What does 'themselves' point? Is that 'birds'?

[Boddy]

English Grammar Tests, Elementary Level

ESL/EFL Test #40 "Reflexive Pronouns", question 6

He had watched birds fly by throwing ......... into the air.

(a) yourselves
(b) themselves
(c) ourselves

English Grammar Tests, Elementary Level

ESL/EFL Test #40 "Reflexive Pronouns", answer 6

He had watched birds fly by throwing themselves into the air.

Correct answer: (b) themselves
_________________________

what does 'themselves' point ? Is that 'birds'?

Thanks.
Boddy

[Mister Micawber]

.
Yes
.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mister Micawber