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...an immature is not always a juvenile.
When talking about the age of a bird, the terms juvenile and immature are not interchangeable. Strictly speaking, one should only refer to a bird as a juvenile during the period when it wears its first complete set of feathers. Once a bird begins to replace feathers from the original set, it is no longer a juvenile. Depending on the extent of the first molt, the subsequent plumage aspects may be referred to as formative, first basic, or, in the case of species that require several years to reach a definitive adult plumage (i.e. gulls, terns, raptors), first-cycle.
For most species, the juvenile plumage is very short-lived. This is particularly true of songbirds. Many migrant songbirds hatch, grow a set of feathers, fledge, and then replace a majority of the original feather set before they ever leave the nesting grounds. For many such species, wing and tail feathers are the only elements of the juvenile plumage that are retained. It is simply too taxing on the bird to replace the longer, more durable flight and tail feathers so soon after growing the first set.
If you see a hatch-year thrush, warbler, or sparrow in July and then see that same bird in September, its appearance will have changed dramatically. Think of what an American Robin, Yellow-rumped Warbler or Dark-eyed Junco looks like when it is still being fed by an adult. By the first of October, you won't be seeing spots on the breast of the robin and the uniform streaking that marked the underparts of the warbler and the junco in July will be long gone.
The convenient thing about songbirds is that they tend to transition from juvenile plumage into an appearance that is very much like that of an adult, or at least a winter adult. Unless you understand how to use molt limits, visually separating many six-month old songbirds from their parents will be difficult. However, some species exhibit intermediate aspects that are distinctly different from both the juvenile and adult plumages. Birds in these plumages should not be referred to as juveniles. It is best and most accurate to describe such a bird as an immature or, perhaps, a sub-adult.
The term juvenile is most often misapplied to gulls, eagles and hawks. These groups of species take multiple years to acquire definitive adult plumages. Unlike the majority of songbirds, they will go through a series of distinctive plumage cycles all of which might be considered to be immature or sub-adult. Three-year and four-year, white-headed gulls offer probably the best known example of plumage cycles.
When white-headed gull species hatch, most grow a set of feathers that is mostly brown or gray-brown, rather uniform, and spangled or mottled. Sometime during the fall or early winter of their hatch year, they will undergo a preformative molt. The most obvious feather replacement will be on the back/mantle, head, and breast. The juvenile mantle feathers, which have dark dusky-brown or gray-brown centers and pale buffy or grayish edges, will be replaced by medium to pale gray feathers that are uniform in color with little if any interior pattern. By the end of the first winter, the heads of birds in this group will be extensively white with some darker streaks and smudges rather than almost entirely brown or gray-brown, as it was in juvenile plumage. Finally, the breast, which was densely streaked and looked mostly dark in juvenile plumage, will end up mostly white or off-white with more limited to non-existent streaking.
Despite the extensive alteration of the head, back, and body pattern, the wings will continue to look brown and mottled because the flight feathers have not been replaced during the preformative molt. Over the next 8-9 months, the first set of flight feathers will usually become worn and in some cases heavily sun-bleached. They will look old and tattered compared to the newer feathers acquired during the preformative molt.
Another groups of birds with distinctive juvenile plumages are shorebirds. Like gulls, they leave the breeding grounds in juvenile plumage and hold that first plumage aspect well into their first fall. Most species, particularly the long-distance migrants, will not start their preformative molt until they reach their wintering grounds.
When the initial North American field guides appeared, it was as if juvenile birds and their plumages did not exist. They were generally not illustrated and if they were the illustrations were not properly labeled and juvenile plumages were not discussed in the text. The first Peterson guides actually offered black-and-white illustrations of "fall" shorebirds. For the most part, these illustrations showed juvenile birds, but did not label them as such or account for the fact that one might also see alternate and basic-plumaged adults during Fall.
The 1st edition of the National Geographic Guide (now in its 6th edition) followed the lead of British and European field guides and became the first North American field guide to thoroughly illustrate, describe, and properly label the juvenile plumages for shorebirds and other species groups. The Sibley Guides raised the bar again by accurately showing the date range (in months) that one can expect to see each particular species in its juvenile plumage. Having access to illustrations or photos that show all the different aspects that a bird might present and understanding the time of year that they might look a certain way is vital when it comes to identifying most birds. As an example, if you see a bird in January that looks like the juvenile junco in the top image, you can be pretty comfortable in concluding that it's not a junco based on seasonality. In fact, Sibley indicates that birds of this appearance are only likely to be seen from May thru August.
As you can see from the three Western Sandpipers in the photos above, understanding how a bird's appearance varies with age and time of year is critical. If you saw the birds in the top image together on the same day–as I did– it would be easy to conclude that they were of different species. On occasion, a winter/non-breeding aspect Western (like the Baja bird) will show up with the southbound migrants (alternate-plumaged adults and juveniles) in August or September. Imagine a newer birder seeing a flock with birds representing all three plumages/aspects (it happens), and then being told by an experienced birder that all of the birds were of the same species.
If you intend to properly convey what you've seen to other birders, it helps to describe them in terminology that will be understood and terms that accurately represent the age-class that you observed. When describing a bird as a juvenile, it is important to understand what that label implies. It's perfectly okay to not know, or not be certain of a bird's age, as it's not always readily evident. While some might figure out that you mean immature or subadult when you call a bird a juvenile, others may be left searching for your discovery armed with a false notion of what they are seeking.
Finally, this subject cannot be discussed with out addressing the question of "juvenile" vs "juvenal," which causes confusion for some. Juvenile can serve as both a noun or an adjective, whereas juvenal is strictly an adjective, most often applied to describing the first plumage of a bird. In my view, whether you say juvenile plumage or juvenal plumage, most birders will understand what you are trying to say. However, among experts there has been some disagreement regarding the importance of using "juvenal" when describing the first plumage of a bird or in describing the molts that produce or alter that plumage. For example, a bird replacing its juvenal/juvenile feather set might be described as undergoing a post-juvenal molt. However, if you are talking about the bird itself, it can only be referred to as a juvenile. You might say, "I saw a juvenal-plumaged Song Sparrow, but it is not appropriate to say, "I saw an adult Song Sparrow feeding two juvenals." For a lively and thought-provoking discussion, I would recommend reading Joe Morlan's thoughts on this topic. He wrote a letter to the editor of Birding in response to a letter to the editor that Steve N.G. Howell had written in 2009, in which Howell endorsed the idea of abandoning the use of "juvenal." Morlan Letter to Birding I don't have a dog in this fight, but for the sake of simplicity I use "juvenile" as both the noun and the adjective when discussing birds.
Glossary of potentially unfamiliar terms:
Note: Most of these definitions below come directly from "Molt in North American Birds" (Howell 2010). This is the most recent, comprehensive treatment of this topic and is a great place to start if you are interested in learning more about molt sequences. I have chosen to use Howell's precise definitions in an effort to avoid introducing any further confusion to a topic that already creates confusion for many birders.
Alternate Plumage -- Any second plumage in a cycle in addition to–and which alternates with–basic plumage. Attained by a prealternate molt.
Aspect -- The overall appearance of a bird, which can be a composite of basic and alternate plumages. For example, larger white-headed gulls with clean white manifest a breeding aspect, even though they may not be breeding or may have started their prebasic molt. European Starlings in glossy, mostly unspotted plumage manifest a breeding aspect, even thought this is simply their worn basic plumage.
Basic Plumage-- The plumage attained by the prebasic molt (which is complete or nearly so)and presumed to be homologous in all birds.
Cycle -- A regularly repeated phenomenon, such as a plumage cycle. A basic plumage cycle extends from the start of one prebasic molt to the start of the next prebasic molt. The first plumage cycle extends from the acquisition of juvenile plumage to the start of the second prebasic molt.
Definitive Plumage -- A plumage whose aspect does not change with time.
Formative Plumage -- Any plumage present only in the first (that is, formative) year of life and lacking a counterpart in subsequent cycles. Attained by a preformative molt. Most conventional "first basic" plumages are formative plumages.
Four-year -- Refers to a group of large gulls that go through four complete plumage cycles before attaining a definitive adult plumage. May or may not happen within four calendar years.
Immature -- A general term for any nonadult plumage, including juvenile plumage.
Juvenal -- An adjective that is interchangeable with "juvenile" when describing the first plumage of a bird or the molts that produce or alter that plumage. Howell (2010) does not use this term, calling it a "psuedo-academic distinction that is unnecessary."
Juvenile -- A bird in juvenile plumage (see definition below)
Juvenile Plumage -- The first plumage of "true" or vaned (nondowny) feathers; often the plumage in which a bird fledges. Considered synonymous with "first basic plumage" in recent molt studies and attained by the prejuvenile (first prebasic) molt.
Molt Limits -- (called "Molt Contrast" by Howell) The point of contrast between two generations of feathers in a non-molting bird; for example, between the alternate and basic primaries of a tern.
Plumage -- There are two meaning for this word. In the Humphrey-Parkes System, refers simply to a generation of feathers attained by a molt, and the color of the feathers is not relevant. In everyday usage, refers to a bird's coat of feathers and may be termed "male plumage," "immature plumage," "breeding plumage," etc; thus the color and pattern of the feathers are relevant.
Preformative Molt --The molt by which formative plumage is attained. In traditional Humphrey-Parkes terminology this was called the first prebasic molt.
Three-year -- Refers to a group of medium-sized gulls that go through three complete plumage cycles before attaining a definitive adult plumage. May or may not happen within three calendar years.
The notions of suppressing and containing fire on the landscape are comparatively recent additions to the human experience. Prior to the invention of various machinery and retardant chemicals that gave us the ability to 'fight' fire, we were, like other creatures, at the mercy of it. Historically, fire was and continues to be more of a tool that was used by various cultures to transform the landscape.
Despite technological advances, periodic wildfire is still a major player in shaping the montane landscapes of western North America. For those of us who watch birds in this region, it is helpful to understand the effects of fire on the plants and animals that inhabit these environs. On 6 July 2013, Shawneen Finnegan, Ann Nightingale, Jim Danzenbaker and I spent most of the day exploring a recently burned area on the south flank of Mt. Adams in south-central Washington.
The expansive Cascade Creek Fire, which was started by lightning on 8 September 2012, blackened more than 20,000 acres before it was fully controlled more than a month later. The charred area extends from timberline in the Mt. Adams Wilderness area downslope into one of the few patches of mature ponderosa pine in Skamania County, Washington.
The county straddles the Cascade Range divide, with Mt. St. Helens on its western edge, Mt. Adams acting as the northeast corner stake and the Columbia River serving as its southern boundary. Aside from the narrow Wind River drainage, there are essentially no lowlands within its borders. Its upland forests are mostly comprised of wet slope trees. Firs, cedars, hemlocks, Douglas fir, bigleaf maple and red alder dominate most of the woodlands, with some lower elevation white oak along the Columbia River and in the southeast corner. Ponderosa pine, a dry slope specialist that hosts a variety of species not normally found west of the Cascade crest, is only found in a limited belt along the eastern edge of the county.
Following some excellent directions provided by Eric Bjorkman, we accessed the Cascade Creek burn by going north out of Trout Lake, Washington on Mt. Adams Rd. (Mt. Adams Recreation Hwy on some maps). After about a mile F.S. 23 Rd. (to Randle) peels off to the left. Stay to right on Mt. Adams Rd., and continue less than a mile before turning left onto F.S. 80 Road. After a few miles on F.S. 80 you'll come to another split, where staying right puts you onto F.S. 8040 Rd and going left puts you onto F.S. 8031 Road. We stayed on F.S. 8040, which continues on for several miles before terminating just below timberline at the trailhead for the South Climb Trail #183. This route ascends through several forest types and into the burn.
The first couple of miles of F.S. 8040 are flat, with a mix of mature ponderosa pine and Douglas fir. In the unburned stretches the understory is mostly brush with some wetter patches featuring dense vine maple and alders. In the lowest reaches of the fire zone, the blaze was mostly a ground fire that rarely 'crowned.' The absence of significant understory and the charred lower trunks of massive ponderosa pines and Douglas firs (still living) offer the only signs of the event. We birded this stretch both coming and going and it provided much of the species diversity that we encountered, including Williamson's Sapsucker, Red-breasted Sapsucker, and lots of other pine forest birds like Dusky Flycatcher, Chipping Sparrow, Cassin's Finch, Red Crossbill, and Pine Siskin. Both Cassin's and Warbling Vireos, along with MacGillivray's Warbler and to a lesser extent Nashville Warbler are pretty common here and we also had several Yell0w-rumped Warblers. A couple of Hermit Warblers were in the unburned area just as we started to climb out of the ponderosa pine.
About three miles in, the road (F.S. 8040) climbs rapidly into the heart of the burn area. The ponderosa pine thins out and a typical mid-slope (3000-5000' elev.) assortment of trees takes over. This part of the forest is/was mostly Douglas firs, true firs, hemlocks and we found a few small stands of aspens in wet draws. Large parcels are utterly devoid of living trees. This was a 'stand replacement' fire in the truest sense. Where the fire burned hottest there is still no ground cover. It's a dusty moonscape populated with blackened tree trunks and very few living things of any kind, including birds. In these areas even the bear grass–often about the only emerging vegetation during the first post-fire growing season–has yet to regenerate. The occasional birds that we pished up in such spots were generally limited to three species, Chipping Sparrow, Dark-eyed Junco, and Pine Siskin.
At the crest of the first lengthy uphill climb, you'll round a sharp curve and there is a steep drop-off on the east side of F.S. 8040. This marks the edge of the fully burned area. We had our first Black-backed Woodpecker of the day here and brief looks at a Red-naped Sapsucker. A family group of Gray Jays were in the live trees on the west side of the road.
Woodpeckers are the primary attraction when it comes to post-fire birding. As was the case with this visit, the first spring/summer season after a burn can be underwhelming, as it seems to take a year or two before the infestation of wood-boring insects takes hold. Without this vital food source, woodpeckers are sure to be scarce.
After visiting this fire site, I am anxious to go back in the next couple years. I suspect that the coming two or three breeding seasons will yield a woodpecker bonanza in this burn. We did find a few woodpeckers, including three Black-backeds, which along with American Three-toed are the two species Pacific Northwest birders most associate with burned areas.
Despite modest success with woodpeckers, we were not hearing "tappers" every time we got out of the car. When the expected onslaught is fully under way, the soft rapping of feeding Piciformes is likely to be a constant part of the soundscape throughout this burn. As we walked and drove through the blackened forest we were not seeing any woodpecker workings or freshly-excavated holes, nor did we find any active woodpecker nests. In fact, the only active cavity nest that we found upslope was that of a pair of Mountain Bluebirds. They were in one of the most severely burned areas on a plateau where there are broad pullouts on both sides of the road (where Mt. Adams first comes into clear view).
Continuing upslope towards timberline and the South Climb trailhead, the mix of trees transitions to hemlock, spruce, noble fir, and lodgepole pine dominant, with few trees that are more than 30-40 feet in height. Aside from bear grass, low matted sub-alpine shrubs, and various wildflowers, there isn't much in the way of understory.
Few bird species occupy this vegetation zone to begin with and our arrival coincided with the mid-afternoon nadir in avian activity. Besides a single Common Raven, plus a handful of Yellow-rumped Warblers, juncos, Chippings Sparrows, and Pine Siskins, we didn't see much.
Among these species, the only juveniles I saw were Yellow-rumped Warblers. It's hard to say if the Dark-eyed Juncos and Chipping Sparrows are even breeding in this fire-compromised habitat. Perhaps there isn't enough shrubby/grassy vegetation or food supply to support ground nesters. I saw what appeared to be adult pairs of juncos and little groups of adult Chipping Sparrows, none of which were carrying food or exhibiting agitated behavior that would suggest we were near a nest site.
For our group, most notably Jim and Shawneen, the scarcity of birds wasn't problematic, as there was an abundance of butterflies to occupy our attentions. Although my need for identifying butterfly species will likely never match my enthusiasm for birding, I am now able to recognize several species on sight and I've gradually learned to sort them by types, mostly by the osmosis that occurs when one is in the presence of those who know far more than I do. Butterflies make beautiful photo subjects and provide a welcomed diversion when a hot midsummer afternoon or a burnt landscape yield little bird activity.
While a burn is not the sort of place where one can expect to rack up a triple-digit daylist of bird species, exploring a fire-charred landscape will provide a look at how forests quickly regenerate after a major wildfire. Some might consider this forest to be dead, but wildfire is integral part of a forest's life-cycle and a closer look in the aftermath of a fire event offers insight into the resiliency of its inhabitants and just how quickly plants, insects, birds, and mammals return and thrive. Over the next couple of summers the Cascade Creek Burn should prove to be haven for woodpeckers and other cavity nesting, insectivorous birds. Butterflies are likely to abound as well. I know that I will we go back, hopefully many times. For those who might have the opportunity to do the same, the Google Map at the link below might be of use. It includes pin drops marking and describing some areas of potential interest.