Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xvi, 161 p. : ill. (some col.), maps (some part col.). Includes abstract. Includes bibliographical references.

Mute swans (Cygnus olor), an exotic species of waterfowl, have been found to negatively impact native waterbirds and submerged aquatic vegetation (SAV) communities in the Chesapeake Bay and lower Great Lakes. Mute swans were first recorded in Illinois in 1971 and their population is small, but growing. In 2008-09, I studied mute swans in central Illinois to investigate whether they negatively impacted waterbirds through aggressive actions and SAV through over-grazing. I also estimated mute swan territory size to estimate potential habitat exclusion and population growth potential. Mute swan territory size averaged 7.0 ha, allowing the current population of approximately 60 breeding pairs to increase to over 125 pairs. I did not find that mute swans reduced above-ground SAV, although I did find that below-ground biomass was reduced where mute swans fed freely. Mute swan aggression was most frequent in early spring and decreasing throughout the breeding season. Most waterbirds were found just as close or closer to mute swans as to control points, although gadwall (Anas strepera) were found farther away perhaps suggesting either avoidance or exclusion. As mute swans become more abundant in Illinois, further monitoring is necessary to prevent significant negative impacts to wetlands and waterbirds.

2009 metais devyniolikoje (su padaliniais dvidešimt viename) Lietuvos žuvininkystės ūkių buvo vykdomi gulbių nebylių sankaupų gausos, formavimosi sezoninės dinamikos ir pasiskirstymo ypatumų tyrimai. Tyrimai užpildo eilę spragų ankstesniuose tyrimuose apie gulbių nebylių sankaupų formavimąsi žuvų tvenkiniuose. Sankaupų formavimosi laikotarpiu žuvų auginimo tvenkiniais naudojasi apie tris tūkstančius neperinčių gulbių nebylių. Paukščiai čia apsistoja sezoninių migracijų metu. Taip pat čia susirenka šertis nesiveisiantys individai. Gulbių buvimo žuvininkystės ūkių tvenkiniuose trukmę apsprendžia tvenkinių pripildymo (balandžio mėn.) ir nuleidimo (intensyviausiai rugsėjo antroje - spalio pirmoje pusėje) laikotarpiai. Sankaupos gausiausios pavasario pabaigoje - vasaros pradžioje, visų pirma birželio mėnesį, tačiau jų dydis atskiruose ūkiuose ženkliai svyruoja ir gali piką pasiekti ir kitais sezono laikotarpiais, ypač rudeniop. Stabiliai pagrindiniu, sankaupų dydį konkrečiuose žuvų ūkiuose apsprendžiančiu, veiksniu yra bendras tvenkinių, kuriuose buvo beriami žuvų pašarai, plotas. Ūkiuose (jų grupėse), kuriuose šio faktoriaus skaitinė reikšmė didelė, gulbių nebylių sankaupos taip pat didelės ir atvirkščiai. Tačiau atsitiktinė natūralių buveinių su gausiomis gulbių nebylių sankaupomis (pavyzdžiui Kuršių Marių) kaimynystė (geografinis faktorius), gali nusverti anksčiau minėto faktoriaus poveikį. Gulbės sankaupose naudoja didžiąją dalį konkretaus, ūkio tvenkinių (paprastai 50-70 %) –... [toliau žr. visą tekstą] / In 2009, research was carried out on abundance of mute swan flocks, its formation, seasonal dynamics and distribution characteristics in nineteen (with branches in twenty-one) fish farms in Lithuania. This research fills-in a number of gaps of previous studies on mute swan flocks formation in fish farm ponds. Around three thousand non breeding mute swans are using fish farming ponds during flock’s formation season. Birds stay here during seasonal migrations. Also non breeding swans gather here to moult. The duration of stay of swans in fish farm ponds is determined by the time of filling up (in April) and draining (most intensive in the second half of September and in the first half of October) of ponds. The most numerous flocks are at late spring - early summer, particularly in June, but the size of individual flocks vary considerably and may reach peak during other periods of the season, especially in autumn. The most stable factor determining size of the specific flock in fish farm ponds is area of the pond where fish are fed. Flocks are more numerous in farms (or groups of farms) in which value of this factor is higher and vice versa. However, random natural dwellings of mute swan flocks with large populations (for example neighborhood of Kuršių Marios – geographical factor) may outweigh the above factor’s impact on mute swans flock size in fish ponds. Flocks of mute swans cluster during the mobilization period and use most part of the fish farm pond (usually 50-70%) –... [to full text]

Dans certains cas, la colonisation des zones humides par les espèces animales et végétales peut être une menace majeure pour la biodiversité. Il est donc primordial de mieux connaître l'écologie des espèces colonisatrices pour définir leurs relations avec le reste de l'écosystème. Nous avons étudié les conséquences de la colonisation relativement récente des étangs piscicoles français par le cygne tuberculé (Cygnus olor). Nous nous sommes intéressés à l'expression de cette colonisation dans l'espace par l'étude des processus de sélection de l'habitat. Nos résultats montrent que dans un paysage d'étangs, la répartition des cygnes tuberculés dépend à la fois de la configuration spatiale des étangs (aire isolement), des ressources disponibles et du statut de reproduction des cygnes tuberculés. Nous avons ensuite étudié les interactions entre le cygne tuberculé et les communautés animales et végétales des étangs. Sur les sites de cantonnement des couples, nous n'avons pas montré d'effet de la présence des cygnes tuberculés sur l'abondance des oiseaux d'eau, et aucune forme d'exclusion spatiale à l'échelle de l'étang. En revanche, les cygnes tuberculés peuvent générer une déplétion significative des herbiers de macrophytes aquatiques, suggérant des effets en cascade sur les autres communautés des étangs piscicoles. Comme toute perturbation générée par une espèce colonisatrice, celle associée à l'arrivée des cygnes doit néanmoins être replacée dans le contexte plus large des régimes de perturbations à l'oeuvre sur l'écosystème, ce qui importe particulièrement dans le cas d'écosystèmes aussi dépendants de l'activité humaine que les étangs piscicoles. / In some cases, wetland colonization by animals and plants may be a major threat to biodiversity. It is therefore crucial to better understand the ecology of colonizing species to assess their relationships with the other elements of ecosystems. We studied the consequences of the relatively recent colonization of French fishponds by mute swan (Cygnus olor). We especially considered how such colonization now translates into space, through the analysis of habitat selection processes. Our results show that swan distribution within a fishpond landscape depends on fishpond spatial configuration (area isolation), available resources as well as mute swan breeding status. We then analysed the relationships between mute swan and fishpond animal and plant communities. Where swan pair settle, we do not demonstrate any effect of swan presence on the abundance of other waterbirds, nor any spatial exclusion within fishponds. Conversely, mute swans can signif icantly deplete aquatic macrophyte beds, suggesting cascade effects on other fishpond communities are possible. Like any perturbation caused by a colonizing species, that associated with swan arrival however has to be considered in the broader context of perturbation regimes onto the ecosystem. This is especially crucial in ecosystems like fishponds, that are so much dependent upon human activity.