The white-throated sparrow (Zonotrichia albicollis) is a medium-sized songbird native to North America. This sparrow is quite distinctive, with its namesake white throat, bright yellow lores (the area between the eye and bill), and boldly striped head. The white-throated sparrow shows an intriguing plumage dimorphism between males and females. While difficult to distinguish by plumage alone, attentive birders can tell male and female white-throated sparrows apart through subtle differences in their appearance.
Plumage Differences Between the Sexes
Male and female white-throated sparrows can be differentiated based on slight variations in their plumage and soft part colors:
Crown Stripes
The most obvious difference between male and female white-throated sparrows is in their crown stripes. Males have wider black stripes and thinner tan stripes on their crown compared to females. The wider black stripes give males a more boldly striped appearance on the head.
Loral Color
The lores (area between eye and bill) of male white-throated sparrows are a richer, more golden yellow color. Females tend to have more pale yellowish lores. However, this difference is quite subtle and hard to discern in the field.
Supercilium Color
The supercilium is the thin “eyebrow” stripe that extends backwards above the eye. Males tend to have brighter white supercilium stripes compared to females. However, like the loral differences, this can be a very subtle distinction.
Bill Color
Male white-throated sparrows generally have darker gray to blackish bills compared to females, which have more pinkish-gray bills with a paler lower mandible. However, bill color varies seasonally and this difference is often unreliable.
Plumage Brightness
The overall plumage coloration of males is typically brighter and bolder than females. The tan stripes, wing bars, and other markings tend to be more buffy on males. Meanwhile, females show more muted, grayish tones. This difference can be difficult to appreciate without having a male and female side by side.
Soft Part Colors
In addition to bill color differences, male white-throated sparrows generally show richer yellow loral and orbital ring coloration compared to females. However, the usefulness of soft part colors for sexing birds varies both geographically and seasonally, making these subtle distinctions unreliable.
Behavioral Differences Between the Sexes
In addition to subtle plumage differences, male and female white-throated sparrows exhibit slightly different behavior, especially during the breeding season:
Singing
As in many songbirds, singing in white-throated sparrows is primarily done by males. During the breeding season, males sing loudly and frequently to both attract mates and defend their territory. Females may sometimes sing, but their songs are generally lower pitched and less frequent than males.
Aggression
Males are generally more aggressive than females in defending their breeding territories against intruders. They are more likely to chase, peck, and engage in aerial fights compared to females when confronting territorial rivals.
Courting
Males take the lead in courtship, frequently displaying before females with ritualized bowing, wing flicks, and soft singing. Females play a more coy, choosy role in breeding behavior.
Parental Care
Among white-throated sparrows, only the females build the nests and incubate the eggs. Males assist by defending territories and bringing food once the young hatch. Both sexes feed and care for the chicks, though females often take the lead role.
Determining Sex in the Field
For attentive birders, white-throated sparrows can be sexed in the field through a combination of plumage, behavior, and voice:
Look for Plumage Cues
Examine the head pattern for wider, bolder black stripes in males. Also look for brighter white supercilium, richer yellow lores, and buffier plumage in males. Use caution as these differences can be subtle.
Pay Attention to Behavior
Watch for males singing frequently, engaging in aggressive displays, or courting behaviors. Females are more quiet, cryptic, and less territorial.
Listen for Song Differences
Male songs are louder, more frequent, and lower pitched. But be aware songs can vary regionally.
Use Seasonality as a Clue
Territorial and breeding behaviors are highest in spring and summer. Birds are harder to sex in winter when plumages are faded and behavior changes.
Consider Plumages in Tandem
Comparing male and female side-by-side makes subtle plumage differences stand out more. If possible, observe paired or grouped birds.
Avoid Over reliance on Any One Factor
No single factor is completely diagnostic. Use a combination of plumage, behavior, voice, and seasonality to accurately sex white-throated sparrows.
Why Do the Sexes Look Different?
The plumage differences between male and female white-throated sparrows likely evolved for a few key reasons:
Territory Defense
The bolder plumage of males, particularly the strongly striped head, is thought to signal dominance to rival males. This aids males in defending their breeding territories.
Mate Attraction
Brighter, bolder male plumage may also help attract females and demonstrate health and vitality as a potential mate. This could drive female preferences for more colorful males.
Camouflage
Duller female plumage may provide better camouflage while nesting, helping conceal the female and eggs from predators.
Sex Recognition
Subtle differences in plumage and soft parts may help males and females recognize each other’s sex, facilitating successful courtship and pairing.
Geographic Variation
Across the white-throated sparrow’s wide breeding range, scientists recognize over a dozen subspecies that vary subtly in size, proportions, and fine details of coloration. However, the overall dimorphism between sexes remains fairly consistent across subspecies. Some minor geographic differences include:
Western Birds
Western subspecies like Z. a. gambelii tend to be more brightly colored with bolder markings in both sexes compared to eastern birds.
Northern Birds
Far northern breeders like Z. a. griseonucha are larger in size and paler in coloration overall. Sexual dimorphism may be reduced due to shorter breeding seasons.
Eastern Birds
Nominate Z. a. albicollis and similar eastern subspecies show the “classic” subtly dimorphic plumage features between sexes.
Southern Birds
Southern subspecies like Z. a. floridana average smaller in size and have softer, more blended plumage markings. But basic sexual dimorphism patterns still hold.
Conclusion
While male and female white-throated sparrows can be tricky to distinguish by plumage alone, their differences become clearer when factoring in behavior, voice, seasonality, and geography. Understanding subtle variations in appearance helps birders appreciate the beauty of avian diversity. With practice, the sexes can be reliably told apart through a thoughtful combination of field observations.
