Pacific swift (Apus pacificus)

Pacific Swift – Aerial Acrobat and Flying Summer Guest

As an acrobatic summer visitor to Japan, the Pacific Swift (Apus pacificus) spends nearly its entire life in the air, catching insects with astonishing agility.

Table of Contents

Introduction

In Japan’s summer skies, the Pacific Swift is a constant companion. It darts across the air like a missile, hunting insects with jaw-dropping precision. This migratory bird arrives each spring from the south and fills the skies with speed, motion, and grace. It only touches the ground to breed.

Appearance – Built for the Skies

The Pacific Swift’s body is designed for perpetual flight. Measuring 18–20 cm in length with a wingspan of 40–45 cm, and weighing only 35–50 grams, it’s a true lightweight of the air.

Distinctive features:

• Dark brown plumage with a striking pale rump
• Light-colored throat
• Long, narrow wings bent like scythes
• Deeply forked tail
• Tiny, nearly invisible beak with a wide gape – ideal for catching insects mid-air

Habitat – High-Flying Cliff Dweller

In Japan, you can see Pacific Swifts from spring to late summer, mostly on Honshū, Shikoku, Kyūshū, and sometimes Hokkaidō. Their preferred habitats include:

• Steep mountain slopes
• Coastal cliffs
• Tall structures like towers and multi-story buildings

Nests are placed in hard-to-reach crevices – where natural or urban features provide safety from predators.

Diet – A Master of Aerial Hunting

This bird feeds exclusively in the air. Its prey includes:

• Flies
• Mosquitoes
• Beetles
• Butterflies

It glides between 10 and 100 meters above the ground. Even drinking happens on the wing – by skimming the water’s surface with its beak.

Reproduction – Sticky Homes Built with Saliva

From June to August, Pacific Swifts build their nests using feathers, plant material, and their own saliva. They prefer vertical surfaces such as cliff faces or eaves of buildings.

Breeding facts:

• Clutch size: 2–3 eggs
• Incubation: About 20 days
• Nestling period: 40–45 days
• Both parents feed the young until fledging

Migration – Long-Distance Champions

The Pacific Swift is a long-distance migrant. It follows the East Asian–Australasian flyway:

• Arrival in Japan: April to May
• Departure: Late summer
• Wintering grounds: Southeast Asia and northern Australia

Notably, it can even sleep while gliding – a rare skill shared by very few bird species.

Conservation Status – Stable but Sensitive

While the species is common and stable in Japan, its nesting sites are vulnerable:

• Threat from demolition of old buildings
• Disturbance of cliff habitats due to tourism or construction

Recommendation:
Protect known nesting areas to ensure long-term survival.

Fact Sheet – Pacific Swift at a Glance