A comparison of neighbour–stranger discrimination in eastern and western meadowlarks

Eastern meadowlarks, which have large song repertoires, showed weaker neighbour–stranger (N–S) discrimination than western meadowlarks with smaller repertoires. Discrimination in western meadowlarks was similar to that reported for other species with repertoires of comparable size. Repertoires may interfere with mechanisms responsible for N–S discrimination, resulting in more strife between neighbors than in species with single songs. This may be a trade-off for benefits of repertoires or may be adaptive where neighbors threaten one another. Significant differences in response to N and S songs all occurred between the first two presentations in N–S–N (rather than S–N–S) sequences. Carry-over of the response to the S song may result from poor discrimination or from intolerance toward the N song, once the subject locates it inside his territory.