Leach’s Storm Petrels Hydrobates leucorhous breeding on Gloup Holm: the third discovered breeding site in Shetland

In the UK, Leach’s Storm Petrel Hydrobates leucorhous breeding colonies are few and geographically very remote. Single Leach’s Storm Petrels were heard calling from burrows on Gloup Holm, north Shetland, in July 2019, July 2020 and August 2020, in response to call-playback. The occupied burrow network found in August 2020 was examined by endoscope and a Leach’s Storm Petrel eggshell was seen, constituting the first proven breeding record at this site. A sample call was recorded from each bird heard, sonograms produced, and comparison with criteria for determining sex from calls indicated the bird heard in 2019 was female and those in 2020 were one or possibly two males. Currently, Leach’s Storm Petrel breeds in very low numbers in Shetland on just two small islands. Restoration projects to eradicate introduced predators and preserve natural breeding habitat on select other islands could result in increased breeding numbers.