The lumping of the gulls

For any of you who have looked through a flock of gulls and thought it was hopeless to pick out the different species, you are in luck. Scientists have just released their findings in the UK journal Molecular Ecology Notes regarding DNA barcodes for bird species in North America. They found that most of the large, white-headed gulls (California, Herring, Iceland, Lesser Black-backed, Western, Glaucous-winged, and Glaucous Gulls) share 99.8% of their DNA. Although there is no official percentage that endows a bird with its own species name, these gulls show a high percentage of similarity, enough that the researches lumped them all into one group.

This would greatly simplify the issue and birders would only have to worry about separating Herring and Ring-billed Gulls. The idea that they are all the same species is difficult for me and many others to believe. There are problems with the DNA barcode method because it does not look at the whole DNA sequence, but just one particular area. Despite this, it is still an interesting study and helps us feel better for having such problems ID’ing these birds.

I have seen all of these gulls and photographed them as well so I give you 4 to ponder. You tell me if you think this is acceptable variation for one species.

Kumlien's Iceland Gull Lesser Black-backed Gull

Herring Gull Glaucous Gull
clockwise from top right:L. Black-backed Gull, Glaucous Gull, Herring Gull and Iceland Gull.


One Response

  1. Certainly, there are “species” that exhibit tremendous differences in physical appearance. The Island Thrush comes to mind. External appearance alone is not a reliable indication of how birds (or other living things) are connected to each other.

    But as I stated in my own post on this topic, I am not comfortable defining species based on a percentage range. I prefer a more holistic approach, but such an approach is messy, confusing, and necessarily self-contradictory.

    Will genetic data eventually be recognized as sort of a trump card, overruling other kinds information? Well, “species” is a rather arbitrary concept after all, and if we wanted to, we could change the definition of species to mean “populations that show greater than a 2 percent difference in their DNA barcodes.”

    But I for one wouldn’t like it.

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