Stanza 1. In this poem, it’s Thomas’s ‘thirty-fifth‘ birthday. It’s just another ‘sandgrain‘ day in the ongoing hourglass of his life, except that it’s the half-way point in the Biblically allotted ‘three score years and ten’. The ‘mustardseed sun‘, however, the small, orange sun of late October, is more than three-quarters of the way along its downward path to the winter solstice, but there’s still plenty of activity in the world of nature.
The river Taf is running at ‘full tilt‘. The roller-coaster waves are making the sea look like a ‘switchback‘, up and down which the ‘cormorants scud’. Birds everywhere are fully engaged in their animated ‘palavers‘. Yet the ‘bent bay‘ seems like a kind of horizontal ‘grave‘, its beach littered with the remains of what stanza 7 calls the ‘seashore dead‘. Among this is the ‘driftwood‘ which figures in Thomas’s reflections on his life.
The poem was written in the Boathouse which was perched, as if ‘on stilts‘, above the Taf estuary. Thomas lived here for the final 4 year instalment of his ‘wind turned‘ life, his progress through which had so often seemed as stormy, ‘contrairy’ and unpredictable as wind and wave driven ‘driftwood‘. With mixed feelings, then, he both ‘celebrates and spurns’ his birthday. Like the ‘herons‘ which, beak upward, a’spire‘ to the heights and, beak downward, ‘spear‘ any tempting morsel coming their way, Thomas could rise towards greatness in his life and art, but also sink to being the “roistering, drunken and doomed poet.” **
Stanza 2. Thomas compares himself with the birds and fish around him. Their days are numbered as they follow ‘cold, dying trails‘ and ‘work at their ways to death‘. In this they have no choice – they’re ‘doing what they are told‘ – they’re following their instincts and are subject to the unpredictable workings of nature. Similarly, for the ‘long tongued‘ poet, the conclusion of his arduous ‘toils‘ will be an encounter with death as the inevitable ‘ambush of his wounds‘. The tolling of his ‘birthday bell‘, as well as a celebratory, has a funereal tone to it and ‘bell’, of course, suggests ‘knell’. All is not lost, however – ‘herons, steeple stemmed‘, beak upwards, supportively ‘bless‘.
Stanza 3. Continuing the theme of the inevitable downward journey to death we have, typical of Thomas, the autumnal ‘thistledown fall‘ which can also be read as ‘thistle downfall’. The seeds will fall into the ground and die. Finches will fly into the ‘seizing‘ claws of hawks. Ships will be ‘drowned‘ in the sea, and through these ‘sundered hulks‘(stanza 11) ‘small fishes’ will gracefully ‘glide‘ their way, thus providing ‘pastures‘ which ‘otters‘ will hungrily fall upon. In his boathouse, the products of Thomas’s poetic ‘trade‘ are like ‘hewn coils‘. ‘Hewn‘ suggests the axe blows needed to cut away rejected words and phrases, and ‘coils‘ suggests the intricacies of sound and sense needing to be productively unwound. From the boathouse, he can sees the ‘herons‘ that ‘bless‘ but which now, ominously, ‘walk in their shroud‘.
Stanza 4. The ‘shroud‘ of the short-lived herons is the ‘livelong river‘ in which they wade. In that river, resembling a flowing ‘robe‘, is a shoal of ‘minnows‘. They may think they’re offering a ‘prayer‘ for their survival, but what they’re doing is forming a populous ‘wreath‘ in preparation for their approaching demise, compliments of the herons. Far at sea, ‘dolphins‘ will die and ‘turn turtle‘, their ‘dust‘ slowly sinking into the deep. ‘Seals‘ will kill their prey, but the time will come when ‘their own tide daubing blood slides good in the sleek mouth‘ of one of their fellow marine predators. All this the poet ‘knows‘ as, ‘crouched‘ at his writing desk, he ‘slaves‘ at the work fate has allotted him. It’s as if he’s ‘under a serpent cloud‘, like Adam and Eve in the Garden of Eden, when death became the inevitable ‘eternal end‘ for man and beast and bird like. Or, as we’ll see, the ‘serpent cloud‘ might also be the twisting, undulating, writhing and roiling nuclear cloud.
** (Welsh Academy Encyclopaedia of Wales)