Feral Pigeons and Walnuts

I am a bird lover (and I love my wife, too).
On the top floor of our house is a small room that incorporates our spare bed (on which I paint from a kneeling position), my wife’s modern computer, and my own computer, which is really a sophisticated word-processor and unconnected to the net.
We are very cramped in this room, but it is our joint den, and very cosy.
Outside old inward-opening windows (a real curse, needing drainage channels and a tube to a bucket to deal with wind-blown rainwater) is a wide sill.
Above this sill I suspend a contraption for feeding birds with sunflower seeds.
Beside the normal run of blue tits and great tits came feral pigeons that ate both the dropped seeds and even their husks. They made a noise and a mess, were plain greedy, and deterred the other birds from enjoying a share.
So I constructed a frame of 1 ½” x 1 ½” woodwork on which I attached rows of spikes – used to keep pigeons away from the perching places on public buildings and monuments.
After adjustments and filling gaps with yet more spikes, the feral pigeons tried for seed and failed.
But the husks fell, started to fill the frame, and began to congeal and rot.
So I scraped and vacuumed to keep the sill hygienically clean. This was a painfully spiky and nuisance job.
It then occurred to me that if I lifted the gutter side of the frame, rainwater would run beneath it and wash the detritus into the gutter and then away.
I was eating a walnut when thinking of a simple method to raise the woodwork with something rot-proof and sightly that would be impervious to the elements. So I used broken walnut shell to do the job.
Walnut shells seem to be indestructible, and easy on the eye. So the broken shells were replaced with intact half shells.
Now the rainwater washes away the husks from the front of the raised frame, and it looks nice, too.
With this success I have hung a Niger seed dispenser above the sunflower seed one.
So now goldfinches have joined the tit crowd, the sill is clean, and there is neither the sight nor sound of a feral pigeon.