Loxia curvirostra

Loxia sinesciuris was formerly considered conspecific with L. curvirostra, but treated as a separate species on the basis of high levels of premating reproductive isolation (Smith and Benkman 2007, Benkman et al. 2009), despite regular and likely long-term sympatric breeding of multiple call types of Red Crossbill, and genomic differences (Parchman et al. 2016) (AOU 2017).

Widespread in North America and Eurasia; large population size; many occurrences, though these are variable in location; apparently stable or slowly declining overall in North America but trends are difficult to determine; taxonomic status is uncertain, and status and rank could change significantly if ongoing research confirms the suspicion that L. curvirostra consists of multiple species.

As traditionally defined, this species occurs widely in Eurasia and North America. In North America it is resident from southeastern Alaska eastward across boreal Canada to Newfoundland and Nova Scotia, and south in the west to northern Baja California and through the mountains to Nicaragua, and south in the east to Great Lakes region, southern Appalachian Mountains, New York, and New England. (Adkisson 1996, AOU 1998). In the nonbreeding season this species disperses irregularly throughout much of the remainder of the contiguous United States. The several types or species of red crossbills are highly nomadic and may shift breeding ranges by as much as a thousand miles between one breeding season and the next (Groth 1993).

This species is represented by a large number of occurrences (subpopulations), but crossbills are not permanent residents of any particular occurrence.

Decline of the Newfoundland population (subspecies percna) evidently has been due at least in part to competition from the introduced red squirrel (Benkman 1993).

Local declines and increases reflect variations in local conifer cone crops; widespread deforestation or low cone availability results in emigration of crossbills to other areas. Net reduction in total area of mature forest (or in overall cone availability) presumably would result in an overall decline in the crossbill population, so recent forestry practices and widespread regional tree mortality due to insect outbreaks likely are detrimental to crossbills, at least temporarily.