 2011a(Gayet et al, , 2013Wood et al, 2013), Mute Swans demonstrate a high level of ecological plasticity, which explains their ability to colonize these diverse habitats within their native range in recent decades (Wieloch, 1991;Fouque et al, 2007). Indeed, these birds have few strict requirements for establishing breeding sites (Gayet et al, 2011b), and can readily rely on agricultural crops for feeding during winter in addition to their more traditional use of wetland habitats (e.g.…”

“…as breeding or flocking sites), it has been postulated that their effects on plants could be cumulative, although a recent study found no evidence for Mute Swan grazing impacts carrying over into the following year (Wood et al, 2018). It is additionally suggested that the swans could cause chronic disturbance, potentially affecting the whole ecosystem through trophic cascades, given the critical role of plants on biogeochemical functioning and as habitat for a range of animals (Tatu et al, 2006;Gayet et al, 2011a), but such potential effects have been poorly studied. It should also be noted, however, that Mute Swan grazing does not invariably have negative consequences for the vegetation: some studies found no evidence for a significant impact on the plants (e.g.…”

Suitability evaluation of habitat for ardeidae waterfowls based on logistic regression model

“…Based on the selecting principle of suitability evaluation factors of habitat and dependency of ardeidae waterfowls in wetland on habitat [14], the current study established an evaluation index system of the habitats of ardeidae waterfowls by integrating relative field investigation data and measured data on waterfowls and combining such data with the effects of local natural conditions and human activities on the habitats of waterfowls. The selection of model argument was divided into four aspects as follows: Based on the digital elevation model (DEM) data of the Hong Kong area, the DEM, gradient, and aspect figure reflecting the terrain of the research area were obtained, with the support of geographic information system (GIS) technology, to analyze the topographic features of the research area.…”