Morphometric features of Pacific and American Golden-Plovers withcomments on field identification.

We measured linear dimensions and evaluated identification criteria in Pacific and American Golden-Plovers(Pluvialis fulva and P. dominica) captured for banding. Most of the fulva sampled were wintering birds inHawaii, representative of the mid-Pacific flyway; additional fulva and all dominica were from breeding groundson the Seward Peninsula, Alaska. The sexes were monomorphic in dominica, and for all practical purposesin fulva as well. On average, fulva females had shorter head, bill, and tarsus lengths than males, but at a scaleof <1.0 mm for each dimension. Interspecific comparisons showed longest wings in dominica, longest billsand tarsi in fulva, and no difference in head lengths. Unpublished data provided by colleagues studying ploversin Siberia and Canada enabled us to compare our Alaska findings with breeding grounds elsewhere. Thereappears to be little, if any, variation in fulva wing lengths from the eastern end (Seward Peninsula) to nearthe western end of the breeding range (Taimyr Peninsula); however, other linear dimensions decreased fromeast to west. American Golden-Plovers breeding on the Seward Peninsula (western end of their range) hadshorter wings and tarsi, but longer bills than birds nesting at the opposite end of the range near Churchill,Manitoba. We found most field identification criteria described in the literature to be less than satisfactorybecause of variability and overlap between the two species. The only reliable characteristics were breedingplumage, number of primaries exposed beyond the longest tertials (2-3 in fulva, 4-5 in dominica), and primaryprojection past the end of the tail (estimated at 0-9 mm in fulva, 12-22 mm in dominica). In field situationsinvolving moulting birds and birds in non-breeding plumage, unequivocal species identification may beimpossible in some cases.

Johnson, O.W. & Johnson, P.M. 2004, Wader Study Group Bull. 103: 42-49