The short answer is no, female horned larks do not have horns. Only the males of this bird species grow horns. Let’s take a deeper look at why this sexually dimorphic trait evolved.
An Introduction to Horned Larks
The horned lark (Eremophila alpestris) is a small ground-dwelling songbird found across North America. They inhabit open countryside and prairies. Their diet consists mainly of seeds and insects.
Horned larks get their name from the small black feathers that grow on the top of the male’s head. These feathers can be raised or lowered, giving the appearance of tiny horns. The females lack these distinctive feathers and have a more nondescript brown plumage.
There are over 30 recognized subspecies of horned lark across their wide range. They show subtle variations in size, color and horn patterns while retaining the same general appearance. Of all these subspecies, only the males have the distinctive “horns” that give the birds their name.
Reasons for Sexual Dimorphism
Within many bird species, the males and females look different. The term for this is called sexual dimorphism. For instance, male peacocks have brightly colored tail feathers that females lack. Sexual dimorphism is driven by sexual selection, where certain traits give individuals an advantage in competing for mates.
Some key theories explain why male horned larks evolved showy head feathers while females did not:
- The horns help males establish a dominance hierarchy. More dominant males may get better breeding territories.
- Females are attracted to males with prominent horns. This trait signals “good genes” to potential mates.
- The horns intimidate rival males during conflicts over breeding rights.
- The horns provide camouflage for incubating fathers. Males participate in raising young.
In most bird species, males are the more visually ornamented sex. They have to compete to breed with females. Females then provide most or all parental care. The extra evolutionary pressure leads males to develop showy traits using sexual selection.
Physical Attributes of Horned Larks
Male Horned Lark Appearance
Let’s look closer at the male horned lark’s distinctive horns:
- They consist of 6-7 feather tufts approximately 1 cm long.
- When raised, they form pointed peaks shaped like miniature horns.
- Each tuft emerges from a single elongated feather follicle.
- The color is black on the tips fading to yellowish at the base.
- The horns sit above the eyes and beak.
- They are not made of keratin, bone or other hard tissue.
Aside from the horn feathers, males have mostly brown upperparts with some black streaks. Their underparts are pale brownish to white with dark streaking. Their white tail feathers are noticeable in flight.
Female Horned Lark Appearance
Female horned larks lack the horn feathers entirely. Their head is rounded without any ornamentation. Their overall plumage coloration is similar but paler than the males. Less streaking and bolder white throat patches help distinguish them.
Females closely resemble immature males before their horn feathers grow in during the first fall or winter after hatching. Adult female plumage remains locked in this juvenile form.
Growth and Display of Horns
The horns begin growing after males are a few months old. At first they are small nubs, becoming more elongated and prominent with the first molt.
Male horned larks can actively control their horns. When calm the feathers lay flattened. When displaying to other males or courting females they raise them to full height. This increases the visual impact.
The horns reach full size by one year of age. After this point they no longer molt or grow larger. As males age their horns gradually wear down from use. Very old males may have stubby rounded horns compared to fresh rigid points of young adults.
Seasonal Cycles
The size and condition of lark horns changes with seasonal hormonal cycles:
- They are largest in late winter and early spring when testosterone levels peak.
- Through summer and fall the horns become abraded from use.
- In the fall, rising testosterone causes shedding and regrowth before breeding.
- Cold weather exposure in winter can also wear the feathers down over time.
Behaviors Using the Horns
Male horned larks utilize their namesake horns in the following contexts:
Territory Defense
Males defend breeding territories against intruders. When confronting rivals they erect their horns to appear larger and more threatening. They may also sing territory songs with the horns raised. Higher quality habitat with more food and nest sites is worth fighting harder for.
Mate Attraction
Courting males visually showcase their horns to visiting females. A healthy, rigid set of horns demonstrates male fitness to potential mates. The female later uses horn quality in making her breeding selection. Males also produce special courtship songs directed at prospective mates.
Camouflage
Once eggs hatch, the male aids the female in caring for young. His cryptic plumage helps conceal incubating fathers from predators. The subdued horns likely provide additional camouflage when nesting on the ground.
Absence of Horns in Females
This brings us back to the original question: why don’t female horned larks have horns like the males? The lack of horns in females is consistent with conventional sexual selection. As the limited sex, females devote energy to producing and incubating eggs. The males must compete among themselves to breed with available females.
Any energy a female spends growing display feathers could otherwise go to reproduction. Minimal plumage better camouflages the nesting female as well. She leaves the brash signaling to the male whose reproductive success depends on it.
The differences between male and female horned larks are summarized below:
| Trait | Male | Female |
|---|---|---|
| Horns | Present | Absent |
| Plumage brightness | Brighter | Duller |
| Plumage patterning | More complex | Simpler |
| Singing | More frequent | Less frequent |
| Aggression | Higher | Lower |
| Parental care | Lower | Higher |
Conclusion
Only male horned larks possess the tiny feather horns that inspired the name of this widespread songbird species. These horns play an important role in territoriality, courtship, and likely camouflage. Females lack horns entirely and sport more cryptic brown plumage suited for nesting.
The horns are an excellent example of sexual selection driving showy traits in males of many bird species. Females receive no benefit from growing elaborate feathers that could otherwise go to reproducing. For the horned lark, horns remain solely part of the male’s biological toolkit.
