Erkki Korpimäki

University of Turku | UTU · Department of Biology

The hoarding behaviour of animals has evolved to reduce starvation risk when food resources are scarce, but effects of food limitation on survival of hoarding animals is poorly understood. Eurasian pygmy owls (Glaucidium passerinum) hoard small mammals and birds in natural cavities and nest boxes in late autumn for later use in the following winter...

The loss of habitat heterogeneity due to agricultural intensification has led to a global decline in farmland birds. Among them is the Eurasian Kestrel Falco tinnunculus , which occupies high trophic levels and may be adversely affected by reduced food quantity or quality and consequent health impacts. In this study, we investigate the effects of h...

Bird sex determination is fundamental in various ecological and biological studies, although many avian species cannot be sexed visually due to their monomorphic and/or monochromatic appearance. Thus, reliable laboratory methods for sexing are a prerequisite. Most avian nestlings lack sex-related signs, including the Eurasian pygmy owl (Glaucidium...

S1 File

Offspring survival rates in altricial birds during the post-fledging period are an essential factor in determining the fitness of parents and have a significant impact on general population dynamics. However, our current knowledge of post-fledging mortality and its causes remains fragmentary in most bird species, and even less information is availa...

Agricultural intensification and climate change are serious threats toward animal populations worldwide. Agricultural intensification reduces the heterogeneity of agricultural habitats by diminishing crop variation and destroying microhabitats, such as small woody features, whereas the effects of climate change range from the growing frequency of w...

A greater knowledge of the intrinsic and extrinsic factors of animal home range (HR) formation can help us to understand the fundamental biological issues underlying, for instance, movement patterns, habitat selection and survival. However, very little is known about the HRs of birds of prey fledglings, even though the post-fledging phase is recogn...

Background Owls have been reported as definitive hosts, whereas wild small mammals (naturally and experimentally) as intermediate hosts of several species of Sarcocystis. Recently, dead fledglings were found infected by an unnamed species of Sarcocystis since its intermediate host was unknown. After collecting additional samples of owls and wild sm...

Most studies on intraspecific competition, i.e., competition among individuals of the same species, have been conducted during the breeding season. Yet, at northern latitudes, intraspecific competition is expected to be particularly strong under the harsh weather conditions of the non-breeding season with limited number of resources available per i...

Climate change affects timing of reproduction in many bird species, but few studies have investigated its influence on annual reproductive output. Here, we assess changes in the annual production of young by female breeders in 201 populations of 104 bird species (N = 745,962 clutches) covering all continents between 1970 and 2019. Overall, average...

The knowledge about the mortality rate of offspring is crucial for estimating bird population dynamics and conserving species with declining populations. Parents of predatory birds provide food for their offspring during the post-fledging dependency period, which is frequently described as essential due to inexpert flying skills. Using radio teleme...

Understanding how interaction with conspecifics can impact predators’ spatial distribution is crucial to investigate predator effects at a landscape scale. We studied food hoarding and age- and sex-specific spatial settlement patterns of pygmy owls (Glaucidium passerinum), small avian predators storing prey for wintertime. When food resources are s...

Climate change is increasing the frequency of extreme events, such as droughts or hurricanes, with substantial impacts on human and wildlife communities. Extreme events can affect individuals through two pathways: by altering the fitness of adults encountering a current extreme, and by affecting the development of individuals born during a natal ex...

Social polygyny usually benefits males by increasing the number of offspring, whereas it is detrimental for females as they must share the resources provided by their mate. An intersexual conflict may exist in animals with obligatory bi-parental care, such as birds of prey, in which females incubate and brood, whereas males provision food for their...

Climate change is a pervasive threat to biodiversity. While range shifts are a known consequence of climate warming contributing to regional community change, less is known about how species’ positions shift within their climatic niches. Furthermore, whether the relative importance of different climatic variables prompting such shifts varies with c...

In vertebrates, thyroid hormones (THs) play an important role in the regulation of growth, development, metabolism, photoperiodic responses and migration. Maternally transferred THs are important for normal early phase embryonic development when embryos are not able to produce endogenous THs. Previous studies have shown that variation in maternal T...

Background: Birds act as intermediate or definitive hosts of cyst-forming coccidia parasites of the genus Sarcocystis Lankester, 1882. However, the spectrum of species of Sarcocystis in birds and the role of the latter in the transmission of coccidia are still incomplete for many avian species, including the Tengmalm's owl Aegolius funereus (Linnae...

Physical condition is important for the ability to resist various parasites and diseases as well as in escaping predators thus contributing to reproductive success, over-winter survival and possible declines in wildlife populations. However, in-depth research on trends in body condition is rare because decades-long datasets are not available for a...

The spectrum of species of Sarcocystis in birds and the role of the latter in the transmission of coccidia are still incomplete for many avian species including Tengmalm’s owl Aegolius funereus (Linnaeus, 1758). Therefore, this study is focused on the morphological and molecular description of a new Sarcocystis species found in the intestine of the...

Food-hoarding behaviour is widespread in the animal kingdom and enables predictable access to food resources in unpredictable environments. Within-species, consistent variation among individuals in food-hoarding behaviours may indicate the existence of individual strategies, as it likely captures intrinsic differences in how individuals cope with r...

Background Birds act as intermediate or definitive hosts of cyst-forming coccidia parasites of the genus Sarcocystis Lankester, 1882. However, the spectrum of species of Sarcocystis in birds and the role of the latter in the transmission of coccidia are still incomplete for many avian species including Tengmalm’s owl Aegolius funereus (Linnaeus, 17...

Tree cavities are an essential requirement for reproduction and survival of secondary cavity nesters. Little is known, however, about how cavity distribution in space and time may limit their use during and outside of the breeding season. Using long-term (17 yr) data on the use of nest-boxes resembling tree cavities by individually marked Eurasian...

The authors would like to correct errors in the original publication of the article.

Recent wildlife population declines are usually attributed to multiple sources such as global climate change and habitat loss and degradation inducing decreased food supply. However, interactive effects of fluctuations in abundance of main foods and weather conditions on population densities and reproductive success have been studied rarely. We ana...

This is a review of owl and raptor food studies in Finland mainly between 1828 and 1974 which was the period covered by a new book: Ornithology in Finland and written by Esa Lehikoinen, Risto Lemmetyinen, Timo Vuorisalo & Mia Rönkä. This book has an extensive list of references from page 491 to 546. In this chapter, raptors included also shrikes an...

Large brains in prey may select for adoption of anti-predator behavior that facilitates escape. Prey species with relatively large brains have been shown to be less likely to fall prey to predators. This results in the prediction that individuals that have been captured by predators on average should have smaller brains than sympatric conspecifics....

It is much debated whether the direct effects of weather or biotic interactions determine species’ responses to climate change. For example, an important biotic factor for herbivores in northern ecosystems is the availability of winter food. If the food availability changes because of the changing climate, it likely has major impact on the abundanc...

We studied the relationship between temperature and the coexistence of great tit Parus major and blue tit Cyanistes caeruleus, breeding in 75 study plots across Europe and North Africa. We expected an advance in laying date and a reduction in clutch size during warmer springs as a general response to climate warming and a delay in laying date and a...

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,...

Specialist individuals within animal populations have shown to be more efficient foragers and/or to have higher reproductive success than generalist individuals, but interspecific reproductive consequences of the degree of diet specialisation in vertebrate predators have remained unstudied. Eurasian pygmy owls (hereafter POs) have less vole‐special...

Results from a 47-year study of Tengmalm's Owls Aegolius funereus in western Finland show that abundance of their main prey (Microtus and Myodes voles), and the three-year, high-amplitude fluctuations in vole populations, is fundamentally important in regulating the owl populations. A strong positive relationship emerged between breeding densities...

Intraspecific competition, i.e. competition occurring between individuals of the same species, can affect the spatial distribution of a species and lead to costs in terms of a reduction in fitness. The amount of resources available for each individual will decrease with increasing population size, resulting in a more intense intraspecific competiti...

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 al...

Natural cavities are a critical resource for non-excavating hole-nesting birds, many of which are declining in northern Europe. In the heavily managed boreal forests in Finland, cavities may be a scarce resource, but their availability to different hole-nesters has been examined in only a few studies. We studied the abundance of suitable cavities i...

Climatic conditions, trophic links between species and dispersal may induce spatial synchrony in population fluctuations. Spatial synchrony increases the extinction risk of populations and, thus, it is important to understand how synchrony-inducing mechanisms affect populations already threatened by habitat loss and climate change. For many species...

Mothers may vary resource allocation to eggs and embryos, which may affect offspring fitness and prepare them to future environmental conditions. The effects of food availability and predation risk on reproduction have been extensively studied, yet their simultaneous impacts on reproductive investment and offspring early life conditions are still u...

Animals' life-history traits vary largely along many continuums across species and several physiological parameters have been proposed as possible mediators that drive the life-history variation, such as metabolic rates, glucocorticoids, and oxidative stress. Interestingly, thyroid hormones (THs), despite closely interacting with these physiologica...

Intraspecific competition, i.e. competition occurring between individuals of the same species, can affect the spatial distribution of a species and lead to costs in terms of a reduction in fitness. The amount of resources available for each individual will decrease with increasing population size, resulting in a more intense intraspecific competiti...

Background: Selecting high-quality habitat and the optimal time to reproduce can increase individual fitness and is a strong evolutionary factor shaping animal populations. However, few studies have investigated the interplay between land cover heterogeneity, limitation in food resources, individual quality and spatial variation in fitness paramet...

Seppo Sulkava, professor emeritus of zoology, passed away aged 87 in Espoo, Finland. He was born on 30th September 1931 at Ilmajoki, western Finland. He made an extensive career starting 1961 at a newly formed University of Oulu as a researcher, then as a curator of the Zoological Museum and since 1968 as a professor until retirement 1994, the last...

Hoarding behaviour (storing food for a later use) has evolved to reduce starvation risk when resources are scarce. Different age and sex classes often show differences in foraging due to experience, skills or life history strategy, but such differences in hoarding under spatio-temporally varying environmental conditions have rarely been studied in...

Natal dispersal, the one-way movement between birth site and first breeding site, is an important determinant of species gene-flow and invasion potential. While dispersing in unfamiliar habitat, individuals may adjust their movement based on possible costs and benefits of moving, termed context-dependent dispersal. The role of factors, such as popu...

Lethal interactions can shape ecosystem structure, and consequently understanding their causes is ecologically relevant. To improve both empirical and theoretical knowledge on superpredation (i.e. predation on high‐order predators), we studied an eagle owl population, including its main prey and mesopredators, and then we crossed these results with...

Habitat choice often entails trade-offs between food availability and predation risk. Understanding the distribution of individuals in space thus requires that both habitat characteristics and predation risk are considered simultaneously. Here, we studied the nest box use of two arboreal squirrels who share preferred habitat with their main predato...

Areas of different habitat types within small and large buffers around occupied and unoccupied squirrels nest boxes. (DOCX)

Yearly occupancy rates of flying and red squirrel nest boxes. (DOCX)

Alternative models. (DOCX)

Prolonged physiological stress response may lead to an excessive production of reactive oxygen species (ROS) and ultimately to oxidative stress and severe fitness costs. We investigated whether natural variation in predation risk, induced by pygmy owls (Glau-cidium passerinum), modifies the oxidative status of two free-living food-supplemented pass...

Browsing effects of voles on plants can be mitigated by means of non-lethal predation, i.e. by subjecting voles to predator cues. Earlier studies largely focused on mammalian olfactory cues, whereas here we exposed Microtus voles to owl calls to examine whether the introduced predation risk reduces browsing on tree seedlings (silver birch, Scots pi...

Competing species and predators can alter the habitat use of animals, but both factors are rarely simultaneously controlled. We studied in experimental enclosures how closely related species, the sibling vole (Microtus levis Miller, 1908) and the field vole (Microtus agrestis (Linnaeus, 1761)), adjust their habitat use when facing either the compet...

Hoarding behaviour evolved in few small species to reduce starvation risk, especially in response to harsh winter condition or food shortage. Some species of owls, such as Eurasian pygmy owls (Glaucidium passerinum), store prey in natural cavities or in nest-boxes. Despite storing habits of pygmy owls being already documented at the population leve...

Predator presence and shortage of food resources can alter behavior and cause chronic physiological stress, with long-term detrimental effects on the prey. Recently, it has been hypothesized that cellular damage via oxidative stress could be associated with such effects. Variation in food availability and predation risk could modify the oxidative/a...

Ilkka Hanski may be best known for his work on insect and metapopulation dynamics, but he also contributed significantly to small mammal research. In the early 1980s he became interested in shrew dynamics, energetics, and of course, shrew metapopulations. He aimed at understanding the population biological consequences of body size in different shr...

Oikos Finland 2017

The spatial distribution of predators is affected by intra- and interspecific interactions within the predator guild. Studying these interactions under fluctuating food availability, while taking habitat characteristics into account, offers a quasi-experimental set up to determine the relative impact of con- and heterospecifics on reproductive succ...

Previous studies on intraguild predation have mainly focused on within-class assemblages, even though avian top predators may also influence mammalian mesopredator prey. By using nation-wide long-term data from Finland, northern Europe, we examined the impacts of golden eagles (Aquila chrysaetos) together with red foxes (Vulpes vulpes) and pine mar...

Food availability and predation risk can have drastic impacts on animal behaviour and populations.The trade-off between foraging and predator avoidance is crucial for animal survival and will strongly affect individual body mass, since large fat reserves are beneficial to reduce starvation but may increase predation risk. Two-factor experiments, si...

Mothers may affect the future success of their offspring by varying allocation to eggs and embryos. Allocation may be adaptive based on the environmental conditions perceived during early breeding. We investigated the effects of food supplementation and predation risk on yolk hormone transfer in the pied flycatcher Ficedula hypoleuca. In a food sup...

We studied the responses of red squirrels, Sciurus vulgaris, to food supplementation and avian predation risk during two winters in Finland, when the level of natural food production, spruce seeds, varied markedly. We performed an open experiment with 6 replicates in the landscape where squirrel signs were counted near a feeding station and/or acti...

The increase in size of human populations in urban and agricultural areas has resulted in considerable habitat conversion globally. Such anthropogenic areas have specific environmental characteristics, which influence the physiology, life history, and population dynamics of plants and animals. For example, the date of bud burst is advanced in urban...

Figure S1. Intensity of urbanisation according to (A) classification by scientists. Box plots show medians, quartiles, 5‐ and 95‐percentiles, and extreme values, and (B) CORINE land cover code (red = discontinuous urban, purple = industrial or commercial units, pink = green urban sites, brown = arable land and rice field, orange = agriculture lands...

Figure S2. Distribution of study plots across Europe, North Africa and the Middle East.

Table S1. Summary data for study plots. See Material and methods for definitions. Table S2. Correlation matrix of explanatory variables. Table S3. Mixed linear model investigating laying date in four passerines species (CF: Collared Flycatcher, GT: Great tit and PF: Pied Flycatcher) as a function of habitat characteristics (intensity of urbanisat...

Figure S3. Box plots of latitude of study plots in four passerine birds in Europe, North Africa and the Middle East.

There is a pressing need to understand how changing climate interacts with land-use change to affect predator-prey interactions in fragmented landscapes. This is particularly true in boreal ecosystems facing fast climate change and intensification in forestry practices. Here, we investigated the relative influence of autumn climate and habitat qual...