ML118245981

Age and sex

Immature Unknown sex - X

Observation details

A young bird on Platform Ellen first spotted by Ryan Seppala. Photos and details to be submitted to the CBRC. [TAB comments] There was disagreement among the trip leaders regarding both the color of the bill (currently, the only known diagnostic character for distinguishing this species pair) and the identification of this bird. I believe I am in the minority with my opinion, which I present here. In the field, the bill appeared to be dull in coloration, and given that we were at the closest 50 meters from the rigs, and only able to view the bird through binoculars, I don't feel I was able to accurately describe the color of the bill from my views beyond dull with some subtle coloration (i.e., not the uniform gray of a true juvenile, nor the bold yellow or orange of an adult). In reviewing my photos, the majority (roughly 80%) of the bill appears dull, with a contrasting (pure) yellowish tip. In a number of photos, particularly those looking down on top of the culmen, the bill appears drab, and almost grayish without any hint of color (except for the tip). In photos of the bill in profile, however, the basal portion of the bill still appears drab, but with a suffusion of warmer coloration. To me it appears to be a very dull orangish color (and not yellowish green, as others described it) that contrasts with the yellowish tip, and this is what I would expect to see on a Nazca Booby that is transitioning from the gray bill of the juvenile to the bright orange bill of the adult. I do not think that this color would be seen on a young Masked Booby transitioning from the gray bill of the juvenile to the yellow to yellow-green bill of the adult. In addition, the central tail feathers are extensively white, a trait that is suggestive of Nazca Booby (though a small percentage of Nazcas lack this feature, while a small percentage of Masked Boobies show this feature).

Technical information

Model

Canon EOS 7D Mark II

Lens

EF100-400mm f/4.5-5.6L IS II USM

ISO

500

Focal length

400 mm

Flash

Flash did not fire, auto

f-stop

f/5.6

Shutter speed

1/1000 sec

Dimensions

2298 pixels x 1567 pixels

Original file size

2.13 MB