The ʻuaʻu, or Hawaiian Petrel Pterodroma sandwichensis, is an endangered seabird endemic to the Hawaiian Islands. Genetic, morphometric, and behavioural differences have previously been found between different island populations of the species. Understanding the breeding phenology of different populations of ʻuaʻu is therefore vital for conservation actions targeting the species. To assess breeding phenology of ʻuaʻu on the islands of Kauaʻi and Lānaʻi, two main techniques were used over a 12-year period: direct burrow monitoring and burrow cameras. The breeding phenology of the ʻuaʻu is described based on this data. On Kauaʻi, breeding birds arrive in the middle of April, undergo an exodus of approximately one month, and return to lay in the beginning of June. Incubation continues until early August, followed by chick-rearing, which ends on average two weeks before the chick fledges. Fledging starts in mid-October, peaks in mid-November, and ends in the third week of December. Lānaʻi birds arrive two weeks earlier and fledge one week earlier than on Kauaʻi. On both islands breeding was asynchronous with a 68-day (Kauaʻi) and 48-day (Lānaʻi) gap between first and last fledging birds. Considering phenology data across its entire Hawaiian range, ʻuaʻu first arrive on east Maui, then Lānaʻi, Hawaiʻi Island, and Kauaʻi in that order. These differences in timing presumably reflect and/or reinforce genetic differentiation between subpopulations of the species. The utility of this information is discussed in terms of directing management actions towards key periods of vulnerability to introduced predators, including peak incubation, chick emergence, and chick exercise periods. Description of island-specific phenologies is also critical to inform efforts to rescue fledglings disoriented by artificial light, mitigate powerline collisions, and refine existing monitoring and restoration projects. Future work using acoustic monitoring and data collected at social attraction sites is recommended for assessing the phenology of non-breeders at colonies.

He manu lawaiʻa ka ʻuaʻu (Pterodroma sandwichensis) no ka pae ʻāina ʻo Hawaiʻi, he manu ʻāpaʻakuma ia i ʻane nalowale. ʻIke ʻē ʻia kekahi mau mea ʻokoʻa ma nā heluna manu o nā mokupuni like ʻole, ma ka welo kūʻauhau, ma ke ʻano kino, a ma ka hana kekahi. No laila, he koʻikoʻi ka hoʻomaopopo ʻana i ke ʻano o ko nā ʻuaʻu hoʻomau ʻana ma nā mokupuni ʻokoʻa, i mea e mālama ai i kēia lāhui manu. I kilo ʻia ai ke ʻano o ko ka ʻuaʻu hoʻomau ʻana ma nā mokupuni ʻo Kauaʻi lāua ʻo Lānaʻi, ʻelua nā kiʻina hana nui i hoʻohana ʻia ma nā makahiki he 12; ʻo ke kilo pololei ʻana aku i ko lākou mau lua, a me ka hoʻonoho ʻana i ka pahu paʻi kiʻi ma kahi o nā lua. Hōʻike ʻia ke ʻano o ka hoʻomau ʻana o ka ʻuaʻu ma nā mokupuni ʻokoʻa ma o kēia ʻike pili. Ma Kauaʻi, hōʻea nā manu e hoʻomau ana i waena o ʻApelila, haʻalele lākou no kekahi mahina, a hoʻi lākou e hānau i ka hoʻomaka ʻana o Iune. Hoʻomoe ʻia ka hua ā hiki i ka hoʻomaka ʻana o ʻAukake, a laila hānai ʻia ka pūnua. Pau ka hānai ʻia ʻana he ʻelua pule ma mua o ko ka pūnua lele ʻana, ma ka ʻawelike. Hoʻomaka ka lele ʻana ma waena o ʻOkakopa, ā hiki i ka nui loa i waena o Nowemapa, ā pau i ka pule ʻekolu o Kēkēmapa. He ʻelua pule ma mua ka hikina o nā ʻuaʻu Lānaʻi, a lele lākou he hoʻokahi pule ma mua kekahi, ke hoʻohālike aku i ko Kauaʻi. Ma nā mokupuni ʻelua, ʻaʻole hānau nā manu i ka manawa hoʻokahi. ʻO ke kaʻawale ʻana ma waena o ka pūnua lele mua a me ka lele hope, he 68 lā ma Kauaʻi a he 48 lā ma Lānaʻi. Ke nānā ʻia ka ʻike pili o ka pae ʻāina holoʻokoʻa, hiki mua ka ʻuaʻu ma Maui hikina, ma Lānaʻi, ma Hawaiʻi mokupuni, a laila ma Kauaʻi, i ia kaʻina nō. Ma nā manawa ʻokoʻa o ka hōʻea ʻana i hōʻike ʻia ai paha a hoʻokumu ʻia ai paha nā welo kūʻauhau o nā heluna manu o kēia lāhui. Hōʻike ʻia ka waiwai o kēia ʻike pili no ka mālama ʻana i ka ʻuaʻu i kōna mau wā i hiki wale ke pilikia i nā holoholona malihini, e laʻa ka wā nui o ka hoʻomoe hua ʻana, ka puka ʻana o nā pūnua, a me ka wā hoʻēheu. He koʻikoʻi hoʻi ka hōʻike ʻana i nā ʻano ʻokoʻa o ko nā mokupuni i mea e alakaʻi ai i ka hoʻopakele ʻana i nā pūnua i pilikia i ke kukui uila, i emi ai ka hoʻokuʻi ʻana i ka uea kelepona, a i hoʻokāʻoi ʻia ai hoʻi nā papahana e kū nei no ke kilo ʻana a me ka hoʻōla hou ʻana iā lākou. Ke paipai ʻia nei no kēia mua aku ke ana ʻana i ko lākou kani a me ka nānā ʻana i ka ʻike pili i loaʻa ma nā kahua kūhea manu no ke kilo ʻana i nā manu e hoʻomau ʻole ana ma loko o nā heluna nui.