Great Dusky Swift vs Sick's Swift

In short

The Great Dusky Swift is larger and has a distinctive silvery head, while Sick's Swift is entirely brown and smaller. Great Dusky Swifts are often seen perched on rock faces, unlike the more aerial Sick's Swift.

Identification tips

• Look for the silvery head of the Great Dusky Swift as a key distinguishing feature.
• Observe behavior: Great Dusky Swifts may be seen perched, especially near waterfalls, while Sick's Swift is more aerial.
• Consider size: Great Dusky Swift is larger than Sick's Swift.

Size

Great Dusky Swift is fairly large compared to the smaller Sick's Swift.

Plumage

Great Dusky Swift is dark grayish brown with a silvery head, whereas Sick's Swift is entirely brown.

Behaviour

Great Dusky Swift is one of the few swifts that can be observed perched on rock faces, especially near waterfalls. Sick's Swift is more typically seen in flight.

Habitat

Great Dusky Swift is associated with rocky areas and waterfalls in eastern South America, notably Iguazu Falls. Sick's Swift is more widespread and not specifically tied to such habitats.