A Naturalist's Way with Words

18a    phase – noun – traditional (becoming archaic): a genetically determined variability of coloration among individuals of the same species without being attributable to, associated with, or determined by subspecies, race, or geographic population.

18b    morph – noun – (1) biology: a recognizable group, distinctive for some specific attribute of form or structure, within a species; (2) an individual of a recognizable group within a species known for having two or more groups distinguishable by form or structure; (3a) ornithology: a group or an individual within a species known to vary by form or structure; (3b) an individual bird distinctive for a specific permanent plumage color within a species known for various genetically determined plumage colors that do not vary by age, season, breeding condition, or geographic subspecies status.

dimorphic – adjective – descriptive of a species characterized by two groups distinguishable by some attribute of form or structure.

Example: Hawks and owls are sexually dimorphic because females are larger than males.

Example: Elk and Moose are sexually dimorphic species because males grow antlers and females do not.

polymorphic – adjective – descriptive of a species characterized by three or more groups distinguishable by some attribute of form or structure.

Example: The Canada Goose is a polymorphic species because the various subspecies are distinctive by size and body proportions.

Example: The Red Crossbill is a polymorphic species based on geographically predictable differences in beak sizes.

18c    chromer – noun – (Kevinism) an individual bearing a specific, permanent coloration that is one of two or more color variations typical of the species and not attributable to genetic mutation or defect or to age, season, breeding condition, geography, or subspecies status.

Example: That soaring bird is a dark chromer of Red-tailed Hawk.

A Hawk A Day Musings You Won't Find in a Field Guide

Northern Harrier — Circus cyaneus (Linnaeus)

    Considering its year round distribution, the Northern Harrier occupies more of North America than any other hawk. As a breeding species, it occurs throughout Alaska and eastward through Yukon and Northwest Territories sweeping southeastward thereby missing Nunavak and on eastward through the southern half of Quebec plus Newfoundland, and Nova Scotia. The southern boundary of its breeding range includes extreme northwestern Baja and coastal California but excludes southeastern California then closely follows the Utah-Arizona, Colorado-New Mexico, Kansas-Oklahoma borders before arcing northeastward through central Missouri then eastward into Delaware. Wintering birds move as far south as Venezuela. Northern Harriers have been found in the Aleutian Islands, Hawaii, Bahamas, Bermuda, and Greater Antilles.
    And this is just in North America!
    The Northern Harrier also occurs in Eurasia from Great Britain through Scandinavia eastward to the Pacific Coast including Sakhalin and Kurile Islands. During winter, these Asian Harriers move south into northern Africa, India, Myanmar, and southern China.

    Eurasian harriers had caught the attention of Eighteenth Century taxonomist Carolus Linnaeus. In 1758 he classified what is now called "Western Marsh Harrier" as Falco aeruginosus and "Montagu’s Harrier" as Falco pygargus. In 1766 he extended his work to include another Eurasian harrier, which he named Falco cyaneus, plus a North American harrier he named Falco hudsonius. To Linnaeus, if it looked like a hawk, it was a hawk; and all hawks were named "Falco."

    But harriers bear two features that quickly distinguish them: their faces and their flight. Their facial feathers are stiffer, less pliant, and more open, less fully meshed together, than other head feathers. These qualities form a facial disk typical of owls but unique among hawks. The facial disk helps the harriers hunt by sound. When hunting, harriers stroke the air in a languid cadence that keeps them aloft in a buoyant, floating manner of flight. They hunt low to the ground and work tall grasses, rushes, and sedges that other hawks ignore. Though vision is vital to their hunting, being able to hear prey – voices, chewing of food, rustlings of movement – can make the difference in eating or not eating.

    Acknowledging the distinctiveness of harriers, French naturalist, musician-composer, and politician, Bernard Germain Etienne de La Ville-sur-Illon, Compt de Lacepede, (basically, the Count of La Cepede, pronounced law-seh-ped), published a 1799 revision establishing the genus Circus just for them. The name is a New Latin adaptation of Greek kirkos, which meant "hawk" predating Aristotle. The species name cyaneus likewise originated in Greek: kyaneus meaning "dark blue," referring to the color of the male’s upper side. The genus has endured academic scrutiny for 210 years. Not so the species.
    During the 1700s and 1800s, taxonomic scholarship used every nuance of detail to establish a new species or genus. This academic temperament completely reversed by the 1930s. Well into the 1970s, consolidation was the new drumbeat of taxonomy. Variability came to be regarded as well within the limits of both the species and the genus concepts. This explains the changes in historical documentation of birds in Colorado.
    Wells Woodbridge Cooke (The Birds of Colorado, 1897), William Lutley Sclater (A History of the Birds of Colorado, 1912), and William Harry Bergtold (A Guide to the Birds of Colorado, 1928) all treated the harrier as Circus hudsonius and called it "Marsh Hawk," though Sclater hyphenated it as "Marsh-Hawk." (The issue of hyphenation in wildlife names in general and bird names in particular has evolved into a highly contentious issue with international implications. It is a story for another day.) Even Arthur Cleveland Bent, writing with a national scope (Life Histories of North American Birds of Prey, Part 1, 1937) cited Circus hudsonius and called it "Marsh Hawk." But when Alfred M. Bailey and Robert J. Niedrach published Birds of Colorado in 1965, North America’s Marsh Hawk had been reassigned as a subspecies, Circus cyaneus hudsonius. Only the American name remained to be tweaked.
    During the 1970s, the Check-list Committee of the American Ornithologists’ Union revised many bird names including "Marsh Hawk." Citing the bird’s frequent use of vegetation types other than marshes and invoking the desirability of aligning American names with international standards, the Check-list Committee abandoned "Marsh Hawk" in favor of "Northern Harrier," a senseless name with no "Southern Harrier," "Western Harrier," or "Eastern Harrier" for meaningful context: "northern" relevant to what? Nevertheless, all 14 species in the genus now go by the name "harrier." Both Latin and American names have been stable for the better part of four decades.

    Before Colorado was even a territory, Spencer Fullerton Baird included the Northern Harrier as part of the regional fauna in the ninth volume of the Pacific Railroad Survey (1858). As political boundaries formed and ornithological knowledge grew, the Northern Harrier took its place in Colorado’s avifauna.
    The Colorado Breeding Bird Atlas (1998) reported Northern Harriers as confirmed nesting in 15 latilongs, 20 counties, and 30 priority blocks. They were documented as probably nesting in 13 additional latilongs (unreported in the four partial Utah-border latilongs), 24 other counties, and 277 more priority blocks (of 1,760 total blocks). Some combination of factors affected the ability of field workers to confirm nesting.
    Northern Harrier colors differ between males and females, a condition widely but improperly called "sexual dimorphism" (see A Naturalist’s Way with Words, No. 18, to be posted Monday, February 16). Color differences also apply to differences between adult and immature birds. Young Harriers resemble females but differ enough the practiced eye can distinguish some portion of them. The similarity explains why females always appear to outnumber males. During migrations, males and females depart from and arrive at nesting grounds in pulses; watch and you will notice more males for awhile then more females.
    Harriers hunt as they migrate; but when intent on covering distance, they abandon their low, languid flying and ride thermals with other hawks and even gulls. Sometimes they spiral so high they become indiscernible specks before they leave the column of rising air and point their beaks to a far horizon.