The 20-year-old left-footer has been drafted in due to the continued absence of Simon Ainge and Alex Penny and has been granted permission to feature for the Pilgrims in the Emirates FA Cup and Buildbase FA Trophy.
Bird has previous National League North loan experience at Alfreton Town — and United boss Craig Elliott was delighted to land his man.
"With the unfortunate injuries of late, we needed a committed left-sided central defender who can give us good balance," said Elliott.
"Not only is Pierce a good defender but he has very good distribution which is important to how we want to play.
"He comes highly recommended and I appreciate the help in getting the deal done from Neil Cox at Notts County."