Summer Survival Research Articles

Predator identity and forage availability affect predation risk of juvenile black-tailed deer

Understanding how top–down and bottom–up effects influence population dynamics of ungulates is essential for effective management and conservation, and there is an emerging consensus that forage productivity and quality interact with predation to influence survival. From 2009 to 2013, we captured and monitored 135 neonatal black-tailed deer Odocoileus hemionus columbianus in coastal California to study possible interactions between forage and predation on survival. We estimated seasonal and annual survival rates, assessed the cause of all mortalities (n = 93), measured available forage and diet quality, estimated relative abundances of predators on summer range each year, and used remote sensing to quantify habitat types on winter range. We evaluated the relationship between fawn survival and environmental covariates with cumulative incidence and proportional hazards functions. Summer survival rates averaged 0.40 (SE = 0.05) across all years and the mean annual survival rate was 0.26 (SE = 0.04). We found that most juvenile mortality resulted from predation during summer, and spatial differences in summer survival persisted until recruitment. Variation in mortality risk from all causes was related to the birth weight of juveniles and available oak forage but not predator abundance. The risk of black bear predation, the single largest cause of mortality, was unrelated to birth weight and showed an interaction between bear abundance and the amount of oak forage. Additionally, the good body condition of adult females in spring and a lack of relationship between mortality risk and variation in deer density did not provide evidence for purely bottom–up limitation. Rather our results provide evidence that both bottom–up and top–down effects were influencing fawn survival in this declining population, and that predator identity and the timing of mortality affected the impact of predation.

Summer survival and activity patterns of estuary feeding anadromous Salmo trutta

AbstractThere is generally a very poor understanding of how anadromous brown trout, Salmo trutta, use marine ecosystems. In this study, we use acoustic telemetry techniques to test four alternative hypotheses for estuarine coastal habitat use by this species on a population in the Clyde, west‐central Scotland. Anadromous brown trout in their second (or more) summer feeding in the marine environment did not show patterns of estuarine use predicted from studies on other populations of this species. They did not (a) use the inner Clyde Estuary as a staging post for onward migration to open coastal waters, nor did they (b) pass through the estuary rapidly nor did they (c) make multiple incursions into freshwater. In contrast, fish utilised a very geographically constrained area of the inner estuary (<8 km in length), within which fish were highly mobile, exhibiting more activity during a flooding tide and exhibited high survivorship compared with reports from other studies. The reasons why estuarine use by anadromous brown trout in the Clyde may differ from that reported elsewhere is discussed.

Causes and short-term consequences of variation in milk composition in wild sheep.

Ecologists seek to understand the fitness consequences of variation in physiological markers, under the hypothesis that physiological state is linked to variability in individual condition and life history. Thus, ecologists are often interested in estimating correlations between entire suites of correlated traits, or biomarkers, but sample size limitations often do not allow us to do this properly when large numbers of traits or biomarkers are considered. Latent variables are a powerful tool to overcome this complexity. Recent statistical advances have enabled a new class of multivariate models-multivariate hierarchical modelling (MHM) with latent variables-which allow to statistically estimate unstructured covariances/correlations among traits with reduced constraints on the number of degrees of freedom to account in the model. It is thus possible to highlight correlated structures in potentially very large numbers of traits. Here, we apply MHM to evaluate the relative importance of individual differences and environmental effects on milk composition and identify the drivers of this variation. We ask whether variation in bighorn sheep milk affects offspring fitness. We evaluate whether mothers show repeatable individual differences in the concentrations of 11 markers of milk composition, and we investigate the relative importance of annual variability, maternal identity and morphological traits in structuring milk composition. We then use variance estimates to investigate how a subset of repeatable milk markers influence lamb summer survival. Repeatability of milk markers ranged from 0.05 to 0.64 after accounting for year-to-year variations. Milk composition was weakly but significantly associated with maternal mass in June and September, summer mass gain and winter mass loss. Variation explained by year-to-year fluctuations ranged from 0.07 to 0.91 suggesting a strong influence of environmental variability on milk composition. Milk composition did not affect lamb survival to weaning. Using joint models in ecological, physiological or behavioural contexts has the major advantage of decomposing a (co)variance/correlation matrix while being estimated with fewer parameters than in a "traditional" mixed-effects model. The joint models presented here complement a growing list of tools to analyse correlations at different hierarchical levels separately and may thus represent a partial solution to the conundrum of physiological complexity.

Environmental factors may influence interseeded annual ryegrass and red clover establishment and growth more than soil residual herbicide applications

AbstractIntegrating multiple weed management (cultural, physical, chemical) strategies is often recommended to combat herbicide resistance. With the increased use of interseeded cover crops, the effects of PRE herbicides on their establishment and growth require study. An investigation was conducted in Lexington, KY, in 2016 through 2018 to assess the extent to which commonly used PRE corn herbicide combinations influenced interseeded red clover and annual ryegrass establishment and growth. Annual ryegrass density was reduced 29% at 3 wk after interseeding by the combination of residual dimethenamid-P and atrazine; however, biomass the following spring was not affected by herbicide combinations. Neither density of interseeded red clover at 2 to 3 wk after interseeding nor biomass prior to termination the following spring were influenced by herbicide combinations. However, red clover density was affected by herbicide treatment 5 wk after interseeding in 2016. These results could have been influenced by low summer survival, particularly in 2016. The environmental factors may have influenced the survival of the interseeded cover crops more than the PRE herbicides. This study suggests that multiple PRE herbicides can be used with minimal risk to interseeded red clover or annual ryegrass. However, the influence of the environment on establishment and survival of interseeded cover crops following the use of PRE herbicides requires further study.

Summertime resource selection and reproductive effects on survival of Ruffed Grouse

ABSTRACT Theory suggests that animals should select resources on the basis of perceived fitness benefits, and avoid other available resources that may result in fitness costs. However, resource selection is both a scale- and a life-stage-specific process, in which the importance of different resources may vary among spatial scales of selection and phases of species' life cycles. We investigated multilevel resource selection and summer survival of Ruffed Grouse (Bonasa umbellus) in Maine, USA, to understand life-stage-specific resource selection and the cost of brood rearing. At the landscape level, male Ruffed Grouse selected areas with greater densities of woody stems taller than breast height, while females avoided these areas and selected areas with greater ground coverage by Rubus. Males further selected areas with greater stem densities at the local level, while females again avoided areas with greater stem densities and selected locally available areas with greater ground coverage by Rubus. Weekly s...

Survival and Predators of Pacific Marten in a Salvage-Logged Pine Forest, South-Central Oregon

Estimating marten (Martes spp.) survival rates in managed forests is important for comparisons with vital rates in unmanaged forests, and data across populations in different forest types are needed in meta-analyses. We estimated survival rates of a Pacific Marten (Martes caurina) population from 1993 to 1998. This population experienced no fur trapping and occurred in an atypical habitat of sparse tree-canopy cover, small tree diameters, and many natural openings and logging clearcuts. In the beetle-damaged, salvage-logged Lodgepole Pine (Pinus contorta) forest, downed wood and snags were removed and slash piles were accumulated to mitigate logging effects. The average annual probability of adult (≥1 y) survival was 0.684, sx = 0.104 (n = 53). The overall adult survival did not differ between years or between the sexes across years. Average annual survival of young (<1 y) was 0.753, sx = 0.118 (n = 26). Seasonal survival of adults (0.945, sx = 0.027) and young (0.974, sx = 0.026) was highest in winter (December through February), and lowest in summer (June through August; adults = 0.853, sx = 0.035; young = 0.902, sx = 0.046). Adult winter survival was significantly greater than summer survival; and for adult females, winter survival was greater than in the other seasons (other seasons range = 0.862 to 0.903) and greater than male winter survival (0.918, sx = 0.039), because there were no known female losses during the period (survival = 1.0). Based on evidence at field recovery sites and laboratory necropsies, predators were associated with 74% of all recovered marten carcasses, including Coyote (Canis latrans), Bobcat (Lynx rufus), American Badger (Taxidea taxus), and raptors of unknown species. Slash piles were used by marten, but the mitigation experiment was discontinued after logging. We suggest that slash piles may have helped sustain the local population of marten in the short term.

Assessment of northern bobwhite survival and fitness in the West Gulf Coastal Plain ecoregion.

In the West Gulf Coastal Plains (WGCP) northern bobwhite (Colinus virginianus) are declining faster than range-wide averages and such declines have been linked to the consequences of land management. Management for the endangered red-cockaded woodpecker (Picoides borealis) has benefitted northern bobwhite by restoring mature pine-grassland ecosystems in some areas of the region. However, at Felsenthal National Wildlife Refuge, Crossett, Arkansas, USA, the bobwhite population was not increasing despite the availability of seemingly suitable habitat from management for the endangered species. To understand factors that may be affecting bobwhite survival on Felsenthal National Wildlife Refuge we conducted a telemetry study and assessed summer survival, brood survival, and nest success from 1 April– 11 August in 2013 and 1 April– 15 August in 2014. We also calculated home-range sizes and measured microhabitat characteristics around nests. Summer survival rates were 71% (SE = 0.17) and 47% (SE = 0.14); while nest success was 47% (SE = 0.02) and 100% for 2013 and 2014, respectively. Between years, both 95% and 50% kernel home-ranges were not different (pooled, 63.92±6.07 ha and 14.94±1.75 ha); however minimum convex polygon home-range sizes were (113.8 ± 20.1 ha in 2013; and 393.1 ± 49.0 ha in 2014, P < 0.001). Only numerical differences in microhabitat vegetation characteristics of nest sites and non- nest sites were observed. We suggest management for red-cockaded woodpeckers supports bobwhite populations but only as a buffer against more severe declines. Since bobwhites are declining range-wide, we believe areas federally managed for red-cockaded woodpeckers will become increasingly more important for sustaining regional bobwhite population levels.

Reproductive state leads to intraspecific habitat partitioning and survival differences in greater sage-grouse: implications for conservation

Context Inter- and intraspecific habitat partitioning is widespread across taxa, yet limited information is available on differences in intraspecific habitat selection by same-sex individuals among differing reproductive states. Understanding habitat selection by conspecifics of different reproductive states may help optimise conservation efforts, particularly for gallinaceous bird species such as greater sage-grouse (Centrocercus urophasianus), which are long-lived but have only moderate reproductive rates. Aims We predicted that habitat use differed between grouse under different reproductive states and that reproductive investment decreased survival of adults in summer. Methods We compared habitat characteristics used by brood-rearing and broodless female sage-grouse and evaluated the influence of reproductive investment and habitat use on survival of adult females. Key results We found that brood-rearing and broodless female sage-grouse partitioned habitat at micro- and macrohabitat scales. Broodless females were more likely to survive the summer. Conclusions Our findings suggest reproductive state variability in habitat selection by female sage-grouse. Broodless females were roosting and foraging in concealed habitats with intermediate visual obstruction and annual vegetation productivity, but less food forb availability compared with early and late brood-rearing females. In contrast, brood-rearing females likely selected more herbaceous understoreys to predictably maximise foraging opportunities and promote growth of their chicks, which appeared to mitigate the influence of reproductive costs on summer survival, particularly during the late brood-rearing period. Implications Survival of adult females is critical for population persistence of sage-grouse and other long-lived Galliformes, yet conservation efforts generally focus on habitats used during nesting and brood-rearing. Our results suggest that habitat partitioning is a potential risk-aversion strategy where individuals across different reproductive states likely select habitats to maximise their survival. Conservation efforts should focus on conserving habitats used by both brood-rearing and broodless sage-grouse to ensure population persistence.

Survival of chicks and adults explains variation in population growth in a recovering red grouse Lagopus lagopus scotica population

Understanding demographic mechanisms is key to managing animal populations, both in conservation and game management. We examine which life‐stages contributed most to population growth in a recovering red grouse Lagopus lagopus scotica population following restoration of management aimed at resuming economically viable harvesting. Demographic parameters derived from biannual grouse counts and from radio‐tagged individuals were analysed using ‘standard demographic accounting’. When parameter estimates were based on counts, a combination of adult summer and winter survival appeared to contribute most to population change. When based on radio‐tagged birds, deemed more reliable because of independence between parameters and years, adult summer survival and chick survival contributed most to population change. The contributions of clutch size, nesting success (i.e. the proportion of nests with ≥1 egg hatching) and hatching success (proportion of eggs hatching in successful nests) were negligible. Overall, the survival rate of adults and chicks contributed most to annual population change and reduced the rate of population recovery. Analysis of grouse carcasses found that 82% were associated with signs of predation or scavenging by raptors. Rates of juvenile production exceeded those of adult mortality, allowing modest population growth, but insufficient to resume economically viable harvesting.

Modeling the Environmental Suitability for Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus (Diptera: Culicidae) in the Contiguous United States.

The mosquitoes Aedes (Stegomyia) aegypti (L.)(Diptera:Culicidae) and Ae. (Stegomyia) albopictus (Skuse) (Diptera:Culicidae) transmit dengue, chikungunya, and Zika viruses and represent a growing public health threat in parts of the United States where they are established. To complement existing mosquito presence records based on discontinuous, non-systematic surveillance efforts, we developed county-scale environmental suitability maps for both species using maximum entropy modeling to fit climatic variables to county presence records from 1960-2016 in the contiguous United States. The predictive models for Ae. aegypti and Ae. albopictus had an overall accuracy of 0.84 and 0.85, respectively. Cumulative growing degree days (GDDs) during the winter months, an indicator of overall warmth, was the most important predictive variable for both species and was positively associated with environmental suitability. The number (percentage) of counties classified as environmentally suitable, based on models with 90 or 99% sensitivity, ranged from 1,443 (46%) to 2,209 (71%) for Ae. aegypti and from 1,726 (55%) to 2,329 (75%) for Ae. albopictus. Increasing model sensitivity results in more counties classified as suitable, at least for summer survival, from which there are no mosquito records. We anticipate that Ae. aegypti and Ae. albopictus will be found more commonly in counties classified as suitable based on the lower 90% sensitivity threshold compared with the higher 99% threshold. Counties predicted suitable with 90% sensitivity should therefore be a top priority for expanded mosquito surveillance efforts while still keeping in mind that Ae. aegypti and Ae. albopictus may be introduced, via accidental transport of eggs or immatures, and potentially proliferate during the warmest part of the year anywhere within the geographic areas delineated by the 99% sensitivity model.

Mechanisms of population limitation in the southern red-backed vole in conifer forests of western North America: insights from a long-term study

Our goals were to characterize multiannual population changes of the southern red-backed vole (Myodes gapperi) to determine potential cycling behavior, and to specify the possible causes of these changes. We analyzed a detailed, 21-year record of changes in abundance of M. gapperi in late successional coniferous forest in southern British Columbia, Canada, from 1995 to 2015. We evaluated 3 hypotheses (H), namely that population changes are related to: (H1) changes in food supply from cone crops of coniferous trees; (H2) changes in forest habitat associated with beetle-killed lodgepole pine (Pinus contorta) trees; and (H3) territorial reorganization leading to breeding season declines in abundance. There were 3 cyclic population fluctuations (6- to 7-year periodicity) where red-backed voles reached mean fall numbers of 19–25, 15–16, and 26–27 per ha, respectively; in contrast, only 2–5 voles per ha occurred during population lows. Breeding season declines in abundance occurred in 17 of 21 years, with particularly precipitous drops ranging from 49% to 69% loss of voles. M. gapperi had more successful pregnancies, juvenile recruits, and adult recruits in the high than in the low population years. Mean index of early juvenile survival was 22% higher in low than high population years. Mean summer survival (58%) was consistently lower than that in winter (83%). Population increases were positively related to cone crops of 3 coniferous tree species. Thus, H1 was partially supported in 3 of 4 seedfall events. Positive changes in forest habitat, resulting from seed rain as a food supply and fallen debris from beetle-killed pine trees as cover, may have supported high numbers of voles in 2011–2012 (H2). A spring reorganization event limited the number of breeding animals by density-dependent inhibition of maturation and survival of juvenile voles, and led to breeding season declines (H3). Rigorous field experiments are needed to test these hypotheses and their interactions as mechanisms driving population change.

Reduced reproductive performance associated with warmer ambient temperatures during incubation in a winter‐breeding, food‐storing passerine

Timing of reproduction can influence individual fitness whereby early breeders tend to have higher reproductive success than late breeders. However, the fitness consequences of timing of breeding may also be influenced by environmental conditions after the commencement of breeding. We tested whether ambient temperatures during the incubation and early nestling periods modulated the effect of laying date on brood size and dominant juvenile survival in gray jays (Perisoreus canadensis), a sedentary boreal species whose late winter nesting depends, in part, on caches of perishable food. Previous evidence has suggested that warmer temperatures degrade the quality of these food hoards, and we asked whether warmer ambient temperatures during the incubation and early nestling periods would be associated with smaller brood sizes and lower summer survival of dominant juveniles. We used 38 years of data from a range‐edge population of gray jays in Algonquin Provincial Park, Ontario, where the population has declined over 50% since the study began. Consistent with the “hoard‐rot” hypothesis, we found that cold temperatures during incubation were associated with larger brood sizes in later breeding attempts, but temperatures had little effect on brood size for females breeding early in the season. This is the first evidence that laying date and temperature during incubation interactively influence brood size in any bird species. We did not find evidence that ambient temperatures during the incubation period or early part of the nestling period influenced summer survival of dominant juveniles. Our findings provide evidence that warming temperatures are associated with some aspects of reduced reproductive performance in a species that is reliant on cold temperatures to store perishable food caches, some of which are later consumed during the reproductive period.

Many places called home: the adaptive value of seasonal adjustments in range fidelity.

The vast majority of animal species display range fidelity, a space-use behaviour enhancing familiarity with local habitat features. While the fitness benefits of this behaviour have been demonstrated in a variety of taxa, some species or populations rather display infidelity, displacing their home range over time. Others, such as many ungulate species, show seasonal adjustments in their range fidelity to accommodate changes in the dominance of limiting factors or in the distribution of resources. Few empirical studies have explored the adaptive value of seasonal adjustments in range fidelity. Using boreal populations of woodland caribou (Rangifer tarandus caribou) as a biological model, we evaluated how range fidelity impacted individual performance during two seasons where juvenile and adult survival are limited by different predation pressures. Between 2004 and 2013, we monitored the survival, reproductive success, habitat selection and range fidelity of female caribou in the boreal forest of eastern Canada. Using resource selection functions, we assessed how seasonal range fidelity was linked to two fitness correlates: calf survival in summer and adult female survival in winter. Females displayed season-specific space use tactics: they selected previously used areas during calving and summer, but tended to shift their winter range from 1year to the next. During calving and summer, range fidelity yielded relatively high fitness benefits, as females that did not lose their calf displayed stronger fidelity than females that did. In winter, however, adult survival was negatively linked to range fidelity, as females that survived selected areas further away from their seasonal range of the previous year than females that died. We provide one of the first evidences that making seasonal adjustments in range fidelity can be an adaptive behaviour influencing the spatial distribution of a threatened species. Assessing the seasonal nature of range fidelity tactics may improve our predictions of space use and associated fitness implications for species displaying this behaviour.

Indiana bats roost in ephemeral, fire-dependent pine snags in the southern Appalachian Mountains, USA

The Indiana bat (Myotis sodalis), a species that is federally endangered in the U.S., is being impacted by white-nose syndrome and habitat loss across much of its range. A better understanding of summer roost ecology of the species will enable us to develop management strategies that promote summer survival for breeding adult females and their pups. We conducted a 5year investigation of Indiana bat roost habitat selection and roosting behavior in a large (>250,000ha) forested area of the southern Appalachian Mountains and compared our results to populations in different landscapes across the species’ range. From May to August 2008–2012, we attached radio transmitters to 50 adult females, 3 juveniles, and 7 adult males captured at sites on the Cherokee and Nantahala national forests and Great Smoky Mountains National Park. We radiotracked bats to 95 roosts and measured characteristics of trees, 0.1ha plots, and landscape attributes for 69 of these roosts and associated random trees. We used an AIC approach to compare 14 candidate conditional logistic regression models. The only plausible model, which carried 95% of total model weights, had 3 important terms. Indiana bats showed strong selection for yellow pine (Pinus subgenus Diploxylon) snags that were significantly taller than random trees and in areas with a greater number of snags within 0.1ha. During this study, tree and stand structure were more important for roost selection than larger scale factors and Indiana bats responded to a pulsed and highly ephemeral resource, dead yellow pines, which were a significant component of the large forest tracts. Roosting behavior differed from what has been observed for Indiana bats in other parts of the eastern U.S.; maternity colonies tended to be smaller (<25 bats, but as large as 75 bats prior to pups being volant) and bats were more nomadic, using each roost tree for only 2–3days on average and rarely for more than one year. The differences we observed in roosting behavior in the southern Appalachians suggest it would be wise to consider the broader landscape context when evaluating the roosting ecology of Indiana bats, as local forest types and disturbance events will affect stand structure and roost tree availability. Stand- and landscape-scale management practices that create or preserve large pine snags, such as prescribed fire, coupled with natural or manmade pulsed disturbances, should aid in the management and recovery of the Indiana bat in this region.

Survival analysis and computer simulations of lethal and contraceptive management strategies for urban deer

I monitored survival of 34 female white-tailed deer (Odocoileus virginianus) in Bloomington, Minnesota, from October 1996 to December 1999. Twenty deer died: nineteen were killed by vehicles, and one was killed in a deer-removal program conducted by an adjacent suburb. Summer survival was high and varied little over the 3 years of study (range = 0.93 to 0.95). Fall survival ranged from 0.84 to 1.00, and winter survival was generally high during the 3 years of study, except during a severe winter (range = 0.72 to 0.95). I calculated population growth rates (λ) from Leslie matrix projections, using these survival estimates and productivity data collected from road-killed female deer in the Twin Cities (Minneapolis-St. Paul, Minnesota, USA) metropolitan area. When winter survival was high (0.94), my model simulations indicated the Bloomington deer population increased by 21% when no deer management program was in place. When a low winter survival rate (0.72) was modeled, the population decreased by 7%, even when no deer management program was implemented. I modeled what impact contraception may have on population growth and concluded that treating >50% of adult female deer was necessary to stabilize population growth, and treating all females was necessary to decrease population growth under high winter survival conditions. I concluded that removal programs are more effective than immunocontraception programs because survival contributes more to population growth rates in deer populations than fecundity. I recommend removing 20% and 40% of adult female deer in the population to cause the population to stabilize or to reduce deer numbers, respectively. I recommend managers collect deer-vehicle collision data because these data potentially represent the most accurate and easily-obtainable life history component of an urban deer herd.

Indirect effects of prey fluctuation on survival of juvenile arctic fox (Vulpes lagopus): a matter of maternal experience and litter attendance

Reproductive experience affects juvenile survival in a wide range of species with possible links to differences in foraging capacity and predation. Using supplementary feeding, we aimed to limit direct effect of prey abundance to investigate indirect effects of small-rodent availability and maternal experience on juvenile summer survival rates in an endangered population of arctic fox (Vulpes lagopus (L., 1758)). We used data spanning 7 years, included a complete small-rodent cycle, comprising 49 litters and 394 cubs. The effect of small-rodent abundance on juvenile survival depended on maternal breeding experience. Cubs born by first-time-breeding females had lower survival rate when small-rodent abundance was low compared with juveniles born to experienced mothers who remained unaffected. It was unlikely due to starvation, as physical condition was unrelated to survival. Instead, we favour the explanation that intraguild predation was an important cause of mortality. There was a negative relationship between survival and amount of time cubs were left unattended, suggesting that parental behaviour affected predation. We propose that a prey switch related to small-rodent abundance caused fluctuations in intraguild predation pressure and that inexperienced females were less able to cope with predation when small rodents were scarce.

A Mid-Atlantic and a National Population Model of Northern Bobwhite Demographic Sensitivity

Numerous field studies have estimated fecundity and survival rates for northern bobwhites (Colinus virginianus), but a synthetic population model based on life-stage simulation analysis (LSA) was only recently developed to examine demographic sensitivity of the finite rate of population change. We compare local demographic parameters of bobwhite versus a national compilation to identify limiting demographic factors for improved regional habitat planning and management. The national compilation provided a useful overview but combined parameters across populations at different latitudes and under different management regimes. We parameterized our LSA model to examine the sensitivity of the finite rate of growth (k) to simulated variation in 9 demographic parameters primarily estimated from field studies for one population in regional decline in New Jersey. Our model results predicted population declines in New Jersey (k 1⁄4 0.55) comparable to the national estimate (k 1⁄4 0.54), but notable differences occurred in sensitivity of demographic variables. The national model predicted winter survival of adults made the greatest contribution to variance of k (r2 1⁄4 0.42) followed by summer survival of adults (r2 1⁄4 0.13), and survival of chicks (r2 1⁄4 0.11). Our regional model for New Jersey also predicted winter and summer survival of adults would make the greatest contribution to variance of k (r2 1⁄4 0.33 and r2 1⁄4 0.13). The New Jersey model, in contrast to the national model, showed that annual variation in components of fecundity had a large effect on Var(k): including clutch size (r2 1⁄4 0.18 vs. national r2 1⁄4 0.01), nest success (r2 1⁄4 0.20 vs. national r2 1⁄4 0.06), and the number of young produced per nest that survived 30 days (r2 1⁄4 0.53 vs. national r2 1⁄4 0.16). Slopes of linear regression between simulated variation in each demographic variable against k were similar between the national and regional models. The slope for number of young produced per nest that survived 30 days with one exception was lower in the New Jersey data indicating more young are required to realize a stationary population. Our simulation results suggest management practices that improve winter survival or the number of young surviving 30 days will have the greatest potential to increase bobwhite population growth rate in New Jersey. Future linkage of models of demographic performance to experimental habitat manipulations will aid regional scientific planning to improve necessary habitat management.

Summer Survival of Translocated Northern Bobwhite in the New Jersey Pine Barrens: Preliminary Results

Northern bobwhite (Colinus virginianus) have declined precipitously since the 1960s, largely due to habitat deterioration and changes in land use; some of the highest declines have been observed in the Mid-Atlantic States. In other regions, attempts to augment bobwhite populations have been relatively successful using translocation. As part of a long-term restocking program, focal areas for translocation in the mid-Atlantic region were identified by biologists at a National Bobwhite Conservation Initiative (NBCI) workshop. The objective of this project is to evaluate translocation to restore bobwhite populations in the New Jersey Pine Barrens, a focal area designated with a high ranking for potential bobwhite recovery. The study site, Pine Island Cranberry Co., is the largest privately owned land tract (>6,000 hectares) in New Jersey, with a mix of shortleaf pine (Pinus echinata), pitch pine (P. rigida), scrub oak (Quercus ilicifolia), and early successional forbes and grasses. For three consecutive years (2015—2017) prior to breeding season, we are translocating eighty radio-collared bobwhite (40 male, 40 female) from wild populations in southwest Georgia. These individuals are radio-located 3-5 times per week, year round. We are collecting microhabitat measurements (e.g., groundcover, understory, and canopy closure) and monitoring nests to characterize habitat use, nest site selection, and nest fate. Survival is estimated using staggered-entry Kaplan-Meier analyses and a Cox proportional hazard model in R to determine covariates of daily mortality. Six of 14 nests were successful in summer 2015 (66 known hatches), and 0 of 12 nests were successful in summer 2016. Snake depredation was the cause of 41.7% of failed nests in 2016. Preliminary analyses produce a five-month adult survival rate of 0.455 (SE = 0.138) for summer 2015 and 0.270 (SE = 0.0516) for 2016. Our planned third summer (2017) of data collection will increase our understanding of these disparate survival estimates.

Top-down limitation of lemmings revealed by experimental reduction of predators.

It is generally recognized that delayed density-dependence is responsible for cyclic population dynamics. However, it is still uncertain whether a single factor can explain why some rodent populations fluctuate according to a 3-4yr periodicity. There is increasing evidence that predation may play a role in lemming population cycles, although this effect may vary seasonally. To address this issue, we conducted an experiment where we built a large exclosure (9ha) to protect brown lemmings (Lemmus trimucronatus) from avian and terrestrial predators. We tested the hypothesis that predation is a limiting factor for lemmings by measuring the demographic consequences of a predator reduction during the growth and peak phases of the cycle. We assessed summer (capture-mark-recapture methods) and winter (winter nest sampling) lemming demography on two grids located on Bylot Island, Nunavut, Canada from 2008 to 2015. The predator exclosure became fully effective in July 2013, allowing us to compare demography between the control and experimental grids before and during the treatment. Lemming abundance, survival and proportion of juveniles were similar between the two grids before the treatment. During the predator-reduction period, summer densities were on average 1.9× higher inside the experimental grid than the control and this effect was greatest for adult females and juveniles (densities 2.4× and 3.4× higher, respectively). Summer survival was 1.6×higher on the experimental grid than the control whereas body mass and proportion of juveniles were also slightly higher. Winter nest densities remained high inside the predator reduction grid following high summer abundance, but declined on the control grid. These results confirm that predation limits lemming population growth during the summer due to its negative impact on survival. However, it is possible that in winter, predation may interact with other factors affecting reproduction and ultimately population cycles.

Male experience buffers female laying date plasticity in a winter-breeding, food-storing passerine

Phenotypic plasticity allows individuals to adjust reproductive timing in response to variation in the environment but little is known about how other factors, such as habitat quality, social environment and experience, may influence adjustments in the timing of breeding. We evaluated intrinsic (female age), environmental and social factors influencing laying date plasticity and assessed the effect of laying date on reproductive success in a population of grey jays, Perisoreus canadensis , over nearly four decades (1978–2015). Grey jays rely on stored food during their late-winter nesting season, a unique life history context to study plasticity in reproductive timing. Overall, females tended to lay eggs earlier in response to higher prelaying temperatures and advanced laying date at similar rates over their lives. Male age interacted with both temperature and female age to influence laying date. Females mated to older males were more likely to breed earlier at lower temperatures than females mated to younger males but there was little effect of male age under warmer conditions. Similarly, younger females mated to older males were more likely to breed earlier than younger females mated to younger males but there was little effect of male age when females were older. Across all years, earlier laying relative to other breeders in the population led to higher probability of nest success and summer survival for dominant juveniles. Our results suggest that individual females adjust laying date in response to temperature and provide the first evidence that male experience plays an important, and probably underappreciated, role in how females adjust their timing of breeding over their lives and with respect to annual variation in the environment.