Iceland was first settled by Norwegian Vikings in about the year 870, 870.

Besides livestock like cows, horses, and sheep, these people brought with them some domesticated

cats. Cats were popular in Scandinavia for their effectiveness at keeping rodent populations

in check on farms. Before Viking ships landed on

its shores, Iceland's only native land-dwelling mammal was the Arctic fox. So humans, farm animals,

and cats were all alien invaders on that isolated island in the North Atlantic.

Fast forward about 1,100 years and you find me, looking at a black and white house cat in Iceland's biggest city and capital, Reykjavik.

I was there leading a birding slash nature tour not that long ago.

My group and I were doing some light bird watching

in a large downtown park, enjoying waterfowl in the ponds and songbirds flitting around in the trees.

One pond has a tiny man-made island in the middle. The island was landscaped specifically to serve

as nesting habitat for Arctic turns.

In summer, it teems with dozens of turn chicks and their devoted parents.

The Arctic Turn, Sterna Paradisia, is a graceful white bird in the family Laridie, which includes

turns and gulls. It has a black cap and a

sharply pointed bill the color of blood. Every year, these birds make a round-trip migration to the

waters around Antarctica and back to the far north. That's about 25,000 miles or 40,000 kilometers every year. So there I was in Reykjavik,

with my group, looking at the turns, when a cat caught my eye. It wasn't on the little island,

thankfully, but on the grassy shore of the pond. The cat was jumping in the air acrobatically, swatting at Arctic turns.

Several turns were swooping back and forth just out of reach over the cat's head.

This is what they do. These birds aggressively dive-bom any predators near their nests.

And they can't always distinguish well-meaning

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