Wood Thrush -- Singing Behavior

I am blessed with thrushes in my woodland yard.  Eastern Bluebirds have just fledged their first brood from one of my nest boxes.  Migrating Swainson's Thrushes were singing a week ago while I planted my hummingbird garden and I spotted one this morning, resting on a limb before dropping to the ground to forage.  Wood Thrushes are singing all around the yard daily, establishing breeding territories.

The habitat here is perfect for nesting Wood Thrushes--shade, shrubby understory, moist soil and leaf litter--all contributing to an attractive habitat for nesting and raising young.

The thick foliage often makes it very hard to find a Wood Thrush even when it is singing right in front of you. (It also offers poor light for early morning photography.) Luckily they often fly from perch to perch while singing and that's when you can sometimes locate them for a good look.

Yesterday morning, it was movement of a different kind that caught my eye and allowed me to locate my singing thrush.  He was flapping his wings vigorously, then stretched his neck, producing his beautiful flutey song.  This was followed by another series of wing-flapping while dropping down onto the limb on his stomach, straddling his legs on either side of the limb, remaining there for a few seconds, then bouncing back up again to sing another refrain of his song.  

He repeated this sequence numberous times--a phrase of his song, followed by wing-flapping, down to his stomach, up again and another phrase of his song,  This observation helped to explain the seemingly long pause between phrases.

I have checked Birds of North America for this behavior and could find nothing that resembled it. I eliminated "brood patch" related behavior because the female is believed to incubate alone.  My thoughts were these possibilties:  scratching his belly, mating display, pre-coital practice (if there is such a thing), energy discharge.

I am interested in what others may know or speculate about this behavior or if you know of this behavior occurring in other species.  

There is always something new to discover while watching bird behavior.  May is an exciting month for bird activity.  Keep your eyes open and ears tuned in!

More about thrushes on this blog:

Wood Thrush
Eastern Bluebirds
Hermit Thrush