Flowering plant phenology and weather in Alberta,Canada

Plant phenology can be used for biomonitoring climate change. The flowering of certain temperate zone plant species occurs in response to accumulated heat. Networks of observers presently provide data on the timing of the growth of native and crop plants to Agro-meteorological Departments in Europe and the United States. In Alberta, a phenological survey which began in 1987 records flowering times for 15 native plants, with about 200 volunteers contributing observations annually. Six years of data have been summarized and correlated with temperature measurements. The Alberta phenological data can provide a key to sound decision-making in two ways: by providing proxy data on key variables to which vegetation responds, and by providing a model for transforming simple weather data into biologically meaningful zones.     

The role of citizen science in monitoring biodiversity in Ireland

Citizen science is proving to be an effective tool in tracking the rapid pace at which our environment is changing over large geographic areas. It is becoming increasingly popular, in places such as North America and some European countries, to engage members of the general public and school pupils in the collection of scientific data to support long-term environmental monitoring. Participants in such schemes are generally volunteers and are referred to as citizen scientists. The Christmas bird count in the US is one of the worlds longest running citizen science projects whereby volunteers have been collecting data on birds on a specific day since 1900. Similar volunteer networks in Ireland have been in existence since the 1960s and were established to monitor the number and diversity of birds throughout the country. More recently, initiatives such as Greenwave (2006) and Nature Watch (2009) invite school children and members of the general public respectively, to record phenology data from a range of common species of plant, insect and bird. In addition, the Irish butterfly and bumblebee monitoring schemes engage volunteers to record data on sightings of these species. The primary purpose of all of these networks is to collect data by which to monitor changes in wildlife development and diversity, and in the case of Greenwave to involve children in hands-on, inquiry-based science. Together these various networks help raise awareness of key environmental issues, such as climate change and loss of biodiversity, while at the same time promote development of scientific skills among the general population. In addition, they provide valuable scientific data by which to track environmental change. Here we examine the role of citizen science in monitoring biodiversity in Ireland and conclude that some of the data collected in these networks can be used to fulfil Ireland’s statutory obligations for nature conservation. In addition, a bee thought previously to be extinct has been rediscovered and a range expansion of a different bee has been confirmed. However, it also became apparent that some of the networks play more of an educational than a scientific role. Furthermore, we draw on experience from a range of citizen science projects to make recommendations on how best to establish new citizen science projects in Ireland and strengthen existing ones.     

The how and why of societal publications for citizen science projects and scientists

In the scientific community, the importance of communication to society is often underestimated. Scientists and scientific organisations often lack the skills to organise such communication effectively. The Dutch citizen science phenology network Nature’s Calendar has been successful in communicating to the general public via numerous newspaper articles, television appearances, presentations, websites and social media. We refer to these publications as societal publications. Due to active communication to mass media, we frequently reach millions of people. This communication helped us to involve thousands of volunteers in recording the timing of phenological events like the start of flowering, leaf unfolding and bird migration, but also several health-related events like hay fever symptoms and tick bites. In this paper, we analyse and present our experiences with the Nature’s Calendar project regarding societal publications. Based on this analysis, we explain the importance of societal publications for citizen science projects and scientists in general, and we show how scientists can increase the newsworthiness of scientific information and what factors and activities can increase the chances of media paying attention to this news. We show that societal publications help phenological networks by facilitating the recruitment, retention and instruction of observers. Furthermore, they stimulate the generation of new ideas and partners that lead to an increase in knowledge, awareness and behavioural change of the general public or specific stakeholders. They make projects, and scientists involved, better known to the public and increase their credibility and authority. Societal publications can catalyse the production of new publications, thereby enforcing the previous mentioned points.     

Citizen science and observer variability during American pika surveys

Within- and between-group observer variability can confound scientific discovery. If observer variability can be quantified and is addressed, data collected by participants with wide ranges of experience and training can yield more reliable inferences. The American pika (Ochotona princeps) is a mammalian sentinel of climate change that has received consideration for listing under the United States Endangered Species Act. As a result, numerous pika monitoring initiatives have been started throughout the mountains in western North America. Some initiatives employ research teams of biological science technicians (professionals), whereas many rely on networks of citizen scientists, or volunteers, for data collection. To date, few studies have quantified observer variability during pika surveys; none have explored the reliability of professional crews or volunteers. We conducted pika surveys in Glacier National Park, Montana, to quantify observer variability. We investigated observer variability 1) among a crew of professionals, 2) among volunteers, and 3) between professionals and volunteers. Professionals were more consistent at identifying pika signs and estimating potential home ranges and consistently found more pika signs than did the volunteers, with the exception of pika sightings. Estimates of pika occupancy were consistent at each site among volunteers conducting sitting surveys. We suggest that sitting surveys conducted by volunteers can reliably detect pika site occupancy. However, data on population dynamics of pikas (e.g., density) should be collected by professionals. Observer variability analyses of this nature should be common practice for wildlife-resource managers and scientists, especially with observers of varying levels of experience and motivation. © 2012 The Wildlife Society.     

Weekend bias in Citizen Science data reporting: implications for phenology studies

Studies of bird phenology can help elucidate the effects of climate change on wildlife species but observations over broad spatial scales are difficult without a network of observers. Recently, networks of citizen volunteers have begun to report first arrival dates for many migratory species. Potential benefits are substantial (e.g., understanding ecological processes at broad spatial and temporal scales) if known biases of citizen data reporting are identified and addressed. One potential source of bias in bird phenology studies is the tendency for more “first” migratory arrivals to be reported on weekends than on weekdays. We investigated weekend bias in data reporting for five common bird species in North America (Baltimore Oriole, Icterus galbula; Barn Swallow, Hirundo rustica; Chimney Swift, Chaetura pelagica; Purple Martin, Progne subis; and Ruby-throated Hummingbird, Archilochus colubris), and assessed whether this bias affected mean arrival dates reported using data from historical (1880–1969; N?=?25,555) and recent (1997–2010; N?=?63,149) Citizen Science databases. We found a greater percentage of first arrivals reported on weekends and small but significant differences in mean arrival dates (approximately 0.5 days) for four of five species. Comparing time periods, this weekend bias decreased from 33.7 % and five species in the historical time period to 32 % and three species in the recent, perhaps related to changes in human activity patterns. Our results indicate that weekend bias in citizen data reporting is decreasing over time in North America and including a ‘day of week’ term in models examining changes in phenology could help make conclusions more robust.     

Can Observation Skills of Citizen Scientists Be Estimated Using Species Accumulation Curves?

Volunteers are increasingly being recruited into citizen science projects to collect observations for scientific studies. An additional goal of these projects is to engage and educate these volunteers. Thus, there are few barriers to participation resulting in volunteer observers with varying ability to complete the project’s tasks. To improve the quality of a citizen science project’s outcomes it would be useful to account for inter-observer variation, and to assess the rarely tested presumption that participating in a citizen science projects results in volunteers becoming better observers. Here we present a method for indexing observer variability based on the data routinely submitted by observers participating in the citizen science project eBird, a broad-scale monitoring project in which observers collect and submit lists of the bird species observed while birding. Our method for indexing observer variability uses species accumulation curves, lines that describe how the total number of species reported increase with increasing time spent in collecting observations. We find that differences in species accumulation curves among observers equates to higher rates of species accumulation, particularly for harder-to-identify species, and reveals increased species accumulation rates with continued participation. We suggest that these properties of our analysis provide a measure of observer skill, and that the potential to derive post-hoc data-derived measurements of participant ability should be more widely explored by analysts of data from citizen science projects. We see the potential for inferential results from analyses of citizen science data to be improved by accounting for observer skill.     

Chimpanzee identification and social network construction through an online citizen science platform

Citizen science has grown rapidly in popularity in recent years due to its potential to educate and engage the public while providing a means to address a myriad of scientific questions. However, the rise in popularity of citizen science has also been accompanied by concerns about the quality of data emerging from citizen science research projects. We assessed data quality in the online citizen scientist platform Chimp&See, which hosts camera trap videos of chimpanzees (Pan troglodytes) and other species across Equatorial Africa. In particular, we compared detection and identification of individual chimpanzees by citizen scientists with that of experts with years of experience studying those chimpanzees. We found that citizen scientists typically detected the same number of individual chimpanzees as experts, but assigned far fewer identifications (IDs) to those individuals. Those IDs assigned, however, were nearly always in agreement with the IDs provided by experts. We applied the data sets of citizen scientists and experts by constructing social networks from each. We found that both social networks were relatively robust and shared a similar structure, as well as having positively correlated individual network positions. Our findings demonstrate that, although citizen scientists produced a smaller data set based on fewer confirmed IDs, the data strongly reflect expert classifications and can be used for meaningful assessments of group structure and dynamics. This approach expands opportunities for social research and conservation monitoring in great apes and many other individually identifiable species.     

Organization of marine phenology data in support of planning and conservation in ocean and coastal ecosystems

Among the many effects of climate change is its influence on the phenology of biota. In marine and coastal ecosystems, phenological shifts have been documented for multiple life forms; however, biological data related to marine species' phenology remain difficult to access and is under-used. We conducted an assessment of potential sources of biological data for marine species and their availability for use in phenological analyses and assessments. Our evaluations showed that data potentially related to understanding marine species' phenology are available through online resources of governmental, academic, and non-governmental organizations, but appropriate datasets are often difficult to discover and access, presenting opportunities for scientific infrastructure improvement. The developing Federal Marine Data Architecture when fully implemented will improve data flow and standardization for marine data within major federal repositories and provide an archival repository for collaborating academic and public data contributors. Another opportunity, largely untapped, is the engagement of citizen scientists in standardized collection of marine phenology data and contribution of these data to established data flows. Use of metadata with marine phenology related keywords could improve discovery and access to appropriate datasets. When data originators choose to self-publish, publication of research datasets with a digital object identifier, linked to metadata, will also improve subsequent discovery and access. Phenological changes in the marine environment will affect human economics, food systems, and recreation. No one source of data will be sufficient to understand these changes. The collective attention of marine data collectors is needed—whether with an agency, an educational institution, or a citizen scientist group—toward adopting the data management processes and standards needed to ensure availability of sufficient and useable marine data to understand marine phenology.     

The social fabric of citizen science—drivers for long-term engagement in the German butterfly monitoring scheme

Insect conservation needs sound information on species distribution trends. Developing this evidence relies—in practice—on long-term engagement of volunteers who observe and record species over large spatial and temporal scales. Many biodiversity monitoring schemes, including those for insects, are highly dependent on conservation-based citizen science programs with a long-term continuity. As these schemes are built entirely on good will, the nature of social relations and networks is pivotal to success. We assess the working mechanism of a monitoring scheme that is citizen-based as a case study. The German Butterfly Monitoring Scheme (hereafter TMD for “Tagfalter-Monitoring Deutschland”) operates, as many other citizen science monitoring schemes, through an overarching national network of regional subnetworks of volunteers and a central scientific coordination. Using a questionnaire survey paired with a visual social network assessment, we investigate how participants interact within these networks and assess their motivations to engage. We characterise the functionality of this social network based on mechanism of coordination and participation, flows of information and knowledge exchange among recorders, regional and central coordinators, academic scientists and institutions. By analyzing the interactions, we show how the social network facilitates and ensures various communication modes and thereby fosters long-term engagement, stability and growth of the scheme. We identify the central role of project coordination and the importance of social relations within citizen-based monitoring programs for engagement and personal satisfaction. Based on our empirical study, we derive a set of recommendations for establishing and maintaining successful volunteer networks in insect citizen-based monitoring programs.     

Variation in two phases of post‐winter development of a butterfly

The temporal aspects of life cycle characteristics, such as diapause development, are under strong selection in seasonal environments. Fine‐tuning of the life cycle may be particularly important to match the phenology of potential mates and resources as well as for optimizing abiotic conditions at eclosion. Here, we experimentally study the spring phenology of the orange tip butterfly, Anthocharis cardamines, by analysing post‐winter pupal development in three populations along a latitudinal cline in each of Sweden and the United Kingdom. These countries differ substantially in their seasonal temperature profile. By repeatedly recording pupal weights, we established that post‐winter development has two separate phases, with a more rapid weight loss in the second phase than in the first, likely corresponding to a ramping up of the rate of development. Variation in the duration of the first phase contributed more strongly than the second phase to the differences in phenology between the localities and sexes. We found that insects from Sweden had a faster overall rate of development than those from the United Kingdom, which is consistent with countergradient variation, as Sweden is colder during the spring than the United Kingdom. Similar trends were not observed at the within‐country scale, however. A cogradient pattern was found within Sweden, with populations from the north developing more slowly, and there was no clear latitudinal trend within the United Kingdom. In all localities, males developed faster than females. Our results point to the importance of variation in the progression of post‐winter development for spring phenology.     

A reversal of the shift towards earlier spring phenology in several Mediterranean reptiles and amphibians during the 1998–2013 warming slowdown

Herps, especially amphibians, are particularly susceptible to climate change, as temperature tightly controls many parameters of their biological cycle—above all, their phenology. The timing of herps’ activity or migration period—in particular the dates of their first appearance in spring and first breeding—and the shift to earlier dates in response to warming since the last quarter of the 20^th century has often been described up to now as a nearly monotonic trend towards earlier phenological events. In this study, we used citizen science data opportunistically collected on reptiles and amphibians in the northern Mediterranean basin over a period of 32 years to explore temporal variations in herp phenology. For 17 common species, we measured shifts in the date of the species’ first spring appearance—which may be the result of current changes in climate—and regressed the first appearance date against temperatures and precipitations. Our results confirmed the expected overall trend towards earlier first spring appearances from 1983 to 1997, and show that the first appearance date of both reptiles and amphibians fits well with the temperature in late winter. However, the trend towards earlier dates was stopped or even reversed in most species between 1998 and 2013. We interpret this reversal as a response to cooling related to the North Atlantic Oscillation (NAO) in the late winter and early spring. During the positive NAO episodes, for certain species only (mainly amphibians), the effect of a warm weather, which tends to advance the phenology, seems to be counterbalanced by the adverse effects of the relative dryness.     

Local snow melt and temperature—but not regional sea ice—explain variation in spring phenology in coastal Arctic tundra

The Arctic is undergoing dramatic environmental change with rapidly rising surface temperatures, accelerating sea ice decline and changing snow regimes, all of which influence tundra plant phenology. Despite these changes, no globally consistent direction of trends in spring phenology has been reported across the Arctic. While spring has advanced at some sites, spring has delayed or not changed at other sites, highlighting substantial unexplained variation. Here, we test the relative importance of local temperatures, local snow melt date and regional spring drop in sea ice extent as controls of variation in spring phenology across different sites and species. Trends in long‐term time series of spring leaf‐out and flowering (average span: 18 years) were highly variable for the 14 tundra species monitored at our four study sites on the Arctic coasts of Alaska, Canada and Greenland, ranging from advances of 10.06 days per decade to delays of 1.67 days per decade. Spring temperatures and the day of spring drop in sea ice extent advanced at all sites (average 1°C per decade and 21 days per decade, respectively), but only those sites with advances in snow melt (average 5 days advance per decade) also had advancing phenology. Variation in spring plant phenology was best explained by snow melt date (mean effect: 0.45 days advance in phenology per day advance snow melt) and, to a lesser extent, by mean spring temperature (mean effect: 2.39 days advance in phenology per °C). In contrast to previous studies examining sea ice and phenology at different spatial scales, regional spring drop in sea ice extent did not predict spring phenology for any species or site in our analysis. Our findings highlight that tundra vegetation responses to global change are more complex than a direct response to warming and emphasize the importance of snow melt as a local driver of tundra spring phenology.     

Challenging a 15‐year‐old claim: The North Atlantic Oscillation index as a predictor of spring migration phenology of birds

Many migrant bird species that breed in the Northern Hemisphere show advancement in spring arrival dates. The North Atlantic Oscillation (NAO) index is one of the climatic variables that have been most often investigated and shown to be correlated with these changes in spring arrival. Although the NAO is often claimed to be a good predictor or even to have a marked effect on interannual changes in spring migration phenology of Northern Hemisphere breeding birds, the results on relations between spring migration phenology and NAO show a large variety, ranging from no, over weak, to a strong association. Several factors, such as geographic location, migration phase, and the NAO index time window, have been suggested to partly explain these observed differences in association. A combination of a literature meta‐analysis, and a meta‐analysis and sliding time window analysis of a dataset of 23 short‐ and long‐distance migrants from the constant‐effort trapping garden at Helgoland, Germany, however, paints a completely different picture. We found a statistically significant overall effect size of the NAO on spring migration phenology (coefficient = ?0.14, SE = 0.054), but this on average only explains 0%–6% of the variance in spring migration phenology across all species. As such, the value and biological meaning of the NAO as a general predictor or explanatory variable for climate change effects on migration phenology of birds, seems highly questionable. We found little to no definite support for previously suggested factors, such as geographic location, migration phenology phase, or the NAO time window, to explain the heterogeneity in correlation differences. We, however, did find compelling evidence that the lack of accounting for trends in both time series has led to strongly inflated (spurious) correlations in many studies (coefficient = ?0.13, SE = 0.019).     

Epidemiology and control of virus diseases of vegetables

In order to assess the effect of an introduced gall wasp on the weed Acacia longifolia, it was necessary to study the vegetative growth and reproductive potential of uninfested trees. The growth of branches on uninfested trees was studied over one year. The results yielded a growth phenology which is notably different from the growth phenology of A. longifolia described by Milton (1980). Milton (1980) observed no flushing, but a gradual increase and decline in growth during spring and late summer, respectively. The present study showed distinct flushing, and a marked lack of growth during spring. Examination of the effect of reproduction on the vegetative growth of A. longifolia explains the disparity. A. longifolia reproduces during spring. Comparison of phyllode addition during spring with pod production for three successive years at one site, and for two years at another, shows that phyllode addition is low during years of high pod production, and vice versa. Between trees, phyllode addition is also inversely related to pod production within a reproductive season. Because the present growth phenology was done in a year of high pod production, growth during spring was negligible, in contrast with Milton's (1980) phenology which was done in a year of low pod production and high phyllode addition. Depending on the year in which the plant was studied, its reproductive potential and vegetative growth could have been under- or overestimated by as much as 62% and 90%, respectively. This study shows that the phenology of weeds with an annual cycle needs to be examined for at least two years in order not to under- or overestimate their reproductive or growth potential. This is especially important when assessing the efficacy of biological control agents.     

A unique role for citizen science in ecological restoration: a case study in streams

Citizen science has the potential to generate valuable biologic data for use in restoration monitoring, while also providing a unique opportunity for public participation in local restoration projects. In this article, we describe and evaluate a citizen science program designed to monitor the effect of stream restoration construction disturbance on the macroinvertebrate community. We present the results of a 7‐year stream restoration study conducted by citizen scientists utilizing a Before‐After‐Control‐Impact (BACI) design. Trait‐based macroinvertebrate data showed a strong response to restoration construction disturbance and return to pre‐restoration conditions within 2 years. The findings of this study suggest that citizen science can generate meaningful BACI‐oriented data about ecological restoration; however, until more research is conducted, citizen data should only be used to augment professional data intended to demonstrate restoration success.     

Effect of winter cold duration on spring phenology of the orange tip butterfly,Anthocharis cardamines

The effect of spring temperature on spring phenology is well understood in a wide range of taxa. However, studies on how winter conditions may affect spring phenology are underrepresented. Previous work on Anthocharis cardamines (orange tip butterfly) has shown population‐specific reaction norms of spring development in relation to spring temperature and a speeding up of post‐winter development with longer winter durations. In this experiment, we examined the effects of a greater and ecologically relevant range of winter durations on post‐winter pupal development of A. cardamines of two populations from the United Kingdom and two from Sweden. By analyzing pupal weight loss and metabolic rate, we were able to separate the overall post‐winter pupal development into diapause duration and post‐diapause development. We found differences in the duration of cold needed to break diapause among populations, with the southern UK population requiring a shorter duration than the other populations. We also found that the overall post‐winter pupal development time, following removal from winter cold, was negatively related to cold duration, through a combined effect of cold duration on diapause duration and on post‐diapause development time. Longer cold durations also lead to higher population synchrony in hatching. For current winter durations in the field, the A. cardamines population of southern UK could have a reduced development rate and lower synchrony in emergence because of short winters. With future climate change, this might become an issue also for other populations. Differences in winter conditions in the field among these four populations are large enough to have driven local adaptation of characteristics controlling spring phenology in response to winter duration. The observed phenology of these populations depends on a combination of winter and spring temperatures; thus, both must be taken into account for accurate predictions of phenology.     

Interactions between land use,habitat use,and population increase in greater snow geese: what are the consequences for natural wetlands?

The North American greater snow goose population has increased dramatically during the last 40 years. We evaluated whether refuge creation, changes in land use on the wintering and staging grounds, and climate warming have contributed to this expansion by affecting the distribution, habitat use, body condition, and migration phenology of birds. We also reviewed the effects of the increasing population on marshes on the wintering grounds, along the migratory routes and on the tundra in summer. Refuges established before 1970 may have contributed to the initial demographic increase. The most important change, however, was the switch from a diet entirely based on marsh plants in spring and winter (rhizomes of Scirpus/Spartina) to one dominated by crops (corn/young grass shoots) during the 1970s and 1980s. Geese now winter further north along the US Atlantic coast, leading to reduced hunting mortality. Their migratory routes now include portions of southwestern Québec where corn production has increased exponentially. Since the mid‐1960s, average temperatures have increased by 1–2.4°C throughout the geographic range of geese, which may have contributed to the northward shift in wintering range and an earlier migration in spring. Access to spilled corn in spring improved fat reserves upon departure for the Arctic and may have contributed to a high fecundity. The population increase has led to intense grazing of natural wetlands used by geese although these habitats are still largely undamaged. The foraging in fields allowed the population to exceed limits imposed by natural marshes in winter and spring, but also prevented permanent damage because of their overgrazing.     

Copepod life cycle adaptations and success in response to phytoplankton spring bloom phenology

In a seasonal environment, the timing of reproduction is usually scheduled to maximize the survival of offspring. Within deep water bodies, the phytoplankton spring bloom provides a short time window of high food quantity and quality for herbivores. The onset of algal bloom development, however, varies strongly from year to year due to interannual variability in meteorological conditions. Furthermore, the onset is predicted to change with global warming. Here, we use a long-term dataset to study (a) how a cyclopoid copepod, Cyclops vicinus , is dealing with the large variability in phytoplankton bloom phenology, and (b) if bloom phenology has an influence on offspring numbers. C. vicinus performed a two-phase dormancy, that is, the actual diapause of fourth copepodid stages at the lake bottom is followed by a delay in maturation, that is, a quiescence, within the fifth copepodid stage until the start of the spring bloom. This strategy seems to guarantee a high temporal match of the food requirements for successful offspring development, especially through the highly vulnerable naupliar stages, with the phytoplankton spring bloom. However, despite this match with food availability in all study years, offspring numbers, that is, offspring survival rates were higher in years with an early start of the phytoplankton bloom. In addition, the phenology of copepod development suggested that also within study years, early offspring seems to have lower mortality rates than late produced offspring. We suggest that this is due to a longer predator-free time period and/or reduced time stress for development. Hence, within the present climate variability, the copepod benefited from warmer spring temperatures resulting in an earlier phytoplankton spring bloom. Time will show if the copepod's strategy is flexible enough to cope with future warming.     

拔节期干旱和复水对春玉米物候的影响及其生理生态机制

物候不仅是气候变化的指示指标,也是作物模型的关键参数。现有研究主要关注物候变化与气候环境因子的关系,关于植物物候变化的生理生态机制研究很少。基于春玉米拔节期干旱与不同时间(抽雄期和吐丝期)复水的田间模拟试验分析表明:(1)不同时间复水均使灌浆期延长,乳熟期推迟(9d),表明物候对前期水分胁迫存在记忆。(2)干旱条件下叶片净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)和相对叶绿素含量(SPAD)均随物候进程呈先降后升再降趋势,且均在抽雄期达到极小值;不同时间复水均使P_n、T_r和G_s在吐丝期达到极大值,而SPAD则在灌浆期达到极大值;叶水势(LWP)随干旱进程整体呈下降趋势,不同时间复水均只是减缓了其下降速度,表明LWP可用于描述物候对前期水分胁迫的记忆。(3)通径分析和决策系数分析表明,P_n是最主要的物候影响因子,而影响LWP的土壤相对湿度(RSWC)则是物候的主要控制因子,物候的变化是由P_n的累积变化引起,表明存在P_n的物候触发阈值。研究结果为春玉米物候变化的准确预测提供了依据。     

Functional analysis of Normalized Difference Vegetation Index curves reveals overwinter mule deer survival is driven by both spring and autumn phenology

Large herbivore populations respond strongly to remotely sensed measures of primary productivity. Whereas most studies in seasonal environments have focused on the effects of spring plant phenology on juvenile survival, recent studies demonstrated that autumn nutrition also plays a crucial role. We tested for both direct and indirect (through body mass) effects of spring and autumn phenology on winter survival of 2315 mule deer fawns across a wide range of environmental conditions in Idaho, USA. We first performed a functional analysis that identified spring and autumn as the key periods for structuring the among-population and among-year variation of primary production (approximated from 1 km Advanced Very High Resolution Radiometer Normalized Difference Vegetation Index (NDVI)) along the growing season. A path analysis showed that early winter precipitation and direct and indirect effects of spring and autumn NDVI functional components accounted for 45% of observed variation in overwinter survival. The effect size of autumn phenology on body mass was about twice that of spring phenology, while direct effects of phenology on survival were similar between spring and autumn. We demonstrate that the effects of plant phenology vary across ecosystems, and that in semi-arid systems, autumn may be more important than spring for overwinter survival.