25 September 2014

First Cycle California Gulls

Below is a collection of 1st cycle California Gulls photographed in Half Moon Bay, California in mid-September. All are hatch year birds - some still in complete juvenile plumage while others showing early 1st alternate scapulars. Subspecies unknown.

(1) All juvenile scapulars, a few showing a holy-leaf pattern (a pattern that's been associated with Herrings). The mostly black bill is shown by a minority of birds in mid-September. Band information to follow.

(2) Still entirely juvenile. White forehead. Bill pattern with a mixture of black not uncommon for mid-Sept.

(3) "Cinnamon" type. Pale underparts and chest partially due to bleaching but also plumage variation. Post-ocular line.

(4) Cinnamon type still fully juvenile. Note the characteristic white forehead commonly shown by this age class.

(5) Similar to the individual above, but more black in the bill and some smoky gray 1st alternate scapulars.

(6) Smaller bird showing the famous decurved gape. Large, plain juvenile scapulars.
Size variation is difficult to appreciate in photos, but what is obvious from these images is the immense variation in upperpart patterns and coloration.

(7) A bigger and darker Herring-sized bird. A few dark gray alternate scapulars mixed in. Note the long-winged look.

(8) Moderate post-juvenile scapular molt. More typical plumage aspect. Blue-gray tibia can be shown at this age.

(9) Longish bill, straight and skinny, with typical two-toned pattern. Moderate scapular renewal. Neater lesser/median upperwing coverts.

(10) Large individual with larger bill and head proportions (male?).  Upperparts more worn than average.

(11) Small bill. Variegated look to upperarts becomes more common as the season progresses. Classic anchor pattern on the lower scapulars. Replaced upper tertial?

(12) Very plain greater and median coverts. Note the dark post-ocular line. Undertail coverts plainer than most Herrings.

(13) A darker cinnamon type with smoky gray post-juvenile scapulars. Matching some Western Gulls in size. Massive.

(14) Extensive post-juvenile scapular replacement. Variegated and dark-gray scapular centers advanced. A few renewed lesser upperwing coverts and a renewed greater upperwing covert. Undertail coverts generally not as neatly barred as Herring. Lower hindneck blotchy with a heavily greased look.

Overall, 1st cycle California Gulls have upperwing coverts that are weakly patterned and not as neatly shaped as similar-aged Herrings. Their bills are mostly straight with little expansion to the gonys. By early October the bill pattern is two-toned on almost all individuals, but some birds can exceptionally retain a mostly black bill into late October. On average, the species appears shorter and smaller than Herring but slimmer towards the rear with longer wings.