On a warm, still day last week, I paddled the contours of the west Cork coastline: deep coves with water so clear I could see straight down to the sand and the shadows cast by fish; hidden sea caves that opened into green, watery gardens, with old trees rooted in the rock and freshwater cascading from the cliffs above; seaweeds of every colour waving up at me from below; and purple sea urchins clinging to periwinkled Old Red Sandstone. No engine, no noise, just my own body propelling the kayak forward, with little to disturb the life in the water, or above it.
This is just the kind of water an osprey hunts – sheltered, salty, with fish – and locals told me these birds have been spotted here over the years. If, like me, you’ve never laid eyes on an osprey, you can conjure it. It’s roughly the length of your arm, but light: it weighs little more than a bag of sugar, and you could cradle it in two hands. But if it opens its wings, it transforms into an imposing bird of prey, with a wingspan as wide as your outstretched arms, fingertip to fingertip.
Its feathers are packed tight and lightly oiled, built to shed water the moment it emerges from a dive. Its legs are bare and scaled, like a lizard’s, and its feet are its weapon: long, curved hooks that can grip a slippery, thrashing fish. It has a dark band across the eye, like a bandit’s mask, beneath a pale crown, and its hooked black beak is made for tearing. Underneath it is clean white, making it hard for fish to distinguish against the bright sky.
Over the water, it can stop dead – unnervingly still – staring at the surface below. When it commits, it’s all in. It plunges feet-first at more than 60km/h, making an audible smack, then hauls a fish up and out as it twists in its talons. In Irish, it’s iascaire coirneach, the tonsured fisherman – that pale crown and the dark stripe through the eye resembling the shaved head of a monk.
READ MORE
Systematic persecution wiped out the osprey as a breeding species roughly 200 years ago, but it never fully vanished from our skies and small numbers continued to pass through on migration between northern Europe and West Africa. Then, in 2023, a naturally returning pair raised chicks in Fermanagh. That same year, the National Parks and Wildlife Service started a five-year reintroduction programme that will release 50 Norwegian osprey chicks in the hope they’ll breed here.
Everything about the osprey is arranged around catching fish; even its breeding is timed to the spring fish runs, which means the bird is only as safe as the water beneath it. And for an illustration of what happens when fish numbers decline, you have to cross the Atlantic.
Chesapeake Bay is the great osprey nursery in the eastern United States, home to nearly a fifth of the world’s ospreys, some 10,000 breeding pairs. The insecticide DDT once nearly finished them off, but they came back. However, now they are starving to death. In a study published in June, led by the biologist Bryan Watts of the Centre for Conservation Biology at William & Mary, 571 osprey nests were monitored. In the saltier waters, the birds were no longer raising enough young to sustain themselves – breeding no better than they had during the height of the DDT era; in some places worse. Ospreys were emaciated. Chicks were hatching, then dying in the nest from lack of food.
The clue is in the salt. Ospreys nesting near freshwater rivers, feeding on catfish and shad, were doing fine. But in the saltwater, where the birds depended on an oily fish called menhaden, they were failing. Over four decades, the menhaden that ospreys carried home to their chicks had fallen by 80 per cent.
Ospreys are “indicator” species – their numbers reflect the health, or sickness, of the water. Menhaden live by straining plankton from the sea. In the Chesapeake, researchers found that the years with the most young menhaden tend to be the years with the richest spring plankton, so an osprey lifting a fish from the Bay to feed its young tells a story that starts with abundant microscopic life. When menhaden numbers dwindle, everything starts to go out of kilter.
[ Something is happening in the underwater world of Irish kelpOpens in new window ]
Chesapeake is a warning. Ireland sits on the edge of the north-east Atlantic and across the ocean scientists have been tracking plankton for six decades, watching their populations thin. This summer, researchers led by the University of Plymouth published a health check of these waters. Their verdict? Plankton are in decline in a rapidly warming sea.
The cause, mainly, is heat. The plant-like plankton need two things: sunlight near the surface, and nutrients from the deep. In winter, the sea mixes the two together to feed the spring bloom. But as the surface warms from climate change, it forms a lighter layer that floats on the colder water beneath and resists mixing, choking off nutrients to the surface where plankton grow.
Plankton is where life in the ocean starts. It feeds species as vast as basking sharks and blue whales; it is the diet of small fish, which feed larger fish, which feed birds like osprey.
In Ireland, the osprey chicks released in 2023 are now old enough to breed if they survived the migration across the Sahara and the seas and found their way back here. The skies over our coasts are beginning to refill with a bird that had gone missing for two centuries. What ospreys ask of us is simple: clean, fish-rich waters. Whether they succeed here will depend on whether the fish do too.
