The Mara Crossing, By Ruth Padel

The question of migration, and all its implications, pulls us gently through this thoughtful and often really quite magical mix of prose and poetry, in which Ruth Padel focuses on the instinct to move. What impels gazelles and zebras and wildebeest to make a terrifying and often fatal crossing over the crocodile-infested Mara river? What keeps certain breeds of birds returning every year to the same place, many thousands of miles away, when equally suitable conditions exist nearby? And what makes people leave behind family and friends to encounter hostility and strangeness in a foreign land?

As the final poem in the volume, "Time to Fly", shows, the reasons are many and varied: some are biological imperatives, some financial, some emotional. But given that we are made up of cells that migrate, it shouldn't be too surprising that animals and birds and human beings should feel the compulsion to migrate too.

And yet, however primeval an instinct, and however much migration may benefit us, or in some cases even protect us, it's still something that we are deeply uncomfortable with; an act or impulse we often view with suspicion.

What is just as fascinating as Padel's central theme is the insight that she also gives us into poetry, or rather, into the creation of a poem. By setting out her stall in prose, she can sell us the essence of the poem that follows. In "The Ampullae of Lorenzini", for example, you might not know that the line "Who doesn't long/for gel-filled pores/somewhere –/and under your top lip would do ..." refers to the physiology of sharks, without having read the previous passage. Or that "The Mission" may be a poem based on the fourth book of The Aeneid, but is also inspired by thoughts on migration as a "violent loss"; on what occurs when migration becomes invasion.

This isn't to argue that poetry necessarily requires a prose explanation, but rather to emphasise the relationship between the two. As Padel ponders the history of the American railroad as a consequence of the Industrial Revolution, she muses on the symbol of loneliness it became as it took workers away from their families, and she recalls one song by that "frail son of a railroad worker", Hank Williams. She doesn't need to turn this musing into a poem – the poetry is already there, contained in the prose.

From famous dustbowl images of migrant workers to the fall in long-distance migrant birds coming to Britain; from contemplating her own move to a smaller house now that her daughter has left home, to the fate of the "Wandering Jew" and the Irish diaspora, Padel ranges over the kinds of migration that once took place numerously and that now leave off, sometimes altogether, for good and bad reasons. Ultimately, home is what we are searching for; "home and migration are two sides of the same coin". What that home is may change with the seasons. The need for home, though, is constant.