Nest Site Use Research Articles

Nest-site use of the cavity-nesting bird community associated with old-growth longleaf pine forests

Nest-site use of the cavity-nesting bird community associated with old-growth longleaf pine forests

Nest characteristics of African crowned eagles and black sparrowhawks in urban mosaic landscapes: Potential constraints in finding nesting sites and implications for exotic tree management

The increase in human population and continuous landscape transformations, especially in urban areas, will result in most of the natural habitats being degraded, significantly reduced in size and lost. Consequently, constraints in acquiring resources such as nesting sites and food may occur. In this study, we investigated the nesting site characteristics of two raptor species in the urban mosaic landscape of Durban, KwaZulu Natal, South Africa, to determine the potential constraints affecting acquiring nesting sites. Between October 2020 and July 2021, we visited a total of 52 nests occupied by the African crowned eagle (Stephanoaetus coronatus, hereafter crowned eagle) and the black sparrowhawk (Accipiter melanoleucus) in our study area and compared the nest characteristics of the two raptors. Our results showed that exotic tree plantations were the most commonly used as nest sites by both species, suggesting that exotic trees may be crucial in providing nesting sites for both species in this highly modified landscape. Furthermore, our results showed that there was no significant difference in nest height, tree cover, nest cover and distance to (i) road, (ii) building and (iii) water of nests occupied by the two species. However, there was a significant difference between tree height and nearest neighbour distance. Tall, mature trees, slightly isolated from other trees, influenced nest site use for our study species. Innovative conservation measures and strategies could be vital in protecting raptor nesting sites (i.e., exotic tree plantations) in urban mosaic landscapes with natural and managed green spaces.

The evolution of nest site use and nest architecture in modern birds and their ancestors.

The evolution of nest site use and nest architecture in the non-avian ancestors of birds remains poorly understood because nest structures do not preserve well as fossils. Nevertheless, the evidence suggests that the earliest dinosaurs probably buried eggs below ground and covered them with soil so that heat from the substrate fuelled embryo development, while some later dinosaurs laid partially exposed clutches where adults incubated them and protected them from predators and parasites. The nests of euornithine birds-the precursors to modern birds-were probably partially open and the neornithine birds-or modern birds-were probably the first to build fully exposed nests. The shift towards smaller, open cup nests has been accompanied by shifts in reproductive traits, with female birds having one functioning ovary in contrast to the two ovaries of crocodilians and many non-avian dinosaurs. The evolutionary trend among extant birds and their ancestors has been toward the evolution of greater cognitive abilities to construct in a wider diversity of sites and providing more care for significantly fewer, increasingly altricial, offspring. The highly derived passerines reflect this pattern with many species building small, architecturally complex nests in open sites and investing significant care into altricial young. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'.

The importance of fine-scale landscape characteristics for habitat selection in penguins

Investigating the ecology of a species and the spatial requirements needed for their survival within an environment can improve and help develop conservation measures. In this study, we reviewed the literature describing the importance of fine-scale landscape characteristics on the distribution of penguin species. We then investigated little penguin nest-site use across eleven colonies in South Australia, with a focus on nest type, vegetation cover, nest entrance orientation, proximity to the nearest active nest, and side of the island. We showed that both abiotic and biotic variables were important for nest-site use in penguins and that the specific variables varied between species and populations. Little penguins in South Australia did not appear to use nest sites randomly, and active nests were mostly found on the northern side of the island and facing east or west. Our study highlights the importance of gaining a better understanding of penguin nest-site use, and their fitness consequences for populations, to ensure effective conservation outcomes.

Habitats change habits: How Garden Dormice cope with different environments in Germany

The Garden Dormouse is currently disappearing from parts of its range. While its population is declining in many parts of Germany including forest habitats in low mountain ranges, a stable occurrence is found in some cities. A radiotelemetry study was performed in the spruce forests of the Harz National Park (mountains) and the city of Wiesbaden to compare space and habitat use, and the structure and use of daytime nest sites (DNS) used for rest. In total, eight individuals (5 males, 3 females) were tracked between May and September 2021. They used smaller home ranges in the city (MCP100: 2.39 ± 1.34 ha; n = 4) than in the forest (MCP100: 4.56 ± 3.13 ha; n = 4). At night, the animals used structures offering protection from predators and providing food like wide hedges in the city and rock crevices and berry bushes in the forest. The animals were located in a DNS a total of 133 times, and one to ten different DNS per animal were identified. They were situated in structures providing a high degree of protection from predators and also had consistent temperatures (e.g. rock crevices , deadwood piles , hedges, vines on buildings, nest boxes, and buildings). While females rarely changed their DNS, males used several of them. Recommended conservation measures for Garden Dormice include raising public awareness and also the protection and promotion of facade greening, hedges and old buildings in urban areas. A dense rocky cover, as well as a well-developed shrub layer with raspberry bushes are valuable in spruce woodlands .

Nest Architecture of an Endangered Hawaiian Yellow-Faced Bee, Hylaeus anthracinus (Hymenoptera: Colletidae) and Potential Nest-Site Competition from Three Introduced Solitary Bees1

Hylaeus anthracinus is an endemic Hawaiian yellow-faced bee (Colletidae) that is federally protected under the Endangered Species Act of 1973. On O‘ahu, H. anthracinus populations are restricted to a few isolated areas of intact coastal strand habitat. A detailed understanding of H. anthracinus nesting ecology is required to protect and expand the remaining fragmented and isolated populations. Here, we explore how nest parameters such as tunnel inside diameter, cell length, cell partition material, and plant species utilization compare among H. anthracinus and three non-native coastal bee species. Solitary bee nests from coastal habitats on O‘ahu, Hawai‘i were dissected and nest parameters were measured, compared, and described. We found overlap in most nest parameters among H. anthracinus and the introduced species: Hylaeus strenuus, Ceratina smaragdula, and Ceratina dentipes. No significant differences for inside diameter of nest entrance, length of tunnel nest, or # of cells/nest were found among the four bee species that were utilizing cavity nests. Thus, competition for nesting resources could be occurring. This increased understanding of H. anthracinus nest ecology will inform future conservation actions that could include the development of captive rearing programs, translocations, use of artificial nest sites, and the enhancement of natural habitat to increase nesting resources to support the existing populations.

Natural nest sites of the European Starling Sturnus vulgaris in a primeval temperate forest

ABSTRACT Capsule European Starlings Sturnus vulgaris nested mostly in natural holes with strong walls (in live trees), typically excavated by medium-sized woodpeckers (small entrances, deep cavities), and high above the ground. Co-occurrence of these safety-enhancing features suggests that predation avoidance has been the main force shaping patterns of Starling nest site selection. Aims To describe patterns of nest site use by Starlings in a primeval forest and to assess the adaptive value of nest site choice. Methods Observations were made of Starlings breeding in undisturbed conditions in a strictly protected part of the Białowieża National Park, Poland. Intensive searches were made for nests (n = 2039) in permanent observation plots during 46 breeding seasons (1975–2020), coupled with measurements of hole attributes and observations of fate and re-use of nest sites. Results Starlings bred along forest edges in holes located in several species of deciduous tree; tree species used differed among habitats and hole location differed across tree species. The birds bred mostly in holes excavated by woodpeckers (70.3%), in trunks (77.4%) of living trees (84.5%). The median girth at breast height of these trees amounted to approximately 170 cm and median height of holes above the ground was 13 m. Starlings used holes excavated by the medium-sized woodpeckers roughly in proportion to their availability in the forest (tree species, stature, height above the ground). About 39% of holes were re-used in the consecutive years, with some holes being used over several decades. Conclusion The features of Starling nest holes (strong walls, narrow entrances, deep cavities) probably constitute adaptations to the need to evade predators. Their body size allows them to nest in excavated holes without threat of their broods being destroyed by woodpeckers.

An experimental test of information use by wood ducks (Aix sponsa): external habitat cues, not social visual cues, influence initial nest site selection

Birds may use a variety of cues to select a nest site, including external information on habitat structure and nest site characteristics, or they may rely instead on social information obtained directly or indirectly from the actions of conspecifics. We used an experimental manipulation to determine the extent to which a California population of the wood duck (Aix sponsa) used social information gleaned from visual cues inside nest boxes that might indicate the quality or occupancy of that site. Over two nesting seasons, we manipulated the contents of newly installed boxes to simulate one of three states: (1) presence of wood duck eggs, indicating current use of a nest site; (2) presence of down and shell membranes, indicating a previously successful nest; and (3) control nests with fresh shavings indicating an unused box. In addition, we measured habitat characteristics of the area surrounding each box to assess the use of external, non-social information about each nest site. We found no evidence that females laid eggs preferentially, or that conspecific brood parasitism was more likely to occur, in any of the treatments. In contrast, nest site use and reproductive traits of wood ducks did vary with vegetation cover, and orientation and distance of the box from water. Our results suggest that personal information, not social information, influences initial nest site selection decisions when females are unfamiliar with a site. Social cues likely become increasingly important once nest sites develop their own history, and a population becomes well established. In selecting a nest site, birds may use many types of information, including habitat characteristics, their own previous breeding experience, or social cues inadvertently provided by other individuals of the same or different species. We examined information use in a Californian population of wood ducks by experimentally manipulating the visual cues within nest boxes and found that females did not use internal box cues to direct their nesting behaviors, appearing to rely on key habitat characteristics instead. These results contrast with previous studies of this system, suggesting that females may change the cues they use depending on their prior experience with a particular area. In the nest site selection literature, there appears to be a divergence between research on passerines versus waterfowl, and we advocate unifying these perspectives.

Long-term persistence of conservation-reliant species: Challenges and opportunities

“Conservation-reliant species” – those fully dependent on continued management actions – are booming and, with limited conservation budgets, securing funds to sustain their long-term viability is becoming overwhelming. This study assesses the degree of dependence on conservation actions of two obligatory cavity-nesters, the Lesser Kestrel Falco naumanni and the European Roller Coracias garrulus, whose populations in Europe were recently recovered through artificial nest-site provisioning. Using long-term monitoring data and population surveys conducted in their main Portuguese stronghold, we examined temporal changes in the availability and use of semi-natural (cavities in rural abandoned buildings) and artificial nest-sites. We further assessed the financial costs of nest-site provisioning and evaluated the potential use of tourism revenues as a conservation funding source. Following the implementation of conservation projects, the Lesser Kestrel and Roller populations have been increasing but >65% of all breeding pairs currently nest in artificial nest-sites. Semi-natural nest-sites remain suitable for approximately 30 years and are expected to disappear by the end of this century. Lesser Kestrels and Rollers will thus become fully dependent on artificial nest-sites and sustaining their current population sizes is estimated to cost 4500€ per year. This represents <1% of the region's lodging income, largely supported by nature-based tourism. Our findings suggest that reactive conservation measures can be very effective at recovering endangered populations but can make them fully reliant on the perpetuation of those measures. This demands long-term funding, which can be alleviated by tourism revenues in areas with high nature capital values.

Breeding population decline and associations with nest site use of Leach&amp;#8217;s Storm-Petrels on Kent Island, New Brunswick from 2001 to 2018

Breeding population decline and associations with nest site use of Leach&amp;#8217;s Storm-Petrels on Kent Island, New Brunswick from 2001 to 2018

Nest-site fidelity in Lesser Kestrels: a case of Win–Stay/Lose–Shift?

We studied Lesser Kestrels’ (Falco naumanni) conditional nest-site fidelity, i.e., fidelity that depends on the outcome of the previous nesting attempt in that site. In particular, we were interested in examining whether individual kestrels practice a Win–Stay/Lose–Shift (WSLS) strategy towards their nest-sites; that is, does the tendency to use the same nest-site increase following a successful nesting season, but decrease following a failure. For that purpose, we documented the use of nest-sites by Lesser Kestrels and the breeding success in these sites during 1998–2003 in the city of Jerusalem (Israel). We found that while Lesser Kestrels do not practice WSLS strategy towards their nest-site, the males (but not the females) do so towards their sub-colony – they tend to stay in the same sub-colony if their nesting was successful, whereas they tend to migrate to a different sub-colony after failure. A possible explanation to this sexual difference in WSLS behavior can arise from the fact that changing a sub-colony entails a change of hunting area. The male, being the main food provider in the Lesser Kestrel, may be more sensitive to this opportunity.

Breeding biology of the Sayaca Tanager (Thraupis sayaca) in southeast Brazil

ABSTRACTThraupis is a genus of the American endemic Thraupidae (subfamily Thraupinae), comprising seven species that inhabit tropical forests to urban centres. The Sayaca Tanager (Thraupis sayaca) is a disturbance-tolerant species of high representativeness in plant-frugivore networks, but information on its breeding biology is scarce and often restricted to non-systematic surveys. We studied the breeding biology of the T. sayaca, following 39 active nests in a periurban area of southeast Brazil during two breeding seasons (2017/2018, 2018/2019). The breeding season ranged from early September to middle December, and the nests were placed in native and exotic plants and human buildings (nest height above ground: 3.35 ± 1.73 m, mean ± SD). Only females incubated and brooded, but both adults built the nests, fed the nestlings, and removed their faecal sacs. Clutch size was 2.86 ± 0.38 eggs and nest attentiveness was 71.2%. The incubation and nestling periods were, respectively, 13.4 and 17.4 days. Males and females did not differ on nestling provisioning and nest sanitation rates. Nestling provisioning (13.35 ± 6.25 trips/hour) increased with nestling age, while mean brooding time was 37.2% and decreased with nestling age. Apparent nest success was 38.7%, and nest survival according to the Mayfield method was 27.2%. Five nests (20.8%) were parasitised by the Shiny cowbird (Molothrus bonariensis), and we recorded five events of nest-site reuse. We concluded that the most remarkable breeding traits of T. sayaca in comparison with close-related tanagers are the use of anthropogenic nest sites, the higher clutch size and number of feeding trips, and the longer nestling period.

The interrelationship between torpor expression and nest site use of western and eastern pygmy-possums (Cercartetus spp.)

Physiology and behaviour are closely linked, making knowledge of the interaction between species’ energetics and activities important when attempting to understand how animals function in the wild. I examined torpor use by western pygmy-possums (Cercartetus concinnus) and eastern pygmy-possums (C. nanus) in relation to nest site characteristics and movement patterns. In coastal mallee heath in winter, C. concinnus nested beneath leaf litter at the base of dead Banksia ornata, where they employed torpor on 69% of observed days. In warm temperate sclerophyll forest, C. nanus nested in tree hollows of Eucalyptus spp. and used torpor on 64% of days in winter and 10% in summer. Torpor was used in nest sites that were buffered from outside temperature extremes. Both species frequently reused nest sites and while C. nanus was more likely to employ torpor in a previously used site, site familiarity did not influence torpor use for C. concinnus. Additionally, C. nanus was more likely to use torpor in hollows with a higher relative thickness in both seasons. No relationship was found between range size and the number of tracking days or capture body mass, though sample sizes were small. I suggest that the thermal attributes of nest sites influence torpor use for both species and this is likely vital for maintaining a positive energy balance, stressing the importance of preserving habitat with ample potential nest sites for conservation management.

Nest-Site Selection In A High-Density Colony of Burrowing Owls

Although many Western Burrowing Owl (Athene cunicularia hypugaea) populations have been declining, a high-density population nests at the National Radio Transmission Facility (NRTF), Dixon, California. We compared density at NRTF to densities elsewhere, and nest-site use and reuse to available nest substrates. Breeding pairs numbered 24–44 per year, averaging 34 pairs on 83 ha, the fourth-highest on record. Occupancy of eight artificial nest sites installed in 2000 declined from six pairs in 2006 to one pair in 2007 and 2008, and none afterward. Nearest-neighbor distance among artificial nests averaged half the distance among nest sites in fossorial mammal burrows and concrete half-rounds covering aboveground power cables. Undisturbed clay soils supported pocket gophers (Thomomys bottae) but few ground squirrels (Spermophilus beecheyi), whereas disturbed soils supported both ground squirrels and Burrowing Owls. The presence of both ground squirrels and Burrowing Owls was associated with backfill soils over buried cable, cable covers, and areas where soils bordered impervious surfaces. Nest-site reuse was low, with only 12% of the sites occupied in all study years, 2006–2011. Most (78%) nest sites reused in a subsequent year involved nests in a different burrow or cable cover opening >1 m from the previous year's nest. We recommend research on whether concrete half-rounds might outperform buried utility boxes as artificial nests, especially in conjunction with efforts to conserve the fossorial mammals that naturally excavate burrows used by Burrowing Owls.

Raptor nest–site use in relation to the proximity of coalbed–methane development

espanolLa generacion de energia como la extraccion de metano en capas de carbon es un uso importante de la tierra que tiene consecuencias practicamente desconocidas para numerosas especies de animales. Algunas especies de rapaces, dadas de sus necesidades y su evolucion demografica, pueden ser especialmente vulnerables a los cambios en el habitat provocados por la generacion de energia. Utilizando 12.977 observaciones de 3.074 nidos de 12 especies de rapaces durante nueve anos (2003–2011) en la cuenca del rio Powder, en Wyoming, EE.UU., evaluamos la relacion entre el uso de los sitios de nidificacion de las rapaces y la extraccion de metano en capas de carbon. Nuestros objetivos fueron determinar tendencias temporales en los indices de utilizacion de nidos y si el uso de los sitios de nidificacion estaba relacionado con la proximidad a yacimientos de metano en capas de carbon. En la zona de estudio, los indices de utilizacion de los nidos variaron en funcion de la especie y de los anos de forma no lineal. Elaboramos una nueva prueba de aleatorizacion para evaluar las diferencias de uso entre los nidos en zonas extractivas y zonas no extractivas, a la vez que se controlaba la variacion anual del uso de los sitios de nidificacion. El ratonero de cola roja (Buteo jamaicensis), la lechuza madriguera (Athene cunicularia) y el buho chico (Asio otus) utilizaron nidos en zonas no extractivas mas que en zonas extractivas (es decir, nidos cercanos a yacimientos de metano en capas de carbon). Las diferencias entre los grupos fueron ambiguas para las otras nueve especies; no obstante, hemos de advertir que probablemente teniamos menor potencia estadistica para detectar diferencias en especies menos frecuentes. Nuestros resultados sugieren que algunas especies podrian evitar nidificar en zonas cercanas a los yacimientos de metano en capas de carbon y revelan que los efectos de esta sustancia pueden ser relativamente constantes en un radio de entre 400 y 2.415 m de los pozos. En estudios futuros se deberian analizar a las preferencias de habitat y a la eficacia biologica, y controlar otros factores decisivos como la disponibilidad de presas en el ambito local, la densidad de rapaces y las condiciones meteorologicas. EnglishEnergy development such as coalbed–methane (CBM) extraction is a major land use with largely unknown consequences for many animal species. Some raptor species may be especially vulnerable to habitat changes due to energy development given their ecological requirements and population trajectories. Using 12,977 observations of 3,074 nests of 12 raptor species across nine years (2003–2011) in the Powder River Basin, Wyoming, USA, we evaluated relationships between raptor nest–site use and CBM development. Our objectives were to determine temporal trends in nest–use rates, and whether nest–site use was related to the proximity of CBM development. Across the study area, nest–use rates varied across species and years in a non–linear fashion. We developed a novel randomization test to assess differences in use between nests at developed and undeveloped sites, while controlling for annual variation in nest–site use. Red–tailed hawks (Buteo jamaicensis), burrowing owls (Athene cunicularia), and long–eared owls (Asio otus) used nests in undeveloped areas more than nests in developed areas (i.e. nests near CBM development). Differences between development groups were equivocal for the remaining nine species; however, we caution that we likely had lower statistical power to detect differences for rarer species. Our findings suggest potential avoidance of nesting in areas near CBM development by some species and reveal that CBM effects may be fairly consistent across distances between 400–2,415 m from wells. Future work should consider habitat preferences and fitness outcomes, and control for other key factors such as local prey availability, raptor densities, and weather.

Nest Height and Vertical Vegetation Associated with Black-capped Vireo Breeding Success in Southwest Texas

Vireo atricapilla (Black-capped Vireo) is an endangered songbird whose habitat use has been well studied in central portions of its breeding range, which is characterized by successional vegetation communities. To expand our understanding of habitat use as it relates to reproductive success, we studied Black-capped Vireo habitat use at the territory and nest-site scales in southwest Texas in 2009 and 2010, an area characterized by xeric and stable vegetation communities. We measured vegetation in territories and at nests to evaluate the influence of habitat variables on nest parasitism and nest survival. Our results showed that Black-capped Vireo nest-site use in southwest Texas differed from that in breeding areas of central Texas and Oklahoma. Black-capped Vireos in southwest Texas used nest sites with a wide range of woody cover (70 ± 13%) and used Juniperus spp. (junipers) as a nest substrate proportionately more than its availability in territories, which is contradictory to previously published literature. Nest parasitism increased significantly with greater nest height, likely due to increased visibility to Molothrus ater (Brown-headed Cowbird). Increasing height of vertical cover above the nest was associated with decreased overall nest survival, likely because nests placed in habitat with taller vegetation are more susceptible to avian predators and Brown-headed Cowbird parasitism. Unlike the findings of studies conducted in the northern part of the species' breeding range, we found that parasitism did not increase the likelihood of depredation or abandonment. Our results indicate that Black-capped Vireo habitat structure and composition, as well as factors influencing nest success in Southwest Texas, differ from their breeding habitat in central Texas and Oklahoma, indicating that management guidelines need to be regi on-specific.

分断された狭小森林に生息するエゾモモンガPteromys volans oriiによる巣の利用

分断された狭小森林に生息するエゾモモンガPteromys volans oriiによる巣の利用

Do increases in the availability of standing dead trees affect the abundance, nest-site use, and niche partitioning of great spotted and middle spotted woodpeckers in riverine forests?

Standing dead trees may be a limited resource for woodpeckers in managed forests, especially for species that rely on dead wood for their nest or roost cavity, and as foraging sites. Effective conservation strategies for woodpeckers require a detailed knowledge of species’ responses to dead wood availability. To investigate the importance of standing dead wood (snags) for the abundance and nest-site use of the great spotted woodpecker Dendrocopos major and middle spotted woodpecker Leiopicus medius in mature riverine forests, we compared the responses of birds between two periods—before mass mortality, and during a pulse in standing dead trees. The density of standing dead trees available for cavity excavation by the great spotted woodpecker and the middle spotted woodpecker increased significantly during the study period: 37-fold and 4-fold, respectively. Temporal trends in the abundance of both woodpecker species from 2000 to 2015 were not significant. Great spotted woodpeckers were significantly more likely to use dead trees and places with wounds in species other than oak and ash during the outbreak period than in the pre-outbreak period. Middle spotted woodpeckers were significantly less likely to excavate cavities in tree species other than oak and ash in the outbreak period, but dead trees were more likely selected. An interspecific comparison suggests that the probability of a nest-hole having been excavated by a middle spotted woodpecker increased with a nest-hole sited in ash, in a dead tree, in a limb/branch, and decreased with a nest-hole in a closed forest. These findings suggest that woodpecker species, especially weak excavators, may benefit from an increase in dead wood availability leading to nest niche shifts into more favorable substrates for cavity excavation. However, a strong increase in dead wood availability does not modify the general pattern of niche partitioning between great spotted and middle spotted woodpeckers. Conservation plans for the specialized middle spotted woodpecker must consider the preference for dead and decaying trees. The decreasing number of large ashes and oaks, and the lack of natural regeneration of the latter species, may negatively affect the middle spotted woodpecker in the future.

Breeding Success and its Correlation with Nest-Site Characteristics: A Study of a Griffon Vulture Colony in Gamla, Israel

Abstract Gamla Nature Reserve once held the largest colony of nesting and roosting Griffon Vultures (Gyps fulvus) in Israel, with 45 to 57 pairs nesting at the colony during our study years (1998–2002), and up to 140 individuals roosting on the canyon's cliffs. Nevertheless, the fledging success there was very low: only 34% of breeding attempts (nest with eggs laid) resulted in fledged young during our study. Poisoning and hunting were the main causes of mortality, but in addition, a shortage of appropriate nesting places may also have been an important limiting factor. Fledging percentage was correlated with nest-site use and “attractiveness”: nest sites with greater fledging percentage also had more breeding attempts and were inhabited earlier in the nesting season. The main physical characteristic that enhanced breeding success was the type of nest site; nests in caves were more successful and were used for more breeding attempts than nests that were exposed from above. The influence of microclimatic c...

Nest Sites of a Strong Excavator, the Great Spotted WoodpeckerDendrocopos major, in a Primeval Forest

In managed forests, birds that create their own breeding holes in trees have limited access to substrates in which they can excavate. Therefore, nest site use in these forests possibly reflects availability of substrates more than species preferences. We analysed data on nest sites of Great Spotted Woodpeckers Dendrocopos major collected during 1987–2013 in the strictly protected part of Bialowieza National Park in East Poland. The woodpeckers excavated breeding holes in 11 tree species, but species used in individual habitats varied greatly: Alder Alnus glutinosa was almost the only species used in the riverine forest; Aspen Populus tremula, Hornbeam Carpinus betulus and Pedunculate Oak Quercus robur were used most often in oak-lime-hornbeam forest, whereas Scots Pine Pinus sylvestris and P. tremula were used most in coniferous habitat. In oak-lime-hornbeam habitat, the birds strongly preferred to excavate in P. tremula and Q. robur, in the coniferous habitat the birds preferred P. sylvestris and P. trem...