Similarities in expression of territorial aggression in breeding pairs of northern cardinals, Cardinalis cardinalis

Avian pairs that defend resources year-round may demonstrate similar territorial behavior. We examined male and female responses of northern cardinal pairs to male simulated territorial intrusions. Pair members demonstrated comparable responses towards a male ‘intruder’, as latency to respond and proximity scores were very similar between pair members in the majority of pairs examined. Similarity in territorial behavior could be important in cardinal pairs for maintaining year-round resources.