The effect of managed forest-wetland landscapes on forest grouse and nest predation
Date
2023-11-13
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Abstract
Metsakanaliste (metsis, teder ja laanepüü) elujõulised asurkonnad on märk maastiku terviklikkusest ning selliste maastike hoidmine kaitseb ka teisi liike. Põhja- ja Baltimaades on viimastel aastakümnetel looduslikke metsa-märgalamaastikke muudetud ulatuslike lage- ja harvendusraiete ning kuivendussüsteemidega: maastikud on muutunud ühetaolisteks killustunud metsadega aladeks, milles suureneb lindude pesarüüste. Koos muutustega on neis maastikes langenud ka metsakanaliste arv. Kõik kolm liiki eelistavad sama maastiku erinevaid elupaiku ning on tundlikud nii kiskluse kui ka metsamajanduse suhtes.
Uurisin, kuidas saab parandada kanaliste ellujäämisedukust. Selleks hindasin metsandusvõtete mõju pesarüüstele, ja millistes elupaikades on kanalised kõige tundlikumad kisklusele.
Raiesmikel ja noortes puistutes on pesarüüste väikseim, kuid metsis ja laanepüü väldivad selliseid alasid. Metsamaastiku raielankidega killustades võivad nii linnud kui ka kiskjad koonduda säilinud keskealise ja vana metsaga elupaigalaikudesse, mis suurendaks rüüstet veelgi. Kuivenduskraavidel kanalistele otsest mõju ei ole, kuid iga liik eelistab erinevat tüüpi soomullal olevat elupaika – sellise mullastiku esinemine eeldab aga kuivendamata metsa-märgalamaastikku.
Kanalistele on kõige sobimatumad väikesed kaitsealad, mille ümbruses majandatakse metsa erinevate võtetega, majandamata või minimaalselt majandatud loodusmaastikes saavad populatsioonid edukalt hakkama. Selliste maastike säilimine on kriitilise tähtsusega – isegi kui taastada kuivendatud elupaiku, on vahetult pärast taastamistöid kanaliste sigimisedukus väike ja pesarüüsterisk suur. Ajutist leevendust pakuks pesa rüüstavate väikekiskjate küttimine, kuid sel on vaid lokaalne ja lühiajaline mõju.
Viable forest grouse populations (capercaillie, black grouse and hazel grouse) indicate landscape integrity, and maintaining such landscapes also protects other species. In the Nordic and Baltic countries, natural forest-wetland landscapes have been transformed by extensive afforestation, thinning and drainage systems. During the recent decades, the named landscapes have been altered into patches of fragmented woodland with increasing nest predation risk in birds. Along with the changes, the populations of forest grouse in these landscapes have also declined. All three species prefer different habitats in the same landscape and are sensitive to predation and forest management. I investigated how to improve the species survival. For that, I evaluated which silvicultural practices increase nest predation, and in which habitats the species are most vulnerable to predation. Clearcuts and young stands have the lowest nest predation, but capercaillie and hazel grouse avoid these areas. Forest fragmentation by clearcuts can cause both birds and predators to concentrate into remained patches of middle-aged and old-growth forest, increasing thus predation risk. Drainage ditches do not have a direct impact on grouse, but each species prefers a different type of Histosols. Thus, the abundance of variuous Histosols requires undrained forest-wetland landscape. The most unsuitable habitat for grouse are small protected areas, surrounded by production forestry with various silvicultural techniques. Unmanaged or minimally managed natural landscapes favour viable grouse populations. Conservation of such landscapes is crucial - even if drained habitats are being restored, breeding success decreases and nest predation risk increases shortly after the restoration. Culling nest predator species would provide temporary relief, but this would only have a local short-term effect.
Viable forest grouse populations (capercaillie, black grouse and hazel grouse) indicate landscape integrity, and maintaining such landscapes also protects other species. In the Nordic and Baltic countries, natural forest-wetland landscapes have been transformed by extensive afforestation, thinning and drainage systems. During the recent decades, the named landscapes have been altered into patches of fragmented woodland with increasing nest predation risk in birds. Along with the changes, the populations of forest grouse in these landscapes have also declined. All three species prefer different habitats in the same landscape and are sensitive to predation and forest management. I investigated how to improve the species survival. For that, I evaluated which silvicultural practices increase nest predation, and in which habitats the species are most vulnerable to predation. Clearcuts and young stands have the lowest nest predation, but capercaillie and hazel grouse avoid these areas. Forest fragmentation by clearcuts can cause both birds and predators to concentrate into remained patches of middle-aged and old-growth forest, increasing thus predation risk. Drainage ditches do not have a direct impact on grouse, but each species prefers a different type of Histosols. Thus, the abundance of variuous Histosols requires undrained forest-wetland landscape. The most unsuitable habitat for grouse are small protected areas, surrounded by production forestry with various silvicultural techniques. Unmanaged or minimally managed natural landscapes favour viable grouse populations. Conservation of such landscapes is crucial - even if drained habitats are being restored, breeding success decreases and nest predation risk increases shortly after the restoration. Culling nest predator species would provide temporary relief, but this would only have a local short-term effect.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
forest birds, forest economics, human impact, grouse, nesting, depredations, bird protection