Secondary Cavity-nesting Birds Research Articles

The effects of environmental conditions on eggshell thickness of two North American secondary cavity-nesting birds

The effects of environmental conditions on eggshell thickness of two North American secondary cavity-nesting birds

Nest-Site Features and Breeding Ecology of Chestnut-Vented Nuthatch Sitta nagaensis in Southwestern China.

The breeding ecology of birds is the cornerstone of bird life-history theory, and breeding success directly affects the survival and development of populations. We studied the breeding ecology of a secondary cavity-nesting bird, the chestnut-vented nuthatch Sitta nagaensis, in southwestern China from March to June in 2020, 2021, and 2022. In total, 16 nests in nest boxes and 19 nests in natural cavities were studied. The nesting habitat was mainly Pinus yunnanensis forest (68.4%), and the nest trees were mainly P. yunnanensis and pear Pyrus spp. Cavities made by woodpeckers and knot holes were used as nest sites, and the nuthatches plastered the hole entrance with mud. The nesting material was mainly pine bark. The clutch size was 3.47 ± 0.56 (range 2-4, n = 30), with an incubation period of 16.06 ± 0.91 days (range 15-19 days, n = 18). The nestling period was 20.88 ± 1.90 days (range 18-23 days, n = 23), and both parents fed the nestlings.

Ticks in the box: Argas persicus occurrence in nest boxes of secondary cavity-nesting bird species in Italy

Migratory organisms can be vectors of parasitic host organisms that can then be transported along seasonal migratory journeys and spread across continents. Ornithophilic nidicolous ticks (e.g. soft ticks) include species responsible for the transmission of pathogens and bacteria, thus representing a health problem not only for wild species that are directly parasitized, but also for those that share the same environments or reproductive sites with them. In this regard, artificial nests for birds may turn out to be site-sources of parasites. Here, we document the occurrence of different life stages of Argas persicus ticks in nest boxes of wild birds in a natural area (not associated with poultry activities) of central coastal Italy (Maremma Regional Park, Tuscany). Between 2018 and 2022, 168 ticks were collected from nest boxes occupied by different secondary cavity-nesting birds, such as European rollers Coracias garrulus and scops owl Otus scops. Ticks were analysed morphologically, and selected specimens were also identified by mitochondrial ribosomal 16S (16S) subunit gene to ascertain their taxonomic status. All ticks were identified as Argas persicus. This finding not only suggests that this tick species has formed a viable population in this Italian region, but also further confirms the previously doubtful natural origin of the species at country level and sheds new light on its underestimated and little investigated distribution. Possible pathways of introduction and its potential impacts on local avian community are discussed.

Occupation rates of artificial nest boxes by secondary cavity-nesting birds: The influence of nest site characteristics

Artificial nest boxes may increase the abundance of nest sites for secondary cavity-nesting birds and provide more breeding opportunities. Since birds have strong preferences for certain characteristics of nest boxes, careful selection of installation sites can improve the occupancy rate of nest boxes and enhance reproduction. From 2016 to 2019, we studied the parameters affecting birds’ occupation of nest boxes in Xianrendong National Nature Reserve in Liaoning, northeast China. Among 241 nest boxes, five were occupied continuously for 4 years (1.6%), 42 for 3 years (17.4%), 69 for 2 years (28.6%) and 88 for 1 year (36.5%), with 37 (15.3%) never being occupied for 4 years. The birds using the nest boxes were mainly cinereous tits (Parus cinereus), varied tits (Sittiparus varius), marsh tits (Poecile palustris), and Eurasian nuthatches (Sitta europaea). Our results showed that the occupation rates were positively correlated with nest box height, nest openness and proportion of conifers. Tree or pole that nestboxes are attached to also had a significant effect on occupation rates, and nest boxes hanging on conifer trees were occupied more often than those on deciduous trees and wooden telegraph poles. Breeding performance was not affected by occupation rates. These findings demonstrate that nest boxes should be hung high on a coniferous tree located in woodland with a higher ratio of conifers and open space in front of the nest when hanging nest boxes to attract small cavity-nesting birds.

Experimental playback of natural gas compressor noise reduces incubation time and hatching success in two secondary cavity-nesting bird species

Abstract Natural gas compressor stations emit loud, low-frequency noise that travels hundreds of meters into undisturbed habitat. We used experimental playback of natural gas compressor noise to determine whether and how noise influenced settlement decisions and reproductive output as well as when in the nesting cycle birds were most affected by compressor noise. We established 80 nest boxes to attract Eastern Bluebirds (Sialia sialis) and Tree Swallows (Tachycineta bicolor) to locations where they had not previously nested and experimentally introduced shale gas compressor noise to half the boxes while the other 40 boxes served as controls. Our experimental design allowed us to control for the confounding effects of both physical changes to the environment associated with compressor stations as well as site tenacity or the tendency for birds to return to the specific locations where they had previously bred. We incorporated behavioral observations with video cameras placed within boxes to determine how changes in behavior might lead to any noted changes in fitness. Neither species demonstrated a preference for box type (quiet or noisy), and there was no difference in clutch size between box types. In both species, we observed a reduction in incubation time, hatching success, and fledging success (proportion of all eggs that fledged) between quiet and noisy boxes but no difference in provisioning rates. Nest success (probability of fledging at least one young; calculated from all nests that were initiated) was not affected by noise in either species suggesting that noise did not increase rates of either depredation or abandonment but instead negatively impacted fitness through reduced hatching and fledging success. Compressor noise caused behavioral changes that led to reduced reproductive success; for Eastern Bluebirds and Tree Swallows, gas infrastructure can create an equal-preference ecological trap where birds do not distinguish between lower and higher quality territories even when they incur fitness costs.

An assessment of the availability of cavities for secondary cavity-nesting birds in certified and conventionally-logged Neotropical rainforests

The high level of forest intervention and the decrease in biodiversity as a result of logging are incentives to implement forest certification schemes. Despite the advances in the results of the impact of forest certification on biodiversity, there are few studies on species with specific habits, such as cavity-nesting birds. The objective of this study is to compare the impact of forest certification and conventional logging on the richness, availability (density) and dominance of potentially suitable cavity trees for secondary cavity-nesting birds in the subtropical forests of northwestern Argentina. Seven sites were selected: three control sites which were not logged for at least 40 years, one site under Forest Stewardship Council (FSC) certification, and three sites with conventional logging. The results suggest that logged forests under FSC-certification may guarantee a diversity, availability (density) and dominance of potentially suitable cavity trees for secondary cavity-nesting birds, as well as certain characteristics (such as DBH > 40 cm), similar to unlogged forests for this group of birds. Therefore, we suggest that the forests of northwestern Argentina should be managed by a scheme under forest certification so that the high levels of cavity tree species are maintained.

Functional diversity of tree cavities for secondary cavity-nesting birds in logged subtropical Piedmont forests of the Andes

Studies about functional ecology have increased in the last years and they are currently an important element for the understanding of ecosystem processes. The aim of this study was to compare different functional traits of cavity trees for secondary cavity-nesting birds, between unlogged (control forest) and conventionally logged sites in subtropical piedmont forests of NW Argentina. Between 10 and 20 plots per site were established and were grouped according to the treatments (control forest and logged forest) for statistical analyses. We measured and defined the following cavity tree traits potentially important for cavity-nesting birds: diameter at breast height (DBH), cavity height, cavity entrance size and cavity internal depth. Besides, abundance and taxonomic richness of cavity tree species were calculated, as well as functional indices: Functional Richness (FRic, amount of functional niche volume filled by cavity tree species in the community), Functional Evenness (FEve, measures the regularity of the distribution of cavity tree species abundances and dissimilarities in functional space), Functional Divergence (FDiv, quantifies how cavity tree species diverge in their abundance-weighted, distances in functional space) and Community-Weighted Mean (CWM, mean of trait values present in the community weighted by the relative abundance of species bearing each value). The main results showed that logged sites (relative to control sites) had: (1) lower abundance and taxonomic richness of cavity trees; (2) lower functional richness; (3) higher functional evenness, which may be due to the uniformity in distribution of the traits of the cavity tree species in space; (4) lower ‘Community-Weighted Mean’ of cavity size, possibly due to the fact that larger cavities need larger tree species and they are the most extracted in logged sites. Understanding how the functional traits of cavity trees are affected may help decision makers to implement sustainable policies for conservation of secondary-cavity user birds, and consequently, of the ecological services they provide.

Forest inventory attributes predict the occurrence of cavities suitable for nesting by Wood Ducks (Aix sponsa)

Large secondary cavity-nesting birds such as waterfowl and raptors rely on tree cavities developed principally through decay and damage processes or excavation by woodpeckers. Forest and wildlife managers are tasked with maintaining and producing these essential habitat components through forest management practices. Predicting where tree cavities are most likely to have developed based on commonly collected forest-inventory data would therefore be useful to better manage important bird species. Wood Ducks (Aix sponsa) are a common and well-studied secondary cavity-nesting species, though until recently, management of nesting habitat has primarily focused on installing artificial nesting structures as opposed to influencing forest-management practices. We measured and inspected 7869 trees and 1186 potential cavities in forests of north-central Minnesota during 2016–2018 to determine their suitability for use by nesting Wood Ducks. Two hundred and twenty-three of the cavities inspected (19%) were classified as suitable for use by nesting Wood Ducks. We fitted logistic regression models using tree- and stand-level forest attributes to predict the probability of an individual tree having at least one suitable cavity. The top model predicted well whether trees had suitable cavities (average area under the received-operated-characteristic curve value of 0.85 [95% CI; 0.82–0.87]) and had an additive relationship among diameter at breast height (DBH), tree health status, and tree species. We also found some support for including an interaction between DBH and health status. For every one-cm increase in DBH, the odds that a given tree would have a suitable cavity increased by 7% (95% CI; 6–9%). Dead and declining trees were more likely to have suitable cavities than healthy trees, with 834% (483–1420%) and 477% (276–807%) higher odds, respectively. In a comparison of seven common deciduous species with cavities, sugar maple (Acer saccharum) and American basswood (Tilia americana) were most likely to have developed cavities. These results can be applied to existing forest-inventory datasets to predict the availability of suitable cavities in the landscape and to improve forest management strategies that benefit Wood Ducks and other large-bodied secondary cavity-nesting species.

Old nest material functions as an informative cue in making nest-site selection decisions in the European Kestrel (Falco tinnunculus)

BackgroundFor secondary cavity-nesting bird species that do not add lining materials to nests, the presence of old nest material or organic remains that have accumulated within nest cavities from previous breeding events may be a cue of nest-site quality. These materials potentially contain information about past breeding success in con- and heterospecifics and may improve the thermal insulation of eggs during incubation. However, few studies have addressed whether the presence of old nest materials serves as a cue for cavity-nesting raptors when choosing specific nest sites.MethodsWe conducted a 9-year nest box experiment to test whether old nest materials from con- and heterospecifics serve as informative cues to the European Kestrel (Falco tinnunculus) when making nest selection decisions, as this species uses nest boxes without adding nesting material.ResultsThe presence of old nest materials and entrance size best discriminated nest boxes occupied by European Kestrels from unoccupied boxes. Nest boxes containing conspecific organic remains, artificial dry leaf and branch material, and material left behind by Great Tits (Parus major) were reused at higher rates, especially those containing conspecific nest material, than nest boxes containing true or simulated nest materials from predators. In 2010, no single nest box was occupied by the same banded individual that occupied the box in the previous year (10 females and 2 males were banded in 2009).ConclusionsEuropean Kestrels preferred nest boxes containing old nest material over empty boxes, which is consistent with previous findings that they exploit con- and heterospecific cues when deciding where to settle and breed, as old nest or organic material provides substrate for incubating females. Kestrels may be able to assess the predation risks associated with a specific nest site based on experience or the presence of prey remains. The repeated use of nest boxes across breeding seasons by kestrels cannot be entirely ascribed to philopatry. This study provides evidence that old nest materials are potentially used as informative cues when making nest-site selection decisions in European Kestrels.

Hole Life: Survival Patterns and Reuse of Cavities Made by the Lesser Spotted Woodpecker Dendrocopos minor

Primary cavity-producers such as woodpeckers produce nest sites for several other cavity-nesting animals and, thus, are often considered to be keystone species. However, the persistence and occupancy rates of cavities are rarely known and as such the real importance of primary cavity-producers also remains unclear. Cavities of the Lesser Spotted Woodpecker Dendrocopos minor were monitored during their whole lifespan. The data include the annual availability and occupancy history of 106 cavities in a 170-km2 area in southern Finland during 1987–2018. The median survival time of a cavity was six years, but there were differences between the various forest types (range six to eight years). The median time for cavity fall was six years, and five years for cavity damage. Six bird species used the old cavities for breeding, with the Pied Flycatcher Ficedula hypoleuca the dominant species accounting for 53% of all occupancies. The cavity reuse rate in the Lesser Spotted Woodpecker was 3.6%. The mean occupancy by secondary cavity-nesting birds in old cavities was 32%, with a range of 29–36% across the various forest types. There was a significant negative correlation between annual occupancy rates and the age of the cavity. The first two years of a cavity were found to be the most important for total occupancy and 90% of occupancies took place before the median age of the cavities. The expected mean number of lifespan occupancies by secondary cavity-nesters for a single cavity was 1.97. The results indicate that new, fresh cavities are continuously needed for the secondary cavity-nesters that use Lesser Spotted Woodpecker cavities in their territories.

Bird services applicable to mine restoration: a case study of Sand Martin (Riparia riparia) burrow construction

Vertical banks in mining sites can provide safe nesting sites for burrowing bird species. These burrows can then, in turn, provide nest sites for species unable to create burrows themselves, especially in areas where the abundance of safe nesting holes is a limiting factor. Thus, primary burrowing species can provide ecosystem services for secondary cavity-nesting species. Our objective was to study the availability of burrows of biotic origin in mining sites, and their role in improving colonization and local biodiversity of cliff-nesting birds (birds that rely primarily on rocky or sandy walls to breed). We selected the Sand Martin because it is a colonial ecological engineer species that nests frequently in mining sites. First, we estimated Sand Martin burrow abundance and occupation rates and identified secondary cavity-nesting birds in 8849 burrows from 30 colonies in ten mining sites in central Spain. Second, we studied the dynamics of the Sand Martin burrows, by estimating annual construction and disappearance rates. Finally, we studied factors that could favour secondary cavity-nesting bird occupation. We found that Sand Martins burrowed more than was previously estimated in mining sites, and that their burrows were used by five species of secondary cavity-nesting birds. The number of available burrows each year varied due to relatively high annual construction and disappearance rates. Numbers of Sand Martin pairs and burrows in the colonies were the main factors favouring secondary cavity occupation. Our results support promoting Sand Martins in mine restoration projects, not only to benefit this endangered bird, but also because their ecosystem services can benefit other cliff-nesting species of birds, thus increasing local biodiversity.

Identification of tree groups used by secondary cavity-nesting birds to simplify forest management in subtropical forests

In tropical and subtropical forest ecosystems, cavities formed by decay processes are a key but scarce resource for birds that nest and roost in them, which makes them a highly sensitive group to logging. The piedmont forest of northwestern Argentina is a complex ecosystem with 113 tree and 120 bird species. It has high logging pressure on the few, well-conserved forest remnants, complicating the delineation of sustainable management guidelines for each tree or bird species in a short time. Our objective was to reduce the complexity of subtropical forests by grouping tree species according to the characteristics used by secondary cavity-nesting birds (i.e. non excavators). In the piedmont forest, 50 plots of 0.25 ha were sampled to record cavity trees and cavity characteristics. These were then used in a cluster analysis to form tree groups. Additionally, cavities were searched to identify the bird species using the decay-formed cavities. A total of 187 cavity trees, comprising 23 tree species, were recorded, and these formed four tree groups or clusters. We recorded 86 cavities that were used by secondary cavity-nesting bird species. The four tree groups were unequally used by secondary cavity nesters. The tree group that included valuable timber species (Myroxylon peruiferum, Anadenanthera colubrina and Calycophyllum multiflorum) and had the greatest cavity availability represented 71% of total cavity use. Another tree group with valuable timber species (Cedrela balansae and Amburana cearensis), measured > 73 cm DBH and > 21 m tall, had cavity entrances > 0.10 cm2, and contributed 14% of all cavity use by birds. A third group had no highly economically valuable tree species, and included the snag category (i.e. standing dead trees) as well as a 15% of cavity use. The fourth tree group had a DBH < 0.40 cm, only one highly economically valuable tree species (Cordia trichotoma), and supported no cavity use. The clustering of subtropical trees can reduce the complexity of these forests, hence easing their management by focusing on those groups with tree species showing similar characteristics and providing suitable nesting sites for secondary cavity-nesting birds.

Additional information on reproductive behavior of the Red-breasted Toucan, Ramphastos dicolorus (Aves: Piciformes: Ramphastidae)

Abstract: Ramphastidae is Family of secondary cavity-nesting birds that is endemic to the Neotropical region. Here we provide a comprehensive literature review of nest measurements, and new information on characteristics of the nest cavity, parental nest attendance, incubation and nestling period of the Red-breasted Toucan, Ramphastos dicolorus. We also add information on the origin of the seeds found inside toucan nests and propose a potential function for them. Eight nests were studied in three cavities during six breeding seasons at Parque Estadual das Fontes do Ipiranga, São Paulo, and at a private allotment in Ibiúna, southeastern Brazil. The reproductive activities of the birds were observed from September to February. In one cavity, we found the first record of a Meliponini bee hive (Scaptotrigona bipunctata) co-existing with a toucan nest. At the beginning of the nesting season, the parents regurgitate seeds on the floor of the cavity, covering it with them. This preparation plays a role in nest sanitation, once the seeds act as a substrate for the feces facilitating the process of carrying them off the nest by the female. The incubation and nestling periods lasted 17.2 ± 1.2 and 43 ± 5.4 days, respectively, and both parents shared egg incubation, nestling, brooding and provisioning, but only the female performed nest sanitation. This differs from published observations on other species of the group, suggesting that the participation of each sex in nest attendance may not be the same for all ramphastids. Additionally, our observations suggest that selecting anthropic locations for nesting can negatively influence toucan nest success.

Effects of Experimental Anthropogenic Noise Exposure on the Reproductive Success of Secondary Cavity Nesting Birds.

Artificial nest boxes are critical nesting sites for secondary cavity-nesting birds; however, they are often placed near roadways and in urban areas that experience noise pollution and other human-caused stressors. Recent correlative studies document both negative and positive influences of noise pollution on reproductive success. Additionally, observational studies have not determined which stage of the breeding process is most vulnerable to noise pollution-settlement, incubation, and/or provisioning. Here, we controlled for possible effects from non-random settlement and eliminated potential effects of roadways, such as collisions and chemical and light pollution, by experimentally introducing traffic noise into nest boxes after clutch initiation in two secondary-cavity nesting bird species. We found no evidence for an influence of noise on clutch size, brood size, number of fledglings, or overall nest success in western bluebirds (Sialia mexicana). In contrast, we found that ash-throated flycatcher (Myiarchus cinerascens) nests exposed to noise had lower reproductive success than quiet nests due to higher rates of abandonment at the incubation stage. Our results match recent research demonstrating that ash-throated flycatchers avoid energy-sector noise in their nest placement and, when they do nest in noise, experience stress hormone dysregulation and fitness costs. The lack of a response among western bluebirds differs from reported declines in reproductive success due to exposure to energy-sector noise; however, the absence of a response matches the response seen in other species using an in-box noise playback experiment. These results suggest that in-box noise exposure experiments may be appropriate for assessing noise impacts at the nest, and through some pathways (e.g., direct effects of noise on nestlings), but do not capture other ways in which noise can negatively affect birds during the breeding season that may ultimately cause declines in fitness. Additionally, although manipulative experiments that examine the influence of a single anthropogenic stressor on a single life stage can help reveal causal pathways, urban and other human-dominated environments are characterized by many stressors and future studies should seek to understand how noise interacts with other stressors to impact birds and other wildlife. Finally, in light of mounting evidence demonstrating declines in reproductive success due to noise, our results suggest that nest box placement near roads may be counterproductive to efforts to bolster population densities of some species.

How Important are Nest Cavities Made by the Three-Toed Woodpecker Picoides tridactylus for Cavity-Nesting Forest Bird Species?

Woodpeckers are important primary excavators that produce nest-sites that are also used by several other cavity-nesting animals. However, the value of nest sites produced by different woodpecker species for other cavity-nesters is not generally known. We studied old Three-toed Woodpecker Picoides tridactylus cavities to examine their importance for other cavity-nesting forest bird species. Over a 31-year period (1987–2017), we annually monitored the occupancy of 655 cavities excavated by the Three-toed Woodpecker in 86 territories of the species in a 170-km2 area in southern Finland. Eight bird species used old Three-toed Woodpecker cavities for breeding, and the occupancy of these cavities by all secondary users was 21.3%. The expected mean number of lifetime occupancies by secondary cavity-nesters for a single cavity was 2.03. This is equivalent to a mean of two cavities occupied per territory per year, if we assume that Three-toed Woodpeckers produce a new cavity every year. The actual numbers of annually occupied cavities by secondary cavity-nesters can be substantially lower especially in territories that are not constantly occupied by the Threetoed Woodpecker. Based on the use of old cavities and densities of secondary cavity-nesting bird species, we conclude that cavities made by Three-toed Woodpeckers are most significant for the species itself, which accounted for 23.3% of nests in old Three-toed Woodpecker cavities. When Three-toed Woodpeckers reused an old cavity rather than occupy a freshly excavated cavity, 93% of cavities selected were originally excavated by Three-toed Woodpeckers. In addition, old cavities are important for the Pygmy Owl Glaucidium passerinum — up to 26–31% of breeding attempts were in old Three-toed Woodpecker cavities. The importance of old cavities for other hole-nesting bird species like the Pied Flycatcher Ficedula hypoleuca or the Great Tit Parus major was rather minor considering their densities within woodpecker territories.

Sequential Use of Tree Cavities by Birds and Nest Web in a Riparian Forest in Southwest India

We studied the sequential use of tree cavities by the cavity-nesting bird community in a riparian forest ecosystem of south-western India during 2013–2015. During the study period, a total of 376 nests of 20 cavity-nesting bird species comprising six primary and 14 secondary cavity nesters were located in the riparian forest. The cavity use pattern showed that one-third of the cavities were reused by birds and that the majority of the reused cavities were located in live trees. A lesser proportion (5%) of cavities used by birds was reused by other animal taxa. Competition for nest cavity use was observed among bird species in which Common Myna Acridotheres tristis was found to be the major competitor. A strong correlation was found between the bird body mass and nest cavity dimensions. Cluster analysis based on tree and cavity characteristics divided the avian community into five groups. We constructed a nest web for community structure that showed cavity resource use by various primary and secondary cavity-nesters. Woodpeckers (Greater Golden-backed Woodpecker Chrysocolaptes guttacristatus, White-naped Woodpecker C. festivus, and Browncapped Pygmy Woodpecker Dendrocopos nanus) as well as barbets (Brown-headed Barbet Psilopogon zeylanica, Coppersmith Barbet P. haemacephala and White-cheeked Barbet P. viridis) formed the key excavators in the riparian forest. While many of the smaller secondary cavity-nesting birds depend on the excavated cavities for nesting and reproduction, large-sized birds used decay formed cavities.

Home, dirty home: effect of old nest material on nest-site selection and breeding performance in a cavity-nesting raptor.

The quality of a breeding site may have major fitness consequences. A fundamental step to understanding the process of nest-site selection is the identification of the information individuals use to choose high-quality nest sites. For secondary cavity-nesting bird species that do not add nest lining material, organic remains (faeces, pellets) accumulated inside nest cavities during previous breeding events may be a cue for high-quality nest-sites, as they contain information about past successful breeding and may improve thermal insulation of eggs during incubation. However, cavities in which breeding was successful might also contain more nest-dwelling ectoparasites than unoccupied cavities, offering an incentive for prospective parents to avoid them. We exposed breeding cavity-nesting lesser kestrels (Falco naumanni) to nestbox dyads consisting of a dirty (with a thick layer of organic substrate) and a clean nestbox (without organic material). Dirty nestboxes were strongly preferred, being occupied earlier and more frequently than clean ones. Hatching success in dirty nestboxes was significantly higher than in clean ones, suggesting a positive effect of organic nest material on incubation efficiency, while nestbox dirtiness did not significantly affect clutch and brood size. Nestlings from dirty nestboxes had significantly higher ectoparasite load than those from clean nestboxes soon after egg hatching, but this difference was not evident a few days later. Nest substrate did not significantly affect nestling growth. We concluded that nest substrate is a key driver of nest-site choice in lesser kestrels, although the adaptive value of such a strong preference appears elusive and may be context-dependent.

Chronic anthropogenic noise disrupts glucocorticoid signaling and has multiple effects on fitness in an avian community

Anthropogenic noise is a pervasive pollutant that decreases environmental quality by disrupting a suite of behaviors vital to perception and communication. However, even within populations of noise-sensitive species, individuals still select breeding sites located within areas exposed to high noise levels, with largely unknown physiological and fitness consequences. We use a study system in the natural gas fields of northern New Mexico to test the prediction that exposure to noise causes glucocorticoid-signaling dysfunction and decreases fitness in a community of secondary cavity-nesting birds. In accordance with these predictions, and across all species, we find strong support for noise exposure decreasing baseline corticosterone in adults and nestlings and, conversely, increasing acute stressor-induced corticosterone in nestlings. We also document fitness consequences with increased noise in the form of reduced hatching success in the western bluebird (Sialia mexicana), the species most likely to nest in noisiest environments. Nestlings of all three species exhibited accelerated growth of both feathers and body size at intermediate noise amplitudes compared with lower or higher amplitudes. Our results are consistent with recent experimental laboratory studies and show that noise functions as a chronic, inescapable stressor. Anthropogenic noise likely impairs environmental risk perception by species relying on acoustic cues and ultimately leads to impacts on fitness. Our work, when taken together with recent efforts to document noise across the landscape, implies potential widespread, noise-induced chronic stress coupled with reduced fitness for many species reliant on acoustic cues.

Interpopulation variation in nest architecture in a secondary cavity-nesting bird suggests site-specific strategies to cope with heat loss and humidity

ABSTRACT Nest morphology can affect the breeding success of birds. Thus, birds inhabiting different environments may experience divergent selection for nest structure and composition that results in intraspecific geographic variation in nest architecture. We describe interpopulation differences in nest architecture among Thorn-tailed Rayaditos (Aphrastura spinicauda) in 2 contrasting environments near the species' distribution limits: a temperate and very humid environment in north-central Chile (the forest relicts of Fray Jorge National Park; 30°38′S, 71°40′W) and a cold and windy sub-Antarctic environment in the south of Chile (Isla Navarino; 55°4′S, 67°40′W). We collected a total of 62 nests from Fray Jorge and 61 nests from Navarino in 2013 and 2014, measured their dimensions, and quantified their constitutive materials. We tested the nests' thermal properties (simulating heat loss by convection and conduction) and hygroscopic features (water absorption and water loss capacity) and used general linear...

Sound settlement: noise surpasses land cover in explaining breeding habitat selection of secondary cavity-nesting birds.

Birds breeding in heterogeneous landscapes select nest sites by cueing in on a variety of factors from landscape features and social information to the presence of natural enemies. We focus on determining the relative impact of anthropogenic noise on nest site occupancy, compared to amount of forest cover, which is known to strongly influence the selection process. We examine chronic, industrial noise from natural gas wells directly measured at the nest box as well as site-averaged noise, using a well-established field experimental system in northwestern New Mexico. We hypothesized that high levels of noise, both at the nest site and in the environment, would decrease nest box occupancy. We set up nest boxes using a geospatially paired control and experimental site design and analyzed four years of occupancy data from four secondary cavity-nesting birds common to the Colorado Plateau. We found different effects of noise and landscape features depending on species, with strong effects of noise observed in breeding habitat selection of Myiarchus cinerascens, the Ash-throated Flycatcher, and Sialia currucoides, the Mountain Bluebird. In contrast, the amount of forest cover less frequently explained habitat selection for those species or had a smaller standardized effect than the acoustic environment. Although forest cover characterization and management is commonly employed by natural resource managers, our results show that characterizing andmanaging the acoustic environment should be an important tool in protected area management.