Program MARK Research Articles

Factors Influencing Survival of Black-chinned Hummingbird Nests in Southwest Colorado

We estimated survival of Black-chinned Hummingbird (Archilochus alexandri) nests in southwest Colorado in 1998, 2001, and 2004 by means of models generated in program Mark. The best supported, and parsimonious, model suggested nest age (i.e., time since the nest was initiated) as the most important variable in indicating nest survival; daily survival rates of nests with eggs were lower than those of nests with nestlings. Substrate type was a second covariate that had some support in describing nest survival. Nests in Gambel oak (Quercus gambelii) or narrow-leaf cottonwood (Populus angustifolia) had greater daily survival rates than did those built in other substrates. No other ecological covariates were strongly supported in explaining nest survival. Of the 24 nests studied, 10 were successful, fledging an average of 1.7 (standard error 0.14) chicks.

Effects of Anthropogenic and Climate-Induced Habitat Changes on Adult Female Mule Deer Survival

Increased wildfire size and frequency, invasion of non-native annual grasses, extensive fire suppression, climate change, and widespread juniper expansion have led to dramatic changes in sagebrush ecosystems, which provide habitat for a suite of wildlife species, including mule deer (Odocoileus hemionus). These landscape-level disturbances can cause habitat loss and degradation, which influence the quantity and quality of available forage and can negatively influence adult female mule deer survival. We used Program MARK to estimate survival rates using a known-fate model. Our dataset included 111 radio-collared female mule deer to estimate monthly survival rates and to investigate factors that may affect these rates, including movement behavior (migratory or resident) and habitat characteristics (wildfire and juniper canopy cover) in mule deer habitats supporting sagebrush potential vegetation types (PVTs). The dataset included 116 421 Global Positioning System (GPS) location points from 2015 to 2017 in the John Day Basin, Oregon, United States. Survival averaged 0.78 (95% confidence interval = 0.61–0.82) across the study period but was 0.69 (95% confidence interval = 0.59–0.77) in 2015. Our results indicated survival was positively influenced by the presence of small amounts of recent fire (< 15% of total winter range burned; 1−20 yr postfire) within an individual's winter range. Annual survival (0.78) was low compared with survival rates for adult female mule deer in other parts of their geographic range. These findings demonstrate how postfire vegetation response can have a positive effect on mule deer survival, regardless of their migration strategy. Our findings also indicate how climate change poses a growing threat to mule deer populations as prolonged periods of drought increase the spread of fatal diseases.

Histone methylation regulates reproductive diapause in Drosophila melanogaster.

Fluctuating environments threaten fertility and viability. To better match the immediate, local environment, many organisms adopt alternative phenotypic states, a phenomenon called "phenotypic plasticity." Natural populations that predictably encounter fluctuating environments tend to be more plastic than conspecific populations that encounter a constant environment, suggesting that phenotypic plasticity can be adaptive. Despite pervasive evidence of such "adaptive phenotypic plasticity," gene regulatory mechanisms underlying plasticity remains poorly understood. Here we test the hypothesis that environment-dependent phenotypic plasticity is mediated by epigenetic factors. To test this hypothesis, we exploit the adaptive reproductive arrest of Drosophila melanogaster females, called diapause. Using an inbred line from a natural population with high diapause plasticity, we demonstrate that diapause is determined epigenetically: only a subset of genetically identical individuals enter diapause and this diapause plasticity is epigenetically transmitted for at least three generations. Upon screening a suite of epigenetic marks, we discovered that the active histone marks H3K4me3 and H3K36me1 are depleted in diapausing ovaries. Using ovary-specific knockdown of histone mark writers and erasers, we demonstrate that H3K4me3 and H3K36me1 depletion promotes diapause. Given that diapause is highly polygenic, that is, distinct suites of alleles mediate diapause plasticity across distinct genotypes, we also investigated the potential for genetic variation in diapause-determining epigenetic marks. Specifically, we asked if these histone marks were similarly depleted in diapause of a genotypically distinct line. We found evidence of divergence in both the gene expression program and histone mark abundance. This study reveals chromatin determinants of phenotypic plasticity and suggests that these determinants may be genotype-dependent, offering new insight into how organisms may exploit and evolve epigenetic mechanisms to persist in fluctuating environments.

Genetic mark–recapture analysis reveals large annual variation in pre‐breeding sex ratio of greater sage‐grouse

Sex ratio, and the extent to which it varies over time, is an important factor in the demography, management, and conservation of wildlife populations. Greater sage‐grouse Centrocercus urophasianus populations in western North America are monitored using counts of males at leks in spring. Population estimates derived from lek‐count data typically assume a constant, female‐biased sex ratio, yet few rigorous, empirically derived estimates of sex ratio are available to test that assumption. We estimated pre‐breeding sex ratio of greater sage‐grouse in a peripheral, geographically isolated population in northwestern Colorado during two consecutive winters using closed‐population, robust‐design, multi‐state, genetic mark–recapture models in program MARK. Sex ratio varied markedly between years, with estimates of 3.29 (95% CI: 2.36–4.59) females per male in winter 2012–2013 and 1.54 (95% CI: 1.22–1.95) females per male in winter 2013–2014. Rather than assuming a constant sex ratio, biologists should consider the potential for large annual variation in sex ratio of greater sage‐grouse populations when estimating population size or trend from male lek‐count data.

Using mobile smartphones and bioacoustics to monitor endangered bird species

Monitoring the status of endangered wildlife is a critical foundation for biodiversity conservation efforts. The use of autonomous acoustic recorders to monitor wildlife has become increasingly popular in terrestrial tropical systems. However, these recorders are expensive and not available for purchase and repair in all countries. The development of easy‐to‐use and low‐cost devices is therefore needed for applications worldwide. In this study, we modified and installed smartphone devices to operate and record sounds produced by the Vietnamese Crested Argus Rheinardia ocellata in Kon Chu Rang Nature Reserve, Vietnam, in 2021. We used the software package RAVEN to create spectrograms and to identify Crested Argus calls from acoustic recordings and used the program MARK to estimate occupancy and detection probabilities. We recorded calls of Crested Argus at 16 of 40 locations and most calls were recorded in the northern and eastern parts of the nature reserve. Our model‐averaged estimates of detection probabilities indicated that detection in the morning or afternoon was c. 0.50 and constant over seven sampling days. Our overall average occurrence probability of Crested Argus was 0.43 (standard error = ±0.08), but we found occupancy to be positively correlated with distance to the nearest village, indicating that poaching may negatively affect this species. Based on these data we suggest that the Kon Chu Rang Nature Reserve and possibly two adjacent nature reserves, namely An Toan Nature Reserve and Ba To Proposed Nature Reserve, might be important sites for Crested Argus.

Density, Apparent Survival, and Local Population Size of Louisiana Pigtoe (Pleurobema riddellii) in the Neches River, Texas

Most North American unionids are imperiled to some degree, including the Louisiana Pigtoe, Pleurobema riddellii, which is currently under review for listing under the U.S. Endangered Species Act. Understanding a species' population dynamics, including spatial and temporal variation in survival, density, recruitment, and population size, is vital for conservation, but this information is lacking for P. riddellii. We conducted a mark–recapture study to estimate apparent survival, density, recruitment, and population size of P. riddellii within a 25-m2 area at three sites (75 m2 total) in the Neches River, Texas from 2014 to 2019. We used the program MARK to evaluate POPAN models for estimating population parameters. We collected a total of 392 unique individuals of P. riddellii over the 5-yr period and the observed recapture rate averaged 55.6%. The most parsimonious POPAN model indicated that apparent survival varied temporally, the recapture rate varied temporally and spatially, and both the entry probability (recruitment) and population size varied spatially. Apparent survival averaged 83.3% ± 3.4% (SE)/yr, overall population size across the three sites was 429 individuals (overall density = 5.7/ m2), and recruitment averaged 6.3%/yr. High survival, relatively high density, the presence of recruitment, and the lack of temporal changes in population size suggest that these populations are stable. The presence of P. riddellii throughout a long section of the river, including localized patches of higher abundance, suggests that the total population size in the Neches River is relatively large and the river is a global stronghold for the species.

A contemporary estimate for the abundance of juvenile American Eel Anguilla rostrata attempting to migrate past a barrier in the Ottawa River

AbstractAmerican Eel (Anguilla rostrata) travels from the Sargasso Sea to fresh waters of eastern North America and back in a lifetime, and once provided one of the most abundant eel fisheries in the world. Many American Eel populations are now at risk worldwide. Dams act as barriers to the upstream migration of juvenile American Eels, which can be partially mitigated by installing eel ladders. To inform mitigation decisions and provide baseline data, the number of eels approaching barriers should be estimated; however, estimation is difficult for this now rare and cryptic species, especially in large rivers. In St. Lawrence and Ottawa River system, American Eels are among the largest and most fecund of the species, and local populations in the Ottawa River are almost entirely composed of large, female eels. American Eel in this area has declined to less than 1% of historic abundance, yet no local population estimates are available to inform recovery strategies and management actions. We, therefore, evaluated data from an unpublished study to estimate the abundance of American Eel attempting to migrate upstream past a barrier. American Eels (n = 339) were captured at the Carillon Generating Station over 36 days (July 12, 2010–August 17, 2010). Results were fit to the POPAN Jolly‐Seber model in program MARK. Future studies could be improved by sampling throughout the migration season and deploying multiple traps spanning downstream features. While confidence intervals in the best‐fitting model were wide, the estimate nonetheless provides a baseline to inform future work and management.

Informing wind energy development: Land cover and topography predict occupancy for Arizona bats.

Wind energy is a growing source of renewable energy with a 3-fold increase in use globally over the last decade. However, wind turbines cause bat mortality, especially for migratory species. The southwest United States has high bat species diversity and is an important area for migratory species, although little is known about their seasonal distribution. To examine potential risk to bats in areas proposed for wind energy development, we characterized bat occupancy spatially and temporally across northern Arizona, identifying use during summer when bats are reproductively active and fall during the migratory season. Our objectives were to determine occupancy of migratory species and species of greatest conservation need and develop a probability of occupancy map for species to identify areas of potential conflict with wind energy development. We selected 92 sites in 10 clusters with potential for development and used acoustic detectors to sample bats in the summer and fall of 2016 and 2017 for 6 nights per site per year. We predicted response of migratory bat species and species of special concern to 9 landscape variables using Program MARK. During summer, higher densities of forest on the landscape resulted in a higher probability of occupancy of migratory species such as hoary bats (Lasiurus cinereus), silver-haired bats (Lasionycteris noctivagans), big free-tailed bats (Nyctinomops macrotis), and species of conservation need such as spotted bats (Euderma maculatum). During the fall, higher concentration of valleys on the landscape predicted occupancy of hoary bats, big free-tailed bats, and spotted bats. High bat occupancy in the fall was also associated with higher elevation and close proximity to forests. We recommend that wind turbines be placed in open, flat grasslands away from forested landscapes and concentrations of valleys or other topographic variation.

Occurrence patterns of wild turkeys altered by wild pigs

Eastern wild turkeys (Meleagris gallopavo silvestris) are an important game bird in the United States, particularly in the Southeast. The introduction of wild pigs (Sus scrofa) can negatively affect native wildlife, habitat quality, and ecosystem functions. To explore the potential effects that pig presence, through habitat degradation and interspecific competition, may have on wild turkeys, we evaluated changes in occupancy of co-occurring wild pigs and wild turkeys.We deployed camera-monitored bait stations on 3 wildlife management areas in Arkansas during January–April 2017–2019 and collected >680,000 images to determine turkey and wild pig occurrence. We evaluated presence/absence of turkeys and wild pigs in camera trap images using Timelapse2 image analyzer software® and then used program MARK to create 2-species occupancy models and determine the effect of wild pig presence and various landscape covariates on the occupancy and detectability of wild turkeys. The occupancy rate of wild pigs was 50.4% (95% CI = 46.9%–54.0%) and included positive relationships with the percent cover of deciduous forest and the number of wildlife openings within 500 m. The occupancy rate of turkeys increased from 45.5% (95% CI = 39.3%–51.6%) when wild pigs were not present to 59.4% (95% CI = 45.2%–73.5%, 95%) when wild pigs were present, indicating a tendency of the 2 species to select for similar environmental conditions (Species Interaction Factor = 1.13). Detectability of turkeys decreased when wild pigs occupied a site at any point during the season, regardless of whether or not the wild pigs were detected during the same trapping occasion. The decrease in detectability suggests a possible short-term displacement of turkeys by wild pigs. This displacement can have indirect effects through alteration of breeding behaviors and altered habitat use patterns, and these indirect effects represent an important topic for research moving forward.

Carnivore Occupancy within the Early Successional Habitat of New England Cottontails

Abstract Predation pressure from carnivores can shape ecological communities and has significant consequences for prey species that are declining or recovering from historical declines. New England cottontails Sylvilagus transitionalis are a species of greatest conservation need in Connecticut and are experiencing continued decline associated with habitat loss. Restoration of early successional habitat is underway to address the most significant threat to their populations. However, one of the largest documented sources of mortality is associated with several key predators and remains a threat to recovery efforts. We sought to develop species-specific occupancy estimates of carnivores in early successional habitat and relate our findings to the potential recovery of New England cottontails. We conducted camera surveys at 34 sites in early successional habitat in or near New England cottontail focus areas throughout Connecticut and used the program MARK to estimate occupancy and detectability from detection data. We found key predators in early successional habitat, but their detectability was generally low. Occupancy was highest for coyotes Canis latrans, and regional occupancy differed only for bobcats Lynx rufus. Covariates that influenced parameter estimates in our models included high road densities and the intensity of New England cottontail and eastern cottontail Sylvilagus floridanus detections. Expanding carnivores, particularly coyote and bobcat, may place additional pressure on New England cottontail recovery in the state, but restoration efforts that promote contiguous habitat and reduce isolated patches where predation risk is higher will improve their chances of a long-term recovery.

Integrating video and genetic data to estimate annual age‐structured apparent survival of American black bears

AbstractCamera or genetic data are increasingly used to estimate wildlife abundance and density. We integrated video camera data with genetic data over 7 years to estimate annual age‐structured apparent survival of American black bears (Ursus americanus). We identified 70 individuals through meticulous scrutiny of 7531 video captures, cross‐referenced with 721 genetic captures from hair samples concurrently collected from stations in view of cameras. We used the Cormack–Jolly–Seber model in Program Mark to estimate annual age‐structured apparent survival for yearling males, yearling females, 2+ year‐old males, and 2+ year‐old females. We manually calculated cub survival. We compared parameter estimates based on combined video and genetic data with those based on only genetic data. Combining video and genetic data provided a means to test video‐based identification accuracy, which was highest for females (97%–100%). Annual apparent survival was highest for yearling females (φ = 0.92, SE = 0.07), followed by 2+ year‐old females (φ = 0.88, SE = 0.05), 2+ year‐old males (φ = 0.84, SE = 0.06), and yearling males (φ = 0.80, SE = 0.14). Annual cub survival (φ = 0.86, SE = 0.07) was likely biased because we could not account for mortality that occurred in‐den through early spring. Annual apparent survival and recapture probabilities derived from only genetic data were lower than those derived from combined video and genetic data. Our finding that noninvasive data can be used to estimate annual age‐structured apparent survival of a species with relatively indistinct traits is broadly relevant to wildlife research and conservation.

Age-specific, population-level pedigree of wild black bears provides insights into reproduction, paternity, and maternal effects on offspring apparent survival.

Wildlife pedigrees provide insights into ecological and evolutionary processes. DNA obtained from noninvasively collected hair is often used to determine individual identities for pedigrees and other genetic analyses. However, detection rates associated with some noninvasive DNA studies can be relatively low, and genetic data do not provide information on individual birth year. Supplementing hair DNA stations with video cameras should increase the individual detection rate, assuming accurate identification of individuals via video data. Video data can also provide birth year information for individuals captured as young of the year, which can enrich population‐level pedigrees. We placed video cameras at hair stations and combined genetic and video data to reconstruct an age‐specific, population‐level pedigree of wild black bears during 2010–2020. Combining individual birth year with mother–offspring relatedness, we also estimated litter size, interlitter interval, primiparity, and fecundity. We used the Cormack‐Jolly‐Seber model in Program Mark to evaluate the effect of maternal identity on offspring apparent survival. We compared model rankings of apparent survival and parameter estimates based on combined genetic and video data with those based on only genetic data. We observed 42 mother–offspring relationships. Of these, 21 (50%) would not have been detected had we used hair DNA alone. Moreover, video data allowed for the cub and yearling age classes to be determined. Mean annual fecundity was 0.42 (95% CI: 0.27, 0.56). Maternal identity influenced offspring apparent survival, where offspring of one mother experienced significantly lower apparent survival (0.39; SE = 0.15) than that of offspring of four other mothers (0.89–1.00; SE = 0.00–0.06). We video‐documented cub abandonment by the mother whose offspring experienced low apparent survival, indicating individual behaviors (e.g., maternal care) may scale up to affect population‐level parameters (e.g., cub survival). Our findings provide insights into evolutionary processes and are broadly relevant to wildlife ecology and conservation.

Abundance and effect of health status on apparent survival of Guiana dolphins, Sotalia guianensis, in an open embayment in north‐eastern Brazil

Abstract Guiana dolphins (Sotalia guianensis) inhabit shallow waters of the tropical western Atlantic, an area that is now mostly occupied by cities and harbours. Demographic studies have been concentrated in sheltered areas of south/south‐eastern Brazil. This study investigated site fidelity and estimated population abundance and apparent survival of Guiana dolphins in Mucuripe Embayment (ME), on the north‐eastern Brazilian coast, through photo‐identification surveys and closed and open population mark–recapture models, from October 2009 to September 2011. Forty‐six Guiana dolphin groups were recorded (in groups of between one and eight dolphins, with a mean ± SD of 3.49 ± 2.33) in 27 out of 40 surveys. Twenty‐five animals were photo‐identified, with eight considered to have a ‘poor health’ status. The standardized site fidelity index (SSFI) was low (0.25). Using the program capture, the time and heterogeneity model (Mth) resulted in a total abundance estimate of 39, with a Coefficient of Variation (CV) of 21% (95% CI 35–80%). In program mark, model averaging resulted in a total abundance estimate of 33 (CV 32%, 95% CI 30–100%). Using a CV of 21%, the power to detect a decline of 50% during the study period was 0.44 and the power to detect a decline of 5% a year was 0.11. To detect these declines with a 0.90 power, 12 years of monitoring would be necessary. The annual adult apparent survival rate was low (0.71; CV 19%; 95% CI 0.40–0.90), and differed for dolphins in ‘good’ (0.64; CV 28%, 95% CI 0.27–0.89) and ‘poor’ (0.85; CV 22%; 95% CI: 0.23–0.99) health. The low abundance of Guiana dolphins in ME indicates that conservation actions should start immediately, such as creating a marine protected area, continuing awareness campaigns, using by‐catch reduction technologies, developing new regulations, and promoting law enforcement. Monitoring studies must continue with increased effort to reduce uncertainty in estimates and to improve the power to detect trends of decline.

Monitoring Occupancy of Bats with Acoustic Data: Power and Sample Size Recommendations

Bats are difficult to study due to their nocturnal, cryptic, and highly vagile nature. Ongoing advances in acoustic recording hardware and call classification software have made species detection and activity monitoring more feasible. Our objectives were to determine the effort necessary to monitor bat assemblages using an occupancy framework and acoustic data and to provide guidelines for researchers interested in developing similar monitoring programs. We collected data at 2 study areas in South Texas from June through September in 2015, 2016, and 2017. We used Pettersson D500X Mk II real-time full-spectrum detectors and classified sound files using SonoBat bat call analysis software. We attempted to collect data during 2 visits to individual sites, with up to 5 consecutive nights per visit each year. We estimated occupancy rates for each species in each study area using occupancy models in Program MARK and included terms to define trends in detection probability through the season. Over the 3 years of our study, we sampled 106 sites with 803 sampling nights and classified a total of 2880 sound files to 7 species. Data sets for 6 of the species supported models indicating that detection probability varied throughout our sampling period. Our results generally indicate that sample sizes between 10 and 20 sites would be required to detect declines in occupancy of 50% over 25 years using 10 nights per site with a starting occupancy rate of 0.70. Detecting declines of 30% in 10 years may require >75 sampling sites. Finally, our analysis shows that recognizing seasonal variation in detection probability, and then timing surveys accordingly, can greatly reduce sample size requirements.

Survival estimates of free-living arctic ground squirrels (Urocitellus parryii): effects of sex and biologging

Hibernation is associated with long lifespan: on average, hibernating mammals live 15% longer than nonhibernators of equivalent mass. We investigated how survival varies with sex, season, and the deployment of biologgers in arctic ground squirrels (Urocitellus parryii (Richardson, 1825)), a widely distributed northern hibernator. The duration of hibernation in arctic ground squirrels differs markedly by sex: females hibernate 30% longer each year than males, a behavioural trait that could positively affect female survival. Additionally, males engage in aggressive territorial and food cache defense in spring and fall, which may decrease survival in this sex. From 13 years of mark–recapture data, we estimated apparent survival of arctic ground squirrels in Arctic Alaska (USA) using Cormack–Jolly–Seber models in program MARK. We found that females had higher annual survival ([Formula: see text] (95% confidence interval (CI): 0.469, 0.913)) than males ([Formula: see text] (95% CI: 0.416, 0.670)), with a maximum observed lifespan (10 years) that exceeded that of males (6 years). We also show that biologger use and implantation did not significantly impact survival. Quantifying basic arctic ground squirrel demographics from this well-studied population illustrates how sex-specific hibernation parameters may influence lifespan differences in male and female arctic ground squirrels and provides support for the safety of biologging devices.

Effects of spring weather on laying dates, clutch size, and nest survival of ground-nesting passerines in abandoned fields

Weather conditions have a significant impact on the life-history strategies of birds. The mechanisms by which weather variability drives demographic processes in boreal passerines have been investigated insufficiently. We examined the effects of spring weather on first egg-laying dates, clutch size, and nest survival of Booted Warbler (<em>Iduna caligata</em>) and Whinchat (<em>Saxicola rubetra</em>) breeding in abandoned agricultural fields in the north of European Russia in 2005–2019. We used general linear models to express first egg-laying dates and clutch size and program MARK to model nest survival as a function of weather variables. Our results demonstrated that variability of May precipitation and averaged daily temperature are important drivers of first egg dates, clutch size, and nest survival in both species. The first egg dates of Booted Warblers and Whinchats were determined primarily by the May temperature: the warmer the weather in May, the earlier the laying dates. Taking into account the effect of the first egg date, the clutch size of Booted Warblers strongly depended on the May averaged daily temperatures, whereas the clutch size of Whinchats was weakly affected by May precipitation. The spring weather had a strong impact on Booted Warbler and Whinchat nest survival, potentially by influencing the activity of nest predators. We suggest that years with a coincidence of low spring precipitation and temperature are the

Evaluating Release Strategy for Translocated Northern Bobwhites in Cross Timbers Ecoregion of Texas: A Pilot Study

Northern bobwhite (Colinus virginianus) population decline is largely driven by the loss, fragmentation, and degradation of grassland habitats. Translocation is used to reintroduce or augment populations in fragmented landscapes where natural dispersal is inhibited. Northern bobwhites have been successfully translocated in the southeastern portion of their range, but outcomes of translocations in western ranges have been mixed. Our objective was to conduct a pilot study to test the feasibility of translocating northern bobwhites to a restored, but isolated, habitat in the Cross Timbers ecoregion of Texas, USA and to evaluate the influence of release strategy for improving northern bobwhite site fidelity and survival post-release. The release property was restored through brush management, native species seeding, and proper grazing management. We trapped and translocated 84 northern bobwhites from source populations in the Rolling Plains and Edwards Plateau ecoregions during March 2015. Coveys were assigned to either delayed or immediate release treatment. We radio-collared all hens (n = 40; 11 adults; 29 juveniles) and evenly divided the sample between delayed and immediate releases. Delayed release coveys were held on the release site for 4 weeks in a Surrogator® (Wildlife Management Technologies, LLC). We trapped and radio-collared resident hens (n = 15) in March and monitored all hens through breeding season (March–August; 180 days). We implemented a 2-state (alive or dead) multistate model in Program MARK to analyze survival as a function of the release treatment, resident status, and age. We found no evidence that survival differed between translocated and resident hens (β = 0.48, standard error [SE] = 0.38), release treatments (β = 0.10, SE = 0.40), or age (β = -0.16, SE = 0.54). Daily survival for all hens was 0.99 (SE = 0.009) and breeding season survival was 0.19 (SE = 0.08). Four (20%) immediate, 2 (10%) delayed release, and 0 resident hens dispersed off-property. Translocated and resident hens survived at similar rates, indicating that translocation may be a feasible management strategy for augmenting a northern bobwhite population on restored habitats in the Cross Timbers ecoregion although overall survival was low. We did not find evidence that delayed release improved daily survival post-release, but our small sample size may have prevented us from detecting a difference. However, delayed release birds were effectively sheltered from predation during peak raptor migration. Additional research is needed to fully understand population dynamics and implications of release strategy for translocated northern bobwhite.

Bayesian mark–recapture–resight–recovery models: increasing user flexibility in the BUGS language

AbstractEstimating demographic parameters of interest is a critical component of applied conservation biology and evolutionary ecology, where demographic models and demographic data have become increasingly complex over the last several decades. These advances have been spurred by the development and use of information theoretic approaches, programs such as MARK and SURGE, and Bayesian inference. The use of Bayesian analyses has also become increasingly popular, where WinBUGS, JAGS, Stan, and NIMBLE provide increased user flexibility. Despite recent advances in Bayesian demographic modeling, some capture–recapture models that have been implemented in Program MARK remain unavailable to quantitative ecologists that wish to use Bayesian modeling approaches. We provide novel parameterizations of capture–mark–recapture–resight–recovery models implemented in Program MARK that have not yet been implemented in the BUGS language. Simulations show that the models described herein provide accurate parameter estimates. Our parameterizations of these models can easily be extended to estimate additional parameters such as entry probability, additional live states, or cause‐specific mortality rates. Additionally, implementing these models in a Bayesian framework allows users to readily estimate parameters as mixtures, incorporate random individual or temporal variation, and use informative priors to assist with parameter estimation.

Survival of western Gulf Coast Mottled Ducks (Anas fulvigula) in the path of a Category 4 hurricane.

Tropical cyclones are the most powerful storms on earth, causing catastrophic damage to human lives and infrastructure. Hurricanes also cause wildlife mortality when they make landfall, but the severity of these effects is difficult to quantify because data collection is either logistically impossible or deprioritized in the wake of human tragedy. On August 27, 2020, Hurricane Laura made landfall in southwestern Louisiana with maximum sustained winds of 241 kph (150 mph), making it one of the most powerful storms to strike the mainland United States. Hurricane Laura passed directly over the core breeding range of the western Gulf Coast population of Mottled Duck (Anas fulvigula), during a time when many adult birds were undergoing a simultaneous wing feather molt and were flightless. We used GPS‐GSM telemetry data to evaluate survival rates of adult female Mottled Ducks in late summer 2020 (bracketing August 27 by one month on either side) relative to the same period in 2018 and 2019. Mortality was lower in 2018 (12 out of 29; 41%) and 2019 (8 out of 28; 29%) than in 2020 (12 out of 18; 67%), and 7 out of 12 mortalities documented in 2020 occurred when Hurricane Laura made landfall. Survival analyses in program MARK confirmed lower survival probability in 2020, but there was overlap in 85% confidence intervals in all years. This single storm resulted in the death of ~40% of all marked birds in our sample, suggesting that hurricanes have the potential to influence population demographics. In addition, Hurricane Laura resulted in widespread habitat loss and degradation that has reduced available nesting habitat in 2021, and possibly for years to come. The acute and chronic effects of hurricanes may exacerbate Mottled Duck population declines, which may worsen in the face of increasingly frequent and more severe tropical storms.

Diverse demographic factors influence apparent juvenile survival in a migratory songbird

AbstractTo better understand the dynamics of avian populations and their role in population trends, we require an in‐depth understanding of the factors influencing the survival of adults and juveniles. However, assessing survival in juveniles is often challenging, especially in small, migratory species where individuals typically disperse from the study area and are not available for recapture in subsequent years. Bobolinks (Dolichonyx oryzivorus) are a long‐distance migrant that exhibits natal philopatry in at least one population, allowing for more comprehensive juvenile survival analyses than in many other long‐distance avian migrants. Using a 17‐yr dataset from two sites representing a Vermont population of Bobolinks, we used Program MARK to assess factors influencing apparent juvenile survival, including factors related to nesting timing, nest attempt number, the philopatric behaviors of relatives, body mass, brood size, and agricultural management scheme. Our top models indicated that nest attempt number and whether or not a nest mate also survived and returned to breed locally were important factors explaining variation in apparent survival in juvenile Bobolinks. Specifically, juveniles from first nest attempts that fledged earlier in the season, with siblings that did not survive and return to breed locally, showed higher apparent survival. Factors such as site and the philopatric behavior of females associated with nests also appeared in top‐ranking models, while factors such as body mass and brood size did not. These results indicate the importance of providing high‐quality breeding habitat to birds early in the season when juvenile survival is greatest and indicate that individuals may be utilizing inbreeding avoidance strategies. These results provide new insight into the ecological and agricultural management factors influencing survival in migratory species that use managed habitats and underscore the importance of integrating juvenile survival data into current management schemes to better support this and other declining species.