Multi-year change and annual variation in fall migratory timing of songbirds captured across a 19-year time span in northeastern Pennsylvania, USA

1. In migratory species, early arrival on the breeding grounds can often enhance breeding success. Timing of spring migration is therefore a key process that is likely to be influenced both by factors specific to individuals, such as the quality of winter and breeding locations and the distance between them, and by annual variation in weather conditions before and during migration. 2. The Icelandic black-tailed godwit Limosa limosa islandica population is currently increasing and, throughout Iceland, is expanding into poorer quality breeding areas. Using a unique data set of arrival times in Iceland in different years for individuals of known breeding and wintering locations, we show that individuals breeding in lower quality, recently occupied and colder areas arrive later than those from traditionally occupied areas. The population is also expanding into new wintering areas, and males from traditionally occupied winter sites also arrive earlier than those occupying novel sites. 3. Annual variation in timing of migration of individuals is influenced by large-scale weather systems (the North Atlantic Oscillation), but between-individual variation is a stronger predictor of arrival time than the NAO. Distance between winter and breeding sites does not influence arrival times. 4. Annual variation in timing of migration is therefore influenced by climatic factors, but the pattern of individual arrival is primarily related to breeding and winter habitat quality. These habitat effects on arrival patterns are likely to operate through variation in individual condition and local-scale density-dependent processes. Timing of migration thus appears to be a key component of the intricate relationship between wintering and breeding grounds in this migratory system.

We analysed 12 years of data on the spring migration of the common toad Bufo bufo L. to breeding ponds across 25 locations in Derbyshire, UK, to determine factors influencing the number of toads active per night. We also tested whether the timing of spring migration is predicted by annual variation in temperature or precipitation. More toads migrate in warmer temperatures and as the moon waxes, whereas precipitation did not have a significant effect on toad activity. Across years, spring migration begins earlier in warmer years, but the main migration of toads was not predicted by air temperatures before the onset of the breeding season. Contrary to the majority of studies of amphibian breeding phenology, there has been a temporal shift towards later timing of breeding over the past 12 years. Overall, comparison of our results with that of previous studies suggests that it can be difficult to generalize about the factors that influence breeding phenology, even within species. However, as more studies accumulate, it should be possible to address whether variation in breeding phenology is consistently linked to geographic variation in abiotic conditions or species biology, which will help to evaluate its consequences under climate change.

Mountain forests are important carbon stocks and biodiversity hotspots but are threatened by increased insect outbreaks and climate‐driven forest conversion. Soil microorganisms play an eminent role in nutrient cycling in forest habitats and form the basis of soil food webs. Uncovering the driving factors shaping microbial communities and functioning at mountainsides across the world is of eminent importance to better understand their dynamics at local and global scales. We investigated microbial communities and their climatic and local soil‐related drivers along an elevational gradient (800–1700 m asl) of primary forests at Changbai Mountain, China. We analyzed substrate‐induced respiration and phospholipid fatty acids (PLFA) in litter and two soil layers at seven sites. Microbial biomass (Cmic) peaked in the litter layer and increased towards higher elevations. In the litter layer, the increase in Cmic and in stress indicator ratios was negatively correlated with Ca concentrations indicating increased nutritional stress in high microbial biomass communities at sites with lower Ca availability. PLFA profiles in the litter layer separated low and high elevations, but this was less pronounced in soil, suggesting that the litter layer functions as a buffer for soil microbial communities. Annual variations in temperature correlated with PLFA profiles in all three layers, while annual variations in precipitation correlated with PLFA profiles in upper soil only. Furthermore, the availability of resources, soil moisture, Ca concentrations, and pH structured the microbial communities. Pronounced changes in Cmic and stress indicator ratios in the litter layer between pine‐dominated (800–1100 m) and spruce‐dominated (1250–1700 m) forests indicated a shift in the structure and functioning of microbial communities between forest types along the elevational gradient. The study highlights strong changes in microbial community structure and functioning along elevational gradients, but also shows that these changes and their driving factors vary between soil layers. Besides annual variations in temperature and precipitation, carbon accumulation and nitrogen acquisition shape changes in microbial communities with elevation at Changbai Mountain.

Animal migration is one of the most spectacular and visible behavioural phenomena in nature with profound implications for a range of ecological and evolutionary processes. Successful migration hinges on the ability to exploit temporary resources (e.g. food) and evade threats (e.g. predators) as they arise, and thus the timing of migration is often regarded as a dominant predictor of individual migratory success.However, with the exception of intensively studied taxa (mainly birds), relatively few studies have investigated inter‐individual annual and seasonal variation in migratory timing and performance, or tested predictions on how migration across high and low predation‐risk habitats may exert selection on migratory timing. In particular, studies that assess the survival consequences of variation in migratory timing remain rare, which is most likely due to the logistical challenges associated with monitoring survival success and population‐level characteristics simultaneously.Here, we address the above‐mentioned questions using roach Rutilus rutilus, a fish that migrates from lakes characterised by high predation risk into low‐risk streams during winter. Specifically, we used individual‐based tracking of roach in two European lake systems over multiple migration periods (9 and 7 years respectively), to obtain highly detailed (year‐round scheduling, repeat journeys and the fate of individuals) data on the variability/synchrony of migratory timing in spring and autumn respectively.We report seasonal differences in the variability of migratory timing, with lower variance and higher migration synchrony in spring lake arrival timing as compared to autumn lake departure timing. Furthermore, the timing of autumn migration is more variable across years than the timing of spring migration. Second, we find that later arrival to the lake habitat is positively associated with apparent survival from 1 year to the next, whereas we found no effect of lake departure timing on survival probability.These findings represent rare evidence showing how intraspecific variation in timing in migratory fish differs across years and seasons, and how variation in timing can translate into survival consequences for prey in systems characterised by high predation risk.

ABSTRACTIdentifying environmental metrics specific to lesser scaup (Aythya affinis; scaup) spring migration chronology may help inform development of conservation, management and population monitoring. Our objective was to determine how environmental conditions influence spring migration of lesser scaup to assess the effectiveness of the Waterfowl Breeding Population and Habitat Survey in accurately estimating scaup populations. We first compared peak timing of mallard (Anas platyrhynchos) and scaup migration from weekly ground surveys in North Dakota, USA because the Waterfowl Breeding Population and Habitat Survey is designed to capture annual mallard migration. As predicted, we detected that peak timing of scaup and mallard migrations differed in 25 of 36 years investigated (1980–2010). We marked scaup with satellite transmitters (n = 78; 7,403 locations) at Long Point, Lake Erie, Ontario, Canada; Pool 19 of the Mississippi River, Iowa and Illinois, USA; and Presque Isle Bay, Lake Erie, Pennsylvania, USA. We tested the assumption that our marked scaup were representative of the continental population using the traditional survey area by comparing timing of migration of marked birds and scaup counted in the North Dakota Game and Fish Department survey. We detected a strong positive correlation between marked scaup and the survey data, which indicated that marked scaup were representative of the population. We subsequently used our validated sample of marked scaup to investigate the effects of annual variation in temperature, precipitation, and ice cover on spring migration chronology in the traditional and eastern survey areas of the Waterfowl Breeding Population and Habitat Survey, 2005–2010. We evaluated competing environmental models to explain variation in timing and rate of scaup migration at large‐scale and local levels. Spring migration of scaup occurred earlier and faster during springs with warmer temperatures and greater precipitation, variables known to influence energy budgets and wetland availability. Our results suggest that surveys designed to index abundance of breeding mallards is imprecise for estimating scaup abundance, and inaccurate at estimating breeding population size by survey stratum. © 2016 The Wildlife Society.

The long-term advance in the timing of bird spring migration in the Northern Hemisphere is associated with global climate change. The extent to which changes in bird phenology reflect responses to weather conditions in the wintering or breeding areas, or during migration, however, remains to be elucidated. We analyse the relationships between the timing of spring migration of 9 species of trans-Saharan migratory birds across the, Mediterranean, and thermal and precipitation anomalies in the main wintering areas south of the Sahara Desert and in North African stopover areas. Median migration dates were collected on the island of Capri (southern Italy) by standardized mist-netting during 1981 to 2004. High temperatures in sub-Saharan Africa (Sahel and Gulf of Guinea) prior to northward migration (February and March) were associated with advanced migration. Moreover, birds migrated earlier when winter rainfall in North Africa was more abundant. The relationships between relevant meteorological variables and timing of migration were remarkably consistent among species, suggesting a coherent response to the same extrinsic stimuli. All these results were obtained while statistically controlling for the long-term trend towards the earlier timing of spring migration across the Mediterranean that has been documented in previous analyses of the same dataset, a trend that was confirmed by the present analyses. In conclusion, our results suggest that thermal conditions in the wintering quarters, as well as rainfall in North African stopover areas, can influence interannual variation in migration phenology of trans-Saharan migratory birds, although the ecological mechanisms that causally link meteorological conditions to the timing of migration remain a matter of speculation.

We studied long‐term trends and the yearly variation in mean spring passage time in 36 passerine bird species trapped at Ottenby Bird Observatory in south‐eastern Sweden. Between the years 1952–2002, data were available for 22–45 years depending on species. Most long‐distance migrant species passed progressively earlier over the study period (range: 2.5 days earlier to 0.7 days later per 10 years, with an average of 0.9 days earlier per 10 years). The annual variation in timing of migration in most species, regardless of migration distance, correlated negatively with the winter index of the North Atlantic Oscillation (NAO), a large‐scale climate phenomenon influencing the climate in the North Atlantic region. Birds passed earlier after mild and humid winters, corresponding to the high phase of the NAO. This corroborates the pattern found at a nearby migration site with a comparable dataset (Helgoland, 600 km WSW of Ottenby). However, short/medium‐distance migrant species at Ottenby, in contrast to the situation at Helgoland, have shown no general trend of earlier passage in recent years. This was probably a consequence of the shorter study period at Ottenby, which included only the last 22–32 years (41 years at Helgoland), when the NAO showed no significant trend. At the species‐specific level, the long‐term trends in passage time were similar at the two sites, and there was some congruence to the extent that a given species was affected by NAO. Long‐distance migrants wintering south and south‐east of the breeding grounds showed some of the strongest changes in long‐term trends (passing progressively earlier) at Ottenby, and for some of these species passage time varied negatively with NAO. Obviously, and contrary to previous suggestions, variations in NAO also influence birds migrating through eastern Europe, although the direct or indirect mechanisms through which this is achieved are unknown.

AimPhenological mismatches, when life‐events become mistimed with optimal environmental conditions, have become increasingly common under climate change. Population‐level susceptibility to mismatches depends on how phenology and phenotypic plasticity vary across a species’ distributional range. Here, we quantify the environmental drivers of colour moult phenology, phenotypic plasticity, and the extent of phenological mismatch in seasonal camouflage to assess vulnerability to mismatch in a common North American mammal.LocationNorth America.Time period2010–2017.Major taxa studiedSnowshoe hare (Lepus americanus).MethodsWe used > 5,500 by‐catch photographs of snowshoe hares from 448 remote camera trap sites at three independent study areas. To quantify moult phenology and phenotypic plasticity, we used multinomial logistic regression models that incorporated geospatial and high‐resolution climate data. We estimated occurrence of camouflage mismatch between hares’ coat colour and the presence and absence of snow over 7 years of monitoring.ResultsSpatial and temporal variation in moult phenology depended on local climate conditions more so than on latitude. First, hares in colder, snowier areas moulted earlier in the fall and later in the spring. Next, hares exhibited phenotypic plasticity in moult phenology in response to annual variation in temperature and snow duration, especially in the spring. Finally, the occurrence of camouflage mismatch varied in space and time; white hares on dark, snowless background occurred primarily during low‐snow years in regions characterized by shallow, short‐lasting snowpack.Main conclusionsLong‐term climate and annual variation in snow and temperature determine coat colour moult phenology in snowshoe hares. In most areas, climate change leads to shorter snow seasons, but the occurrence of camouflage mismatch varies across the species’ range. Our results underscore the population‐specific susceptibility to climate change‐induced stressors and the necessity to understand this variation to prioritize the populations most vulnerable under global environmental change.

How similar are annual and summer temperature variability in central Sweden?

In order to evaluate the effect of the penetration of diurnal and annual wave temperature into the subsurface, the temperature has been monitored at an hourly recording frequency at depths of 40, 60 and 78 m between summer 2016 and summer 2018, at the geothermal experimental test site “Neutra” of the Georg-August-University of Göttingen, Germany. It has been asserted that the mean temperature gradient between 40 and 78 m continuously increases, because the temperature decreases at 40 m. The decrease can be explained by an increase in vegetation cover (trees, shrubs, etc.) in the perimeter of the test area, increasing the absorption of solar energy by the leaves. During the phenological growth season the diurnal temperature variation at the surface can be recorded in phase with opposite sign, even at a depth of 40 m, and the drop of the temperature at 40 m, when surface temperature reaches a value of nearly 9 °C, can be observed during small events of eco-dormancy during winter. The annual surface temperature variation of ±10 K induce the same effect with an amplitude of ±2mK at 40 m. It is stated that the dormant state of the vegetation cells is the reason of the annual variation of the residual temperature. At greater depths groundwater flows prevail and influence the temperature according to the structural properties of the encountered lithologies and the precipitation. The vegetation can transfer the daily and seasonal temperature variation to larger depths than expected based on the theory of heat conduction. This timely variation of the temperature gradient demonstrates that the determination of the terrestrial heat flow density is subject to several impacts induced from the surface as well as from the Earth’s interior. As a conclusion, temperature gradients determined at shallow depths may be influenced by changes in surface coverage.

In this paper, finite element method (FEM) of axisymmetric linear elastic model has been used to calculate the tilt and strain induced by small annual temperature variations in a deep tunnel. The results show that even if the amplitude of the annual variation meets the construction standard of seismic station issued by China Earthquake Administration (the annual temperature variation amplitude in the tunnel is no more than 0.5 °C), a small annual temperature variation of amplitude just 0.2 °C in the tunnel would produce 10−7 rad changes in tilt and 10−7 changes in strain. Especially, at the end and the corner of the tunnel, changes of tilt and strain can be even larger. Therefore, in the future, it is an important task to reduce the annual temperature variation in the tunnel as far as possible. Within the tunnel, for both baseline instrument and pendulum instrument, the modeling suggests ways of construction of the tunnel and installation of the instrument to decrease the influence of the annual temperature variation.

Temperature changes at depths to 150 metres near the active crater of Aso Volcano: preliminary analysis of seasonal and volcanic effects

The life and time of clams: Derivation of intra-annual growth rates from high-resolution oxygen isotope profiles

Under laboratory conditions, two mechanisms have been identified that control the onset of migration. One mechanism inflexibly controls the initiation of migration, while the other requires external input from a changing environment. It has been suggested that the evolution of these mechanisms has an ecological basis related to the wintering latitude of the species. To establish whether the timing of migration was consistent with this ecological explanation, we studied the long-term mean timing of spring migration, and within-year and among-year variance in timing, in 27 free-living Nearctic migrant species. Species that wintered in higher, temperate latitudes migrated significantly earlier than tropical-wintering species. Tropical-wintering species showed significantly less within-year and among-year variation in the timing of migration, suggesting that the mechanism regulating their migration is primarily endogenous, with little influence of external stimuli. In contrast, breeding latitude showed no relationship to the mean date of migration, or the within-year or among-year variation in timing. These results are consistent with the notion that conditions that indicate time-of-year are unreliable or change imperceptibly (photoperiod) in the tropics, making an endogenous circannual clock valuable for controlling the onset and progression of migration. Temperate-wintering species were more likely to show interspecific correlations in timing than tropical species, further suggesting that external cues modulate spring migration in temperate-wintering species. Our results indicate that the migration regulation system employed might be ultimately determined by wintering latitude and associated environmental cues.

Understanding the effects of environmental variation on insect populations is important in light of predictions about increasing climatic variability. This paper uses the univoltine western corn rootworm (WCR, Diabrotica virgifera virgifera LeConte) as a case study and employs deterministic and stochastic modeling to evaluate how insect population dynamics is shaped by density‐dependent survival and annual variation in temperature, which are key in regulating insect populations. Field data showed that larval survival varied significantly between years but was constant for a range of densities. Survival dropped only beyond a threshold density, a feature resembling generalized Ricker functions used in modeling density‐dependent survival due to scramble competition for resources. We used soil temperature data for 20 yr to model annual variation in developmental time and survival. The deterministic model, where the developmental time was same across years, showed that though survival was high and did not change for a range of densities (i.e., density‐independent survival), predicted densities were large enough that strong density dependence could occur in the field (i.e., predicted densities fall in the region where survival drops sharply) and that populations could exhibit stable equilibrium, cycles, etc. Interestingly, populations with lower density‐independent survival were less likely to produce stable equilibrium compared to populations with higher density‐independent survival. We found that population densities were at stable equilibrium when both mean developmental time and fertility were relatively low or when developmental time and fertility were relatively high. This in turn implies that, in warmer regions, where mean developmental time will be lower, stability is more likely for insect populations with low fertility; species in warmer regions will experience cyclical and unstable dynamics when fertility is high. While increase in the mean developmental time reduces overall survival, increasing variation in developmental time could increase mean survival, a consequence of the Jensen's inequality, since survival was a concave decreasing function of developmental time. Hence, both mean and variability in temperature affect the dynamics of insect populations. Finally, we found that stochastic variation in soil temperature produced large variation in predicted population densities that could potentially enhance or diminish the effect of density dependence.