Thursday, June 24, 2010

Indigo and Lazuli Buntings

Genetic research is revolutionizing our understanding of how birds are related and of what constitutes a species.  The Yellow-shafted and Red-shafted Flickers I recently wrote about are a good example. They look different but they are genetically similar and they interbreed. Therefore they are considered to be the same species, now called the Northern Flicker.

At first glance, Indigo Buntings (the first photo taken in Northfield, Minnesota) and Lazuli Buntings (the second photo taken in Aberdeen, South Dakota) appear to be a similar example.  Although they look quite different, where the eastern Indigo comes in contact with the western Lazuli, these two buntings often hybridize. Thus, Alan Phillips, in his book Birds of Arizona, combined the two into a single species, which he named the Common Bunting.
Studies of certain enzymes suggest that Indigo and Lazuli Buntings are the same species, because the two buntings differ in enzyme frequencies in areas where they do not overlap, but these enzymes are similar where the ranges do overlap.  However, work with mitochondrial DNA suggests that Indigo Buntings' closest relative is the larger bodied and billed Blue Grosbeak (photo below from Fort Pierre, South Dakota). Furthermore,  Lazuli Buntings are relatively distantly related to any of the other North American buntings.  These results would imply that Indigo and Lazuli Buntings are distinct species that occasionally hybridize. Because of these conflicting data, most ornithologists have yet to lump Indigo and Lazuli Buntings into a single species.
Just to confuse matters a bit more, Indigo Buntings are also known to rarely interbreed with Painted Buntings in southeastern North America.  The photo below is a Painted Bunting in Florida.  I do not think anyone, however, suggests that Indigo and Painted buntings are the same species.

What is a "species?"  Most ornithologists adhere to the Biological Species Concept.  A species is a group of individuals that are at least potentially capable of interbreeding.  In other words, a species consists of individuals that share a common gene pool.  Other scientists lobby for the Phylogenetic Species Concept.  Here a species is a group of individuals that share a relatively recent common ancestry.  One result of this second concept is the recognition of many more species than are currently illustrated in our field guides.

My source for much of the genetic information is Payne, Robert B. 2006. Indigo Bunting (Passerina cyanea), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.bnaproxy.birds.cornell.edu/bna/species/004

6 comments:

  1. What a pity it would be to lose descriptive names like indigo and lazuli and end up with "common" as a descriptor for these beautiful birds. We went in search of a lazuli bunting last year, following a rare report near Henderson, but didn't have any luck, so I've never seen one.

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  2. Penelope--Indigo Buntings are fairly common on telephone wires between Northfield and Big Woods State Park.

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  3. Dan - I think I am spotting a female Lazuli Buntings this morning in Farmington (just north of Northfield on HWY 3). Is this possible?

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  4. Actually, I just saw them - they are juvenile Indigo buntings! Their parents are in a nest close by....

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  5. Dan... I am sorry for a thrice post... But now I see a brownish breast on the male... Lazuli!!! And juveniles in tow!

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    1. The two species interbreed where they overlap. A vagrant Lazuli might well breed with an Indigo if no other Lazulis could be found.

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