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Abstract Background Ecological segregation allows populations to reduce competition and coexist in sympatry. Using as model organisms two closely related gadfly petrels endemic to the Madeira archipelago and breeding with a two month allochrony, we investigated how movement and foraging preferences shape ecological segregation in sympatric species. We tested the hypothesis that the breeding allochrony is underpinned by foraging niche segregation. Additionally, we investigated whether our data supported the hypothesis that allochrony is driven by species-specific adaptations to different windscapes. Methods We present contemporaneous tracking and stable isotopes datasets for Zino’s (Pterodroma madeira) and Desertas (Pterodroma deserta) petrels. We quantified the year-round distribution of the petrels, characterised their isotopic niches and quantified their habitat preferences using machine learning (boosted regression trees). Hidden-Markov-models were used to investigate the effect of wind on the central-place movement speed, and a simulation framework was developed to investigate whether each species breeds at times when the windscape is most favourable to sustain their trips. Results Despite substantial spatial overlap throughout the year, the petrels exhibited diverging isotopic niches and habitat preferences during breeding. Both species used a vast pelagic region in the North Atlantic, but targeted two different mesopelagic ecoregions and showed a preference for habitats mostly differing in sea surface temperature values. Based on our simulation framework, we found that both species would perform trips of similar speed during the other species’ breeding season. Conclusions The different breeding schedules between the species are underpinned by differences in foraging habitat preferences and adaptation to the local environment, rather than to the windscape. Nevertheless, the larger Desertas petrels exploited significantly windier conditions, potentially unsustainable for the smaller Zino’s petrels. Furthermore, due to larger mass and likely higher fasting endurance, Desertas petrels engaged in central-place-foraging movements that covered more ground and lasted longer than those of Zino’s petrels. Ultimately, patterns of ecological segregation in sympatric seabirds are shaped by a complex interplay between foraging and movement ecology, where morphology, foraging trip regulation and fasting endurance have an important– yet poorly understood– role.

Niche theory predicts that similar species cannot occupy the same geographical space when resources are limited. Sympatric seabirds, such as auks, are ideal models for investigating niche differentiation because they share life history traits and form breeding colonies that rely on common prey items. Auk differentiation may be driven by variations in body mass and wing size, diving capacity, and visual acuity leading each species to forage at different distances, depths, or times of day, respectively. However, previous auk studies have produced diverse results, leaving us with an incomplete understanding of their foraging differentiation across spatial, environmental, and temporal dimensions. In 2021, we tested niche differences at the Mingan Archipelago National Park Reserve, Québec, Canada (50°11′ N, 63°13′ W) by utilizing GPS and time and depth recorders to track the positions of breeding Atlantic puffins (Fratercula arctica), razorbills (Alca torda), and common murres (Uria aalge), which were then paired with environmental data. There was high niche overlap in geographical foraging areas, with auk wing size and mass not appearing to influence their foraging distance. Instead, auk foraging was partitioned over different depths and times of day. Although razorbills and puffins generally exploited shallow foraging areas, puffin foraging activity occurred in deeper waters and at different times of day than razorbills. Murres foraged in the deepest benthic areas and were the only species to forage at night. Our study therefore suggests that auks could be facilitating their coexistence by exhibiting temporal and spatial differences in their foraging behaviours and locations. [ABSTRACT FROM AUTHOR]

Understanding habitat selection patterns in congeneric species has raised special interest due to its importance when designing conservation strategies for the species. We analysed reproductive habitat selection of three coexisting warbler species in the eastern Iberian Peninsula. We detected the individuals by their vocalizations at 40 listening points in two study areas (Carcaixent and Alcoy). We used satellite images to identify different vegetation types and their availability. Reproductive habitat selection was analysed by the Ivlev selectivity index and a compositional analysis. In addition, we determined the effect of different habitat variables (dominant vegetation, vegetation height, cover and site) on the presence of the species fitting a binomial GLM with logistic linking function. We found that the Sardinian Warbler (Curruca Melanocephala) selected scrub-dominated areas; while the Dartford Warbler (C. undata) preferred areas with low (<50%) vegetation cover; and the Subalpine Warbler (C. cantillans) was present in areas with scrubs and low (<50%) vegetation cover, avoiding crops. The compositional analysis showed that the species used different vegetation types, in relation to their availability and that the selection differed between species. The Sardinian Warbler was the only species which showed spatial variation in reproductive habitat selection. Our results evidence that the studied warbler species select and avoid different types of vegetation in relation to their specific requirements and the present habitat structure. This represents valuable information to understand the composition of local communities and the reproductive habitat selection of the studied species. [ABSTRACT FROM AUTHOR]

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Background: Ecological segregation allows populations to reduce competition and coexist in sympatry. Using as model organisms two closely related gadfly petrels endemic to the Madeira archipelago and breeding with a two month allochrony, we investigated how movement and foraging preferences shape ecological segregation in sympatric species. We tested the hypothesis that the breeding allochrony is underpinned by foraging niche segregation. Additionally, we investigated whether our data supported the hypothesis that allochrony is driven by species-specific adaptations to different windscapes. Methods: We present contemporaneous tracking and stable isotopes datasets for Zino's (Pterodroma madeira) and Desertas (Pterodroma deserta) petrels. We quantified the year-round distribution of the petrels, characterised their isotopic niches and quantified their habitat preferences using machine learning (boosted regression trees). Hidden-Markov-models were used to investigate the effect of wind on the central-place movement speed, and a simulation framework was developed to investigate whether each species breeds at times when the windscape is most favourable to sustain their trips. Results: Despite substantial spatial overlap throughout the year, the petrels exhibited diverging isotopic niches and habitat preferences during breeding. Both species used a vast pelagic region in the North Atlantic, but targeted two different mesopelagic ecoregions and showed a preference for habitats mostly differing in sea surface temperature values. Based on our simulation framework, we found that both species would perform trips of similar speed during the other species' breeding season. Conclusions: The different breeding schedules between the species are underpinned by differences in foraging habitat preferences and adaptation to the local environment, rather than to the windscape. Nevertheless, the larger Desertas petrels exploited significantly windier conditions, potentially unsustainable for the smaller Zino's petrels. Furthermore, due to larger mass and likely higher fasting endurance, Desertas petrels engaged in central-place-foraging movements that covered more ground and lasted longer than those of Zino's petrels. Ultimately, patterns of ecological segregation in sympatric seabirds are shaped by a complex interplay between foraging and movement ecology, where morphology, foraging trip regulation and fasting endurance have an important– yet poorly understood– role. [ABSTRACT FROM AUTHOR]

• Abundant record of Macaronichnus segregatis degiberti in a Tortonian package has been studied. • Storm-wave dominated, tide-influenced shoreface/subtidal to offshore transition setting is interpreted. • Possible contemporaneous presence of? M.s. maeandriformis is observed for the first time. • Fluid muds favor the meeting point of ecologically 'incompatible' trace makers. Macaronichnus is a key trace fossil in palaeoceanographic, palaeoclimatic, and petroleum exploration research. Small ichnosubspecies such as Macaronichnus segregatis segregatis , M. s. lineiformins , M. s. maeandriformis and M. s. spiriformis , typically occur in wave-dominated foreshore sands where large M. s. degiberti was never found. The latter shows a wide environmental distribution, occurring in sandy deposits of tidal channels, tidal bar sand sandridges, tidal-flat sand sheets, shorefaces, bioturbated sandy shelf, shelf storm-sheets, shelf sand ridges, and upper slopes. Small M. segregatis and large M. s. degiberti have not been observed to date due the ecological segregation of the tracemakers. An abundant record of large M. s. degiberti in a Tortonian (Late Miocene) mixed carbonate-siliciclastic unit from the Betic Cordillera (southern Spain) has been studied. Occurrence of M. s. degiberti is the result of the interaction of tidal and waves, storm influenced environment determining high-energy conditions and associated palaeoenvironmental parameters as shifting substrates, organic matter availability, and oxygenated pore and bottom-waters. Locally, associated to M. s. degiberti appear small, sinuous traces infilled by light material that were originally assigned to M. s. maeandriformis , and very rare M. s. spiriformis. However, the absence of the typical rim of Macaronichnus avoid a conclusive assignment. The coexistence of both small traces (? M. s. maeandriformis) and large M. s. degiberti is identified in the deposits underlying mudstone layers, revealing the importance of mud deposition during tidal slack water intervals or linked to fluid mud events favouring the co-occurrence of the trace makers of both Macaronichnus ichnosubespecies. This fact would have significant palaeobiological and palaeoecological implications, and could be the first record of both ichnosubspecies in the same intervals. [ABSTRACT FROM AUTHOR]

Related species often engage in abutting or overlapping contact zones with various strengths of interspecific competition. Biotic interactions such as these preclude the registration of the full profile of environmental variables that would describe the otherwise larger species ranges. Here, I advocate to forego full range species distribution modelling and instead focus on the ecography of the contact zone, for example with 'two-species distribution models' (TSDMs), in which presence data are contrasted against the background of environmental data. The newts Triturus cristatus and Triturus marmoratus meet in the west of France. A countrywide TSDM suggests that the contact zone of the species is located at a climatic gradient, in line with their north-eastern vs. south-western ranges. The species are also ecologically segregated by elevation and forestation, which is in line with a documented movement of the contact zone caused by hedgerow removal in lowland areas. Hindcasts for the Holocene suggest that the species contact zone was positioned at either the same place as at present or more to the south, depending on the amount of forestation. A forecast under climate warming predicts a fast movement to the north, but this scenario is deemed unrealistic. One reason is that recent habitat loss compromises dispersal and range expansion. Other species pairs to which TSDMs have been applied are listed for comparison. [ABSTRACT FROM AUTHOR]

Climate-induced range overlap can result in novel interactions between similar species and potentially lead to competitive exclusion. The West Antarctic Peninsula (WAP) is one of the most rapidly warming regions on Earth and is experiencing a poleward climate migration from a polar to subpolar environment. This has resulted in a range expansion of the ice-intolerant gentoo penguins (Pygoscelis papua) and a coincident decrease in ice-obligate Adélie penguins (P. adeliae) near Palmer Station, Anvers Island, WAP. Ecologically similar species that share a limited prey resource must occupy disparate foraging niches in order to co-exist. Therefore, we determined the extent of foraging and dietary niche segregation between Adélie and gentoo penguins during the austral breeding season near Palmer Station. This research was conducted across six breeding seasons, from 2009 to 2014, which allowed us to investigate niche overlap in the context of interannual resource variability. Using biotelemetry and diet sampling, we found substantial overlap in the diets of Adélie and gentoo penguins, who primarily consumed Antarctic krill (Euphausia superba); however, our results showed that Adélie and gentoo penguins partitioned this shared prey resource through horizontal segregation of their core foraging areas. We did not find evidence that Antarctic krill were a limiting resource during the breeding season or that climate-induced sympatry of Adélie and gentoo penguins resulted in competition for prey or caused the subsequent differing population trajectories. This apparent absence of resource competition between Adélie and gentoo penguins throughout this study implies that current population trends in this region are governed by other biological and physical factors. Our results highlight the importance of understanding the mechanistic processes that influence top predator populations in the context of climate-driven ecosystem shifts.

Abstract Background Animal communities have complex patterns of ecological segregation at different levels according to food resources, habitats, behavior, and activity patterns. Understanding these patterns among the community is essential for the conservation of the whole ecosystem. However, these networks are difficult to study nowadays, due to anthropic disturbances and local extinctions, making it difficult to conclude if segregation patterns are natural or human-induced. We studied ecological segregation in a community of large and mid-sized mammals in the Great Gobi Desert, a remote arid area free from recent extinctions and human disturbances. Activity patterns of 10 sympatric mammal species were monitored around 6 waterholes through camera-trapping over a two-year period, and analyzed them primarily through circular statistics. Results Complex patterns of spatial, seasonal, and daily segregation were found. Overlap in seasonal activity was detected in only 3 of the 45 possible pairs of species. Four species used the waterholes all-year-round, while others peaked their activity during different periods. The Bactrian camel showed continuous daily activity, the grey wolf had bimodal activity, and the argali and Siberian ibex were diurnal, while the others had nocturnal peaks during different hours. Daily and spatial overlap were both detected in only 6 of the 45 pairs. Only one species pair (snow leopard and Eurasian lynx) showed an overlap at two levels: seasonal and daily. Climate and moon phase significantly affected the activity of certain species. Conclusions Altogether, the results showed complex patterns of ecological segregation at different levels in the use of the key resource in arid environments: waterholes. These results are important for understanding the biology of these species under natural conditions, as well as potential changes in altered ecosystems, and may help to design conservation strategies.

Morphological variation in biological structures may be driven by genetic and environmental factors, such as inter- and intraspecific competition for resources. In seabirds, although the bill is also involved in vocalization, olfaction, sexual selection and defence, the main drivers of high morphological plasticity in bill size and shape appear to relate primarily to diet and thus to niche differentiation. Here, we combined geometric morphometrics and comparisons of linear measurements as a precise tool for measuring shape variation in anatomical features, to investigate the differences among species and populations (island groups) in bill shape of three planktivorous petrels (Antarctic prion Pachyptila desolata, blue petrel Halobaena caerulea and thin-billed prion Pachyptila belcheri). Fieldwork was carried out in South Georgia (54° 0′ S, 38° 3′ W), Falkland (51° 42′ S, 57° 51′ W), Diego Ramírez (56° 31′ S, 68° 44′ W) and Kerguelen (49° 20′ S, 69° 20′ E) Islands, from 2010 to 2021. Results show that the bills of Antarctic prions were more robust and shorter, appropriate for filtering large amounts of small prey. Blue petrels and thin-billed prions had narrower and longer bills, effective for catching and tearing large single prey. Also, Antarctic prions and blue petrels from Kerguelen had longer and narrower bills than conspecifics from other colonies, which could potentially be explained by geographic variation in diet. In conclusion, prey availability and diversity appear to be important factors influencing variation in bill morphology. This study highlights the utility of geometric morphometrics for investigating bill shape variation in seabirds. Nevertheless, further studies are needed to better understand selective pressures leading to morphological variation of biological structures. [ABSTRACT FROM AUTHOR]

Introduction: Resource partitioning by promoting coexistence is essential to determine species richness and composition in natural communities. However, the partitioning of time has been questioned as a mechanism that promotes the coexistence of ecologically similar species. Objective: To determine the importance of the partitioning of time as a mechanism that promotes coexistence, we compared the activity patterns of tropical frugivorous bats. Methods: We captured bats with mist nets from sunset to sunrise in three study sites (tropical dry forest, wet forest, and rainforest) to calculate activity patterns of the species using Kernel density estimation. We used the superposition coefficient (Δ1) to compare activity patterns between (1) bat assemblages of study sites, (2) frugivorous species in the same site, and (3) populations of the same species among different sites. To determine whether the overlap in the activity patterns was related to the ecological similarity of species, we evaluated the association between Δ1 and similarity in abundances and body mass and phylogenetic closeness. Results: We found geographical variations in the overall activity patterns of the assemblages of the three localities. Likewise, we found variations in activity patterns between species at each study site and between populations in different study sites. Overlap in activity patterns tended to decrease as species were phylogenetically more closely related and similar in abundance and body size. Conclusions: Our results provide empirical support for the role of temporal segregation in activity patterns as a mechanism that promotes the coexistence of ecologically similar species in nature. [ABSTRACT FROM AUTHOR]

Background: Animal communities have complex patterns of ecological segregation at different levels according to food resources, habitats, behavior, and activity patterns. Understanding these patterns among the community is essential for the conservation of the whole ecosystem. However, these networks are difficult to study nowadays, due to anthropic disturbances and local extinctions, making it difficult to conclude if segregation patterns are natural or human-induced. We studied ecological segregation in a community of large and mid-sized mammals in the Great Gobi Desert, a remote arid area free from recent extinctions and human disturbances. Activity patterns of 10 sympatric mammal species were monitored around 6 waterholes through camera-trapping over a two-year period, and analyzed them primarily through circular statistics. Results: Complex patterns of spatial, seasonal, and daily segregation were found. Overlap in seasonal activity was detected in only 3 of the 45 possible pairs of species. Four species used the waterholes all-year-round, while others peaked their activity during different periods. The Bactrian camel showed continuous daily activity, the grey wolf had bimodal activity, and the argali and Siberian ibex were diurnal, while the others had nocturnal peaks during different hours. Daily and spatial overlap were both detected in only 6 of the 45 pairs. Only one species pair (snow leopard and Eurasian lynx) showed an overlap at two levels: seasonal and daily. Climate and moon phase significantly affected the activity of certain species. Conclusions: Altogether, the results showed complex patterns of ecological segregation at different levels in the use of the key resource in arid environments: waterholes. These results are important for understanding the biology of these species under natural conditions, as well as potential changes in altered ecosystems, and may help to design conservation strategies. [ABSTRACT FROM AUTHOR]

Seabirds inhabiting vast water masses provide numerous examples where opposing phenomena, such as natal and breeding philopatry vs. vagility have dug cryptic taxonomic boundaries among closely related taxa. The taxonomy of little shearwaters of the North Atlantic Ocean (Little–Audubon's shearwater complex, Puffinus assimilis – lherminieri) still remains unclear, and complementary information on non-breeding distributions and at-sea behaviour becomes essential to unravel divergent local adaptations to specific habitats. Using miniaturized light-level geolocators from seven study areas in the North Atlantic, we evaluate the spatial and habitat segregation, estimate the timing of their key life-cycle events and describe the at-sea behaviour of three taxa of these little shearwaters year-round to distinguish ecological patterns and specializations that could ultimately unravel potential lineage divergences. We also assess morphometric data from birds that were breeding at each study area to further discuss potential adaptations to specific habitats. Our results show that, while birds from different taxa segregated in space and habitats, they share ecological plasticity, similar annual phenology and diel foraging behaviour. These ecological inconsistencies, while defining the evolutionary stressors faced by these taxa, do not suggest the existence of three Evolutionary Significant Units. However, they confirm the recent evolutionary divergence among the three little shearwaters of the North Atlantic. [ABSTRACT FROM AUTHOR]

Forest stands of Pinus yunnanensis Franch in southwestern China are seriously damaged by several bark living insect pests. These pests commonly exist in the same host tree and exploit limited phloem resources. In this study, we hypothesized that sympatric pests would occupy different ecological niches to reduce interspecific competition, and their coordinated attack would aggravate the tree vigor decline of P. yunnanensis. To quantify the ecological niches, we used a sampling method involving three dimensional divisions of tree resource states: (a) sample plot dimension (to evaluate the extent of pest colonization at plot scale), (b) trunk height dimension, and (c) tree vigor dimension. Those attacked pine canopies and colonized trunks were analysed in the field study. The results showed that Tomicus minor and Tomicus yunnanensis both widely and uniformly distributed in lightly, moderately and heavily damaged canopies while they aggregated on particular trunks of dying and withered trees. Lower and middle trunk sections (1–4 m) were mainly occupied by Monochamus alternatus and T. minor, yet T. yunnanensis dominated the upper parts (5–6 m). There was an overlap of the pine shoot beetles in the middle sections (2–4 m), whereas all three species were ecologically segregated in other trunk sections. During the shoot feeding phase, tree vigor declined with pine shoot beetles' increasing shoot feeding density. They coexisted in the same host tree, while M. alternatus only attacked dying and withered tree trunks, causing a greater infestation. Colonization of pine shoot beetle then followed by M. alternatus could be the major causes of tree mortality. This study highlights the resource utilization pattern of sympatric bark living insect pests corresponding with tree vitality. Those findings would help to understand the mechanisms of pest outbreak in P. yunnanensis ecosystem and provide potential guidance for developing an early monitoring pest warning system. [ABSTRACT FROM AUTHOR]

A "suture zone" is a zone where geographically otherwise separated faunas meet. New Guinea's Bird's Neck Isthmus potentially constitutes a double suture zone, where the avifaunas of New Guinea's northern and southern lowlands (otherwise separated by the Central Dividing Range), and also the avifaunas of the Vogelkop Peninsula to the west and New Guinea's main body to the east, are in contact. The Isthmus is a north/south corridor only 60 km long and only 160 m in maximum elevation. The watershed lies much closer to the north coast than to the south coast. We surveyed the northern 60% of the Isthmus's interior, previously unexplored ornithologically, to just south of Lake Yamur. We observed 178 species on the Isthmus, including some disproportionately in hilly terrain and others in flat terrain, and identified visually or vocally informative Isthmus populations of 30 geographically variable species. At the middle of the Isthmus, southern forms prevail over northern forms, and both western and eastern forms are represented. At least eight southern populations and one northern population extend across the Isthmus to the opposite coast. We present examples of hybridization, incipient speciation, achievement of sympatry, and ecological segregation. Three species confined to the mountains on the northern watershed descend to or near sea level on or near the Isthmus. We report the first ornithological survey of the waterbirds of Lake Yamur, Indonesian New Guinea's third largest lowland lake. [ABSTRACT FROM AUTHOR]

Variation in morphological structures may indicate the existence of ecological differences between species or sexes. In birds, the bill is one of the structures most affected by selection pressures because it is directly involved with several biological functions, particularly the acquisition of food. In this study, we combined geometric morphometrics and comparisons of linear measurements to assess the presence of sexual dimorphism and differences in bill shape and size of four species of abundant zooplanktivorous seabirds that coexist during their breeding season in Southern Ocean ecosystems [blue petrel (Halobaena caerulea), Antarctic prion (Pachyptila desolata), common diving petrel (Pelecanoides urinatrix) and South Georgia diving petrel (P. georgicus)]. The results showed that bills of Antarctic prion and blue petrel differed noticeably in size and shape from those of the two diving petrels, whereas those of common diving and South Georgian diving petrels overlapped in bill shape. These differences may be due to diet segregation or factors such as diving strategy, vocalizations or olfactory development. In addition, there was sexual dimorphism in bill shape or size in all four species. However, we could not directly attribute these differences to selection pressures because of the lack of studies comparing feeding ecology between sexes in these seabirds. These results reveal relationships between the bill shape and key factors of the ecology of these species, and demonstrate the usefulness of geometric morphometrics for detecting interspecific and sexual differences in species of otherwise sexually monomorphic petrels. This study combines geometric morphometrics and comparisons of linear measurements, to assess the presence of sexual dimorphism and differences in bill shape and size of four species of abundant zooplanktivorous seabirds, which coexist during their breeding season in Southern Ocean ecosystems. The results showed that bills of Antarctic prion and blue petrel differed noticeably in size and shape from those of the two diving petrels, whereas those of common diving and South Georgian diving petrels overlapped in bill shape. These differences may be due to diet segregation or factors such as diving strategy, vocalizations or olfaction development. [ABSTRACT FROM AUTHOR]

Song structure can be constrained by morphological characters such as beak size. Studies have shown that songbirds with larger beaks produce songs with a lower frequency, narrower frequency range and lower note rates than birds with smaller beaks. We tested whether beak volume and bite force constrain song parameters in three Neotropical seedeaters that show a gradient of beak size and force (Sporophila beltoni, S. caerulescens and S. hypoxantha). We also determined the relationship between body size and song structure. We evaluated the song structure of these species, measuring differences that may help them to segregate the acoustic space, since they occur in sympatry. These birds can be predicted to segregate the acoustic space to reduce overlapping of their songs, which is a possible result of the force of sexual selection. Individuals of each species had their beaks and bite forces measured and their own territorial songs recorded in the field. Only S. caerulescens showed a positive relationship between beak volume and song parameters (maximum frequency and frequency bandwidth). No song parameters showed an association with bite force or body size. The use of acoustical space seemed to be unique to each species with respect to note rate and song duration. Sporophila beltoni and S. hypoxantha showed the most differences from each other in all song parameters analysed. In contrast to other studies of finch species with conical beaks, our findings suggested that for these three species, beak volume and bite force do not limit the song structure. [ABSTRACT FROM AUTHOR]

An ecological segregation of five species of thrushes (Turdus pilaris, T. merula, T. iliacus, T. philomelos, T. viscivorus) in Volyn Polissia was studied. For the overwhel­ming majority of ecological characteristics, the most similar are Song Thrush and Blackbird (DE = 38.36). They have similar biotopical preferences in forest and forest edges habitats, almost the same nesting height (1.58 and 2.00 m, accordingly), similar feed rations. All this gives us the reason to conclude minimal ecological segregation of Song Thrush and Blackbird in the forest ecosystems of Volyn Polissia. At the same time, they avoid high ecological competition due to different ratios in thrushes complexes in the certain territories [22, 23], structure of nesting habitats [23]. Fieldfare often settled near open habitats by meadows and forest edges, build the nests on the prevailing tree species within the habitat. Food preferences associated primarily with the composition of the feed, the majority of which is produced out of the forest habitats. Mistle Thrush prefers medieval pine forests without undergrowth (73 % of all habitats) with poor forest floor, that made different strategy of food use and obtaining among all presented thrushes species. It was established that among the five studied species of thru­shes Redwing and Mistle Thrush has the highest value of ecological specialization and segregation.

Amongst migratory species, it is common to find individuals from different populations or geographical origins sharing staging or wintering areas. Given their differing life histories, ecological theory would predict that the different groups of individuals should exhibit some level of niche segregation. This has rarely been investigated because of the difficulty in assigning migrating individuals to breeding areas. Here, we start by documenting a broad geographical gradient of hydrogen isotopes ( δ H) in robin Erithacus rubecula feathers across Europe. We then use δ H, as well as wing-tip shape, as surrogates for broad migratory origin of birds wintering in Iberia, to investigate the ecological segregation of populations. Wintering robins of different sexes, ages and body sizes are known to segregate between habitats in Iberia. This has been attributed to the despotic exclusion of inferior competitors from the best patches by dominant individuals. We find no segregation between habitats in relation to δ H in feathers, or to wing-tip shape, which suggests that no major asymmetries in competitive ability exist between migrant robins of different origins. Trophic level (inferred from nitrogen isotopes in blood) correlated both with δ H in feathers and with wing-tip shape, showing that individuals from different geographic origins display a degree of ecological segregation in shared winter quarters. Isotopic mixing models indicate that wintering birds originating from more northerly populations consume more invertebrates. Our multi-scale study suggests that trophic-niche segregation may result from specializations (arising in the population-specific breeding areas) that are transported by the migrants into the shared wintering grounds. [ABSTRACT FROM AUTHOR]

Ecological theory predicts that animals with similar foraging strategies should not be able to co‐exist without segregating either in space, time or diet. In communities, intra‐specific competition is thought to be more intense than the competition among species, because of the lack of niche partitioning between conspecifics. Hence, while different seabird species can overlap in their foraging distribution, intra‐specific competition can drive the neighboring populations of the same species to spatial segregation of foraging areas. To investigate ecological segregation within and among species of diving seabirds, we used a multi‐species GPS‐tracking approach of seabirds of four species on a small island in the Southwest Atlantic. The present study goes beyond previous work by analyzing simultaneous effects of species and colonies. We observed strikingly strong spatial foraging segregation among birds of the same species, breeding in colonies as close as 2 km from each other. Conspecifics from neighboring colonies used foraging places adjacent to their own colony, and there was little or no overlap with birds from the other colony. A zone with increased predator concentration was completely avoided during foraging trips, likely contributing to the spatial segregation. In addition to spatial segregation, we also observed intra‐specific differences in other components of foraging behavior, such as time of day, dive depth and diet. These were most likely caused by optimal foraging of individuals in relation to habitat differences on a local scale, leading to a complex pattern of interactions with environmental covariates, in particular foraging daytime, foraging water layer temperature and depth, distance to coast and bathymetric depth of foraging areas. As mechanisms leading to the spatial segregation we propose a combination of optimal foraging and avoidance of predation.

Individuals within populations can use different resources, leading to ecological segregation and niche variation. This segregation could have direct impacts on the migratory strategy or breeding success, thus affecting the overall population and community dynamics and, ultimately, survival. In this study, we assessed the inter-annual and within individual foraging ecology of an endemic and highly threatened seabird species, the Desertas petrel P terodroma deserta, during the breeding and non-breeding phases. We combined 54 annual tracks (26 individuals; 2009-2013) obtained with light-level loggers (Global Location Sensing or GLS loggers) with stable isotope analyses (δ15N and δ13C) of blood (plasma and cells) and feathers. Wide-ranging tracking data show that this species is a generalist predator, able to adapt to very different habitats. All birds remained faithful to their selected non-breeding areas over the years leading to very high spatial, temporal and trophic consistency among years (i.e. usually with intra-correlation coefficient values, which is an index of repeatability of > 40%). During both the breeding and non-breeding seasons, individual birds showed narrow and segregated isotopic niches, indicating a high level of specialization and limited choice of prey and habitats. The conservation of a seabird with such a dispersive (species-level) yet consistent (individual-level) non-breeding distribution pattern represents a challenge in marine policy terms. On the one hand, such a consistent temporal and spatial pattern will help with defining core areas for conservation, which could be protected through specific management measures or by the establishment of marine protected areas. Yet, their relatively large size (on average 4000 km2) and extent over both national and international waters, where different legislative frameworks apply, will require the coordinated action by many nations, international organizations and multilateral environmental agreements. [ABSTRACT FROM AUTHOR]

Understanding the extent of interspecific hybridization and how ecological segregation may influence hybridization requires comprehensively sampling different habitats over a range of life history stages. Arctic char ( Salvelinus alpinus) and Dolly Varden ( S. malma) are recently diverged salmonid fishes that come into contact in several areas of the North Pacific where they occasionally hybridize. To better quantify the degree of hybridization and ecological segregation between these taxa, we sampled over 700 fish from multiple lake (littoral and profundal) and stream sites in two large, interconnected southwestern Alaskan lakes. Individuals were genotyped at 12 microsatellite markers, and genetic admixture ( Q) values generated through Bayesian-based clustering revealed hybridization levels generally lower than reported in a previous study (<0.6% to 5% of samples classified as late-generation hybrids). Dolly Varden and Arctic char tended to make different use of stream habitats with the latter apparently abandoning streams for lake habitats after 2-3 years of age. Our results support the distinct biological species status of Dolly Varden and Arctic char and suggest that ecological segregation may be an important factor limiting opportunities for hybridization and/or the ecological performance of hybrid char. [ABSTRACT FROM AUTHOR]

Aim Species that breed sympatrically often occupy different foraging niches to mitigate competition for prey. When resource availability declines at the end of the breeding season, some animals migrate to regions with more favourable environmental conditions. When these life-history traits combine, foraging habitat preferences may continue to influence migration patterns and habitat utilization. The Bering Sea is home to the red-legged kittiwake ( RLKI), Rissa brevirostris, which is endemic, and the black-legged kittiwake ( BLKI), Rissa tridactyla, which has a circumpolar breeding distribution. Since the 1970s, numbers of RLKIs at the largest colony have declined and then recovered, whilst the BLKI population has remained stable. Knowledge of the migration ecology of kittiwakes is key to understanding differences in population trajectories, and predicting possible future responses of these species to climate change. Location Pribilof Islands, Bering Sea, subarctic North Pacific. Methods Using geolocation loggers, we tracked adult RLKIs and BLKIs during their non-breeding migrations. We used iterative methods to assess suitable sample sizes for determining space use. Kittiwakes are surface foragers; therefore we used wet-dry data to distinguish active foraging behaviour and to test the species' responses to environmental conditions. Stable isotope ratios of feathers grown during the non-breeding period were used to assess dietary niche. Results RLKIs remained largely in the Bering Sea, where they experienced colder conditions and shorter days; individual birds used multiple habitats, including the continental shelves, the sea-ice edge and pelagic waters. In contrast, BLKIs migrated to the subarctic North Pacific, where they dispersed laterally across the basin; the majority of birds travelled to the western subarctic. RLKIs spent less time actively foraging than BLKIs, and consumed higher trophic-level prey. Main conclusions The disparate wintering ranges and foraging behaviour of BLKIs and RLKIs suggest distinct environmental factors drive variation in overwinter survival. A strong association with sea ice, and specialization both in diet and foraging behaviour, may make RLKIs particularly vulnerable to climatic change. [ABSTRACT FROM AUTHOR]

Aim Pelagic seabirds exploit large areas of ocean when acting as central-place foragers during the breeding season, and ranges are even more extensive outside the breeding period. Spatial niche partitioning is known to occur among species that breed sympatrically, but is less apparent during the non-breeding period when there is increased potential for overlap among closely related species from neighbouring island groups. This applies to several species of prion, Pachyptila spp., in the Southern Ocean; although extremely abundant, their at-sea distribution was virtually unknown because they are difficult to distinguish while at sea. To understand spatial niche partitioning at large scales, we investigated the year-round distribution of thin-billed prions ( Pachyptila belcheri) from the Falkland Islands (Islas Malvinas) and Antarctic prions ( Pachyptila desolata) from South Georgia. Location South Atlantic Ocean. Methods Recently, geolocation devices have become small enough to be deployed on small seabirds. During 2009-10, we tracked 20 thin-billed prions and 9 Antarctic prions with miniaturized geolocators. We applied ecological niche models to compare environmental conditions in the habitat utilized year-round. Results We show that two prion species from the south-west Atlantic Ocean have divergent patterns of migration, and that this has resulted in nearly complete spatial segregation (0-5% overlap by month in the 95% kernel density polygons). Nineteen of 20 thin-billed prions migrated to an area > 3000 km east of their breeding site, whereas all Antarctic prions migrated a much shorter distance, and to the north-west. The non-breeding distribution of thin-billed prions included the waters around South Georgia, but only when the Antarctic prions were absent. The models highlighted large differences in the realized niche between the two species, and between the habitat characteristics of breeding and non-breeding areas of thin-billed and Antarctic prions. Main conclusions Our results are consistent with the prediction that spatial niche partitioning occurs at large scales, allowing the co-existence of related species. The methods applied here will enable predictive maps of the distributions of other prion populations to be created, once data become available from other breeding sites in the Southern Ocean. [ABSTRACT FROM AUTHOR]

The article discusses research on the putative segregation of two yellow wagtail taxa by breeding habitat in Western Siberia and its implications for Motacilla flava taxonomy. It references a study by H. Herman van Oosten and Alexander A. Emtsev, published in a 2013 issue of "Ardea." The researchers describe the breeding habitat of thunbergi and beema in European Russia and Western Siberia to determine whether breeding habitat could be an ecological factor for sub-specific segregation in such breeding range. They determined that large scale segregated breeding due to varied habitat preferences could impact taxonomic interpretations within the Motacilla flava complex.

The expression of two or more discrete phenotypes amongst individuals within a species (morphs) provides multiple modes upon which selection can act semi-independently, and thus may be an important stage in speciation. In the present study, we compared two sympatric morph systems aiming to address hypotheses related to their evolutionary origin. Arctic charr in sympatry in Loch Tay, Scotland, exhibit one of two discrete, alternative body size phenotypes at maturity (large or small body size). Arctic charr in Loch Awe segregate into two temporally segregated spawning groups (breeding in either spring or autumn). Mitochondrial DNA restriction fragment length polymorphism analysis showed that the morph pairs in both lakes comprise separate gene pools, although segregation of the Loch Awe morphs is more subtle than that of Loch Tay. We conclude that the Loch Awe morphs diverged in situ (within the lake), whereas Loch Tay morphs most likely arose through multiple invasions by different ancestral groups that segregated before post-glacial invasion (i.e. in allopatry). Both morph pairs showed clear trophic segregation between planktonic and benthic resources (measured by stable isotope analysis) but this was significantly less distinct in Loch Tay than in Loch Awe. By contrast, both inter-morph morphological and life-history differences were more subtle in Loch Awe than in Loch Tay. The strong ecological but relatively weak morphological and life-history divergence of the in situ derived morphs compared to morphs with allopatric origins indicates a strong link between early ecological and subsequent genetic divergence of sympatric origin emerging species pairs. The emergence of parallel specialisms despite distinct genetic origins of these morph pairs suggests that the effect of available foraging opportunities may be at least as important as genetic origin in structuring sympatric divergence in post-glacial fishes with high levels of phenotypic plasticity. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ••, ••-••. [ABSTRACT FROM AUTHOR]

1. Species potentially competing for the same resource are considered to be able to co-exist if they occupy different niches. In an apparent example of this, Adélie, Chinstrap and Gentoo penguins all feed predominantly on krill Euphausea superba at certain sites of sympatry in Antarctica and are proposed to exploit different niche hyper-volumes via differential area and depth utilization. 2. Patterns of foraging for 49 of these penguins breeding in sympatry were assessed using dead-reckoning loggers to examine foraging niche overlap. 3. Area use overlaps were 0·29 for Adélie ∩ Chinstrap, 0·44 for Adélie ∩ Gentoo, and 0·40 for Chinstrap ∩ Adélie and depth use overlaps were 0·69 for Adélie ∩ Chinstrap, 0·48 for Adélie ∩ Gentoo, and 0·52 for Chinstrap ∩ Gentoo Penguins. 4. Foraging efficiency was greatest for Adélie Penguins diving near surface waters (0–15 m) while Chinstraps were most efficient at medium depths (15–60 m) and Gentoo Penguins most efficient at deeper depths (> 60 m). There appear to be physiological reasons for this. Penguins primarily exploited those depths where they were most efficient. 5. The overlap for foraging periods was 0·47 for Adélie ∩ Chinstrap, 0·26 for Adélie ∩ Gentoo, and 0·40 for Chinstrap ∩ Gentoo Penguins. Chinstraps foraged primarily at night, Gentoos during the morning and Adélies in the afternoon. Temporal differences in foraging may result in the three species exploiting krill at those depths where it is best adapted to pursue it, this being mediated by the diel vertical migration of krill. 6. Integration of all measured parameters together gives minimal overlap between species with total overlaps of 0·09 for Adélie ∩ Chinstrap, 0·05 for Adélie ∩ Gentoo, and 0·08 for Chinstrap ∩ Gentoo Penguins so it appears that these penguins conform to conventional theory in avoiding competition in areas of sympatry. However, a model incorporating prey movement between hyper-volumes indicates that penguins may still compete, even in the virtual absence of hyper-volume overlap. 7. This study shows that Pygoscelid penguin do indeed exploit different hypervolumes in areas of sympatry but that such exploitation of different niches by sympatric species feeding on a common resource does not necessarily result in reduced competition if the mobility of prey is high. [ABSTRACT FROM AUTHOR]

When species with similar morphological and ecological characteristics occupy the same habitat, selection should minimize resource competition and promote coexistence by means of spatial partitioning. Competing species might exploit resources at different times or specialize in distinct resources. From July 2005 through May 2006 we examined the niche axes of two endemic sympatric desert species, Syspira tigrina Simon 1885 and Syspira longipes Simon 1885 in the State of Baja California Sur, looking for evidence that coexistence is fostered by differences in choice of microhabitat, temporal activity, occupation of space, or size. The results show high monthly microhabitat overlap (> 0.9). However, we found subtle differences in temporal activity and marked differences in juvenile and male body size, as well as some evidence of mutual spatial segregation. We conclude that body size and spatial segregation appear to be the dominant niche axes that facilitate coexistence of these species. [ABSTRACT FROM AUTHOR]

Elephants ( Loxodonta africana) exhibit pronounced sexual dimorphism, and in this study we test the prediction that the differences in body size and sociality are significant enough to drive divergent foraging strategies and ultimately sexual segregation. Body size influences the foraging behaviour of herbivores through the differential scaling coefficients of metabolism and gut size, with larger bodied individuals being able to tolerate greater quantities of low-quality, fibrous vegetation, whilst having lower mass-specific energy requirements. We test two distinct theories: the scramble competition hypothesis (SCH) and the forage selection hypothesis (FSH). Comprehensive behavioural data were collected from the Pongola Game Reserve and the Phinda Private Game Reserve in South Africa over a 2.5-year period. The data were analysed using sex as the independent variable. Adult females targeted a wider range of species, adopted a more selective foraging approach and exhibited greater bite rates as predicted by the body size hypothesis and the increased demands of reproductive investment (lactation and pregnancy). Males had longer feeding bouts, displayed significantly more destructive behaviour (31% of observations, 11% for females) and ingested greater quantities of forage during each feeding bout. The independent ranging behaviour of adult males enables them to have longer foraging bouts as they experience fewer social constraints than females. The SCH was rejected as a cause of sexual segregation due to the relative abundance of low quality forage, and the fact that feeding heights were similar for both males and females. However, we conclude that the differences in the foraging strategies of the sexes are sufficient to cause spatial segregation as postulated by the FSH. Sexual dimorphism and the associated behavioural differences have important implications for the management and conservation of elephant and other dimorphic species, with the sexes effectively acting as distinct “ecological species”. [ABSTRACT FROM AUTHOR]

Populations of the ‘continental’ Great Cormorant P. c. sinensis have expanded from north-eastern Europe towards the western part of the range of the ‘marine’ P. c. carbo breeding in the United Kingdom and France. The aim of the study was to test the hypothesis of ecological segregation between subspecies by analysing the structuring of the European populations. Sequencing the mtDNA of 231 birds belonging to 20 colonies revealed 38 haplotypes based on 25 polymorphic sites (5.76% sequence divergence). P. c. sinensis (‘S’) was well confirmed, but usual P. c. carbo formed two coastal populations, the real P. c. carbo ‘C’ mainly in the western part of the range (United Kingdom, coastal France), and also in Norway and Sardinia, and ‘N’, branched to the Japanese Cormorant P. capillatus and probably isolated by glaciations, mainly present in the Nordic range (Norway, but also on the coasts from Sweden to Brittany), we named P. c. norvegicus. In a variable position in the trees but close to C is a group of undetermined origin haplotypes, named U, also present in both traditional ranges. The new tree-nesting colonies in Brittany are clearly a mixture of S and the two clades C and N previously described as P. c. carbo, with a decreasing proportion of C+N between 1993 (67%), 1996 (60%) and 2002 (33%) for the pioneering Grand-Lieu colony. These results confirmed the current introgression of continental populations in the western range, with probable hybridization. Although the subspecies can switch habitats locally due to social behaviour and migrations, the ecological segregation between the two usual subspecies appears to be largely confirmed in Europe. [ABSTRACT FROM AUTHOR]

Stable isotopes of carbon and nitrogen were used to examine differences in the feeding ecology of sympatric morphotypes of Arctic char, Salvelinus alpinus, from Gander Lake, Newfoundland. Morphotypes were differentiated on the basis of colour (pale and dark) and meristic characteristics. Significant differences in length, age and habitat depth were also noted, with the pale-form being smaller, younger and caught at greater average depths than the dark-form. Pale and dark morphotypes possessed significantly different carbon and nitrogen stable isotope signatures, with the dark-form being more δ13C enriched than the pale-form. Within each morphotype grouping distinctive isotopic signature differences related to diet (dark-form) and capture depth (pale-form) were also observed. Differences in the isotopic signatures within and among habitat groupings were induced by differences in feeding opportunities arising from differences in habitat use and feeding strategies and generally corroborated by stomach content analysis and an index of dietary overlap. Study results provide evidence for the contention that sympatric forms of Arctic char in Gander Lake occupy significantly different foraging niches within the lake. Results further suggest ecologically relevant separations within morphotype groupings result in lower resource competition. [ABSTRACT FROM AUTHOR]

Hybridization between sympatric species provides unique opportunities to examine the contrast between mechanisms that promote hybridization and maintain species integrity. We surveyed hybridization between sympatric coastal steelhead ( Oncorhynchus mykiss irideus) and coastal cutthroat trout ( O. clarki clarki) from two streams in Washington State, Olsen Creek (256 individuals sampled) and Jansen Creek (431 individuals sampled), over a 3-year period. We applied 11 O. mykiss-specific nuclear markers, 11 O. c. clarki-specific nuclear markers and a mitochondrial DNA marker to assess spatial partitioning among species and hybrids and determine the directionality of hybridization. F1 and post-F1 hybrids, respectively, composed an average of 1.2% and 33.6% of the population sampled in Jansen Creek, and 5.9% and 30.4% of the population sampled in Olsen Creek. A modest level of habitat partitioning among species and hybrids was detected. Mitochondrial DNA analysis indicated that all F1 hybrids (15 from Olsen Creek and five from Jansen Creek) arose from matings between steelhead females and cutthroat males implicating a sneak spawning behaviour by cutthroat males. First-generation cutthroat backcrosses contained O. c. clarki mtDNA more often than expected suggesting natural selection against F1 hybrids. More hybrids were backcrossed toward cutthroat than steelhead and our results indicate recurrent hybridization within these creeks. Age analysis demonstrated that hybrids were between 1 and 4 years old. These results suggest that within sympatric salmonid hybrid zones, exogenous processes (environmentally dependent factors) help to maintain the distinction between parental types through reduced fitness of hybrids within parental environments while divergent natural selection promotes parental types through distinct adaptive advantages of parental phenotypes. [ABSTRACT FROM AUTHOR]

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Retinal visual fields were determined using an ophthalmoscopic reflex technique in two seabird species of the family Procellariidae: white-chinned petrel Procellaria aequinoctialis and antarctic prion Pachyptila desolata. The binocular fields of both species show a similar shape but they differ in size and in the position of the bill within the field. In white-chinned petrels the binocular field extends vertically through approximately 140° and has a maximum width of approximately 40°. The bill is placed approximately central within the field. The binocular field of the prions is approximately half this width and vertical extent, and the bill is placed close to the ventral edge. These differences in binocular field topography can be correlated with the different foraging techniques that these birds employ when seeking a similar diet within the same environment. White-chinned petrels pursue individual items both at the surface and while diving to moderate depths. Antarctic prions feed primarily by filtering items from surface waters. These differences in visual field topography mirror those found in different terrestrial bird species that primarily employ visual or tactile cues in the pursuit of food items. White-chinned petrel eyes and visual fields show features of an amphibious optical design similar to those found in penguins and albatrosses.Copyright © 2001 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Ecological segregation (sexual differences in diet or habitat use) in large herbivores has been intimately linked to sexual body size dimorphism, and may affect both performance and survival of the sexes. However, no one has tested comparatively whether segregation occurs at a higher frequency among more dimorphic species. To test this comparatively, data on sex-specific diet, habitat use and body size of 40 species of large herbivores were extracted from the literature. The frequency of ecological segregation was higher among more dimorphic herbivores; however, this was only significant for browsers. This provides the first evidence that segregation is more common among more dimorphic species. The comparative evidence supported the nutritional-needs hypothesis over the incisor breadth hypothesis, as there was no difference in frequency of segregation between seasons with high and low resource levels, and since segregation was also evident among browsers. Whether the absence of a correlation between ecological segregation and level of sexual body size dimorphism for intermediate feeders and grazers is due to biological differences relative to browsers or to the fact that the monomorphic species included in the analysis were all browsers is discussed. [ABSTRACT FROM AUTHOR]

The objectives of this study are to analyse the degree of coexistence between Rana pyrenaica, Euproctus asper and Rana temporaria, to prove the existence of differential predation of E. asper on R. pyrenaica and R. temporaria tadpoles, and to analyse some of the consequences that this may have on the community of tadpoles of both species. Segregation/coexistence was investigated in 83 localities in the Spanish central and western Pyrenees and forty seven new localities for R. pyrenaica were identified. There is a significantly higher degree of coexistence between R. pyrenaica and E. asper than expected from a null association, but there is a spatial segregation between R. pyrenaica and R. temporaria. Laboratory tests showed the existence of selective predation of E. asper on R. temporaria tadpoles. The coexistence between R. pyrenaica and E. asper could favour the populations of R. pyrenaica by decreasing interspecific larvae competition and the chance that R. temporaria colonizes the egg-laying localities of R. pyrenaica. [ABSTRACT FROM AUTHOR]

Erica australis, E. scoparia, E. arborea and Calluna vulgaris are the most abundant heath species on acid, sandstone-derived soils of the Strait of Gibraltar region (southern Spain and northern Morocco). Despite their apparently similar ecological requirements, these four species are somewhat ecologically segregated. Erica australis is abundant only on poor, shallow soils, with a high content in soluble aluminium, generally on mountain ridges and summits. Erica scoparia becomes dominant on deeper sandstone soils with lower aluminium. Calluna vulgaris coexists with these Erica species in communities under low or no tree cover. In the Spanish side of the Strait (Algeciras), Erica arborea tends to be relegated to communities under moderate to dense tree cover, whereas this species is more abundant and widespread in the Moroccan side (Tangier). Tolerance to extreme physical conditions – high aluminium and dense tree cover – and interspecific competition seem to explain the ecological distribution of these four heath species in the Strait of Gibraltar region. The more fragmented pattern of sandstone patches and higher disturbance levels in Tangier might account for the differences in the patterns of ecological distribution of these four heath species between both sides of the Strait of Gibraltar. [ABSTRACT FROM AUTHOR]

In the large European river floodplains, closely related species segregate between habitats within numerous forest communities whose structure and dynamics are shaped by the river and its tributaries. Factors of segregation are mainly geochemistry (lime content and texture), water stress and fluvial dynamics. When sympatric, the closely related species coexist by niche differentiation (life-form, place in the successional stages, phenology and abundance). We have made a comparative study of the niches of 70 species belonging to 24 genera in the alluvial forest communities of the upper Rhine valley (France), using a descriptive and qualitative approach. Results were compared with the literature on European biogeography. Particular attention was paid to seven woody genera (Populus, Salix, Ulmus, Alnus, Acer, Crataegus and Prunus) and to the behaviour of hybrids along the environmental gradients of the study area. [ABSTRACT FROM AUTHOR]