Winter Habitat Research Articles

Differential winter and breeding range shifts: Implications for avian migration distances

AbstractAimFor many migratory avian species, winter and breeding habitats occur at geographically distinct locations. Disparate magnitudes and direction of shifts in wintering and breeding locations could lead to altered migration distances. We investigated how shifts in the centre of abundance (COA) of winter and breeding ranges have changed for 77 species of short‐distance migratory birds. We addressed whether species tracked their historical average temperature and precipitation conditions at their winter and breeding COA, using data from 1990 to 2015.LocationNorth America.MethodsWe calculated the COA for winter and breeding ranges from the National Audubon Society's Christmas Bird Count and the North American Breeding Bird Survey. We regressed the annual change in distance (km) between the two annual COAs of each species as a proxy for change in migration distance. We constructed a series of generalized linear mixed models (GLMMs) to evaluate changes in average temperature and precipitation at the wintering and breeding COAs.ResultsWinter shifts in COA were predominantly northward. For most species, average temperature and precipitation that species experienced had not changed. Breeding shifts in COA varied in direction. For breeding season COAs, average temperature warmed, but average precipitation had not changed. Thirty‐one species significantly decreased their migration distances, mainly driven by northward shifts in the winter range. Ten species increased their migration distances.Main conclusionsWinter and breeding range shifts in COA have not occurred at the same magnitude and direction and have therefore impacted migration distance. Our results suggest that wintering and breeding range shifts occur independently and under different climate pressures.

Habitat predicts local prevalence of migratory behaviour in an alpine ungulate.

The resource hierarchy hypothesis predicts that the most important factors limiting a species' distribution act at the coarsest spatial scales. However, resource selection behaviour affords mobile organisms the opportunity to adopt a range of tactics for navigating spatial trade-offs between competing biotic and abiotic constraints. Throughout the animal kingdom, partial migration (where some individuals migrate, and others remain resident year round) offers a pervasive example of such behavioural polymorphism. Identifying the differences between these behaviours is therefore central to understanding the conditions (habitat) needed to sustain migrant and resident populations. Here we test an extension of the resource hierarchy hypothesis. We hypothesized that rather than responding to a single limiting factor, migration and residency represent contrasting scale-specific approaches to managing trade-offs between forage, predation risk and severe winter conditions. Furthermore, we predicted that the distribution of habitat selected by migrants and residents is predictive of the local prevalence of migratory behaviour. To test these hypotheses, we quantified migratory status- (resident/migrant) and season-specific (winter/summer) differences in resource selection by eight populations of federally endangered Sierra Nevada bighorn sheep Ovis canadensis sierrae across three spatial scales: population range, individual range and within individual range. We then integrated these spatial predictions to produce separate spatial predictions of migrant and resident winter habitat. As predicted, model selection provided strong evidence for the importance of status-specific differences in resource selection. Residents showed stronger coarse-scale selection for terrain associated with predator avoidance and stronger fine-scale selection for greenness, while in migrants this pattern was reversed. Availability of migrant habitat predicted the local prevalence of migration (top model pseudo R2 of .87). Our ability to respond to global declines of migratory species depends on improving our understanding of the conditions required to maintain migratory behaviour. Through explicitly contrasting migrant and resident behaviour, our results illustrate seasonal differences in migrant and resident habitat and how these two behaviours represent responses to different limiting conditions. Our analyses provides a novel empirical basis for assessing the local prevalence of migratory behaviour across large landscapes.

Oceanographic drivers of winter habitat use in Cassin's Auklets.

Reduced prey abundance and severe weather can lead to a greater risk of mortality for seabirds during the non-breeding winter months. Resource patterns in some regions are shifting and becoming more variable in relation to past conditions, potentially further impacting survival and carryover to the breeding season. As animal tracking technologies and methods to analyze movement data have advanced, it has become increasingly feasible to draw fine-scale inference about how environmental variation affects foraging behavior and habitat use of seabirds during this critical period. Here, we used archival light-sensing tags to evaluate how interannual variation in oceanography affected the winter distribution of Cassin's Auklets from Southeast Farallon Island, California. Thirty-five out of 93 geolocators deployed from 2015 to 2017 were recovered and successfully recorded light-level data, from which geographic positions were estimated. Step-selection functions were applied to identify environmental covariates that best explained winter movement decisions and habitat use, revealing Cassin's Auklets dispersed farther from the colony during a winter with warm SST anomalies, but remained more centralized near the breeding colony during two average winters. Movement patterns were driven by avoidance of areas with higher sea surface temperatures and possible limits of dispersal from the breeding colony, and selection for areas with well-defined mesoscale fronts and cooler surface waters. Through multiple years of tagging and the application of step-selection functions, a robust and widely applied approach for analyzing animal movement in terrestrial species, we show how interannual differences in the movement patterns of a small seabird are driven by oceanographic variability across years. Understanding the winter habitat use of seabirds can help inform changes in population structure and measures of reproductive success, aiding managers in determining potential causes of breeding failures.

Development of Active Numerating Side-scan for a High-Density Overwintering Location for Endemic Shortnose Sturgeon (Acipenser brevirostrum) in the Saint John River, New Brunswick

In 1979, the Shortnose Sturgeon (Acipenser brevirostrum) population of the Saint John River, New Brunswick, was estimated at 18,000 ± 5400 individuals. More recently, an estimate of 4836 ± 69 individuals in 2005, and between 3852 and 5222 individuals in 2009 and 2011, was made based on a single Shortnose Sturgeon winter aggregation in the Kennebecasis Bay of the Saint John River, a location thought to contain a large proportion of the population. These data, in combination with the Saint John River serving as the sole spawning location for Shortnose Sturgeon in Canada prompted a species designation of “Special Concern” in 2015 under Canada’s Species at Risk Act (SARA). A three-decade span of scientific observations amplified by the traditional knowledge and concerns of local indigenous groups have pointed to a declining population. However, the endemic Shortnose Sturgeon population of the Saint John River has not been comprehensively assessed in recent years. To help update the population estimate, we tested a rapid, low-cost side-scan sonar mapping method coupled with supervised image classification to enumerate individual Sturgeon in a previously undescribed critical winter location in the Saint John River. We then conducted an underwater video camera survey of the area, in which we did not identify any fish species other than Shortnose Sturgeon. These data were then synchronized with four years of continuous acoustic tracking of 18 Shortnose Sturgeon to produce a population estimate in each of the five identified winter habitats and the Saint John River as a whole. Using a side-scan sonar, we identified > 12,000 Shortnose Sturgeon in a single key winter location and estimated the full river population as > 20,000 individuals > ~40 cm fork length. We conclude that the combined sonar/image processing method presented herein provides an effective and rapid assessment of large fish such as Sturgeon when occurring in winter aggregation. Our results also indicate that the Shortnose Sturgeon population of the Saint John River could be similar to the last survey estimate conducted in the late 1970s, but more comprehensive and regular surveys are needed to more accurately assess the state of the population.

Influence of fire severity and vegetation treatments on mule deer (Odocoileus hemionus) winter habitat use on the Kaibab Plateau, Arizona

Context Wildfire and vegetation treatments affect mule deer (Odocoileus hemionus) populations across the western United States. However, the relative influence of fire and treatments on habitat use by mule deer in Arizona is not well defined. Aims We examined locations of mule deer on the Kaibab Plateau in northern Arizona, so as to determine the influence of vegetation treatments and wildfire severity on deer habitat-use patterns across their winter range where fires and treatments had occurred previously. Methods We used locations (n = 11297) from 21 adult female mule deer fitted with global positioning system collars to model probability of use as a function of habitat covariates. Key results The best model describing winter-range habitat use by mule deer on the Kaibab Plateau included covariates describing the age of vegetation treatments and fire severity. Increased deer use in winter was associated with areas of lower terrain ruggedness and reduced snow depths. Deer use also increased in areas that experienced a higher average fire severity, resulting in decreased vegetation heights. Among treatment age classes, deer use was greatest in areas containing vegetation treatments that were ≤6 years old, but negatively associated with treatments that were >6 years old. Conclusions Vegetation treatments designed to remove or reduce less palatable tree and shrub species to improve forage conditions may increase the use of winter habitats by deer on the Kaibab Plateau. Similarly, prescribed fire and rangeland treatments designed to return areas to a more natural fire regime and, thereby, generate new plant growth, may improve winter-range habitat conditions for mule deer. Implications Similar treatment strategies may also benefit mule deer populations throughout the western USA, by improving forage conditions on critical habitats and reducing the potential for catastrophic wildfire.

Anthropogenic noise affects winter song structure of a long-distance migrant, Gambel’s white-crowned sparrow

AbstractMany animals learn to produce acoustic signals that are used to attract mates and defend territories. The structure of these signals can be influenced by external features of the environment, including the anthropogenic soundscape. In many sedentary species, habitat features and soundscape appears to influence the cultural evolution of songs, often with tradeoffs for better transmission over sexually selected song structure. However, none have investigated whether noise on the wintering grounds affects song structure, which for long-distance migrants may result in an acoustic ‘mismatch’ when returning to a breeding ground. This study investigates urban noise effects on song structure in a long-distance migrant, Zonotrichia leucophrys gambelii, on the wintering grounds in the Fresno Clovis Metropolitan Area and in outlying non-urban areas. Songs and background noise levels were recorded concurrently, and song measurements of frequency and duration were examined differences across noise levels and habitats . We found that the buzz and trill decrease in bandwidth in the presence of noise. The length of the whistle and buzz portion of the song also tends to decreases with noise in urban habitats. This trend toward short, pure tones in noisy areas may transmit better in noisy urban winter habitats, but may not be adaptive on quieter breeding grounds. We suggest that future studies should consider whether winter auditory feedback and song learning environments have consequences for song crystallization and breeding success for long-distance migrants.

Condition of mule deer during winter: stress and spatial overlap with North American elk

We assessed body condition, diet quality (indexed by fecal nitrogen), and stress levels (using fecal glucocorticoid metabolites) in mule deer Odocoileus hemionus in southeastern Idaho, USA, during a mild (2007) and a harsh winter (2008) to evaluate spatial overlap and potential competition with North American elk Cervus elaphus. We used data from GPS telemetry to construct spatially explicit maps of local population density of elk for January–April. Loss of body condition over winter in yearling and adult female mule deer was not related to elk density but to winter severity. Fecal nitrogen increased as winter progressed in both winters, was significantly lower during 2008 than in 2007, but was not related to local population density of elk. In the mild winter of 2007, a significant positive relationship existed between local population density of elk and fecal glucocorticoid metabolite levels of mule deer, indicating increased physiological stress among mule deer wintering in close proximity to elk. Fecal glucocorticoid metabolite levels in deer were lower in 2008 than in 2007 and exhibited no significant relationship with elk density. Declining fecal glucocorticoid levels through winter may be typical of northern cervids. No difference existed in levels of fecal glucocorticoids between sexes of deer. A reduction in elk populations may not improve diet quality, physiological stress levels, or body condition of mule deer on winter range, especially during severe winters. Consequently, management and conservation of winter habitat are more likely to benefit mule deer than would altering density of elk.

Individual variation in migratory movements of chinstrap penguins leads to widespread occupancy of ice-free winter habitats over the continental shelf and deep ocean basins of the Southern Ocean.

A goal of tracking migratory animals is to characterize the habitats they use and to interpret population processes with respect to conditions experienced en route to, and within, overwintering areas. For migratory seabirds with broad breeding ranges, inferring population-level effects of environmental conditions that are experienced during migratory periods would benefit by directly comparing how birds from different breeding aggregations disperse, characterizing the physical conditions of areas they use, and determining whether they occupy shared foraging areas. We therefore tracked 41 adult and juvenile chinstrap penguins (Pygoscelis antarctica) from three breeding locations in the northern Antarctic Peninsula region during the austral winter of 2017. The satellite tracking data revealed overlap of individuals over continental shelf areas during autumn months (Mar-May), shared outbound corridors that track the southern Antarctic circumpolar current front, followed by occupancy of progressively colder, deeper, and ice-free waters that spanned the entire western hemisphere south of the Polar Front. Despite broadly similar physical environments used by individuals from different colonies, the proportion of birds from each colony that remained within 500km of their colony was positively correlated with their local population trends. This suggests that local migration strategies near the Antarctic Peninsula may benefit breeding populations. However, the magnitude of inter-colony and intra-colony overlap was generally low given the broad scale of habitats occupied. High individual variation in winter movements suggests that habitat selection among chinstrap penguins is more opportunistic, without clear colony-specific preference for fine-scale foraging hotspots. Mixing of individuals from multiple colonies across broad regions of the Southern Ocean would expose chinstrap penguins from the Antarctic Peninsula to a shared environmental experience that helps explain the regional decline in their abundance.

Brook trout (Salvelinus fontinalis) movement and survival after removal of two dams on the West Branch of the Wolf River, Wisconsin

AbstractDam removals allow fish to access habitats that may provide ecological benefits and risks, but the extent of fish movements through former dam sites has not been thoroughly evaluated for many species. We installed stationary PIT antennas in 2016 and 2017 to evaluate movements and survival of brook trout Salvelinus fontinalis in the West Branch of the Wolf River (WBWR) in central Wisconsin following removal of two dams and channel modifications designed to promote fish movement. These changes provided access to lacustrine habitats that might provide suitable winter habitat or act as ecological sinks. We used multistate models to estimate transition probabilities between river sections, to determine whether brook trout: (a) moved between multiple river sections and (b) entered lacustrine habitats as seasonal refuges, but eventually returned to lotic habitat. We also used a Cormack‐Jolly‐Seber model to evaluate whether apparent survival of brook trout in the WBWR was comparable to other populations. Few fish moved among river sections or used lacustrine habitat (<5% of tagged fish); most brook trout remained in sections where they were initially tagged, potentially due to quality habitat located throughout the river. Like other studies, brook trout in the WBWR appear to experience high mortality based on low number of detections, few physical recaptures and an estimated eight‐month apparent survival rate of 0.27. In scenarios where fish can already access suitable habitat, removal of dams may not result in substantial increases in fish movement and colonisation of newly accessible habitat may not occur immediately.

Large-scale versus small-scale agriculture: Disentangling the relative effects of the farming system and semi-natural habitats on birds’ habitat preferences in the Ethiopian highlands

While the Western World is facing an inexorable decline of its farmland biodiversity following continuous intensification of production modes, agricultural landscapes in Africa are still largely dominated by small-scale subsistence farming operated by smallholders, mostly harbouring high biodiversity. However, as most African countries are confronted to an unprecedented population growth and a rapid economic development, efforts to intensify food production are widespread, with concomitant potentially negative effects on biodiversity. We conducted a study in a highly contrasted agricultural landscape of the Ethiopian highlands comprising two distinct farming systems: large-scale farming relying on modern, combine machinery and technology (e.g. enhanced crop varieties, application of herbicides, pesticides and synthetic fertilizers) vs small-scale traditional farming. Our objective was to disentangle the effects upon avian biodiversity of the operating farming system and the extent of semi-natural habitat features in the wider landscape. We performed a model selection approach to assess habitat selection by the overall bird community as well as the wintering, endemic and open habitat species, respectively. Our results show that habitat preferences of birds in the Ethiopian highlands were mainly driven by the amount of semi-natural habitats within the landscape, with varying effects depending on the farming system itself. While large-scale farming had overall more negative effects on birds, some typical open habitat species were mostly restricted to these wide-open landscapes. Our findings thereby suggest that both farming systems could coexist as long as semi-natural habitats are preserved and agricultural management maintained in its current practices. We emphasize the urgent need to conduct further studies integrating the socio-economic aspects in order to better predict future impacts of agricultural intensification processes on African farmland biodiversity.

Long-tailed Duck (Clangula hyemalis) ecology: insights from the Russian literature. Part 1: Asian part of the Russian breeding range

Long-tailed Ducks (Clangula hyemalis) nest in tundra habitats and are marine birds outside of the breeding season. These sea ducks are subject to negative impacts and threats throughout their annual cycle, and the population wintering in the Baltic Sea has declined dramatically in recent decades. To understand their life history and the drivers of population decreases, the ecology of Long-tailed Ducks needs to be understood in their breeding and wintering habitats. Most of the birds wintering in the Baltic Sea breed in northern Russia. Here, we reviewed the Russian literature on the Long-tailed Duck in the Asian part of the Russian breeding range (from Yamal to North East), with respect to their distribution, density, breeding and feeding biology. We summarized information from 74 Russian sources, with a strong representation of field surveys and ecological studies in the 1970s and 1980s. The data show a comparable overall breeding biology and timing within the area and compared to the European part of the breeding range. Considerable differences in the densities between sites and years were observed, but the underlying drivers of these differences are not yet understood. Overall, the proportions of non-breeding birds were high in most reports, but further studies are needed to understand the potential impact of changes in the breeding habitat on population trends. The data summarized here provide a comprehensive database for carrying out repeat surveys and ecological studies to improve understanding of population trends and their underlying ecological basis.

Wintering in the Western Subarctic Pacific Increases Mercury Contamination of Red-Legged Kittiwakes.

Marine methylmercury concentrations vary geographically and with depth, exposing organisms to different mercury levels in different habitats. Red-legged kittiwakes (Rissa brevirostris), a specialist predator, forage on fish and invertebrates from the mesopelagic zone, a part of the ocean with elevated methylmercury concentrations. We used kittiwakes as bioindicators of MeHg concentrations in remote mesopelagic systems by examining how wintering distribution and habitat affected kittiwakes' mercury exposure. In 2011-2017, we sampled winter-grown feathers on St. George Island, Alaska, from birds equipped with geolocation loggers. We measured total mercury (THg) and nitrogen stable isotopes in nape and head feathers grown during winter, respectively. THg concentration of kittiwake nape feathers averaged 4.61 ± 0.97 μg/g dry weight. Hierarchical cluster analysis was used to classify winter habitats with remotely sensed environmental variables along each bird's track. Five habitat clusters were identified. Birds that spent more time in the Western Subarctic Gyre and those that wintered further south had elevated THg concentrations. In contrast to THg, trophic level varied annually but did not show strong spatial patterns. Our results documented spatial variability in THg exposure based on the oceanic wintering locations of red-legged kittiwakes and highlight their use as a bioindicator of MeHg across ocean basins.

Recent Forest Cover Loss in the Core Zones of the Monarch Butterfly Biosphere Reserve in Mexico

The Monarch Butterfly Biosphere Reserve (MBBR) in central Mexico was established in 2000 to protect monarch butterfly (Danaus plexippus) overwintering colonies and contribute to the conservation of the monarch migratory phenomenon. Since it was decreed, the MBBR has faced deforestation pressures (forest cover loss) due to illegal logging and climatic factors. Here we report deforestation trends from 2012 to 2018 in the core zones of the MBBR where most monarch overwintering colonies perch. We used aerial ortho-photographs and satellite images complemented with field validation for temporal comparisons. During this period, 163.44 ha of forest cover were affected; 125.44 ha due to natural factors (rain and wind), 25.86 ha due to large-scale illegal logging, and 12.14 ha due to small-scale illegal logging. The core zone of the MBBR located in the State of Michoacan showed the highest deforestation values with 94.07 ha lost due to climatic factors, and 32.63 ha lost due to large-scale illegal logging. Over all illegal logging significantly decreased in the core zones of the MBBR due to an effective shared conservation effort including local communities, NGOs, academic institutions, governmental agencies, and philanthropists. Our study also showed a significant decrease of approximately 98% in large-scale illegal logging in the core zones of the MBBR compared to previous years from 2001 to 2012 (Vidal et al., 2013). Deforestation due to climatic factors remained similar (120 to 130 ha) between both studies. The decrease of deforestation during the period studied suggests that factors elsewhere rather than deforestation in the monarch butterfly’s winter habitat have strongly contributed to the dramatic population declines observed in recent years of monarch overwintering colonies since 2010.

Annual Winter Site Fidelity of Barrow's Goldeneyes in the Pacific

ABSTRACTCoastal regions on the Pacific north coast of North America provide important wintering habitat for many species of sea ducks. Although winter range and habitat preferences are well described for most species, fidelity to coastal wintering sites is generally undocumented. Fidelity is an important factor necessary for understanding interactions with coastal developments and activities and corresponding management strategies. We used data from Barrow's goldeneyes (Bucephala islandica), a sea duck that winters predominantly in nearshore habitats along the Pacific north coast, to investigate inter‐annual fidelity to, and intra‐annual fidelity within, coastal wintering sites. Between 2006 and 2015, we marked goldeneyes on breeding, molting, and wintering sites with satellite transmitters. We retained 4,931 locations in coastal habitats from 221 goldeneyes across 4 coastal regions for our analyses. These birds demonstrated high inter‐annual fidelity to coastal wintering sites; 75% of selected wintering sites were within 29 km of sites used the previous winter. Inter‐annual fidelity to wintering sites was similar between sex and age classes but differed by coastal region. Goldeneyes from southcentral Alaska, USA, expressed greater inter‐annual fidelity relative to birds from northern or southern British Columbia, Canada, and southeast Alaska. Goldeneyes also expressed high intra‐annual fidelity within wintering sites, with 75% of individuals averaging within‐season movements of ≤9 km. Intra‐annual fidelity was lesser for female than male goldeneyes but did not differ between hatch‐year and after‐hatch‐year birds. We found regional variation in intra‐annual fidelity, with goldeneyes from southcentral Alaska expressing greater intra‐annual fidelity compared to birds from other regions. High inter‐ and intra‐annual winter site fidelity by Barrow's goldeneyes suggests that, at a population level, habitat use is predictable and can be used to inform risk assessment or to evaluate factors affecting habitat choice. Also, low dispersal among wintering sites suggests that recovery from population perturbations, whether caused by natural or anthropogenic events, will be protracted. © 2019 The Wildlife Society.

Effects of land-use change on the distribution of the wintering red-crowned crane (Grus japonensis) in the coastal area of northern Jiangsu Province, China

The coastal area of northern Jiangsu (CNJ) is the largest silt coastal zone along the western Pacific Coast. This area is a newly established world natural heritage site and is also the largest winter habitat for the red-crowned crane in the world. However, rapid economic development in the study area has led to great changes in the types and intensities of land-use, which has had an effect on the distribution of wintering red-crowned cranes. In this paper, we first analyzed land-use change and determined the spatiotemporal evolution of land-use types and intensities in the study area. Then, the distribution of the red-crowned cranes was analyzed over various years. Finally, a geographically weighted regression (GWR) model was adopted to study the spatial differences in the effects of land-use types and intensity changes on the distribution of the cranes. The results showed that salt marsh (p<0.01), salt field (p<0.05) and paddy field (p<0.05) were positively correlated with red-crowned cranes. Dry land (p<0.05), construction land (p<0.01) and aquaculture pond (p<0.05) were negatively correlated with red-crowned cranes. There was a strongly negative correlation between land-use intensity and the red-crowned cranes (p<0.01). These positive and negative factors had significant spatial heterogeneity. Given these differences and the current local economic and land policies, we proposed the concrete countermeasures for red-crowned crane habitat protection and established a “friendly” land-use pattern that is beneficial for the protection of the crane population and restoration of its habitat.

Northern Yellowstone Mule Deer Seasonal Movement, Habitat Selection, and Survival Patterns

We determined the movement patterns and survival rates of 85 radio-marked adult female Rocky Mountain mule deer (Odocoileus hemionus hemionus) wintering on the Northern Yellowstone Winter Range (NYWR). We assessed seasonal movement and distribution patterns and individual fidelity to those patterns, along with seasonal habitat selection and survival rates. Twenty-three percent of the deer were nonmigratory, remaining on the winter range year-round, and 77% were migratory, moving 10–104 km from winter to summer ranges. No deer switched between migratory and nonmigratory status. All migratory deer that were monitored for ≥2 years exhibited traditional movement patterns and utilized the same winter and summer ranges in all years. Mean winter and summer home range sizes for migratory deer were 1076 ha (SE 129) and 1527 ha (SE 249), respectively, and mean home range size for resident deer was 3100 ha (SE 902). There was a dichotomy in winter habitat use, with one group of deer selecting cultivated and grassland vegetation land cover classes and a second group of deer selecting shrubland and grassland vegetation land cover classes. A dichotomy in summer habitat use was evident between those deer selecting for unburned forest and avoiding all burned land cover classes and those deer selecting for moderate and high burn intensity land cover classes and avoiding unburned forest. We estimated annual mean survival at 0.813 (SE 0.028) and found no differences in survival rates among migratory deer, nonmigratory deer, or deer exhibiting differences in winter or summer habitat selection patterns.

Multiple intrinsic markers identify carry-over effects from wintering to breeding sites for three Nearctic–Neotropical migrant swallows

Abstract Carry-over effects from one stage of the annual cycle to subsequent stages can have profound effects on individual fitness. In migratory birds, much research has been devoted to examining such effects from the nonbreeding to the breeding period. We investigated potential carry-over effects influencing spring body condition, breeding phenology, and performance for 3 species of sympatric, declining Nearctic–Neotropical migratory swallows: Bank Swallow (Riparia riparia), Barn Swallow (Hirundo rustica), and Cliff Swallow (Petrochelidon pyrrhonota). To examine carry-over effects, we used structural equation modeling and several intrinsic markers, including stable isotope (δ 2H, δ 13C, and δ 15N) and corticosterone (CORTf) values from winter molted-feathers, and changes in telomere length between breeding seasons. We found support for carry-over effects for all 3 species, however, the specific relationships varied between species and sexes. Effects leading to lower breeding performance were only observed in male Bank, female Barn, and female and male Cliff Swallows. In most cases, carry-over effects were attributed to differences in stable isotope values (most commonly with δ 2H) presumably related to differences in winter habitat use, but, for Cliff Swallows, negative carry-over effects were also linked to higher CORTf values and greater rates of telomere shortening. This work provides further support for the potential role of nonbreeding conditions on population declines, and indicates how multiple intrinsic markers can be used to provide information on ecological conditions throughout the annual cycle.

Effects of Natal Dispersal and Density-Dependence on Connectivity Patterns and Population Dynamics in a Migratory Network

Migratory species can be visualized as spatial networks with nodes representing regions and the populations that seasonally occupy them and links between seasonal subpopulations representing migratory connectivity. Connectivity is often regarded as a static property of a migratory network and visualized to evaluate the vulnerability of migratory populations to changes in specific regions. However if the network itself is a dynamical system, its connectivity can be an output of the system that may be changed by perturbations to the network. I constructed a regulated, tripartite network population model with breeding, winter, and migration route nodes that also includes natal dispersal and in which connectivity goes to a dynamical equilibrium. I investigated how natal dispersal as well as the relative regulation in different seasons affects connectivity patterns and the responses of the network population to simulated habitat loss. I found that when the population is primarily regulated by availability of habitat in only one season and natal dispersal was geographically constrained, connectivity patterns were unsymmetrical with weak (diffuse) connectivity from the non-regulating to regulating season and stronger connectivity in the other direction. Less-constrained natal dispersal always resulted in weak connectivity throughout. The overall magnitude of declines caused by habitat loss was determined by relative regulation and generally was not affected by natal dispersal although it was possible, with high natal dispersal, for loss of low-quality nodes in a non-regulating season to cause increases in network population size since the low-quality nodes were acting as an ecological trap. Although we expect that localness (i.e., the extent to which declines resulting from local winter habitat loss was concentrated in a small breeding area versus spread across a larger area) should be predicted by connectivity, localness was in fact hugely variable and affected by both regulation and natal dispersal and generally quite difficult to predict from the connectivity pattern. In summary, the complexity of the system meant that visualization of a network by itself, without knowledge of the underlying processes causing connectivity patterns, often does not provide a good indication of the vulnerability of the network or individual node populations to habitat loss.

What caused the strong increase of the winter population of the Dalmatian Pelican, Pelecanus crispus, in Iran in the last two decades?

The Dalmatian Pelican Pelecanus crispus is listed globally as “Near Threatened”. We used the results of the International Waterbird Census from 1998 to 2017 to find trends in wintering numbers. Of the 102 sites examined, 29 were classified as regular, 18 as irregular and 55 as occasional wintering habitats for the species. Both the population size and the geographical distribution increased in the second half of the study period. The Anzali Wetland Complex, Gomishan Marsh, Gorgan Bay and Miankaleh Wildlife Refuge, inlets and mangroves east of Jask, the east coast of Chabahar and inlets and mangroves west of Konarak were identified as the most important wintering areas of the Dalmatian Pelican in Iran. Wintering numbers increased from 300 to 1,100 in the 1970s and from c. 800 in the 1980s to c. 1,800 by 2006 and up to c. 10,000 in 2017. Thus, more than 37% of the global population of the species overwinters in Iran. A combination of a series of warm winters and delayed timing of cold spells appears to be responsible for the increase of the wintering population.

Quantifying the restoration success of wood introductions to increase coho salmon winter habitat

Abstract. Large wood (LW) addition is often part of fish habitat restoration projects. However, there is limited information about the spatial–temporal variability in hydraulic changes after LW additions. We investigated reach-scale hydraulic changes triggered after the addition of LW that are relevant to juvenile coho salmon survival. We used Nays2DH, an unsteady two-dimensional flow model, to quantify the patterns and magnitudes of changes of stream velocity and shear stress in three alluvial gravel reaches. The study sites are located in low-gradient reaches draining 5 to 16 km2 in the Oregon Coast Range. Survivable habitat was characterized in terms of critical swim speed for juvenile coho and bed stability considering the critical shear stress required to mobilize the median bed particle size. Model predictions indicated that survivable habitat during bankfull conditions, measured as the area with velocity below the critical swim speed for juvenile coho, increased by 95 %–113 % after the LW restoration. Bed stability also increased between 86 % and 128 % considering the shear stress required to mobilize the median bed particle size. Model predictions indicated more habitat created in the larger site; however, considering that wood would move more frequently in this site there appears to be a trade-off between the timing and the resilience of restoration benefits. Overall, this study quantifies how the addition of LW potentially changes stream hydraulics to provide a net benefit to juvenile salmonid habitat. Our findings are applicable to stream restoration efforts throughout the Pacific Northwest.