ID? Age?

[Arthur Morris]

This loon was photographed this morning at Bolsa Chica Lagoon, Huntington Beach, CA.

Is it a Pacific Loon? Is it an adult or a juvenile?

[Dan Brown]

I believe this is a Pacific Loon, the field marks for me are the bill shape, darkness of the plumage and the chin strap. I further think it is a juv. as it has a lot of light feather edges. The neck is dark for a juv. but the light feather edges fit. My two cents! Nice shot BTW, I haven't seen the species all year in CA!

[Chris Sloan]

I agree with everything Dan said.

[Paul Guris]

I'm with Dan, though I think the darkish neck might be due to the bird's position. The bird is turned slightly towards us, so the feathers on the side of the neck are compressed. I think the "lighter" areas on the back of the neck and head are actually due to pale feather bases showing, which wouldn't happen when the dark tips are compressed together.

The other contender is Arctic Loon, though my extensive experience consists of one bird seen on Attu in 1987. Off the top of my head I think there are several things that are wrong for the subspecies expected in California. The chin strap isn't normal for this species, the bill appears too thin, and there is virtually no white showing above the waterline along the sides of the bird, especially at the rear. Saying that, Arctic vs. Pacific is a tough ID and I don't know that I'd want to call an out of range Arctic from one photo. Here's a link to an Arctic Loon photo (a.k.a. Black-throated Diver) from Korea.

[Arthur Morris]

Thanks all. I was thinking young Pacific and did not even remember to think about Arctic. How does Pacific differ from red-throated in the same plumage? I am remembering that red-throated has a slimmer bill that points upwards a bit...

[Paul Guris]

You are correct on the bill. Red-throated's upward look is caused by the fact that the lower mandible angles up near the end as well as having the bird often holding its bill above the horizontal. This can appear exaggerated because Red-throated has a smaller head. In flight, they can look downright snaky.

On the dorsal side, the Red-throated should appear speckled rather than scalloped. It does not show perfect pale edging to the entire feather tips.

The dark edge on the side of the neck should be mostly grayish, not as sharply demarcated, and doesn't come as far forward as on Pacific. (On adult Red-throated, it's even farther back on the neck.) I also believe the neck strap is kind of unique to Pacific.

Finally, color may be a bit tough to assess accurately, but your bird seems to have a fair amount of brownish tones in it. I wouldn't expect this in Red-throated.

[Myer Bornstein]

Checked in my new Stokes guide definitely a first winter Pacific Loon

[Arthur Morris]

Thanks a stack Paul and Myer. Myer, see you on Friday!

[john jackson]

Paul's memory of Arctic Loon/Black-throated Diver is good. Another feature is that Pacific tends to have a dark line across the vent area (not often seen!). Black-throated/Arctic is a larger heavier bird. Arctic is also darker in colour; this difference is particularly noticeable on the rear neck.

Recently in Finland, birders were visiting a Great Northern Diver/Common Loon (a rare bird in Finland). Later inspection of photos revealed that the bird was swimming with Finland's first-ever Pacific Diver/Loon. No one noticed the rarer bird at the time and it was gone when people checked after the event. Anyway, the photos provide a rare opportunity for side-by-side comparison of Arctic and Pacific.

http://www.pekkakomi.1g.fi/kuvat/027...1110_005_f.jpg