Differential demographic responses of sympatric Parids to vegetation management in boreal forest

• Large-scale removal of small-diameter trees (i.e. thinning from below) in boreal forest can diminish niche diversity for birds that rely on a well-developed understory for nesting and foraging. Yet, few studies have examined how reduced niche diversity in managed forests affects fitness measures in closely-related species and the ability of competing species to co-exist. We related forest thinning to population trends of the willow tit Poecile montana (declining) and its dominant competitor the crested tit Lophophanes cristatus (stable), and conducted a 3-year comparative study to determine how variation in understory spruce density differentially influences survival and reproduction in these species. In line with our prediction that crested tits would gain resource priority under conditions of reduced forest understory complexity, willow tits and their nestlings suffered a disproportionate decline in both nest and adult survival prospects relative to crested tits as understoiy spruce density declined. Willow tits also had increased numbers of tail feather fault bars with decreasing understory complexity, further supporting the idea that willow tits suffer from food shortage and increased predation risk in areas of reduced understory. The long-term population declines of willow tits in boreal forest appears linked to large scale harvest of small-diameter spruce trees that provide important understory vegetation. A patchy arrangement of different thinning treatments through 'Understory Retention Thinning' (URT) may provide a cost-effective way to restore long-term structural complexity and biodiversity in densely stocked conifer stands. (C) 2014 Elsevier B.V. All rights reserved.

Subject headings

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

NATURVETENSKAP  -- Biologi -- Etologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Behavioural Sciences Biology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Zoologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Zoology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Evolutionsbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Evolutionary Biology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Keyword

Commercial thinning

Vegetation management

Variable density thinning

Niche diversity

Social dominance

Parids

Publication and Content Type

ref (subject category)

art (subject category)