Emperor Fairywren

It is the largest fairywren, being 13–16 cm (5.1–6.3 in) long and weighing 12–17 g (0.42–0.60 oz). Males of the nominate race have light royal blue crowns. The forehead, lores, and the side of the head up till the narrow collar is black. The upper back, along with the scapulars and uppertail-coverts is a deep turquoise-blue, with the lower back being blue-black. The upperwing and the tail are blackish-blue with tinges of blue, and the throats and underparts are a navy blue in color. It has dark brown eyes, black bill, and dark grey-brown legs. Females of the nominate race have a head that looks similar to the male, but have chestnut upperparts, white underparts, deep blue throats, and a black tail with whitish tips. They also have lighter and more mid-brown legs, along with duller crowns that are deeper in colour. Juveniles look like females, but have a dusky head, rusty brown upperparts, and entirely white underparts. M. c. mysorensis differs slightly in appearance with its crown being cobalt blue instead of royal blue, and M. c. bonapartii is slightly darker than the nominate race.

Vocalisations. Its songs are a reel that are preceded and followed by sets of 3 notes. This call is frequently given by groups of emperor fairywrens while they are foraging. The contact calls for the bird are "tst-tst-tst-tst", with the alarm call being "tschik".

It is found on New Guinea and the Aru Islands. It is found in tropical lowland, forests, wetlands, and degraded former forests. They inhabit dense secondary growth that occurs at the edges of forest, along with forest openings, riversides, roadsides and overgrown gardens. They are not as affected by habitat disturbance and appear to like disturbed habitats like gardens and parks.

The emperor fairywren feeds mainly on arthropods. They eat beetles, bugs, moths, grasshoppers, and spiders. Foraging is conducted in noisy family groups, with the insects foraged from leaves, palm fronds and branches within 1 m (3.3 ft) of the ground.