Field Museum Musings - Kodak Gray Scales and Such

A few notes from a visit to Chicago's Field Museum last week.

I'm currently working on a project that requires quite a bit of data collection from both live birds and museum specimens. One component to this data is measuring gray tones. Now a standard for measuring gray colors on the upperparts of gulls, the Kodak Gray Scale has steps 1-19, with 1 essentially being white and 19 black. My objective with measuring these gray tones is to compare them to current values given in the literature. In particular, I would like to verify (or contradict) what has been recorded by previous workers. 

The two specimens below are Western Gulls. The left bird is the paler, northern, race: L.o. occidentalis. The right specimen is the darker, southern, race: L.o. wymani. One challenge is to come up with an "average" for what is seen on the upper mantle (lighter) versus the mid to lower scapulars (usually darker). The other challenge is determining whether there are two noticeable generations of feathers. Newer feathers will generally appear darker (in adults) and older feathers should have suffered from some fading, and hence paler.

For the specimen on the left, I averaged it to be a KGS value of 8.5
For the specimen on the right, I averaged it to be a KGS value of 10

Another long-term project of mine is evaluating Iceland Gull specimens collected from the presumed ranges of the various subspecies during the breeding season. Just for fun, here's a spread of dark-end thayeri, to pale kumlieni. At some point, I'll find some time to post on my progress in this endeavor.

And like most of my visits to any gull collection, I usually find myself distracted by all the toys. Pictured below is a 1st cycle male Great Black-backed Gull (New Brunswick, November) and a 1st cycle male Little Gull (India, September).

A special thanks to Ben Marks for allowing access to the gulls here, again! The staff from the bird division at the Field Museum is an incredible resource.