It seemed that Barny was a-huntin'.
Like a Peeping Tom she spent a lot of time peering -- peering into the trampled grass.
A wee sleekit beastie' was probably crepitating therein, and Barny, it seemed, was channeling the sound with her facial disk.
That's how I read the photos, but I needed confirmation.
Hans Peeter's Field Guide to Owls of California and the West made no mention of barn owls foraging on the ground . . . had we made a discovery?
I sent Peeters a message and he answered . . .
I myself had never heard of Barn Owls foraging on foot, although it wouldn't totally surprise me. This species, however, is so highly aurally inclined in its hunting that infantry-style foraging would be a surprise. Do you have videos? All owls, having pounced on prey and missed, do a certain amount of walking about and weaving their heads from side to side to obtain auditory clues, and all seem to be far-sighted and therefore back up from the point of impact and try to locate the prey by sight.
I quickly googled up a minor paper at http://www.fosbirds.org/FFN/PDFs/FFNv26n3p91-93McMillian.pdf which seems to present pretty good evidence of foot hunting by Great Horned Owls, and it mentions other references (though I couldn't locate any discussion of the phenomenon in Johnsgard, which the author mentions. I am also not entirely convinced that his owls actually ate the tern eggs; eggs of ducks and coots not infrequently turn up undamaged in GHO nests, having slipped out of the bodies of prey brought there. Such eggs are not eaten and become part of the nest detritus.
At any rate, if you can provide more detail or video of the foraging on foot that you have seen, I would very much like to see it.
Then came another message . . .
While ruminating about your pedestrian foragers, I remembered that I have seen Burrowing Owls hunt crickets on foot during the day; of course that species is highly visually oriented and more or less cathemeral, so that's no great surprise. The Eurasian Tawny Owl, however, is completely nocturnal but also forages for earthworms on foot sometimes (I've seen Red-shouldered Hawks do so in the daytime, rather surprisingly, since it's such insubstantial prey for such a large raptor).
The codger was highly gruntled with the finding, and began daydreaming about ways of getting the evidence in video.
The problem was time. The days were getting shorter and we hadn't even scheduled the next trip to Chimineas.
Meanwhile, Craig succumbed to curiosity -- he hauled his live traps to Barny's stomping ground, and though he caught deer mice and pocket mice in the neighborhood, harvest mice were the only mice in the swale.
Once again I poured over the photos searching for some hint of the elusive quarry . . . some telling crumb of evidence in the corner of Barny's beak, like the spurred femora of a Jerusalem cricket.
At last I found some frames of suspicious activity -- Oh my God! -- frames of Barny holding something fuzzy in her beak.
I dragged the jpeg into Photoshop and zoomed in.
The victim was no wee mousie -- but the seed head of annual rabbitsfoot grass, Polypogon monspieliensis.
There was actually a sequence -- Now Barny was gripping a seed head in her talons.
Then she was either eating it or tearing it apart!
Was Barny pouncing on imaginary mice in the form of grass seeds?
And sampling them for texture and digestabilty?
The swale seemed a strange and risky place for Barny to hone her hunting skills, if that is what she was doing.
A predator could explode out of the grass and catch the owl in the midst of her baffling game.
All good things do come to an end, don't they?