You ask such good, thought-provoking questions, Marylynne! Thank you for making me think hard 
I didn’t make any conscious choices regarding low- or high-key in posting these images. For these gulls in particular, I liked their white shapes against the still-gray and brown branches in the background, so more of them turned out to be low key. But I also took a bunch of similar pictures of black cormorants against the sky yesterday, and they are all black & white & very high-key, with just the black cormorants against a white background.
As for color or black and white, I also think that bw is more stripped down and elemental. My general rule of thumb for all sorts of images is to go with black and white unless the color adds something to the image.
What do these images evoke for me, other than what we already mentioned regarding the experience of taking them? They evoke hidden beauty in nature uncovered through photographic magic (e.g., see #1, #3, #5, #8), calm & peacefulness & a sense of floating in air (#9), something innocent and pure going through dark & turbulent times (e.g., #2, #4, #6), reality distilled to its essence (e.g., #2, #8).
After a lot of thinking during the past year about what unifies all the various kinds of images I like making, I recently wrote an artist’s statement of sorts (it’s still a draft in progress): “I love to photograph anything and everything. Immersing myself in taking pictures makes me feel alive and savor the present moment. I want to notice and convey the beauty and nuances of the visual world around me, discover aesthetic value in the mundane, turn the ordinary into extraordinary, capture fleeting moments, use pictures as a means of self-expression, and explore the human condition. In other words, I want to photograph life, as seen from my vantage point.” So in this grand scheme of mine, I think these images fit into all of the points above, except exploring the human condition.
So what are your impressions?