The surrounding area of Yellowknife, Northwest Territories, Canada, is known for naturally and anthropogenically elevated concentrations of arsenic. Five bird species (gray jay [Perisoreus canadensis], American tree sparrow [Spizella arborea], dark-eyed junco [Junco hyemalis], yellow-rumped warbler [Dendroica coronata], and spruce grouse [Dendragapus canadensis]) were collected from this area. Their tissues were analyzed for total arsenic and for arsenic species, allowing us to report, to our knowledge for the first time, the arsenic characterization in terrestrial birds. Total arsenic concentrations were determined in the terrestrial birds by inductively coupled plasma-optical emission spectrometry, whereas arsenic speciation analysis was performed using high-performance liquid chromatography-inductively coupled plasma-mass spectrometry. Total arsenic concentrations were substantially higher in the terrestrial bird species studied from Yellowknife compared with those reported previously in the literature. The primary arsenic species detected in two of the bird species studied was arsenobetaine. Normally, arsenobetaine is not formed or retained by terrestrial animals. Thus, the birds in the present study were thought to be highly adapted compared with other terrestrial animals, because they were able to form and/or retain this relatively nontoxic arsenic compound. This adaptation is thought to be a consequence of the elevated concentrations of arsenic in the Yellowknife area.