What do you think of my poem?

This is pretty good. I might change a few things:

Wanderers of the seas 'wanderers' could be anyone/anything/any animal -- maybe 'inhabitants' is a better word choice here?

Mistake our plastics for food.

If only they could understand.

Instinctive – the chicks’ beaks

Plaintive, upheld,

Call for vital sustenance.

Instead – the head of a

Long-forgotten toothbrush,

The hand of a child’s doll.

This next stanza is a tad jaded. You're saying toothbrushes and dolls are only purchased to make kids stop crying?

That's a little over the top.

Flotsam and jetsam of modern life,

Bought to stifle

Clamouring cries of our own offspring,

Impatient for the latest fad.

Many miles from the city,

Our rubbish is transported,

Washed out to sea.

Tragic circles of plastic debris,

Gathered in the gullets and the gizzards of the gulls.

The alliteration in the line above is good but maybe also a little over the top. Maybe one 'g' word too many.

Inscribed by fragile feathers,

Bones of wings that never had a chance

To exult on the soar of an updraft.

Overall, this is a pretty good effort. Don't know how old you are but this is better than a lot of the poems I read on Yahoo.

I think that this eco-poem is under-researched, as you would understand from it, that it is now common practice to dispose of rubbish at sea, whereas Annex V of the MARPOL Convention, which came into force on December 31, 1988, "totally prohibits of the disposal of plastics anywhere into the sea, and severely restricts discharges of other garbage from ships into coastal waters and "Special Areas".

Far more likely sources are passing ships illegally dumping rubbish overboard and debris left by beach-goers.

You also mention "Flotsam and Jetsam". From looking it up on Google, I gather that Flotsam is (unintentional) wreckage from a ship or its cargo, whereas Jetsam is cargo intentionally thrown overboard in time of distress to save the ship, so both terms involve shipwrecks.

In the last stanza, you mention gulls, although the title of the poem includes the albatross. It would have been more effective to pick one bird and stick with it.

Very real expression about a throw away society.

Nice and keep writing

very nice indeed