In chapter 1, my objective was to describe life history patterns of goldeneyes in relation to other sea duck species, which are typically described as long-lived, with delayed maturity, low and variable annual breeding probability, and invariant adult female survival. I used multistate capture-mark recapture models (Arnason 1972, 1973) in Program MARK (White and Burnham 1999) to estimate multiple demographic parameters, and used several explanatory variables to investigate the effects of climate on breeding and wintering areas, nesting density (as indexed by nest box occupancy), and individual variation (e.g., body condition) on my demographic parameters of interest. I detected substantial annual variation in adult survival. In contrast, breeding probability remained relatively high and invariant and was positively related to individual nest success the year prior. Nonbreeding individuals in year t were more likely to remain a nonbreeder, than attempt to breed in year t+1. Probability of recruitment into the breeding population conditioned on survival to two-years of age was age invariant and followed a negative linear trend over time .
In chapter 2, I used Pradel capture-mark-recapture models (Pradel 1996) to evaluate variation in per-capita recruitment (f) and population growth (λ), and determine the extent to which emigration and immigration may influence study area population dynamics. I detected significant differences in demographic patterns among two groups within my study population: (1) in-situ (IS) individuals that were marked as ducklings on the study area and later encountered as breeding adults; and (2) unknown recruitment origin (UN) individuals that were initially encountered as adults. In-situ per-capita recruitment was negatively related to the proportion of boxes occupied by goldeneyes in the year prior to recruitment, whereas recruitment in the unknown group was positively related to the proportion of boxes occupied. In the year prior to recruitment, yearlings typically prospect for potential nest sites (Eadie and Gauthier 1985), therefore, these results suggest that conditions during the prospecting year may facilitate density-dependent dispersal.
The demographic patterns I detected in goldeneyes are most consistent with a bet-hedging life history strategy (Sather et al. 1996), rather than a survivor species strategy, as observed in other sea duck species (Goudie et al. 1994). Bet-hedging species are thought to persist in high-quality breeding habitat that enables annual breeding attempts, contrasted with survivor species that breed in lower quality habitat that constrains annual breeding opportunities (Sather et al. 1996). As such, the importance of suitable nest sites to goldeneye demography is a recurring theme within my thesis research. High probability of breeding at the earliest age possible likely reflects both the necessity of obtaining a nest site, and the need to accumulate as many breeding attempts as possible over a lifetime, as expected of bet-hedging species— females that nest in the same nest site multiple years generally have earlier nest initiation dates and higher nest success than females that change nest sites (Dow and Fredga 1983). Furthermore, the negative relationship between in-situ per-capita recruitment and conspecific nesting density I detected, suggests that under certain conditions, a paucity of available nest sites may inhibit local recruitment patterns and mediate natal dispersal.
The contrast in life history patterns in goldeneyes and other sea ducks may be a contributing factor to observed differences in current population trajectories, therefore, understanding variation in life history strategies within the sea duck group should be of fundamental interest to managers. Furthermore, I detected substantial evidence for both emigration and immigration in our study area, which suggests that nest box populations may be porous, despite assertions of perceived benefits to breeding of natal philopatry (Dow and Fredga 1983). Finally, a lack of demographic parameter estimates for age and sex classes throughout the goldeneye’s range has precluded the construction of a population model (Sea Duck Joint Venture 2008). The estimates presented here are among the first for goldeneyes within Alaska (Schmidt et al. 2006) and will contribute to a better understanding of goldeneyes throughout their North American range. (Abstract shortened by UMI.)
|Advisor:||Sedinger, James S.|
|Commitee:||Forister, Mattew L., Matocq, Marjorie M.|
|School:||University of Nevada, Reno|
|Department:||Environmental and Natural Resource Sciences|
|School Location:||United States -- Nevada|
|Source:||MAI 51/04M(E), Masters Abstracts International|
|Subjects:||Wildlife Conservation, Wildlife Management, Ecology|
|Keywords:||Bucephala, Life history, Nest box, Population dynamics, Sea ducks, Waterfowl|
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