Who has a crown

Question

Who has a crown but is no king

Proclaimed his vows but has no ring

Tends a garden; rarely eats

Often sings but seldom speaks

Answer 1

It might possibly (though I'm not wholly convinced) be some sort of

monk.

Who has a crown but is no king

"Apart from this general clerical tonsure, some Western Rite monastic orders, for example Carthusians and Trappists, employed a very full version of tonsure, shaving the head entirely bald and keeping only a narrow ring of short hair, sometimes called "the monastic crown" (see "Roman tonsure", above), from the time of entrance into the monastic novitiate for all monks, whether destined for service as priests or brothers." (Wikipedia article on "Tonsure"; emphasis mine.)

Proclaimed his vows but has no ring

Monastic rather than matrimonial vows. Pay no attention to the phrase "ring of short hair" in the material quoted above :-).

Tends a garden; rarely eats

Monasteries usually have gardens. Various forms of self-denial are not uncommon in monastic orders, but I confess that "rarely eats" seems like a weak point.

Often sings but seldom speaks

Monasteries have a lot of religious services, at some of which there will be singing. Some monastic orders (most famously the Trappists) refrain almost entirely from speaking; I think most are rather less chatty than the rest of us. I think, though, that for this one to work we need to take "often" and "seldom" as relative to how often most people sing (rarely) and speak (frequently).

Answer 2

Is it a

A crowned conure(a bird)

As

It has a crown like structure of feathers on its head, sings and can be seen in garden