Alternative Habitats Research Articles

Offshore behavioral contingent of an estuarine fish population, common snook Centropomus undecimalis

Research that identifies behavioral contingents, portions of a population that exhibit alternate life history strategies or habitat preferences, can provide a better understanding of a species’ resilience to disturbances, changes in environmental factors, and harvest. Sightings of the estuarine-dependent common snook Centropomus undecimalis at offshore reef areas throughout the year in southeast Florida prompted an investigation to determine whether a contingent of the snook population remains offshore year-round and if they can contribute to the inshore population. This study employed underwater visual observations, specimen collections, and acoustic telemetry over 7 yr to document and describe the snook that utilize offshore habitat. Fish were observed in groups of up to 225 individuals, 20.4 km from an inlet, and in waters up to 36.6 m deep. Snook were present in 79.4% of dive surveys conducted on artificial reefs but only in 18.4% of surveys on natural reefs. Acoustic telemetry showed that many fish remained offshore for multiple years. Most sampled fish (89.1%) were spawning capable, with some classified as actively spawning (15.8%). Reports of snook using offshore reefs occur elsewhere, including southwest Florida and the Florida Keys, indicating that this contingent behavior may not be unique to southeast Florida. Evaluating these occurrences and identifying potential triggers that prompt snook to leave the estuary for an offshore environment can aid in determining how the offshore contingent affects the overall population.

Determinants of fish distribution pattern and habitat preference in protected Karaj River, Iran

Lack of information about ichthyofauna makes it difficult to predict human effects on the communities. In this study, the effects of the environmental and human factors were examined on altitudinal patterns of fish habitat selection, faunal changes, species richness and fish abundance from upstream to downstream in the southern part of the central Alborz Protected Area during 2016 and 2017. 366 fish individuals of five species in three families were identified and brown trout was the dominant species. The river was divided into three zones based on habitat structure, species composition and influence of physical and chemical variables. The results indicate that, in some situations, including small changes in habitat structure indices, physical and chemical variables along the altitudinal gradient are more effective in habitat preference, describing the composition, and abundance. Chemical variables can help to have a better understanding of the conventional patterns, shaped by the habitat structure and physical variables. Habitat suitability index model for brown trout in three zones is completely different over the two years and this species could overcome these conditions. However, upstream areas were more appropriate. Dam, with decreases of outlet water temperature, also creates homogeneous and simple habitats leading to changes in expected fish distribution patterns with decreasing altitude. These conditions may have increased habitat suitability index for the brown trout in downstream, while despite favorable ecological conditions in the middle zone, habitat suitability index and alternative habitats available in this zone are likely to decline due to density and interspecific competition. The natural pattern of fish distribution and habitat selection varies along the altitudinal gradient due to various factors and human disturbances. Optimal management of protected areas can control the effects of some of these factors at least temporarily.

Wood Removals from Lakes May Not Necessarily Elicit Fish Population Responses

AbstractCoarse woody habitat (CWH) in aquatic ecosystems provides structural complexity and a surface for food production for fish. Depending on abundance and complexity of CWH, it is usually associated with influencing predator–prey dynamics, fostering greater localized fish abundance, increasing fish growth, and contributing to fish production, but some conflicting evidence exists about its importance as fish habitat. Our experiment was designed to test for direct linkages between whole‐lake CWH availability and fish community abundance, biomass, and production. We removed ~50% of CWH from three lakes while concurrently sampling them and two other unaffected lakes as controls in a before‐after–control‐impact (BACI) design. Due to the loss of quality foraging habitat, structure, and cover for small fish, we hypothesized that the CWH removal would cause a measurable decline in fish abundance, biomass, and/or production. Despite CWH being a preferred habitat type for fish, our hypothesis was not supported because observed changes in measured fish community metrics could not be attributed to the CWH removal. The inability to directly link the wood removal to changes in the fish metrics we examined may have been due to a number of factors including the composition of the fish community, the high availability of alternate habitat structure (rocks, macrophytes), large quantities of wood remaining in the lakes, the relative lack of littoral habitat use by piscivores, or low statistical power (small sample size, high variance). However, we still urge resource managers to be cautious when considering authorizing removal of CWH from lakes because it does provide temporally stable year‐round structure and high‐quality foraging habitat with unique microbial, fungal, and invertebrate communities. Coarse woody habitat was a preferred habitat for fish and may have a greater relative importance in lakes with minimal alternative cover for fishes or in lakes containing different fish assemblages.

Disentangling the impact of artificial substrata on the trophic ecology of the highly endangered marine invertebrate Patella ferruginea Gmelin, 1791

ABSTRACT Limpets are keystone species worldwide, promoting marine biodiversity in coastal areas. Of special concern are the so-called giant limpets such as Patella ferruginea, either due to their role in marine ecosystems and/or threatened status. The proliferation of artificial substrata caused by human population growth has allowed their use as a surrogate habitat for many species of limpets. However, little is known about the impact on the trophic ecology of these species caused by artificial substrata. The stable isotope approach has been widely used to explore the trophic ecology of marine species and so was used in the present study of P. ferruginea. The results of this study indicated that diet consumption differs between artificial and natural substrata for P. ferruginea. Enrichment in δ15N values of specimens collected within the harbour of Ceuta indicates that this endangered species would be a useful indicator for detecting anthropogenically derived organic matter in coastal areas. Further research is required to evaluate the impact of artificial substrata from a conservational perspective.

True bugs (Hemiptera: Heteroptera) associated with dead wood in exotic Pinus radiata plantations in New Zealand

ABSTRACT This paper reports the true bugs (Heteroptera) collected during a large-scale study of saproxylic insects in exotic pine plantations in New Zealand, reared from Pinus radiata dead wood in the central North Island in 2009–2010. Although only seven species were collected in total, the observations of two flightless flat bug (Aradidae) species indicate that exotic pine forests may provide alternative habitat for dispersal-limited endemic forest invertebrates. An important finding is the first New Zealand record of the Australian aradid Glochocoris monteithi. Assuming this find represents the existence of an established local population, this would be only the third documented case of a flat bug successfully establishing in another major zoological realm.

Saved by the shell: Oyster reefs can shield juvenile blue crabs Callinectes sapidus

Juvenile blue crabs Callinectes sapidus use seagrass and other structured habitats as refuges from predation. Oyster reef habitats provide structural complexity that may offer refuge, but the value of these habitats for juvenile blue crabs has not been examined. We quantified survival of juvenile C. sapidus in structured oyster reef habitat versus unstructured soft-bottom habitat. In a field tethering experiment in the York River, lower Chesapeake Bay (USA), juvenile C. sapidus (10-50 mm carapace width [CW]) were tethered in sand (n = 40) or oyster reef (n = 39) habitats at subtidal sites 1-2 m deep. An underwater camera system was used to record predation activity during 24 h trials. Juvenile crab survival was significantly higher on the oyster reef habitat (53.8%) than on bare sand (15.0%), and tended to increase with crab CW in both habitats. The main successful predators on juvenile blue crabs were northern pufferfish Sphoeroides maculatus in the oyster reef habitat and adult blue crabs in the sand habitat. The high survival rate of juvenile C. sapidus in oyster reef habitats suggests that oyster reefs include physical habitat complexity that may offer refuge from predators. Restored and natural oyster reefs could provide an alternative nursery habitat for juvenile blue crabs, expanding the ecosystem services provided by restored oyster reefs.

Distribution and Utilization Plan of Reclaimed Lands (RLs) as Waterfowl Habitat on the South Coast of Korea

Kim, S.-K.; Kim, J.-C., and Choi, J.-Y., 2020. Distribution and utilization plan of reclaimed lands (RLs) as waterfowl habitat on the south coast of Korea. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Geospatial Research of Coastal Environments. Journal of Coastal Research, Special Issue No. 102, pp. 107-112. Coconut Creek (Florida), ISSN 0749-0208.Since 1960, in South Korea, many coastal areas have been reclaimed to secure agricultural land and construct levees. Small-scale reclaimed lands (RLs) were isolated from coastal areas by levees and roads, and this resulted in the loss of the intrinsic characteristics of the ocean environment. In this study, the distribution of RLs located on the south coast of South Korea was investigated, and the formation cause and use types were identified. Furthermore, their potential was assessed as an alternative wetland by investigating waterfowl distribution in each RL. A total of 161 RLs (total area: 776 ha) were located near the southern coastal area of South Korea. Most RLs were created through disconnection from the marine environment due to the construction of an embankment or road, and most of the land was left unattended because it was difficult to use as agricultural or residential areas due to its narrowness and intermittent water level. The majority of RLs were characterized by intermitted water levels, deep water depth, and high salinity, making it difficult for plants other than emergent plants to develop, and consequently, fauna, including birds, were unable to utilize the environment as a habitat. In winter, some RLs were utilized as habitats for ducks (i.e., dabbling ducks and diving ducks), but there were few in the following seasons (spring and autumn). However, an RL was judged to have potential as a wetland if ecological function improvements, such as efficient water supply and water depth control, could be made. In particular, increasing the diversity and coverage rate of aquatic plants can lead to abundant food sources, such as fish and invertebrates. The use of these RLs as wetlands not only enhances the value of abandoned RLs but can also be a significant alternative habitat for diverse animals at a time when inland wetlands are being damaged and reduced.

The diversity of small mammals in a mixed fruit orchard at Bukit Bekong limestone massif, Merapoh, Pahang, Malaysia

The increasing forest fragmentation due to human encroachment has isolated and scattered forest patches and limestone karsts. Agroforestry has been touted as a sustainable solution for the agriculture sector to yield crops and also provide alternative habitats for wildlife outside protected areas and linking forest patches and isolated limestone karsts. This initial survey was conducted to evaluate small mammals (bats and non-volant) assemblages present in a mixed fruit orchard bordering Bukit Bekong limestone massif in Merapoh, Pahang. We captured 193 individuals from 28 species (13 for bats & 15 for non-volant) using mist nets, harp traps and cage traps. This orchard contains Nycteris tragata and Kerivoula pellucida, listed as Near Threatened plus Maxomys rajah as Vulnerable in the IUCN Red List, revealing the fact that this small area in comparison to protected areas possesses unprecedented conservation value. Furthermore, 15 out of 28 small mammal species captured are habitat generalist may provide a cause of concern for the loss of forest specialists. Nonetheless, our results show that less intensively managed agroforest like mixed fruit orchard can also support forest specialists that are sensitive to disturbance. Moreover, the presence of limestone karst nearby contributes to bat diversity, especially cave-roosting bats. In summary, the diversity of small mammals in agroforest is worth to be studied as the species accumulation curve in this one mixed fruit orchard has yet to reach an asymptote. We hope future biodiversity data in agroforest will be incorporated in agriculture management strategies to stimulate sustainable agriculture and promoting mammal diversity.

Invasive Carp Reproduction Phenology in Tributaries of the Upper Mississippi River

AbstractInvasive Bighead Carp Hypophthalmichthys nobilis, Silver Carp H. molitrix, and Grass Carp Ctenopharyngodon idella are expanding throughout the upper Mississippi River (UMR) basin. Spawning has occurred in the main‐stem UMR but could be limited to high‐discharge events when dam operations create a free‐flowing river. Alternatively, naturally free‐flowing tributaries could offer alternative habitat for successful reproduction. Our objectives were to examine temporal and spatial variation in adult gonad development, ichthyoplankton densities, and back‐calculated spawn dates of invasive carp collected in three UMR tributaries. We compared ichthyoplankton densities between the upstream and mouth reaches of tributaries and densities between the UMR and adjacent tributaries. Ichthyoplankton samples were collected every 10 d, and adult invasive carp were sampled monthly at nine sites throughout the Des Moines, Skunk, Iowa, Cedar, and Mississippi rivers during April–October 2014 and 2015. Peaks in adult gonadosomatic index, an increase in postspawn females, and ichthyoplankton collections suggested that peak spawning occurred during late May through June, when water temperatures were 18–30°C and channel velocities were at least 0.7 m/s. However, reproduction occurred as late as August in some tributaries. Ichthyoplankton densities were highest in the Des Moines River among tributaries, but tributary densities were similar to the UMR densities, suggesting that both tributaries and main‐stem sites provide suitable spawning locations. Invasive carp reproduction in UMR tributaries provides additional sources of potential recruitment for further population expansion upstream in the UMR and should be considered when devising plans for controlling populations along the leading edge of the invasion.

Seascape Configuration Leads to Spatially Uneven Delivery of Parrotfish Herbivory across a Western Indian Ocean Seascape

Spatial configuration of habitat types in multihabitat seascapes influence ecological function through links of biotic and abiotic processes. These connections, for example export of organic matter or fishes as mobile links, define ecosystem functionality across broader spatial scales. Herbivory is an important ecological process linked to ecosystem resilience, but it is not clear how herbivory relates to seascape configuration. We studied how herbivory and bioerosion by 3 species of parrotfish were distributed in a multi-habitat tropical seascape in the Western Indian Ocean (WIO). We surveyed the abundance of three species with different life histories—Leptoscarus vaigiensis (seagrass species), Scarus ghobban (juvenile-seagrass/adults-reefs) and Scarus rubroviolaceus (reef species) —in seagrass meadows and on reefs and recorded their selectivity of feeding substrate in the two habitats. Herbivory rates for L. vaigiensis and S. ghobban and bioerosion for S. rubroviolaceus were then modelled using bite rates for different size classes and abundance and biomass data along seascape gradients (distance to alternative habitat types such as land, mangrove and seagrass). Bioerosion by S. rubroviolaceus was greatest on reefs far from seagrass meadows, while herbivory rates by S. ghobban on reefs displayed the opposite pattern. Herbivory in seagrass meadows was greatest in meadows close to shore, where L. vaigiensis targeted seagrass leaves and S. ghobban the epiphytes growing on them. Our study shows that ecological functions performed by fish are not equally distributed in the seascape and are influenced by fish life history and the spatial configuration of habitats in the seascape. This has implications for the resilience of the system, in terms of spatial heterogeneity of herbivory and bioerosion and should be considered in marine spatial planning and fisheries management.

Nestling Diet and Breeding Success of Little Bitterns Ixobrychus minutus at Two Artificial Fishpond Complexes in South-Western Slovakia

Artificial fishponds are assumed to be suitable alternative habitat for many waterbirds including fish-eating predators such as herons. However, fish farming may lead to contrasting consequences for birds breeding in these biotopes and act as an ecological trap. I examined nestling diet and reproductive success of the least studied heron species in Europe, the endangered Little Bittern Ixobrychus minutus, at two fishpond complexes in south-western Slovakia. A total of 95 breeding attempts by this species were recorded during 2015–2019 in the study area, 84% of which produced at least one nestling. Despite relatively high nest success at both sites, the number of fledged nestlings differed significantly between the two fishpond complexes. The observed differences were mainly caused by higher nest predation at one of the fishponds. The diet of nestlings also differed between study sites. While the food taken at fishponds that are used for intensive farming of Common Carp Cyprinus carpio contained significant proportions of insects (41%) and amphibians (14%), at fishponds used mainly for individual sport fishing, parents fed their nestlings exclusively fish. However, the total amount of food delivered to nestlings was similar at both fishpond complexes. This suggests that Little Bitterns are able to adapt to fishponds with various intensities of management. Nevertheless, considering differences in nest predation risk between studied fishponds, other factors such as abundance and structure of littoral vegetation and predator abundance, can influence the breeding success of this species in artificial fishpond habitats. Identifying such factors may be important for the conservation and management of this species.

Size-specific recolonization success by coral-dwelling damselfishes moderates resilience to habitat loss

Increasing degradation of coral reef ecosystems and specifically, loss of corals is causing significant and widespread declines in the abundance of coral reef fishes, but the proximate cause(s) of these declines are largely unknown. Here, we examine specific responses to host coral mortality for three species of coral-dwelling damselfishes (Dascyllus aruanus, D. reticulatus, and Pomacentrus moluccensis), explicitly testing whether these fishes can successfully move and recolonize nearby coral hosts. Responses of fishes to localized coral loss was studied during population irruptions of coral feeding crown-of-thorns starfish, where starfish consumed 29 (34%) out of 85 coral colonies, of which 25 (86%) were occupied by coral-dwelling damselfishes. Damselfishes were not tagged or individually recognizable, but changes in the colonization of different coral hosts was assessed by carefully assessing the number and size of fishes on every available coral colony. Most damselfishes (> 90%) vacated dead coral hosts within 5 days, and either disappeared entirely (presumed dead) or relocated to nearby coral hosts. Displaced fishes only ever colonized corals already occupied by other coral-dwelling damselfishes (mostly conspecifics) and colonization success was strongly size-dependent. Despite movement of damselfishes to surviving corals, the local abundance of coral-dependent damselfishes declined in approximate accordance with the proportional loss of coral habitat. These results suggest that even if alternative coral hosts are locally abundant, there are significant biological constraints on movement of coral-dwelling damselfishes and recolonization of alternative coral habitats, such that localized persistence of habitat patches during moderate or patchy disturbances do not necessarily provide resilience against overall habitat loss.

Predictors of Gull-billed tern (Gelochelidon nilotica) nest survival in artificial coastal saltpans, Bohai Bay, China.

BackgroundCoastal saltpans are a common supratidal human-modified wetland habitat found within many coastal landscape mosaics. Commercial salt production and aquaculture practices often result in the creation of exposed coastal substrates that could provide suitable breeding habitat for waterbird populations; however, few studies have quantified waterbird breeding success in these artificial wetlands.MethodsHere we examine the nesting behavior of the Gull-billed tern (Gelochelidon nilotica) breeding in the Nanpu coastal saltpans of Bohai Bay, Yellow Sea, China over three consecutive nesting seasons (2017–2019) by using nest survival model in Program MARK.ResultsThe results revealed that nest survival of Gull-billed terns in coastal saltpans (0.697) was higher than previously published estimates from other regions, with an estimated daily survival rate (DSR) of 0.982 ± 0.001 (±95% CI). High nest survival was mainly attributed to low levels of human disturbances and low predation rates, while exposure to strong winds, flooding and silting were the main factors causing nest failure. Model-averaged estimates revealed that eggs laid in nests located on ‘habitat islands’ with feather or clam shell substrates were most likely to hatch. Initiation date, nest age, clutch size and quadratic effects of nearest-neighbor distance, nearest distance to road and nearest distance to water were all significant predictors of nest success, but the nest survival declined overall from 2017 to 2019 due to the degradation and loss of breeding habitat anthropogenically caused by rising water levels.DiscussionCoastal saltpans represent an alternative breeding habitat for the Gull-billed tern populations in Bohai Bay, but conservation management should prioritize flood prevention to improve the extent and quality of breeding habitat, concurrent with efforts to create further ‘habitat islands’ with suitable nesting substrate.

Unravelling Seascape Patterns of Cryptic Life Stages: Non-Reef Habitat Use in Juvenile Parrotfishes

Juvenile fish often use alternative habitats distinct from their adult phases. Parrotfishes are an integral group of coral reef fish assemblages, are targeted in fisheries, are sensitive to reef disturbances, and have been documented as multiple-habitat users. Considering the abundance of research conducted on parrotfishes, very little is known about their juvenile ecology at the species level due to their cryptic and variable coloration patterns. We collected juvenile parrotfishes in non-reef habitats (macroalgal beds, seagrass beds, and lagoons) in the Philippines and used DNA analysis to determine species composition. The results were then compared with data on adult parrotfish abundance from underwater visual census (UVC) surveys in coral reef and non-reef habitats. Collections identified 15 species of juvenile parrotfishes in non-reef habitats, and of these, 10 were also recorded in UVCs as adults. Informed by adult surveys, 42% of the 19 parrotfish species observed as adults were classified as multi-habitat users based on their presence in coral reef and non-reef habitats. When accounting for the occurrence of species as juveniles in non-reef habitats, 93% of the species collected as juveniles would be considered multi-habitat users. Species identified as juveniles in non-reef habitats comprised 50% of the average adult parrotfish density on coral reefs and 58–94% in non-reef habitats. The species richness of juveniles in non-reef habitats was greater than that of adults occupying the same habitats, and the most common adult species observed in UVCs was not collected as juveniles in non-reef habitats. Finally, UVC suggested that 97% of juvenile parrotfish <10-cm total length was present in non-reef habitats compared to coral reefs. These results provide further evidence for ontogenetic movement across habitat boundaries for parrotfish species in a diverse and highly connected tropical seascape. This is one of the few studies to quantify links between nursery and adult habitat in parrotfishes, highlighting the importance of including non-reef habitats in ecological studies of an iconic group of coral reef fish.

Effect of Diverse Abiotic Conditions on the Structure and Biodiversity of Ichthyofauna in Small, Natural Water Bodies Located on Agricultural Lands

Mid-field natural ponds promote regional biodiversity, providing alternative habitats for many valuable animal species. The study’s objective was to determine the most important abiotic factors, including hydrochemical and morphometric parameters, affecting fish occurrence in natural, small water bodies on agricultural lands. The studies were conducted in nine randomly selected water bodies located in Poland (the North European Plain). Eleven species of fish were recorded in the waterbodies, with the most abundant being cyprinids (mainly crucian carp). Canonical correspondence analysis (CCA) showed that an increase in oxygenation, temperature, amount of macrophytes, and K concentration and a decrease in the concentration of phosphates, electrical conductivity (EC), Mg, and Cl is associated with the most beneficial living conditions for the most frequently occurring species in the studied water bodies—crucian carp and tench. Aside from the hydrochemical parameters of water in the natural ponds, the number of fish correlates with the basin area and the pond area, maximum depth, area of the buffer zone surrounding the water bodies, and the number of macrophytes. This last factor also has a significant influence on the species’ abundance in the water bodies. Fish occurrences in mid-field ponds and common knowledge on their important role in the environment require taking steps to provide fish protection.

Isotopic niche size of Coregonus artedi (sensu lato) Increases in the presence of Mysis diluviana, expanded habitat use and phenotypic diversity.

Post‐glacial colonization of lakes in Algonquin Park, Ontario, Canada resulted in food webs with cisco (Coregonus artedi sensu lato) and either Mysis diluviana or Chaoborus spp. as the dominant diel migrator. Mysis as prey, its diel movements and benthic occupancy, are hypothesized to be key elements of ecological opportunity for cisco diversity in the Laurentian Great Lakes. If correct, the hypothesis strongly implies that lakes with Mysis would have greater trophic niche size and drive greater adaptive radiation of cisco forms relative to lakes without Mysis. The dichotomy in diel migrator in Algonquin Park lakes was an opportunity to assess the isotopic niche size of cisco (δ15N and δ13C) and determine if niche size expands with Mysis presence. We found the presence of Mysis is necessary to expand isotopic niche size in our study lakes. The use of habitats not typically associated with the ancestral form of cisco (e.g., benthic habitats) and phenotypic diversity (blackfin and cisco) also continue to expand niche size in Mysis‐based food webs. Partial ecological speciation based on a large niche space appears to be present in one lake (Cauchon Lake) where use of alternative habitats is the only real difference in cisco. The presence of blackfin expands niche space in Cedar and Radiant Lakes. This was not matched in Hogan Lake where niche space was relatively smaller with similar forms. Possible reasons for this discrepancy may be related to the asymmetric basin of Hogan Lake and whether the two forms overlap during cool and cold‐water periods of the annual temperature cycle. By comparing trophic niche size among lakes with and without Mysis, we conclude that Mysis provides a key ecological opportunity for cisco diversity in our study lakes and likely more widely.

Search strategies in rural and urban environment during natal dispersal of the red squirrel

Decisions made during natal dispersal highly influence the future fitness of the animal. The selection of future home range affects, for example, food supply and mating success. In order to select between potential sites, dispersing individuals may use different search strategies, and for example, aim to compare quality of different sites by revisiting them. Alternatively, dispersers visit new sites without comparison until a suitable site is located. By using radio telemetry, we studied search strategies during natal dispersal in both urban and rural environments. We examined what kind of sites juvenile red squirrels (Sciurus vulgaris) choose as their home range from all visited sites and whether they display revisit behavior during natal dispersal. We found that most of the dispersing individuals perform revisits while searching for the settlement site. In the rural study area, there were also individuals (mostly long-distance dispersers) that did not perform revisits and settled in the last visited area. The landscape characteristics did not explain the amount of revisits individuals made, but the amount of revisits declined with site’s distance to natal nest and dispersal distance of individuals. The effect of landscape characteristics on settlement decision was small, but surprisingly, juvenile red squirrels in the rural area settled in sites with more built area compared with sites only visited. However, the decision-making of red squirrels during natal dispersal seems to be driven mainly by other factors (potentially food availability and conspecific density) than landscape characteristics. We conclude that revisiting behavior is linked to dispersal strategy of red squirrels and can differ between the sexes and habitats of the species.Significance statementAnimals often choose their habitat from among multiple alternative habitats and potential settlement sites, and the decisions made during dispersal highly influence the future fitness of the animal. We examined what kind of areas juvenile red squirrels choose as their home range in both urban and rural environments and whether they display revisit behavior when selecting their home range from many alternatives. We found that search strategies during natal dispersal can vary between individuals and habitats. Surprisingly, juvenile red squirrels in the rural area settled in sites with more built area compared with the sites only visited. However, for red squirrel, decisions made by juveniles during the search of a home range are mainly influenced by other factors than landscape composition.

Spatial ecology of little egret (Egretta garzetta) in Hong Kong uncovers preference for commercial fishponds.

Many natural wetlands have been converted to human-influenced wetlands. In some instances, human-influenced wetlands could provide complementary habitats for waterbirds, compensating for the loss of natural wetlands. Inner Deep Bay in Hong Kong is composed of both natural and human-influenced wetlands and is under immense development pressure. From an ecology perspective, we need to understand if different wetland types play the same ecological role. To achieve this, we tracked nine little egrets (Egretta garzetta) using GPS loggers for 14 months to study their spatial ecology, home range, movement and habitat use. We found that over 88% of the home range of all individuals comprised of wetlands (commercial fishponds, mangrove, gei wai, channel, and intertidal mudflat). Among these wetland types, nearly all (seven of nine) individuals preferred commercial fishponds over other habitats in all seasons. Little egrets exhibited seasonal movement and habitat use among seasons, with largest home range, greatest movement, and most frequent visits to commercial fishponds in winter compared to spring and autumn. Our results highlight the significant role of commercial fishponds, providing a feeding ground for little egrets. However, other wetland types cannot be ignored, as they were also used considerably. These findings underscore the importance of maintaining a diversity of wetland types as alternative foraging and breeding habitats.

Assessment of growth patterns of amphidromous fish larvae in alternative estuarine nursery habitats along a developed coast

The placement of artificial structures in coastal areas can adversely impact the life histories of larval and juvenile fish by reducing suitable nursery areas. However, little is known about the responses of them to such habitat loss. The ayu Plecoglossus altivelis altivelis is an amphidromous fish that spends its early ontogenetic stages in suitable nurseries, the surf zone, within 2 km from river mouths. To evaluate the possible impact of habitat loss on larval and juvenile ayu, we collected 50 juveniles from the Takahashi River, Okayama, Japan, on 19 April 2018, where more than 95% of the coastal outlet area is covered with artificial structures. Otolith Sr/Ca- and increment analyses were conducted to examine the habitat use and growth rates of each individual. We also collected nine larvae on 27 December 2018 from a semi-natural surf zone, which is located 5 km from the Takahashi River mouth, in order to evaluate their growth rate. The 50 juveniles spent approximately one-third of their marine life stage in estuaries with brackish water, suggesting that the estuaries are the only nursery grounds remaining in this area. Among the 50 juveniles, specimens that experienced lower salinities showed higher growth rates and larger body sizes in the larval stage (1–80 days old). However, a large variation in growth rates was also observed among the specimens that grew in estuaries, probably owing to environmental instability in the area. While the difference was not statistically significant, the nine larvae from the semi-natural surf zone showed higher growth rates than the 50 juveniles from the Takahashi River. Our results indicate that the estuaries can be an alternative habitat, but that they might not be a better habitat than the regular surf zone habitat.

Farmland birds occupying forest clear-cuts respond to both local and landscape features

Agricultural landscapes have changed fast in Europe, which has led to steep declines in farmland biodiversity. While this has differentially impacted “farmland species”, some of these seem to be able to use alternative man-made open habitats in forests, such as forest clear-cuts and powerline rights-of-way. We investigated the use of clear-cuts by two historically declining farmland birds, the Yellowhammer (Emberiza citrinella) and the Red-backed Shrike (Lanius collurio), to determine both local and landscape habitat characteristics of clear-cuts used for breeding. Among 101 clear-cuts visited in Scania, southern Sweden, 27% were occupied by Yellowhammers and 12% by Red-backed Shrikes. Yellowhammer occurrence in clear-cuts was positively related to local spruce cover (the planted tree species). There was also an interaction between clear-cut size and the proportion of farmland in the landscape, such that the positive effect of the proportion of farmland nearby was stronger for larger clear-cuts. Red-backed Shrike occurrence was positively related to clear-cut size and the local presence of piles of forest residues (tops and branches). The relation between occurrence and the proportion of clear-cuts in the landscape was positive for small clear-cuts and negative for larger ones. Yellowhammers and Red-backed shrikes are affected by both the local habitat structure in the clearcut and on the composition of the surrounding landscape, most likely because they use the clear-cut for nesting and the surroundings as complementary feeding habitat. To what extent clear-cuts as complementary breeding habitat to farmland may contribute to the conservation of Yellowhammers and Red-backed shrikes, as well as other farmland birds, is a promising path for future investigations.