Bird Plumage: Patterns & Functions

bird plumage
Many-colored Rush-Tyrant (Tachuris rubrigastra)

Bird Plumage

Bird plumages are composed of patterned feathers and pigments that produce remarkable effects on a bird’s appearance. Bright yellow, green, and blues combine with bold plumage color patterns as in the Many-colored Rush-Tyrant of South America.

However, at the other extreme are drab gray olive and brownish birds such as the many shorebirds and tyrant flycatchers. Bold or subdued plumage color patterns are the result of birds’ adaptation to habitats and species behavior. Whether a plumage pattern has a concealing or signaling purpose, birds use them throughout their life cycle.

Broad Classification of Bird Plumages

The nearly 10,000 known species of birds show a large variety of plumage patterns that can be broadly classified into mottled, scaled, barred, and spotted. Combinations of these broad plumages may appear in a single species in the upperparts and underparts of males, females, juveniles, and breeding and non-breeding plumages.

Studies on bird plumages have shown that a mottled pattern tends to function well in stationary camouflage. Plumages that regularly repeat a pattern, such as bars, scales, and spots, function in motion camouflage. Examples of the broad classification of bird plumage patterns in birds include:

mottled plumage

Mottled Plumage consists of feathers that are heterogeneously pigmented. It consists of feathers that are pigmented heterogeneously. This is the most common plumage pattern found on the upperparts more frequently than on the underparts in males and females, although least frequent in males. Common Pauraque (Nyctidromus albicollis)

scaled bird plumage

Scaled Plumage is a plumage pattern where pigmentation follows the feather’s edge, giving a scaled effect. Scaled plumages are less prevalent and are frequently biased towards the upper parts of adults and juveniles’ underparts. Female Blue-winged Teal (Anas discors).

barred bird plumage

Barred Plumage is made of alternating dark and light pigmentation transversal to the feather’s axis. Barred plumages are frequently found on the underparts of breeding adult males, but also in juveniles. Andean Flicker (Colaptes rupicola).

spotted bird plumage

Spotted Plumage is a pattern where one or more spots pigment each feather. Spotted plumages are also frequently found on the underparts of breeding males and females, adults and juveniles. Ocellated Tapaculo (Acropternis orthonyx).

 

Are birds self-aware of their plumages?

It is evident that birds choose where to forage, nest, and rest from a mosaic of many backgrounds or substrates available to them. However, it is not clear how birds choose places to suit their appearance. The evidence suggests the birds must have a sense of self-awareness of how they relate to their environment.

Ornithologists suggest that “It could be that somehow they ‘know’ what they look like and act accordingly.” Furthermore, birds may look at themselves, their eggs and the background and substrates and decide whether it’s a good place to forage for food, rest, and nest safely. Alternatively, birds may learn over time and multiple attempts about the kinds of situations they were not being detected by predators or their eggs escaped being eaten.

plumage patterns Rock Ptarmigans in three different plumages/Flickr/CC by 2.0

Plumage Pattern and Function
Concealment

The need for a plumage that protects from predation via camouflage and is optimal for sexual signals at the appropriate time and environment has resulted in the development of intricate plumages by birds. Animals display diverse coloration patterns that are thought to function in camouflage. To prevent detection by predators, birds match the background or break up (disrupt) their outline creating false edges.

Concealment is thought to be the main result of bird color patterns — not just of those that are cryptic but also of many that are brightly-colored and bold. The predominant visual aspect of many plumage colors is their similarity to the bird’s usual environment.

For example, ptarmigans are nearly pure white in the winter when they blend in with the snow. When patches of snow remain on the alpine meadows in spring, the birds are white and brown. In summer, when herbs and lichen cover the rocks, ptarmigans are finely barred black and brown.

Plumage and Posture

Some birds have taken camouflage a step further and adopt a posture that helps them match their background even more. The common potoo of Tropical America looks for dead branches or stumps that resemble its plumage to nest and day-roost. Its camouflage typically works well when the bird is relaxed. When a threat approaches, a potoo will adopt an upright position to line up its body outline with the perch and make it look like the bird, and the pole is one piece.

A more familiar example is the American Bittern. This bittern points its bill skyward, aligning its body contours and the stripes on its breast with the surrounding vertical marsh grasses.

plumage and postureCommon Potoo (left) and Americana Bittern (right) adopting a concealment posture.

Reduction of Contrast

Some bold color patterns reduce the contrast between a bird’s shape or outline and its background. The breast band of small plovers, a classic example of the disruptive pattern, visually separate the outline of its head from that of its body.

To be most effective, the contrast between elements of a bird’s plumage should be similar to the contrast between elements in the background. Thus, the color and sizes of patches or mottles on a bird’s plumage provide the most effective concealment when they match the color and size of the background elements.

Nightjars that spend the day on the forest floor’s leaf litter have mottles of sizes and tones that resemble the surrounding leaf litter. The boldly patterned plumages of tanagers and wood warblers blend with the small leaves, branches, reflections of light, and shadows found in their arboreal habitats.

Countershading and Concealment

The lower reflectivity of the upper parts of a bird interacts visually with the contrasting color of the underparts to disguise its outline, helping the bird to match its background. The value of contrast increases with the intensity of illumination from above. Open country birds such as plovers have strongly contrasting colors on their upperparts and underparts. White underparts work particularly well in this regard as a neutral reflector that takes on the nearest surface’s color tone, in this case, the ground.

White breasts and bellies on small plovers function more effectively for countershading than white breasts on large, long-legged shorebirds. The underparts of long-legged shorebirds are farther from the sand or muddy surfaces and have dark underparts rather than white.

concealment plumageSemipalmated Plover (left) and Black-bellied Plover (right) showing countershading and reverse countershading plumages.

Reverse Countershading

While countershading (dark upperparts and white underparts) helps concealment, reverse countershading (White upperparts and dark underpants) makes birds conspicuous. Breeding male Bobolinks (Dolichonyx oryzivorus)  and Black-bellied Plovers (Pluvialis squatarola) have striking reverse countershading. They need to be as noticeable as possible for a short period of time during the mating season when attracting females is the most important goal.

Plovers are also most conspicuous to predators, but they spend most of their time vigilant, continually scanning their surroundings for females and predators during the mating season. Food is abundant during this period, and they do not need to spend much time foraging for food. Once the mating season is over, bobolinks and plovers molt into plumages that make them inconspicuous in the habitat they favor in the wintering grounds. Most male ducks are dressed to impress during the breeding season. They molt into brown feathers during the non-breeding season.

Plumages that Enhance a Bird’s Outline

Contrary to concealment, some bird plumages are highly visible and do not typically match the natural background elements. Some birds, mostly males, developed conspicuous plumages to enhance their visibility. Scientists have asked whether brightly colored birds or those with plumages that do not match the background are more susceptible to predation and therefore are at a disadvantage.

Field experiments revealed that predators do not always attack bright-colored plumages. The unexpected result may be explained by the fact that brightly colored males often are more cautious and tend to spend more time in dense foliage than females and birds with less conspicuous plumages. Predators may not try to attack brightly colored birds because they may be more difficult to catch than their drab-colored counterparts.

The uniform coloration of the all-red Northern Cardinal (Cardinalis cardinalis) enhances its outline and renders it more conspicuous than a mixed color pattern. The crest probably enhances this effect. Contrasting edgings enhance striking signal patches such as the white crest of the Hooded Merganser (Lophodytes cucullatus).

The flamboyantly patterned plumage of a Torrent Duck (Merganetta armata) seems as if it would stick out in its habitat. However, finding one in the tumbling rapids of a stream when the bird is foraging can be challenging.

Final Remarks 

Learning the fundamentals of birds’ plumage patterns adds a new dimension to your enjoyment of birds and birding skills. The next time you see a nightjar on a day roost, you will know why the bird spends the day on such a particular spot.

Likewise, a whitish-gray Black-bellied Plover is on its way to the breeding grounds will molt into a plumage that defies camouflage rules and makes it highly visible.

If you happen to visit the Tropics, you will better understand why tanagers, honeycreepers, and toucanets are brightly colored. You will also understand why antbirds and flycatchers of the understory of the forest have such subdued plumages.

References:

  • Foster, Dr. Rory; Smith, Dr. Marty. “Bird Feather Types, Anatomy, Growth, Color, and Molting.” Veterinary & Aquatic Services Department. peteducation.com. Archived from the original on 9 February 2017. Retrieved 10 April 2017.
  • Frank B. Gill. 1990. Ornithology. W. H. Freeman and Company. New York.
  • Lindsay L. Farrell, Clemens Küpper, Terry Burke, and David B. Lank (December 2014). “Major Breeding Plumage Color Differences of Male Ruffs (Philomachuspugnax) Are Not Associated With Coding Sequence Variation in the MC1R Gene” (PDF). White Rose Research Online.
  • Marius Somveille, Kate L.A. Marshall, and Thanh-Lan Gluckman. A global analysis of bird plumage patterns reveals no association between habitat and camouflage. Academic Editor: Scott Edwards. PeerJ. 2016; 4: e2658. Published online 2016 Nov 9.

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