To reduce costs associated with nest building, some birds steal (kleptoparasitize) nest material. While this behavior is rarely reported in solitary nesting birds, it has been previously documented in 2 species of white-eyes, the Japanese White-eye (Zosterops japonicus) and the Indian White-eye (Z. palpebrosus). During surveys for Tinian Monarchs (Monarcha takatsukasae) on Tinian Island in the Northern Mariana Islands, we documented nest material kleptoparasitism by the Bridled White-eye (Z. conspicillatus). Through camera-trap footage and real-time observation, we observed Bridled White-eyes stealing material from 2 other forest bird species: the Micronesian Rufous Fantail (Rhipidura versicolor; n = 1 observation) and Tinian Monarch (n = 7). We documented nest material piracy during multiple nesting phases including building, incubation, and post-fledge, and from abandoned and depredated nests. This behavior was previously undocumented in the Bridled White-eye, and nest material kleptoparasitism is not documented in any other forest birds in the Mariana Islands. Kleptoparasitism of nest material has been known to cause destruction or abandonment of the host’s nest. Given the potential implications of nest material kleptoparasitism on host nesting behavior and success, and that the Bridled White-eye is estimated to be the most abundant forest bird on Tinian, our observations warrant inquiry into how this behavior could be affecting the broader ecology of forest birds in the Mariana Islands.

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