In 1966 ornithologists split the Tropical Kingbird into two species, the Tropical, found in southern Arizona and elsewhere in South America, and the Couch's Kingbird, found in southern Texas south into northern Central America. In the 1980s, because of their ranges, I was able to add Couch's Kingbird to my life list.
Their call reminded me of the "Beer" part of the Olive-sided Flycatcher (see last post). It was good to finally REALLY see a Couch's Kingbird. (We saw many Tropical Kingbirds during our research in Peru and Ecuador.)
The situation is more complicated. In the 1990s, Tropical Kingbirds began breeding in southern Texas. During our March 2012 visit, Erika and I found a Tropical Kingbird near the National Butterfly Center near Mission. The bird clearly had a different call from the Santa Ana birds. Thus I added the Tropical Kingbird to my United States list.Brush (1999) and Stoffer and Chesser (1998). The song links in this post are used with permission from Thayer's Birds of North America DVD Gold Edition V5.5.