27 Plumage and Molt Terminology Ron Pittaway A knowledge of plumages, molts winter, first summer and all subse­ and ageing is essential to the mod­ quent plumages until the non­ ern birder. The identification of a changing adult (definitive) plumage rare gull or shorebird often hinges is acquired. on knowing its correct plumage and stage of molt. Determining a bird's Juvenile or Juvenal: To avoid con­ plumage and molt is an identifica­ fusion, it is best to use these two tion challenge that will add new fun terms as having the same meaning. and skills to your birding. It is also It is the first covering of true con­ important to translate correctly tour feathers following the natal between different terminologies. down(s), or in certain species it suc­ This article (1) defines the key gen­ ceeds the naked nestling stage with­ eral terms of plumage and molt, out the natal down. Juvenile has a including the banding codes; (2) precise meaning; it is the first imma­ provides separate lists of birds that ture plumage. The juvenile plumage molt once and twice per year; and is worn briefly in most passerines, (3) compares a general terminology but much longer in loons, hawks, with that of Humphrey and Parkes gulls, shorebirds and others. In most (1959). The Humphrey and Parkes birds, the juvenile feathers appear terminology is recommended where looser, woollier, and differently there is a need to describe precisely a coloured and shaped than subse­ birdJs plumages and molts. quent stages. Some authors use juvenile, but not juvenal, as having General Terminology the same meaning as immature, just The following terms are used com­ adding to the confusion. Other monly by North American birders, authors use juvenile as a noun and but they are often used inconsistent­ juvenal as an adjective. For exam­ ly by authors and birders. Here, each ple, the juvenile is in its juvenal term is given an exact meaning in an plumage. However, both words can attempt to standardize the defini­ be used as nouns and adjectives. See tions. Plumage terms are defined also the definition of Juvenal in the first, followed by the terms for molt. section below under the Humphrey and Parkes terminology. PLUMAGES Immature: A general and collective First Year: This term applies to term that includes juvenile, first birds that molt once per year. It fol- VOLUME 18 NUMBER 1 28 lows the postjuvenile molt and is postbreeding molt. First summer retained until the first postbreeding plumage is adult-like in most molt. First year birds do not have species. Most passerines breed in separate first winter and first sum­ first summer plumage, but they are mer plumages. In many birds, first not adults because they retain juve­ year plumage is worn from late nile flight feathers. Many first sum­ summer or early fall to the follow­ mer birds are separable from adults ing summer. First year plumage is in the field by their duller or incom­ adult-like in many species, especial­ plete plumage colour and molt con­ ly passerines. Many breed in this trast. See the sections below under plumage. First year birds often can Feather Generations and Ageing. be separated from adults by First summer is sometimes called retained juvenile feathers. See the first breeding plumage. When you sections on Feather Generations are unsure if the bird is in first sum­ and Ageing below. First year is also mer or adult breeding plumage, just used as a general term to include call it breeding plumage to include birds in juvenile, first winter and both age classes. first summer plumages. Secondffhird Winter: Some birds First Winter: This is also called first that have two molts per year, such nonbreeding plumage. First winter as large gulls, have recognizable plumage follows the postjuvenile second and third winter plumages. molt in birds having two plumages a year. First winter plumage is retained Secondffhird Summer: Some birds until the first prebreeding molt. First that have two molts per year, such winter is adult-like in some species, as large gulls, have recognizable but many other species are separable second and third summer plumages. from adults in the field. See also the sections below under Feather SecondffhirdlFourth Year: Some Generations and Ageing. species have recognizable second, third and fourth year plumages. First Summer: This term does not refer to a bird in the summer of its Adult: Adult refers to a bird's hatching year, but to the next sum­ plumage, not to whether the bird is mer in its second calendar year. of breeding age. A bird is adult Remember this point to avoid con­ when it acquires its final or defini­ fusion. It refers to that plumage fol­ tive plumage that is then repeated lowing the first winter plumage in for life. Birds that molt once a year birds having two plumages a year. It have only one adult plumage; they is acquired by the first prebreeding are not divided into adult winter molt and retained until the first and adult breeding plumages. The ONTARIO BIRDS APRIL 2000 29 sexes are often alike in birds having plumages (e.g., loons). only one adult plumage and many are dull and cryptic in colour. Birds Subadult: This is generally used to that molt twice per year have two describe birds whose plumage is adult plumages: adult winter and nearly adult in appearance, but adult breeding. The sexes are often shows traces of immaturity. It is different, particularly the breeding most often used for birds that take plumage, in species having two several years to reach adult or adult plumages. Most passerines definitive plumage, such as eagles. breed in their second year before This term is confusing and is best they acquire adult plumage; they avoided. appear very adult-like but retain the juvenile flight feathers. Accipter Eclipse: This female-like plumage is hawks frequently breed in their sec­ held very briefly by ducks in sum­ ond year when they are in juvenile mer and early fall, and is most plumage. They are "adults" only in noticeable in the males. Eclipse is terms of reproduction, but not really the basic or winter plumage, plumage. Birds wearing any but is worn in summer by most retained immature plumage, even ducks, except the Ruddy Duck though breeding, are not adults. which wears eclipse to late winter. Note: adult used here is synony­ Most ducks acquire breeding mous with the term definitive of plumage in the fall, six or seven Humphrey and Parkes. months before other birds. This shift in the assumption of breeding Adult Winter: Birds that molt twice plumage appears related to per year have two adult plumages: courtship during fall and winter. adult winter and adult breeding. Adult winter plumage is also called Calendar Year Terminology: First adult nonbreeding plumage. calendar year refers to a bird up to the 31 December of its hatching Adult Breeding: Birds that molt year. Second calendar year goes twice per year have two adult from 1 January to 31 December, plumages: adult breeding and adult and so forth. Large birds, such as winter. Adult breeding plumage is eagles, are often aged using the cal­ also called adult summer plumage, endar year. and in the old literature it was known as adult nuptial plumage. In MOLTS adult birds that have two distinct Traditional molt terms are postjuve­ plumages, adult breeding and adult nal or postjuvenile, prebreeding and winter, there are a very few species postbreeding. These terms are where the sexes have identical defined below. Complete molts VOLUME 18 NUMBER 1 30 replace all the feathers, sometimes but in other species it starts much interrupted by a pause between peri­ earlier or later. In some species, the ods of molting. Anything less than a postbreeding molt takes place on complete molt is termed a partial the wintering grounds after migra­ molt. Most partial molts replace the tion. It produces a combination body feathers, but not the wings and winter and summer (yearly) tail. Some partial molts are limited, plumage in species that molt once usually replacing only a few head per year. In species that molt twice and/or body feathers. Depending on per year, it produces the winter the species, molts may be protracted plumage. During the postbreeding such as in hawks, or suspended dur­ molt, there is often a noticeable ing migration and continued (offset) change in the behaviour of many on the wintering grounds. birds, particularly in passerines; they become quiet and lethargic, Postjuvenile Molt: This begins soon avoiding long flights, and spending after fledging in most passerines more time resting and skulking. and somewhat later in many non­ Knowing differences in the timing passerines. It is a partial molt in of molts among similar species can most birds, producing first winter help identify a difficult species; for and first year plumages. A very few example, some Empidonax fly­ species have a complete postjuve­ catchers molt before, and others nile molt. These species usually after, fall migration. acquire adult plumage directly from the juvenile plumage; for example, Feather Generations: The feathers the Horned Lark becomes an adult acquired by a molt, whether partial at about three months of age. or complete, form a feather genera­ tion. Most first winter and first year Prebreeding Molt: Some species birds wear a combination of older have a molt in late winter or early juvenile and newer first winter feath­ spring that produces a separate, ers. First summer shorebirds often often more colourful, breeding or wear a combination of old juvenile, summer plumage. It is a partial molt somewhat younger first winter and in most species.