Aberrants

What's in a name? Nomenclature for colour aberrations in birds reviewed by Hein van Grouw acts as the basis for classifying the primary aberrant plumages shared on this page. We've done our best to sort the birds presented below, however there are likely mistakes. If you have any thoughts on how to improve this section, including classifications - please let us know! 

Some common species have many well documented examples of abnormal plumages. To help show how pigmentation can alter appearance, we've made a species-specific page for American Robin here! 

Leucism / Leucistic Birds

Patterned: 

Patchy:

White: 

Progressive Greying

Heritable:

Head & Bare Parts Specific? 

Albino

Brown / Aeumelanism 

Ino

Dilution

Pastel / Hypomelanism

Isabel / Aphaeomelanism 

Melanism / Hypermelanism

Extra Red: 

Extra Blue:

Extra Yellow: 

Diet-based Aberrants

Dilute Red

Staining

Brown

Gray

Yellow

Red

Pink 

Oiled

Further Aberrants 

Additional atypical individuals you may encounter include: 

Gynandromorph

A gynandromorph is an organism that contains both male and female characteristics and is most frequently recognized in birds that have strong sexual dimorphism.

Here's an example of a bi-lateral gynandromorphic (left side female, right side male) Evening Grosbeak from Ontario in Feb 2024. An article was linked which discusses a similar bird collected in Minnesota in Jan 1982. 

Further examples include: 

Spontaneous Sex Reversal

Sexually-dimorphic birds can sometimes go though spontaneous sex, which can cause females to exhibit male plumage, and vice versa (phenotypic feminisation or masculinisation). This may be most commonly encountered in the region among female Mallards with variable male plumage, but usually retaining a female-like bill pattern. Some examples include: 

Recognizing feminisation in males may be more challenging due to their most subtle plumage, raising confusion with possible hybrids (e.g., ABDUxMALL), or atypical molt such as atypically retained eclipse or juvenile (i.e., more female-like) feathers. Some examples include: 

Trauma Fault Barring

During molt a significant struggle such as hunger, illness or injury can affect the colour and structure of newly grown feathers. It is most recognizable in young birds, where all feathers are growing in at the same time, leading to bold/extensive "patterns". Older birds may only have isolated feathers affected due to the prolonged nature of feather replacement. Most examples involve gulls: