White-tailed eagles over the Oslofjord

The white-tailed eagle (havørn, Haliaeetus albicilla) returned to the Oslofjord in 2008 after 126 years of absence — the last confirmed breeding had been at Hankøsundet in Østfold in 1882. The first new nest fledged a single chick on the east cliff of Håøya, in Drøbaksundet. Wingspan reaches 200–240 cm, the fourth-largest eagle species globally. Best viewing is from the outer fjord south of Drøbak.

How big they actually are

Wingspan 200 to 240 centimetres. Body length around 90. Females heavier than males — up to seven kilos. The fourth-largest eagle species on the planet and the largest raptor in northern Europe by a clear margin. When one passes over the boat at altitude, the shadow on the water first makes you think someone’s swinging a door.

Unmistakable from below. Broad, rectangular wings held flat in a slow glide, with fingered feathers at the tips. Short wedge-shaped tail — white in adults, dark and pointed in young birds. Hooked pale-yellow bill the size of a small trowel. A voice like a small dog barking in sequence.

How to tell it from a golden eagle

The golden eagle (kongeørn) turns up inland in Norway but almost never on the coast. Two giveaways: the golden eagle has feathered legs down to the toes, the havørn’s lower legs are bare. And the golden eagle has a long, square tail; the havørn has a short, wedge-shaped one. If you see a huge eagle over open water, it is a havørn. Odds are about a hundred to one.

The common buzzard (musvåk) sometimes gets confused with a distant eagle. Wingspan is the tell: buzzard is about 120 centimetres, the havørn is nearly double that. Seen together in the sky, there is no contest.

Why they almost disappeared

The havørn was hunted nearly to extinction in Europe. It was considered a threat to sheep and lambs and was shot, trapped, and poisoned through the 1800s and early 1900s. In Norway it disappeared from everywhere south of Hordaland. DDT pesticide accumulation through the food chain made it worse in the 1950s and 60s: egg shells thinned, chicks died in the shell.

The turnaround came with 1968 — the year Norway protected the species fully. DDT bans followed through the 1970s. Populations recovered slowly, then quickly. By the 1990s Norway had roughly 1,500 breeding pairs. By 2013 the national estimate was 2,800 to 4,200 pairs. Norway now holds more breeding havørn than any country in Western Europe — over half the continental population. It is one of the great conservation success stories of the century.

What took longer was repopulating the old range in the south. The Oslofjord was the last bit to fill back in. Until 2008.

The Håøya pair

Håøya is a forested island in Drøbaksundet — the narrows where the inner Oslofjord constricts to about 1 km before opening into the outer fjord. It sits directly north of the Oscarsborg fortress. In 2008 a pair of adult havørn began nesting on the east cliff, facing Hurum. The pair raised one chick. It fledged successfully. BirdLife Norge rang the chick and confirmed, from ring data, that at least one of the parents had likely been ringed in northern Norway — birds from the northern stronghold coming south to recolonise.

A year-round no-entry zone was set up around the nest. The pair has bred most years since. Other pairs have followed. There are now confirmed breeding havørn in Ytre Hvaler Nasjonalpark (Akerøya, Vesleøya, Heia, the skerries around Torbjørnskjær), in Færder Nasjonalpark (Bolærne, the Færder archipelago), and periodically in the inner fjord.

Where to see them

Outer fjord gives you much better odds than inner. The hotspots, from the boat:

• Drøbaksundet around Håøya. Year-round. Look up at the east cliffs. A perched eagle on a dead pine against the skyline is a silhouette you’ll recognise.
• Ytre Hvaler Nasjonalpark. The skerries south of Torbjørnskjær, around Søndre Sandøy and Vesleøya. Multiple confirmed pairs.
• Bolærne and Færder NP. Regular sightings year-round; especially over the seabird colonies where the eider flocks concentrate.
• Verdens Ende / Tjøme. Land-based viewing from the outer headlands.

Winter is better than summer. In October through March the resident pairs are joined by immigrants from northern Norway moving south. The leafless forest also means better visibility of perched birds on the crowns. On a clear January day in the outer fjord you can sometimes see three or four in the air at once, circling over an eider flock deciding which one to pick off.

How they hunt

Lazy. They are called Nordens gribb — the Nordic vulture — because they scavenge as much as they hunt. They take fish off the surface, mostly lumpfish and cod. They pick off tired eider and sick seabirds from the flocks. They take carrion from the shore. They do not often chase down healthy prey; their strategy is more about finding opportunities than running them down. They can lift about two and a half kilos in flight. A full-grown eider duck sits comfortably inside that.

A useful trick: watch the eider. When a thousand eider ducks explode off the water all at once in a dense panic takeoff, look up. There is almost always a havørn working the flock somewhere above them.

Breeding seasonality

Pairs bond for life and use the same nest for decades. Nest-building begins late February. Eggs laid mid-March. Incubation about 38 days. Chicks hatch late April, fledge late July into early August. Young birds are dark brown all over and take four to six years to reach full adult plumage, the white tail, the pale yellow bill. You can read a havørn’s age from across the bay if you know what you’re looking for.

The fjord they came back to

There’s something worth sitting with: the fjord the havørn returned to in 2008 is very different from the one they left in 1882. Cleaner water in Drøbaksundet, but an almost-collapsed cod stock. An inner harbour turned from shipping yard into swimming beach. Eider populations that are declining, not thriving, and which form a big part of the havørn diet. The eagle is a good news story layered on top of bad news stories, and it is hunting a food web that is still not recovered.

If you want to see one, go to the outer fjord. If you want to go there in a day, that’s what the full-day cruise reaches — Drøbak, the narrows around Håøya, the outer islands beyond. The captains point out eagles every summer; by late autumn they are the steady feature of the outer fjord’s sky.

For the rest: read the porpoise guide or our seasonal wildlife overview. The eagle is only one of the animals Oslofjord rebuilt itself a seat for.

I saw my first havørn over Håøya in 2018. Now we see them on probably one trip in three. They sit on the dead pines on the southwest side of the island, often the same individual eagle two days in a row.