Questions raised by the consumption of cane sugar by a Black-throated Blue Warbler (Setophaga caerulescens)

I address questions raised by an observation of a Black-throated Blue Warbler (Setophaga caerulescens) eating unrefined granulated cane sugar in Kingston, Jamaica. Sugar consumption implies the presence of taste receptors sensitive to sucrose and digestive sucrase activity sufficient to assimilate highly concentrated sucrose solutions. The ability to efficiently digest disaccharides, such as sucrose, and more complex oligosaccharides has permitted wood warblers and other nine-primaried oscines to exploit nectars of hummingbird-pollinated flowers and homopteran honeydew that may not be easily digested by avian clades such as thrushes and mimids that appear to lack digestive sucrases. In a broader context, clade-specific differences in digestive physiology may result in resource use patterns in birds that mimic the outcome of interspecific competition.