Nest Occupancy Research Articles

Barn owl site occupancy and breeding success in relation to land use and nest box characteristics

AbstractAgricultural landscapes play a crucial role in enhancing biodiversity because of their widespread presence over the Earth and their ability to encompass diverse ecosystems. Recognizing this, numerous governments are incentivizing farmers through direct payments to adopt sustainable practices, such as managing extensive pastures and meadows, planting wildflowers, or establishing hedgerows. However, the benefit of such sustainable practices on vertebrate species is not well understood. From 2018 to 2020, we investigated nest occupancy, fledging success, and clutch size of a Swiss population of barn owls (Tyto alba) with respect to nest box characteristics and the presence of extensive agriculture and urbanization in areas surrounding nest boxes. Our results revealed that extensively used pastures were positively associated with site occupancy but negatively associated with clutch size. The proportion of urban areas was negatively related to both site occupancy and clutch size. The altitude of the nest box location was negatively correlated with occupancy, and the number of nest boxes placed at the same site (either 1 or 2) was positively correlated with site occupancy. Moreover, clutch size, but not fledging success, was larger in nest boxes placed outside barns than in nest boxes placed inside barns. Based on these findings, we recommend installing nest boxes at locations <700 m in altitude and in pairs on the same barn, incorporating biodiversity promotion areas into agricultural landscapes, and avoiding dense urban areas in favor of rural zones with lower urban density. Understanding the nuanced relationships between nest box characteristics, environmental factors, and breeding success provides valuable insights for optimizing artificial nesting sites and enhancing the overall reproductive success of barn owls.

Using a drone to monitoring arboreal nests of birds of prey

ABSTRACT The breeding parameters of birds are the key element of bird population monitoring. The assessment of nesting success is difficult in the case of arboreal nests, which are typical for birds of prey. Drones are valuable tools for monitoring arboreal nest occupancy. We tested the feasibility of safely monitoring the common buzzard Buteo buteo and northern goshawk Accipiter gentilis nests via drones. We compared assessments of nest occupancy and the number of fledglings in occupied nests using drones with those obtained from traditional ground-based observations. Additionally, the response of the raptors to drone appearance was documented. The assessments of the nest occupancy of the common buzzard from the ground level and the drone were not significantly different. The monitoring of nest occupation by drones was more precise for northern goshawks. Monitoring using drones showed a higher number of juveniles. Adult birds reacted weakly to the presence of the drone. Our study indicates that monitoring arboreal nests of birds of prey with drones is more effective than monitoring arboreal nests from the ground and does not elicit adverse reactions from the birds. Further studies should be conducted to determine the responses of other raptors.

Population monitoring and conservation implications of intra- and interspecific nest occupation rates in swallows.

With the exception of a few groups of birds, such as large raptors and colonial seabirds, direct counts of nests cannot be conducted over very large areas for most of the abundant and widely distributed species, and thus indirect methods are used to estimate their relative abundances and population sizes. However, many species of the Family Hirundinidae (swallows and martins) build their mud nests in discrete, predictable and accessible sites, which are reused across years. Therefore, the direct count of active nests could constitute a reliable method for estimating breeding population sizes and their changes at large spatial and temporal scales. We illustrate the feasibility of this monitoring approach through a single year survey of >2700 nests of three coexisting Old-World species, the barn swallow (Hirundo rustica), the red-rumped swallow (Cecropis daurica), and the crag martin (Ptyonoprogne rupestris), distributed across Portugal and Spain. Our results revealed changes in the use of nesting substrates and increases in interspecific nest usurpation rates over recent decades. While 56% of the nests of C. daurica were located in rocks five decades ago, almost 100% are nowadays located in anthropogenic substrates such as bridges, road culverts, and abandoned buildings, which could have favored the range expansion of this species. Nest occupation rates were surprisingly low (12% in C. daurica, 21% in H. rustica, and 37% in P. rupestris), and the proportion of abandoned nesting sites was very high (65% in C. daurica, 50% in H. rustica, and 27% in P. rupestris). Abandonment rates reflect the population decline reported for H. rustica. Notably, the usurpation of nests of C. daurica by house sparrows Passer domesticus, which is the main cause of breeding failure, has increased from 2.4% in 1976-1979 to 34.7% of the nests nowadays. The long-term monitoring of nests may constitute a reliable and affordable method, with the help of citizen science, for assessing changes in breeding population sizes and conservation threats of these and other mud-nest building hirundines worldwide.

Landscape structure and site characteristics influence whether the northern house martin Delichon urbicum occupies artificial nests.

Artificial nest sites can support populations of endangered species when they are correctly installed. Here we analysed the characteristics and conditions that determined whether the northern house martin Delichon urbicum occupied more than 300 artificial nests around the city of Münster, Germany. We found that artificial nest occupation rates were influenced by various environmental and temporal factors. Positive influences included a longer time since installation and, to a lesser extent, the number of artificial nests at the same site. Negative impacts were observed from higher proportions of sealed surface cover in the surrounding area and, to a lesser extent, southward exposure. The distance to the nearest water body and the number of occupied natural nests showed no significant effect. We compared our results with descriptive evidence from the grey literature and published reports, and we give recommendations for installing artificial house martin nests for conservation practitioners. Future studies should also investigate the potential negative effects of 'dirt boards' below the nests and of gaps between the roof and the artificial nests.

Modeling abundance and nest occupation of Pseudomyrmex termitarius as a function of detection factors and habitat structure in fragments of urban vegetation

Understanding the relationship between abundance and habitat variability is an underlying theme of ecological studies. Due to imperfect detection, robust estimates of population size require large efforts, especially for megadiverse taxa such as Formicidae, where most of the surveys rely on presence-absence or community data. Here, we used mixed occupation models to estimate the population abundance and local distribution of Pseudomyrmex termitarius (Formicidae: Pseudomyrmecinae) in nests when detection was imperfect. Our goal was to create a sampling protocol to estimate unbiased population parameters, taking into account several sources of heterogeneity that can affect the estimates (e.g., researcher detection variability, survey period, habitat variables). The advantage of this protocol is that it is time- and cost-effective for accessing common and easily identifiable ant species. We distributed 44 transects (2.5 × 20 m) with five subplots each in 2.33 ha of the vegetation remnants of the Cuiabá Campus of the Federal University of Mato Grosso (UFMT). In each subsample, we recorded the presence or absence of P. termitarius workers, as well as the count of other cooccurring ant species during two consecutive days and time periods (midday and 16:00). Canopy openness and soil compaction were recorded in each transect. Among all the sampling trials, we directly counted a maximum of 364 P. termitarius workers in 92 subplots. Both nest abundance and occupation estimates were directly related to soil compaction. The estimated probability of detection was 39% and was not affected by the period. On the other hand, despite P. termitarius being a noncryptic species in the study area, it had a stronger effect on detectability. Although P. termitarius is a subordinate species, the co-occurrence of other species does not explain its abundance and distribution in our study. Perhaps P. termitarius's preference for sites with more compact soils could favor it by filtering out or reducing the abundance of potential competitors. After taking into account soil compaction and researcher detection variability, we estimated that the species occurred in 70% of the study area with a density of approximately 0.09 nests/m². We expect that this protocol can be an additional tool to improve the knowledge of ants in general and, especially, the management of alien or economically relevant ant species.

Understanding ground-nesting habitat selection by waterbirds to prioritize invasive predator control on islands

The introduction of carnivores to islands affects the conservation status of native prey. For two decades, American mink (Neogale vison) has expanded its distribution in the sub-Antarctic archipelago of Austral Patagonia, while preying on nests of solitary ground-nesting birds. Here, upland geese (Chloephaga picta) and flightless steamer ducks (Tachyeres pteneres) are naïve to such predation risk because of the lack of native terrestrial predators. We used nest occupancy models to reveal preferred breeding habitats of those two ground-nesting waterbirds to prioritize areas for future mink control programs. We searched for nests along 80 transects on Navarino Island, southernmost Chile, and 11 transects on 10 nearby islets (3 ± 2.9 ha). Our results showed that islets were essential for breeding in comparison to the main island (5.3 nests/km versus 0.8 nests/km, respectively). The occupancy models revealed that islets were particularly important for flightless steamer ducks, endemic to western Patagonia. As breeding habitat, upland geese preferred medium-dense shrubland, and flightless steamer ducks preferred rocky coastlines. Nest detection was negatively affected by dense vegetation and, in the case of the upland geese, towards the end of the survey. Ten camera traps (n = 385 trap nights) revealed mink presence on all islets, highlighting their capacity to swim in cold water, up to 340 m distance from the main island. We conclude that islets represent breeding refuges for ground-nesting waterbirds and therefore advocate allocating resources for mink control during the warm season on islets. We also provide predictive maps of nesting habitat preference of upland geese and flightless steamer ducks for conservation managers to focus their often scarce human and financial resources on areas critical for breeding. Finally, we argue that detection probability should be an integral part of bird breeding studies, which can be methodologically achieved through targeting transects, not nests, as sample units.

Delay in Adélie penguin nest occupation restricts parental investment in nest construction and reduces reproductive output.

Reproductive success is an important demographic parameter that can be driven by environmental and behavioural factors operating on various spatio-temporal scales. As seabirds breed on land and forage in the ocean, processes occurring in both environments can influence their reproductive success. At various locations around East Antarctica, Adélie penguins' (Pygoscelis adeliae) reproductive success has been negatively linked to extensive sea-ice. In contrast, our study site in the Windmill Islands has limited fast ice present during the breeding season, allowing us to examine drivers of reproductive success under vastly different marine environmental conditions. Here, we examined the reproductive success of 450 Adélie penguin nests over a 10-year period using images obtained from remotely operated cameras. We analysed nest survival in relation to marine and climatic factors, environmental conditions at the camera site and immediately around the nest, and behavioural attributes reflecting parental investment and phenological timing. Our key result was a strong positive association between nest structure and chick survival, particularly when ground moisture and snow cover around the nest were high. Earlier nesting birds were more likely to build bigger nests, although it is unclear whether this is due to more time available to build nests or whether early arrival and high-quality nests are complementary traits. This intrinsic activity is likely to become more important if future predictions of increased snowfall in this region manifest.

Molecular form identification of anterior pituitary gland-secreted prolactin in chicken

Endocrine changes during bird reproduction are well documented. Prolactin (PRL) exhibits a strong relationship between incubation and broody behavior. The molecular forms of PRL in the anterior pituitary gland during the reproductive cycle have already been previously identified but not those in the secreted form. To identify the molecular forms of secreted PRL during the reproductive cycle, we thus monitored the physiological status and incubation behavior of 10 Silkie hens by a video recording system over 1–2 years. Nine out of ten mature hens exhibited incubation behavior multiple times during the experiment. Ten hens demonstrated two interesting features. In a typical clutch, hens spent 10–15 min in the nest to lay an egg. Once they spent over 1 h in the nest, the nest occupancy increased incrementally. This shift in the nest occupancy occurred 7–10 days before the incubation onset and was highly repeatable. Based on the behavior of the hens, we cultured the anterior pituitary gland during four stages (premature non-laying, laying, trans, and incubation) with physiological PRL-releasing factor, vasoactive intestinal peptide (VIP). Based on our two-dimensional protein analysis, glycosylated PRL (G-PRL) displayed several isoforms with varying isoelectric points (pI), whereas we could detect one primary signal for non-glycosylated PRL (NG-PRL). However, 3–4 NG-PRL isoforms were detected in the anterior pituitary gland. These results suggested that secreted PRL, especially from the trans and incubation stages, contains various isoforms and it is post-translationally glycosylated and phosphorylated.

Does nest occupancy by birds influence the microbial composition?

Nest microbiota plays a vital role in the breeding and development of birds, which not only provides protection to bird hosts but also negatively affects the host. At present, it is unclear whether the composition of the microbes in the nests is affected by nesting. For this reason, we hung artificial nest boxes to simulate the natural nesting environment and combined 16S rRNA and ITS high-throughput sequencing technology to further study the differences in microbial composition and richness between used nests and control nests of Japanese tits (Parus minor). The study found that the bacteria in used nests and control nests showed significant differences at the phylum level (p < 0.05). It is also worth noting that the predominant bacteria in used nests were Proteobacteria (51.37%), Actinobacteria (29.72%), Bacteroidetes (6.59%), and Firmicutes (3.82%), while the predominant bacteria in control nests were Proteobacteria (93.70%), Bacteroidetes (2.33%), and Acidobacteria (2.06%). Both used nests and control nests showed similar fungi at the phylum level, which consisted mainly of Ascomycota and Basidiomycota, although significant differences were found in their relative abundance between both groups. The results of alpha diversity analysis showed significant differences in bacteria between the two groups and not in fungi. However, the beta diversity analysis showed significant differences between both bacteria and fungi. In summary, our results showed that the used nests had a higher abundance of beneficial microbiota and a lower presence of pathogenic microbiota. Therefore, we speculate that birds will change the characteristics of the nest microbial composition in the process of nest breeding to ensure their smooth reproductive development.

Is there an effect of electromagnetic waves from base stations on the breeding success of Ciconia ciconia ciconia in Algeria?

New nest supports used by the white stork Ciconia ciconia ciconia (Linnaeus, 1775) are mobile phone network relay antennas, which are not without danger because they emit electromagnetic waves that can have a major, although insidious, impact on the species. The aim of this study is to assess the effects of electromagnetic waves from mobile phone network base stations on white stork reproduction. We monitored the breeding phenology of the storks as a function of the distance of their nests from the base stations over 2 consecutive seasons, 2020 and 2021. The work took place in the North-East of Algeria, in Annaba and El-Tarf provinces. The nests were counted and divided into 3 distinct groups. The first is located on the relay antennae, the second less than 200 m and the third more than 300 m from the antennae. We calculated nest occupancy, number of young in the nest and number of nests without young. The results show that nests located directly on base stations have a reduced clutch size, not exceeding two storks and a low reproductive success since the majority of nests (51.9%) remained without young. The number of young storks tends to increase in nests far from base stations. Broods with 3 and 4 young are generally those located more than 300 m from relay antennas.

Using camera traps to inform reintroduction success and recovery of the Northern Aplomado Falcon (Falco femoralis septentrionalis)

Anthropogenic disturbances, including habitat changes, climate change, and pesticides, contribute significantly to species declines and extinctions worldwide. These disturbances also hinder conservation efforts like species reintroductions by creating novel ecosystems that no longer support the species that is being reintroduced. Using camera traps, we observed Great Horned Owls (Bubo virginianus), which are a dominant avian predator, perching on the nests of Northern Aplomado Falcons (Falco femoralis septentrionalis), a federally endangered species reintroduced to coastal Texas with a current breeding population of 23 pairs. The presence of Great Horned Owls on five of the twenty cameras placed on Northern Aplomado Falcon nest structures led us to consider the impact this interaction may have on occupancy and productivity of the nests. Throughout the study system, fast-growing tree and shrub species have become more prominent, which could be facilitating the interaction. We hypothesize that encroachment of woody vegetation is drawing Great Horned Owls into the open coastal grassland habitat of Northern Aplomado Falcons, which may limit the occupancy and productivity of falcon nests. Based on this hypothesis from the camera trap observations and anecdotal evidence of habitat encroachment, quantifying this relationship is a key next step in the recovery process. This will enable us to define priority areas for targeted restoration to push back woody vegetation, as well as areas best suited to release Northern Aplomado Falcons that will minimize the likelihood of predation by Great Horned Owls.

Commentary: Subadult Nest Occupancy Rates and Floater-To-Breeder Ratios in Raptor Population Assessment

Commentary: Subadult Nest Occupancy Rates and Floater-To-Breeder Ratios in Raptor Population Assessment

When food fights back: Cebid primate strategies of larval paper wasp predation and the high‐energy yield of high‐risk foraging

AbstractOptimal foraging theory predicts that well‐defended potential foods should be exploited only when energy pay‐offs are great. Although stinging hymenopteran nests are both well‐defended and predated by primates, their larvae's energy yields rarely have been calculated, and predation‐linked foraging behaviours by primates infrequently documented. Based on 58 opportunistic observations of primates raiding wasp nests for larvae, we calculated energetic yields of low‐ and high‐risk wasp nest predation for Cebus albifrons, Saimiri collinsi, S. sciureus and Sapajus apella, and tested predictions derived from optimal foraging theory. We recorded how nests were processed and by which age‐sex classes, eaten nest fragment sizes, number of occupied and empty cells, and nest occupancy patterns (percent larvae/pupae, eggs, empty cells). Basal metabolic rate (BMR) calculations showed energetic yields from 15 min foraging on low‐risk nests (Polybia quadricincta) would meet energy needed to sustain adult female and male C. albifrons BMR for 4.9 and 4.5 h, respectively; yields from high‐risk (Chartergus artifex) nests for 6.5 and 6.2 h; Mischocyttarus sp. nest yields (low risk, but mimetically resembling other wasps) would meet S. collinsi BMR for 2.9 h (female) and 2.3 h (male), and 2.6 and 2.1 h, for the slightly larger S. sciureus, respectively. The Chartergus energetic‐yield value is nearly 20% of a 36 g chocolate bar (741 kJ). Our data provide quantitative support for the common assertion that wasp larvae and pupae are high‐yield foods for primates. As predicted by optimal foraging, energetic yield is sufficient to offset the risk and pain of being stung.

Степной орёл в Алтае-Саянском регионе – результаты исследований 2019–2023 годов

Степной орёл в Алтае-Саянском регионе – результаты исследований 2019–2023 годов

Некоторые особенности гнездования орлов на территории ГНПП «Буйратау», Казахстан

Republican state institution “State National Park “Buiratau” (hereinafter referred as SNNP “Buiratau”) was created on March 11, 2011, in Ereymentau district of the Akmola region and the Osakarovsky district of the Karaganda region. Based on the analysis of literary sources and our observations, it can be assumed that about 227 bird species from 18 orders, including 19 species from the bids of prey (Minakov et al., 2019) can be encountered here. Since the Park formation, we began to mark raptor nests on its territory. Since 2022, together with the Biodiversity Research and Conservation Center (BRCC), we have been monitoring nest occupancy for three eagle species known to us: Golden Eagle (Aquila chrysaetos), Eastern Imperial Eagle (Aquila heliaca), Steppe Eagle (Aquila nipalensis). 31 eagle nests are known on the territory of Buiratau State National Park and its protective zone, of them 14 belonging to Eastern Imperial Eagle, 8 – to Golden Eagle, and 9 – to Steppe Eagle. For the period of 2022–2023, the number of identified inhabited nests (belonging to nesting pairs, used for nesting in a given year) changed slightly. For Eastern Imperial Eagle, it increased from 6 to 7, for Golden Eagle it increased from 1 to 3, for Steppe Eagle it remained the same, 3 breeding pairs. Encounters were recorded during eagle nests monitoring, indicating unusual, in our opinion, timelines of nesting for Golden Eagle and Eastern Imperial Eagle. For example, on May 26, 2023, we discovered a clutch of three Golden Eagle eggs in a nest on a cliff face on a 6 m high rock. The number of eggs in a clutch indicated that it was not a repeated one. Literary sources indicate that in Northern and Central Kazakhstan Golden Eagle starts laying eggs in the early April (Bragin, 1987). According to A.I. Marakshin, Golden Eagle nest with one egg was found near Zerenda on April 24 (Korelov, 1962). Thus, the Golden Eagle nest with a clutch located on May 26, 2023, can be considered late. It is unknown what could have caused the delay in the onset of reproduction of this Golden Eagle pair. On June 1 of the same year, one month old nestlings were observed in another Golden Eagle nest built on a birch tree.

Vércse költőláda kihelyezések tapasztalatai a Mosoni-Síkon

The Mosoni Plain Natura 2000 site is one of the most western nesting sites of the strictly protected Red-footed Falcon (Falco vespertinus) in Hungary, and the Common Kestrel (Falco tinnunculus) is the most common nesting bird of prey in the area. The breeding success of these two species, which do not build nests, can be greatly enhanced by the installation of good quality and properly placed artificial nests boxes. Monitoring of the artificial nest-boxes was previously not regularly and entirely conducted. However, from 2019 onwards, the now nearly 100 active nest-boxes are being regularly monitored, recording nest occupancy, clutch size and fledging data for Red-footed falcon, Common Kestrel, as well as for the Long-eared owl. The presenent paper summarises the nesting records of these three species on artificial breeding sites on the Moson Plain. During the period 2019–2023, we observed a total of 12 Red-footed Falcon breedings, 7 of which were in artificial nestboxes. On average, 3.0 chicks were successfully fledged from the boxes. Regarding Common Kestrel, a total of 121 breedings were recorded in nesting boxes, of which more than 80% were successful. On average 3.84 chicks fledged per nest box. During the 5 years of the study, a total of 14 pairs of Long-eared Owl breeding were associated with artificial nest-boxes, of which 10 proved successful. A total of 35 chicks fledged successfully.

Spatial modeling of Sarus Crane nest site suitability in Cambodia to help target conservation of breeding areas

To understand the breeding habitat requirements of the small, highly threatened migratory population of Eastern Sarus Crane (Grus antigone sharpii) in Cambodia and Vietnam, we assessed nest site selection at two different spatial scales: at the scale of individually occupied wetlands within the deciduous dipterocarp forests of Kulen Promtep and Chep Wildlife Sanctuaries, and at a landscape scale covering all such forested areas in northern Cambodia. To model the likelihood of nest occupancy within the landscape, results of aerial surveys for Sarus Crane nests, conducted in 2001, were combined with topographical and environmental spatial data. A second model incorporated deforestation and road development in the landscape between 2001 and 2016.We found that Sarus Cranes in Cambodia typically nested in remote rain-fed wetlands that formed on flat terrain in the upper reaches of drainage basins. Within these small, forested wetland units, nests were often placed in deeper, well-defined ponds, although three-quarters of all nests were placed randomly in relation to water level. Nest locations were further from roads and agricultural areas than random points.Most of the best nesting habitat, including Kulen Promtep and Chep Wildlife Sanctuaries, was located on Cambodia’s Northern Plains (247 km2 of habitat with a predicted occupancy likelihood of >75 % inside protected areas and 77 km2 outside), with smaller patches of highly suitable areas scattered across the Eastern Plains (15 km2 inside protected areas and 11 km2 outside).Between 2001 and 2016, 14,215 km2 (15 %) of the original deciduous dipterocarp forest cover was cleared for agriculture, 1,605 km of road was constructed and the area of habitat with a predicted occupancy likelihood of >75 % shrank by 69 % in the Northern Plains (66 % inside protected areas and 79 % outside) and 73 % in the Eastern Plains (80 % inside and 64 % outside). In Kulen Promtep and Chep, cranes continued to nest but in areas modeled as having lower suitability. We recommend (i) strengthening protection of Kulen Promtep and Chep Wildlife Sanctuaries in the Northern Plains and of remaining nesting habitat in other protected areas; (ii) surveying for active nesting in areas having the highest suitability classes based on the 2001 model but not currently protected, particularly south of Kulen Promtep; (iii) in the meantime, take immediate steps towards protecting as much remaining habitat as possible, that was modeled as highly suitable, to allow for population recovery or in case subsequent surveys find it occupied.

Differential effects of anthropogenic noise and vegetation cover on the breeding phenology and success of two urban passerines

The urban environment is associated with a multitude of challenges and stressors for populations of wild species from the surrounding natural environment. Among those, habitat fragmentation and noise pollution are suspected to have negative effects on the behavior and physiology of free-living birds in urban areas. Exposure in early life and chronic exposure to anthropogenic noise could be particularly deleterious, with short-and long-term consequences. In this study, we investigated if noise levels in city parks affect the distribution and reproductive success of two common bird species in the urban environment, the great tit (Parus major) and the blue tit (Cyanistes caeruleus) and if vegetation cover could mitigate those effects. We predicted that high noise levels might correlate with a decreased nest-box occupancy rate, a delayed laying date or a decreased clutch size, hatching, and fledging success. On the contrary, vegetation cover was expected to correlate positively with nest occupancy rate, advanced laying date, increased clutch size, hatching, and fledging success. We used data from population monitoring collected between 2012 and 2019 in parks and green public spaces in the city center and suburbs of Paris, France, and did not find any correlation between nest occupancy rates and noise levels or vegetation cover for both species. Laying date was not significantly related to anthropogenic noise in any species but was delayed with increasing vegetation cover in the great tit, while we did not find any association with clutch size. Hatching success in blue tits negatively correlated with increasing noise levels, and positively with increasing vegetation coverage. Finally, we did not find any correlation between anthropogenic noise or vegetation cover and the clutch size or fledging success in both species. In this study, two closely related species that share a common environment show a different sensibility to environmental parameters during reproduction, a key period for population maintenance. It also highlights the importance of considering multiple parameters when studying wild populations living in the urban environment.

Contrasting effects of landscape on nest founding and colony success of bumble bees in a mixed‐crop agroecosystem

Abstract Nest‐founding bumble bee queens search landscapes broadly for a nest site, whose later‐developed workers are constrained to foraging around the nest. Landscape could therefore have different influences on nest site selection and subsequent colony success. Additionally, the density of bumble bees in a landscape reflects the product of their nest density and nest success. To examine separate landscape effects on nest density and success, we examined nest occupancy (reflecting nest density) and colony size (reflecting nest success) using ground‐installed nest boxes placed adjacent to blueberry (Vaccinium corymbosum) fields in the Lower Mainland of British Columbia, Canada. Nest‐searching queens occupied 59% of these boxes. We classified landscapes in a 1.5 km radius of colonies using habitats of a priori relevance to bumble bees: beneficial (i.e. flowering) agriculture, non‐beneficial agriculture (NBA), forest, open semi‐natural, suburban, and their configuration (habitat edge density). Landscape strongly affected nest founding but only weakly affected colony success. Nest founding increased in landscapes with more forest habitat, more open semi‐natural habitat (and little NBA), and more habitat edge (and little NBA). Colony success increased in landscapes with more edge density (and much NBA). Overall, edge habitats enhanced bumble bee populations, but enhancement was conditional: edge increased nest occupation in landscapes with little NBA and nest success in landscapes with a lot of NBA. Populations of crop‐pollinating bumble bees might therefore best be enhanced by locally enhancing nesting: protecting forests, 2D semi‐natural habitats (when flowering crops are uncommon), and edge habitats.

Use of reed stalk trap nests by insects within the reed beds and in nearby steppic habitats

Trap nests made from stalks or stems of eudominant plants, such as Phragmites australis (reed) and Solidago canadensis (goldenrod), have been frequently used in previous studies. Nevertheless, trap nest occupancy in large stands of source plants remains poorly understood. We deployed trap nests made from stems with and stalks without parenchyma to steppic grasslands and terrestrial reed bed margins (64 localities in Central Europe) and matched the data with those from Moericke traps and phytocenologic relevés. The reed stalk trap nests attracted a much more abundant assemblage of Aculeata than the goldenrod stem trap nests. However, a large part of the species nesting in goldenrod stem trap nests overlapped with the species that used (and preferred) reed stalk trap nests. Ten aculeate species, which were present in large amounts in trap nests, were completely absent from the Moericke traps, and others were present in limited quantities. In natural habitats, trap-nesting bees and wasps had lower dominance but similar Fisher alpha values as those in anthropogenic habitats. Cavities in stems with or stalks without parenchyma served as previously undervalued nesting resources and an important monitoring tool. Trap-nesting species readily adopted broken stems and stalks even within stands of the source plants, the common reed and the goldenrod. Therefore, the conservation of threatened bee and wasp species that are associated with these cavities and are limited to habitats of natural origin requires conservation management that allows the presence of broken stems and stalks of ≥1 year of age in the proximity of the potential feeding habitats.