• Login
    View Item 
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • Biological Sciences
    • View Item
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • Biological Sciences
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of Scholarworks@UACommunitiesPublication DateAuthorsTitlesSubjectsTypeThis CollectionPublication DateAuthorsTitlesSubjectsType

    My Account

    Login

    First Time Submitters, Register Here

    Register

    Statistics

    Display statistics

    Contrasting diet, growth, and energy provisioning in loons breeding sympatrically in the Arctic

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Rizzolo_D_2017.pdf
    Size:
    8.281Mb
    Format:
    PDF
    Download
    Author
    Rizzolo, Daniel J.
    Chair
    Lindberg, Mark
    Committee
    Schmutz, Joel
    Springer, Alan
    Hundertmark, Kris
    Metadata
    Show full item record
    URI
    http://hdl.handle.net/11122/7635
    Abstract
    Red- throated (Gavia stellata) and Pacific (G. pacifica) loons breed throughout Arctic Alaska, often on adjacent lakes. Despite having similar life histories and distributions, these species have contrasting population trends in Alaska. Red-throated Loon populations have fluctuated dramatically over the past 3 decades, while the population trend of Pacific Loons has remained stable. These species-specific, population-level differences may be related to the foraging behaviors of breeding adults: Red-throated Loons feed on marine fishes using central place foraging behavior, while Pacific Loons feed primarily on freshwater prey captured from their breeding lakes. In this dissertation, I examined how differences in diet composition during the breeding season were associated with individual fitness parameters, namely adult body condition, chick growth performance, and breeding success. I used results from this research to address the hypothesis that interspecific differences in foraging behaviors contribute to the contrasting population dynamics of Pacific and Red-throated Loons breeding in Alaska. Using stable isotopes and fatty acid biotracers of diet, I found that the diet of breeding Pacific Loons was composed of a mix of freshwater and marine prey, and that variation in diet composition was related to the size of the breeding lake. Pacific Loons nesting on small lakes consumed more marine prey, suggesting that small lakes were not profitable foraging habitat, but their use for nesting was enabled by the close proximity of marine foraging habitat. In contrast, Red-throated Loons nested on very small lakes and ate a diversity of marine fishes. Despite differences in diet, both species had similar body condition during late-incubation, indicating that their diets met adult energy requirements, and adults maintained similar lipid reserves despite differences in foraging behavior. I found that Red-throated Loon chicks grew rapidly, yet were only 66% of adult body mass when they departed their natal lakes for the sea at fledging. This pattern of chick growth reduced the length of the postnatal period, and, consequently, the amount of time adults had to fly to marine habitat to capture fish for their chicks. Red-throated Loons provisioned their chicks with sufficient energy to support high growth rates. Other loon species which do not fly to the sea to capture fish for their chicks, like the Pacific Loon, likely do not face similar selection pressure for reduced parental energy investment through rapid chick growth. In Red-throated Loons, the total energy demands of chicks over the postnatal period were reduced at the expense of increased daily energy demands during the period of rapid growth. Given this pattern of chick growth, variation in the availability of high-energy content prey exerts a strong influence on breeding success. Pacific Loons provisioned their chicks mostly freshwater invertebrates with low-lipid content. Consequently, Pacific Loon brood provisioning rates were much higher than those of Red-throated Loons, which provisioned their chicks large-bodied marine fishes. Brood-rearing Pacific Loons commonly departed their breeding lakes for marine habitat, presumably to forage for themselves; however, parents rarely fed their chicks marine fishes, suggesting that central place foraging was not an energetically profitable provisioning behavior for larger-bodied Pacific Loons. Reproductive success over 3 years was higher in Red-throated Loons than Pacific Loons due to higher chick survival rates. Estimates of maximum energy provisioning rates for broods demonstrated that the provisioning rates and diet composition of Red-throated Loons could more easily meet peak brood energy requirements than the provisioning rates and diet composition of Pacific Loons. Thus, lower survival of Pacific Loon chicks was associated with lower maximum energy provisioning rates. The use of both freshwater and marine prey may insulate Pacific Loons from changes in either foraging habitat. Further, Arctic lakes provide a reliable source of invertebrate prey for chicks, but a diet of invertebrates may limit chick production rates because of their small size and low lipid content. Although meeting maximum brood energy requirement by provisioning freshwater invertebrates was difficult for Pacific Loons, particularly for adults rearing the maximum brood size of 2 chicks, chick production rates were sufficient to maintain a stable population trend. Red-throated Loons' specialization on marine prey strongly links their energy intake to the availability of marine fishes, which can vary suddenly and dramatically with ocean climate. Foraging conditions for Red-throated Loons in this study supported high chick growth rate and high chick production rates. Low chick growth rate and low chick production documented at other sites in Alaska indicate that Red-throated Loon breeding success is highly variable. Low chick production rates may contribute to Red-throated Loon population dynamics in Alaska if the availability of important forage fish species is low over multiple breeding seasons. Pacific Loons may be better suited than Red-throated Loons to adapt to the changing Arctic environment given the flexibility of their foraging behavior and diet. Because Pacific and Red-throated loon chicks in coastal tundra habitat rely on different types of prey, chick survival can function as a sensitive indicator of changes in lentic and marine habitats in the Arctic.
    Description
    Dissertation (Ph.D.) University of Alaska Fairbanks, 2017
    Date
    2017-05
    Type
    Dissertation
    Collections
    Biological Sciences

    entitlement

     
    ABOUT US|HELP|BROWSE|ADVANCED SEARCH

    The University of Alaska is an affirmative action/equal opportunity employer, educational institution and provider and prohibits illegal discrimination against any individual.

    Learn more about UA’s notice of nondiscrimination.

    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.