A display of murre eggshells from Tatoosh Island. Murres are monogamous, mainly because it takes two full-time parents to rear one chick. Studies of other murre colonies have shown that individuals return to the same locales to greet their mates year after year. In fact, most murres return to the colony of their birth to pair off and begin adult life. Migrating Atlantic eels and Pacific salmon share the same behavior.
Murres show several other forms of predictable behavior.
For one thing, they're highly synchronous. That is, they all do the same things at once. For instance, by mid-May of this year, there were no murres on Tatoosh Island. In fact, I thought fleetingly that they might have given up on this site after last year's particularly bad nesting season. However, a scant two weeks later, the island was full of murre pairs.