"Black and Tan" has a different connotation in the bird world than in a pub. Shown is a male Eastern Towhee, northern variety.
I have a friend whose favorite beer is a Black and Tan. I was always intrigued when he drank it by the fact that the drink was two-toned: light tan on the bottom, and a very dark, almost black on top. While Yuengling makes and sells a pre-mixed “original” Black and Tan, my friend preferred to make his own the old British way by pouring pale lager or ale into the bottom of the glass, followed by a very slow pouring of a dark stout into the top. The slow pour kept the two beers from mixing because the stout was less dense than the lager and the black and tan colors remained separated until the glass was tipped into the drinker’s mouth. The whole idea stems back to the 1880’s. en.wikipedia.org/wiki/Black_and_Tan. I have no idea what it tastes like.
White-throated Sparrows come in two color phases: black and tan. While other bird species come in different color phases, i.e. Great Blue Herons, Screech Owls, Short-tailed Hawks, Red-tailed Hawks, and Snow Geese. The White-throated Sparrow is unique in that approximately equal numbers of both color phases are produced, black White-throats are universally more aggressive and tan White-throats are universally more passive, and most importantly: male or female black White-throated Sparrows mate almost exclusively with tan female or male White-throated Sparrows, while tan male or female White-throats mate almost exclusively with black female or male White-throats.
It is the absolute ultimate in “opposites attract.” nationalzoo.si.edu/scbi/migratorybirds/featured_birds/default.cfm?bird=White-throated_Sparrow. I believe White-throated Sparrows are the only sparrow species to exhibit this complex pattern, and I was not able to discover any other species in any bird family to engage in this unique behavior.
White-throated Sparrows do not reach the Treasure Coast in their winter migration. Occasionally they are reported in the winter as far south as central Florida, but are more common in the winter in the Florida Panhandle. While they only occur at our home area in Pennsylvania in the winter, they are abundant at that time, and they are still present when we complete our north-bound spring migration. See: stlucieaudubon.org/hartBeat/hb2012/hb120926Martins.html. By early to mid-May, all of our White-throats will have migrated farther north, primarily into Canada, for their breeding purposes.
Another black and tan scenario comes to mind: Eastern Towhees. The male is black above, with rufous sides and a white belly, while the female (right) is tan in the same areas where the male is black. Florida Towhees have white eyes: See stlucieaudubon.org/images/BirdPhotos/EasternTowhee.jpg, while northern Towhees have red eyes, but that difference has not been deemed sufficient to consider them separate species. One can find Eastern Towhees year round in Florida, but in Pennsylvania, they migrate, both ways, pretty much about the same time that we migrate.
What does black and tan beer have to do with the birds described? Not much of anything really, except a commercial for Yuengling “original” Black and Tan reminded me of my friend’s preference for the brew, and that occurred while I was looking at White-throated Sparrows, and that jarred my recollection of a birding club program describing a study where the black and tan “opposites attract” behavior of White-throats was documented. Then, while taking photos of the White-throats for this article, a pair of Eastern Towhees serendipitously put in an appearance, and another light bulb went off in this old head. My long time ago English teacher would have called that thought process “stream of consciousness.” Luckily, Jewel did not interrupt that stream of thought at any point, or I might never have reached this point in the article. (5/30/2013)