Nest-site Preferences Research Articles

Nest Sites of Middle Spotted WoodpeckersLeiopicus mediusin a Primeval Forest

Forest management usually reduces the diversity and amount of substrates in which woodpeckers can excavate holes. In such conditions the recorded patterns of nest site selection could reflect a more reduced array of substrates than the species' nest site preferences. We analysed new data on nest sites of Middle Spotted Woodpeckers Leiopicus medius collected during 27 breeding seasons (1987–2013) in the strictly protected fragments of the Bialowieza National Park in Poland. The birds could use diverse excavation substrates, of various statures, that varied in condition from living and healthy to dead and completely rotten. Middle Spotted Woodpeckers used a wide array of tree species, with little overlap in the species used in the riverine habitat (mostly Alnus glutinosa, and Fraxinus excelsior) and oak—hornbeam habitats (Carpinus betulus and Quercus robur). The birds preferred to excavate in Q. robur but avoided Tilia cordata and Picea abies. They placed holes in large trees (median girth at breast height:...

Queen location and nest site preference influence colony reunification by the ant Temnothorax rugatulus

Social insect colonies adeptly make consensus decisions that emerge from distributed interactions among colony members. How consensus is accomplished when a split decision requires resolution is poorly understood. We studied colony reunification during emigrations of the crevice-dwelling ant Temnothorax rugatulus. Colonies can choose the most preferred of several alternative nest cavities, but the colony sometimes initially splits between sites and achieves consensus later via secondary emigrations. We explored the decision rules that govern reunification using artificially split colonies. When monogynous colonies were evenly divided between identical sites, the location of the queen played a decisive role, with 14 of the 16 colonies reuniting at the site that held the queen. This suggests a group-level strategy for minimizing risk to the queen by avoiding unnecessary moves. When the queen was placed in the less preferred of two sites, all 14 colonies that reunited did so at the preferred nest, despite having to move the queen. These results show that colonies balance multiple factors when reaching consensus, and that preferences for physical features of the environment can outweigh the queen’s influence.

Evaluation of nest site preferences of a nest dismantler, the Hair-crested Drongo (Dicrurus hottentottus) in Dongzhai National Nature Reserve of central China

The Hair-crested Drongo (Dicrurus hottentottus) exhibits a unique nest-dismantling behavior after the fledging of the young. One hypothesis explaining this behavior is dismantling one’s own nest may reduce potential competition for nest sites in the following breeding season because suitable breeding habitat might be limited, and sites are often reused. By comparing the habitat features at nest and random locations, we determined the nest habitat preference of the Hair-crested Drongo within Dongzhai National Nature Reserve, Henan, China. We also compared habitat features with nesting success to determine if any trends could be detected. We found that nest tree height, diameter at breast height, live crown ratio, tree rank, and presence of overstory were significantly higher at nesting locations than random locations; slope, leaf litter cover percentage and depth, presence of understory and midstory, and number of trees per hectare were significantly lower at nest sites than random sites. Drongos preferred to use some tree species, such as Metasequoia glyptostroboides, Castanea mollissima, and Pterocarya stenoptera for nesting. Failed nests were often associated with habitat with higher percentage of leaf litter on the ground. Our data support that selection of nest sites does occur for this species at this site and therefore support the hypothesis that breeding habitat limitation could be one of the driving forces for the development of the nest-dismantling behavior in this species.

Drivers of decline and changed nest-site preference of the Baltic eider: an island-level analysis from south-western Finland

The recent large-scale decline of Eiders (Somateria mollissima) in the Baltic Sea is well documented by long-term population monitoring. One hypothesis to explain the decline is increased predation pressure during breeding, but because the decline has been steep and geographically broad, multiple drivers may be involved. Here we explore whether some of these hitherto unidentified drivers relate to the breeding habitat. To this end, we performed an analysis of long-termmonitoring data from ca. 300 islands from the Archipelago Sea, SW Finland, representing five geographical sub-areas, during 1993–2012. We analysed population trends and whether nest-site preference changed over time. The results showed steep population declines in the sub-areas farthest from themainland and a more moderate decline in the sub-area closest to the mainland. The presence of breeding gulls (Larus spp.) on the Eider breeding island had a consistently positive effect on Eider breeding numbers throughout the study period. In contrast, the presence of breeding White-tailed Sea Eagles (Haliaeetus albicilla) had a negative effect on breeding numbers, but only during the early study period when the Eagle breeding populationwas still small. Interestingly, the sign of the effect of the distance from the nearest neighbouring island on Eider breeding numbers changed over time. Eider breeding numbers positively correlated with island size and distance to neighbouring islands in the early period, whereas exposed large islands with islands nearby were positively associated with Eider breeding abundance during the late period. Future conservation efforts should shift from site-specific conservation to population-specific management due to the shift in nest-site preference. Furthermore, the positive influence of gulls warrants the adoption of conservation measures taking interspecific interactions into consideration.

A self-organising network model of decision making by the honey bee swarm

Purpose– The purpose of this paper is to carry out a detailed investigation of the mechanisms operating during decision making by the honey bee swarm, which is now considered to be one of the best examples of collective decision making outside the human domain.Design/methodology/approach– This investigation is based on a review of the last 60 years’ published literature about swarm behaviour. It introduces a different perspective to the work by utilising a cybernetic model of a self-organising information network to analyse the findings of this body of research.Findings– Scout bees evaluating potential nest sites accumulated support for their site by differential net recruitment, so the total scout numbers present at each site was a good measure of the total evidence in favour of the site and hence the relative probability of choosing it as the swarm’s new home. The accumulation of evidence continued at a number of alternative nest site locations until a critical quorum threshold was sensed at one of them. The first alternative to reach the threshold was chosen as the preferred nest site. Quorum scouts then prepared the swarm for departure and steered it to its new home.Originality/value– Swarm decision making has not been modelled as a self-organising information network before. This novel approach reveals how a combination of network modifications, self-amplification, self-attenuation, cross-inhibition, integration and quorum mechanisms together contribute towards accurate group decision making.

Breeding success of the Great Tit Parus major in relation to attributes of natural nest cavities in a primeval forest

An overlap in attributes of nest cavities used by Great Tit Parus major across Eurasia suggests similar nest site preferences within the geographical range, although the drivers of these preferences are unclear. To determine whether preferred cavities provide conditions enhancing successful reproduction, we investigated the breeding performance of Great Tits in relation to tree cavity characteristics using data collected during 2008–2011 in primeval conditions (Bialowieza National Park, Poland). Here, tree cavities are diverse and superabundant but nesting birds are at risk from a variety of predators. According to expectations, nest losses were high (60 % of Great Tit nests failed), mostly due to predation (69 % of nest failures). The risk of nest failure varied with nest cavity attributes. Compared to successful nests, failures were situated higher above the ground and placed closer to the cavity entrance. Very deep cavities with narrow entrances and strong livings walls provided effective protection against larger predators (e.g., martens, woodpeckers), unable to enter the cavity or pull out the contents. Yet, such holes were no barrier for the smallest predators (e.g., Forest Dormouse Dryomys nitedula), which were able to enter any Great Tit nest cavity and destroyed most of the nests. Avoiding small predators would give a selective advantage to the birds, but this seems hardly possible to achieve. We conclude that tree cavities preferred by the tits show a combination of properties which are a compromise for avoiding predation (the strongest selective pressure) and providing the minimum requirements (sufficient nest illumination, microclimate, protection against nest soaking) for development and growth of young.

Climate change implications for the nest site selection process and subsequent hatching success of a green turtle population

Sandy beach habitat where sea turtles nest will be affected by multiple climate change impacts. Before these impacts occur, knowledge of how nest site selection and hatching success vary with beach microhabitats is needed to inform managers on how to protect suitable habitats and prepare for scientifically valid mitigation measures at beaches around the world. At a highly successful green turtle (Chelonia mydas) rookery at Akumal, Quintana Roo, Mexico, we measured microhabitat characteristics along the beach crawl (rejected sites) and related nest site conditions (selected sites) to subsequent hatching success rates for 64 nesting events. To our knowledge, this is the first study to report environmental data along the nesting crawl for a green turtle population and the first to use natural breaks in the data to describe their preferred habitat ranges. Our results indicate that turtles were likely using a combination of cues to find nest sites, mainly higher elevations and lower sand surface temperatures (Kruskal-Wallis test, H = 19.84, p < 0.001; H = 10.78, p < 0.001). Hatching success was significantly and negatively correlated to sand temperature at cloaca depth (Spearman’s ρ = −0.27, p = 0.04). Indeed, the preferred range for cloaca sand temperatures at the nest site (26.3–27.5 °C) had significantly higher hatching success rates compared to the highest temperature range (Tukey HSD = 0.47, p = 0.05). Sand temperatures at various depths were intercorrelated, and surface and cloaca depth sand temperatures were correlated to air temperature (ρ = 0.70, p = 0.00; ρ = 0.26, p = 0.04). Therefore, rising air temperatures could alter sand temperature cues for suitable nest sites, preferred nest site ranges, and produce uneven sex ratios or lethal incubating temperatures. Elevation cues and preferred ranges (1.4–2.5 m) may also be affected by sea level rise, risking inundation of nests.

Habitat and nest site preferences of Red-backed Shrike (Lanius collurio) in western Denmark

In this study we evaluate nest site and habitat preferences of Red-backed Shrike (Lanius collurio) in the national park Mols Bjerge, Denmark. In total, 28 nests were found during 2010 and 2011. To determine nesting site preferences, the species composition of vegetation in scrub used for nesting was compared to that of nearest unused scrub. To evaluate habitat preferences, a Resource Selection Probability Function (RSPF) was modelled based on presence/absence data. The habitat factors were represented by Light Detection And Ranging (LIDAR) derived measures of vegetation height and topographic wetness as well as distance to nearest road/path, as an indicator of human disturbance. Scrub used as nesting sites were characterized by thorny shrub species such as Prunus spinosa and Rubus fruticosus. RSPF showed that shrike presence was positively correlated with vegetation heterogeneity and high topographic wetness, and that it was unaffected by the distance to the nearest road/path. These results provide some guidelines for management, showing that Red-backed Shrike for nesting preferred habitats with high wetness, possibly linked to food availability, and heterogeneous vegetation, consistent with their need for low vegetation for hunting and higher vegetation for hunting perches and nest sites, with thorny shrubs especially important for the latter.

Nest site characteristics and nest loss of Marsh Grassbird at Zhalong National Nature Reserve, China

The Marsh Grassbird Locustella pryeri is an uncommon songbird endemic to East Asia. Suitable nest- site selection can minimize nest loss, especially for open- cup and ground nesting passerines. We located and mon- itored 66 Marsh Grassbird nests during 2004-2006 in Zhalong National Nature Reserve, northeast China, to identify characteristics of preferred nest sites. Marsh Grassbird nested mainly at sites with dense vegetation cover, high undergrowth and dry standing reed stalks, as well as small shallow ponds or rivers. Nests were more successful when they were placed higher above ground in patches with greater litter thickness. Predation and flooding were the leading causes of nest failure, accounting for at least 33 and 25 % of 24 nests lost, respectively. We ad- vocate retention of some unharvested reed patches and implementation of irrigation strategies that avoid increas- ing water levels during the breeding period (May-July) of Marsh Grassbirds.

Alternative Rangeland Management Strategies and the Nesting Ecology of Greater Prairie-Chickens

Population declines of grassland birds over the past 30 yr have followed the widespread implementation of intensive rangeland management practices that create homogenous grassland habitats. Patch-burn grazing (PBG) was tested as an alternative management technique that is ecologically similar to historically heterogeneous fire and grazing regimes and holds promise as a rangeland management tool that may benefit grassland wildlife. We conducted a 3-year study to compare nest-site selection and nest survival of greater prairie-chickens, an umbrella species for tallgrass prairie conservation, on private lands managed with PBG or intensive fire and grazing in the Flint Hills of Kansas. The goal of our field study was to evaluate the relationships among rangeland management practices, habitat conditions, and nesting ecology of greater prairie-chickens. Nest-site selection and nest survival of prairie-chickens were both directly related to vertical nesting cover, which was determined by the fire return interval of a pasture. Nesting habitat was affected little by stocking rate in PBG management regimes because preferred nest sites were unburned patches that were not grazed by cattle. Overall, the quantity and quality of nesting sites was improved under PBG management when compared with more intensive rangeland management regimes. Our results join a growing body of evidence that rangeland management strategies that mimic historical heterogeneous fire and grazing regimes benefit native species of prairie wildlife.

One size does not fit all: Importance of adjusting conservation practices for endangered hawksbill turtles to address local nesting habitat needs in the eastern Pacific Ocean

Conservation biologists frequently use data from the same or related species collected in diverse geographic locations to guide interventions in situations where its applicability is uncertain. There are dangers inherent to this approach. The nesting habitats of critically endangered hawksbill sea turtles (Eretmochelys imbricata) cover a broad geographic global range. Based on data collected in the Caribbean and Indo-Pacific, conservationists assume hawksbills prefer open-coast beaches near coral reefs for nesting, and that individual hawksbills are highly consistent in nest placement, suggesting genetic factors partially account for variation in nest-site choice. We characterized nest-site preferences of hawksbills in El Salvador and Nicaragua, where >80% of nesting activity occurs for this species in the eastern Pacific, and ∼90% of hawksbill clutches are relocated to hatcheries for protection. We found hawksbills preferred nest sites with abundant vegetation on dynamic beaches within mangrove estuaries. Nests in El Salvador were located closer to the ocean and to the woody vegetation border than nests in Nicaragua, suggesting female hawksbills exhibit local adaptations to differences in nesting habitat. Individual hawksbills consistently placed nests under high percentages of overstory vegetation, but were not consistent in nest placement related to woody vegetation borders. We suggest conservation biologists use caution when generalizing about endangered species that invest in specific life-history strategies (e.g., nesting) over broad ranges based on data collected in distant locations when addressing conservation issues.

Natural nest-sites of Great Tits (Parus major) in a primeval temperate forest (Białowieża National Park, Poland)

Knowledge of the breeding ecology of the Great Tit Parus major is vast, but almost exclusively concerns birds using nest-boxes. Information on birds nesting in natural conditions is scant. Here, we present the results of the first thorough study on natural nest-sites of the Great Tit. The data, including descriptions of nest-cavity location and dimensions, were collected during 39 breeding seasons in the primeval forest of Bialowieza National Park (BNP), Poland. With an excess of available tree-cavities providing a diverse choice of nesting options, Great Tits nested mainly in non-excavated, very deep and spacious cavities with elongated, narrow openings, placed at intermediate heights in living tree trunks. Different sets of tree species were used in different habitats. The pattern of nest-site utilisation by Great Tits in BNP overlapped with that recorded in other areas, but showed niche separation from other non-excavating hole-breeders in BNP. This indicates that Great Tits have core nest-site preferences, which have probably evolved in response to selective forces such as, e.g., risk of predation, flooding, sufficient nest illumination and/or efficient air ventilation.

Factors predicting summer nest construction of Muscardinus avellanarius in deciduous woodland edges in Slovakia

AbstractForest edges with diverse vegetation are an important feature of habitat preference for the hazel dormouse Muscardinus avellanarius. Therefore, this study was conducted to determine the factors predicting summer nest construction in deciduous woodland edges in Slovakia. At the same time, nest types, dimensions of nests and nest-site preference in shrubs and young trees were analysed. A total of 178 summer nests were found over the years 2010-2013 on the branches of several plant species, but mainly on Prunus spinosa, Rubus fruticosus and Carpinus betulus. The principle component analysis (PCA) in this study revealed that several factors were significant for the construction of nests in shrubby vegetation. The occurrence of four nest types (mixed, layered, foliar and grassy) with relatively large dimensions was confirmed. Botanical analysis of the leaf material in the nests confirmed that ten different plant species were incorporated into the nests. Moreover, a positive correlation was shown between the distance of the nest from the ground and from the top of the plant and the plant height. This study suggests that this micro-habitat may play an important role for suitable nesting of the hazel dormouse, as stated by several authors from the different countries and regions of its large distributional range. At the same time, data on the presence or absence of summer nests in the monitored habitat aid in the detection of species.

Effects on rural House Sparrow and Tree Sparrow populations by experimental nest-site addition

While rural House Sparrows (Passer domesticus) have declined in Sweden, the population of the related Tree Sparrow (P. montanus) has remained stable, suggesting that they are affected by different population regulating mechanisms. Here we investigated if the two species differ in degree of nest-site limitation. After conducting an initial survey of both species on farmsteads in southern Sweden, we supplemented a subset of farms with additional nest-boxes. The farmsteads were resurveyed 3–4 years later to compare any change in population sizes for the two species between farms with and without added nest-sites. We also considered the availability of other nest-sites by counting the number of tile-clad buildings on the farmsteads. We did not find any effect of adding nest-boxes on House Sparrow population sizes, but a significant increase in the population estimate of Tree Sparrows. The number of Tree Sparrows was related to the availability of tile-clad buildings, whereas no such relationship was found for House Sparrows. At low and intermediate population sizes, House Sparrow nest-box utilization declined with the number of tile-clad buildings, suggesting preference for nest-sites under tiles when available. Our results suggest that while Tree Sparrow populations in the southern Swedish farmland are nest-site limited, House Sparrow populations are mainly limited by other mechanisms. Our results suggest that nest-site limitation is unlikely to explain the stronger population decline in rural House Sparrows compared to Tree Sparrows and that nest-site addition is unlikely to be an efficient remedy for the rural House Sparrow decline.

Greater shrub dominance alters breeding habitat and food resources for migratory songbirds in Alaskan arctic tundra.

Climate warming is affecting the Arctic in multiple ways, including via increased dominance of deciduous shrubs. Although many studies have focused on how this vegetation shift is altering nutrient cycling and energy balance, few have explicitly considered effects on tundra fauna, such as the millions of migratory songbirds that breed in northern regions every year. To understand how increasing deciduous shrub dominance may alter breeding songbird habitat, we quantified vegetation and arthropod community characteristics in both graminoid and shrub dominated tundra. We combined measurements of preferred nest site characteristics for Lapland longspurs (Calcarius lapponicus) and Gambel's White-crowned sparrows (Zonotrichia leucophrys gambelii) with modeled predictions for the distribution of plant community types in the Alaskan arctic foothills region for the year 2050. Lapland longspur nests were found in sedge-dominated tussock tundra where shrub height does not exceed 20cm, whereas White-crowned sparrows nested only under shrubs between 20cm and 1m in height, with no preference for shrub species. Shrub canopies had higher canopy-dwelling arthropod availability (i.e. small flies and spiders) but lower ground-dwelling arthropod availability (i.e. large spiders and beetles). Since flies are the birds' preferred prey, increasing shrubs may result in a net enhancement in preferred prey availability. Acknowledging the coarse resolution of existing tundra vegetation models, we predict that by 2050 there will be a northward shift in current White-crowned sparrow habitat range and a 20-60% increase in their preferred habitat extent, while Lapland longspur habitat extent will be equivalently reduced. Our findings can be used to make first approximations of future habitat change for species with similar nesting requirements. However, we contend that as exemplified by this study's findings, existing tundra modeling tools cannot yet simulate the fine-scale habitat characteristics that are critical to accurately predicting future habitat extent for many wildlife species.

Ant colonies prefer infected over uninfected nest sites.

During colony relocation, the selection of a new nest involves exploration and assessment of potential sites followed by colony movement on the basis of a collective decision making process. Hygiene and pathogen load of the potential nest sites are factors worker scouts might evaluate, given the high risk of epidemics in group-living animals. Choosing nest sites free of pathogens is hypothesized to be highly efficient in invasive ants as each of their introduced populations is often an open network of nests exchanging individuals (unicolonial) with frequent relocation into new nest sites and low genetic diversity, likely making these species particularly vulnerable to parasites and diseases. We investigated the nest site preference of the invasive pharaoh ant, Monomorium pharaonis, through binary choice tests between three nest types: nests containing dead nestmates overgrown with sporulating mycelium of the entomopathogenic fungus Metarhizium brunneum (infected nests), nests containing nestmates killed by freezing (uninfected nests), and empty nests. In contrast to the expectation pharaoh ant colonies preferentially (84%) moved into the infected nest when presented with the choice of an infected and an uninfected nest. The ants had an intermediate preference for empty nests. Pharaoh ants display an overall preference for infected nests during colony relocation. While we cannot rule out that the ants are actually manipulated by the pathogen, we propose that this preference might be an adaptive strategy by the host to “immunize” the colony against future exposure to the same pathogenic fungus.

Avoiding perceived past resource use of potential competitors affects niche dynamics in a bird community.

BackgroundSocial information use is usually considered to lead to ecological convergence among involved con- or heterospecific individuals. However, recent results demonstrate that observers can also actively avoid behaving as those individuals being observed, leading to ecological divergence. This phenomenon has been little explored so far, yet it can have significant impact on resource use, realized niches and species co-existence. In particular, the time-scale and the ecological context over which such shifts can occur are unknown. We examined with a long-term (four years) field experiment whether experimentally manipulated, species-specific, nest-site feature preferences (symbols on nest boxes) are transmitted across breeding seasons and affect future nest-site preferences in a guild of three cavity-nesting birds.ResultsOf the examined species, resident great tits (Parus major) preferred the symbol that had been associated with unoccupied nest boxes in the previous year, i.e., their preference shifted towards niche space previously unused by putative competitors and conspecifics.ConclusionsOur results show that animals can remember the earlier resource use of conspecifics and other guild members and adjust own decisions accordingly one year after. Our experiment cannot reveal the ultimate mechanism(s) behind the observed behaviour but avoiding costs of intra- or interspecific competition or ectoparasite load in old nests are plausible reasons. Our findings imply that interspecific social information use can affect resource sharing and realized niches in ecological time-scale through active avoidance of observed decisions and behavior of potentially competing species.

Preferred nest site characteristics reduce predator-specific predation risk in a canopy-nesting raptor

Habitat features influence nest survival and, as a result, identifying relationships between habitat characteristics and nest survival remains a central focus among studies of avian reproduction. In cases where nest predation is the main cause of failure, knowing how the habitat affects predation risk may provide managers with a tangible means by which to improve reproductive success. The Mississippi kite (Ictinia mississippiensis) is a species of regional conservation concern due to small population sizes and high rates of nest failure. We monitored Mississippi kite nests, documented causes of nest failure, and examined relationships between habitat features and predator-specific patterns in nest predation in a floodplain forest in east-central Arkansas. We identified Texas ratsnakes (Pantherophis obsoletus) and owls (Strigidae) as the dominant nest predators and predation by each was influenced by different habitat features. Ratsnake predation was greater in areas with fewer overstory trees and when kite nests were positioned farther above the tree canopy. Owls were more likely to depredate nests farther from the forest edge and nests that had less canopy coverage around them. Our results illustrate that the nest site characteristics preferred by kites reduce nest predation risk, indicating most of the management actions proposed to promote kite nesting are likely to create or maintain quality habitat for this species in the Mississippi Alluvial Valley. Beyond knowing the main causes of nest failure in kites, our results may also provide a glimpse into threats faced by mid-story and other canopy-nesting birds, a guild for which very little information exists regarding causes of nesting failure. © 2014 The Wildlife Society.

Crowding in the city: losing and winning competitors of an invasive bird.

Invasive species can take advantage of resources unexploited by natives (opportunism hypothesis) or they can exploit the same resources but more aggressively or efficiently (competition hypothesis), thus impacting native species. However, invasive species tend to exploit anthropogenic habitats that are inefficiently used by natives such as urban environments. Focusing on the ring-necked parakeet (Psittacula krameri), one of the most invasive birds worldwide, we combined observations of interspecific aggressions, species-specific cavity-nest preferences and the spatial distribution of the native cavity-nesting vertebrate community to determine the invasion process as well as its potential impacts on native species in a Mediterranean city. Our results support the competition hypothesis, suggesting that ring-necked parakeets are outcompeting native species sharing nest-site preferences. Parakeets initiated and won most interspecific aggressions, which were directed towards competitors but also towards predators. This behaviour could explain the spatial arrangement of natives, with most bird species breeding close to parakeets possibly to take advantage of their effective antipredatory behaviour. However, temporal and spatial patterns of segregation suggest that a threatened bat species is negatively affected by parakeets. This demonstrates that common species gain benefits and threatened ones (in this study, a bat and possibly a falcon) lose nest sites due to invaders. Therefore, the conservation status of the native species that pay the costs of competition with invaders should be considered. This scenario of winners and losers may, however, shift towards more losers if the ring-necked parakeet population continues to grow, thus requiring close monitoring and control/eradication programs to avoid further impacts.

Nest site selection by the hazel dormouse Muscardinus avellanarius: is safety more important than food?

Vegetation parameters determining nest site selection by the hazel dormouse Muscardinus avellanarius were studied in a typical habitat where dormice are relatively common in Lithuania, the northern periphery of its distributional range. Dormice preferred nest sites with a better-developed understory, particularly with a good cover of hazel shrubs taller than 4 m and plentiful bird cherry trees, a high diversity of woody plant species in the understory and overstory, and better connectivity of the nest tree with its surroundings. They avoided sites with a high number of mature Norway spruce trees in the canopy and a high density of young trees. In a stepwise multiple regression analysis, three vegetation parameters of the number of shrub species, the cover of hazel shrubs, and the number of Norway spruce trees in the canopy determined over 85% of the index of nestbox use by M. avellanarius. The number of shrub species in the surroundings of the nest site had the highest impact of all. Nest sites used by dormice for breeding were distinguished by a better-developed understory, particularly by a significantly higher number of bird cherry trees and a lower number of Norway spruce trees in the canopy, as well as a higher diversity of plants in the understory and overstory. Selection of nest sites by M. avellanarius is a combination of safety from predators and the presence of food. A well-developed inter-connected understory ensures the safety of nest sites from predators, and the diversity of understory and overstory species guarantees continuity of the food supply in the vicinity of nest sites.