Defining full life cycle biology is critical for comprehensive conservation planning. To that end, life history information on the endangered Mariana swiftlet (Aerodramus bartschi) is scarce. Therefore, this study examined the reproductive biology of the Mariana swiftlet over five annual cycles on the island of Oahu in the Hawaiian Islands. This introduced population used a human-made tunnel for roosting and nesting, and was studied as a surrogate to negate interference with the endangered populations in the Mariana Islands. Active nests (N = 478) were observed in every month of the year with peak nesting activity between May and September. A clutch of one white egg was laid in a nest that was secured to a tunnel ledge or wall with copious amounts of mucus-like salivary cement. Mean incubation and nestling periods averaged 23.91 3.30 days (range = 1830, N = 233) and 55.04 6.61 days (range = 4184,
N = 228), respectively. Estimated nest success was 63%. Over half (52%) of nest failures were attributed to eggs found on the tunnel floor. Rat (Rattus spp.) depredation was also an important cause of nest failure and often resulted in simultaneous loss of most nests. Mariana swiftlets completely recycled breeding activities following rat depredation events. The daily nest survival
rate varied with nest age (quadratic) within years. These results from a surrogate population provide important life history information for proposed plans to enhance swiftlet populations with reintroductions in the Mariana Islands.