Thanks to the several of you who replied,

It is, in fact, a Spotted Sandpiper. I was fooled/didn't know about the
fact that they don't have spots when in non-breeding. Someone asked "was
it bobbing?" and I don't know. I was focused on getting a photo of the
Black-Necked Stilt and didn't really think about "that other bird in the
frame". That picture was taken from a boat on the Rio Ameca that was
moving downstream and under power ... so it was "grab the photo when you
can" ... !
- thanks again, Jim

Quoting jimbetz at jimbetz.com:


> Hi,

>

> I'm having trouble with the ID for the "sandpiper" that is in this picture.

> I think it is either a Baird's or a Solitary - but am open to other

> suggestions.

> This bird was seen last week along the Rio Ameca in Jalisco, Mexico (Puerto

> Vallarta area).

>

>

> https://eamon.smugmug.com/Family-pics-from-jim/Birds-and-Stuff-from-Jim/Best-of-the-Best/n-Z9wm3x/Best-of-the-Best/i-NPbd439/A

>

> ... thanks for your help. - Jim