Songbirds are resilient to hurricane disturbed habitats during spring migration

The Gulf of Mexico is a conspicuous feature of the Neotropical–Nearctic bird migration system. Traveling long distances across ecological barriers comes with considerable risks, and mortality associated with intercontinental migration may be substantial, including that caused by storms or other adverse weather events. However, little, if anything, is known about how migratory birds respond to disturbance‐induced changes in stopover habitat. Isolated, forested cheniere habitat along the northern coast of the Gulf of Mexico often concentrate migrants, during weather conditions unfavorable for northward movement or when birds are energetically stressed. We expected hurricane induced degradation of this habitat to negatively affect the abundance, propensity to stopover, and fueling trends of songbirds that stopover in coastal habitat. We used spring banding data collected in coastal Louisiana to compare migrant abundance and fueling trends before (1993–1996 and 1998–2005) and after hurricanes Rita (2006) and Ike (2009). We also characterized changes in vegetative structure before (1995) and after (2010) the hurricanes. The hurricanes caused dramatic changes to the vegetative structure, which likely decreased resources. Surprisingly, abundance, propensity to stopover, and fueling trends of most migrant species were not influenced by hurricane disturbance. Our results suggest that: 1) the function of chenieres as a refuge for migrants after completing a trans‐Gulf flight may not have changed despite significant changes to habitat and decreases in resource availability, and 2) that most migrants may be able to cope with habitat disturbance during stopover. The fact that migrants use disturbed habitat points to their conservation value along the northern coast of the Gulf of Mexico.     

A place to land: spatiotemporal drivers of stopover habitat use by migrating birds

Migrating birds require en route habitats to rest and refuel. Yet, habitat use has never been integrated with passage to understand the factors that determine where and when birds stopover during spring and autumn migration. Here, we introduce the stopover‐to‐passage ratio (SPR), the percentage of passage migrants that stop in an area, and use 8 years of data from 12 weather surveillance radars to estimate over 50% SPR during spring and autumn through the Gulf of Mexico and Atlantic coasts of the south‐eastern US, the most prominent corridor for North America’s migratory birds. During stopovers, birds concentrated close to the coast during spring and inland in forested landscapes during autumn, suggesting seasonal differences in habitat function and highlighting the vital role of stopover habitats in sustaining migratory communities. Beyond advancing understanding of migration ecology, SPR will facilitate conservation through identification of sites that are disproportionally selected for stopover by migrating birds.     

Atmospheric trajectories and spring bird migration across the Gulf of Mexico

We examined the relationship between the longitude of peak arrival of trans-Gulf migrants on the northern coast of the Gulf of Mexico in spring and wind trajectories over the Gulf at three different altitudes (500, 1,500, and 2,500 m above ground level). We used data from 10 WSR-88D radars (weather surveillance radar-1988-Doppler) from Brownsville, Texas, to Key West, Florida, to record the time and longitude of peak arrival on the northern Gulf coast for four spring migrations (2001–2004). We used the National Oceanic Atmospheric Administration Air Resources Laboratory HYSPLIT transport and dispersion model at the READY Web site to generate backward, 24-h atmospheric trajectories based on archived atmospheric data for each trans-Gulf flight. The trajectories began at the geographic location where radar indicated the greatest concentrations of arriving migrants. Although the longitude of peak arrival varied, peak densities of most trans-Gulf migrants arrived on the northern coast near longitude 95°W. Regression analyses showed that the relationship between the longitude of peak trans-Gulf arrival and the direction of atmospheric trajectory was significant but weak at the 500-m level, where few migrants occurred, and was insignificant for the 1,500- and 2,500-m altitudes, where migrant densities were greater. We conclude that winds aloft over the Gulf have little influence on the longitude of peak trans-Gulf arrival on the northern coast of the Gulf of Mexico, and we speculate that the arrival pattern may reflect the trans-Gulf migration pathways that evolved during the Last Glacial Maximum.     

El Ni?o-Southern Oscillation Is Linked to Decreased Energetic Condition in Long-Distance Migrants

Predicting how migratory animals respond to changing climatic conditions requires knowledge of how climatic events affect each phase of the annual cycle and how those effects carry-over to subsequent phases. We utilized a 17-year migration dataset to examine how El Niño-Southern Oscillation climatic events in geographically different regions of the Western hemisphere carry-over to impact the stopover biology of several intercontinental migratory bird species. We found that migratory birds that over-wintered in South America experienced significantly drier environments during El Niño years, as reflected by reduced Normalized Difference Vegetation Index (NDVI) values, and arrived at stopover sites in reduced energetic condition during spring migration. During El Niño years migrants were also more likely to stopover immediately along the northern Gulf coast of the southeastern U.S. after crossing the Gulf of Mexico in small suboptimal forest patches where food resources are lower and migrant density often greater than larger more contiguous forests further inland. In contrast, NDVI values did not differ between El Niño and La Niña years in Caribbean-Central America, and we found no difference in energetic condition or use of coastal habitats for migrants en route from Caribbean-Central America wintering areas. Birds over-wintering in both regions had consistent median arrival dates along the northern Gulf coast, suggesting that there is a strong drive for birds to maintain their time program regardless of their overall condition. We provide strong evidence that not only is the stopover biology of migratory landbirds influenced by events during the previous phase of their life-cycle, but where migratory birds over-winter determines how vulnerable they are to global climatic cycles. Increased frequency and intensity of ENSO events over the coming decades, as predicted by climatic models, may disproportionately influence long-distance migrants over-wintering in South America.     

Stopover and fat deposition by North American wood-warblers (Parulinae) following spring migration over the Gulf of Mexico

Summary Length of stopover and rate of weight gain (fat deposition) were studied in several species of passerine birds that stopped in southwestern Louisiana along the northern coast of the Gulf of Mexico after a trans-Gulf flight. Fatdepleted birds were more common among the birds that arrived at our study site in southwest Louisiana, though variability characterized our samples. Migrants that landed after encountering opposing winds or rain over the northern Gulf of Mexico were, on average, fatter than migrants that landed when weather was favorable for continued migration. Some of the variation in the energetic condition of arrivals may be explained by the location where migrants initiated crossings. Our simulation of flight over the Gulf of Mexico showed that with following winds a warbler can cross the Gulf of Mexico from Yucatan with fat reserves to spare, and stronger tailwinds make flights from as far south as Honduras energetically permissible. The length of stay after a trans-Gulf flight was related to the extent of fat-depletion upon arrival: lean birds stayed longer than fat migrants. Migrants stopped over for 1–7 days and replenished energy reserves at rates that varied from 0.19 g/d for Hooded Warblers (Wilsonia citrina) to 0.87 g/d for Ovenbirds (Seiurus aurocapillus). Within each species, most individuals gained weight at a rapid rate, though a few individuals lost or maintained weight during their stay.     

Landscape‐scale habitat availability,and not local geography,predicts migratory landbird stopover across the Gulf of Maine

While it is clear that many migratory behaviors are shared across taxa, generalizable models that predict the distribution and abundance of migrating taxa at the landscape scale are rare. In migratory landbirds, ephemeral concentrations of refueling birds indicate that individual behaviors sometimes produce large epiphenomena in particular geographic locations. Identifying landscape factors that predict the distribution and abundance of birds during migratory stopover will both improve our understanding of the migratory process and assist in broad, regionally relevant conservation. In this study we used autumnal passerine stopover data from a five‐year period and eleven stopover sites across coastal Maine, USA, to test four broad hypotheses of migrant distribution and abundance that have been supported in other regions: a) the community characteristics of the pool of potential migrants, b) a site's local geography, c) landscape composition and configuration measured at different spatial scales, and d) interactions between these factors. Our final model revealed that birds concentrate at ‘habitat islands’, sites that possess a disproportionate percentage of the vegetated habitat in the 4‐km surrounding landscape. The strength of this pattern, however, was inversely proportional to a species' remaining migratory distance. Our results corroborate several studies that emphasize the importance of land cover composition at finer spatial scales (< 80 km²) for predicting the stopover distribution and abundances of migratory birds. This suggests that different migrants likely assess stopover sites with similar mechanisms along their migratory route, and these commonalities may be broadly applied to identify stopover locations of conservation importance across the continent.     

Effect of fuel deposition rate on departure fuel load of migratory songbirds during spring stopover along the northern coast of the Gulf of Mexico

Migrants are generally assumed to minimize their overall migration time by adjusting their departure fuel loads (DFL) in relation to anticipated and experienced fuel deposition rates (FDRs). We utilized a 21‐yr long migration banding station dataset to examine the relationship between FDR and DFL during spring migration in six Nearctic‐Neotropical migratory songbird species during stopover along the northern coast of the Gulf of Mexico (GOM) following trans‐gulf flight. Estimates of fuel stores, stopover durations, and FDRs from our long term migration data set were combined to determine DFL. We expected and found that migrants across all six species adjust their DFL to the rate at which they deposit fuel reserves. This robust finding suggests that songbird migrants are sensitive to time constraints during spring passage presumably to fine‐tune their stopover schedule in relation to experienced and anticipated habitat quality. Two of the species studied showed an effect of age on the FDR–DFL relationship: one was consistent with the expectation that older birds would be less sensitive to changes in FDR, while the second was contrary to our expectations and likely suggesting an age‐dependent response to habitat quality. We found sex‐dependent differences consistent with male DFL being more sensitive to FDR in only two of six species studied, and argue that both males and females are time constrained during spring passage in relation to arrival at breeding destinations. The positive relationship between FDR and DFL among all species and for age and sex groups in some species reflects a migration strategy sensitive to time.     

长距离迁徙鸟类对应于能量积累状态的取食行为调整

迁徙鸟类能够预计到迁徙过程中对能量需求的增加和迁徙途中获得能量的不确定性。最佳迁徙理论指出：迁徙停留期的一系列决策受到体内能量状态、取食机会和迁徙时间的影响。利用刚完成春季跨越墨西哥湾迁徙的鸫类,我们研究了取食行为、体内能量状态和能量积累速度的相互关系。我们用雾网捕获了停留的鸫,然后给每只鸟进行了环志和称重,并估测了表皮下积累的脂肪。为了检测体内能量积累大小对取食行为的影响,我们把在野外观察到的鸟分成肥、瘦两组。当一天里被捕获鸟的平均体重低于相关种的瘦体重时,这一天被观察到的取食鸟被归到瘦组,反之就属于肥组。我们同时对一部分鸟用有色环进行了标记,以便能在野外观察到它们时能准确地知道每一只鸟的初始能量积累状态。在春天完成跨越墨西哥湾迁徙以后的鸫大约有50％在到达停留地时就已经消耗了所有的表皮下脂肪。与肥组鸟相比,瘦组的个体在停留期扩展了取食方法和取食基底,增加了取食速度。与此相关的是,瘦鸟表现出体重积累更多、速度更快。我们的数据表明迁徙鸟在到达迁徙中途停留地时的能量状态会影响到它们停留期间的取食行为和继续迁徙时的生理机能,从而影响停留期的长短和在迁徙途中停留与否的决定[动物学报51(1)：12—23,2005]。     

Experimental evidence for the interplay of exogenous and endogenous factors on the movement ecology of a migrating songbird

Movement patterns during songbird migration remain poorly understood despite their expected fitness consequences in terms of survival, energetic condition and timing of migration that will carry over to subsequent phases of the annual cycle. We took an experimental approach to test hypotheses regarding the influence of habitat, energetic condition, time of season and sex on the hour-by-hour, local movement decisions of a songbird during spring stopover. To simulate arrival of nocturnal migrants at unfamiliar stopover sites, we translocated and continuously tracked migratory red-eyed vireos (Vireo olivaceus) throughout spring stopover with and without energetic reserves that were released in two replicates of three forested habitat types. Migrants moved the most upon release, during which time they selected habitat characterized by greater food abundance and higher foraging attack rates. Presumably under pressure to replenish fuel stores necessary to continue migration in a timely fashion, migrants released in poorer energetic condition moved faster and further than migrants in better condition and the same pattern was true for migrants released late in spring relative to those released earlier. However, a migrant's energetic condition had less influence on their behavior when they were in poor quality habitat. Movement did not differ between sexes. Our study illustrates the importance of quickly finding suitable habitat at each stopover site, especially for energetically constrained migrants later in the season. If an initial period prior to foraging were necessary at each stop along a migrant's journey, non-foraging periods would cumulatively result in a significant energetic and time cost to migration. However, we suggest behavior during stopover is not solely a function of underlying resource distributions but is a complex response to a combination of endogenous and exogenous factors.     

Fall migratory departure decisions and routes of blackpoll warblers Setophaga striata and red‐eyed vireos Vireo olivaceus at a coastal barrier in the Gulf of Maine

Each year, millions of songbirds concentrate in coastal areas during fall migration. The choices birds make at the coast about stopover habitat use and migratory route can influence both the success of their migratory journey and fitness in subsequent life stages. We made use of a regional‐scale automated radio telemetry array to study stopover and migratory flights and migratory routes of blackpoll warblers Setophaga striata and red‐eyed vireos Vireo olivaceus during fall migration in the Gulf of Maine, USA. We focused on differences between species, sexes, age groups, breeding origins, and time of year. Both species made within‐stopover relocations (i.e. ‘stopover flights’) from the coastal capture site. Stopover flights were primarily oriented inland, and were more frequent for blackpolls (87%) than vireos (44%). By studying migratory behavior at a broad spatial scale, we demonstrated that most blackpolls and vireos took coastal and offshore routes through the Gulf of Maine, despite initially relocating inland from the capture site. Though we captured blackpolls and vireos from a broad breeding range, more than 70% of migratory flights from the capture site were oriented for coastal or offshore travel for both species, suggesting that birds actively chose coastal and offshore routes, and were not simply displaced by wind drift. Later vireos oriented offshore more frequently during migratory flights from the coast, indicating that they may be more inclined towards time‐minimizing overwater flight routes and thus more exposed to coastal and offshore collision hazards than earlier conspecifics.     

Fuel reserves affect migratory orientation of thrushes and sparrows both before and after crossing an ecological barrier near their breeding grounds

Fat reserves influence the orientation of migrating songbirds at ecological barriers, such as expansive water crossings. Upon encountering a body of water, fat migrants usually cross the barrier exhibiting 'forward' migration in a seasonally appropriate direction. In contrast, lean birds often exhibit temporary 'reverse' orientation away from the water, possibly to lead them to suitable habitats for refueling. Most examples of reverse orientation are restricted to autumn migration and, in North America, are largely limited to transcontinental migrants prior to crossing the Gulf of Mexico. Little is known about the orientation of lean birds after crossing an ecological barrier or on the way to their breeding grounds. We examined the effect of fat stores on migratory orientation of both long- and short-distance migrants before and after a water crossing near their breeding grounds; Catharus thrushes (Swainson's and gray-cheeked thrushes, C. ustulatus and C. minimus ) and white-throated sparrows Zonotrichia albicollis were tested for orientation at the south shore of Lake Ontario during spring and autumn. During both spring and autumn, fat birds oriented in a seasonally appropriate, forward direction. Lean thrushes showed a tendency for reverse orientation upon encountering water in the spring and axial, shoreline orientation after crossing water in the autumn. Lean sparrows were not consistently oriented in any direction during either season. The responses of lean birds may be attributable to their stopover ecology and seasonally-dependent habitat quality.     

红胁蓝尾鸲(Tarsiger cyanurus)在中国东北部帽儿山地区的迁徙中途停歇生态

中国迁徙鸣禽类的保护面对着与世界其他地区如欧洲和北美洲鸟类保护相似的挑战。迁徙鸣禽类具有复杂生活周期和很大的空间关联。迁徙过程中发生的事件对迁徙鸣禽类种群动态具有决定作用。对于鸣禽类迁徙中途停歇期的生态,比如停歇期的长短,能量的积累,生境的利用等,了解还非常有限。在中国东北部的一个鸟类迁徙停歇地对红胁蓝尾鸲(Tarsiger cyanurus)的中途停歇生态包括迁徙时间、停歇时间、能量状态和性比进行了研究。2002年秋和2003年春分别捕获了1751只和684只红胁蓝尾鸲。红胁蓝尾鸲的体重在秋季迁徙时要比在春季迁徙时重。春季雌性红胁蓝尾鸲停歇时的能量状态指数最低; 而秋季的红胁蓝尾鸲比春季的红胁蓝尾鸲停歇时间更长。无论季节和性别,红胁蓝尾鸲的能量状态指数和第1次捕获的时间早晚成正相关, 间接证明红胁蓝尾鸲在停歇期间能够比较快地积累能量。秋季雄性红胁蓝尾鸲日体重净增率最大。估测秋季停歇期的每日能量净增能维持红胁蓝尾鸲雌性0.6h和雄性3.1h的飞行。红胁蓝尾鸲的中途停歇生态与北美和欧洲一些迁徙鸣禽类很相似。比如,春季迁徙过境的时间和脂肪积累的变化与自然选择对雄性的要求：当食物和气候适宜时尽快到达繁殖地的假设是一致的。对迁徙中途的停歇生态研究有利于更好地了解鸟类的迁徙行为和更有效地保护迁徙鸣禽类。     

红胁蓝尾鸲(Tarsiger cyanurus)在中国东北部帽儿山地区的迁徙中途停歇生态

中国迁徙鸣禽类的保护面对着与世界其他地区如欧洲和北美洲鸟类保护相似的挑战.迁徙鸣禽类具有复杂生活周期和很大的空间关联.迁徙过程中发生的事件对迁徙鸣禽类种群动态具有决定作用.对于鸣禽类迁徙中途停歇期的生态,比如停歇期的长短,能量的积累,生境的利用等,了解还非常有限.在中国东北部的一个鸟类迁徙停歇地对红胁蓝尾鸲（Tarsiger cyanurus）的中途停歇生态包括迁徙时间、停歇时间、能量状态和性比进行了研究.2002年秋和2003年春分别捕获了1751只和684只红胁蓝尾鸲.红胁蓝尾鸲的体重在秋季迁徙时要比在春季迁徙时重.春季雌性红胁蓝尾鸲停歇时的能量状态指数最低;而秋季的红胁蓝尾鸲比春季的红胁蓝尾鸲停歇时间更长.无论季节和性别,红胁蓝尾鸲的能量状态指数和第1次捕获的时间早晚成正相关,间接证明红胁蓝尾鸲在停歇期间能够比较快地积累能量.秋季雄性红胁蓝尾鸲日体重净增率最大.估测秋季停歇期的每日能量净增能维持红胁蓝尾鸲雌性0.6h和雄性3.1h的飞行.红胁蓝尾鸲的中途停歇生态与北美和欧洲一些迁徙鸣禽类很相似.比如,春季迁徙过境的时间和脂肪积累的变化与自然选择对雄性的要求：当食物和气候适宜时尽快到达繁殖地的假设是一致的.对迁徙中途的停歇生态研究有利于更好地了解鸟类的迁徙行为和更有效地保护迁徙鸣禽类.     

Inter-island variation in the diet of female northern fur seals (Callorhinus ursinus) in the Bering Sea

The diet of adult female northern fur seals ( Callorhinus ursinus ) is examined through the analysis of faecal material collected during the summer breeding season at three breeding locations in the Bering Sea: St. Paul Island (1988, 1990) and St. George Island (1988, 1990) of the Pribilof Islands Group (USA), and Medny Island (1990) of the Commander Islands Group (Russia). Prey consumption varies annually and accordingly with the physical and biological environment surrounding each island. Juvenile walleye pollock ( Theragra chalcogramma ) is the most common prey of northern fur seals from St. Paul Island; the island is surrounded by a broad neritic environment with widely separated frontal zones and is the greatest distance from the continental shelf-edge. Gonatid squid ( Gonatopsis borealis/Berryteuthis magister and Gonatus madokail Gonatus middendorffi ) were the most common prey of northern fur seals from Medny Island; the island is surrounded by a compressed neritic environment and is adjacent to the continental shelf-edge and the oceanic marine environment. A combination of walleye pollock and gonatid squid is consumed by northern fur seals from St. George Island; the island has a surrounding oceanographic environment intermediate between the other two islands.
Variability in predation on walleye pollock is consistent with fishery information concerning the relative abundance and availability of walleye pollock around St. George and St. Paul Islands. The abundance and availability of these prey resources during the summer breeding season are key factors which influence the health and growth of the northern fur seal populations in the Bering Sea.     

Effects of storm frequency on dune vegetation

In the Gulf of Mexico, barrier islands absorb the majority of wind and wave action from storms, which modifies their dune morphology and vegetation dynamics. Storm frequency is predicted to increase as a result of climate change, yet the effects of this change on coastal ecosystems remain poorly understood. Using estimates of plant growth in storm and nonstorm years from long‐term census data describing the dynamics of dune vegetation on St. George Island, FL, we built a first‐order model that predicts how dune communities will respond to a change in storm frequency. It predicts that an increasing frequency of storms will result in a change in the vegetation across the dunes. The fore‐ and interdune communities are predicted to become more similar to one another through the dominance of a small number of common storm‐resilient species. Alternatively, the backdune community is predicted to become more distinct through an increase in rare species that represent primary succession. Finally, the model predicts that many species will not respond to an increase in the number of storms per year in the same manner in which they respond to current storm frequency. This model is beneficial both for the development of more complex approaches to predicting effects of climate change and for informing preventative management techniques.     

Lessons from the Tōhoku tsunami: A model for island avifauna conservation prioritization

Earthquake‐generated tsunamis threaten coastal areas and low‐lying islands with sudden flooding. Although human hazards and infrastructure damage have been well documented for tsunamis in recent decades, the effects on wildlife communities rarely have been quantified. We describe a tsunami that hit the world's largest remaining tropical seabird rookery and estimate the effects of sudden flooding on 23 bird species nesting on Pacific islands more than 3,800 km from the epicenter. We used global positioning systems, tide gauge data, and satellite imagery to quantify characteristics of the Tōhoku earthquake‐generated tsunami (11 March 2011) and its inundation extent across four Hawaiian Islands. We estimated short‐term effects of sudden flooding to bird communities using spatially explicit data from Midway Atoll and Laysan Island, Hawai'i. We describe variation in species vulnerability based on breeding phenology, nesting habitat, and life history traits. The tsunami inundated 21%–100% of each island's area at Midway Atoll and Laysan Island. Procellariformes (albatrosses and petrels) chick and egg losses exceeded 258,500 at Midway Atoll while albatross chick losses at Laysan Island exceeded 21,400. The tsunami struck at night and during the peak of nesting for 14 colonial seabird species. Strongly philopatric Procellariformes were vulnerable to the tsunami. Nonmigratory, endemic, endangered Laysan Teal (Anas laysanensis) were sensitive to ecosystem effects such as habitat changes and carcass‐initiated epizootics of avian botulism, and its populations declined approximately 40% on both atolls post‐tsunami. Catastrophic flooding of Pacific islands occurs periodically not only from tsunamis, but also from storm surge and rainfall; with sea‐level rise, the frequency of sudden flooding events will likely increase. As invasive predators occupy habitat on higher elevation Hawaiian Islands and globally important avian populations are concentrated on low‐lying islands, additional conservation strategies may be warranted to increase resilience of island biodiversity encountering tsunamis and rising sea levels.     

Energy reserves stored by migrating Gray‐cheeked Thrushes Catharus minimus at a spring stopover site in northern Colombia are sufficient for a long‐distance flight to North America

Stopover sites used to accumulate the energy that fuels migration, especially those used prior to crossing ecological barriers, are regarded as critically important for the survival of Nearctic?Neotropical migratory birds. To assess whether South American stopover sites are used to store the energy required to cross the Caribbean Sea and the Gulf of Mexico to North America by a Neotropical migratory landbird, we studied Gray‐cheeked Thrushes in northern Colombia through constant effort mist‐netting during spring migration in 2010 and 2011. We combined stopover duration estimates and models of body mass change based on recaptures to estimate departure body mass and potential flight range from our study site. We recaptured 62 birds, the majority of which gained mass. Models indicated significant differences in rates of mass gain between years and age groups and with arrival date. Estimated total stopover durations varied between 15.4 (2010) and 12.5 days (2011). Predicted departure mass ranged between 41.3 and 44.9 g, and potential flight range was estimated at between 2727 and 4270 km. Gray‐cheeked Thrushes therefore departed our study site with sufficient energy reserves to cross the Caribbean Sea and the Gulf of Mexico (2550 km). As the first demonstration that birds departing from South American stopover sites can reach North America without refuelling, this has important implications for stopover site protection. Strategic conservation measures in the Sierra Nevada de Santa Marta could protect habitats in which up to 40% of the energy required to complete spring migration is stored by a Neotropical migratory land bird.     

Comparison of autumn and spring migration strategies of Neotropical migratory landbirds in northeast Belize

ABSTRACT Migration represents one of the most vulnerable stages of a migrant's life cycle, but the strategies and stopover sites used by Neotropical migrants in Central America are not well known. We carried out constant‐effort mist netting and conducted censuses along transects during one autumn (2007) and one spring (2008) migration in northeast Belize. We recorded more landbird migrant species in autumn (63) than in spring (54), and spring abundance was >25% lower for 88% of transient species. These differences in presence and abundance indicate that routes and stopover strategies vary between seasons and species. In autumn, fuel loads, calculated as any increase in mass above lean body mass (LBM), were generally small (mean = 5.9% LBM and 10.1% LBM for wintering and transient species, respectively) and fuel deposition rates and minimum stopover durations suggest that some individuals replenished energy reserves in our study area. Variation in autumn fuel loads meant that some individuals had reserves sufficient for flights >1000 km. Fuel loads were larger in spring for 16 of 17 species, and the mean spring fuel load for transient species (32.5% LBM) was sufficient for a flight from northeast Belize to North America without refueling. The similarity in spring passage times between northeast Belize and the Gulf Coast of the United States also suggests that energy reserves were not replenished in northeast Belize prior to crossing the Gulf of Mexico. We hypothesize that sufficient energy reserves are accumulated during spring stopovers in northern South America or elsewhere in Mesoamerica to allow migrants to fly directly to North America without refueling.     

Ecological niche modeling of coastal dune plants and future potential distribution in response to climate change and sea level rise

Climate change (CC) and sea level rise (SLR) are phenomena that could have severe impacts on the distribution of coastal dune vegetation. To explore this we modeled the climatic niches of six coastal dunes plant species that grow along the shoreline of the Gulf of Mexico and the Yucatan Peninsula, and projected climatic niches to future potential distributions based on two CC scenarios and SLR projections. Our analyses suggest that distribution of coastal plants will be severely limited, and more so in the case of local endemics (Chamaecrista chamaecristoides, Palafoxia lindenii, Cakile edentula). The possibilities of inland migration to the potential ‘new shoreline’ will be limited by human infrastructure and ecosystem alteration that will lead to a ‘coastal squeeze’ of the coastal habitats. Finally, we identified areas as future potential refuges for the six species in central Gulf of Mexico, and northern Yucatán Peninsula especially under CC and SLR scenarios.     

Artificial light at night confounds broad‐scale habitat use by migrating birds

With many of the world's migratory bird populations in alarming decline, broad‐scale assessments of responses to migratory hazards may prove crucial to successful conservation efforts. Most birds migrate at night through increasingly light‐polluted skies. Bright light sources can attract airborne migrants and lead to collisions with structures, but might also influence selection of migratory stopover habitat and thereby acquisition of food resources. We demonstrate, using multi‐year weather radar measurements of nocturnal migrants across the northeastern U.S., that autumnal migrant stopover density increased at regional scales with proximity to the brightest areas, but decreased within a few kilometers of brightly‐lit sources. This finding implies broad‐scale attraction to artificial light while airborne, impeding selection for extensive forest habitat. Given that high‐quality stopover habitat is critical to successful migration, and hindrances during migration can decrease fitness, artificial lights present a potentially heightened conservation concern for migratory bird populations.