Nest Site Characteristics Research Articles

Eastern Wood-Pewee (Contopus virens) reproductive success in red pine plantations and deciduous forests in Ontario, Canada

Pine plantations comprise about 7% of total world forest cover and are increasing across the globe. We compared settlement times, breeding densities, and the effects of time, habitat, and nest-site characteristics on the nest success of Eastern Wood-Pewees (Contopus virens) in red pine (Pinus resinosa) plantations and deciduous forest stands in south-central Ontario, Canada, in 2007 and 2008. Our goal was to evaluate the quality of these 2 habitats for this declining aerial insectivore. Pine plantations and deciduous forest stands were settled nearly simultaneously and at similar breeding densities, suggesting no preference for either habitat. Nest success in pine plantations (22%) was lower than in deciduous forests (35%), corresponding to higher counts of red squirrels (Tamiasciurus hudsonicus) and Blue Jays (Cyanocitta cristata) in plantations. Daily nest survival was lowest when nestlings were about 5 d old, but improved substantially as nestlings aged, and over the nesting season. In both habitats, increased nest visibility was correlated with decreased nest survival. In pine plantations, nest survival was higher where trees were more dispersed, while in deciduous forests, nests situated farther from tree trunks had higher survival rates. In both habitats, Eastern Wood-Pewees may use outward branches, when available, to detect movement and then evade potential nest predators. Although pine plantations provide breeding habitat for Eastern Wood-Pewees, management that increases hardwood understories and overstories may help to reduce visibility of Eastern Wood-Pewee nests and to reduce the populations of generalist songbird predators.

Direct and Indirect Effects of Nesting Site Characteristics for a Cliff-Nesting Raptor in Western Alaska

Habitat suitability for breeding birds is defined at scales ranging from the landscape to individual nesting sites. Nesting site characteristics that govern exposure to inclement weather may affect breeding success, although attempts to understand this effect for Arctic breeding raptors have yielded ambiguous results. Further, breeding adults incur substantial costs from incubating eggs and brooding nestlings, and it is possible that greater site exposure results in increased nest attendance rates, increasing their cost of breeding. We quantified nesting site characteristics of Gyrfalcons (Falco rusticolus) and assessed how breeding parameters and nest attendance rates varied by protective site qualities on Alaska's Seward Peninsula, 2014–2019. The degree of physical exposure in the horizontal plane correlated negatively with the probability of hatching and fledging (provided hatch occurred), as well as overall productivity. The negative effect of horizontal exposure on the probability of fledging and productivity was greatest at nesting sites that were also more exposed in the vertical plane, although this interaction did not affect the probability of hatching. Early breeding pairs had higher productivity and tended to select more protected nesting sites. Additionally, nest attendance rates were higher in more horizontally exposed nesting sites, particularly when nestlings were approximately 2 wk old. The increased nest attendance and concurrent decreased productivity associated with greater nesting site exposure demonstrated that nesting site characteristics can have direct and indirect effects on Arctic breeding raptors and also highlight the importance of small-scale variables when evaluating habitat suitability.

Aspects of the Ecology of Urban-Nesting Bald Eagles (Haliaeetus leucocephalus) in South-Coastal British Columbia

Bald Eagle (Haliaeetus leucocephalus) populations throughout North America have increased considerably since the ban of DDT in 1972 and eagles now inhabit suburban areas in large numbers. To better understand the ecology of urban populations living in south-coastal British Columbia, we compared nest-site characteristics, reproductive rates, and diets of more than 150 breeding pairs of rural-, suburban- and urban-nesting eagles in the Greater Vancouver area. Three-quarters of the nests were located within 230 m of buildings and roads, or within 31 m of a potential source of disturbance. Urban eagles nested in live, taller trees that were close to the edges of patches, whereas rural eagles used shorter trees and occasionally human-made structures such as transmission towers. Eagles at nests located close to patch edges and in areas with greater human land use had higher reproductive rates than those at isolated nests or in remote rural habitat. Waterfowl and gulls (family Laridae) were common in the diet across the study area, but urban eagles also used alternative sources such as C-O sole (Pleuronichthys coenosus), Bufflehead (Bucephala albeola), and Band-tailed Pigeon (Patagioenas fasciata). Eagles in the Vancouver area have adapted to human-altered landscapes; management strategies should focus on maintaining edge habitat, monitoring population expansion in urban areas, and protecting nest sites.

Wild Turkey Nest Success in Pine‐Dominated Forests of the Southeastern United States

ABSTRACTNest success is a primary component of productivity for wild turkeys (Meleagris gallopavo; turkeys) and there is concern that turkey productivity is declining across the southeastern United States. We evaluated the influence of nest site and landscape characteristics on risk of nest failure for turkeys in pine (Pinus spp.)‐dominated forests across the southeastern United States. We used Cox proportional hazard models to evaluate daily hazard of nest failure associated with nest site and landscape metrics within 500‐m and 1‐km buffers centered on nests. Of 451 nests monitored (n = 320 females) between 2014 and 2018, 76% failed, with predation as the primary cause. Daily hazard of nest failure increased by 1.2% for each day that females delayed nest incubation following the mean nesting date (29 Apr; βday = 0.010 ± 0.002 [SE]; hazard ratio [HR] = 1.01, 95% CI = 1.006–1.015). Environmental covariates associated with risk of nest failure included the maximum enhanced vegetation index (EVI) and distance to the nearest ecotone. Daily hazard increased with increasing distance away from an ecotone (βecotone = 0.16 ± 0.06; HR = 1.17, CI = 1.03–1.32) and with lower EVI around the nest (βEVI = −0.30 ± 0.06; HR = 0.74, CI = 0.65–0.83). Additional nest site or landscape covariates were included in competitive models but did not influence risk of nest failure significantly. Our study highlights the importance of considering landscape context when designing and implementing land management actions intended to enhance wild turkey reproduction. Our findings suggest that landscape metrics thought to be important to turkeys in northern agro‐forested landscapes may not be relevant to turkeys in pine ecosystems of the southeastern United States. © 2021 The Wildlife Society.

Colony characteristics influence nest survival of Caribbean Roseate Terns

AbstractDetermining how site characteristics influence reproductive success can help guide conservation planning for declining wildlife populations. For colonially breeding seabirds, nest survival and predation risk can be influenced by both colony and nest site characteristics such as colony size, nest density, and nest location. We evaluated the reproductive success of a declining population of Roseate Terns (Sterna dougallii) in the United States and British Virgin Islands to identify primary causes of nest failure and investigate the influence of colony and nest site covariates on nest survival. In addition, we measured the influence of colony characteristics on chick provisioning to determine if resource competition in larger colonies affected foraging rates. Monitoring was conducted in 2017–2018 via motion-triggered cameras, which enable 24-hr monitoring with minimal nest disturbance. Nest survival was defined by both hatch success and early chick success, defined as a chick surviving from hatching through the fourth post-hatch day. We monitored 118 nests in 6 colonies over the 2 breeding seasons. We found that predation was the primary cause of nest failure. Both hatch and nest success increased with colony size, and neither nest survival nor predation probability was influenced by individual nest site characteristics. Provisioning rates were comparable among colony sites and did not vary with colony size. Our results suggest that directing management efforts toward enhancing colony size, rather than focusing on nest site characteristics, can be beneficial for tropical seabird conservation.

Seasonal patterns in nest survival of a subtropical wading bird, the Hawaiian Stilt (Himantopus mexicanus knudseni).

Nest survival is influenced by where and when birds decide to breed. For ground-nesting species, nest-site characteristics, such as vegetation height and proximity to water, may impact the likelihood of nest flooding or depredation. Further, habitat characteristics, and thus nest survival, may fluctuate across the breeding season. The Hawaiian Stilt (‘Ae‘o; Himantopus mexicanus knudseni) is an endangered Hawaiian waterbird that nests in wetlands across the Hawaiian Islands. In this study, we used observational surveys and nest cameras to examine the impact of nest-site characteristics and day of nesting season on nest survival of the Hawaiian Stilt. Early nests had a higher chance of survival than late nests. For most of the nesting season, taller vegetation was correlated with increased nest survival, while shorter vegetation was correlated with increased nest survival late in the nesting season. Seasonal patterns in nest survival may be due to changes in parental behavior or predator activity. Nest depredation was responsible for 55% of confirmed nest failures and introduced mammals were the primary nest predators. Our study is the first to examine seasonality in nest survival of Hawaiian Stilts and suggests that, despite longer nesting seasons and year-round occupation of wetlands, late nesters in subtropical regions may have lower nest survival than early nesters, similar to trends observed in temperate regions.

The role of woodpeckers (family: Picidae) as ecosystem engineers in urban parks: a case study in the city of Madrid (Spain)

Many species of the family Picidae, such as the woodpeckers, excavate the tree-cavities where they nest. Frequently the cavities are used during a single breeding season and subsequently abandoned, which allows their use by non-excavator species for nesting or roosting. Here we analyze the role of woodpeckers as providers of nesting and refuge places in two urban parks in the city of Madrid. The environmental characteristics of the woodpecker nest-sites were also studied. Prior to the breeding season 75 trees bearing woodpecker-excavated cavities and 142 control trees (i.e. without woodpecker cavities) were located, georeferenced and characterized by a set of variables relative to the tree and its environment. During the breeding season the cavities were monitored with an endoscopic camera to verify occupation and user identity. Additionally, 71 non-excavated tree-cavities were monitored to measure their occupancy and make comparisons with those excavated by woodpeckers. Woodpeckers showed a strong preference for trees of the genus Populus: 54 of 75 (72%) woodpecker-cavities were in poplars, which comprised only 7–10% of available trees. The excavated cavities were found mainly in the trunk of the trees, north oriented and away from paths. The occupancy rate by bird species was higher, although not significantly, for excavated cavities than for natural cavities (36.0% and 23.9% respectively). The richness and composition of cavity-user species also differed between types of tree-cavities. This work shows the importance of woodpeckers as providers of nesting and refuge places for other cavity-user birds and highlights their role as ecosystem engineers in urban parks. Finally, we consider that these results can guide biodiversity conservation efforts in urban planning.

Teaching old dogs and young dogs new tricks: canine scent detection for seabird monitoring

Dogs Canis familiaris have been domesticated for over 11,000 years and have been trained to perform a vast array of tasks. Scent dogs are routinely used to detect elusive animals of conservation concern as well as the presence of invasive nonnative predators. However, a recent review of studies on scent dogs for nature conservation found few peer-reviewed papers on detection of seabirds, and we suggest the potential of scent dogs for seabird monitoring is currently under-utilised. To stimulate wider consideration of the use of scent dogs for seabird monitoring we: (i) document the training, testing and performance of a one-year old Golden Retriever, to detect scent from European Storm Petrels Hydrobates pelagicus, and to differentiate between scent of European Storm Petrels and Manx Shearwaters Puffinus puffinus, and (ii) report on the field performance of a 12-year old Border Collie to detect Manx Shearwaters breeding in natural nest burrows and artificial nest boxes. We show that these individual dogs had a high success rate in locating hidden seabird targets by scent in experimental and field settings and we highlight some of the set-backs encountered during the training process, and their solutions. We show that the detection of occupied Manx Shearwater burrows is dependent on their depth and recent history of occupation. Our results highlight the potential value of scent dogs to establish the presence of particular seabird species at sites where breeding status is currently uncertain, and to map the extent of occupied areas. Further work is needed to validate the use of scent dogs to determine seabird breeding density in real-world situations, where detection probability may be influenced by nest site characteristics and breeding density. We stress the need to involve professionals in the selection, training and testing of scent dogs.

Drivers of nest survival in the Tawny-bellied Seedeater Sporophila hypoxantha (Aves: Thraupidae): time-specific factors are more related to success than ecological variables.

Tawny-bellied Seedeater (Sporophila hypoxantha) is an endangered (in Brazil) grassland dependent species, whose breeding success remains poorly known hampering conservation measures on its breeding grounds. Here we analyze the nest survival of the species in relation to temporal and environmental variables over three breeding seasons in hilly dry grasslands in southern Brazil. The apparent nest success was 40%, and MARK survival 20%. Predation was the main cause of failure, affecting 55% of the unsuccessful nests, followed by desertion, infestation by Philornis fly larvae, cattle trampling and burning. The productivity was 1.77 young per pair. Best models include time-specific factors (nest age and time of breeding season), reflected by a gradual reduction in nest survival over the nesting cycle, accompanied by an increase in temperature, subcutaneous larvae infestation, and predation. Nest site characteristics did not influence nest survival. Predation is more prevalent in the nestling rearing period than during incubation. This tendency may be caused by an increase in the activity in the nests, as is predicted by the Skutch hypothesis. The conclusion that time-specific factors influence nest survival more than ecological variables is important to plan on seasonally dependent conservation and management measures.

Breeding behavior of the Helmeted Manakin Antilophia galeata (Passeriformes: Pipridae) in a gallery forest from São Paulo state, Brazil

ABSTRACT Information on the breeding biology of most Neotropical birds, and interpopulation comparisons, are insufficient. The Helmeted Manakin, Antilophia galeata (Lichtenstein, 1823), is a forest understory passerine commonly found in the gallery forests of the tropical savanna-like Cerrado biome. We provide information about the nesting phenology, nesting cycle, nests, eggs, nestlings, and nest-site characteristics of a population of the Helmeted Manakin in the state of Sao Paulo, southeastern Brazil. During two breeding seasons we found 16 active, and 30 inactive nests. Breeding activities occurred from mid- August to mid- January, and nests were constructed in bushes and saplings in the forest’s understory, 0.45-3.48 m above ground (1.56 ± 0.66 m). Clutch size was two eggs, which were laid in intervals of one to three days. Three remarkable patterns of interclutch egg color and marking variations were observed. The incubation period of two nests was 18 and 19 days, and nestling periods were 16.3 ± 0.6 days (16-17 days, n = 3 nests). The apparent nest survival of 11 thoroughly monitored nests was 36.4%. In addition to the first description of the interclutch egg pattern variations, the following information differs from previous literature data: egg laying interval and nestling periods. Our data contribute to the overall knowledge of the variations in breeding parameters of the Helmeted Manakin.

The Role of Cognition in Social Information Use for Breeding Site Selection: Experimental Evidence in a Wild Passerine Population

In spatio-temporally variable environments, individuals are known to use information for making optimal decisions regarding where and when to breed. Optimal decision making can be complex when relying on multiple information sources with varying levels of reliability and accessibility. To deal with such complexity, different cognitive abilities such as learning and memory might enable individuals to optimally process and use these information sources. Yet, the link between information use and cognitive ability remains unexplored in natural populations. We investigated whether learning performance on a problem-solving task was related to the use of an experimentally manipulated source of social information for nest site selection in wild collared flycatchers (Ficedula albicollis). Collared flycatchers are known to use heterospecific information from their main competitors, the great tits (Parus major). Here, we created a local apparent preference by tits for an artificial nest site feature (a geometric symbol attached to nest boxes occupied by tits) and recorded whether flycatcher pairs chose to settle in nest boxes displaying the same feature as tits (i.e., copied tit apparent preference). Using a problem-solving task requiring opening a door temporarily blocking the nest box entrance, we then measured flycatchers' learning performance during nestling rearing as the number of entrances required to solve the task and enter the nest box twice in a row below a given efficiency threshold. We found that the probability to copy tit preference decreased with decreasing learning performance in females, particularly yearling ones: fast learning females copied tit preference, while slow learning ones rejected it. Male learning performance did not affect copying behavior. Our results showed that learning performance might play an important role in the ability to optimally use information for nest site selection in females: both fast and slow learning females could process this heterospecific information source but used it differently. This could partly explain the link between cognitive abilities and reproductive success reported in previous studies. Whether cognitive abilities may modulate condition-dependent costs of using different information remains to be explored.

Role of the thermal environment in scaled quail (Callipepla squamata) nest site selection and survival

Temperature is increasingly recognized as an important component of wildlife habitat. Temperature is particularly important for avian nest sites, where extreme temperatures can influence adult behavior, embryonic development, and survival. For species inhabiting arid and semiarid climates, such as the scaled quail (Callipepla squamata), frequent exposure to extreme temperatures may increase the importance of the nest microclimate. Limited data suggest that scaled quail respond to temperature when selecting nest sites, and they are also known to respond to the presence of surface water and shrub cover on the landscape, two resources which may mitigate thermal stress. To better understand the role of temperature in nest site selection and survival, and to evaluate how other landscape resources may benefit nesting quail, we investigated nest site characteristics of scaled quail in southeastern New Mexico, USA. During the breeding seasons of 2018 and 2019 we located nests, monitored nest fate, and recorded thermal and vegetation characteristics at three spatial scales: the nest bowl, the nest microsite (area within 10m of the nest bowl), and the landscape. We found that nest bowls moderated temperature relative to both the surrounding microsite and the broader landscape, remaining almost 5°C cooler on average than the surrounding microsite at mid-day. Nest bowls also had taller, greater cover of vegetation compared to both the surrounding microsites and the landscape. Despite apparent selection for cooler temperatures and taller vegetation, these characteristics demonstrated a weak relationship with nest survival. Rather, nest survival was positively influenced by proximity to surface water and honey mesquite (Prosopis glandulosa), with survival decreasing with increasing distance from these features. Although the mechanism for this relationship is unclear, our results support the importance of temperature for nest site selection of ground-nesting birds in semiarid landscapes, and suggest further exploration of landscape-level sources of thermal mitigation.

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.

Nest-site selection of a subarctic-breeding shorebird: evidence for tree avoidance without fitness consequences

Vegetation communities in the subarctic are at risk of change due to climate-driven tree and shrub encroachment. Vegetation change may lead to unsuitable habitat for arctic-breeding birds, many of whom are declining. Although many possible factors are contributing to their decline, loss of breeding habitat could be a major contributor. We examined nest-site selection in Dunlin (Calidris alpina hudsonia (Todd, 1953)), a shorebird that nests in open fen habitats in the Churchill, Manitoba, Canada, region. Our objective was to determine whether this species avoids treed habitats and the possible fitness consequences for this. We examined the role of vegetative horizontal and vertical concealments on nest-site selection and nest fate. Dunlin selected nest sites with lower densities of trees than present at unused sites (40 m radius). Both horizontal and vertical concealments were significantly greater at nests than at unused sites, and horizontal concealment was greatest in the north. No measure of tree density or height, or concealment, significantly predicted nest fate. Although Dunlin appear to select nest sites that may minimize exposure to northerly winds and that may provide cover against potential predators, the current nest-site characteristics are not reinforced by contemporary selection.

Nests built on power lines: Nest-site selection by long-tailed broadbills (Psarisomus dalhousiae) in Nonggang of Guangxi, China

The quality of breeding habitat may directly affect the survival and development of progeny. Therefore, the selection of a suitable nest-site is an important factor affecting the reproductive success of birds. The most important reason for a bird’s reproductive failure is nest predation. Predation may cause birds to change their nest-sites and even nest morphology. Here we investigated the nest-site characteristics by long-tailed broadbills ( Psarisomus dalhousiae) in Nonggang, Guangxi, southwestern China. Our results showed that long-tailed broadbills in Nonggang mainly build their nests on power lines (88.5%) and nest-site selection was mainly affected by predation pressure and food resources. At the same time, nest-site concealment was trade-off against predator avoidance. This anti-predator strategy effectively utilizes human infrastructure.

Nest site selection by Loggerhead Shrike (Lanius ludovicianus) in a fragmented landscape

Understanding which factors influence nest site selection can lead to more effective species conservation. The Loggerhead Shrike (Lanius ludovicianus) has experienced severe declines since the 1940s and could potentially benefit from fine-scale management for nesting habitat, especially where fragmentation impedes conservation at the landscape scale. We examined how habitat characteristics at the nest tree and territory core scales influenced nest site selection by Loggerhead Shrikes in the coastal plain of South Carolina. We found 41 Loggerhead Shrike nests and measured habitat characteristics at the nest site and at available sites to model selection factors at the tree and territory core scales. Loggerhead Shrikes selected for low heterogeneity of vegetation density, high heterogeneity of vegetation height, and lower shrub and tree densities at the territory core scale. Loggerhead Shrikes also preferred nest trees with larger diameters at breast height. Overall, Loggerhead Shrikes appeared to select for nest site characteristics that enhanced foraging ease and success, and limited predation risk. We suggest that landowners in the southeastern coastal plain increase grassy habitat on their property and retain large trees in suitable nesting locations to increase optimal nesting habitat for Loggerhead Shrikes.

Breeding site records of three sympatric vultures in a mountainous cliff in Kahara-Thathri, Jammu & Kashmir, India

The current communication deals with the breeding records of three sympatric vultures, viz., Himalayan Vulture Gyps himalayensis, Egyptian Vulture Neophron percnopterus, and Bearded vulture Gypaetus barbatus from a mountain cliff in Kahara, Thathri, a part of upper Chenab catchment in the union territory of Jammu and Kashmir. Made of twigs and lined by dry grass, the nests mostly east-facing, were built on the ledges or in cavities and small caves on cliffs well protected from predators. The inaccessibility, rugged topography (for nesting) and the abundant food base (gorals, monkeys, langurs, pikas, and rodents) make it an ideal nesting location for the vultures. Authors suggested that intensive studies are required to be taken up on the resource apportionment and influence of habitat variables (climate, terrain, disturbance) on the nest site characteristics in such rugged landscapes.

Nesting ecology of Polistes gallicus (Hymenoptera: Vespidae) in South-Western Spain

Among the numerous factors that contribute to the success of social wasps, colony productivity is the most important and depends on ecological and environmental factors, such as the nest site. Consequently, nest-site choice should be determined by nest-site characteristics. The objective of this study was to determine on which species of plants Polistes gallicus wasps build their nests and identify the possible preferred features of plants used during nest-site selection by the foundress. From February to October 2017-2019 we recorded details of the nests in natural areas in south-western Spain (at 38° latitude). Nests of P. gallicus were recorded on 49 species of plants belonging to 23 families, with Scirpoides holoschoenus, Epilobium hirsutum and Foeniculum vulgare the most common. Significantly more wasps built their nests on herbaceous than on shrub and arboreal plants, and on green than brown-grey plants. Most of the nests were 21 to 189 cm above the ground, with a nest azimuth of about 102°. Nests were located at a mean distance of 43.51 ± 123.79 m from the nearest source of water. The length of the nesting season in the area studied was between 30 and 33 weeks, and more colonies were founded by a single foundress than several foundresses. Furthermore, a greater percentage of the single foundress colonies failed than of the multiple-foundress colonies.

Nest site characteristics of cavity-nesting birds on a small island, in Haida Gwaii, British Columbia, Canada

Many studies of cavity-nesting birds in North America are conducted in large continental forests and much less is known about them in island ecosystems. We describe a 29-year study of tree species, nest site characteristics, and fledge dates of cavity-nesting birds on a small island in Haida Gwaii, British Columbia (BC). Seven cavity-nesting bird species were documented on East Limestone Island and 463 nests were found in 173 different trees. Nest trees were significantly taller and had a greater diameter than a random sample of snags. Tree height did not differ among bird species but diameter at breast height was larger for trees used by Brown Creeper (Certhia americana) than for other species. Cavity-nesters selected tree decay classes 2–7 (all dead/near dead [snags]), with 85% in decay class 4 (35%) or 5 (50%), similar to the random snag sample (class 4, 32%; class 5, 42%). Cavity height ranged from 2.6 to 44.9 m and for all species, except Brown Creeper, the mean nest height was >60% of the mean tree height. Nest heights were generally greater than observed elsewhere in BC. Nest cavity orientation was random except for Red-breasted Sapsuckers (Sphyrapicus ruber), for which only 13% of the cavity entrances faced southeast. Median fledging dates ranged from 7 June (Chestnut-backed Chickadee [Poecile rufescens]) to 28 June (Northern Flicker [Colaptes auratus]). Estimated median dates of clutch completion were similar for all species. Our results show that large snags provide habitat for a high diversity of cavity-nesting birds on Haida Gwaii.

Behavioural traits modulate the use of heterospecific social information for nest site selection: experimental evidence from a wild bird population.

The use of social information for making decisions is common but can be constrained by behavioural traits via, for example, the ability to gather information. Such constrained information use has been described in foraging habitat selection; yet it remains unexplored in the breeding habitat selection context, despite potentially strong fitness consequences. We experimentally tested whether three behavioural traits (aggressiveness, boldness and neophobia) affected the use of heterospecific social information for nest site selection in wild collared flycatchers Ficedula albicollis. Flycatchers have previously been found to copy or reject an artificial apparent preference of tits (their main competitors) for a nest site feature: they preferred nest-boxes with the same or a different feature, depending on tit early reproductive investment. Here, we confirmed this result and showed that shy individuals and less aggressive old males (i.e. 2 years old or older) copied tit apparent preference, while more aggressive old males rejected the tit preference. Aggressiveness and boldness may allow males to access more information sources or affect males' interactions with dominant tits when selecting a nest site. Our study highlights the links between variation in behaviours and social information use for breeding habitat selection and calls for further work to explore underlying mechanisms.