Volume 40 Number 1 23 Introduction Hybridization among birds—the produc- tion of offspring when members of two different species breed—is a common occurrence, especially among Anseri- formes, the family of waterfowl (Grant and Grant 1992). Hybrid offspring often show intermediate physical characteris- tics between their two parent species, such as overall size, colouration and structure. The eBird/Clements checklist lists 545 known hybrids of birds world- wide, with 137 (25.1%) of those hybrids belonging to Anseriformes (Clements et al. 2021). However, these are only the hybrids that have been reported, and like- ly do not represent a complete listing of the world’s bird hybrids (McCarthy 2006). The true number of hybrids may be much higher, as hybridization tends to be a rare event and not all bird families are as amenable to the detection of hybrids as are waterfowl, and so the prob- ability of detecting a hybrid is generally low (Grant and Grant 1992; Aliabadian and Nijman 2007). Canvasback (Aythya valisineria) is a duck species that hybridizes with other duck species. Some confirmed hybrids with Canvasback include Redhead (Aythya americana; Haramis 1982), Common Pochard (Aythya farina; Vini- combe 2003) and Ring-necked Duck (Aythya collaris; McCarthy 2006). Less occurring but confirmed hybrids within the Aythya genus include Lesser Scaup (Aythya affinis; McCarthy 2006), Greater Scaup (Aythya marila; Gray 1958, Sibley 2000) and Tufted Duck (Aythya fuligula: Gillham and Gillham 2000). Most natu- ral hybridizations involving Canvasback appear to be within the Aythya genus, but there also exist records of hybridizations across genera, such as with Mallard (Anas platyrynchos: Phillips 1922, McCarthy 2006) and possibly American Wigeon (Anas americana; Edscorn 1974). Ruddy Duck (Oxyura jamaicensis) has also been shown to hybridize, but to a much lesser extent than Canvasback. Only one hybrid involving a Ruddy Duck is usually acknowledged, that being a Ruddy x White-headed Duck (Oxyura A possible Canvasback x Ruddy Duck hybrid Brandon P.M. Edwards and Mike Bouman