Fortunately, the little chickens soon had the help of the Washington Humane Society, which found them a cozy place to stay with the kind folks at Poplar Spring Animal Sanctuary in Maryland.
"One of the chicks has an injured leg, but is recovering. The rest are very active and healthy," writes the sanctuary on Facebook. "They are currently being housed in a playpen with a heat lamp in our infirmary until their feathers grow in."
Nine of the birds will live out their days at Poplar Springs, and six will be sent to Peaceful Fields Sanctuary in Virginia.
Mailing chicks is legal under certain conditions, so it's unclear if the ex-boyfriend will face any criminal charges for what seems to be a blatant disregard for the animals' lives.
Chicks are commonly shipped from large hatcheries to supply small rural farms, says poultry expert Richard Brzozowski, but the practice is not without its dangers. In 2012, one thousand baby chicks died, likely after being exposed to extreme heat while in transit with USPS - and such incidents are hardly rare.
"Unfortunately, it's a very common tragedy," Stephanie Bell, from PETA's Cruelty Investigation Department, told CentralMaine.com. "There are serious risks to putting animals in a package and sending them across the country."