Mrs. Merrick knew she was going to die. She was a Lapsed Catholic, but even as lapsed as she was, she recognized an apocalypse when it ate everyone in sight. Pet owners pounded on the glass of her shop for sanctuary, but she dared not open up and risk the zombies getting in with them. She had work to do.
Zombieism was an exotic strain of bird flu. Scientists knew it because they had isolated the virus. Mrs. Merrick knew it because all of her parakeets had it, and set about devouring her canaries. She only managed to save ten pigeons and her most obnoxious parrot, forcing the flock of zombie-keets into a glass cage. They only ate their own for now, and that meant working fast.
The parrot went first after it repeated her weight. She found the zombie-keets preferred their parrot raw, and so she put out feathers and bits of wing to start, only letting a zombie-keet bite if it first picked up its string and rod.
By Day 3, they only ate if they carried the rod and string appropriately, and if they visually saw her eat.
By Day 6, the zombie parakeets brought her a bagel in return for some pigeon. No matter what she did, she could not condition them to butter it.
By Day 8, she tied the dozens of strings to her arms and had her first successful takeoff. The zombie-keets didn't even attack their prey until she'd had her bagel.
On Day 11, the inevitable happened. A couple of star-crossed lovers smashed in her front window looking for supplies, and pedestrian zombies followed them in. Mrs. Merrick was bitten before she even got out of bed, and she died with a surprising poise. She'd known this was coming. As the infection overtook her, she slipped on her strings and loosed the flock of parakeets.