When I got back I went out on the balcony to bring in my clothes. I saw a stray twig on the concrete. When I paused to consider it, I realized a pigeon might have brought it there and... yep, another egg.
Those [expletive] birds.
Now I know why I had to clean so much [expletive] [excretory expletive] off my balcony with the hose this weekend, and why they were hanging around so much. I had to chase them off again and again.
What do I have to do, call in to work and sit at home with a bag of pebbles?
This wasn't going to be a repeat of last time. As no bird was attending the egg, I steeled myself, grabbed a tissue, picked up the egg and launched it over the balcony. It fell straight through the bushes and made a disquieting crack on impact.
It's not a nice feeling to have killed something. But at least it's been done before the birds invested too much time. The eggs from last time were sometimes left unattended, but it would have been cruel to smash them after the birds had been tending them for days / weeks (though the temptation was there), so I decided to grin and bear the frequent droppings. But no more. No more, you foul, rotten fowl.