Little Brown Birds of Confusion

Autumn migration gives us many opportunities for interesting sightings, discoveries, and challenging identifications.  Moreover, the eagerness to see a particular species can get in the way of good observations. One example is Lincoln’s Sparrow, whose northern boreal distribution extends down into our Northeast Kingdom and on a few ski slopes such as Stratton Mountain.  However, Lincoln’s Sparrows are renowned for staying on their breeding grounds until late in the season, then all migrating within a quite short duration.

Vermont eBird data is dramatic, with the migration beginning during the week of September 15th, peaking in the week of October 1st, and complete by the week of October 22nd.  The highest counts are between September 22nd and October 15th.  Early dispersals are quite rare, so the chance to see one away from a breeding site is very unusual until mid-September.

But it is not unusual in late summer for juvenile sparrows to be confused with Lincoln’s due to the juvenile’s finely lined breast and often evident buffy breast. Song Swamp sparrow juveniles seem to be most often mistaken for Lincoln’s, as can be juvenile Chipping, and other sparrow species. Even banders can have difficulties. In 1986 Chris Rimmer wrote a detailed paper examining the identification of juvenile Lincoln’s and Swamp sparrows that remains an important reference today.

So, as always, look for as many diagnostic features that you can with migrant birds, many of whom are youngsters with their own set of clothes and their own music.  If a Lincoln’s Sparrow sighting is your quest, mark September 15th on the calendar, and you have a full month’s worth of opportunity for that elusive little-brown-bird with the perky crown.  And if you are unsure of the identification, you can always choose Lincoln’s/Swamp sparrow on your eBird checklist.

Enjoy the challenge!