Welcome! See – Learn – Share. Our galleries document the variation of bald eagle plumage across the pre-definitive molt sequence (age), individuals, regions and seasons. In most cases, these variables aren’t known, so plumage and age classifications are approximate, based on plumage presentation and coloring of the beak, cere and iris. Sorting of the images is also approximate based upon Mark A. McCollough’s seminal 1989 paper, “Molting Sequence and Aging of Bald Eagles” which includes his descriptions and iconic sketches of known-age individuals. The variation in plumage tells a story of molt sequence over time. This page is dedicated to the Basic IV plumage class which begins at about 4½ years of age, marking the completion of the Prebasic IV molt. McCollough notes that some Bald Eagles in Basic IV exhibited definitive plumage, while others retained some pre-definitive characteristics. Please refer to the table below the gallery for key classification tips. A full plumage description is available in McCollough’s cited paper. Some individuals shown in this gallery may exhibit active molt. They are placed in the gallery that best matches their overall presentation based on McCollough’s 1989 plumage descriptions. Viewer input is welcome.
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Eagles Explored Bald Eagle head diagram
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This anatomical diagram of the Bald Eagle’s head highlights key feather regions and structural features referenced in McCollough’s 1989 plumage study. While McCollough sometimes used accessible terms like “cheek,” “forehead,” and “eye stripe” to describe variation across plumage stages, this illustration offers a more detailed map of the underlying anatomy—including the auriculars, malars, crown, and throat. By visualizing these regions, viewers can better understand how flecking, shading, and molt-phase traits appear in different plumage classes. The diagram serves as both a reference and an invitation: to look closer, ask questions, and engage with the archive as a living resource. (Illustration Credit: EaglesExplored.com CC-BY-NC 2.0)
🦅 Basic IV Plumage Identification Summary (4½ year) per Mark A. McCollough (1989). The following descriptions are based on McCollough’s observations of 135 Bald Eagles of known age. The observations were made in Maine and the Canadian Maritime Provinces. Plumage variation from these descriptions is possible, and rather likely based on factors such as season, region, molt status, diet, and more. This is a tool for approximation, not for confirmation. Some birds are undoubtedly in molt phase. An attempt has been made to place them in the gallery of the closest plumage classification. Please see note below gallery.
Note: Per McCollough (1989) Basic IV plumage includes both pre-definitive and definitive individuals. While some eagles show pure white heads and tails, others retain brown flecking around the eyes or on the forehead, and may resemble younger birds despite nearing adult plumage. Please refer to the sketch below if you are unfamiliar with parts of the eagle.
Feature
Basic IV Pre-definitive
Basic IV Definitive
Crown
White with brown flecking around the eye and on the forehead near the cere
Pure white
Nape
Not explicitly described; likely white or lightly flecked, consistent with crown
White
Auriculars
Variable; one bird had heavily flecked eye stripe, resembling Basic III
White; no distinct eye stripe
Chin/Throat
Not directly described; likely white or lightly flecked
White
Belly
Dark brown contour feathers with buffy-brown margins
Same as pre-definitive
Tail
Predominantly white rectrices lacking terminal brown stripe; key field mark vs. Basic III
Identical; white tail without terminal band
Beak
Yellow with light brown at base, extending forward as faint line from nares
Yellow; may retain faint brown line at base
Cere
Usually all yellow; some birds showed light brown at base
Yellow
Iris
Pale yellow
Pale yellow
Plumage Classification Notes: Bald Eagle images in this archive have been sorted according to plumage stages described by McCollough (1989). With over 300 images and countless individual variations, some classifications may be imperfect or open to interpretation, especially in cases of transitional molt or atypical feathering. Molt-phase birds are placed in galleries that best reflect their overall appearance, though some may straddle two plumage stages both before and after the molt. This project is a work in progress, and constructive input is always welcome. If you believe an image might better reflect a different plumage stage—or if you notice traits that suggest molt phase rather than a clean classification, then please let us know. We’ll do our best to annotate transitional birds in their captions and move them to better-fitting galleries when appropriate. To share your thoughts, just refer to the image ID (e.g., EaglesExplored_00017) and reach out through the contact link. Your insights help us refine the archive and deepen the conversation.
