Browsing by Author "Gibson, Daniel"
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- Application of Bayesian robust design model to assess the impacts of a hurricane on shorebird demographyGibson, Daniel; Riecke, Thomas V.; Keyes, Tim; Depkin, Chris; Fraser, James D.; Catlin, Daniel H. (Ecological Society of America, 2018-08)The increasing use of Bayesian inference in population demography requires rapid advancements in modeling frameworks to approach the rigor and flexibility of the current suite of maximum-likelihood models. We developed an unbiased, Jolly-Seber robust design (JSRD) model that is both accessible and generalizable in a Bayesian hierarchical multistate framework. We integrated band and age-classification data to estimate site entry, temporary emigration, and apparent survival rates, as well as estimate age-class specific abundances. The complete model parameterization is provided in the Appendix S1, as well as tools for simulating capture histories and an assessment of model fit. We applied this model to determine whether these demographic processes in non-breeding population of American oystercatchers (Haematopus palliatus) were affected by a major hurricane event (Hurricane Matthew) in coastal Georgia. The JSRD model was demonstrably unbiased at relatively small sample sizes, and the majority of parameters were identifiable in the fully saturated model parameterization. In the model application, we found that Hurricane Matthew temporarily altered local population abundances of American oystercatchers through increased movements of individuals into and out of the observable population, but mortality rates were largely unaffected. Together, our results suggest that American oystercatchers were largely able to avoid the immediate demographic consequences (i.e., reduced survival) of Hurricane Matthew. Integrating age and band ratios from survey data allowed for more descriptive and potentially less biased estimates of age-specific abundance, relative to estimates generated solely from either mark-resight or survey data.
- Atlantic Flyway Disturbance Project Phase 2: Biological Data Collection ReportGibson, Daniel; Hunt, Kelsi L.; Catlin, Daniel H. (2021)Human disturbance is a significant threat facing shorebirds throughout the annual cycle, and threats to shorebird habitats may be exacerbated by increased human use (e.g., beach recreationists, off-leash dogs), reducing the amount of coastal habitat that is functionally available to shorebirds. We worked with partners across the Atlantic flyway to develop a standardized protocol for data collection to evaluate the effects of human disturbance on six Atlantic Flyway Shorebird Initiative (AFSI) focal species (American Oystercatchers [AMOY; Haematopus palliates], Piping Plovers [PIPL; Charadrius melodus], Red Knots [REKN; Calidris canutus], Sanderling [SAND; Calidris Alba], Semipalmated Sandpipers [SESA; Calidris pusilla], and Wilson’s Plovers [WIPL; Charadrius wilsonia]).
- Direct and indirect effects of nesting density on survival and breeding propensity of an endangered shorebirdCatlin, Daniel H.; Gibson, Daniel; Hunt, Kelsi L.; Friedrich, Meryl J.; Weithman, Chelsea E.; Karpanty, Sarah M.; Fraser, James D. (ESA, 2019-04-08)Density-dependent regulation is a fundamental part of ecological theory and a significant driver of animal demography often through complex feedback loops. We investigated the relationship between flood- and demographically induced fluctuations in density and the breeding propensity and survival of a pioneer species, the piping plover (plover, Charadrius melodus).We captured and marked adult and hatchling plovers on the Gavins Point Reach of the Missouri River in South Dakota and Nebraska, USA, from 2005 to 2014. In 2010 and 2011, historically high water levels and flooding inundated much of the plover’s sandbar nesting habitat on theMissouri River.We developed a Bayesian formulation of a multievent model, or a multistate survival model with state uncertainty to estimate breeding propensity simultaneously with survival. Although plovers are conspicuous, their breeding status can be difficult to establish with certainty, which necessitated the use of uncertain states.With this model, we investigated the effect of sex, habitat availability, river flow, and density (birds/ha nesting habitat) on survival of hatch year and breeding and non-breeding adult plovers. In addition, we estimated the transition rates for these age classes between breeding and nonbreeding states. Non-breeding adults (ɸAHY, n = 0.58 ± 0.06) had lower survival rates than breeding adults (ɸAHY, b = 0.80 ± 0.04), and both breeding survival and breeding propensity decreased with increasing nesting density. Not only did survival and breeding propensity decrease directly at higher nest densities, but survival also was indirectly impacted by increasing the proportion of non-breeding birds with relatively low survival. Thus, plovers were regulated through a complex set of feedback loops, acting as densities increased. Our findings underscore the intricacy of density-dependent regulation and suggest that detailed demographic studies are needed to fully understand these effects.
- Fitness landscapes and life-table response experiments predict the importance of local areas to population dynamicsKane, Kristin; Sedinger, James S.; Gibson, Daniel; Blomberg, Erik; Atamian, Michael (Ecological Society of America, 2017-07)Animal resource requirements differ among life-history stages, and thus, habitat is most appropriately thought of as specific to a particular life stage. Accordingly, different habitats may vary in their significance as functions of (1) the sensitivity of population growth to the life stage for which the habitat is most important, (2) spatial association of each habitat to other habitats, and (3) the abundance of the habitat in question. We used an analogy to a life-table response experiment to develop spatial models linking key habitats to rates of population increase in Greater Sage-grouse. We parameterized models linking demographic rates to vegetation and physical attributes of habitats, including spatial association of some habitats to others, using a decade-long study of Greater Sage-grouse in central Nevada. We modeled the contribution of each pixel in the landscape to regional k (finite rate of population increase) using functional relationships between demographic rates and the attributes of that pixel, and the sensitivity of k to each demographic rate. We incorporated the following demographic rates into our model: female nesting success, survival of chicks from hatching to 45 d, and adult female annual survival. We also incorporated the probability a site was used for nesting. Chick survival (62%) and nest site selection (21%) explained most of the variance in lambda. We found that only similar to 8% of all habitat for Greater Sage-grouse contributed to lambda > 1. Habitat supporting population growth occurred in mid-high elevation areas with moderate slopes, and a high percent cover of sagebrush, and in nesting areas close to late-brood habitat. Our models indicate that a relatively small proportion of habitat available to Greater Sage-grouse in central Nevada is responsible for maintenance of the population in our study system. We suggest that the general approach we describe here can be used to improve understanding of habitats most likely to regulate populations in other systems, providing an important tool in ecology and conservation.
- Habitat selection and potential fitness consequences of two early‐successional species with differing life‐history strategiesCatlin, Daniel H.; Gibson, Daniel; Friedrich, Meryl J.; Hunt, Kelsi L.; Karpanty, Sarah M.; Fraser, James D. (Wiley, 2019-11-19)Habitat selection and its relationship to fitness is a fundamental concept in ecology, but the mechanisms driving this connection are complex and difficult to detect. Despite the difficulties in understanding such intricate relationships, it is imperative that we study habitat selection and its relationship with fitness. We compared habitat selection of least terns (Sternula antillarum) and piping plovers (Charadrius melodus) on the Missouri River (2012–2014) to examine the consequences of those choices on nest and chick survival. We hypothesized that plovers and terns would select habitat that minimized the chance of flooding and predation of eggs, chicks, and adults, but that plovers would also select habitat that would provide foraging habitat for their chicks. We developed an integrated habitat selection model that assessed selection across multiple scales (sandbar and nest scales) and directly modeled the effect of selection on nest and chick survival. In general, the species selected habitat in keeping with our hypotheses, such that predation and flooding, in particular, may have been reduced. Sandbar selection had either a negative or no appreciable effect on nest survival for both species across years. Nest‐site selection in 2012 had a generally positive effect on nest survival and chick survival for both terns and plovers, and this trended toward a negative effect by 2014. This result suggested that early selection decisions appeared to be adaptive, but we speculate that relatively high site fidelity and habitat degradation led to reduced benefit over time. Our results highlight the complex nature of habitat selection and its relationship to fitness.
- Piping plover chick ecology following landscape-level disturbanceRobinson, Samantha G.; Walker, Katie M.; Bellman, Henrietta A.; Gibson, Daniel; Catlin, Daniel H.; Karpanty, Sarah M.; Ritter, Shannon J.; Fraser, James D. (Wiley, 2023-01)Population declines of disturbance-dependent species due to suppression of natural disturbances are realized across ecosystems. The piping plover (Charadrius melodus; plover), a disturbance-dependent and conservation-reliant shorebird that nests on sandy beaches and barrier islands on the Atlantic Coast, was listed under the United States Endangered Species Act in 1986. In 2012, Hurricane Sandy landed on Fire and Westhampton islands, barrier island nesting sites for plovers in New York, USA. Hurricane Sandy was a natural disturbance in this system, creating abundant nesting habitat. The number of chicks produced by a pair, or a population, is a direct measure of reproductive output, and gaining a better understanding of productivity and chick behavior following large-scale habitat creation may improve plover habitat management and potentially species persistence. We evaluated the effects of landscape features on habitat selection, behavior, and survival of plover broods using logistic regression, generalized linear mixed effects models, and survival models. Plover broods selected flatter sites with less dense vegetation than available at random. Chick foraging rates were highest in moist substrates and were lower in areas of higher nesting plover density. Chick survival was greater for broods that hatched earlier in the breeding season and increased as chicks aged. Generally, providing access to sites with flatter, moist substrates will likely result in higher quality brood rearing habitat on the landscape. Ultimately, vegetation removal and habitat management may be needed to reduce plover nesting density and ensure sufficient habitat, which may in turn improve plover chick survival. Moreover, sustaining natural landscape disturbances such as those resulting from storms, and not taking actions to prevent hurricane-created overwash, will allow these landscape features to persist.
- Residency, recruitment, and stopover duration of hatch-year Roseate Terns (Sterna dougallii) during the premigratory staging periodDavis, Kayla L.; Karpanty, Sarah M.; Spendelow, Jeffrey A.; Cohen, Jonathan B.; Althouse, Melissa A.; Parsons, Katharine C.; Luttazi, Cristin F.; Catlin, Daniel H.; Gibson, Daniel (Resilience Alliance, 2019)Seabird demography and spatial distribution outside of the breeding season are poorly understood, and migratory stopover and staging sites represent important energetic bottlenecks during the avian annual cycle. We quantified hatch-year Roseate Tern (Sterna dougallii) weekly residency, weekly recruitment rate into the staging population, and derived weekly staging population growth rate during two postbreeding, premigratory staging seasons (2014 and 2015) at Cape Cod National Seashore, Massachusetts, USA. We also estimated hatch-year tern stopover duration at Cape Cod staging grounds. Tern residency probability at Cape Cod National Seashore during 2014 and 2015 was nearly 1 during the first weeks of the season and decreased steadily over the last 4 weeks to ~0.5 in the final week of the study. Recruitment rates into the staging population, representing the weekly per capita change in hatchyear terns present during the staging season, indicated that most terns arrived on the staging grounds during the first weeks of the staging season (16 July to 19 August). We also identified differences in staging duration between birds from the two breeding regions. Hatch-year terns from the southernmost region spent less time staging at Cape Cod National Seashore than their northern counterparts in both 2014 and 2015. These differences may indicate alternative staging strategies for individuals originating in different regions and possibly reveal differences in resource conditions between these areas, for example, in the availability of ephemeral prey fish.
- Senescence and carryover effects of reproductive performance influence migration, condition, and breeding propensity in a small shorebirdWeithman, Chelsea E.; Gibson, Daniel; Hunt, Kelsi L.; Friedrich, Meryl J.; Fraser, James D.; Karpanty, Sarah M.; Catlin, Daniel H. (Wiley, 2017-11-15)Breeding propensity, the probability that an animal will attempt to breed each year, is perhaps the least understood demographic process influencing annual fecundity. Breeding propensity is ecologically complex, as associations among a variety of intrinsic and extrinsic factors may interact to affect an animal’s breeding decisions. Individuals that opt not to breed can be more difficult to detect than breeders, which can (1) lead to difficulty in estimation of breeding propensity, and (2) bias other demographic parameters. We studied the effects of sex, age, and population reproductive success on the survival and breeding propensity of a migratory shorebird, the piping plover (Charadrius melodus), nesting on the Missouri River. We used a robust design Barker model to estimate true survival and breeding propensity and found survival decreased as birds aged and did so more quickly for males than females. Monthly survival during the breeding season was lower than during migration or the nonbreeding season. Males were less likely to skip breeding (range: 1–17%) than females (range: 3–26%; βsex = −0.21, 95% CI: −0.38 to −0.21), and both sexes were less likely to return to the breeding grounds following a year of high reproductive success. Birds that returned in a year following relatively high population-wide reproductive output were in poorer condition than following a year with lower reproductive output. Younger adult birds and females were more likely to migrate from the breeding area earlier than older birds and males; however, all birds stayed on the breeding grounds longer when nest survival was low, presumably because of renesting attempts. Piping plovers used a variety of environmental and demographic cues to inform their reproduction, employing strategies that could maximize fitness on average. Our results support the “disposable soma” theory of aging and follow with predictions from life history theory, exhibiting the intimate connections among the core ecological concepts of senescence, carryover effects, and life history.