Last week I promised to do a series on common backyard birds and began with the hairy woodpecker. This week’s column looks at the similar downy woodpecker. Many people may think of this woodpecker as a scaled-down version of the hairy woodpecker, but differences exist between the two.

It may not always be possible to distinguish the two by size for the beginning birder. When viewed alongside a downy, a hairy is obviously bigger (think robin compared to sparrow), but you may not always have this luxury. A good field mark is to note the size of the beak in relation to the head. A hairy’s beak is at least the length of the head from front to back, and is clearly a powerful chiseling tool. A downy’s beak appears small and puny, and is less than half the length of the head.

A second field mark is the tail. The downy’s white outer tail feathers have black spots on them; the hairy’s white tail edges have no such spots.

Both of these woodpeckers will readily visit feeders so there will be ample opportunity to identify them by sight. However, voice and drumming patterns are also reliable cues. Downies have a descending rattle, described as resembling the whinny of a miniature horse; their call note is a flat, soft “pick” note. The rattle of a hairy woodpecker is flat, sharp, and does not descend in pitch, while their “peek” call note is also sharp and much louder.

The rapid drumming of a hairy makes it impossible to count beats; the downy’s slower drumming enables us to distinguish individual beats as it pounds a tree to advertise territory or attract a mate.

Another difference between the two is their choice of nest sites. Hairy woodpeckers often prefer to excavate their nest holes in live trees that have internal fungal decay, while downies often choose dead trees or the dead parts of trees.

Now, the similarities: both of these woodpeckers are thought to be largely monogamous; both occupy a range within which they will defend a territory surrounding a nest site. Both associate closely during the breeding season but drift apart once it is over. In the case of the downy woodpecker, the female will leave the male’s territory, especially if there are inadequate supplies of food.

As I bring this column to a close, I’d like to bring attention to differences in plumage patterns among individual downy woodpeckers, as mentioned in the second volume of Donald and Lillian Stokes’ delightful “A Guide to Bird Behavior.”

Apparently, the black and white pattern on the back of each bird’s head is unique to that bird, enabling us to distinguish individuals. The Stokes suggest sketching the pattern you see so you can begin to tell the birds apart. Although I couldn’t find a reference to this regarding hairy woodpeckers, I would think this could be the case for them as well.

And finally, what does “downy” refer to? There seems to be some speculation regarding this. The BNA states it could refer to “the soft white feathers of the white stripe on the lower back, in contrast to the similar, but more hair-like feathers on the hairy woodpecker… various authors have suggested… [a] reference to the soft appearance of its plumage… [or] the lesser bristles covering the nostrils of the downy as compared to those of the hairy.”

Small details on which to base a name – but there you have it.

NEWS bird columnist Chris Corio can be reached at bdnsports@bangordailynews.net