Re: how we knew it was a Thrush...
Birders look for size, shape, color, posture, bill type and any obvious field marks. Another useful clue is found in the habitat in which the bird is seen and sometimes in its location within that habitat ( high vs low; on the ground or in a tree etc ). In the case of this bird, the shape, the overall brownish-grayish color but especially the spotting on the birds chest all immediately pointed to a Thrush.
Thanks for the query and to all for a stimulating thread.
42, yes and angioplasty...Bucky Katt