Estimation of species identification error

Implications for raptor migration counts and trend estimation

Joshua M. Hull, Allen M. Fish, John J. Keane, Sylvia R. Mori, Benjamin Sacks, Angus C. Hull

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

One of the primary assumptions associated with many wildlife and population trend studies is that target species are correctly identified. This assumption may not always be valid, particularly for species similar in appearance to co-occurring species. We examined size overlap and identification error rates among Cooper's (Accipiter cooperii) and sharp-shinned (A. striatus) hawks specific to a raptor migration count station along the Pacific Coast of North America. Illustrating the difficulty of distinguishing between these 2 species, we found overlap in 7 metrics among speciessex groups and in 2 metrics between species, and a principal components analysis revealed a continuum of discrete clusters for each speciessex combination in morphospace. Among juvenile hawks (n 940), we found the greatest misidentification rate for male Cooper's hawks (23 of the 156 males were identified as sharp-shinned), lesser error rates for female Cooper's (8, n 339) and female sharp-shinned (6, n 246), and the lowest misidentification rate for male sharp-shinned hawks (0, n 199). We observed a similar pattern of misidentification among adult hawks (n 48). We attempted to use conditional probabilities (identification rates) from calibration data to calculate the true number of adult and juvenile Cooper's hawks and sharp-shinned hawks. Discrepancies between total number of observed accipiters and estimated number using calibration data suggest that daily observer misclassification rates are higher than misclassification rates estimated from calibration data and prevent correction of the raw data. Our results illustrate the importance of testing for and quantifying observer error in species identification in wildlife census and population trend studies particularly when target species may be easily confused with other nontarget species.

Original languageEnglish (US)
Pages (from-to)1326-1334
Number of pages9
JournalJournal of Wildlife Management
Volume74
Issue number6
DOIs
StatePublished - Aug 1 2010

Fingerprint

raptor
hawks
birds of prey
Accipiter
calibration
wildlife
nontarget organisms
species identification
trend
rate
principal component analysis
census
coasts
coast

Keywords

  • Accipiter cooperii
  • Accipiter striatus
  • California
  • Cooper's hawk
  • error
  • hawk count
  • identification
  • migration
  • monitoring
  • sharp-shinned hawk

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Nature and Landscape Conservation

Cite this

Estimation of species identification error : Implications for raptor migration counts and trend estimation. / Hull, Joshua M.; Fish, Allen M.; Keane, John J.; Mori, Sylvia R.; Sacks, Benjamin; Hull, Angus C.

In: Journal of Wildlife Management, Vol. 74, No. 6, 01.08.2010, p. 1326-1334.

Research output: Contribution to journalArticle

Hull, Joshua M. ; Fish, Allen M. ; Keane, John J. ; Mori, Sylvia R. ; Sacks, Benjamin ; Hull, Angus C. / Estimation of species identification error : Implications for raptor migration counts and trend estimation. In: Journal of Wildlife Management. 2010 ; Vol. 74, No. 6. pp. 1326-1334.
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