Nauru Reed-warbler - Behaviour and Ecology

Behaviour and Ecology

Nauru Reed Warbler nests are cup-shaped and woven from grasses and twigs. They sometimes include Cassytha filiformis vine or Casuarina equisetifolia needles. The nests are bound to upright stems in a way typical of warblers. Buden reported that the warblers nest in trees and shrubs at a height of 2 to 8 metres (6.6 to 26 ft). The species may also nest on the ground; the young in ground nests may be more vulnerable to predation by rats. Eggs have variously been reported in December and July, and ornithologist A. Pearson suggested that the species may nest all year round. The clutch size has been reported as two or three eggs. Incubation and fledgling periods are unknown. Pearson reported lower nesting than Buden, recording nests in bushes and undegrowth between 45 and 300 centimetres (18 and 120 in) from the ground, especially in forked braches of hibiscus and lime. Buden reported that the birds were more vocal in December than in March and April. The song has been described as similar to that of a Song Thrush, Common Blackbird, or Willie Wagtail, and it is delivered both day and night.

Finsch described the warbler as insectivorous, feeding primarily on dragonflies. Six species of dragonfly have been observed on the island; Ischnura aurora, Anax guttatus, Diplacodes bipunctata, Pantala flavescens, Tholymis tillarga and Tramea transmarina. Buden did not observe the species feeding on dragonflies, but did see three different feeding habits. Most frequently, the birds were seen moving through trees and shrubs, catching prey on the foliage. Other birds were seen perched close to the floor, darting to the ground, and returning to the perch with prey. In open areas, the birds were observed moving across the ground, "occasionally grasping a presumed prey item." In coastal areas, they have been observed feeding in coconut trees. Potential predators for the birdlife of Nauru in general include feral cats and dogs, as well as the Polynesian rat and the Tanezumi rat. Feral cats and wild rats in particular are potential threats to the Nauru Reed Warbler.