During the spring and summer months, it is just about impossible not to see what you want, due to the sheer numbers and varieties of birds. It is also easier to find birds then because they are advertising their whereabouts with their mating and territorial songs.

But locating birds in winter isn’t necessarily impossible; you just have to know where to look.

Coastal areas and unfrozen sections of rivers can be gold mines for wintering waterfowl, for example. On a recent trip to Mt. Desert Island, we found red-necked grebes, red-breasted mergansers, common loons, an arctic loon, harlequin ducks, purple sandpipers, razorbill auks, northern gannets, and hooded mergansers.

Last Sunday, we found common goldeneye ducks, Barrow’s goldeneye ducks, and common mergansers on the Penobscot River just south of the Sea Dog restaurant in Bangor. It was very unexpected; the day before had been a very bleak day of birding, with only one chickadee seen towards dusk.

The ducks were a treat to see. The common goldeneyes caught our attention first. They were grouped loosely together, numbering twenty in all. The majority of them were males, easy to spot because of the large amount of white on their bodies. Their heads are completely dark, with one oval white patch just below their eyes, towards their bills.

A short distance upriver another group of ducks caught our attention-they were the less familiar Barrow’s goldeneyes. They differed from the common goldeneyes by having darker backs and an elongated white patch on their dark heads. The females were also easily distinguishable because of their pinkish beaks-something they don’t share with the common goldeneye.

Soon after, we encountered the common mergansers. While we were watching them, a flock of herring and ring-billed gulls suddenly took to the air from the field behind us. The reason for their agitation became evident as an adult bald eagle came flying downriver; it ignored the gulls and alighted on the tip of a bare branch on the opposite bank, only to be mobbed by crows.

This wasn’t the last treat of the day, however. Open areas of marsh or field can also provide food for wintering raptors such as the rough-legged hawk. This large hawk breeds in the Arctic, but every winter several are reported throughout Maine, and I was thrilled at my first sighting of this bird of prey.

We were on the Wiswell Road heading toward the Fields Pond Nature Center in Holden; as we passed the fields through which the power line runs, the large raptor flapped into view. It settled atop a pine bordering the field, and I glimpsed its robust, dark body. By the time we had turned around and driven back, the bird had disappeared. But luck was with us, for soon it appeared again, flying east, and we were able to view it for a few more seconds.

Not bad for birding on a winter’s day!

Chris Corio, a volunteer at Fields Pond Nature Center in Holden, can be reached at fieldspond@juno.com