In order to accurately describe what we're looking at, I had to make up some terms.
In most (all?) PFGOs, the area of the upper mandible between the nostrils and the hard, distal bill cap is almost entirely pink. The corresponding parts of the lower mandible are generally pink, as well. I call this the band.
There is usually (though not always) some pink reaching back from the band toward the base of the bill. It starts at the lower edge of the upper mandible and stretches up and back to varying degrees. There may or may not be pink on the corresponding part of the lower mandible. I call this pink area the stroke.
In addition, there may or may not be areas of white on the black part of the bill, especially at the edges. There may also be some white at the distal end of the band.
I've given names to the birds so we can be clear what we're talking about. At first I just gave them names of the Greek alphabet, but then I figured hey, they're not from around here -- so I also gave them names in the Greenlandic language meaning "one", "two", etc.
I assigned the name-letters in order of appearance in the area, so that "Alpha" is the first bird we can identify, "Delta" the most recent.
The "type photos" for each individual are the largest, clearest images I could find. For Beta (Malik) and Delta (Qajuusat), these pictures are phenomenally detailed, comparable to having the birds in the hand. I've tried to find both right- and left-side views for each individual, but they're only of equal, high quality for Delta.
Type date and location: Peace Valley, Bucks County PA; November 18, 2012.
The distinguishing feature on this bird is the very thick stroke, reaching almost all the way back to the base of the bill. On the left side, the stroke widens out into almost a "Y" at the end.
Type date and location: Deer Path Park, Hunterdon County NJ; December 24, 2012
The stroke is somewhat uneven. It does not extend to the base of the bill. There is no stroke on the lower mandible, at least on the right side. There is a fairly prominent white dot on the distal side of the band.
On the left side, there is a long white mark of some kind at the base of the bill.
The lower edge of the upper mandible is straight, with "teeth" that may be visible.
Type date and location: Shady Brook Farm, Yardley-Newtown Rd, Bucks County PA; 01/17/2013
There appears to be no real stroke at all, only a band. The upper mandible has a number of white marks, which may be scrapes or abrasions. On the right side, a bright white line is visible at the proximal top of the bill, and another, vertical one is at the point where the beak joins the head. The area where the stroke occurs on other individuals has irregular white or grayish marks.
I have found no good pictures of the bird's left profile.
Type date and location: Marshals Pond, Ocean County NJ; 01/20-22/2013
The stroke is very thin, but shows up well even in more distant shots. The mandibles gape apart proximal to the nostrils, in approximately the area of the stroke. The bill has few white marks, though there appears to be a white dot in the most distal part of the band.
Type date and location: Overpeck County Park, Bergen County NJ; February 2&4, 2013.
On both the left and right sides the stroke does not extend beyond the nostril. The stroke is wider on the L side, reaching up almost to the nostril. The serrated edge of the upper mandible may be visible on the L side.
On the Right, the stroke is thinner, barely thicker than the "lip". There are white scrapes or marks on the R side which give the impression of extending the stroke.
On neither side is there a white dot at the distal end of the band.
Updated on February 11, 2013. Email me if you have additions or corrections. All photographs are copyright @ the photographers.