Tree cavity abundance and beyond: Nesting and food storing sites of the pygmy owl in managed boreal forests

Baroni, Daniele; Korpimäki, Erkki; Selonen, Vesa; Laaksonen, Toni

doi:10.1016/j.foreco.2019.117818

Cited by 23 publications

(14 citation statements)

References 71 publications

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“…Aspen trees are inhabited by epiphytic bryophytes and lichens (Kuusinen, 1994;Gustafsson and Eriksson, 1995;Hazell, 1998;Pykälä et al, 2006), pathogens (Callan, 1998), herbivorous invertebrates (Robinson et al, 2012), mammals such as the flying squirrel (Pteromys volans; Hanski, 1998;Remm et al 2017) and birds such as woodpeckers and owls (Hågvar et al, 1990;Angelstam and Mikusinski, 1994;Tikkanen et al, 2006;Hardenbol et al 2019). Secondary hole-nesters, including many tits, flycatchers, owls, ducks and flying squirrels, are dependent on cavities excavated by woodpeckers (Martin and Eadie, 1999;Baroni et al 2020). Aspen leaf litter is utilised by, for example, gastropods (Suominen et al, 2003), and dead and decaying aspen trunks provide a suitable habitat for myriad 4 polypore fungi (Kotiranta and Niemelä, 1981;Hynynen and Viherä-Aarnio, 1999;Junninen et al, 2007) and saproxylic invertebrate species (Siitonen and Martikainen, 1994;Martikainen, 2001;Dahlberg and Stokland, 2004;Halme et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

A keystone species, European aspen (Populus tremula L.), in boreal forests: Ecological role, knowledge needs and mapping using remote sensing

Kivinen

Koivisto

Keski‐Saari

et al. 2020

Forest Ecology and Management

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Section: Introductionmentioning

confidence: 99%

A keystone species, European aspen (Populus tremula L.), in boreal forests: Ecological role, knowledge needs and mapping using remote sensing

Kivinen

Koivisto

Keski‐Saari

et al. 2020

Forest Ecology and Management

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“…Quantifying the total response of pygmy owls is a challenging task because of a lack of data on the real numbers of prey species available in the field on one hand and incomplete information on the amount of food stored in undiscovered stores in natural tree cavities on the other. In our study area, natural cavities in trees were only very seldom used as food stores (Baroni et al 2020). The obtained result is thus an approximation of the real consumption by pygmy owls on these species, but we consider that it anyway reflects interspecific differences between prey species and its among-year variation in relation to the vole abundance.…”

Section: Total Response Of Pygmy Owlsmentioning

confidence: 83%

Age and sex differences in numerical responses, dietary shifts, and total responses of a generalist predator to population dynamics of main prey

et al. 2020

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Fluctuations in the abundance of main prey species might shape animal communities, by inducing numerical responses and dietary shifts in predators. Whether numerical responses and dietary shifts differ among individuals of different age and sex has so far gained little attention. These differences could affect how much predators consume main and alternative prey, thus causing variation in predation pressure on main and alternative prey species. We studied the effect of fluctuating main prey abundance (voles) in autumn on the age and sex composition of a food-hoarding population of Eurasian pygmy owls Glaucidium passerinum (327 individuals), and on the species composition of their food stores in western Finland during 2003-2017 (629 food stores). Numbers of yearlings (< 1-year old) of both sexes and adult (+ 1-year old) females increased with increasing vole abundance. During low vole abundance, adult owls stored more small birds and less small mammals than yearlings. Females stored more small mammals than males and showed a tendency to store less birds. The amount of consumed birds (the most important alternative prey), and in particular of crested, willow, great, and blue tits, increased with low vole densities. Our results show that numerical, functional, and total responses of pygmy owls, and probably also other vertebrate predators, to the availability of the main prey in winter are shaped by the age and sex composition of the predator population, which both show large spatio-temporal variation in boreal forests.

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“…The use of partially rotten prey items by owls has been shown before (Roulin, 2004), but we are not aware of any previous study on the possible detrimental effects that eating rotten food could have on avian and mammalian predators. Pygmy owls have been shown to clean old nest material from the boxes before the breeding season (Baroni, Korpimäki, Selonen, & Laaksonen, 2020). It is therefore possible that rotten prey items are not consumed but thrown away, but this was never observed during inspection of food hoards in early spring in the surroundings of the hoard.…”

Section: Discussionmentioning

confidence: 99%

Climate change and perishable food hoards of an avian predator: Is the freezer still working?

Masoero

Laaksonen

Morosinotto

et al. 2020

Global Change Biology

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Changing climate can modify predator–prey interactions and induce declines or local extinctions of species due to reductions in food availability. Species hoarding perishable food for overwinter survival, like predators, are predicted to be particularly susceptible to increasing temperatures. We analysed the influence of autumn and winter weather, and abundance of main prey (voles), on the food‐hoarding behaviour of a generalist predator, the Eurasian pygmy owl (Glaucidium passerinum), across 16 years in Finland. Fewer freeze–thaw events in early autumn delayed the initiation of food hoarding. Pygmy owls consumed more hoarded food with more frequent freeze–thaw events and deeper snow cover in autumn and in winter, and lower precipitation in winter. In autumn, the rotting of food hoards increased with precipitation. Hoards already present in early autumn were much more likely to rot than the ones initiated in late autumn. Rotten food hoards were used more in years of low food abundance than in years of high food abundance. Having rotten food hoards in autumn resulted in a lower future recapture probability of female owls. These results indicate that pygmy owls might be partly able to adapt to climate change by delaying food hoarding, but changes in the snow cover, precipitation and frequency of freeze–thaw events might impair their foraging and ultimately decrease local overwinter survival. Long‐term trends and future predictions, therefore, suggest that impacts of climate change on wintering food‐hoarding species could be substantial, because their ‘freezers’ may no longer work properly. Altered usability and poorer quality of hoarded food may further modify the foraging needs of food‐hoarding predators and thus their overall predation pressure on prey species. This raises concerns about the impacts of climate change on boreal food webs, in which ecological interactions have evolved under cold winter conditions.

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Tree cavity abundance and beyond: Nesting and food storing sites of the pygmy owl in managed boreal forests

Cited by 23 publications

References 71 publications

A keystone species, European aspen (Populus tremula L.), in boreal forests: Ecological role, knowledge needs and mapping using remote sensing

A keystone species, European aspen (Populus tremula L.), in boreal forests: Ecological role, knowledge needs and mapping using remote sensing

Age and sex differences in numerical responses, dietary shifts, and total responses of a generalist predator to population dynamics of main prey

Climate change and perishable food hoards of an avian predator: Is the freezer still working?

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