Trivelpiece Wayne Z.

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Wayne Z.

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  • Article
    Spatial and isotopic niche partitioning during winter in chinstrap and Adélie penguins from the South Shetland Islands
    (Ecological Society of America, 2015-07-29) Hinke, Jefferson T. ; Polito, Michael J. ; Goebel, Michael E. ; Jarvis, Sharon ; Reiss, Christian S. ; Thorrold, Simon R. ; Trivelpiece, Wayne Z. ; Watters, George M.
    Closely related species with similar ecological requirements should exhibit segregation along spatial, temporal, or trophic niche axes to limit the degree of competitive overlap. For migratory marine organisms like seabirds, assessing such overlap during the non-breeding period is difficult because of long-distance dispersal to potentially diffuse foraging habitats. Miniaturization of geolocation devices and advances in stable isotope analysis (SIA), however, provide a robust toolset to quantitatively track the movements and foraging niches of wide ranging marine animals throughout much of their annual cycle. We used light-based geolocation tags and analyzed stable carbon and nitrogen isotopes from tail feathers to simultaneously characterize winter movements, habitat utilization, and overlap of spatial and isotopic niches of migratory chinstrap (Pygoscelis antarctica) and Adélie (P. adeliae) penguins during the austral winter of 2012. Chinstrap penguins exhibited a higher diversity of movements and occupied portions of the Southern Ocean from 138° W to 30° W within a narrow latitudinal band centered on 60° S. In contrast, all tracked Adélie penguins exhibited smaller-scale movements into the Weddell Sea and then generally along a counter-clockwise path as winter advanced. Inter-specific overlap during the non-breeding season was low except during the months immediately adjacent to the summer breeding season. Intra-specific overlap by chinstraps from adjacent breeding colonies was higher throughout the winter. Spatial segregation appears to be the primary mechanism to maintain inter- and intra-specific niche separation during the non-breeding season for chinstrap and Adélie penguins. Despite low spatial overlap, however, the data do suggest that a narrow pelagic corridor in the southern Scotia Sea hosted both chinstrap and Adélie penguins for most months of the year. Shared occupancy and similar isotopic signatures of the penguins in that region suggests that the potential for inter-specific competition persists during the winter months. Finally, we note that SIA was able to discriminate eastward versus westward migrations in penguins, suggesting that SIA of tail feathers may provide useful information on population-level distribution patterns for future studies.
  • Preprint
    Rethinking ‘normal’ : the role of stochasticity in the phenology of a synchronously breeding seabird
    ( 2017-12) Youngflesh, Casey ; Jenouvrier, Stephanie ; Hinke, Jefferson T. ; DuBois, Lauren ; St. Leger, Judy A. ; Trivelpiece, Wayne Z. ; Trivelpiece, Susan G. ; Lynch, Heather J.
    Phenological changes have been observed in a variety of systems over the past century. There is concern that, as a consequence, ecological interactions are becoming increasingly mismatched in time, with negative consequences for ecological function. Significant spatial heterogeneity (inter-site) and temporal variability (inter-annual) can make it difficult to separate intrinsic, extrinsic, and stochastic drivers of phenological variability. The goal of this study was to understand the timing and variability of breeding phenology of Adélie penguins under fixed environmental conditions, and to use those data to identify a ‘null model’ appropriate for disentangling the sources of variation in wild populations. Data on clutch initiation were collected from both wild and captive populations of Adélie penguins. Clutch initiation in the captive population was modeled as a function of year, individual, and age to better understand phenological patterns observed in the wild population. Captive populations displayed as much inter-annual variability in breeding phenology as wild populations, suggesting that variability in breeding phenology is the norm and thus may be an unreliable indicator of environmental forcing. The distribution of clutch initiation dates was found to be moderately asymmetric (right skewed) both in the wild and in captivity, consistent with the pattern expected under social facilitation. The role of stochasticity in phenological processes has heretofore been largely ignored. However, these results suggest that inter-annual variability in breeding phenology can arise independent of any environmental or demographic drivers and that synchronous breeding can enhance inherent stochasticity. This complicates efforts to relate phenological variation to environmental variability in the 53 wild. Accordingly, we must be careful to consider random forcing in phenological processes, lest we fit models to data dominated by random noise. This is particularly true for colonial species where breeding synchrony may outweigh each individual’s effort to time breeding with optimal environmental conditions. Our study highlights the importance of identifying appropriate null models for studying phenology.
  • Article
    Circumpolar analysis of the Adélie Penguin reveals the importance of environmental variability in phenological mismatch
    (John Wiley & Sons, 2017-03-20) Youngflesh, Casey ; Jenouvrier, Stephanie ; Li, Yun ; Ji, Rubio ; Ainley, David G. ; Ballard, Grant ; Barbraud, Christophe ; Delord, Karine ; Dugger, Katie M. ; Emmerson, Louise M. ; Fraser, William R. ; Hinke, Jefferson T. ; Lyver, Philip O'B. ; Olmastroni, Silvia ; Southwell, Colin J. ; Trivelpiece, Susan G. ; Trivelpiece, Wayne Z. ; Lynch, Heather J.
    Evidence of climate-change-driven shifts in plant and animal phenology have raised concerns that certain trophic interactions may be increasingly mismatched in time, resulting in declines in reproductive success. Given the constraints imposed by extreme seasonality at high latitudes and the rapid shifts in phenology seen in the Arctic, we would also expect Antarctic species to be highly vulnerable to climate-change-driven phenological mismatches with their environment. However, few studies have assessed the impacts of phenological change in Antarctica. Using the largest database of phytoplankton phenology, sea-ice phenology, and Adélie Penguin breeding phenology and breeding success assembled to date, we find that, while a temporal match between Penguin breeding phenology and optimal environmental conditions sets an upper limit on breeding success, only a weak relationship to the mean exists. Despite previous work suggesting that divergent trends in Adélie Penguin breeding phenology are apparent across the Antarctic continent, we find no such trends. Furthermore, we find no trend in the magnitude of phenological mismatch, suggesting that mismatch is driven by interannual variability in environmental conditions rather than climate-change-driven trends, as observed in other systems. We propose several criteria necessary for a species to experience a strong climate-change-driven phenological mismatch, of which several may be violated by this system.