American Kestrels are small falcons found throughout North America. They are some of the most colorful raptors in North America, with a mix of different colors and patterns on their plumage. There are a few quick facts about the coloring of American Kestrels:
- Male American Kestrels tend to be more colorful than females.
- Males have blue-gray wings and a rusty red back with black spots and bars.
- Females have reddish-brown wings and back with black barring.
- Both sexes have two bold black vertical stripes on their face.
- American Kestrels have a whitish belly with black spots.
- Their tail has black bars with a white tip.
To understand the colorful plumage of American Kestrels, we need to look at the different parts of their body individually. In this article, we’ll review the colors and patterns on the head, wings, back, tail, and belly of these falcons. We’ll also discuss how males and females differ and why this species evolved such vibrant colors.
Head
The head is one of the most brightly colored parts of an American Kestrel. Both males and females have two thick, vertical black stripes that run down each side of their face through the eye. This bold facial pattern makes the kestrel one of the most recognizable raptors. It likely serves to camouflage the kestrel when hunting.
In males, the area between the black facial stripes is a blue-gray color. Females have a more tan-brown head between the black stripes. The crown of the head is chestnut brown in males and brownish-gray in females. American Kestrels do not have any other markings on the top or back of the head.
The bright facial patterns and difference between males and females are important for communication. The striking face allows kestrels to easily identify each other, especially during courtship and mating. The dimorphism suggests the colors help attract mates and demonstrate fitness.
Wings
The wings show some of the most obvious differences between male and female American Kestrels. Males have slate-blue gray wings and back. Females are more dull, with brownish-red wings and back. The wings have black spots and barring in both sexes, although this is more pronounced in females.
When perched, the kestrel’s wings are folded up, showing the coloration on the coverts (small feathers on the upper wing). The greater primary coverts form a reddish bar on the upper wing that is rusty in males and brownish in females. The lesser primary coverts are also slightly lighter and redder on males.
When in flight, the kestrel’s wings are open, revealing the flight feathers. Males have slate-blue flight feathers matching the blue-gray on the coverts. Females have lighter reddish flight feathers with barring. The pale base of the primaries contrasting with the dark wing tips forms a dark band across males’ wings that is less visible in females.
The differences in wing color results from melanin pigmentation. Males have less melanin, resulting in gray wings. Females have more melanin deposits, especially on the flight feathers, making the wings browner and darker. The brighter blue-gray wings in males likely help attract females and signal strength.
Back
The interscapulars and scapulars (feathers on the back and shoulder area) show very distinct color patterns that help distinguish males from females. Males have a rusty orange-red back that contrasts nicely with the slate-blue wings. Females are a deeper chocolate brown on the back.
In both sexes, the back feathers have black barring and streaking, although it is finer and denser in females. Males tend to have thicker black streaks down the feather shafts. The barring provides camouflage when the bird is perched with wings folded.
The reddish color comes from pigments called phaeomelanins. Males have higher levels, leading to the rusty orange back color. Females have lower levels, resulting in the darker brown back. This coloration is under strong sexual selection pressure and likely helps attract mates.
Tail
The tail of the American Kestrel is relatively long for a falcon. It is brownish-rusty colored with black bars running across the feather vanes in both sexes. Males tend to have lighter and brighter rusty bars compared to the dark bars of females. The tip of the tail is white with a wide subterminal black band.
When seen from below in flight, the tail shows a distinctive pattern. The white tail tip and wide subterminal band form an obvious white triangle or fan shape. This makes the kestrel highly identifiable in flight. The contrasting tail pattern likely helps with signaling and communication during aerial maneuvers.
Belly
The belly and underparts of American Kestrels are buffy white or pale cream in color. This region has heavy black spotting and streaks, especially towards the lower breast and flanks. The spotting provides camouflage when the kestrel is viewed from below. The black spots are slightly darker and denser in female kestrels compared to males.
The buffy white belly contrast nicely with the colorful back and wings. This pattern is common in falcons and helps break up their shape against the sky when seen from below by potential prey. The lighter belly probably also helps with signaling, especially during flight displays.
Differences Between Males and Females
The major differences in plumage coloration between male and female American Kestrels are summarized below:
| Body Region | Male Color | Female Color |
|---|---|---|
| Head | Blue-gray crown | Brownish-gray crown |
| Wings | Blue-gray | Reddish-brown |
| Back | Rusty orange with black spots | Chocolate brown with black barring |
| Tail | Rusty bars | Dark bars |
| Belly | Pale with dark streaks | Pale with dark streaks |
As seen above, males tend to have lighter and more brightly colored plumage on the head, wings, back, and tail. Females are a deeper chocolate brown color overall with more barring and streaking especially on the back, wings, and tail. However, both sexes share the same black and white facial pattern and streaked belly.
These sex-based differences are the result of sexual dimorphism and sexual selection. The more colorful plumage in males likely helps attract females and intimidate rival males. The drabber female coloration provides better camouflage while incubating eggs and brooding chicks in the nest.
Reasons for Colorful Plumage
American Kestrels display very vibrant and colorful plumage, especially in males. But why did this species evolve these colors? Here are some of the main evolutionary reasons for the kestrel’s ornamentation:
Camouflage
The main colors of the kestrel’s plumage provide camouflage while perched and hunting. The black vertical stripes help the kestrel blend into trees and branches. The black spotting and barring break up the bird’s outline. The brownish-red back matches with tree bark and dirt.
Communication
The high-contrast plumage pattern helps kestrels communicate visually. The bold face pattern allows easy recognition during courtship or territorial interactions. The bright white belly and tail stand out in flight, useful for signaling and interacting aerially.
Sexual Dimorphism
The sex differences in color help birds identify males and females of their own species. It also allows each sex to signal their fitness for breeding – males try to show off bright colors while females showcase camouflage.
Sexual Selection
Brighter plumage indicates health and good genes in males. Females evolved drabber plumage to blend into the nest background while incubating eggs and brooding young. Males likely evolved colorful plumage through female mate choice over successive generations.
Species Recognition
The unique patterning might help American Kestrels recognize others of their own species and prevent wasted courtship with other raptors. The colorful plumage facilitates identification between the kestrel and other falcons.
Communication
The high-contrast colors and patterns help kestrels communicate quickly during courtship displays, territorial interactions, and prey exchanges between mates. The coloration improves visual signals important for breeding and hunting coordination.
So in summary, the colorful plumage of American Kestrels serves many critical functions related to camouflage, signaling, sexual selection, species identification, and visual communication. The colors and patterns are essential adaptations for this falcon’s survival and reproduction.
Plumage Variations and Morphs
Although American Kestrels show fairly consistent color patterns, there are some regional and individual variations:
Regional Variations
West coast kestrels are slightly more colorful than east coast birds. West coast males have brighter rusty backs while east coast males are more subdued. West coast females also show more barring on the back and wings. The reasons for these geographical differences are not fully understood but may relate to habitat differences.
Melanistic Morph
A small percentage of kestrels display darker blackish-brown plumage instead of the usual colors. These melanistic morphs occur due to increased deposition of melanin pigments. Though rare, melanistic kestrels can be found across the species’ range.
Albinistic Morph
Very rarely, albino kestrels with white plumage and pink eyes and feet are observed. Albinism results from genetic mutations causing a lack of melanin throughout the body. Albino kestrels likely experience decreased survivorship in the wild due to greater visibility.
Leucistic Morph
Leucistic kestrels showing patchy loss of pigment also occur infrequently. Unlike albino birds, leucistic kestrels retain normal eye and foot color. Leucism only affects some plumage patches, leading to blotchy color patterns.
Moult and Color Changes
The colors and patterns of American Kestrels change somewhat across the year due to seasonal moulting:
Fledglings
Juvenile kestrels just fledging from the nest appear slightly duller than adults. Their feathers are newer and haven’t bleached or been exposed to as much sunlight. The wing and tail bands are also less distinct in young birds.
Fall & Winter
After moulting in late summer, kestrels are generally more brightly colored in the nonbreeding season. This may help with territorial defense and signaling after the stress of breeding. The fresh plumage is also important for visual communication and courtship displays.
Spring & Summer
By spring, the kestrel’s colors are fading and worn. The wing and tail feathers become frayed and bleached in both sexes. Males also show some grayish feather tips as their breeding plumage deteriorates. After breeding, the summer moult restores the bright colors.
Color Patterns in Other Falcon Species
The American Kestrel shows a typical falcon color pattern seen in related species worldwide. Here’s how some other falcons compare:
Common Kestrel
The Common Kestrel of Europe and Asia shows similar color patterns to the American Kestrel including rusty upperparts, grayish wings, black facial stripes and spotted underparts. As close relatives, their coloration has been conserved through evolution.
Merlin
The Merlin also has a grayish back and wings in males, reddish-brown in females. But Merlins lack the facial stripes, showing streaking instead. The tail bands are less distinct than in kestrels. Merlins have heavier streaking below.
Peregrine Falcon
The larger Peregrine Falcon exhibits more uniform gray-brown upperparts in both sexes compared to kestrels. They also lack the bold facial stripes. However, Peregrines do show similar belly streaking and bars on the tail.
Prairie Falcon
Prairie Falcons have brown upperparts with lighter flight feathers giving a hoary appearance. The facial pattern includes thick moustachial and cheek stripes. they exhibit fine barring on the belly and tail base unlike kestrels.
So falcons tend to share a basic pattern but differ in details like the facial patterning. The kestrel’s black facial stripes make it unique among North American falcons. The kestrel’s reddish back is also distinctive.
Conclusion
In conclusion, American Kestrels display a colorful mix of rusty reds, slate blues, and black and white patterns. Males tend to be more brightly colored on the head, wings, back, and tail compared to females. These vibrant colors serve functions like camouflage, signaling mates, communication, and species recognition. Regional and individual variation can occur, but most kestrels follow the same basic palette. Compared to related falcons, the kestrel’s black facial stripes make it visually distinctive. The striking and ornate colors of the American Kestrel reflect its active lifestyle and open habitats.
