This next one is clearly a crap photo, but does show the existence of at least one narrow streak on the rump - and the patchy orange/white colour to that area. Not as useful as DNA from poo, but prettier.
A third trip to Salthouse paid dividends when the presumed Stejneger's Stonechat finally came close enough, and in good enough light, to photograph properly. What a cracking bird! Now that poo has been collected, we can live in hope of a confirmed identification.