At the Cuckoo showing, galena-pyrite-chalcopyrite occur as blebs and pods within two large diorite dikes of the Proterozoic Moyie Intrusions which crosscut shales and argillites of the Helikian Aldridge Formation (Purcell Supergroup). The dikes are parallel, about 150 metres apart, and strike generally east with a vertical dip. A pod of sulphides about 38 centimetres wide was exposed within the dike material.

Three claims, the Cuckoo, Twilight, and Molly Bawn were owned in 1898 by George Watson and Jay Usher of Fort Steele and George Huggarth of Elko. Exploration work was done in 4 short adits, the longest being 15 metres in length. Two adits on the Twilight claim exposed slight mineralization, chiefly galena, (Minister of Mines Annual Report 1898, page 1005).

In mid-1983 a reconnaissance V.L.F. electromagnetic test survey was flown along northwest-southeast flight lines for R.H. Stanfield (Assessment Report 11681). Diagrams show this survey to have covered the Bull River Mine area, including the Cuckoo occurrence area, and a significant area extending southeast to the Elk River.

In 1991, 1206 line-kilometres of airborne electromagnetic (DIGHEM) survey completed for Bul River Mineral Corporation Ltd. (R.H. Stanfield) identified several anomalies on the Steeples claim block and portions of the Aspen claim block (Assessment Report 21155). The survey covered Bull River (082GNW002), Copper King (082GNW006), Cuckoo (082GNW028), Trilby (082GNW072), Old Abe (082GNW103), Bull River Gypsum (082GSW031), and Aspen (082GSW033).

Refer to Bull River (082GNW002) for details of the greater Bull River property which contained the Cuckoo occurrence and a minimum of 25 other documented mineral occurrences as of October 2022.