Browsing by Subject "Castor canadensis"

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  • Sola, Petri (Helsingfors universitet, 2013)
    Tutkimuksessa selvitettiin varpuslintujen pesimäaikaista esiintymistä ja siihen vaikuttavia tekijöitä majavien patoamilla tulva-altailla (12 kpl) ja majavatoiminnan ulkopuolisilla kontrollikosteikoilla (12 kpl). Myös muun linnuston esiintymistä selvitettiin. Tutkimusalue sijaitsi Kanta-Hämeessä Lammin Evolla. Lintulaskennat suoritettiin pistelaskentamenetelmällä alkukesinä 2008 ja 2009. Linnut jaoteltiin laskentaympyrän (r=50m) sisä- ja ulkopuolisiin ja sisäpuolelta kerättiin tiedot kohteen puustosta ja biotoopista. Erot majava- ja kontrollikosteikkojen varpuslinnustoissa tulivat selkeimmin esiin tarkasteltaessa laskentaympyrän sisäpuolisia määriä. Parimäärä, lajimäärä sekä lehvästössä ruokailevien, ilmasta saalistavien ja rastaiden parimäärät olivat majavakosteikoilla tilastollisesti merkitsevästi suuremmat kuin kontrollikosteikoilla. Pajulintu oli ainoa laji, jonka parimäärä oli tilastollisesti merkitsevästi suurempi majavakosteikoilla, kun tarkastelualueena oli koko laskenta-alue. Kololinnut olivat ainoa lajiryhmä, joita esiintyi kontrollikosteikoilla enemmän kuin majavakosteikoilla. Koko linnuston laji- ja parimäärät olivat majavakosteikoilla laskentaympyröiden sisäpuolella tilastollisesti merkitsevästi suuremmat kuin kontrollikosteikoilla. Koko linnuston diversiteetti oli majavakosteikoilla huomattavasti suurempi kuin kontrollikosteikoilla, mutta varpuslintujen osalta diversiteeteissä ei ollut eroja. Varpuslintujen pari- ja lajimääriä selittivät lehtipuuston osuus kasvattavasti ja kuusen osuus vähentävästi, mutta tulokset eivät olleet tilastollisesti merkitseviä.
  • Nummi, Petri; Arzel, Celine; Sauramo, Virva (2021)
    Stability of breeding habitat use and population variability was studied in two common wader species: green sandpiper Tringa ochropus and common sandpiper Actitis hypoleucos in a boreal lake area in southern Finland. The main natural driver of habitat disturbance in the area is an ecosystem engineer, the North American beaver Castor canadensis. We also studied the presence and abundance of green sandpipers before, during and after beaver-induced floods. In the studied landscape, the variable habitat created by beaver flooding appeared to have carrying capacity for a larger green sandpiper population than the more stable habitat for that of the common sandpiper. Common sandpipers made much use of the same lakes from year to year whereas the occupation of wetlands by the green sandpiper was more variable. The population of common sandpipers fluctuated more, although they inhabited the more stable environment. Green sandpiper pair numbers increased during beaver flooding, which suggests that they adapt rapidly to changes in breeding site availability. Some of the facilitating effects of the beaver appeared to remain 1-2 years after the flooding.
  • Nummi, Petri; Holopainen, Sari (2020)
    Wetlands are declining worldwide, and there is a great need for their restoration and creation. One natural agent of wetland engineering is beavers,Castorspp., which have returned or are returning to many parts of their former range. We initially studied the facilitative effect of the beaverCastor canadensison a waterbird community consisting of three waders and four ducks in boreal wetlands in southern Finland. Both waterbird species diversity and abundance increased when beavers impounded a pond. Common tealAnas creccaand green sandpiperTringa ochropuswere the species showing the most positive numerical response, but the other five species also increased upon flooding. This article evaluates how the results of the study have been used in management, both in theory and practice. The whole-community facilitation concept has been taken up in numerous articles considering the restorative effects of beavers. It has also been used as ecological background when planning and executing man-made wetland projects in Finland within both the public and the private sectors. Our study and its publication inAquatic Conservation: Marine and Freshwater Ecosystemshave set a foundation for further evidence-based management of waterbird communities. As the results show, having beavers as wetland managers is a feasible tool for creating and restoring wetlands for waterbirds and other biota. Moreover, wetland restoration projects are becoming more popular endeavours, owing to an understanding of the diverse benefits of wetlands. Flooding by beavers is used as a model for managers when creating man-made wetlands; for example, in urban areas where it is difficult to maintain beavers.
  • Nummi, Petri; Suontakanen, Eeva-Maria; Holopainen, Sari; Väänänen, Veli-Matti (2019)
    Avian species respond to ecological variability at a range of spatial scales and according to life history stage. Beaver dams create wetland systems for waterbirds that are utilized throughout different stages of the breeding season. We studied how beaver?induced variability affected mobile pairs and more sedentary broods along with the production of Common Teal Anas crecca at the patch and landscape scale on their breeding grounds. Beavers Castor spp. are ecosystem engineers that enhance waterfowl habitats by impeding water flow and creating temporary flooding. Two landscapes in southern Finland with (Evo) and without (Nuuksio) American Beavers Castor canadensis were used in this study. To investigate the patch?scale effect, pair and brood densities along with brood production were first compared at beaver?occupied lakes and non?beaver lakes in the beaver landscape. Annual pair and brood densities/km shoreline and brood production were compared between beaver and non?beaver landscapes. Facilitative effects of beaver activity were manifest on brood density at both patch and landscape scales: these were over 90 and 60 percent higher in beaver patches and landscapes, respectively. An effect of beaver presence on pair density was only seen at the landscape level. Pair density did not strongly affect brood production, as shown earlier for relatively mildly density?dependent Teal populations. Because the extent of beaver flooding was a crucial factor affecting annual Teal production in the study area, we infer beaver activity has consequences for the local Teal population. Ecosystem engineering by the beaver could therefore be considered as a restoration tool in areas where waterfowl are in need of high?quality habitats. This article is protected by copyright. All rights reserved.