We document for the first time a Red-naped Sapsucker (Sphyrapicus nuchalis) usurping the nest of a Red-breasted Nuthatch (Sitta canadensis). A nuthatch nest in the incubation phase was usurped by a male Red-naped Sapsucker on 23 May 2003, and a sapsucker nest was initiated in the cavity on 1 June. Red-naped Sapsuckers are primary cavity excavators that normally nest in live and dead quaking aspens (Populus tremuloides) infected with heart rot fungus (Fomes spp.). Red-breasted Nuthatches are weak excavators that most commonly nest in broken-topped conifer snags. Nest usurpation was likely due to a shortage of suitable nest sites in our study plot.