ML483237181

Age

Not specified

Sex

Not specified

Observation details

In the field, I called this tern perched on a buoy a Common. Jonathan and I later second-guessed the ID in the car after looking at the tiny photos on our phone and camera screens. Don Gorney's friendly neighborhood eBird reviewer email strikes again. Here are his comments, solidified in this checklist for my future reference. — "The bird in your pics is an adult in molt between alternate and basic plumage (it's transitioning to basic). Field marks that I see that help ID as a Common: - jet black primaries. Forster's will have dark primaries in the fall but will be more grey-black and not jet black - Primary tips that appear to reach to the tail tip and not go beyond - presence of some dark lesser wing coverts, somewhat hidden by scapulars, which forms the "carpal bar" - the white on the face above the bill gape is thin and wedge-shaped vs a bit wider in Forster's - Legs appear shorter than Forster's - takes experience to judge leg size and still easy to get wrong even with experience. More of a soft field mark. - head mostly black except for forehead is better sign for Common as Forster's begin molt in July and most Forster's on Sept 11 in Indiana will only have the black eye spot. But, this is variable so it's a "soft" field mark meaning it is not diagnostic on its own. So, four solid field marks and two soft field marks all point to Common."

Technical information

Model

NIKON D500

ISO

800

Focal length

500 mm

Flash

Flash did not fire

f-stop

f/6.3

Shutter speed

27957/44731201 sec

Dimensions

823 pixels x 584 pixels

Original file size

108.57 KB