Have Rodents Impacted the Breeding and Distribution of Black Noddy <i>Anous minutus</i> on Lord Howe Island?

Rodents are well known to impact nesting seabirds. However, not all seabird species are equally susceptible to rodents due to variations in size, nest-site selection, or nesting behaviour. The Black Noddy Anous minutus, a common tropical, tree-nesting species, began colonisation of North Bay on Australia’s Lord Howe Island in 1989, 70 years after the establishment of Black Rats Rattus rattus. In 2014, when the breeding colony consisted of 560 pairs, we commenced a pilot study to assess impacts of rodents. Ten motion-triggered cameras monitoring 12 nests showed no rodent presence on any branches within view; 11 of those nesting attempts (92%) resulted in fledglings. A further 38 nests were monitored for breeding success, of which 28 (74%) produced a fledgling. In 2019, coincident with the eradication of rodents from Lord Howe Island, noddies started breeding in small numbers in the Settlement Area. In 2020, visitor disturbance was low at this colony due to COVID-19 lockdowns, and by the 2022 season, the entire original North Bay colony had relocated here. From initial colonisation until 2014, the population grew at 10% per annum, but it increased only marginally (0.7% per annum) during 2014–2024. It appears that neither colony establishment nor breeding by the Black Noddy is affected by the presence of Black Rats. Contributing factors may include the selection of tree nest sites, which reduces rodent access and provides only one point of contact to a nest, and the presence of adults at nests during all nocturnal periods, which enables nest defence.