IDAHO BIRD RECORDS COMMITTEE
RARE BIRD REPORT FORM

SPECIES:

Pomarine Jaeger

HOW MANY:

1, adult light morph

REPORTER:

Cilff Weisse
4125 Beaver Springs Rd.
Island Park, ID 83429
208-558-7789

REPORTER EMAIL:

cliffandlisa@octobersetters.com

OTHER OBSERVERS:

None

DATE REPORT PREPARED:

11/6/07

DATE SIGHTING OCCURRED:

10/8/2007

LOCALITY OF OBSERVATION:

At the Middle (Rt 33) Rexburg Exit on US 20 near Rexburg, Madison County. The bird was west of the highway.

HABITAT:

Farm fields

CONDITIONS:

Time of observation about two minutes. Distance ranged from abut 150 yards (without binocs) to about 1/4 mile.

Conditions:

Sunny with no wind
First morning of good (sunny and calm)weather after several days (3) of rain/wind.
Sun behind observer

Binoculars used were Nikon Premier LX 10 x 42

DID YOU TAKE NOTES?:

Yes, another day after the observation

DID YOU CONSULT FIELD GUIDE OR OTHER REFERENCES?:

Yes, another day after the observation

WHAT GUIDE(S) OR REFERENCE(S) DID YOU CONSULT?:

Sibley Guide to Birds of North America
Peterson Advanced Birding

DESCRIPTION:

Transcript of field notes written 11/9/07:

Overall impression was of a very dark backed gull. Very dark brown, almost black, upperparts. Under side of wings dark. White belly with obvious breast band across upper breast. Breast band was easliy seen at a distance and was definitely heavier than a wash of color (appeared brown) but also did not appear solid or cleanly demarcated. No tail streamers were seen and no other significant plumage details were observed. Flight style was very much gull like. It was in close proximity to a Ring-billed Gull and flew in identical fashion with deep slow wing beats. Wing span was similar to Ring-billed Gull in direct comparison. During entire time of obserbvation it flew gull like, even while harassing the RB Gull, and never flew with fast wing beats like a falcon.

BEHAVIOR:

Flying behind Ring-billed Gull when first observed. The Ring-billed Gull turned and interacted with the jaeger at one point, then continued on with the jaeger in pursuit. Pursuit seemed somewhat leisurely or unhurried.

HOW AND WHEN DID YOU POSITIVELY IDENTIFY THE BIRD, AND WHAT CLINCHED THE IDENTIFICATION FOR YOU?

While driving south on US 20 I initially thought the birds were Northern Harriers, because they were interacting with each other, then I noticed that they were gulls as they continued flying SW. While continuing to watch them I realized that one of the birds was very dark on the back, appearing almost black. I suspected it was a jaeger so I pulled over and got my binocs out. I watched the bird flying for at least one minute during which time it circled several times with the RB Gull. When it circled the upperparts were in full view and there was no visible contrast between the mantle/coverts and flight feathers. During one circle I was able to see the breast band, confirming that it was indeed an adult jaeger. I suspected it was a Pomarine because of the flight style and became convinced when I read about mantle shade in Advanced Birding.

HOW DID YOU ELIMINATE SIMILAR SPECIES, AND WHAT WERE THEY?

There are no species that this individual could be confused with except other jaegers or skuas. Skuas are not white below and don't venture inland. I eliminated the jaeegers as follows:

Long-tailed has light gray mantle/coverts contrasting strongly with darker flight feathers. Flight is bouyant and tern-like, not gull like. They also have considerably smaller wing span than a Ring-billed Gull.

Parasitic Jaeger is similar but typically has paler mantle/coverts that contrast with black secondaries and primaries. Parasitic also flies falcon-like, especially in pursuit, not with the slow deep gull-like wings beats of the individual.

I'm basing the ID mostly on flight style and color of upperparts. While this was not a long or ideal view of the bird I feel that the field marks observed, including flight style, eliminate other jaeger species.

EXPERIENCE WITH THIS SPECIES (AND SIMILAR SPECIES):

I've only seen three jaegers prior to this sighting, one of each species. I spent hours observing the Long-tailed both perched/walking on the bank and in short flights chasing gulls or terns. The Parasitic was observed for a short time but at close range (20 yds?) and the characteristic falcon-like flight was very obvious, so much so that I thought it was a Peregrine upon relocating it at a distance of 300 yards or more. Previous Pomarine sighting was in flight only and lasted for about 10 minutes

GENERAL BIRDING EXPERIENCE:

15 years, at least 10 seriously.

WERE PHOTO(S), VIDEO, AND/OR AUDIO OBTAINED BY YOU?:

None