Applying the Declining Population Paradigm: Diagnosing Causes of Poor Reproduction in the Marbled Murrelet

Applying the Declining Population Paradigm: Diagnosing Causes of Poor Reproduction in the Marbled... Abstract: We identified six approaches to diagnosing causes of population declines and illustrate the use of the most general one (“multiple competing hypotheses”) to determine which of three candidate limiting factors—food availability, nesting site availability, and nest predation—were responsible for the exceptionally poor reproduction of Marbled Murrelets ( Brachyramphus marmoratus) in central California. We predicted how six attributes of murrelet demography, behavior, and physiology should be affected by the candidate limiting factors and tested predictions with field data collected over 2 years. The average proportion of breeders, as estimated with radiotelemetry, was low (0.31) and varied significantly between years: 0.11 in 2000 and 0.50 in 2001. Murrelets spent significantly more time foraging in 2000 than in 2001, suggesting that low food availability limited breeding in 2000. In 2001, 50% of radio‐marked murrelets nested and 67% of females were in breeding condition, suggesting that enough nest sites existed for much of the population to breed. However, rates of nest failure and nest predation were high (0.84 and 0.67–0.81, respectively) and few young were produced, even when a relatively high proportion of murrelets bred. Thus, we suggest that reproduction of Marbled Murrelets in central California is limited by food availability in some years and by nest predation in others, but apparently is not limited by availability of nesting sites. The multiple‐competing‐hypotheses approach provides a rigorous framework for identifying causes of population declines because it integrates multiple types of data sets and can incorporate elements of other commonly used approaches. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Conservation Biology Wiley

Applying the Declining Population Paradigm: Diagnosing Causes of Poor Reproduction in the Marbled Murrelet

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Publisher
Wiley
Copyright
Copyright © 2004 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0888-8892
eISSN
1523-1739
D.O.I.
10.1111/j.1523-1739.2004.00134.x
Publisher site
See Article on Publisher Site

Abstract

Abstract: We identified six approaches to diagnosing causes of population declines and illustrate the use of the most general one (“multiple competing hypotheses”) to determine which of three candidate limiting factors—food availability, nesting site availability, and nest predation—were responsible for the exceptionally poor reproduction of Marbled Murrelets ( Brachyramphus marmoratus) in central California. We predicted how six attributes of murrelet demography, behavior, and physiology should be affected by the candidate limiting factors and tested predictions with field data collected over 2 years. The average proportion of breeders, as estimated with radiotelemetry, was low (0.31) and varied significantly between years: 0.11 in 2000 and 0.50 in 2001. Murrelets spent significantly more time foraging in 2000 than in 2001, suggesting that low food availability limited breeding in 2000. In 2001, 50% of radio‐marked murrelets nested and 67% of females were in breeding condition, suggesting that enough nest sites existed for much of the population to breed. However, rates of nest failure and nest predation were high (0.84 and 0.67–0.81, respectively) and few young were produced, even when a relatively high proportion of murrelets bred. Thus, we suggest that reproduction of Marbled Murrelets in central California is limited by food availability in some years and by nest predation in others, but apparently is not limited by availability of nesting sites. The multiple‐competing‐hypotheses approach provides a rigorous framework for identifying causes of population declines because it integrates multiple types of data sets and can incorporate elements of other commonly used approaches.

Journal

Conservation BiologyWiley

Published: Aug 1, 2004

References

  • Are declines in North American insectivorous songbirds due to causes on the breeding range
    Böhning‐Gaese, Böhning‐Gaese; Taper, Taper; Brown, Brown
  • Experimental evidence of disrupted dispersal causing decline of an Australian passerine in fragmented habitat
    Cooper, Cooper; Walters, Walters
  • Which species traits predict population declines in experimental forest fragments
    Davies, Davies; Margules, Margules; Lawrence, Lawrence
  • Decline of a tropical montane amphibian fauna
    Lips, Lips
  • Diagnosing the cause of population changes: localized habitat change and the decline of the endangered St. Helena Wirebird
    McCulloch, McCulloch; Norris, Norris
  • Assessing limitations on population growth in two critically endangered Acacia taxa
    Yates, Yates; Broadhurst, Broadhurst

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