The Mara Crossing, By Ruth Padel

Dawn glows through the "geisha fans" of starlings' wings as the writer gazes from her kitchen window: across the pane of her imagination pass migrants of many species, bird, animal, human. She brings to bear on their flocking variety the twitcher's forensic and delighted eye, the lens of science, the totalising frame of history and the traveller's testimony. Ruth Padel's vision in this beautiful, haunted book is of a world of unfixity. Her lens focuses down on the individual mutating cell; vaults to aerial views of wildebeest crossing the Mara River; submerges to film "the planet's largest migration" in the nightly rise and fall of billions of jellyfish.

The Mara Crossing is a vertiginous compendium, a prodigy, a book of wonders: it is Montaigne's and Darwin's 21st-century child. "Migration is part of the restless... self-renewing nature of all life, in creative tension between the fixed and the wandering." I recalled Montaigne's meditation on the instability of observer and world, the attempt to fix nature being "as if one should go about to prison the water".

The Mara Crossing is composed of alternating prose and poetry, responding to the variegated character of her subject. Padel asks us to read her prose as commentary, as if we were listening to a poetry reading. But the prose achieves far more than this – and the poetry, occasionally, less.

In the pulses of prose, Padel moves easily between the manners of diarist, meditator, teacher, travel reporter, science aficionado. Her mind wings from Dante via Darwin to a house-move with her daughter; she presents a magpie intelligence pleased with sparkling oddments, like the medieval belief that swallows hibernated at the bottom of rivers. On birds, Padel is always sheerly brilliant. "Petrels skim the waves, sipping planktonic food from the surface and seeming to pat the water with first one trailing foot then the other." Those verbs, skim, sip, pat, have a precise perfection, scarcely bettered in the poem, "Children of Storm": "hunting microscopic prey/ with dangling toes/ as if they walked/ over whipped-and-peaking waves".

Within the volume's DNA coil narratives that unfold with exuberant brio. The damson narrative begins with her daughter plucking fruit in Padel's garden ("Once handled, they change colour forever"), shifts to consideration of the fact that there's no such thing as a "native" tree, for trees migrate, and determines in the thought that wild hawthorn berries, borne in the guts of bears, mutated into the apple. I was reminded here of Milton's account of the Creation in Paradise Lost: "The grassy clods now calved... The swift stag from underground/ Bore up his branching head".

Milton paused in his tragic story to celebrate the ecstasy of being and becoming. Padel's Ovidian celebration likewise inhabits the realm of requiem; wonder connects with pity and terror.

Modern man's place in the epic cycles of migration troubles the ethical heart of The Mara Crossing. Humans "want more than we need"; "our migrations are inextricably mixed with trade, invasion, conquest and empire". Padel quotes Goya's handwritten "I saw it" on the Disasters of War etchings. Perhaps the most eloquent testimony is a found poem-within-a-poem: "the note/ in a dead boy's pocket – Excuse me, this is the end,/ sorry to my family in Bassada" ("Ghost Ship"). This fragment is lodged in the searing penultimate section: migrant monologues, voices in transit, coercing "Compassion – and beyond that, empathy".

Stevie Davies's most recent novel is 'Into Suez' (Parthian)