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I was surprised to read nothing about the timing of the songs when the birds are separated by distance. The ABCD duet would become A—BC—D (where the dashes represent the time delay due to distance) to the male and AB—CD to the female. The duet could be a distance-measurement tool for pairs wanting to keep track of how far apart they are.

Joe Heagney
Arlington, Wash.

When I read this article, the behavior of my pet yellow-naped Amazon, Wellington, suddenly became less surprising. He often likes to whistle the four phrases of “How Much Is that Doggie in the Window?” However, sometimes he indicates, by pausing after phrase A, that he wants me to whistle phrase B. He then whistles phrase C and pauses for me to whistle phrase D. Other times, if I whistle phrases A and C, he whistles phrases B and D.

Andrea Borr
La Jolla, Calif.

In the wild, yellow-naped Amazon parrots perform duets in which a male and a female take turns calling, says Timothy Wright of New Mexico State University in Las Cruces. —S. Milius