#53-B-06

IDAHO BIRD RECORDS COMMITTEE

RARE BIRD REPORT FORM

SPECIES:  Parasitic Jaeger

HOW MANY:  1

REPORTER:    Cliff Weisse,  4125 Beaver Springs Rd. , Island Park, ID 83429

208-558-7789

REPORTER EMAIL:  cliffandlisa@octobersetters.com

OTHER OBSERVERS:  Lisa Weisse

DATE REPORT PREPARED:    10/9/06

DATE SIGHTING OCCURRED:    9/4/04

LOCALITY OF OBSERVATION:

West end of Island Park Reservoir near mouth of Sheridan Creek.

HABITAT:  Lake

CONDITIONS:  Binoculars were Nikon 10 x 25 Mountaineers.  Distance varied from 20 yards to several hundred yards.

DID YOU TAKE NOTES?:   No, not at all

DID YOU CONSULT FIELD GUIDE OR OTHER REFERENCES?:   Yes, later the same day

WHAT GUIDE(S) OR REFERENCE(S) DID YOU CONSULT?:  nSibley Guide to Birds of North America

DESCRIPTION:   Juvenile jaeger.  This individual had buffy fringes to feathers of brown upperparts.  uppertail coverts were barred but appeared rusty/rufous from a distance.  Upper surface of primaries had white patch at base.  In addition white shafts were noted on primaries but short duration of sighting made counting the exact number impossible.  My impression at the time was that there were at least four white shafts, definitely more than two.  (this field mark was observed numerous times on a Long-tailed Jaeger that had been present for some time immediately prior to this sighting)  Bill was seen only briefly during pursuit but was slender without pronounced gonys, but I didn't see it well enough to evaluate the structure other than that, IE nail length, etc.

BEHAVIOR:    When this individual was first observed it flew past our boat at about 20 yards in pursuit of a Franklin's Gull.  It was actually nipping at the tail with its bill.  They flew about 50 yards past us, turned back, and flew past again at about the same distance.  When the bird made the turn to head back towards us the rusty/rufous color was clearly seen on the uppertail coverts, which contrasted lighter than the tail and back.  During this pursuit several Franklin's Gulls were flying behind the jaeger nipping at its tail.  When the pursuit was terminated the haeger flew along the shoreline and gulls, mostly Franklin's and Ring-billeds, were flushing at its approach.  It made passes at a few birds and was lost in a cloud of birds.  When I again picked it up it was several hundred yards away and flying low over the water, quartering away from us.  At this time I pointed it out as a juvenile Peregrine Falcon.  I recognized it when it banked and I saw the white flashes in the primaries.

  This falcon-like flight was during direct flight, not near other birds, and not while actively chasing other birds.  It was lost soon after it banked and was never relocated. 

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

I tentatively identified the bird based on the rufour tones to the uppertail coverts not typically shown by other jaeger species.  The clincher for me was that it flew falcon-like, so much so that I mistook it for a Peregrine.  Although I was aware of this flight style "field mark" prior to this sighting I was not thinking about it during the observation. 

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

Other jaeger species are the only ones likely to be confused with Parasitic Jaeger.  Long-tailed Jaeger does not show the rufous/rusty tones to the uppeparts and has only two white primary shafts.  Flight style is totally different, bouyant and tern-like.  Pomerine Jaeger is larger, bulkier, has a large gull-like bill, and has flight style similar to a gull. 

EXPERIENCE WITH THIS SPECIES (AND SIMILAR SPECIES): 

 This is the third jaeger I've seen, all in Idaho.  I observed a juvenile Long-tailed Jaeger for extended periods on five days between 8/28/04 and 9/3/04 so I was very familiar with that individual recently and had been studying field marks for jaegers extensively just prior to this sighting.  The only other jeager I'd previously observed was a Pomerine.  Flight style was very different and very gull-like. 

GENERAL BIRDING EXPERIENCE:   12 years, 9 serious

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

None