Nest Density Research Articles

Fragmentation shapes nest density and social structure but not genetic diversity of Temnothorax crassispinus (Formicidae)

AbstractHuman activities affect biodiversity by reducing the area of habitats, altering their shape, and increasing their isolation. Ants are particularly sensitive to habitat fragmentation, as it may locally change abiotic conditions, the availability of food and nest sites, the abundance of mutualists, competitors and predators, and also restrict gene flow between patches. As a result, the genetic population and colony structure of ants is expected to show signs of fragmentation. In the present study, we investigated the impact of fragmentation on the ant Temnothorax crassispinus in 45 forest patches across the Franconian Jura, Germany. Based on 283 colonies, of which 156 were genetically analyzed, we evidenced the presence of two putative distinct genetic clusters in the study area. Both the nest densities and the presence of queen were impacted by the number of adjacent forest patches within 400 m around the focal patch, but neither by patch shape nor patch size. We could not detect any effect of fragmentation on the genetic diversity, probably because the high dispersal abilities of T. crassispinus counterbalance any detrimental genetic consequences of fragmentation. Nevertheless, fragmentation still impacts the species density as well as the social structure of its colonies. Further investigations regarding the drivers of occurrence at a finer spatial scale might clarify the role of edge effects on the occurrence of this species.

Detecting ecological traps in human-altered landscapes: A case study of the thick-billed longspur nesting in croplands.

Conversion of the North American prairies to cropland remains a prominent threat to grassland bird populations. Yet, a few species nest in these vastly modified systems. Thick-billed longspurs historically nested in recently disturbed or sparsely vegetated patches within native mixed-grass prairie, but observations of longspurs in spring cereal and pulse crop fields during the breeding season in northeastern Montana, USA, suggest such fields also provide cues for habitat selection. Maladaptive selection for poor-quality habitat may contribute to ongoing declines in longspur populations, but information on thick-billed longspur breeding ecology in crop fields is lacking. We hypothesized that crop fields may function as ecological traps; specifically, we expected that crop fields may provide cues for territory selection, but frequent human disturbance would result in reduced reproduction. To address this hypothesis, we compared measures of habitat selection (settlement patterns and trends in abundance) and productivity (nest density, nest survival, and number of young fledged) between crop fields and native grassland sites during 2020-2021. Across both years, settlement patterns were similar between site types and occupancy ranged from 0.52 ± 0.17 SE to 0.99 ± 0.01 on April 7 and 30, respectively. Early season abundance differed by year, and changes in abundance during the breeding season appeared to be associated with precipitation-driven vegetation conditions rather than habitat type. While an index of nest density was lower in crop than native sites, the number of young fledged per successful nest (2.9 ± 0.18 SE) and nest survival (0.24 ± 0.03 SE; n = 222 nests) were similar for crop and native sites. Collectively, the data did not support our ecological trap hypothesis: longspurs did not exhibit a clear preference for crop sites and reproductive output was not significantly reduced. Our results indicate that croplands may provide alternative breeding habitat within a human-dominated landscape.

Estimating direct and indirect effects of habitat structure on nesting field sparrows (Spizella pusilla) using structural equation models

Due to consistent population declines across the continent, grassland birds have become a guild of high conservation and management interest. Despite a large number of studies investigating grassland bird habitat associations, we know relatively little about the mechanisms through which habitat characteristics may impact grassland birds, as these mechanisms are often assumed rather than directly tested. For this study, we estimated whether the effects of habitat structure on breeding Field Sparrows are mediated through changes in predator (snake and raccoon) abundance, alternative prey availability, or arthropod biomass using structural equation models. We found no evidence of nest survival or nest density of Field Sparrows being directly influenced by nest predator abundance, alternative prey, or arthropod biomass, although habitat characteristics associated with increased nest survival were also associated with greater arthropod biomass and reduced predator abundance. We suggest that habitat structure in our study area primarily impacts breeding Field Sparrows through direct means, such as influencing nest concealment or foraging efficiency. Our results also suggest that nest success and nest density are decoupled in our study area, so Field Sparrows may be preferentially selecting nest sites with structural characteristics that do not increase nest survival. Ultimately, our findings from this study indicate that while predator avoidance and food provisioning likely play an important role in determining nest survival for grassland birds, predator abundance and arthropod biomass may not necessarily predict predation risk and foraging efficiency to the extent that is often assumed.

White Storks nest at high densities near landfills changing stork nesting distributions in the last four decades in Central Spain

AbstractHuman-induced environmental changes are the main drivers of the ongoing redistribution of biodiversity. The millions of tons of organic waste that is added daily to landfills can increase the carrying capacity of ecological systems with direct effects on species’ population sizes and/or distributions. Understanding the effect of landfills on bird distribution is essential to assess management decisions. Our aim was to determine the role of landfills in the distribution of the breeding population of White Storks (Ciconia ciconia) in the last 4 decades. For that purpose, we used historical and current census data of breeding pairs before and after landfill exploitation. In this study, we found that landfills have altered the distribution of the breeding population over the last 4 decades in the province of Madrid, Spain. We found that birds occupied new nesting sites near landfills independently of habitat quality as defined by prey abundance and quality according to the previous studies. Nest density was higher near landfills and increased after the landfills began to be utilized by this species. Population growth and extremely high breeding densities may translate into conflicts with humans, particularly when new nesting sites are in urban areas, and possibly alter the perception of this bird species by the human population. Landfill closures, mandated by the European Landfill legislation, are an opportunity to reduce the effects of landfills on animal populations, and reduce human–wildlife conflicts. However, there must be a process of transition and a preliminary evaluation of habitat quality and suitability in the region to avoid a dramatic decline of the White Stork population.

Local and landscape environmental heterogeneity drive ant community structure in temperate seminatural upland grasslands.

Environmental heterogeneity is an important driver of ecological communities. Here, we assessed the effects of local and landscape spatial environmental heterogeneity on ant community structure in temperate seminatural upland grasslands of Central Germany. We surveyed 33 grassland sites representing a gradient in elevation and landscape composition. Local environmental heterogeneity was measured in terms of variability of temperature and moisture within and between grasslands sites. Grassland management type (pasture vs. meadows) was additionally included as a local environmental heterogeneity measure. The complexity of habitat types in the surroundings of grassland sites was used as a measure of landscape environmental heterogeneity. As descriptors of ant community structure, we considered species composition in terms of nest density, community evenness, and functional response traits. We found that extensively grazed pastures and within-site heterogeneity in soil moisture at local scale, and a high diversity of land cover types at the landscape scale affected ant species composition by promoting higher nest densities of some species. Ant community evenness was high in wetter grasslands with low within-site variability in soil moisture and surrounded by a less diverse landscape. Fourth-corner models revealed that ant community structure response to environmental heterogeneity was mediated mainly by worker size, colony size, and life history traits related with colony reproduction and foundation. We discuss how within-site local variability in soil moisture and low-intensity grazing promote ant species densities and highlight the role of habitat temperature and humidity affecting community evenness. We hypothesize that a higher diversity of land cover types in a forest-dominated landscape buffers less favorable environmental conditions for ant species establishment and dispersal between grasslands. We conclude that spatial environmental heterogeneity at local and landscape scale plays an important role as deterministic force in filtering ant species and, along with neutral processes (e.g., stochastic colonization), in shaping ant community structure in temperate seminatural upland grasslands.

First penetration of pine processionary moth (Thaumetopoea pityocampa) in North Bulgaria

The pine processionary moth (Thaumetopoea pityocampa) was reported for the first time in North Bul-garia in 2022. Winter nests of the pest were observed in a number of pine plantations in more than 10 sites of four Forest State Enterprises (Troyan, Sevlievo, Gabrovo, Plachkovtsi). The penetration of the pest into the new localities is due to a long-distance dispersion by vehicles. In January 2023, the nests in new localities contained fifth-instar larvae of T. pityocampa. Only about 3% of them were empty as larvae had descended in the soil for pupation. Based on the high population density and presence of old nests in some localities, it was assumed that the pest penetrated into Northern Bulgaria most likely 3-4 years ago. 

Frequency and types of alternative breeding strategies employed by nesting American black ducks in North Carolina.

Although most birds are considered to be at least partially monogamous, molecular evidence continues to uncover that many species can have multiple sexual mates. Many species of Waterfowl (Order Anseriformes) consistently deploy alternative breeding strategies, and although cavity nesting species have been well studied, few attempts to understand rates of alternative breeding strategies exist in the Anatini tribe. Here, we assay mitochondrial DNA and thousands of nuclear markers across 20 broods of American black ducks (Anas rubripes; "black duck") that included 19 females and 172 offspring to study population structure as well as types and rates of secondary breeding strategies in coastal North Carolina. First, we report high levels of relatedness among nesting black ducks and offspring and while 17 (of 19) females were of pure black duck descent, three were found to be black duck x mallard (A. platyrhynchos) hybrids. Next, we evaluated for mismatched mitochondrial DNA and paternity identities across each female's clutch to determine types and frequency of alternative or secondary breeding strategies. Although we report that nest parasitism occurred in two nests, 37% (7 of 19) of the sampled nests were multi-paternal as a result of extra-pair copulation. In addition to being part of a mix of strategies used to increase fecundity by successfully breeding females, we posit nest densities providing easier alternative mate access for males also explains high rates of extra-pair copulation among our sampled black ducks. Ultimately, however, while some proportion of females of many species engage in forms of secondary breeding strategies, we conclude that the decision to do so appears to be seasonally flexible for each individual.

Semi-natural habitats on organic strawberry farms and in surrounding landscapes promote bird biodiversity and pest control potential

Agricultural intensification and expansion have degraded biodiversity in agroecosystems, jeopardizing the ecosystem services provided by wildlife. Birds can act as particularly important purveyors of ecosystem services to farmers by consuming arthropod pests. Some bird species, however, may sometimes act as pests themselves by consuming crops. Further, on-farm management practices (e.g., crop diversity, vegetative structure) and the complexity of the surrounding landscape can shift the balance of bird-mediated ecosystem services and disservices through changes in bird community composition. Here, we explored how organic strawberry farms in California could be managed to bolster bird biodiversity and shift community composition from strawberry-consuming to pest-eating species. Using multi-species N-mixture models we found that semi-natural habitat at the landscape (1000 m) and farm (50 m) scales were positively associated with mean abundance of all birds, with varying effects on different species. In particular, we found that the mean local abundance of species that consume Lygus spp. (a major pest), but not strawberry-consuming species, increased with semi-natural habitat at the farm scale. Nest density in developed areas within farms also increased with greater semi-natural habitat in the landscape, while nest density in semi-natural habitat within farms decreased with increasing semi-natural habitat in the landscape. Further, nest density of Lygus spp. eating birds increased with increasing local semi-natural habitat. These results suggest that increasing semi-natural habitat at the landscape and local scales can bolster bird abundance across farms, while pest control can be promoted locally by conserving or restoring semi-natural vegetation at the farm scale.

Biogeography, climate, and land use create a mosaic of parasite risk in native bumble bees

Host-parasite interactions are crucial to the regulation of host population growth, as they often impact both long-term population stability and ecological functioning. Animal hosts navigate a number of environmental conditions, including local climate, anthropogenic land use, and varying degrees of spatial isolation, all of which can mediate parasitism exposure. Despite this, we know little about the potential for these environmental conditions to impact pathogen prevalence at biogeographic scales, especially for key ecosystem service-providing animals. Bees are essential pollination providers that may be particularly sensitive to biogeography, climate, and land-use as these factors are known to limit bee dispersal and contribute to underlying population genetic variation, which may also impact host-parasite interactions. Importantly, many native bumble bee species have recently shown geographic range contractions, reduced genetic diversity, and increased parasitism rates, highlighting the potential importance of interacting and synergistic stressors. In this study, we incorporate spatially explicit environmental, biogeographic, and land-use data in combination with genetically derived host population data to conduct a large-scale epidemiological assessment of the drivers of pathogen prevalence across >1000 km for a keystone western US pollinator, the bumble bee Bombus vosnesenskii. We found high rates of infection from Crithidia bombi and C. expoekii, which show strong spatial autocorrelation and which were more prevalent in northern latitudes. We also show that land use barriers best explained differences in parasite prevalence and parasite community composition, while precipitation, elevation, and B. vosnesenskii nesting density were important drivers of parasite prevalence. Overall, our results demonstrate that human land use can impact critical host-parasite interactions for native bees at massive spatial scales. Further, our work indicates that disease-related survey and conservation measures should take into account the independent and interacting influences of climate, biogeography, land use, and local population dynamics.

Structure-property relationships that influence platinum stability in all-silica or highly siliceous zeolites

In this study we examine the role of alkali cations and siloxy/silanol nests in stabilizing platinum clusters on all-silica zeolites. This work complements a recent study by the Corma group at Instituto de Tecnología Química (ITQ) that investigated platinum stability within Pt–K/MFI zeolites prepared by one-pot methods [1]. Here we demonstrate that stable platinum particles are likewise produced either by impregnating platinum onto an alkali-cation-containing all-silica MFI or by deboronating a borosilicate to create silanol nests and then co-impregnating with potassium and platinum sources. In this context, stability is assessed by resistance to sintering as measured by hydrogen chemisorption. Platinum impregnation alone onto a deboronated or borosilicate MFI does not produce stable platinum clusters after reduction. Furthermore, a one-pot synthesis of a Pt–K/B-MFI (borosilicate) or exchange of Pt onto a K-containing borosilicate does not lead to stable Pt particles. This further demonstrates the necessity of internal silanol/siloxy nests in stabilizing platinum clusters. In summary, silanols and alkali cations together create silanol/siloxy nests that stabilize Pt clusters. Hence, stable Pt clusters can be achieved by 1) a one-pot synthesis of the all-silica zeolite in the presence of Pt and alkali cations, 2) platinum impregnation on an all-silica sample that has occluded a high enough concentration of an alkali cation during the synthesis, or 3) by co-impregnating platinum and alkali metal cations together onto a calcined zeolite that has a high density of internal silanol nests. These nests can be generated by removal of boron from the framework of the zeolite. In the current study, we have examined these systems by 11B and 29Si NMR spectroscopy.

Гнездовые группировки орлов на ключевой орнитологической территории «Чинк Донызтау» в 2022 году

Гнездовые группировки орлов на ключевой орнитологической территории «Чинк Донызтау» в 2022 году

Nest density of Atta sexdens (Linnaeus, 1758) in Atlantic Forest restoration sites depends on the surrounding landscape

Abstract Herbivory is an important ecological filter, affecting plant establishment in restoration sites. One group of herbivores whose abundance has been increasing with environmental changes are the leaf-cutting ants (LCA). Here we evaluated the influence of the surrounding landscape on Atta sexdens nest density in restoration sites, by testing the hypothesis that sites farthest from forest fragments or with less surrounding habitat cover have higher nest density. The study was conducted in eleven reforestations with native species, amidst an agricultural matrix in southern Brazil. For each site, we estimated LCA nest density (active, inactive and total) and landscape metrics (distance to nearest forest fragment, surrounding habitat area and an index combining both distance and surrounding habitat area, the Proximity Index). There were negative relationships between active and total nest density and surrounding habitat area. These results suggest that increased isolation from forest fragments is a factor contributing to the relaxation of top-down control. Therefore, the increase in A. sexdens population density in restoration sites is a result, at least in part, of low pressure from natural enemies, since LCA are not limited by resource availability.

Проект «Скопа в России»: основные результаты работы в 2019–2023 годах

Проект «Скопа в России»: основные результаты работы в 2019–2023 годах

Three grassland bird species’ responses to fire and habitat structure in southern Illinois, USA suggest broad benefits of grassland size and plant diversity

Grassland birds are the most rapidly declining bird guild in North America, largely due to extensive habitat loss and fragmentation. Because many grassland bird species have different habitat preferences, managing grasslands to provide habitat for a range of species can be a challenge. We used four years of data from southern Illinois, USA grasslands to estimate the influence of prescribed fire and habitat structure on nest survival, nest density, and abundance of three grassland bird species with different habitat preferences: Dickcissel (<em>Spiza americana</em>), Field Sparrow (<em>Spizella pusilla</em>), and Common Yellowthroat (<em>Geothlypis trichas</em>). We found that Dickcissels exhibited the strongest response to prescribed fire, as nest density and nest survival both increased after previously undisturbed grasslands were burned. Fire may have also benefitted Common Yellowthroats and Field Sparrows by reducing woody cover and increasing bare ground, both of which were characteristics associated with nest survival for these birds. Dickcissel abundance was positively related to plant diversity within a grassland and agriculture in the surrounding landscape (within 400 m of a grassland patch), and negatively related to edge-interior ratio. Field Sparrows demonstrated a positive association with woody cover and proximity to forests. Common Yellowthroats were associated with tall vegetation and agriculture in the surrounding landscape. Both Field Sparrows and Common Yellowthroats associated positively with habitat characteristics that reduced nest survival, suggesting potential adaptive mismatches. Our results suggest that periodic prescribed fire, increased plant diversity, and larger patch size may simultaneously benefit a broad variety of grassland bird species with different habitat preferences.

Новые данные о гнездовании беркута в бассейне реки Бердь, Новосибирская область, Россия

Новые данные о гнездовании беркута в бассейне реки Бердь, Новосибирская область, Россия

Diversity and spatial distribution of native bees in Mt. Banahaw de Lucban, Philippines

Abstract Native bees are pollinators and bioindicators of ecosystem health but only little is known about its abundance, species distribution, and habitat range, especially in the Philippines. This study assessed the diversity and spatial distribution of native bees in Mt. Banahaw de Lucban (MBDL). Belt transect coupled with opportunistic sampling were used in the inventory of bees and their nests. Nests occurrence and 7 environmental predictor variables including; 1) annual mean temperature; 2) precipitation of warmest quarter; 3) elevation; 4) slope; 5) Normalized Difference Vegetation Index (NDVI); 6) distance to agricultural areas (m); and 7) distance to forested areas (m) were used for modeling species distribution by MaxEnt. A total of 16 species of native bees including representatives from genus Apis, Tetragonula, Lasioglossum, Halictus, Hylaeus and Megachile were identified. A total of 96 bee nests from 5 species were also recorded yielding a nests density of 234 nests per km2. Results showed medium diversity of solitary native bees with H’ of 2.488. Most bee nests were found in lower elevations while the distance from agricultural areas and the distance from forest areas had the highest contributions to the nesting of Apis breviligula, A. cerana, and Tetragonula biroi. The mean distance from forest areas of all bee nests was 649.930 m and the mean extent of suitable area for these species was 5.340 km2. Hence, a landscape approach may be more appropriate to conserve native bees and sustain the ecosystem services they provide in MBDL.

Результаты мониторинга гнездовых популяций солнечного орла в Дагестане (Россия) в 2022–2023 гг.

Результаты мониторинга гнездовых популяций солнечного орла в Дагестане (Россия) в 2022–2023 гг.

Степной орел на территории резервата «Бокейорда» и Ащиозекского заказника (Западно-Казахстанская область) в 2022–2023 годы

Степной орел на территории резервата «Бокейорда» и Ащиозекского заказника (Западно-Казахстанская область) в 2022–2023 годы

Within-colony nest distribution of a waterbird mixed colony in a small alluvial forest at El Salvador

ABSTRACT Breeding in colonies is a defining characteristic of many waterbird species and several behavioural and habitat traits determine nest-site selection. Although there is relatively extensive literature on the topic, information on the within-colony distribution of nests lacks for mixed colonies, especially for ardeid-cormorant associations and in regions such as Central America. Here, geospatial data on vegetation associated with a mixed colony, established in a small alluvial forest northwest of El Salvador and collected from June to November 2015 was assessed to identify some behavioural and habitat features that could influence nest-site selection. Four ardeid species (Ardea alba, Egretta thula, Bubulcus ibis, and Nycticorax nycticorax) and one cormorant (Phalacrocorax brasilianus) conformed the colony, where the last was the outstanding species. The total area of the colony was 2.14 ha (14% of La Barra forest) with high nest densities (584.58 nests/ha). Spatial analyses indicate that some species prefer to occupy trees/shrubs close to other trees/shrubs with conspecific or similarly sized species. A remarkable height-strata distribution was found, with large-sized species in the canopy, and small-sized species in the lower strata. The resulting estimates of the generalized linear models applied suggest that the within-colony nest-site selection is determined by the combination of higher heights of the tree/shrub used for nesting, nearest distance to a food source, fewer species sharing the same tree/shrub and an increasing effect of the interaction of the latter two factors. Finally, the temporal evolution of La Barra’s colony shows that the increasing number of Neotropical Cormorants (Phalacrocorax brasilianus) could be shaping and threatening the colony’s species structure and possibly the vegetation as well. Conservation measures should be implemented to manage the population of this species.

Thirty-Eight Years of Loggerhead Turtle Nesting in Laganas Bay, Zakynthos, Greece: A Review

Here we present 38 yrs of nesting data of the loggerhead population in Laganas Bay, Zakynthos, Greece, adding data for 2010–2021 to existing published data for 1984–2009. This rookery, encompassing 6 discrete beaches of 5.5 km total length, features the highest nesting density in the Mediterranean. The annual nest numbers, ranging from 667 to 2018, showed no significant long-term trend. Beach nesting contributions increased on some public-accessed beaches (as did nesting success), but decreased on a remote beach that previously held > 50% of all nests. These changes might be attributed to management actions by the National Marine Park of Zakynthos that improved conditions for sea turtles (e.g., restricting nighttime access to the public), indicating that the previously recorded high nesting density on the remote beach may have been atypical. Although no significant phenological changes were detected with the available data in the 20-yr period 2002–2021, the date of the first hatched nest shifted significantly toward earlier dates in the 38-yr data set. Clutch size and body size of nesting turtles exhibited significantly decreasing trends. Hatching success, hatchling emergence success, and in-nest hatchling mortality showed significantly increasing trends. The number of viable hatchlings decreased over the seasons, albeit not significantly, possibly a result of the decreasing clutch size. Incubation durations were revealed as shortening on all beaches, a potential sign of global warming, with a consequent suggested increase of female primary sex ratio. Continuation of this long-term monitoring program is expected to provide further insights in the reproductive traits of this regionally important loggerhead population.