Linnea Saukko deserves congratulations for looking closely at the variations in American Robins in a central Ohio neighborhood and for posting comments on this yesterday. One of the best things that birders can do to improve our skills at identification is to increase our understanding of individual variation in birds. For several years I was teaching a series of intensive five-day courses on bird I.D. at various points in the US and Canada, and one of the exercises that we did was to find a flock of some species of bird and start looking closely at individual variation. Without fail, we would find that no two individuals looked exactly the same. This seems to be a universal phenomenon among birds: if we look closely enough, no two individuals look exactly alike (and it follows that no bird will ever look exactly like the picture in the field guide!). Part of the variation in American Robins is owing to age and sex differences. At this season the adult males (more than a year old) tend to be the darkest and most richly colored, while the young females (hatched just last summer) tend to be the palest and drabbest. Males tend to have blacker heads than females, while adults tend to have larger white tail spots than young birds. But individual variation is so major that even with a good look, we can only guess at the age and sex of of a given bird. Some of the variability in American Robins seen in Ohio could also be owing to geographic variation, with birds originating from different populations, but this is very hard to prove for any given individual. The phenomenon of subspecies is widely misunderstood, partly because it's an artificial category. Any given individual either is or isn't an American Robin -- the definition of that species is pretty clear -- but you often can't assign an individual to a particular subspecies. Here's a way to look at it. If you leave Ohio in early summer and drive north into Canada, by the time you get to the coast of Labrador you may notice that the American Robins there tend to look a little darker, and some of them are quite blackish on the nape and back. Most technical references will call this a different subspecies (T. m. nigrideus) from the one common in Ohio (T. m. migratorius). But on the drive north, you will not have noticed any abrupt change from one subspecies to another; rather, it's gradual and clinal. (And some variants of our local American Robins can look very black-backed, like the Labrador birds, so identifying this subspecies out of range is very difficult.) Likewise, if you drive south from Ohio in early summer, by the time you get to the Gulf Coast states, you may notice that the American Robins there tend to be slightly paler and very slightly smaller. These are usually called a different subspecies (T. m. achrusterus), but again you wouldn't notice a sharp division between the subspecies, because the change is gradual and clinal. (Some past authorities have said that T. m. achrusterus gets into southern Ohio, but it's a matter of opinion, depending on where you draw the line in the middle of a gradual cline.) So what does it mean when we see variation in American Robins in Ohio? If we see an obviously mated pair in summer, the one with the blacker head and richer rufous chest is almost certainly the male. In a winter flock, it's almost impossible to be certain of what the variations mean. But it's still extremely worthwhile to study the individual variations in common birds. It's a great way of increasing our total understanding of birds, and increasing our chances of spotting those that are actually of different species. Kenn Kaufman Rocky Ridge, Ohio ______________________________________________________________________ Ohio-birds mailing list, a service of the Ohio Ornithological Society. Our thanks to Miami University for hosting this mailing list. You can join or leave the list, or change your options, at: http://listserv.muohio.edu/scripts/wa.exe?LIST=OHIO-BIRDS Send questions or comments about the list to: [log in to unmask]