The McKay's Bunting (Plectrophenax hyperboreus) is one of the rarest passerine species in North America and breeds solely on St. Matthew and Hall islands in the remote Bering Sea, Alaska. We examined the nesting ecology of this poorly studied species on St. Matthew Island in 1982, 1983, and 2003. We found that the high breeding density of the McKay's Bunting may account for the lower clutch size and number of young fledged per successful nest compared to its sister species, the Snow Bunting (P. nivalis). The proportion of eggs that successfully hatched was higher for McKay's Buntings than Snow Buntings breeding at other Arctic locations in North America. Daily nest survival declined during egg-laying and incubation and increased throughout the nestling period. Nesting chronology was earlier in 2003 compared to the 1980s; however, daily nest survival was similar between decades. To assess how McKay's Buntings are responding to climate-mediated changes to physical and biotic conditions, we recommend monitoring the species' reproductive rates and population size.