Food Caches Research Articles

Climate-driven carry-over effects negatively influence population growth rate in a food-caching boreal passerine.

Understanding how events throughout the annual cycle are linked is important for predicting variation in individual fitness, but whether and how carry-over effects scale up to influence population dynamics is poorly understood. Using 38years of demographic data from Algonquin Provincial Park, Ontario, and a full annual cycle integrated population model, we examined the influence of environmental conditions and density on the population growth rate of Canada jays (Perisoreus canadensis), a resident boreal passerine that relies on perishable cached food for over-winter survival and late-winter breeding. Our results demonstrate that fall environmental variables, most notably the number of freeze-thaw events, carried over to influence late-winter fecundity, which, in turn, was the main vital rate driving population growth. These results are consistent with the hypothesis that warmer and more variable fall conditions accelerate the degradation of perishable stored food that is relied upon for successful reproduction. Future warming during the fall and winter may compromise the viability of cached food that requires consistent subzero temperatures for effective preservation, potentially exacerbating climate-driven carry-over effects that impact long-term population dynamics.

Interactions among Shade, Caching Behavior, and Predation Risk May Drive Seed Trait Evolution in Scatter-Hoarded Plants

Although dispersal is critical to plant life history, the relationships between seed traits and dispersal success in animal-dispersed plants remain unclear due to complex interactions among the effects of seed traits, habitat structure, and disperser behavior. We propose that in plants dispersed by scatter-hoarding granivores, seed trait evolution may have been driven by selective pressures that arise from interactions between seedling shade intolerance and predator-mediated caching behavior. Using an optimal foraging model that accounts for cache concealment, hoarder memory, and perceived predation risk, we show that hoarders can obtain cache-recovery advantages by placing caches in moderately risky locations that force potential pilferers to engage in high levels of vigilance. Our model also demonstrates that the level of risk needed to optimally protect a cache increases with the value of the cached food item. If hoarders perceive less sheltered, high-light conditions to be more risky and use this information to protect their caches, then shade-intolerant plants may increase their fitness by producing seeds with traits valued by hoarders. Consistent with this hypothesis, shade tolerance in scatter-hoarded tree species is inversely related to the value of their seeds as perceived by a scatter-hoarding rodent.

Food shopping under risk and uncertainty

During the 2020 Covid-19 pandemic panic buying of food was reported by the media. Panic buying has received little attention within behavioural science. In this paper we suggest that optimality models of foraging under risk and uncertainty would be a fruitful place to begin developing useful and testable hypotheses about this behaviour. In making this case we relate panic buying to a general increase in foraging effort, which we characterize as an increase in purchasing and spending. We note two risks during the pandemic – that of food security and that of predation, where predation is understood as a perceived threat to life due to infection risk. Food security was effectively solved early on in the pandemic, whilst perceived threat to life has remained but diminished to some limited extent. We relate panic buying to food caching as a method of buffering risk and make six predictions about how this behaviour should present under food insecurity and perceived threat to life.

Food caching behavior of the Eurasian beaver in northern Europe

Food storage (caching, hoarding), which is observed in many species of animals, increases food availability during times of food insecurity. Both species of beaver (Eurasian beaver, Castor fiber, and the North American beaver, C. canadensis) living at northern latitudes where food may be scarce during winter are larder‐hoarders, constructing a food cache of branches of woody species during autumn. We studied the food caching behavior of the Eurasian beaver in three northern European countries (Sweden, Norway, Lithuania) to provide additional insight into this important behavior. Thirty‐seven of forty‐seven (79%) active family groups had food caches by mid‐November and 41 of 47 (87%) had caches by December. Water depth of caches ranged from 1 to 2.3 m and depths at caches in Sweden were significantly deeper than in either Norway or Lithuania. Construction of caches began as early as late September (week 39/40) in Sweden and Lithuania and by mid‐October (week 42) in Norway. We observed plasticity in timing of cache initiation but the majority of active sites in all areas had food caches by the beginning of November (week 45). Declining air temperature and mean minimum temperatures of 0°C or below were associated with cache initiation. Caches in Lithuania were larger than in Sweden and Norway, which may be associated with colder winter temperatures. We did not find any relationship between family size or length of territory occupancy and cache size at our Norway sites where population demographics were available. Our results are generally consistent with other studies of food caching behavior in both species and suggest general similarities as well as behavioral plasticity in this important evolutionary strategy.

Accounting for unknown behaviors of free-living animals in accelerometer-based classification models: Demonstration on a wide-ranging mesopredator

Describing the behaviors of free-living animals is broadly useful for ecological and physiological research, but obtaining accurate records for difficult-to-observe species presents a considerable challenge. Tri-axial accelerometers are increasingly used for this purpose by exploiting behavioral observations from accelerometer-carrying animals to predict behaviors of unobserved conspecifics. We developed a modeling approach to predict behaviors of wolverines from collar-mounted accelerometers using Support Vector Machines. By applying a temporal smoothing function and setting a lower threshold for a-posteriori prediction probabilities, we improve the predictive performance of our model and simultaneously create a framework for explicitly accounting for behaviors unknown to the model, a problem that remains largely unaddressed in similar studies. We demonstrate that such an approach can achieve a model-averaged accuracy of 98.3%, with high predictive performance for the behaviors resting, running, scanning, tearing at food, and transferring items with the mouth, a behavior typically associated with caching food among captive wolverines. To illustrate the utility of this approach, we apply this model to a sample of seven free-living wolverines in Arctic Alaska.

Evolution of woodcutting behaviour in Early Pliocene beaver driven by consumption of woody plants

Modern beavers (Castor) are prolific ecosystem engineers and dramatically alter the landscape through tree harvesting and dam building. Little is known, however, about the evolutionary drivers of their woodcutting behaviour. Here we investigate if early woodcutting behaviour in Castoridae was driven by nutritional needs. We measured stable carbon and nitrogen isotopes (δ13C and δ15N) of coeval subfossil plants and beaver collagen (Dipoides sp.) from the Early Pliocene, High Arctic Beaver Pond fossil locality (Ellesmere Island), in order to reconstruct Dipoides sp. diet. Isotopic evidence indicates a diet of woody plants and freshwater macrophytes, supporting the hypothesis that this extinct semiaquatic beaver engaged in woodcutting behaviour for feeding purposes. In a phylogenetic context, the isotopic evidence implies that woodcutting and consumption of woody plants can be traced back to a small-bodied, semiaquatic Miocene castorid, suggesting that beavers have been consuming woody plants for over 20 million years. We propose that the behavioural complex (swimming, woodcutting, and consuming woody plants) preceded and facilitated the evolution of dam building. Dam building and food caching behaviours appear to be specializations for cold winter survival and may have evolved in response to late Neogene northern cooling.

Effects of site fidelity, group size and age on food-caching behaviour of common ravens, Corvus corax

The storage of food is widespread among mammals and birds and can be flexibly adjusted to various contexts such as competition, food availability or energetic demands. In bird species, nonbreeders often move through large areas whereby periods of long-term settlement can alternate with short-term visits. In food-caching species these differences in the degree of local settlement might change the benefits gained from storing food, and caching may only be advantageous during periods of prolonged settlement. We examined whether differences in local settlement influence food-caching behaviour of wild common ravens at a local anthropogenic food source with high interspecific and intraspecific competition. We found that individuals with a higher degree of site fidelity (i.e. prolonged periods of local settlement) engaged in food caching more than individuals with less site fidelity (i.e. short periods of local settlement); this effect was even stronger in the presence of potential predators representing a high-risk foraging situation. Further, juvenile ravens were less likely to cache than subadults and adults, and an increasing number of conspecifics present at the feeding site decreased the likelihood of caching. We found considerable individual variation in respect to the area used for caching. We suggest that individuals with higher site fidelity may gain more benefits from caching food and/or that they are more successful in obtaining food potentially due to more experience with the local foraging situation. Research is needed to examine the exact causes of the observed link between food-caching behaviour and the different degrees of site fidelity. Our findings show that differences in movement and settlement decisions can influence ecological aspects such as food acquisition and thus may have important consequences for individual fitness and population dynamics. • We studied how differences in site fidelity affect food-caching behaviour of ravens. • Individuals with a high site fidelity cached food more frequently. • This effect was even stronger in the presence of predators. • Young ravens cached food less often compared to older individuals. • Caching behaviour decreased with an increasing number of conspecifics.

Refrigeration or anti-theft? Food-caching behavior of wolverines (Gulo gulo) in Scandinavia

Food-caching animals can gain nutritional advantages by buffering seasonality in food availability, especially during times of scarcity. The wolverine (Gulo gulo) is a facultative predator that occupies environments of low productivity. As an adaptation to fluctuating food availability, wolverines cache perishable food in snow, boulders, and bogs for short- and long-term storage. We studied caching behavior of 38 GPS-collared wolverines in four study areas in Scandinavia. By investigating clusters of GPS locations, we identified a total of 303 food caches from 17 male and 21 female wolverines. Wolverines cached food all year around, from both scavenging and predation events, and spaced their caches widely within their home range. Wolverines cached food items on average 1.1 km from the food source and made between 1 and 6 caches per source. Wolverines cached closer to the source when scavenging carcasses killed by other large carnivores; this might be a strategy to optimize food gain when under pressure of interspecific competition. When caching, wolverines selected for steep and rugged terrain in unproductive habitat types or in forest, indicating a preference for less-exposed sites that can provide cold storage and/or protection against pilferage. The observed year-round investment in caching by wolverines underlines the importance of food predictability for survival and reproductive success in this species. Increasing temperatures as a consequence of climate change may provide new challenges for wolverines by negatively affecting the preservation of cached food and by increasing competition from pilferers that benefit from a warmer climate. It is however still not fully understood which consequences this may have for the demography and behavior of the wolverine.Significance statementFood caching is a behavioral strategy used by a wide range of animals to store food for future use. Choosing appropriate caching sites appears important for slowing down decomposition rates and minimizes competition. In this study, we demonstrate that the wolverine, an opportunistic predator and scavenger, utilizes available carrion to create caches all year around. By following wolverines with GPS collars, we registered that they carried food far away to cache it in secluded and cold places, which are often located on steep slopes or in forest. However, when scavenging other carnivores’ prey, they move food in shorter distances, possibly to be able to quickly return for more. The observed efficiency in wolverine caching behavior is likely vital for their survival and reproductive success in the harsh and highly seasonal environment in which they live.

Effects of habitat use on food acquisition and food caching during a nonbreeding season in a winter-breeding, food-storing passerine

ABSTRACT Capsule: Wintering male Bull-headed Shrikes Lanius buchepalus preferred vegetable fields with perch sites to search for and detect terrestrial prey, and males occupying territories with large areas of vegetable fields acquired more prey and cached more food. Aims: To better understand effects of habitat use on food acquisition and food caching of the Bull-headed Shrike, we investigated relationships between habitat quality (measured through foraging-site selection and foraging success) and food caching during the non-breeding season. Methods: We monitored 66 territorial male shrikes during the non-breeding season from 2014 to 2016, and collected data on foraging-site selection, foraging success, and food caching. Results: Our field observations showed that male shrikes preferred to forage over vegetable fields and that males occupying territories incorporating large areas of that habitat were able to acquire more food items and store more food caches in their territories during the nonbreeding season. Conclusion: We suggest that for male Bull-headed Shrikes, a winter-breeding food-storing passerine, the quality of habitat in the nonbreeding season has the potential to affect their subsequent fitness.

Investigating information seeking in ravens (Corvus corax)

Measuring the responses of non-human animals to situations of uncertainty is thought to shed light on an animal’s metacognitive processes; namely, whether they monitor their own knowledge states. For example, when presented with a foraging task, great apes and macaques selectively seek information about the location of a food item when they have not seen where it was hidden, compared to when they have. We presented this same information seeking task to ravens, in which a food item was hidden in one of three containers, and subjects could either watch where the food was hidden, infer its location through visual or auditory clues, or were given no information. We found that unlike several ape species and macaques, but similar to capuchin monkeys, the ravens looked inside at least one tube on every trial, but typically only once, inside the baited tube, when they had either witnessed it being baited or could visually infer the reward’s location. In contrast, subjects looked more often within trials in which they had not witnessed the baiting or were provided with auditory cues about the reward’s location. Several potential explanations for these ceiling levels of looking are discussed, including how it may relate to the uncertainty faced by ravens when retrieving food caches.

Elevation-related differences in annual survival of adult food-caching mountain chickadees are consistent with natural selection on spatial cognition

Animals inhabiting montane gradients experience varying winter climates that may result in differential selection on survival-related traits. Higher elevations in temperate climates are characterized by harsher winters with greater and longer-lasting snow cover compared to lower elevations, potentially leading to stronger selection for traits that improve fitness under these harsher conditions. For food-caching mountain chickadees, Poecile gambeli, inhabiting harsh high elevation environments, individual variation in spatial cognitive abilities related to cache retrieval is associated with significant differences in overwinter survival. Compared to lower elevations, stronger predicted selection on traits needed for overwinter survival at higher elevations can be expected to result in higher adult annual survival despite harsher environmental conditions, indicating that individuals that survive their first winter are better suited to survive similar subsequent selection events. Here, we used a Bayesian hierarchical Cormack-Jolly-Seber (CJS) model to estimate and compare survival of adult mountain chickadees at higher and lower elevations over 3 years. We showed that adult survival was consistently higher at higher elevations despite much harsher environmental conditions, supporting our hypothesis that selection on overwinter survival-related traits (such as spatial cognition) is stronger at our high elevation study area than at lower elevations. Understanding how environmental conditions are associated with different selection strengths on survival-related traits is an important question in behavioral ecology. Directly estimating differences in strength of selection is daunting, but comparing survival between environments may provide an alternative method. We tested for differences in adult survival in a resident food-caching species at higher and lower elevations varying in winter climate severity. These birds rely on food caches for winter survival, and juvenile birds with better spatial cognition (needed for cache retrieval) have higher survival during their first year at higher harsher elevations. Here, we report higher adult survival at higher elevations compared to lower elevations, despite much harsher winter environment. Such findings support our hypothesis for stronger selection in harsher winter conditions because individuals that survive their first year under stronger selection are better suited to survive subsequent selection events.

The ecological and behavioral significance of short-term food caching in polar bears (Ursus maritimus)

The paucity of observations of wild polar bears (Ursus maritimus) caching of food (including hoarding, i.e., burying and remaining with a kill for up to a few days) has led to the conclusion that such behavior does not occur or is negligible in this species. We document 19 observations of short-term hoarding by polar bears between 1973 and 2018 in Svalbard, Greenland, and Canada. Short-term hoarding appears to be influenced by size of the kill and its remaining energetic value after the first meal has been consumed. Fat and meat from smaller seals, such as pup or yearling ringed seals (Pusa hispida), are largely devoured immediately, leaving little to hoard. Carcasses of adult ringed seals, harp seals (Pagophilus groenlandicus), and bearded seals (Erignathus barbatus) may be covered with snow to reduce the chance of kleptoparasitism by another bear or other scavengers visually detecting a dark spot on the ice, while the hoarding bear lies nearby. Hoarding of other species, such as beluga (Delphinapterus leucas) (calves or parts) or other polar bears, appears opportunistic. We review differences in caching, including short-term hoarding behavior between polar bears and brown bears (U. arctos), and hypothesize about factors that may have influenced their evolution.

Movement Patterns of the Eastern Chipmunk (<i>Tamias striatus</i>) in Four Fragmented Landscapes of Prince Edward Island, Canada

The analysis of animal movement patterns can provide important information on animals’ responses to habitat features. In this study, the movement paths of eastern chipmunks (Tamias striatus) were examined in four landscapes, with different levels of habitat fragmentation, using either fluorescent powdering or spool-and-line tracking. Descriptions of the tree and ground vegetation communities were performed in the vicinity of the trail to obtain information on habitat use and habitat selection. Several key movement variables were calculated, including the total path length, net distance, fractal dimension, and radius of gyration. Despite statistically significant differences in some of the movement metrics between the four landscapes, the overall movement patterns were generically the same for all of chipmunk paths examined in this study. The data were compared to trends expected based on random or correlated random walks, as well as Lévy-walk models. The mean squared net displacement did not support the correlated random walk predictions, except at smaller spatial scales, but overall demonstrated Lévy-like super diffusive behaviour. Lévy-like patterns were also confirmed from the move-length distributions that demonstrated truncated-tail power-law behaviour. Although this would suggest invariance of the movement patterns at all spatial scales studied, fractal analysis revealed at least two transitions in movement patterns at scales of around 2 and 5 m. The transition point at 2 m was negatively correlated with the density of small trees, while the transition at ~5 m was positively correlated with the spatial distribution of large trees. As the habitat-preference data showed that small trees are among the least preferred habitat component, while large trees were among the most preferred habitat, chipmunks are likely to alter their movement behaviour to avoid small trees, and attracted towards large trees possibly to avoid predators. Overall, we determined three principal domains of movement: at smaller spatio-temporal scales, foraging activities dominate and the movement is highly correlated but also random; at intermediate spatial scales, chipmunks may be moving to avoid predators, using different environmental cues, and the movement is more directed (but still influenced by vegetation patterns at intermediate scales); at larger spatio-temporal scales, the movement is dominated by long-range/long-term memory and homing to burrows and other key habitat features, such as food caches, drives more directed movement. The fact that scale-dependent movement mechanisms could give rise to LW patterns is consistent with recent studies.

Raising young with limited resources: supplementation improves body condition and advances fledging of Canada Jays.

Food availability early in life can play a vital role in an individual's development and success, but experimental evidence for the direct effects of food on body condition, physiology, and survival of young animals in the wild is still relatively scarce. Food-caching Canada Jays (Perisoreus canadensis) begin breeding in the late winter and, therefore, rely on either cached food or seemingly limited quantities of fresh food to feed nestlings in the early spring. Using a 2-yr food supplementation experiment conducted during the nestling period and 40yr of observational data on food supplemented by the public, we examined whether food quantity during early life influenced the physiology, body condition, timing of fledging, and survival of young Canada Jays in Algonquin Provincial Park, Ontario, Canada. Experimental food supplementation of breeding pairs advanced the fledging date of young by 24% (5.5 d) compared to controls. In 1yr of the experiment, nestlings raised on experimentally supplemented territories had lower feather corticosterone concentrations and were in higher body condition than controls. Across treatment and control nests, young that successfully fledged had lower concentrations of feather corticosterone and were in higher body condition than those that did not fledge. Based on 40yr of observational data, nestling body condition was positively related to the degree of food supplementation by park visitors and nestlings in higher body condition were more likely to be observed in the population in the following fall. Our results demonstrate how food availability early in life can have important downstream consequences on metrics related to individual fitness, including first year survival.

Elevation-related differences in the age structure of breeding birds suggest stronger selection at harsher elevations

How environmental variation affects the strength of selection is important for understanding phenotypic variation within a population. An indirect method to evaluate differences in selection pressures is to compare the age composition of a breeding population. A larger adult/first-year breeding ratio, due to higher juvenile mortality, may indicate stronger selection. We investigated the adult/first-year breeding ratios of food-caching mountain chickadees inhabiting different elevations. Chickadees at high elevations experience harsher winter conditions and cache more food items and have better spatial cognition to recover caches compared with their low-elevation counterparts. Cache recovery and spatial cognition are critical for overwinter survival and individuals with better spatial cognitive abilities are more likely to survive their first winter; therefore, these differences are likely a result of stronger selection pressures on spatial cognition and caching behavior at higher elevations. In support of this hypothesis, we found a significantly larger adult/first-year breeding ratio at high elevations compared with low elevations. This may suggest higher overwinter juvenile mortality and hence stronger selection pressures on survival-related traits at high elevations, consistent with elevation-related phenotypic differences. The strength of selection on survival-related traits varies across heterogenous environments. One way to assess the strength of selection is to measure the traits of individuals that are able to survive a particular selection event. Here we assessed the adult/first-year breeding ratios of resident, food-caching birds experiencing differentially harsh winter climates. These birds rely on spatial cognition to retrieve food caches and survive the winter; the largest annual selection event. At the individual level, those with better cognitive ability have demonstrated higher overwinter survival. However, at the population level, it remains unclear whether or not the strength of selection differs between harsh and mild winter climates. By assessing the age of breeders, we found a significantly larger adult/first-year breeding ratio in birds inhabiting harsher, high elevations compared with milder, low elevations. This suggests higher overwinter juvenile mortality and hence stronger selection pressures on survival-related traits at high elevations.

Neuronal Correlates of Spatial Working Memory in the Endbrain of Crows

Birds are renowned for their excellent spatial cognition. Corvid songbirds, in particular, rely on explicit representation of spatial cues in memory when caching food and retrieving caches for later consumption. However, the neuronal correlates of flexible spatial memory abilities are largely unknown in birds. We therefore trained carrion crows (Corvus corone) on a spatial delayed-response task in which they had to maintain the variable location of a visual item for a few seconds in working memory. After the crows performed this task with high precision, we recorded single-cell activity from the associative endbrain area Nidopallium caudolaterale (NCL) in the behaving crows. A large fraction of NCL neurons were tuned to individual preferred locations and selectively maintained the spatial location of items in working memory. A comparison of firing rates with reaction times suggested that the majority of delay-selective neurons represented stored location information rather than motor preparation. Almost 30% of all recorded neurons were tuned during both visual presentation and memory delay, and their spatial tuning was significantly correlated. The population of recorded neurons stably maintained spatial information over the course of the working memory period. Importantly, the neural responses of spatially tuned neurons were relevant for the crows' choices and allowed a statistical classifier to predict the subsequently chosen target location in free-choice trials. Our findings demonstrate the pivotal role of the avian NCL in spatial working memory that is reminiscent of the function of the convergently evolved primate prefrontal cortex in spatial working memory.

Spontaneous use and modification of a feather as a tool in a captive common raven

AbstractHere, we report an observation of a zoo‐housed common raven (Corvus corax) modifying and using a raven feather as a tool to access the food cache of her partner. We believe this record is of importance, as it represents one of the first cases of untrained common ravens spontaneously using and modifying a tool, and a rare example of a non‐human animal manufacturing a tool from a body part. This anecdotal observation suggests that tool use and tool modification may be present in the common raven behavioral repertoire in the foraging context; nevertheless, further investigations are needed to assess this possibility in more controlled settings as well as in the wild.

Food caching in city birds: urbanization and exploration do not predict spatial memory in scatter hoarders.

Urbanization has been shown to affect the physiological, morphological, and behavioral traits of animals, but it is less clear how cognitive traits are affected. Urban habitats contain artificial food sources, such as bird feeders that are known to impact foraging behaviors. As of yet, however, it is not well known whether urbanization and the abundance of supplemental food during the winter affect caching behaviors and spatial memory in scatter hoarders. We aim to compare caching intensity and spatial memory performance along an urban gradient to determine (i) whether individuals from more urbanized sites cache less frequently and perform less accurately on a spatial memory task, and (ii) for the first time in individual scatter hoarders, whether slower explorers perform more accurately than faster explorers on a spatial memory task. We assessed food caching, exploration of a novel environment, and spatial memory performance of wild-caught black-capped chickadees (Poecile atricapillus; N = 95) from 14 sites along an urban gradient. Although the individuals that cached most in captivity were all from less urbanized sites, we found no clear evidence that caching intensity and spatial memory accuracy differed along an urban gradient. At the individual level, we found no significant relationship between spatial memory performance and exploration score. However, individuals that performed more accurately on the spatial task also tended to cache more, pointing to a specialization of spatial memory in scatter hoarders that could occur at the level of the individual, in addition to the previously documented specialization at the population and species levels.

Food caching by a marine apex predator, the leopard seal (Hydrurga leptonyx)

The foraging behaviors of apex predators can fundamentally alter ecosystems through cascading predator–prey interactions. Food caching is a widely studied, taxonomically diverse behavior that can modify competitive relationships and affect population viability. We address predictions that food caching would not be observed in the marine environment by summarizing recent caching reports from two marine mammal and one marine reptile species. We also provide multiple caching observations from disparate locations for a fourth marine predator, the leopard seal (Hydrurga leptonyx (de Blainville, 1820)). Drawing from consistent patterns in the terrestrial literature, we suggest the unusual diversity of caching strategies observed in leopard seals is due to high variability in their polar marine habitat. We hypothesize that caching is present across the spectrum of leopard seal social dominance; however, prevalence is likely to increase in smaller, less-dominant animals that hoard to gain competitive advantage. Given the importance of this behavior, we draw attention to the high probability of observing food caching behavior in other marine species.

Using nest-boxes in pine stands of the Augustów Forest

Abstract In 2011–2014, the occupancy of nest-boxes by secondary hole-nesting birds and their breeding success was investigated in pine stands of the Augustów Forest (North-Eastern Poland). In the studied area of 12600 ha, the share of Scots Pine Pinus sylvestris L. in the stands was 92%. On average, birds occupied 54% and bats 3% of the 224–317 nest boxes controlled yearly. Nest boxes were also used by the Pygmy Owl Glaucidium passerinum L. as food caches. In total, broods of nine secondary hole-nesting species were observed, but only four bird species nested in each year of study. The most numerous species, occupying 53–60% of all boxes each year was the Pied Flycatcher Ficedula hypoleuca Pall. The Great Tit Parus major L. occupied 15–24% and the Coal Tit Periparus ater L. 10–12% of available nest-boxes, while the Redstart Phoenicurus phoenicurus L. used 2–7% of nest boxes. The yearly breeding success was highest for tits (Great Tit – 52–84%, Coal Tit – 50–72%) and strongly variable for the Pied Flycatchers – 38–78%. Broods were lost due to predation by martens Martes sp. (38%) and great spotted woodpeckers Dendrocopos major L. (6%) as well as nest competition (2%). The nest-boxes were occupied at a constant rate during the following four years after their exposition. Over 67% of the new nest-boxes were occupied annually which means new nest-boxes (up to 4 years) were occupied significantly more often than boxes older than 4 years.