Ever since July of 2017, I have been on a mission to study the Song Sparrows of the interior Pacific Northwest. The reason why I've become so obsessed with this research is because of a very Eastern-looking (Melospiza melodia melodia) Song of that summer. However, when I discussed that bird with several experts, it turned out to be a singing Mountain Song (M. m. montana).

These experts confirmed the Mountain Song's id because of the white supercilium. However, eBird lumped the Mountain and Merrill's Song together as the Song Sparrow (merrilli/montana) or more commonly the Interior West Group. The main id marks of this group is the ashy gray facial stripes, reddish body and heavy underparts streaking. But if my individual is indeed a Mountain Song, why does it differ so much from the Merrill's? Especially when the Mountain looks so much like Eastern.

That's why I'm observing each Song I see very closely. This journal post will show what I saw on March 2, 2018. Location is Wilkinson Lane, a backroad at Ladd Marsh Wildlife Management Unit, Union County, Oregon. Over the course of fifty-three minutes, I counted thirty-two different individual Songs, a huge number in one location. It also helps with my study of these highly complex species.

In Union Co, Oregon, two subspecies reside in the winter. From what I've seen, the Merrill's Song dominates the other subspecies. Roughly 84% of all the Songs I see are Merrill's. The second is the Mountain Song. Both subspecies breed in the county and integration is known in these range overlaps.

Now let's assume that my white supercilium Songs are Mountain and gray for Merrill's. Getting the numbers, I saw five Mountain Songs and twenty-one Merrill's. Neat thing was, the last six individuals had a white lore with gray supercilium, somewhat resembling a White-throated Sparrow's yellow lore and white supercilium. Are these bicolored supercilium Songs intergrades? It is indeed highly probably but without mtDNA testing, we'll never know for sure. One thing though, I will not stop my studying of these beautiful birds because there's almost something new to learn about them!

Posted on March 13, 2019 04:59 AM by birdwhisperer