Fidelity to Their Mates and Fighting

Two male peregrines, Pulse and Erie, battle for the Cathedral of Learning site, 18 March 2007. Dorothy waits as Erie kills Pulse.
Two male peregrines, Pulse and Erie (left side of box), battle for the Cathedral of Learning, 18 March 2007. Dorothy watches as Erie kills Pulse.

Question: Do peregrines mate for life?  How do they acquire a new mate?  Do they fight to the death?  Will the male defend his mate against female challengers?

Answer: Peregrine falcons are serially monogamous, though exceptions do occur.  In fact they are more loyal to the nest site than they are to their mates, especially if they’ve successfully raised young there.

Good nest sites are hard to find so each spring peregrines who want to acquire a site, called intruders, test the owners.  Challenges are always female against female, male against male.  Couples do not defend each other against the opposite sex.  It is up to the member of the same sex to chase off or fight the intruder.

Intruders are usually chased away but if the challenger engages the resident the two will lock talons and fight in beak-to-beak combat.  The loser often dies.

The winner gets the territory, the nest site, and the remaining peregrine as a mate.  The new couple immediately courts and becomes a pair. Peregrines don’t grieve.

It is truly survival of the fittest.  For real life examples of this see:

(photo of two male peregrines fighting at the nest at the University of Pittsburgh, 18 March 2007.  Falconcam by The Western Pennsylvania Conservancy)