Nest Searches Research Articles

Breeding biology of Great White Pelican Pelecanus onocrotalus at Lake Tana, Ethiopia

Great White Pelicans, once thriving at Lake Shala, have faced a decline in breeding pairs at Lake Abijata due to increased salinity and overfishing. A study at Lake Tana Biosphere, from December 2020 to December 2021, aimed to understand their breeding biology, which had not been previously documented. We conducted intensive searches for nests and monitored them during incubation and post-hatching to assess reproductive success. The study found pelicans breed year-round, with peaks from late December to March and June to July. The average clutch size was 2.14, with egg dimensions averaging 90.33 mm in length and 58.70 mm in breadth and a mean weight of 173.68 g. No significant differences were observed in these measurements, but a positive correlation was found between egg length, weight, and breadth and weight. However, no correlation existed between length and breadth. Out of 98 eggs, 84 hatched, resulting in 80 and 91.5 % hatchability rates across two breeding seasons, averaging 85.71 %. The hatching success rate did not differ significantly between seasons. Unfortunately, only 37 pelicans reached the pre-fledging stage, indicating a high mortality rate of 63 %. The study concluded that the breeding performance of Great White Pelicans at Lake Tana is poor, with human disturbance, overfishing, and predation on nestlings posing significant threats to their nesting success. This highlights the need for conservation efforts to address these challenges and protect the species.

Geometrical multiscale tortuosity of desert ant walking trajectories.

Desert ants stand out as some of the most intriguing insect navigators, having captured the attention of scientists for decades. This includes the structure of walking trajectories during goal approach and search behaviour for the nest and familiar feeding sites. In the present study, we analysed such trajectories with regard to changes in walking direction. The directional change of the ants was quantified, i.e. an angle θ between trajectory increments of a given arclength λ was computed. This was done for different length scales λ, according to our goal of analysing desert ant path characteristics with respect to length scale. First, varying λ through more than two orders of magnitude demonstrated Brownian motion characteristics typical of the random walk component of search behaviour. Unexpectedly, this random walk component was also present in - supposedly rather linear - approach trajectories. Second, there were small but notable deviations from a uniform angle distribution that is characteristic of random walks. This was true for specific search situations, mostly close to the (virtual) goal position. And third, experience with a feeder position resulted in straighter approaches and more focused searches, which was also true for nest searches, albeit to a lesser extent. Taken together, these results both verify and extend previous studies on desert ant path characteristics. Of particular interest are the ubiquitous Brownian motion signatures and specific deviations thereof close to the goal position, indicative of unexpectedly structured search behaviour.

О формировании городской популяции вяхиря (Columba palumbus L.) в г. Орле

To date, the Woodpigeon has formed specialized urban populations in many European cities and towns. A steady trend towards synanthropization is also observed for this species in some Russian urban areas. In the city of Oryol, no dedicated studies of the local urban Woodpigeon population have been carried out until recently. This paper aims to evaluate the status of the urban Woodpigeon population in Oryol. The field observations were made in the city of Oryol (52°58′ N, 36°05′ E) located in the Central Federal District of the Russian Federation and having an area of 121.2 km2 , with a population of 303.7 thousand and distance from Moscow of 368 km. The studies began in 2006, at the moment when the urban population of the Woodpigeon started to form within the Oryol administrative borders, and ended in 2021. In June 2019 and July 2021, counts of singing individuals and nest search activities were carried out in forest and recreational parks, squares, cemeteries, on specially selected plots among individual houses, and in green residential areas with predominantly five-storied apartment buildings. In total, 26 census plots with an aggregate area of about 228.9 ha were surveyed. Associated observations were also made, including Woodpigeon nest search in all administrative districts of the city. The degree of introduction of the Woodpigeon into the Oryol urban landscapes was evaluated by the use of five synanthropization stages (from 0 to 4). The paper shows that the urban population of the Woodpigeon in Oryol, as it was the case in other European urban areas, started from the birds which began to nest at the urban periphery, in less transformed habitats, and is dated back to 2006. Afterwards the birds were reported breeding in the built-up part of the city, including the city center, with the first breeding case in the built-up part reported in 2016. The number of nests found in the built-up part of the city grew in the following years. Now the birds nest across the entire city, including its central part, where their nests are found both along highways with intense traffic and in yards in residential areas with predominantly fivestoried apartment buildings. The species is registered as breeding in forest and recreational parks, cemeteries, among individual houses and in green residential areas. The average population density in the said habitats ranges from 0.5 to 1.5 pairs/10 ha, with the average for the entire city being 0.8 pairs/10 ha. The highest population density is registered in cemeteries (1.5 pairs/10 ha) and forest parks (1.1 pairs/10 ha). The population density in green residential areas with predominantly five-storied apartment buildings is 0.9 pairs/10 ha (see Table 1). In general, the Woodpigeon population in Oryol is much smaller than in many other urban areas in Europe and in Northwest Africa (see Table 2), which is attributed to the longer history of urban populations there. All nests found were located on trees and bushes, with none found on man-made structures. The high numbers of the Hooded Crow are among the factors hindering colonization of urban habitats by the Woodpigeon in European cities and towns. At the same time, the Hooded Crow is an uncommon breeder in Oryol. The Magpie, another nest predator, is a rather common breeder in the city: its breeding density was 2.2 nests/10 ha in green residential areas and 1.5 nests/10 ha among individual houses. Urban-breeding Woodpigeon aggregations generally make long-distance foraging movements to nearby farmlands where the birds obtain additional food. The agroclimatic conditions of Orlovsky District, which surrounds the city, are characterized as the most attractive for crop cultivation. Thus, the low numbers of the Hooded Crow and presence of large areas occupied by grain crops around the city make up favorable conditions for the establishment of an urban population of the Woodpigeon in Oryol. The urban Woodpigeon population in Oryol is at the stage 3 – breeding in urban parks in a high density and regular breeding in residential areas (on residential streets). The population under study has not yet reached the synanthropization stage 4, when the species breeds in a high density in urban parks and residential areas, with individual pairs transitioning to breeding on man-made structures.

Культ орла в мифологии хангаласцев

Культ орла в мифологии хангаласцев

Орел-могильник в Республике Татарстан — продолжение исследований

Орел-могильник в Республике Татарстан — продолжение исследований

Vespas Sociais (Vespidae: Polistinae) do Instituto Inhotim, Minas Gerais, Brasil

Due to the great loss of insect diversity the world has been suffering, inventorying existing species can provide us with insights for future studies on conservation of functional groups. The objective of this work is to contribute with knowledge of the social wasp fauna of Minas Gerais, by determining the species of the visitation area of the Inhotim Institute, Minas Gerais, Brazil. Through active search for nests, 49 colonies of 16 species and nine genera were recorded.

Ring‐necked pheasant nest site selection in a landscape with high adoption of fall‐seeded cover crops

AbstractGrasslands provide important nesting cover for ring‐necked pheasants (Phasianus colchicus), but they have been largely reduced with intensification of row‐cropping systems, resulting in population declines for pheasants and other grassland birds across the U.S. Row‐crop intensification and landscape homogenization has had negative impacts on environmental health, and agronomic practices such as fall‐seeded cover crops seek to ameliorate some of the environmental issues. Whether fall‐seeded cover crops provide additional benefits to wildlife, such as creating nesting cover for pheasants, remains unknown. We used radio telemetry and nest searches in 365, 0.4‐ha² plots during summer of 2019 and 2020 in 3 cover types including fall‐seeded cover crops, native warm season grasses, and cool season grasses to examine nest site selection by pheasants in the agricultural dominated landscape of Washington County, Iowa. We examined nest site selection at 3 spatial scales based on cover type and specific vegetation attributes to understand factors influencing nest site selection. Highest nest densities were found in native warm season grass (0.59 nests/ha, 95% CI = 0.41–0.86), while pheasants nested at low densities in cool season grass fields (0.03 nests/ha, 95% CI = 0.00–0.21) and cover crop fields (0.03 nests/ha, 95% CI = 0.01–0.12). Most nest‐site selection occurred at the landscape level (second order) and patch level (third order) and was influenced by percent litter cover (second order) and visual obstruction or vegetation density (third order). Our findings suggest that cover crops may make minor improvements in nesting cover availability but are unlikely to replicate the needs for nesting cover provided by perennial grasslands in working landscapes and thus have little potential to reverse long‐term population declines.

Golden Eagle Nesting Territory Distribution in Wind Energy Landscapes of the Southern Great Plains

Abstract Deaths of four Golden Eagles (Aquila chrysaetos) due to collision trauma at a new wind energy facility in east-central New Mexico during 2004–2005 prompted concerns about the species' population status in the encompassing Southern Great Plains region, primarily because its breeding distribution there was poorly documented and wind energy development was expanding rapidly. Therefore, we conducted aerial searches for Golden Eagle nests across northeastern New Mexico, northwestern Texas, western Oklahoma, and adjacent portions of Colorado and Kansas during 2006–2009 and 2015–2020. We delineated five Golden Eagle Nest Search Areas (NSAs) with unique physiographic/geological origins. Individual NSAs were searched partially or entirely for up to 8 yr. Collectively, we identified 123 nesting territories (NTs) occupied by Golden Eagles ≥ 1 yr, of which 94 (76%) were in northeastern New Mexico. The most NTs (40) were in the 11,720-km2 Highlands NSA. Greatest NT density (126.6 km2/NT) and shortest NT nearest neighbor distance (7.4 km) were in the 3533-km2 Northern Caprock NSA. Wind turbines existed near (within 3.2 km) eight nests distributed among five of 28 NTs in the Northern Caprock and were planned for sites in two occupied NTs. Elsewhere, only potential turbines were near nests and only within six NTs. The number of nesting territories we found underscores the importance of the Southern Great Plains to Golden Eagles, even though this region lies at the eastern margin of the species' western North American breeding range. Our data provide strong support for protecting breeding habitat from potential threats, particularly those posed by wind energy development, and are also a foundation for long-term population monitoring.

Nesting Of Montezuma Quail In Mexico

Although Mexico has the greatest diversity of quail of any New World country, basic information on the ecology and life history of Mexican quails remains unknown. Our objective was to describe nest characteristics of the Montezuma quail (Cyrtonyx montezumae montezumae) in central Mexico. We searched for Montezuma quail nests within 8 counties in the state of México, Mexico during May–September 2003. We conducted nest searches along 66 transects (3–5 km × 40 m) distributed across 17 study sites. We recorded vegetation community, elevation, and nesting substrate for each nest. We measured nest characteristics: height, depth, nest entrance diameter, and orientation. If eggs were found, we recorded clutch size and egg mass, texture, color, and shape. We observed 324 quail and located 6 nests along a 254-km route. Nests were located at elevations ranging from 2,568–2,692 m above sea level. Mean (± standard deviation) nest height and depth were 122.2 ± 7.7 mm and 195 ± 61.8 mm, respectively. Nest entrance orientation for 5 of 6 nests was toward a southerly direction. Mean nest egg mass was 9.9 ± 0.1 g. Our study provides basic and descriptive information on a poorly known quail species in Mexico.

Decision-making at the time of parasitism: cowbirds prefer to peck eggs with weaker shells.

Interspecific avian brood parasites, like cuckoos and cowbirds, lay their eggs in nests of other species, the hosts, which take over the entire parental care of the parasite's eggs and chicks. This breeding strategy requires decisions that may affect the parasite's reproductive success. During the breeding season, cowbirds search for host nests and revisit them to monitor its progress and parasitize at the time host laying begins. When visiting hosts nests, they repeatedly peck the nest contents trying to destroy one or more eggs. This behaviour favours parasite's offspring by reducing the competition for food with nestmates. We evaluated if the egg-pecking behaviour of female shiny (Molothrus bonariensis) and screaming (M. rufoaxillaris) cowbirds is affected by the strength and the size of the eggs they find in the nest. We presented to wild-caught females artificial clutches with two natural eggs that differ in size and shell strength. We found that female shiny and screaming cowbirds adjusted egg-pecking behaviour based on the strength but not on the size of the eggs. When differences in strength between eggs were high, both cowbird species pecked more frequently the egg with the weaker shell, increasing the probability of a successful puncture. Our results indicate that female cowbirds can discriminate eggs through the strength of the shell, and by choosing the weaker egg to peck, they increase the probability of puncturing.

Contrasting effects of land cover on nesting habitat use and reproductive output for bumble bees

AbstractUnderstanding habitat quality is central to understanding the distributions of species on the landscape, as well as to conserving and restoring at‐risk species. Although it is well known that many species require different resources throughout their life cycles, pollinator conservation efforts focus almost exclusively on forage resources. In this study, we evaluate nesting habitat for bumble bees by locating nests directly on the landscape. We compared colony density and colony reproductive output for Bombus impatiens, the common eastern bumble bee, across three different land cover types (hay fields, meadows, and forests). We also assessed nesting habitat associations for all Bombus nests located during surveys to tease apart species‐specific patterns of habitat use. We found that B. impatiens nested under the ground in two natural land cover types, forests, and meadows, but found no B. impatiens nests in hay fields. Though B. impatiens nested at similar densities in both meadows and forests, colonies in forests had much higher reproductive output. In contrast, B. griseocollis tended to nest on the surface of the ground and was almost always found in meadows. B. perplexis was the only species to nest in all three habitat types, including hay fields. For some bumble bee species in this system, meadows, the habitat type with abundant forage resources, may be sufficient to maintain them throughout their life cycles. However, B. impatiens might benefit from heterogeneous landscapes with forests and meadows. Results for B. impatiens emphasize the longstanding notion that habitat use is not always positively correlated with habitat quality (as measured by reproductive output). Our results also show that habitat selection by bumble bees at one spatial scale may be influenced by resources at other scales. Finally, we demonstrate the feasibility of direct nest searches for understanding bumble bee distribution and ecology.

Low reproductive success of the endangered Iberá Seedeater in its only known breeding site, the Iberá Wetlands, Argentina

Abstract Subtropical grasslands are highly susceptible to habitat conversion and number among South America’s most threatened ecosystems. The grasslands of northeastern Argentina have been identified as a priority conservation area for threatened capuchino seedeaters because they constitute the main breeding area of these migratory birds. The Iberá Seedeater (Sporophila iberaensis) is a newly described species in the Iberá Wetlands in Argentina whose biology is still poorly understood. The endangered species inhabits grasslands but has only been reported to breed in the Iberá Wetlands ecoregion of northeastern Argentina. To explore the species’ association with grassland vegetation, we studied the breeding biology (clutch size, hatching success, and fledgling production) of the Iberá Seedeater and the main parameters that influence nest survival and nest-site selection. We conducted nest searches and banded adults and nestlings in Iberá National Park during the breeding seasons of 2016–2018. The breeding season of the Iberá Seedeater was highly synchronous and the cumulative probability of nest survival was 0.16. The daily nest survival rate decreased as the breeding season advanced, survival was lower for nests supported by Rhynchospora corymbosa than Paspalum durifolium, the two main nest substrates, and the main causes of nest failure were nest predation and strong winds. Additionally, the population exhibited male-biased site fidelity and a low female return rate. In contrast to other capuchinos, whose breeding biology is associated with upland grasslands, the Iberá Seedeater nested exclusively in flooded lowland grasslands on marsh plants. Thus, effective lowland grassland management is key to maintain the vegetation structure required for reproduction in the Iberá Seedeater.

Classification and feature analysis of the Human Connectome Project dataset for differentiating between males and females

We analysed features relevant for differentiation between males and females based on the data available from the Human Connectome Project (HCP) S1200 dataset. We used 354 features containing cognitive and emotional measures as well as measures derived from task functional magnetic resonance imaging (MRI) and structural brain MRI. The paper presents a thorough analysis of this extensive set of features using a machine learning approach with a goal of identifying features that have the ability to differentiate between males and females. We used two state of the art classification algorithms with different properties: support vector machine (SVM) and random forest classifier (RFC). For each classifier the hyperparameters were obtained and classifiers were optimized using nested cross validation and grid search. This resulted in the classification performance of 91% and 89% accuracy using SVM and RFC, respectively. Using SHAP (SHapley Additive exPlanations) method we obtained relevance of features as indicators of sex differences and identified features with high discriminative power for sex classification. The majority of top features were brain morphological measures, and only a small proportion were features related to cognitive performance. Our results demonstrate the importance and advantages of using a machine learning approach when analysing sex differences.

Habitat modelling locates nesting areas of the Endangered Black-capped Petrel Pterodroma hasitata on Hispaniola and identifies habitat loss

SummaryThe Black-capped Petrel or Diablotin Pterodroma hasitata has a fragmented and declining population estimated at c.1,000 breeding pairs. On land, the species nests underground in steep ravines with dense understorey vegetation. The only confirmed breeding sites are located in the mountain ranges of Hispaniola in the Caribbean, where habitat loss and degradation are continuing threats. Other nesting populations may still remain undiscovered but, to locate them, laborious in situ nest searches must be conducted over expansive geographical areas. To focus nest-search efforts more efficiently, we analysed the environmental characteristics of Black-capped Petrel nesting habitat and modeled suitable habitat on Hispaniola using openly available environmental datasets. We used a univariate generalized linear model to compare the habitat characteristics of active Black-capped Petrel nests sites with those of potentially available sites (i.e. random pseudo-absences). Elevation, distance to coast, and the influence of tree cover and density emerged as important environmental variables. We then applied multivariate generalized linear models to these environmental variables that showed a significant relationship with petrel nesting activity. We used the top performing model of habitat suitability model to create maps of predicted suitability for Hispaniola. In addition to areas of known petrel activity, the model identified possible nesting areas for Black-capped Petrels in habitats not previously considered suitable. Based on model results, we estimated the total area of predicted suitable nesting habitat for Black-capped Petrels on Hispaniola and found that forest loss due to hurricanes, forest fires, and encroachment from agriculture had severely decreased availability of predicted suitable habitat between 2000 and 2018.

Primeros datos sobre la distribución, tamaño poblacional y reproducción del picamaderos negro Dryocopus martius (Linnaeus, 1758) en un área del País Vasco de reciente colonización

espanolLa distribucion del picamaderos negro en la peninsula Iberica ha experimentado recientemente una expansion que ha dado lugar a la coalescencia de sus poblaciones cantabrica y pirenaica. El presente estudio analiza la distribucion de la especie y realiza una estima de su abundancia en una de las zonas de contacto recientemente colonizadas. Asimismo, este trabajo aporta informacion sobre sus preferencias ecologicas a nivel regional. Para ello se recopilaron las citas de los ultimos anos y se realizaron itinerarios de censo, asi como una busqueda intensiva de nidos durante la primavera de 2019. Tambien se analizo la tipologia forestal en el entorno de los nidos, las caracteristicas de los arboles-nido y la productividad media. Se registraron 375 citas repartidas por gran parte del area de estudio, estimandose un minimo de 50 territorios. Se observo que la cobertura de pino, haya y roble americano en torno a los nidos fue mayor que la esperada mientras que fue menor la de eucalipto, encina y bosque de ribera. Como arbol-nido utilizaron ejemplares de haya, pino de Monterrey, pino maritimo y roble americano, emplazados en parcelas de estos tipos de arbolado. Tambien utilizaron eucaliptos viejos que crecian en repoblaciones de coniferas. El exito de cria fue elevado (80%) pero la tasa media de pollos volados (2,1) fue inferior a la media observada en otras regiones europeas. Se concluye que las coniferas estan jugando un importante papel en la colonizacion y que su sustitucion por cultivos de eucaliptos podria limitar el proceso expansivo EnglishThe distribution area of the black woodpecker in the Iberian Peninsula has expanded in recent years, leading to a unification of its Cantabrian and Pyrenean populations. The present study evaluates the distribution of this species and estimates its abundance in one of the recently-colonised contact areas. Likewise, this work provides information on their ecological preferences at a regional level. To this end, records from the last years were compiled and line transects were carried out, as well as an intensive search for nests during the spring of 2019. We also analysed the forest type in the area surrounding the nests, the characteristics of the nest-trees and the average rate of chicks per nest. 375 records were compiled throughout much of the study area, estimating a minimum of 50 territories. It was observed that the coverage of pine, beech and American oak around the nests was greater than expected, while that of eucalyptus, holm oak and riverside forests was lower. The species of nest-trees they used were beech, Monterey pine, maritime pine and American oak, located in areas with the same types of trees. They also used old eucalyptus trees that grew in coniferous plantations. Breeding success was high (80%) but the average rate of fledglings per nest (2.1) was lower than the average observed in other European regions. We conclude that conifers are playing an important role in colonisation and that their replacement by eucalyptus plantations may limit the expansion process. euskaraOkil beltzaren banaketak hedapen handia izan du Iberiar penintsulan berriki, eta horrek kantaurialdeko eta Pirinioetako populazioen bat-egitea eragin du. Ikerketa honek espeziearen banaketa aztertu eta populazioaren tamaina estimatu du. Era berean, lan honek eskualde mailan dituzten lehentasun ekologikoei buruzko informazioa ematen du. Horretarako, azken urteetako aipamenak bildu, trantsektuak egin eta habiak bilatzeko lan intentsiboa egin zen 2019ko udaberrian. Aztertu ziren, halaber, habiaren inguruko basoen tipologia, habietarako zuhaitzen ezaugarriak eta batez besteko txita tasa ere. 375 aipu jaso ziren azterketa eremuan zehar eta gutxienez 50 lurralde estimatu ziren. Ikusi zen habien inguruan pinuen, pagoen eta haritz amerikarren estaldura espero baino handiagoa zela, eta txikiagoa, aldiz, eukalipto, artadi eta ibar-basoena. Habietarako zuhaitz espezie hauek erabili zituzten: pagoa, intsinis pinua, itsas pinua eta haritz amerikarra, zuhaitz mota hauetako lursailetan kokatuak. Konifero landaketetan tartekatuta hazten ziren eukalipto zuhaitz zaharrak ere erabiltzen zituzten. Ugaltze arrakasta handia izan zen (% 80), baina habia bakoitzean txita hegaldatuen batez besteko tasa (2,1) Europako beste eskualde batzuetan ikusitakoa baino txikiagoa zen. Hortaz, ondorioztatu da koniferoek kolonizazioan funtzio garrantzitsua betetzen dutela eta pinudiak eukalipto landaketekin ordezkatzeak hedapen prozesua mugatu egin dezakeela.

Accuracy and spread of nest search behaviour in the Saharan silver ant, Cataglyphis bombycina, and in the salt pan species, Cataglyphis fortis

Desert ants of the genus Cataglyphis are renowned for their navigation abilities, especially for their beeline homing after meandering foraging excursions reaching several hundreds of meters in length. A spiralling nest search is performed when an ant misses the nest entrance upon completing its homebound travel. We examined the nest search behaviours of two desert ant species dwelling in different habitats—Cataglyphis bombycina living in the dunes of the Sahara and Cataglyphis fortis found in the salt pans of North Africa. The two species show distinct differences in walking behaviour. C. bombycina performs a strict tripod gait with pronounced aerial phases, high stride frequencies, and extremely brief ground contact times. In view of these peculiarities and the yielding sand dune substrate, we hypothesised that homing accuracy, and namely distance measurement by stride integration, should be lower in C. bombycina, compared to the well-studied C. fortis with less specialised walking behaviour. We tested this hypothesis in ants’ homebound runs from a feeding site in a linear channel setup. Surprisingly, the accuracies of nest searches were similar in the two ant species, and search accuracy was also independent of the walking substrate, soft dune sand or a hard floor. The spread of the nest search, by contrast, differed significantly between the two species, C. bombycina exhibiting a larger search spread. This may be interpreted as an increased path integration uncertainty due to the above locomotor specialisations, or as a compensation strategy accounting for the silver ants’ particular environmental and behavioural situation.

Depredación de nidos del perico de El Oro Pyrrhura orcesi por el tucanete lomirrojo Aulacorhynchus haematopygus, en la Reserva Buenaventura, Ecuador

La depredación de nidos es considerada uno de los principales factores que regulan las poblaciones de aves. En la actualidad, la información disponible sobre depredación de nidos es amplia, sin embargo, poco se conoce sobre la identidad de los depredadores a nivel mundial. Los eventos documentados de tucanes depredando nidos de la familia Psittacidae, son escasos. Aquí reportamos el primer evento de depredación del tucanete lomirrojo (Aulacorhynchus haematopygus) de nidos del perico de El Oro (Pyrrhura orcesi) en la Reserva Buenaventura, Ecuador. Pyrrhura orcesi es una especie endémica y catalogada en peligro de extinción (EN), únicamente habita una estrecha franja de bosques nublados del suroeste del Ecuador. En el periodo 2002 a 2006, en la Reserva Buenaventura, realizamos búsquedas intensivas de nidos en la época reproductiva y anidación de P. orcesi, y encontramos un total de 12 nidos. El primer nido activo conocido para esta especie lo localizamos en diciembre de 2002, éste fue monitoreado y después de un mes los huevos fueron depredados por una pareja de A. haematopygus. Observamos este tipo de sucesos de depredación en cuatro nidos ubicados en zonas especialmente boscosas de la Reserva Buenaventura, en cambio las cuatro nidadas exitosas se ubicaron en pastos arbolados. A pesar de que el número de nidos que indentificamos no fue representativo, creemos que los nidos ubicados en áreas abiertas arboladas ayudan a evitar la depredación, como sucede con otros psitácidos, aunque esta hipótesis debe ser comprobada. Debido a estos eventos de depredación, en 2007 se colocaron 50 nidos artificiales en pastos arbolados en un área aproximada de 2,000 ha. Esta estrategia permitió incrementar la disponibilidad de cavidades y aumentó el número de grupos anidantes de P. orcesi. Hasta 2019, los nidos artificiales siguen siendo ocupados por P. orcesi y aportan al conocimiento de la biología reproductiva y conservación de esta especie.

Automated auditory detection of a rare, secretive marsh bird with infrequent and acoustically indistinct vocalizations

Autonomous recording units (ARUs) provide a non‐invasive and efficient method for acoustic detection of elusive species across large temporal and spatial scales. However, species with indistinct vocalization structures can be a considerable challenge for automated signal recognizers. We investigated the performance of ARUs and signal recognizers in identifying the broadband, short‐syllable, pulsed calls of a secretive, threatened marsh bird, the King Rail Rallus elegans. Other sympatric species in the same habitat also have repetitive calls within the same frequency range that can be difficult to distinguish. Following serial ARU deployments at specified sites in known breeding habitat, we conducted standardized callback surveys and nest searches to provide an independent measure of breeder density. To analyse recordings, we developed a signal recognizer based on user‐input training files to detect two common call types, kek and grunt. Detections that remained following manual review of recognizer output revealed a previously undescribed seasonal decline and crepuscular diel pattern in calling rate. The rate of the grunt call also predicted density. These patterns emerged despite the recognizer's low precision and high false‐positive rate, which were largely due to misclassification of other species' calls, although ambient noise and effective detection radius also limited the detectability of King Rail calls. We demonstrate that with informed ARU scheduling, improved ability to manipulate user‐specified parameters within signal detection software, and attention to quality control, even the simplest call structures can be located consistently in a diverse acoustic landscape. Our behavioural findings will inform improvements to auditory surveys and to management of King Rails across their range.

Direct and indirect effects of regional and local climatic factors on trophic interactions in the Arctic tundra

Climate change can impact ecosystems by reshaping the dynamics of resource exploitation for predators and their prey. Alterations of these pathways could be especially intense in ecosystems characterized by a simple trophic structure and rapid warming trends, such as in the Arctic. However, quantifying the multiple direct and indirect pathways through which climate change is likely to alter trophic interactions and their relative strength remains a challenge. Here, we aim to identify direct and indirect causal mechanisms driven by climate affecting predator-prey interactions of species sharing a tundra food web. We based our study on relationships between one Arctic predator (Arctic fox) and its two main prey - lemmings (preferred prey) and snow geese (alternate prey) - which are exposed to variable local and regional climatic factors across years. We used a combination of models mapping multiple causal links among key variables derived from a long-term dataset (21years). We obtained several possible scenarios linking regional climate factors (Arctic oscillations) and local temperature and precipitation to the breeding of species. Our results suggest that both regional and local climate factors have direct and indirect impacts on the breeding of foxes and geese. Local climate showed a positive causal link with goose nesting success, while both regional and local climate displayed contrasted effects on the proportion of fox breeding. We found no impact of climate on lemming abundance. We observed positive relationships between lemming, fox and goose reproduction highlighting numerical and functional responses of fox to the variability of lemming abundance. Our study measures causal links and strength of interactions in a food web, quantifying both numerical response of a predator and apparent interactions between its two main prey. These results improve our understanding of the complex effects of climate on predator-prey interactions and our capacity to anticipate food web response to ongoing climate change.

Multimodal cues facilitate nest recognition in carpenter bee aggregations

The advantages of group living are partially offset by the cognitive challenges associated with maintaining social boundaries. These challenges can give rise to recognition mechanisms that adaptively integrate information across multiple sensory modalities. The valley carpenter bee, Xylocopa varipuncta, nests in dead wood in large aggregations of up to several dozen nests. This study investigates the proximate mechanisms by which returning foragers quickly and reliably identify their own nest entrance within a high-density nesting site. We manipulated long- and short-range visual cues associated with nest entrances, removed chemical cues on the inside of nest entrances and added chemical cues from foreign conspecific bees. By measuring the effect of these manipulations on nest search time and search accuracy, we assessed the importance of visual and olfactory sensory modalities in allowing carpenter bees to locate their nests within aggregations. Our results support the hypothesis that both visual and olfactory cues can facilitate nest localization. Removal of nest olfactory cues did not significantly disrupt homing, suggesting that olfactory information may not be necessary for nest localization when visual information is available. However, the addition of olfactory cues from unfamiliar conspecific bees actually aided nest localization rather than disrupting it, suggesting that bees may use generalized species odour cues for homing. Due to intense nest site competition within aggregations, nest localization may have important social implications for maintenance of high-density nesting.