New York State Rarities - Pacific Loon

On Saturday 1 March 2003, Dale Dyer discovered a Pacific Loon (Gavia Pacifica) at Captree State Park, Suffolk County, New York. The bird was still present the next morning (Sunday 2 March 2003) and in spite of heavy rain and thick mist, gave excellent views for those who braved the inclement conditions. The loon fed in the tidal current that sweeps around the eastern end of Jones Island at Captree SP. During the time of my observation is was continuously active, repeatedly making short dives. Once or twice it paused to preen. No other loon species were present, although a Common Loon had been loafing in the boat dock earlier. The Pacific Loon was joined by a Red-necked Grebe and the two were often in the same view.

[Pacific Loon is a review species for the New York State Avian Records Committee (NYSARC) and the committee would appreciate documentation from all lucky observers.]

Side view showing the well-defined even demarcation between the dark hind-neck and the white fore-neck. The dark feathering of the crown extends down over the eye. The 'chin-strap' comprised a thin brownish band and was more evident on the left side of the head (above) than on the right (below). At certain angles, the slightly browner square centers to mantle feathers gave a checkered pattern reminiscent of the neat white squares seen in alternate plumage. One can see a hint of this in the photo above. More easily rendered by the camera, the coverts [not scapulars as I originally thought] were sprinkled with white specks. As several correspondents have pointed out, these are indictative of a second year or older bird. This is supported by the lack of obvious pale feather edges on the upper-parts.

Sometimes the bird would raise the feathers on the forehead, creating an odd bulge. This would be flattened just before a dive giving a smooth rounded shape, reminiscent of a cormorant. Arctic Loon is said to have a more angular head than Pacific, but this bird illustrates the problem with such generalizations. The top of the head seemed slightly paler than the nape or forehead, but again this was a subtle feature and less obvious than on other similar plumaged birds I've seen on recent trips to California. The bill was generally held horizontal to the water. The mandibles themselves appear strait, without the upturned distal end to the lower mandible of Red-throated Loon. The bill was steely blue with dark cutting edges and a dark top to the upper mandible, creating a dark tip effect.

A hint of horizontal barring was evident at the meeting point of the flanks and upper breast. This pattern is more striking in alternate plumage and is not seen in Common or Red-throated Loons of any age. The dull red iris is just visible against the dark plumage.

Other features: When diving, the bird tended to throw itself forward, athletically arching into the water. Although Red-throated Loons use a similar action, Common Loons tend to put their head forwards and then slide below the surface.

Identification: With these close and sustained views, separation from Common and Red-throated Loons was relatively straightforward. Separation of Pacific from Arctic Loon (Black-throated Diver) is a little more difficult. The literature often relies of direct comparisons (posture, neck length etc), which are less useful on isolated birds. The following features are most consistent with Pacific Loon.

Here is my best attempt at catching the vent region! The tail is depressed largely obscuring the vent but theredoes seem to be a hint of darker (less shiny gray) feathering wrapping around. Not very conclusive, I afraid!

A crowd of soggy but very lucky birders study the loon. No doubt each is contemplating the opening wording of their NYSARC report!

Here are a couple of reference shots of a 1st year Pacific Loon taken on a recent visit to Morro Bay in California. The broad pale edges to the upper part feathers are very evident. The smooth head shape is very typical of Pacific Loon and contrasts with the peaked forehead of the Captree bird.

Many thanks to Pat Lonergan, Mary Gustafson, Julian Hough, Tony Leukering, Martin Reid and Kevin McGowan for comments on this bird and Pacific Loon identification in general.

Images and page layout copyright of Angus Wilson©2003.
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