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Puerto Penasco

23 - 24 January 1999

by Tony Leukering

John Vanderpoel, Rich Levad, Peter Gaede, and I visited Puerto Penasco, at the top of the Sea of Cortez, this past weekend (23-24 Jan '99).  The focus of the trip was gulls, but we did some seawatching and shorebirding also.  The highlight of the trip was a potential first Mexico record of ICELAND GULL (ICGU).  We found the bird, a Basic I-plumaged bird, flying around at the mouth of the harbor and, later, on the rocks south of the fish stores.  The bird was a classic Basic I ICGU in most all respects, with the only things a little less-than-classic being the somewhat short wingtip projection beyond the tail and the tail pattern.  However, we believe that those aspects of this bird are within the range of normal variation for the species.  The tertials were perfect for ICGU, with marbling/loops running throughout the interior of those feathers (unlike the more solid pattern of Thayer's Gull).  We found the bird in the AM on the 23rd and refound it late in the afternoon the same day.  We returned to those sites on the afternoon of the 24th, but did not see the bird again.

Other sightings of note:

Sooty Shearwater - 1 noted at the booby feeding frenzy noted below.

Black-vented Shearwater - at least 7 as above.

Black Storm-Petrel - 1 seen beyond the booby swarm.

Boobies - we saw >800 boobies, mostly Browns, at an amazing feeding frenzy that included very few other species.  This was east of Estero Marua (east of Puerto Penasco) and just offshore.  The Sooty came into the madness and dove repeatedly from the surface, but the Black-venteds didn't seem to like all the madness, though were obviously attracted to the commotion, as the circled it repeatedly.

Reddish Egret - 3 adult dark morphs were at Estero Marua.

Cinnamon Teal - 1 male with a flock of 20 Green-winged Teal that were apparently migrating north, as we saw them swimming on the Sea of Cortez/Gulf of CA and then flying up the Gulf.

Laughing Gull - 2 birds in Def.  Basic plumage at the fish stores.

Thayer's Gull - 3 birds, 1 in Basic II and 2 in Basic I plumages in town.

Iceland Gull - see above.

Western Gull - 3 birds, 1 in Basic I and 2 in Def.  Alternate (performing minor courtship activities)

Glaucous-winged Gull - 3 birds, 1 each in Basic I, Basic II, and Def.  Basic plumages.

Herring x Glaucous Gull - 1 bird, probably of this parentage, in Basic I plumage in town.

Herring x Glaucous-winged Gull - 1 bird, possibly of this parentage, in Basic I plumage in the harbor.

Tree Swallow - 2 in active migration north at/near Estero Marua.

Violet-green Swallow - 2 at Quitobaquito in Organ Pipe Cactus N.M., AZ, that strayed across the fence into Sonoran airspace.  Presumably these are migrants on a layover?

Le Conte's Thrasher - I know they're supposed to be here, but I'd only seen them once before seeing the two across the main road from the old sewage ponds.

Dark-eyed Junco - Three forms found at the old sewage ponds: Pink-sided (the most numerous), Oregon (a few), and, amazingly, Gray-headed (1).  John V.  and I both observed the strongly-demarcated rufescent back, gray head, black lores, gray sides, and underparts gray - dark gray on chest gradually becoming very pale toward the legs.

As soon as possible, I will endeavor to get pix of the ICGU posted on a web site for your perusal.


Tony Leukering
Colorado Bird Observatory
Brighton, CO