British protectorate declared over the Gilbert Islands (27 May-17 June 1892, by Captain Edward Davis, HMS Royalist) and the Ellice Islands (9-16 October 1892, by Captain Herbert Gibson, HMS Curacoa), upgraded to full Crown Colony status on 12 January 1916. The colony later absorbed Ocean Island/Banaba (phosphate mining from 1900), the Phoenix Islands (1937) and the British-claimed portion of the Line Islands, and was administered under the umbrella British Western Pacific Territories framework (alongside the neighboring Solomon Islands Protectorate). No canonical record currently covers this 1892-1976 colonial union predating the separate Kiribati/Tuvalu independence records already in the dataset.
The ethnically and linguistically distinct Ellice Islands (Polynesian, vs. the Gilbertese Micronesian majority) voted by referendum in 1974 to separate; legal separation took effect 1 October 1975, with full administrative split on 1 January 1976. The Ellice Islands became independent Tuvalu on 1 October 1978 (canonical record 'tuvalu'); the remaining Gilbert, Phoenix and Line Islands became independent Kiribati on 12 July 1979 (canonical record 'kiribati').
Open Library-verified (work OL22661324W / OL37359627W, first published 1979); widely catalogued under the fuller title 'Kiribati: Aspects of History,' a University of the South Pacific Institute of Pacific Studies volume covering Gilbertese history through the colonial protectorate/colony period to independence -- the closest polity-specific monograph found.