Evaluation of a reproductive index to estimate dickcissel reproductive success

James W. Rivers, Donald P. Althoff, Philip S. Gipson, Jeffrey S. Pontius

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

Intensive monitoring of bird nests to measure reproductive success is time-consuming and may influence the fate of nests. Reproductive indices that do not require searching for and visiting nests may be reasonable alternatives to nest monitoring if they provide results similar to nest-searching efforts. We evaluated the reproductive index of Vickery et al. (1992) for estimating reproductive success of the dickcissel (Spiza americana) in northeast Kansas, USA. We used nest searching and Vickery et al.'s (1992) reproductive index to compare reproductive success on 20 plots (200 × 200 m). Daily nest survival (DNS) rates averaged 0.911 (SE=0.011, n=72 nests), and brown-headed cowbirds (Molothrus ater) accounted for 21% of all nest failures. Surveyors underestimated reproductive index ranks when compared to nest-searching efforts and were inaccurate in their assignment of reproductive success. In particular, surveyors reported successful nests on 3 study plots that fledged no young, probably because young dickcissels moved onto plots after fledging from their natal territories. Our results indicate that the reproductive index of Vickery et al. (1992) may be inappropriate for wary species or those heavily parasitized by brood parasites. We suggest that before relying on the index alone, investigators should use pilot trials to determine whether results from this index are concordant with results from intensive nest-searching efforts for species of interest.

Original languageEnglish
Pages (from-to)136-143
Number of pages8
JournalJournal of Wildlife Management
Volume67
Issue number1
DOIs
StatePublished - Jan 2003

Keywords

  • Cowbird parasitism
  • Dickcissel
  • Kansas
  • Productivity
  • Reproductive index
  • Reproductive success
  • Spiza americana

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