Inside the envelope addressed to him, but with no return address was a birthday card with a cat on it.
The cat was a ginger kitten that reminded me of Nile. When the card was opened, it played the birthday song, only with cats meowing.
Bow listened, chewed on the card a little, shook it along with the beat of the music, then closed it to silence the cats and handed it back to me.
Afterwards he pointed toward the front door frantically several times, before spelling. "הם לא באו" -- "They didn't come!"
It turns out Bow thought it must be his birthday, if he got a birthday card in the mail today, and he was a little upset that nobody had come to his birthday party. I had to reassure him that today is neither his actual birthday nor the day we set for his birthday party to take place this year. Eventually, he calmed down.
It is hard to explain to an intelligent, literate, but impatient chimpanzee that the arrival of a birthday card in the mail does not necessarily mean that today is his birthday.