Patterns of Annual Seed Production by Northern Hemisphere Trees: A Global Perspective

We tested whether annual seed production (masting or mast fruiting) in Northern Hemisphere trees is an evolved strategy or a consequence of resource tracking by comparing masting patterns with those of annual rainfall and mean summer temperatures, two environmental variables likely to correlate with available resources. There were generally significant negative autocorrelations between the seed crop in year x and year [Formula: see text] (year [Formula: see text] in species of Quercus requiring 2 yr to mature acorns), as expected if resources are depleted in mast years in part by switching resources from growth to reproduction. Spatial autocorrelation in annual seed production generally declined with distance but was statistically significant over large geographic areas. Variability in annual seed production was relatively high and inversely correlated with latitude and generally not bimodally distributed. Patterns of spatial autocorrelation in annual rainfall and summer temperatures are generally similar to those exhibited by annual seed production, and relative variability in annual rainfall is also inversely correlated with latitude. However, these environmental variables exhibit distinctly different patterns of temporal autocorrelation, are much less variable, and are more normally distributed than annual seed production. Combined with the inverse relationship between growth and reproduction previously documented, these results support the hypothesis that variability in annual seed production is an evolved strategy and that annual seed production is more or less normally distributed rather than an all-or-none phenomenon.

Wave-like Patterns of Plant Phenology Determine Ungulate Movement Tactics

Animals exhibit a diversity of movement tactics [1]. Tracking resources that change across space and time is predicted to be a fundamental driver of animal movement [2]. For example, some migratory ungulates (i.e., hooved mammals) closely track the progression of highly nutritious plant green-up, a phenomenon called "green-wave surfing" [3-5]. Yet general principles describing how the dynamic nature of resources determine movement tactics are lacking [6]. We tested an emerging theory that predicts surfing and the existence of migratory behavior will be favored in environments where green-up is fleeting and moves sequentially across large landscapes (i.e., wave-like green-up) [7]. Landscapes exhibiting wave-like patterns of green-up facilitated surfing and explained the existence of migratory behavior across 61 populations of four ungulate species on two continents (n = 1,696 individuals). At the species level, foraging benefits were equivalent between tactics, suggesting that each movement tactic is fine-tuned to local patterns of plant phenology. For decades, ecologists have sought to understand how animals move to select habitat, commonly defining habitat as a set of static patches [8, 9]. Our findings indicate that animal movement tactics emerge as a function of the flux of resources across space and time, underscoring the need to redefine habitat to include its dynamic attributes. As global habitats continue to be modified by anthropogenic disturbance and climate change [10], our synthesis provides a generalizable framework to understand how animal movement will be influenced by altered patterns of resource phenology.

Biodiversity, Evolution and Ecological Specialization of Baculoviruses: A Treasure Trove for Future Applied Research

The Baculoviridae, a family of insect-specific large DNA viruses, is widely used in both biotechnology and biological control. Its applied value stems from millions of years of evolution influenced by interactions with their hosts and the environment. To understand how ecological interactions have shaped baculovirus diversification, we reconstructed a robust molecular phylogeny using 217 complete genomes and ~580 isolates for which at least one of four lepidopteran core genes was available. We then used a phylogenetic-concept-based approach (mPTP) to delimit 165 baculovirus species, including 38 species derived from new genetic data. Phylogenetic optimization of ecological characters revealed a general pattern of host conservatism punctuated by occasional shifts between closely related hosts and major shifts between lepidopteran superfamilies. Moreover, we found significant phylogenetic conservatism between baculoviruses and the type of plant growth (woody or herbaceous) associated with their insect hosts. In addition, we found that colonization of new ecological niches sometimes led to viral radiation. These macroevolutionary patterns show that besides selection during the infection process, baculovirus diversification was influenced by tritrophic interactions, explained by their persistence on plants and interactions in the midgut during horizontal transmission. This complete eco-evolutionary framework highlights the potential innovations that could still be harnessed from the diversity of baculoviruses.

Following the water? Landscape-scale temporal changes in bat spatial distribution in relation to Mediterranean summer drought

Understanding how the spatial distribution of ecological resources shapes species' diversity and abundance in human-modified landscapes is a central theme in conservation biology. However, studies often disregard that such patterns may vary over time, thereby potentially missing critical environmental constraints to species persistence. This may be particularly important in highly mobile species such as bats, which are able to track temporal variations in spatial resource distribution. Here we test the hypothesis that bats in Mediterranean landscapes are strongly affected by the progressive reduction in water availability during the seasonal summer drought. We analyzed the effects of landscape composition and structure on bat diversity and activity, during pregnancy, lactation, and postlactation periods, and identified the most influential variables within and across periods. Water bodies showed the strongest positive effect on bats, followed by riparian habitats and areas with steeper (>30%) slopes. However, while during pregnancy, there were only small landscape effects, these increased during lactation and postlactation, highlighting a progressively stronger association with water habitats during the summer drought. The spatial projection of habitat models showed that the landscape distribution of bat diversity and activity hotspots changed markedly over time. During pregnancy, the spatial pattern of hotspot distribution was weakly defined, while during lactation and particularly postlactation, there was a concentration of hotspots along permanently flowing watercourses. Our study highlights that permanently flowing watercourses are critical for bat conservation in Mediterranean landscapes, calling for measures to counteract their ongoing degradation due in particular to climate change, water abstraction and damming. More generally, our study underlines the importance of considering the temporal dimension in habitat selection studies, without which there is the risk of overlooking the importance of habitats that are key for species persistence only at certain times of the year.

Tracking snowmelt to jump the green wave: phenological drivers of migration in a northern ungulate

In northern climates, spring is a time of rapid environmental change: for migrating terrestrial animals, melting snow facilitates foraging and travel, and newly emergent vegetation provides a valuable nutritional resource. These changes result in selection on the timing of important life-history events such as migration and parturition occurring when high-quality resources are most abundant. We examined the timing of female caribou (Rangifer tarandus, n = 94) migration and parturition in five herds across 7 yr in Newfoundland, Canada, as a function of two measures of environmental change-snowmelt and vegetation green-up. We generated resource selection functions to test whether caribou selected for areas associated with snowmelt and green-up during migration and following calving. We found that caribou migrated approximately 1 wk prior to snowmelt, with the flush of emergent vegetation occurring during the weeks following parturition. The results indicate that caribou "jump" the green wave of emergent forage and do so by tracking the receding edge of melting snow, likely reducing movement and foraging costs related to snow cover. Our research further broadens the ecological scope of resource tracking in animals. We demonstrate that resource tracking extends beyond resources directly related to foraging to those related to movement. We also show that snowmelt provides an environmental cue that may provide a buffer against changing environmental conditions.

Characterizing population and individual migration patterns among native and restored bighorn sheep (Ovis canadensis)

Migration evolved as a behavior to enhance fitness through exploiting spatially and temporally variable resources and avoiding predation or other threats. Globally, landscape alterations have resulted in declines to migratory populations across taxa. Given the long time periods over which migrations evolved in native systems, it is unlikely that restored populations embody the same migratory complexity that existed before population reductions or regional extirpation.We used GPS location data collected from 209 female bighorn sheep (Ovis canadensis) to characterize population and individual migration patterns along elevation and geographic continuums for 18 populations of bighorn sheep with different management histories (i.e., restored, augmented, and native) across the western United States.Individuals with resident behaviors were present in all management histories. Elevational migrations were the most common population-level migratory behavior. There were notable differences in the degree of individual variation within a population across the three management histories. Relative to native populations, restored and augmented populations had less variation among individuals with respect to elevation and geographic migration distances. Differences in migratory behavior were most pronounced for geographic distances, where the majority of native populations had a range of variation that was 2-4 times greater than restored or augmented populations. Synthesis and applications. Migrations within native populations include a variety of patterns that translocation efforts have not been able to fully recreate within restored and augmented populations. Theoretical and empirical research has highlighted the benefits of migratory diversity in promoting resilience and population stability. Limited migratory diversity may serve as an additional factor limiting demographic performance and range expansion. We suggest preserving native systems with intact migratory portfolios and a more nuanced approach to restoration and augmentation in which source populations are identified based on a suite of criteria that includes matching migratory patterns of source populations with local landscape attributes.

Vaccine resource tracking systems

BACKGROUND

From 1999 to 2010, annual disbursements of development assistance for health for vaccinations increased from $0.5 billion to $2.0 billion (all financial values USD 2010). In its 2012 Global Vaccine Action Plan (GVAP), the World Health Assembly recommended establishing a comprehensive vaccination resource tracking system to better understand the source and recipients of these funds, and ultimately their impact on outcomes. This systematic review aims to respond to the GVAP recommendation in reviewing and assessing the state of the data and literature on vaccination resource tracking.

METHODS

We scrutinized all relevant vaccination resource tracking systems identified in the literature and by practitioners in the field. We examined schemes used elsewhere in the health sector and by other sectors. Informant interviews were also conducted to determine what data exists and how it might be utilized. With this information, we completed a qualitative assessment of existing approaches to vaccination resources tracking.

RESULTS

Tracking systems provide information about some vaccine-related activity in the majority of low- and middle-income countries. Data are generally available for the period of 2006-2010. Levels of granularity vary. Interviewees were concerned about the degree of rigor used to validate the data and the lack of verification. Data are often presented in tabular form, which may be unwieldy for non-technical audiences.

CONCLUSIONS

The schemes currently in place to track the resources available for vaccinations were fairly advanced relative to other mechanisms in the health sector. Nonetheless, the coverage, validity, and accessibility of vaccination resource tracking data could be ameliorated. Establishing improved feedback loops and verification mechanisms that connect country-level administrators and the international organizations that support reporting efforts would enhance data quality.

Oceanic giants dance to atmospheric rhythms: Ephemeral wind-driven resource tracking by blue whales

Trophic transfer of energy through marine food webs is strongly influenced by prey aggregation and its exploitation by predators. Rapid aggregation of some marine fish and crustacean forage species during wind-driven coastal upwelling has recently been discovered, motivating the hypothesis that predators of these forage species track the upwelling circulation in which prey aggregation occurs. We examine this hypothesis in the central California Current Ecosystem using integrative observations of upwelling dynamics, forage species' aggregation, and blue whale movement. Directional origins of blue whale calls repeatedly tracked upwelling plume circulation when wind-driven upwelling intensified and aggregation of forage species was heightened. Our findings illustrate a resource tracking strategy by which blue whales may maximize energy gain amid ephemeral foraging opportunities. These findings have implications for the ecology and conservation of diverse predators that are sustained by forage populations whose behaviour is responsive to episodic environmental dynamics.

Passive directed dispersal of plants by animals

Conceptual gaps and imprecise terms and definitions may obscure the breadth of plant-animal dispersal relationships involved in directed dispersal. The term 'directed' indicates predictable delivery to favourable microsites. However, directed dispersal was initially considered uncommon in diffuse mutualisms (i.e. those involving many species), partly because plants rarely influence post-removal propagule fate without specialized adaptations. This rationale implies that donor plants play an active role in directed dispersal by manipulating vector behaviour after propagule removal. However, even in most classic examples of directed dispersal, participating plants do not influence animal behaviour after propagule removal. Instead, such plants may take advantage of vector attraction to favourable plant microsites, indicating a need to expand upon current interpretations of directed dispersal. We contend that directed dispersal can emerge whenever propagules are disproportionately delivered to favourable microsites as a result of predictably skewed vector behaviour. Thus, we propose distinguishing active and passive forms of directed dispersal. In active directed dispersal, the donor plant achieves disproportionate arrival to favourable microsites by influencing vector behaviour after propagule removal. By contrast, passive directed dispersal occurs when the donor plant takes advantage of vector behaviour to arrive at favourable microsites. Whereas predictable post-removal vector behaviour is dictated by characteristics of the donor plant in active directed dispersal, characteristics of the destination dictate predictable post-removal vector behaviour in passive directed dispersal. Importantly, this passive form of directed dispersal may emerge in more plant-animal dispersal relationships because specialized adaptations in donor plants that influence post-removal vector behaviour are not required. We explore the occurrence and consequences of passive directed dispersal using the unifying generalized gravity model of dispersal. This model successfully describes vectored dispersal by incorporating the influence of the environment (i.e. attractiveness of microsites) on vector movement. When applying gravity models to dispersal, the three components of Newton's gravity equation (i.e. gravitational force, object mass, and distance between centres of mass) become analogous to propagules moving towards a location based on characteristics of the donor plant, the destination, and relocation processes. The generalized gravity model predicts passive directed dispersal in plant-animal dispersal relationships when (i) animal vectors are predictably attracted to specific destinations, (ii) animal vectors disproportionately disperse propagules to those destinations, and (iii) those destinations are also favourable microsites for the dispersed plants. Our literature search produced evidence for these three conditions broadly, and we identified 13 distinct scenarios where passive directed dispersal likely occurs because vector behaviour is predictably skewed towards favourable microsites. We discuss the wide applicability of passive directed dispersal to plant-animal mutualisms and provide new insights into the vulnerability of those mutualisms to global change.

Expenditure tracking and review of reproductive maternal, newborn and child health policy in Pakistan

Since 2001 substantial resources have been allocated to the reproductive, maternal, newborn and child health sector (RMNCH) in Pakistan. Many new programmes have been started and coverage of some existing programmes has been extended to un-served and rural areas. Despite these efforts the Millennium Development Goals (MDGs) 4 and 5 were not achieved (2000-15). Maternal Mortality Ratio was reduced to 170 per 100 000 live births (target 100) by 2013 at an annual reduction rate of 3.6% (1990-2013). Against the target of 46 per 1000 live births, the Under Five Mortality Rate was reduced to 81 per 1000 live births by 2015 at an annual reduction rate of 2.1% (1990-2015). We evaluated the comparative expenditures for the RMNCH sector and analysed impact of public expenditures on the use of the public facilities for the RMNCH services. Expenditure on RMNCH increased by 181% (2000-10), reaching PKR 628.79 billion (US$9.67 billion). The Share of the RMNCH expenditure in the total health expenditure increased from 16 to 21% (2005-10). The share of official development assistance for the RMNCH increased from 36 to 51% (2003-10). Equity was modestly achieved with a greater proportion of the poor using public facilities for the childhood diarrhoea (Concentration Index -0.06 in 2001-02 to - 0.11 in 2010-11) and reduction in the proportion of the rich using the public health facilities for institutional births (Concentration Index 0.30 in 2001-02 to 0.25 in 2010-11). Overall the RMNCH disease control programmes focused on vertical primary health approach and targeted the district health system in the un-served areas. Our findings confirm that diseconomies of scale, donor dependence and supply side perspective could only result in a modest progress towards achieving the MDGs. We call for urgent attention of the policy makers for the integration of the vertical and the routine primary health care and reliance on indigenous sustainable healthcare financing. We also recommend acknowledging economic perspective on health policy and health programmes.

EPIC Studies: Governments Finance, On Average, More Than 50 Percent Of Immunization Expenses, 2010-11

Governments in resource-poor settings have traditionally relied on external donor support for immunization. Under the Global Vaccine Action Plan, adopted in 2014, countries have committed to mobilizing additional domestic resources for immunization. Data gaps make it difficult to map how well countries have done in spending government resources on immunization to demonstrate greater ownership of programs. This article presents findings of an innovative approach for financial mapping of routine immunization applied in Benin, Ghana, Honduras, Moldova, Uganda, and Zambia. This approach uses modified System of Health Accounts coding to evaluate data collected from national and subnational levels and from donor agencies. We found that government sources accounted for 27-95 percent of routine immunization financing in 2011, with countries that have higher gross national product per capita better able to finance requirements. Most financing is channeled through government agencies and used at the primary care level. Sustainable immunization programs will depend upon whether governments have the fiscal space to allocate additional resources. Ongoing robust analysis of routine immunization should be instituted within the context of total health expenditure tracking.

Coursing the mottled mosaic: Generalist predators track pulses in availability of neonatal ungulates

The density and distribution of resources shape animal movement and behavior and have direct implications for population dynamics. Resource availability often is "pulsed" in space and time, and individuals should cue in on resource pulses when the energetic gain of doing so exceeds that of stable resources. Birth pulses of prey represent a profitable but ephemeral resource and should thereby result in shifting functional responses by predators. We evaluated movements and resource selection of coyotes (Canis latrans) across a gradient of reproductive stages ranging from late gestation to peak lactation of female mule deer (Odocoileus hemionus) in southwest Wyoming, USA, to test whether coyotes exhibited shifts in selection and movement behavior relative to the availability and vulnerability of neonatal mule deer. We expected coyotes to track pulses in availability of neonatal mule deer, and such behavior would be represented by shifts in resource selection and search behavior of coyotes that would be strongest during peak parturition of mule deer. Coyotes selected areas of high relative probability of use by female mule deer and did so most strongly during peak parturition. Furthermore, searching behavior of coyotes intensified during pulses of availability of deer neonates. Our findings support the notion that coyotes exploit pulses of neonatal deer, presumably as an attempt to capitalize on a vulnerable, energy-rich resource. Our work quantifies the behavioral mechanisms by which coyotes consume ungulate neonates and provides one of the first examples of a mammalian predator-prey system centered on a pulsed resource.

Tracking Global Fund HIV/AIDS resources used for sexual and reproductive health service integration: case study from Ethiopia

OBJECTIVE/BACKGROUND

The Global Fund to Fight AIDS, Tuberculosis & Malaria (GF) strives for high value for money, encouraging countries to integrate synergistic services and systems strengthening to maximize investments. The GF needs to show how, and how much, its grants support more than just HIV/AIDS, TB and malaria. Sexual and Reproductive Health (SRH) has been part of HIV/AIDS grants since 2007. Previous studies showed the GF PBF system does not allow resource tracking for SRH integration within HIV/AIDS grants. We present findings from a resource tracking case study using primary data collected at country level.

METHODS

Ethiopia was the study site. We reviewed data from four HIV/AIDS grants from January 2009-June 2011 and categorized SDAs and activities as directly, indirectly, or not related to SRH integration. Data included: GF PBF data; financial, performance, in-depth interview and facility observation data from Ethiopia.

RESULTS

All HIV/AIDS grants in Ethiopia support SRH integration activities (12-100%). Using activities within SDAs, expenditures directly supporting SRH integration increased from 25% to 66% for the largest HIV/AIDS grant, and from 21% to 34% for the smaller PMTCT-focused grant. Using SDAs to categorize expenditures underestimated direct investments in SRH integration; activity-based categorization is more accurate. The important finding is that primary data collection could not resolve the limitations in using GF GPR data for resource tracking. The remedy is to require existing activity-based budgets and expenditure reports as part of PBF reporting requirements, and make them available in the grant portfolio database. The GF should do this quickly, as it is a serious shortfall in the GF guiding principle of transparency.

CONCLUSIONS

Showing high value for money is important for maximizing impact and replenishments. The Global Fund should routinely track HIV/AIDs grant expenditures to disease control, service integration, and overall health systems strengthening. The current PBF system will not allow this. Real-time expenditure analysis could be achieved by integrating existing activity-based financial data into the routine PBF system. The GF's New Funding Model and the 2012-2016 strategy present good opportunities for over-hauling the PBF system to improve transparency and allow the GF to monitor and maximize value for money.

A test of the frost wave hypothesis in a temperate ungulate

Growing evidence supports the hypothesis that temperate herbivores surf the green wave of emerging plants during spring migration. Despite the importance of autumn migration, few studies have conceptualized resource tracking of temperate herbivores during this critical season. We adapted the frost wave hypothesis (FWH), which posits that animals pace their autumn migration to reduce exposure to snow but increase acquisition of forage. We tested the FWH in a population of mule deer in Wyoming, USA by tracking the autumn migrations of n = 163 mule deer that moved 15-288 km from summer to winter range. Migrating deer experienced similar amounts of snow but 1.4-2.1 times more residual forage than if they had naïve knowledge of when or how fast to migrate. Importantly, deer balanced exposure to snow and forage in a spatial manner. At the fine scale, deer avoided snow near their mountainous summer ranges and became more risk prone to snow near winter range. Aligning with their higher tolerance of snow and lingering behavior to acquire residual forage, deer increased stopover use by 1 ± 1 day (95% CI) day for every 10% of their migration completed. Our findings support the prediction that mule deer pace their autumn migration with the onset of snow and residual forage, but refine the FWH to include movement behavior en route that is spatially dynamic.

A gradual migratory divide determines not only the direction of migration but also migration strategy of a social migrant bird

Migratory divides separate populations of migratory animals, facilitating the evolution of intraspecific differences in migration strategies. Migration strategies are expected to be different for birds using different flyways and environments, but the knowledge regarding the impact of the flyway on individual migration strategies is scarce. By using satellite tracking and neckband resightings, we reveal the existence and structure of a gradual migratory divide between two European flyway populations of greylag geese Anser anser. Birds breeding at the far end of the Gulf of Bothnia in the Baltic Sea coast use the Western Flyway, those breeding in the Gulf of Finland the Central Flyway and those breeding between these extremes scatter to the two flyways. By using Gaussian process modelling, we show that migration strategies differed between the flyways. The birds using the Western Flyway migrated earlier in autumn, performed longer annual migration and made a clear stopover during migration, whereas the birds using the Central Flyway flew directly to their wintering sites. The gradual migratory divide that also divides migration strategies provides insights into migratory divides on birds with learned migration. Distinct migration strategies in different flyways provide exciting possibilities to further study the factors driving migration strategies.

Migratory herbivorous waterfowl track multiple resource waves during spring migration

East Asian herbivorous waterfowl intensively use farmland in spring, next to their natural habitat. Accordingly, they might have expanded their migration strategy from merely tracking the green wave of newly emerging vegetation to also incorporating the availability of post-harvest agricultural seeds (here dubbed the seed wave). However, if and how waterfowl use multiple food resources to time their seasonal migration is still unknown. We test this migration strategy using 167 spring migration tracks of five East Asian herbivorous waterfowl species and mixed-effect resource selection function models. We found that all study species arrived at their core stopover sites in the Northeast China Plain after agricultural seeds became available, extended their stay after spring vegetation emerged and arrived at their breeding sites around the emergence of vegetation. At the core stopover sites, all study species used snowmelt as a cue to track seed availability, although smaller-bodied species tended to arrive later. At the breeding sites, swans tracked the onset of vegetation emergence and geese tracked the mid- or end phases of snowmelt. Our findings suggest that waterfowl track multiple resource waves to fine-tune their migration, highlighting new opportunities for conservation.

Origin stories: how does learned migratory behaviour arise in populations?

Although decades of research have deepened our understanding of the proximate triggers and ultimate drivers of migrations for a range of taxa, how populations establish migrations remains a mystery. However, recent studies have begun to illuminate the interplay between genetically inherited and learned migrations, opening the door to the evaluation of how migration may be learned, established, and maintained. Nevertheless, for migratory species where the role of learning is evident, we lack a comprehensive framework for understanding how populations learn specific routes and refine migratory movements over time (i.e., their origins). This review draws on advances in behavioural and movement ecology to offer a comprehensive framework for how populations could transition from resident to migratory by connecting cognitive research on fine-scale perceptual cues and movement decisions with literature on learning and cultural transmission, to the emergent pattern of migration. We synthesize the multiple cognitive mechanisms and processes that allow a population to respond to seasonal resource limitation, then encode spatial and environmental information about resource availability in memory and engage in social learning to navigate their landscapes and track resources better. A rise in global reintroduction efforts, along with human-induced rapid shifts in environmental cues and changing landscapes make evaluating the origins of this threatened behaviour more urgent than ever.

Riding the wetland wave: Can ducks locate macroinvertebrate resources across the breeding season?

Food availability varies considerably over space and time in wetland systems, and consumers must be able to track those changes during energetically-demanding points in the life cycle like breeding. Resource tracking has been studied frequently among herbivores, but receives less attention among consumers of macroinvertebrates. We evaluated the change in resource availability across habitat types and time and the simultaneous density of waterfowl consumers throughout their breeding season in a high-elevation, flood-irrigated system. We also assessed whether the macroinvertebrate resource density better predicted waterfowl density across habitats, compared to consistency (i.e., temporal evenness) of the invertebrate resource or taxonomic richness. Resource density varied marginally across wetland types but was highest in basin wetlands (i.e., ponds) and peaked early in the breeding season, whereas it remained relatively low and stable in other wetland habitats. Breeding duck density was positively related to resource density, more so than temporal resource stability, for all species. Resource density was negatively related to duckling density, however. These results have the potential to not only elucidate mechanisms of habitat selection among breeding ducks in flood-irrigated landscapes but also suggest there is not a consequential trade-off to selecting wetland sites based on energy density versus temporal resource stability and that good-quality wetland sites provide both.

Chasing and surfing seasonal waves: Avian migration through the US tracks land surface phenology in fall, but not spring

Climate change is altering the timing of seasonal events for many taxa. There is limited understanding of how northward/southward songbird migration follows or is limited by the latitudinal progression of seasonal transitions. Consistent environmental conditions that migrating birds encounter across latitudes likely represent or correlate with important resources or limiting factors for migration. We tested whether migratory passage-observed via radar-consistently tracked land surface variables and phenophases across latitudes in the US Central Flyway in both spring and fall. The daily temperatures, precipitation and vegetation greenness occurring on 10%, 50% and 90% cumulative passage dates changed substantially with latitude, indicating that most migrants experienced rapidly changing conditions as they headed north or south. Temperature did not limit the progression of migration in either season. Peak spring migration in the southern US occurred nearly 40 days after the spring green wave, the northward progression of vegetation growth, but nearly caught up to green-up at 48° N. Spring migration phenology may have evolved to prioritize earlier arrival for breeding. Across all latitudes, peak fall migration coincided with the same land surface phenophase, an interval of 26 days prior to dormancy onset. Migrants may rely on phenological events in vegetation during fall stopovers. Considering that (a) migratory passage tracked fall land surface phenology across latitudes at a continental scale, (b) previous studies at local scales have demonstrated the importance of fruit during fall migratory stopover and (c) fruiting phenology in North America is occurring later over time while fall migration is advancing, the potential for mismatch between fall fruiting and bird migration phenology urgently needs further investigation.