This handsome lithograph — an illustration for some reason not listed in McCarthy — is the earliest depiction of a now well-known hybrid combination, that between the common goldeneye and the smew.
The bird was shot in the spring of 1825 on the Oker River near Braunschweig,
on a stretch where various duck and merganser species are regularly found every year in migration (open water is maintained here even in freezing temperatures by the rapid current). Fortunately, it came into the hands of a collector, who mounted it for his otherwise run-of-the-mill collection of common German birds.
When that collector died, apparently in the summer of 1828, A.F.E. Eimbeck, Inspector of the Ducal Museum in Braunschweig, obtained the “fairly well preserved specimen” and added it to the collections he oversaw. The following year, Eimbeck prepared a description of this “hitherto unknown, very striking German waterbird,” in the hope that
as a result of wider knowledge of this rarity, it might be determined in the future whether there exists anywhere another specimen resembling this one, and it would thus be determined whether this should be accepted as a new species or considered a hybrid.
Eimbeck reports that several of the ornithologists to whom he had shown the Braunschweig bird believed it to be a hybrid, but those expert opinions did not keep him from giving the creature a name: Mergus anatarius, the Entensäger, the “duck-merganser.”
Christian Ludwig Brehm agreed with Eimbeck that this curiosum was the representative of a newly discovered taxon — but he decided that it was not so much a duck-like merganser as a merganser-like duck, and so he named it the narrow-billed goldeneye, Clangula angustirostris.
Brehm appears to have been alone in his opinion. In 1840, H.R. Schinz (of dunlin fame), while dutifully reproducing Eimbeck’s species name, nevertheless appears to be among those who believe that the specimen represents a hybrid — but that it is no less noteworthy for it: this is, he says,
the only example other than the rackelhahn of two species of different genera living in the wild having bred together; extremely remarkable.
Naumann, too, four years later rather left the question open, but
the remarkable intermediate appearance, which would place this bird precisely halfway in between two known species, irresistibly suggests to the practiced observer at the first glance that this is a mixture or hybrid between the common goldeneye and the smew.
All the same, the title cut to Naumann’s waterfowl volume remains cautious: this is a “suspected hybrid.”
Not until 1887, though, would the assertion be made without qualification. In the Vogelwelt for December of that year, Rudolf Blasius, son of Eimbeck’s successor at the Braunschweig museum, published an illustrated study of Eimbeck’s Mergus anatarius.
Blasius’s subtitle says it all: the Braunschweig duck is a hybrid between the smew and the common goldeneye. While the other natural historians cited above could rely only on the specimen in that city’s museum, Blasius knew of three others: a Danish bird killed in February 1843 and named as a new species, Anas mergoides;
a third taken on Poel in the German Baltic in February 1865;
and finally one collected in Sweden in November 1881.
Blasius was able to handle three of those birds, and to work from a very careful description of the Swedish individual. Compiling a series of measurements of these four ducks and of smews and common goldeneyes, he was able to show that the hybrid individuals were exactly intermediate between the presumed parental species; he also presented detailed parallel plumage descriptions.
The precise comparison of the plumages of the adult male goldeneye and the adult male smew with those of the hybrids described … clearly leads to the conviction that we are truly dealing with hybrid forms and not with distinct bird species…. One can hardly doubt any longer that these are actually hybrids.
He goes on to urge zookeepers to help prove his point by intentionally breeding smews to goldeneye:
It would be a lovely experiment to produce these hybrids artificially.
As we now know, though, the birds do just fine out there on their own.
