The standard-winged nightjar (Caprimulgus longipennis, formerly Macrodipteryx longipennis) is an insect-eating bird of sub-Saharan Africa whose breeding males grow one of the most bizarre ornaments in the bird world: a single elongated flight feather on each wing that extends far beyond the wingtip on a bare, ribbon-like shaft, ending in a broad, pennant-shaped vane. During courtship these feathers trail behind and above the bird in flight like a pair of tiny flags, creating a silhouette so strange that early European naturalists initially refused to believe the specimens were real. Outside of breeding season the males shed the extensions entirely, reverting to the same cryptic, mottled-brown plumage shared by females and most other nightjars.
What the “Standards” Actually Are
The ornament that gives the bird its name is not an extra appendage or a tail streamer. It is the second primary feather on each wing, massively modified. In breeding males this feather grows to roughly twice the body length. Most of the shaft is nearly bare, stripped of the normal interlocking barbs that make a flight feather aerodynamic. Only at the tip does a broad, oval vane appear, producing the pennant or flag effect. The result is a feather that contributes nothing to lift or thrust during normal flight but becomes visually spectacular during display.
Females and non-breeding males lack the elongated feathers entirely. Outside the breeding window, males molt the standards and grow ordinary-length second primaries in their place. This seasonal transformation is dramatic enough that a birdwatcher encountering the same individual in January and again in July could be forgiven for thinking they were looking at two different species.
Display Flight and How the Feathers Move
During courtship, males fly slow, circling routes above or near perched females, typically at dusk. The standards are lifted nearly vertically above the wing during these flights, and research suggests this upward positioning is achieved through a combination of muscular effort and aerodynamic forces acting on the feather’s unusual shape.1Wiley Online Library. Structural and functional adaptation to display in the Standard‐winged nightjar Macrodipteryx longipennis In other words, the bird actively raises the feathers, but the airflow over the pennant helps keep them aloft once they are up. The visual impression from the ground is of two pale, bobbing shapes trailing above a dark, fast-moving silhouette against the fading sky.
The display serves the same function as a peacock’s tail or a bird-of-paradise’s plume: females presumably choose mates based on the quality and vigor of the performance. Longer, more symmetrical standards likely signal a healthier male, though pinning down exactly what females evaluate has been difficult. Nightjars are notoriously hard to study in the field. They are active in low light, camouflaged on the ground during the day, and tend to breed in remote, open savanna and woodland. Most of what we know about the display comes from relatively brief observational studies rather than long-term, controlled experiments.
A Nightjar That Defies the Family Mold
At first glance the standard-winged nightjar shares the classic nightjar body plan: a wide, gaping mouth fringed with stiff bristles for catching insects on the wing; large eyes adapted for dim light; short legs; and soft, earth-toned plumage that blends into leaf litter and bare ground. It is a member of the family Caprimulgidae, which includes roughly 100 species spread across every continent except Antarctica. Most of these birds look remarkably similar to one another, so much so that molecular studies have overturned earlier classification schemes that grouped them by appearance.
Genetic work using cytochrome b and multi-gene datasets showed that the traditional genus Caprimulgus is not a natural group. Species placed in it were scattered across the family tree, grouped together largely because they all retained the same ancestral body shape suited to nocturnal, insect-hawking life.2PubMed. A molecular phylogeny of the nightjars (Aves: Caprimulgidae) suggests extensive conservation of primitive morphological traits across multiple lineages The standard-winged nightjar and its close relative, the pennant-winged nightjar, were historically placed in a separate genus, Macrodipteryx, precisely because their elongated feathers were so conspicuous. But molecular data revealed that they nest within an African-Eurasian clade of Caprimulgus species, and a broad taxonomic revision folded them back into Caprimulgus.3PubMed. A multi-gene estimate of phylogeny in the nightjars and nighthawks (Caprimulgidae) The irony is that the traits that once seemed to make them stand apart, the extravagant plumage ornaments, are probably products of sexual selection layered on top of a body plan that has barely changed across tens of millions of years of nightjar evolution.
Sharing Space with Other Nightjars
Across much of its West African range, the standard-winged nightjar lives alongside other nightjar species, particularly the long-tailed nightjar. A field study in The Gambia found that the two species coexist at the landscape level, showing up in the same broad habitat patches, but avoid each other at finer spatial scales of less than about 500 meters. The long-tailed nightjar was far more abundant in the study area, outnumbering standard-winged nightjars roughly nine to one. Density was sharply higher inside rice-field habitats, where both species found abundant insect prey drawn to the open, wet ground.4PubMed Central. Microhabitat Segregation of Co-Existing Nightjar Species in The Gambia
This kind of fine-scale habitat partitioning is common among closely related species that eat the same food. By roosting and foraging in slightly different microhabitats, the two nightjars reduce direct competition even where their ranges overlap. For the standard-winged nightjar, favored roosting spots tend to be open, stony, or laterite ground in dry savanna, woodland edges, and recently burned areas. The bird is an intra-African migrant, moving south into its breeding range during the wet season and retreating northward into the Sahel and semi-arid belt outside of breeding. Tracking these movements precisely has been difficult because the birds are so cryptic during the day.
Camouflage as a Survival Strategy
When not displaying, the standard-winged nightjar relies on the same defense strategy as virtually every other nightjar: it sits still and trusts its plumage to make it invisible. All nightjars nest on the ground, laying eggs directly on leaf litter, bare soil, or gravel with no constructed nest. Both the eggs and the sitting adult are exposed to visual predators, and the primary protection is the match between plumage pattern and background.
A study tracking nest survival in nightjars found that clutches survived at higher rates when the incubating adult’s plumage more closely matched its surroundings in both pattern and contrast. The appearance of the eggs themselves, by comparison, had no measurable effect on whether a nest was raided. Adults sat tight until a threat came within about two meters on average before flushing, reinforcing the idea that camouflage is the critical first line of defense and that it acts mainly through the adult’s appearance rather than the eggs’.5PubMed Central. Camouflage predicts survival in ground-nesting birds Observations of a related species, the fiery-necked nightjar, showed that brooding adults responded to approaching humans by pressing flat against the ground, sleeking their plumage, withdrawing their head level with the back, and closing their eyes to a narrow slit, remaining completely motionless until the threat passed.6Bulletin of the British Ornithologists’ Club. Fiery-necked Nightjar Caprimulgus pectoralis development and behaviour from hatching to fledging, including attendant parental care
For the standard-winged nightjar, there is an inherent tension between camouflage and display. The elongated feathers that make breeding males so conspicuous at dusk would be a liability during the day if they disrupted the bird’s cryptic outline on the ground. That the standards are raised only during active flight display and otherwise trail behind or fold alongside the body means the cost to daytime concealment may be modest. And the post-breeding molt eliminates the ornament entirely for the months when the bird is not trying to attract a mate.
Eyes Built for Twilight
Nightjars are crepuscular and nocturnal hunters, catching moths, beetles, and other flying insects in mid-air using their enormous gape. Doing this in near-darkness demands specialized eyes. Research on the visual system of caprimulgiform birds, the order that includes nightjars, potoos, and oilbirds, has revealed a retina packed with adaptations for low light. In the common pauraque, a New World relative, the rods responsible for dim-light vision have unusually long and thick outer segments, boosting each rod’s ability to capture photons. The rods are also distributed in patches across the retina, and the eye contains a tapetum, a reflective layer behind the retina that bounces light back through the photoreceptors for a second pass.7Brain, Behavior and Evolution. Retinal Morphology and Electrophysiology of Two Caprimulgiformes Birds: The Cave-Living and Nocturnal Oilbird (Steatornis caripensis), and the Crepuscularly and Nocturnally Foraging Common Pauraque (Nyctidromus albicollis) The tapetum is what gives nightjars their eerie, bright eyeshine when caught in a flashlight beam, a feature birders and researchers use to locate them at night.
Alongside the rods, pauraques retain a higher proportion of cone cells than a purely nocturnal animal would need. Cones are the photoreceptors used for color and detail in brighter conditions. This mix makes sense for a bird that is most active during the transitional light of dusk and dawn rather than the pitch dark of midnight. The standard-winged nightjar’s own retinal anatomy has not been studied in comparable detail, but the shared ecology and close evolutionary relationship strongly suggest a similar design. The bird is typically most active in the half-hour after sunset and before sunrise, the same twilight window when its display flights occur and insect activity peaks.
Why the Standard-Winged Nightjar Is Hard to Study
For such a visually arresting bird, remarkably little is known about many aspects of its biology. Basic questions like average clutch size, incubation period, chick growth rates, and annual survival remain poorly documented for this species specifically, even though closely related nightjars have been studied in more detail. Several features of the bird’s life conspire to make fieldwork difficult.
First, it is almost impossible to find during the day. A standard-winged nightjar roosting on bare ground among stones and dry leaves is functionally invisible unless you nearly step on it. Second, its breeding range spans a broad but politically complex swath of West and Central Africa, from Senegal east to Ethiopia and south to the Democratic Republic of the Congo, where funding and logistics for long-term bird monitoring are often limited. Third, nightjars in general are underrepresented in ornithological research compared to songbirds or raptors, partly because they are difficult to mist-net, hard to band reliably, and resistant to conventional survey techniques. Spotlight surveys along roads at night, counting eyeshine reflections, remain the most common census method. That approach works better for species that favor road edges and open ground than for those in denser cover.
The nine-to-one density ratio between long-tailed and standard-winged nightjars observed in The Gambia is one of the few published estimates of relative abundance, and it comes from a single study site.8PubMed Central. Microhabitat Segregation of Co-Existing Nightjar Species in The Gambia Whether that ratio holds elsewhere in the range is unknown. BirdLife International currently lists the species as Least Concern, meaning it is not considered at immediate risk of significant population decline, but the confidence behind that assessment is limited by sparse monitoring data.
The Pennant-Winged Nightjar Comparison
The standard-winged nightjar’s closest living relative, the pennant-winged nightjar (Caprimulgus vexillarius), has converged on a strikingly similar display strategy from a slightly different angle. In the pennant-winged species, breeding males also grow enormously elongated flight feathers, but in their case the feather retains a continuous vane along its full length rather than having a bare shaft capped by a pennant. The result is a long, streamer-like plume that trails behind the bird in flight, rippling and fluttering. Both species shed these feathers after breeding. Both are intra-African migrants. And both were historically placed together in Macrodipteryx before being folded back into the broader Caprimulgus clade.
Why two closely related species evolved such similar but structurally distinct ornamental feathers is an open question. The most likely explanation involves sexual selection acting on slightly different starting variation in feather structure. The two species breed in different parts of Africa (the pennant-winged nightjar is concentrated in southern and eastern Africa), so they are not in direct competition for mates, and the ornaments may have evolved independently after the lineages split. Alternatively, a shared ancestor may already have had elongated second primaries, and each descendant species refined the trait differently. Without fossil evidence of ancestral feather structure, distinguishing between these scenarios is mostly speculative.
Nightjars and the “Goatsucker” Myth
The family Caprimulgidae takes its name from the Latin caprimulgus, literally “goat-milker.” The myth dates back at least to Aristotle and Pliny the Elder, who wrote that nightjars flew into barns at night to suckle from goats, causing the animals to go blind and their udders to dry up. The real explanation is more mundane: nightjars forage for insects around livestock, and their habit of flying close to resting goats and cattle at dusk, snapping up the moths and beetles attracted to the animals, was misinterpreted as something more sinister.
The standard-winged nightjar’s appearance in flight, with its trailing pennants, probably did little to dispel superstition in areas where it was encountered. Across West Africa, nightjars have accumulated a range of folk associations, some neutral and some ominous, connected to their nocturnal habits and ghostly calls. The birds’ cryptic daytime behavior and sudden, silent appearance at dusk lend them an air of mystery that persists even among people who are well-acquainted with local wildlife. In parts of northern Ghana and Burkina Faso, encountering a nightjar at certain times is still considered a portent, though the specifics vary by community and ethnic group.
Molt, Timing, and the Cost of Being Flashy
Growing and maintaining the standards is not free. The elongated feathers represent a significant investment of keratin and metabolic energy, produced during a period when the male also needs to be in peak physical condition for display flights and territorial defense. The fact that males discard the feathers soon after breeding suggests the ornament carries real costs: increased drag during normal flight, greater conspicuousness to predators, and the energetic expense of growing such large feathers in the first place.
The timing of the molt aligns with the species’ migration cycle. Males grow the standards as they arrive on the breeding grounds during the wet season, display for several weeks, and begin shedding them as breeding activity winds down. By the time the bird migrates back to its dry-season range in the Sahel, the standards are gone and the male is once again indistinguishable from a female at a distance. This seasonal toggling between conspicuous and cryptic is more dramatic than in most birds with sexual dimorphism, where differences in plumage persist year-round. It hints at particularly strong selection pressure from both directions: strong enough sexual selection to produce an absurdly elongated feather, and strong enough natural selection to ensure the bird does not carry that feather a day longer than necessary.