A Tale of Two Rainbows

By Bruce G. Marcot, Ecology Picture of the Week:

I took both of these photos of wild birds in Queensland, Australia.  On the left is rainbow lorikeet race moluccanus from Granite Gorge.  On the right is rainbow lorikeet race septentrionalis (or perhaps a cross of moluccanus and septentrionalis) a bit further north and inland, from Atherton. 

Can these two birds really be the same species?  This is a tale of intraspecific (within-species) variation.

Notice the striking difference in coloration.  

The bird on the left has an orange-red chest extending to the upper belly, streaked with yellow.  It also has a lime-green neck although the bird books show this to be yellow or orange ... but the somewhat similar-appearing red-collared lorikeet has recently been split out as a separate species (Trichoglossus rubritorquis).  
But the bird on the right has a bright yellow chest with no orange or red, and the back of the head is bright yellow with a lime-green neck.  This seems to be a variant of race septentrionalis, or intermediate between two of the races, or perhaps even intermediate between the yellow-chested form of the red-collared lorikeet and race moluccanus of the rainbow lorikeet.  

Confused?  The conclusion here is that some species seem to be highly variable among races, or perhaps even within races, and perhaps even form closely-allied superspecies complexes that hybridize.  

Where is all this variation going, and why did it develop in the first place?  Does it have any geographic-specific utility?  And how could the races and species differentiate and separate out when they overlap so broadly in their distributions?  

This is the stuff of ecological research!  
   

  --Bruce G. Marcot

Image and text © Bruce G. Marcot, Ph.D. Research Wildlife Ecologist,
who produces the Ecology Picture of the Week website.