Terrestrial Insectivores Research Articles

Thermoregulation of understory birds in lowland Amazonia

Understanding the capacity for thermoregulation is critical for predicting organismal vulnerability to climate change, especially in lowland tropical rainforests, where warming conditions combine with high humidity and limited elevational or latitudinal refugia. Here, I focused on nine species of ground‐foraging insectivorous birds in the genus Myrmoderus, Myrmornis, Hylopezus, Myrmothera, Formicarius and Sclerurus – sensitive forest specialists characterized by recently documented population declines in both disturbed and undisturbed forests. Using high‐resolution data from loggers deployed on birds and their environment, I examined whether and how birds used thermoregulation and whether ambient water provided cooling opportunities. Variation in the rate of temperature change over the diel cycle suggested that all species employed behavioral and physiological thermoregulation, but some patterns differed by species' phylogenetic relatedness. All species warmed hours before their environment at sunrise, then experienced lower temperature increases at midday relative to the ambient thermal flux. These morning warming periods peaked around sunrise for all but Sclerurus rufigularis and constituted the diel temperature change maxima for five of the nine species. Six species exhibited pronounced oscillations in temperature change consistent with regular bathing around sunset, possibly for thermoregulatory or other purposes. This oscillation was the most prominent feature in the diel thermal flux for all three Sclerurus species and, to a lesser extent, for Myrmoderus ferrugineus, Myrmornis torquata and Myrmothera campanisona. Local rainfall reduced ambient temperatures, and birds experienced stronger cooling in the wet season and with higher rainfall intensity. However, rain‐induced cooling events were markedly absent in all three Sclerurus spp. These results highlight the fundamental role of water in avian thermoregulation and suggest that terrestrial insectivores attempt to maintain thermal homeostasis throughout the diel cycle. The observed thermoregulatory behaviors highlight a potentially critical aspect of their vulnerability – thermal regimes are profoundly altered by forest disturbance, climate change, and their combination.

Aquatic-terrestrial transfer of neonicotinoid insecticides in riparian food webs

Current-use pesticides are ubiquitous in freshwaters globally, often at very low concentrations. Emerging aquatic insects can accumulate pesticides during their aquatic development, which can be retained through their metamorphosis into terrestrial adults. Emerging insects thus provide a potential, yet largely understudied linkage for exposure of terrestrial insectivores to waterborne pesticides. We measured 82 low to moderately lipophilic organic pesticides (logKow: −2.87 to 6.9) in the aquatic environment, emerging insects and web-building riparian spiders from stream sites impacted by agricultural land use. Insecticides, mainly neuro-active neonicotinoids were ubiquitous and had the highest concentrations in emerging insects and spiders (∑ insecticides: 0.1–33 and 1–240 ng/g, respectively), although their concentrations in water were low, even when compared to global levels. Furthermore, neonicotinoids, although not considered to be bioaccumulative, were biomagnified in riparian spiders. In contrast, concentrations of fungicides and most herbicides decreased from the aquatic environment to the spiders. Our results provide evidence for the transfer and accumulation of neonicotinoids across the aquatic-terrestrial ecosystem boundary. This could threaten food webs in ecologically sensitive riparian areas worldwide.

Emergence phenology of the giant salmonfly and responses by birds in Idaho river networks

Emergence of adult aquatic insects from rivers is strongly influenced by water temperature, and emergence timing helps to determine the availability of this ephemeral food resource for birds and other terrestrial insectivores. It is poorly understood how spatial heterogeneity in riverine habitat mediates the timing of emergence. Such spatiotemporal variation may have consequences for terrestrial insectivores that rely on aquatic-derived prey resources. We investigated emergence phenology of the giant salmonfly, Pteronarcys californica, at three spatial scales in two Idaho river networks. We examined the influence of tributary confluences on salmonfly emergence timing and associated insectivorous bird responses. Salmonfly emergence timing was highly variable at the basin-scale during the period we sampled (May–June). Within sub-drainage pathways not punctuated by major tributaries, emergence followed a downstream-to-upstream pattern. At the scale of reaches, abrupt changes in thermal regimes created by 10 major tributary confluences created asynchrony in emergence of 1–6 days among the 20 reaches bracketing the confluences. We observed 10 bird species capturing emerged salmonflies, including 5 species typically associated with upland habitats (e.g., American robin, red-tailed hawk, American kestrel) but that likely aggregated along rivers to take advantage of emerging salmonflies. Some birds (e.g., Lewis’s woodpecker, western tanager, American dipper) captured large numbers of salmonflies, and some of these fed salmonflies to nestlings. Emergence asynchrony created by tributaries was associated with shifts in bird abundance and richness which both nearly doubled, on average, during salmonfly emergence. Thermal heterogeneity in river networks created asynchrony in aquatic insect phenology which prolonged the availability of this pulsed prey resource for insectivorous birds during key breeding times. Such interactions between spatial and temporal heterogeneity and organism phenology may be critical to understanding the consequences of fluxes of resources that link water and land. Shifts in phenology or curtailment of life history diversity in organisms like salmonflies may have implications for these organisms, but could also contribute to mismatches or constrain availability of pulsed resources to dependent consumers. These could be unforeseen consequences, for both aquatic and terrestrial organisms, of human-driven alteration and homogenization of riverscapes.

The carrion connection: Marine mammal carcasses provide an indirect subsidy to insectivorous birds

The transfer of energy from nutrient subsidies across ecological boundaries can link the dynamics of adjacent ecosystems. At the interface between land and sea, beach-cast marine mammal carcasses are a large and nutrient-rich food source available to shoreline scavengers. In addition to subsidizing scavengers directly, marine mammal carrion may also indirectly subsidize terrestrial animals by increasing prey abundance. As part of an ongoing study using camera traps to monitor marine mammal carrion along the California coast, I documented a Black Phoebe (Sayornis nigricans) utilizing a California sea lion (Zalophus californianus) carcass to forage for scavenging invertebrates. Given the widespread distribution of pinniped rookeries and terrestrial insectivores, it is likely that insectivores prey upon invertebrate scavengers of pinniped carrion in many locations where they co-occur.

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Diversity and DistributionsVolume 29, Issue 4 p. i-i COVER IMAGEOpen Access Cover page First published: 14 March 2023 https://doi.org/10.1111/ddi.13576AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract The cover image relates to the Research Article https://doi.org/10.1111/ddi.13662 “Low species turnover of upland Amazonian birds in the absence of physical barriers” by Rutt et al. Although the Black-faced Antthrush (Formicarius analis) is a widespread Neotropical species, this terrestrial insectivore was one of many forest birds detected less often at Reserva Ducke, suggesting that even a very large preserve is not insulated from anthropogenic degradation. Image credit: Cameron L. Rutt. Volume29, Issue4April 2023Pages i-i RelatedInformation

Aquatic-Terrestrial Insecticide Fluxes: Midges as Neonicotinoid Vectors.

Exposure of freshwater ecosystems to insecticides can negatively impact the development of emerging aquatic insects. These insects serve as an important nutritional subsidy for terrestrial insectivores. Changes in insect emergence phenology (i.e., emergence success and temporal pattern) or fluxes of insecticides retained by the emerging adults have the potential to negatively impact terrestrial food webs. These processes are influenced by contaminant toxicity, lipohilicity, or metabolic processes. The interplay between emergence phenology, contaminant retention through metamorphosis, and associated contaminant flux is not yet understood for current-use insecticides. In a microcosm study, we evaluated the impacts of a 24-h pulse exposure of one of three current-use insecticides, namely pirimicarb, indoxacarb, and thiacloprid, at two environmentally realistic concentration levels on the larval development and emergence of the nonbiting midge Chironomus riparius. In addition, we measured insecticide concentrations in the larvae and adults using ultrahigh performance liquid chromatography coupled to tandem mass spectrometry by electrospray ionization. Exposure to pirimicarb delayed larval development and emergence, and exposure to indoxacarb reduced emergence success. The neonicotinoid thiacloprid had the greatest impact by reducing larval survival and emergence success. At the same time, thiacloprid was the only insecticide measured in the adults with average concentrations of 10.3 and 37.3 ng/g after exposure at 0.1 and 4 µg/L, respectively. In addition, an approximate 30% higher survival to emergence after exposure to 0.1 µg/L relative to a 4-µg/L exposure resulted in a relatively higher flux of thiacloprid, from the aquatic to the terrestrial environment, at the lower exposure. Our experimental results help to explain the impacts of current-use insecticides on aquatic-terrestrial subsidy coupling and indicate the potential for widespread dietary exposure of terrestrial insectivores preying on emerging aquatic insects to the neonicotinoid thiacloprid. Environ Toxicol Chem 2023;42:60-70. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Climate trends and behavior of a model Amazonian terrestrial insectivore, black‐faced antthrush, indicate adjustment to hot and dry conditions

Rainforest loss threatens terrestrial insectivorous birds throughout the world's tropics. Recent evidence suggests these birds are declining in undisturbed Amazonian rainforest, possibly due to climate change. Here, we first asked whether Amazonian terrestrial insectivorous birds were exposed to increasingly extreme ambient conditions using 38 years of climate data. We found long‐term trends in temperature and precipitation at our study site, especially in the dry season, which was ~1.3°C hotter and 21% drier in 2019 than in 1981. Second, to test whether birds actively avoided hot and dry conditions, we used field sensors to identify periodic intervals of ambient extremes and prospective microclimate refugia within undisturbed rainforest from 2017 to 2019. Simultaneously, we examined how tagged black‐faced antthrushes Formicarius analis used this space. We collected > 1.3 million field measurements quantifying ambient conditions in the forest understory, including along elevation gradients. For 11 birds, we obtained GPS data to test whether birds adjusted their cover usage using variation in GPS fix success (n = 2724) as a proxy and elevation using successful locations (n = 640) across seasonal and daily cycles. For four additional birds, we collected > 180 000 light and temperature readings to assess exposure. Field measurements in the modern landscape revealed that temperature was higher in the dry season and highest on plateaus. Thus, low‐lying areas were relatively buffered, providing microclimate refugia during hot afternoons in the dry season. At those times, birds apparently entered cover and shifted downslope. Because climate change intensifies the hot, dry conditions that antthrushes seemingly avoid, our results are consistent with the hypothesis that climate change decreases habitat quality for this species. If other terrestrial insectivores are similarly sensitive, climate‐induced changes to otherwise intact rainforest may be related to their recent declines.

Contaminant fluxes across ecosystems mediated by aquatic insects.

Metals and organic contaminants in aquatic systems affect the coupling of aquatic and terrestrial ecosystems through two pathways: contaminant-induced effects on insect emergence and emergence-induced contaminant transfer. Consequently, the impact of aquatic contaminants on terrestrial ecosystems can be driven by modifications in the quantity and quality of adult aquatic insects serving as prey or contaminants entering terrestrial food webs as part of the diet of terrestrial predators. Here, we provide an overview of recent advances in the field, separating metals from organic contaminants due to their differential propensity to bioaccumulate and thus their potential contribution to either of the two pathways. Finally, this review highlights the knowledge gap in the relative impact of these pathways on terrestrial insectivores.

Light and thermal niches of ground‐foraging Amazonian insectivorous birds

Insectivores of the tropical rainforest floor are consistently among the most vulnerable birds to forest clearing and fragmentation. Several hypotheses attempt to explain this pattern, including sensitivity to extreme microclimates found near forest borders, particularly brighter and warmer conditions. Importantly, this "microclimate hypothesis" has additional implications for intact forest under global climate change that could be evaluated through direct assessment of the light and temperature environment of terrestrial insectivores. In this study, we harness novel technology to directly quantify the light and thermal niches of 10 species of terrestrial insectivores in undisturbed Amazonian rainforest. Loggers placed on birds (N=33) and their environment (N=9) recorded nearly continuous microclimate data from 2017 to 2019, amassing >5 million measurements. We found that midday light intensity in tree fall gaps (~39,000 lux) was >40 times higher than at the ground level of forest interior (950 lux). Light intensity registered by sensors placed on birds averaged 17.4 (range 3.9-41.5) lux, with species using only 4.3% (0.9%-10.4%) of available light on the forest floor. Birds therefore selected very dark microhabitats-the light environment was >2200 times brighter in tree fall gaps. Bird thermal niche was a function of ambient temperature as well as body temperature, which averaged >40.5°C but varied among species. Forest floor temperature peaked daily at 27.0°C, whereas bird loggers averaged 35.1°C (34.5-35.7°C) at midday. The antpitta Myrmothera campanisona and the antthrush Formicarius colma used thermal conditions closest to their body temperatures, whereas leaftossers (Sclerurus spp.) and Myrmornis torquata occupied relatively cool microclimates. We found no general link between abundance trends and variation in species-specific light and thermal niches. However, all species occupied markedly dim and cool microclimates. Because such conditions are rare outside the interior of primary forest, these results support the microclimate hypothesis in disturbed landscapes. Moreover, strong avoidance of conditions that are becoming more common under climate change highlights the vulnerability of terrestrial insectivores even in the absence of disturbance and may be the reason for enigmatic declines in Amazonia and elsewhere.

The effect of aquatic and terrestrial prey availability on metal accumulation in pied flycatcher (Ficedula hypoleuca) nestlings

Ingestion of contaminated prey is a major route for metal exposure in terrestrial insectivores. In terrestrial ecosystems adjacent to lakes and streams, emerging aquatic insects can transport metals, accumulated during their larval stage, from aquatic to terrestrial ecosystems. However, contaminant exposure via aquatic insects has often been ignored in terrestrial environments, despite such insects representing a substantial part of the diet for terrestrial insectivores living close to lakes and streams. In this study, we investigated how dietary lead (Pb) and calcium (Ca) exposure from different aquatic and terrestrial prey types affects Pb accumulation in pied flycatcher (Ficedula hypoleuca) nestlings living close to a former Pb/zinc (Zn) mine in northern Sweden, which closed in 2001. Stable isotope analysis (δ 13C and δ15N) of nestling blood and different prey types was used to estimate nestlings' diet. Ants, Lepidoptera larvae and Trichoptera were the most common prey types in the nestlings’ diet, in which aquatic prey types (Trichoptera included) accounted for 2.0–96.4%. Ingestion of specific prey groups, such as aquatic insects and ants, were important for Pb accumulation in nestlings, and when access to aquatic prey was low, ants were the predominant source of Pb. The influence of dietary Ca on Pb accumulation was less consistent, but Ca availability was relatively high and often co-occurred with high Pb concentrations in invertebrates. The study shows that both the proportion of different prey and their individual metal concentrations need to be considered when estimating exposure risks for insectivores. Further, it highlights the need to account for metal exposure from emerging aquatic insects for terrestrial insectivores living close to lakes and streams.

Caracterização da dieta e guilda trófica de peixes silvestres em área protegida

Abstract: Aim We characterize the diet and trophic guild to the fish community in a protected area to contribute information about the trophic ecology. Methods The collection was carried out at three sampling points, in 2017 and 2018, with the help of gill nets. The collected specimens were euthanized in a 0.5% benzocaine solution. In the laboratory, all specimens' stomachs were removed, fixed in a 4% formalin solution, and preserved in 70% alcohol. Stomach contents were examined, and the food items were identified to the lowest possible taxonomic level. Food items were quantified according to the volumetric method. The characterization of the diet was presented through the percentage volume of each food item consumed. To determination of the trophic guild of each species, the predominance of a type of food resource (> 51% of the total volume) in the population's diet was considered. Results The species' diets were distributed in 16 food items (predominance of decapods, fish fragments, terrestrial insects, and aquatic plants), and four trophic guilds were observed (carcinophage, piscivore, terrestrial insectivore, and herbivore). Furthermore, there was the occurrence of microplastic in the diet of three species. Conclusions the fish community evaluated here demonstrates the wide range of resources that can make up the fish diet and demonstrates the different trophic guilds that can be observed in a protected area. As it is a conservation unit, knowing the diet and trophic guilds that make up the fish community can contribute to understanding the dynamics of food chains, the structure of the community, and the functioning of the ecosystem. Thus, this work can contribute information about the biology of the species evaluated for future work and conservation programs.

Guild‐level response to Hurricane Carlotta among birds in a Mexican wetland

We analysed 36 months of point count data to determine the influence of Hurricane Carlotta on species composition in trophic guilds of birds in mangrove and marsh wetlands on the Oaxacan coast of Mexico. We predicted that post‐hurricane composition in guilds would respond to hurricane effects where bird species relied on resources from systems with previous local stability. Post‐hurricane turnover in composition was marked among terrestrial insectivores in mature mangroves, but not in early successional stages in marshland. Turnover was unexceptional among mangrove plant‐consumers that relied on trophic resources from surrounding ecosystem types, and among trophic guilds associated with highly dynamic aquatic systems.

Ten Bird Species, Six Guilds, Three Habitats, and 59 Chlorinated and Brominated POPs: What do 64 Eggs from the Largest Economic Hub of Southern Africa tell us?

There is little information on how POPs in eggs of different terrestrial, wetland, and aquatic birds share a large urban and rural landscape relate. We collected and analysed 64 eggs belonging to ten species of six feeding guilds, and compared organic chlorinated pesticide (OCP), polychlorinated biphenyl (PCB), and brominated flame retardants (BFR) residue concentrations and compositions. The eggs were collected in the Gauteng and the northern part of the Free Sate provinces of South Africa, one of the largest economic hubs in Africa. White-breasted Cormorant and African Darter eggs (at the highest trophic level as large aquatic predators) had the highest ΣOCP and ΣPCB concentrations, and Cape Sparrow and Southern Masked Weaver (granivores) eggs had the lowest concentrations, corresponding to the lowest trophic level in our collection. The highest percentage p,p'-DDT were in eggs of the terrestrial insectivore Crowned Lapwing (24%) and the scavenging African Sacred Ibis (17%), and the lowest in African Darter (1.0%) and White-breasted Cormorant (0.9%) eggs, suggesting that recency of DDT releases in a region cannot be gauged by this metric. African Sacred Ibis and Southern Masked Weaver eggs had the highest ΣBFR concentrations, with Crowned Lapwing, Cattle Egret, and White-breasted Cormorant eggs the least. Based on feeding guilds, the mean ΣPOP concentrations increased from granivore, aquatic omnivore, scavenger, terrestrial insectivore, small aquatic predator, to large aquatic predator. Mean ΣPOP concentrations in eggs increased from terrestrial, to wetland, to aquatic habitat birds. Interesting patterns were observed with multivariate analyses. There were no significant regressions between egg size and any summed POP classes. ΣBFR concentrations were not correlated with ΣOCPs or ΣPCBs. Eggshell thinning of African Darter eggs was associated with p,p'-DDE and ΣPCB suggesting risk. Other metrics also suggest risk. Therefore, different species of terrestrial and aquatic birds from the same area acquire and deposit POPs in different proportions and quantities in their eggs. Trophic levels and habitat explain the overall patterns, but detailed differences were found, some of which we are unable to explain. Based on POPs residues in terrestrial, wetland, and aquatic bird eggs, different POPs classes behave differently in a shared large inland industrial area, complicating deductions about POPs and associated risks based on one or few species.

Cross-Ecosystem Fluxes of Pesticides from Prairie Wetlands Mediated by Aquatic Insect Emergence: Implications for Terrestrial Insectivores.

Contaminants alter the quantity and quality of insect prey available to terrestrial insectivores. In agricultural regions, the quantity of aquatic insects emerging from freshwaters can be impacted by insecticides originating from surrounding croplands. We hypothesized that, in such regions, adult aquatic insects could also act as vectors of pesticide transfer to terrestrial food webs. To estimate insect-mediated pesticide flux from wetlands embedded in an important agricultural landscape, semipermanetly and temporarily ponded wetlands were surveyed in cropland and grassland landscapes across a natural salinity gradient in the Prairie Pothole Region of North Dakota (USA) during the bird breeding season in 2015 and 2016 (n = 14 and 15 wetlands, respectively). Current-use pesticides, including the herbicide atrazine and the insecticides bifenthrin and imidacloprid, were detected in newly emerged insects. Pesticide detections were similar in insects emerging from agricultural and grassland wetlands. Biomass of emerging aquatic insects decreased 43%, and insect-mediated pesticide flux increased 50% along the observed gradient in concentrations of insecticides in emerging aquatic insects (from 3 to 577 ng total insecticide g-1 insect). Overall, adult aquatic insects were estimated to transfer between 2 and 180 µg total pesticide wetland-1 d-1 to the terrestrial ecosystem. In one of the 2 study years, biomass of emerging adult aquatic insects was also 73% lower from agricultural than grassland wetlands and was dependent on salinity. Our results suggest that accumulated insecticides reduce the availability of adult aquatic insect prey for insectivores and potentially increase insectivore exposure to insect-borne pesticides. Adult aquatic insects retain pesticides across metamorphosis and may expose insectivores living near both agricultural and grassland wetlands to dietary sources of toxic chemicals. Environ Toxicol Chem 2021;40:2282-2296. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.

Erosion of tropical bird diversity over a century is influenced by abundance, diet and subtle climatic tolerances

Human alteration of landscapes leads to attrition of biodiversity. Recommendations for maximizing retention of species richness typically focus on protection and preservation of large habitat patches. Despite a century of protection from human disturbance, 27% of the 228 bird species initially detected on Barro Colorado Island (BCI), Panama, a large hilltop forest fragment isolated by waters of Gatun Lake, are now absent. Lost species were more likely to be initially uncommon and terrestrial insectivores. Analyses of the regional avifauna, exhaustively inventoried and mapped across 24 subregions, identified strong geographical discontinuities in species distributions associated with a steep transisthmian rainfall gradient. Having lost mostly species preferring humid forests, the BCI species assemblage continues to shift from one originally typical of wetter forests toward one now resembling bird communities in drier forests. Even when habitat remnants are large and protected for 100 years, altered habitat characteristics resulting from isolation produce non-random loss of species linked with their commonness, dietary preferences and subtle climatic sensitivities.

Variation in metal concentrations across a large contamination gradient is reflected in stream but not linked riparian food webs

Aquatic insects link food web dynamics across freshwater-terrestrial boundaries and subsidize terrestrial consumer populations. Contaminants that accumulate in larval aquatic insects and are retained across metamorphosis can increase dietary exposure for riparian insectivores. To better understand potential exposure of terrestrial insectivores to aquatically-derived trace metals, metal concentrations in water and tissues were analyzed from different components of streams and riparian food webs across a large (2–3 orders of magnitude) metal gradient (e.g., Zn, Cu, Cd, Pb) in the Rocky Mountains (USA). Our research indicates that the trace metal concentration gradient present among streams was lost during metamorphosis of aquatic larval insects into terrestrially flying adults, decoupling terrestrial exposures from aquatic concentrations. This pattern was caused by declines in 1) among-stream variation in trace metal concentrations, 2) relationships between metal concentrations in paired water and food web components, and 3) mean metal concentrations within aquatic food webs and across the aquatic-terrestrial boundary. Specifically, among-stream variation in trace metal concentrations was highest for water and aquatic vegetation, intermediate for aquatic insect larvae (~30% lower than water) and lowest for adult aquatic insects and riparian spiders (~65% lower). Metal concentrations in paired water and food web components ranged from highly related across the stream-metal gradient (slopes ~1) for water and aquatic vegetation, to less related (slopes closer to 0) for aquatic vegetation and aquatic insect larvae, to unrelated (slopes ~0) for aquatic larval and adult insects. Finally, mean metal concentrations were highest in aquatic vegetation and lowest in adult aquatic insects emerging from streams (~50% lower than aquatic vegetation). Our results indicate less efficient trophic transfer and higher metamorphic loss of trace metals from high metal streams (i.e., exposure-dependent transfer). For many trace metals, aquatic-terrestrial dietary transfer is unlikely to be an important source of exposure for terrestrial insectivores of adult aquatic insects.

Dietary DNA metabarcoding reveals seasonal trophic changes among three syntopic freshwater trout species

Abstract Providing taxonomically precise dietary characterisations for freshwater fish species is critical for gaining a deeper understanding of the trophic dynamics present in freshwater ecosystems. However, our current understanding of freshwater trophic ecology has relied almost entirely upon direct observation of foraging attempts or morphological identification of partially digested prey. Due to the limitations of morphological dietary characterisations of soft‐bodied arthropod prey, these techniques offer dietary descriptions that can lack satisfactory taxonomic resolution and may bias our interpretations of freshwater food webs. Recent advancements in DNA‐based prey identification have allowed for species‐level prey characterisations for many terrestrial insectivores, although these techniques have seldom been applied to understand the diets of freshwater fish. This study used DNA metabarcoding with high‐throughput, next‐generation sequencing to provide species‐level descriptions of prey composition for three naturally reproducing, syntopic freshwater trout species. Our study supports previous findings that suggested that brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss) are generalist predators that display a high degree of seasonal dietary flexibility. Prey composition varied significantly across sampling periods, with detection frequency of terrestrial prey greater in the spring/summer period compared to the autumn period. Pollution‐sensitive aquatic macroinvertebrates were detected frequently across both sampling periods, highlighting the importance of high‐quality streams that support such arthropod prey. DNA metabarcoding also detected a high richness of soft‐bodied, Lepidoptera prey species, a taxonomic group that has been largely underrepresented in previous trout dietary studies that used traditional morphological techniques. This study demonstrates the applicability of dietary DNA metabarcoding for the detection and species‐level identification of arthropods found in freshwater fish lavage samples and highlights the importance of taxonomically precise techniques when attempting to better understand trophic interactions within freshwater communities.

Riqueza y conservación de las aves del suroeste de Oaxaca

La vertiente del Pacífico mexicano en el suroeste de Oaxaca alberga una gran diversidad de aves que ha sido poco estudiada. Presentamos un inventario y análisis de la avifauna de esa región, mediante transectos, redes de niebla y observaciones no sistemáticas, en 12 localidades repartidas en cuatro tipos de vegetación (selva mediana subcaducifolia, vegetación ribereña, áreas sujetas a manejo agropecuario y selva baja caducifolia). Contabilizamos 120 especies, correspondientes a 39 familias y 19 órdenes. Del total de especies, 72% fueron residentes todo el año y 24%, de invierno. Por el tipo de alimentación, las terrestres insectívoras (52%) fueron las más abundantes, seguidas de las carnívoras (20%) y terrestres herbívoras (15%). El mayor número de especies (68%) estuvo asociado a vegetación ribereña. Esta región de Oaxaca alberga 16% de la riqueza de aves de México, entre ellas a nueve especies endémicas o cuasiendémicas de México y 12 en categorías de riesgo a nivel nacional o internacional, como el pato real (Cairina moschata), loro corona lila (Amazona finschi), loro cabeza amarilla (Amazona oratrix) y vireo de Bell (Vireo bellii). Recomendamos la protección de la vegetación ribereña y de las selvas como la mejor estrategia para la conservación de la avifauna.

Territorial behaviour and breeding in the Southern Antpipit Corythopis delalandi (Aves: Rhynchocyclidae) in southeastern Brazil

ABSTRACT The Southern Antpipit is a terrestrial insectivore passerine that ranges in the undergrowth of semideciduous forests in central South America. Despite the historical interest on its disputed systematic position, no detailed study about its natural history is available. In this paper, we studied its territorial and breeding biology in southeastern Brazil. We studied colour-banded birds and closely monitored the nests found, estimating the home range using two distinct methods, the Minimum Convex Polygon (MCP) and the Kernel Density Estimator (KDE). The nest (n = 4) is a dome, somewhat elliptical in shape and with a side entrance, placed on the forest litter. Its structural layer is built with unidentified vegetable fibres, leaf petioles and horsehair fungus, and the external decorative layer is built with dry leaves and mosses. No well-defined lining layer was observed. Two eggs are usually laid and incubation, done solely by the female, lasts for 17 days. Both parents feed the nestlings, which fledge when 14–15 days old. Our data, together with citizen science data, reveal that the breeding season extends from August to December, therefore from the end of the dry season to the middle of the wet season. A mean home range size of 1.08 ± 0.44 ha was estimated using the MCP and of 1.42 ± 0.47 ha using the KDE (n = 9). The home range is defended against conspecifics, thus characterising an all-purpose territory, which is hold throughout the year, possibly during the entire reproductive life of the male.

Taxonomic nestedness based on guilds? Bird assemblages of the Jardines de la Reina National Park, Cuba, as study case

Nestedness is a widely known structuring model in insular and fragmented biotas that has often been assessed, but most studies to date have used a taxonomic approach. However, the relevance of an approach using functional groups has become increasingly highlighted in community ecology research. In this study, we evaluated the occurrence of nested structure in the Jardines de la Reina National Park bird assemblages as a whole, and its trophic guilds by following three different grouping criteria. We constructed species presence–absence matrices for each guild and estimated the degree of nestedness with the metric based on the overlap and decreasing fill, assessing its significance by means of two null models. Overall bird assemblage was significantly nested (NODF = 76.99; p = 0.01) whereas terrestrial insectivores (NODF = 81.32) and insectivores (NODF = 80.04) were the only trophic guilds (out of 19) that showed significant nestedness (p ≤ 0.01). These results could provide evidence of the structural and functional cohesion of avifauna at the study site, especially among its insect–eating taxa. Taxonomic nestedness based on a guilds approach may help identify suitable conservation strategies for avian communities inhabiting naturally fragmented areas such as the Jardines de la Reina National Park.