They're not dust-bathing or spreading their wings. They're just lying
there, neatly tucked in, as if simply having a nice quiet rest on the
lawn. They make no movement whatsoever, to the point where Ray wasn't
certain about what creature he was seeing this morning. He even
considered some frightened rabbit or hare because unlike me, he hasn't
seen them do this before. There is no ants' nest, no nothing to be seen
other than dozy pigeons. Occasionally, they get up, move about a bit
and lie down again. I've now seen this about half a dozen times and
then the bird gets up and flies off.

I've looked around a bit and found these replies on "birdforum" which is
world wide bird site.

"mourning doves sitting on ground..

I have a male/female couple who've decided to plunk down as if they had
a nest ..problem is they don't have a nest in my backyard on the ground
6 ft. from my back door. Question is do Doves or for that matter any
birds in general like to "take a break" from standing/perching and give
their legs a rest?? "

"I think Mourning Doves are quite similar to the Collared Doves here in
Europe and the ones in my garden do seem to like to take a little sit on
the ground occasionally - I was concerned when I first saw it too as I'd
previously seen one sitting like that after a window strike but although
I don't see them sitting often they do occasionally plonk themselves
down in the grass for a bit, especially in the summer they like to find
a sunny patch of grass and bask there."

"Probably just sunbathing. I see Mourning Doves on the ground with
out-stretched wings regularly in my backyard in Reno. Sometimes they
hold position for 10 or 15 minutes & seem to be almost comatose. The
point of the exercise is apparently parasite control, flushing out
feather mites and other vermin by over-heating".