Answer:
Passive. Active voice: People should not cage these birds.
Step-by-step explanation:
The sentence is in passive voice. One of the ways to check this is to see whether there's "by (something/someone)" at the start or end of the sentence/clause. If not, see if it flows correctly if "by (something/someone)" is added to the end. In this case, it does, so the sentence is in passive voice.
To change it into active voice, identify the verb, tense, subject, and object.
- verb: cage
- tense: present
- subject: not given
- object: these birds
Arrange them in order (subject + verb in correct tense + object), with modals (if any) connected to the verb. If the subject isn't given, we usually use "people", "someone" or "something". So "People should not cage these birds."