. The Canadian field-naturalist. 1980 MENDALL: INTERGRADATION OF COMMON EIDERS 287. 1 TOTAL LENGTH 2 FRONTAL EXTENSION 3 NOSTRIL-EXTENSION 4 CULMEN MIDLINE Figure 1. Points of measurement of Common Eider bills. broad, rounded lobes of the latter are usually readily apparent. Frontal lobes oi sedentaria resemble those of dresseri but are smaller. Plumage coloration (pale gray or gray-buff) is also helpful in identifying seden- taria, but this character by itself is not always reliable (see Results). For subspecific bill descriptions, see especially Snyder (1941), Todd (1963), Godfrey (1966), an
. The Canadian field-naturalist. 1980 MENDALL: INTERGRADATION OF COMMON EIDERS 287. 1 TOTAL LENGTH 2 FRONTAL EXTENSION 3 NOSTRIL-EXTENSION 4 CULMEN MIDLINE Figure 1. Points of measurement of Common Eider bills. broad, rounded lobes of the latter are usually readily apparent. Frontal lobes oi sedentaria resemble those of dresseri but are smaller. Plumage coloration (pale gray or gray-buff) is also helpful in identifying seden- taria, but this character by itself is not always reliable (see Results). For subspecific bill descriptions, see especially Snyder (1941), Todd (1963), Godfrey (1966), and Palmer (1976). 1 identified intergrades as birds wherein the frontal lobes were either narrow (more so than in dresseri or sedentaria) and semi- rounded (or nearly square), or broad but conspicu- ously short. The Maine and Labrador data from live eiders served as the basis for comparison with preserved birds from other sources; University of Maine, Bow- doin College, Museum of Comparative Zoology, Carnegie Museum, United States National Museum, and Royal Ontario Museum. In addition, fresh spec- imens from southern Labrador and Newfoundland and preserved skins in the National Museum of Can- ada were examined and measured by Douglas Gilles- pie, former biologist of the Canadian Wildlife Service, who kindly sent me his records. Four bill measurements taken by D. Gillespie (per- sonal communication) were adapted for my studies (Figure 1) and defined as follows: 1) Total length: from tip of bill to posteriorend of the frontal lobe, 2) Frontal extension: from anterior end of feathering on top of middle of bill to posterior end of frontal lobe, 3) Nostril-extension: from posterior end of nasal opening to posterior end of frontal lobe, 4) Culmen midline ( = "exposed culmen" of standard measurements): from anterior end of feather- ing on top of middle of bill to the tip of the bill. Most authors have given only the midline length of the culmen in describing eider bills, alth
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