In my last post I showed the female common goldeneye, which is a “near twin” to the female Barrow’s goldeneye (Bucephata islandica). So while I wait for the tree leaves, grasses, wildflowers and other spring flora and fungi to belatedly make their appearance, I can show the close similarity between the male common goldeneye (Bucephata clangula) and its look-alike cousin, the male Barrow’s goldeneye.
As with their female counterparts, this male pair requires a good look to identify in the field. The most obvious difference between the male Barrow’s and common goldeneyes is the cheek patch on their faces. The common goldeneye has a white oval or circular cheek patch while the Barrow’s goldeneye boasts a crescent-shaped white patch on its face. The common goldeneye’s head is more angular or less rounded than the head of the Barrow’s goldeneye and its bill is longer. For me, those distinctions are difficult to determine on a single swimming bird that does not even have the courtesy to remain still for me to observe. Although the male common goldeneye has an iridescent green-black head and the Barrow’s head is more a purple-black, unless the light is at the exact correct angle their heads both look dark. A quick glance is often not enough to distinguish this “pair”.
Common goldeneyes are good divers, often going as deep as 20 feet and staying underwater for up to a half minute. While under the water common goldeneyes overturn stones in search of crabs, crayfish, amphipods and other crustaceans, which make up about three quarters of their diet. Small fish and aquatic seeds and tubers are also eaten.
It is interesting how when reading about a particular subject an almost offhanded comment can pique one’s interest and lead to further investigation. A statement that the common goldeneye is the only duck in North America known to derive benefits from lake acidification sparked my curiosity. A1994 paper by Poysa, Rask and Nummi that looked at the relationship between acidification, perch and common goldeneyes in Finnish lakes, as well as several other publications, noted that acidification (think of sulfur released from burning or smokestacks, for one example) causes acid sensitive fish to disappear in a lake. Once the fish die the invertebrates proliferate. Common goldeneyes, whose diet normally overlaps with that of the fish, no longer must compete with the fish for their preferred invertebrate diet and so can flourish – indeed a “benefit” to the common goldeneye. The research on this topic is sporadic and all elements have not, to my knowledge, been controlled. However, it does for now appear that indeed lake acidification might be advantageous to common goldeneyes.
This common goldeneye male was photographed on Hat Creek near Baum Lake (Shasta County CA).