No doubt some readers are old enough to recall Dr. Doolittle's imaginary hybrid between a gazelle and a unicorn, the pushmi-pullyu. Without going into the details of pushmi-pullyu taxonomy, suffice to say that this issue's mystery bird shares one important characteristic with that mythical creature. Specifically, one of the birds in the photograph is seemingly mired in an identity crisis. That's right, the bird on the left fails to match precisely any duck-like bird regularly occurring in Massachusetts. This observation brings us back to the fictitious pushmi-pullyu by suggesting that we might need to consider interspecies hybridization to identify the mystery bird.
There is little doubt that the birds in the picture are ducks of some kind. A cursory search through a field guide will suggest that the small, white-chested, dark-headed duck with a white patch on the side of its head in the foreground of the picture is either a female or immature male Bufflehead. The other duck, however, fails to match field guide depiction of any other waterfowl species. Clearly, the mystery bird is larger than the Bufflehead in the photograph, and it also has a larger bill, extensive white sides and chest, and a unique head and facial pattern that fails to match any other North American waterfowl. Focusing on the mystery duck's gleaming white sides and chest and its black back significantly narrows the field of possibilities. Only the drakes of Common Goldeneye, Bufflehead, and Common Merganser share these color characteristics. Common Merganser can be eliminated by the shape of the bill, which in all merganser species is narrow, tapered, and pointed at the tip.
A drake Common Goldeneye has a large, somewhat angular-shaped head, and a conspicuous white spot on the face between the eye and the bill. A Bufflehead drake is small and compact, with a small blue-gray bill and a prominent round white patch covering the top and back of the head. When these various features are compared to the mystery duck, the head pattern is decidedly aberrant—intermediate?—in appearance. A close examination of the color photograph on the website also hints at a dark green iridescence on the head of the mystery duck which is a characteristic of drake Common Goldeneyes. Given the overall mix of features, including the size and somewhat chunky shape of the mystery species, everything points to the quiz bird as a probable Bufflehead x Common Goldeneye (Bucephala albeola x Bucephala clangula) hybrid.
Hybrids of these two closely related species, though apparently not common in the wild, have been well documented in the literature. The breeding and wintering ranges of the two species overlap extensively, and both species are cavity nesters that use similar habitats for breeding, so hybridization is not unexpected. Without attempting a lengthy explanation of the genetics and behavioral aspects of waterfowl hybridization, suffice to say that both phenotype (the observable characteristics resulting from gene interactions) and biological probability suggest that the mystery bird is most likely a first-generation hybrid between a Common Goldeneye and a Bufflehead.
In Massachusetts, Common Goldeneyes and Buffleheads are common spring and fall migrants and are winter residents on saltwater and freshwater lakes and ponds. Both species typically arrive in mid-fall and generally depart by mid to late April.
David Clapp photographed this unusual hybrid waterfowl in midwinter of 2019–2020 at Rock Harbor in Orleans, Massachusetts, where it spent much of the winter.