Jennifer Garner grieving the death of her dog Birdie

Actress Jennifer Garner has announced the death of her beloved 9-year-old golden retriever, Birdie.

"It is hard to know how to write this -- it seems nuts, given the world, to mourn a pet, but since we have shared Birdie with all of you, it only seems fair to let you know of her passing. Birdie let us know [last] Thursday that she wasn't feeling herself (a renowned foodie, Birdie never missed a meal)," Garner, 52, posted on Instagram Wednesday, alongside a gallery of photos and videos of her with her pet.

"We were surprised to learn that, not only was she very ill, she was at the end of her life. The vet told us that dogs often hang on until their person comes home from college and we believe Birdie did just that, so that we could pet her soft ears together and thank her for being the world's best dog," the actress added.

"Birdie loved to be read to, always found her way into a Pretend Cooking Show, and knew just how to give people what they needed (as evidenced by her happy days as a dog therapy team with Mo). She lived a happy dog life and is now in the role she was born to play: angel girl. It's a gift to love and be loved by such a creature as Birdie the Doggie."

Garner shares three children with her ex-husband, Ben Affleck -- Violet, 18, Seraphina, 15, and Samuel, 12.