Is Nutting’s Flycatcher actually two species?

Lauren Harter and I have been very busy with work lately and haven’t had the time to update the blog as much as we like (but we do have some interesting stuff that we will hopefully finish and post soon!). Today however I had a second to spend at the computer and catch up on reading some e-mails and checking various things posted when I came across something interesting on the AOU webpage.

This baby Nutting's Flycatcher 21 Apr 2013 in the BWR NWR, Moh Arizona was born in an area where Ash-throated Flycatchers are common, a good indication that Ash-throated and Nutting's Flycatcher tend not to hybridize. Copyright (c) 2013 David Vander Pluym

This baby Nutting’s Flycatcher 21 Apr 2013 in the BWR NWR, Moh Arizona was hatched in an area where Ash-throated Flycatchers are common, a good indication that Ash-throated and Nutting’s Flycatcher tend not to hybridize. Copyright (c) 2013 David Vander Pluym

Recently the AOU has posted a batch of pending proposals. Among others that caught my eye was a proposal to split Nutting’s Flycatcher into two species. Since Lauren Harter and I discovered the Nutting’s Flycatcher at Mosquito Flats BWR NWR back in Dec 2011 our interest has been piqued by the species and when we have had a chance we have tried to read up as much as possible on the species as well as watching it in the field. Listening to recordings, we had noticed vocal differences between Nutting’s Flycatchers that have been found in the US, those from central and southern Mexico (Myiarchus nuttingi inquietus) and those in southern Mexico to Costa Rica (M. n. flavidior), and we had heard some discussion about the status and the differences between these taxa.  I know nothing about the nominate taxa which occurs in the interior of southern Mexico to Nicaragua, except that the genetics align it with inquietus. Listening to the various calls and songs of each taxa on Xeno-canto and Macaulay Library really gives you an appreciation for just how different they are!  Take this recording from Costa Rica for example: I have heard nothing like it from the Bill Williams birds or any recordings of northern Nutting’s. Compare for yourself with vocalizations of Nutting’s Flycatcher from the Bill Williams River or elsewhere in west Mexico.  I know that I would not be able to identify one of these southern birds as a Nutting’s Flycatcher if I were to hear it out birding!

Given how different the vocalizations are it is not surprising that a recent paper found that the two taxa differ significantly at the genetic level as well. This change in both vocalizations and genetics is apparently very abrupt with birds on the coastal plain of southern Mexico differing from those in the nearby hills. The two taxa are said to be similar in appearance and it will be interesting to sort out field identification. A quick google search of Nutting’s Flycatchers from Costa Rica indicates that identification may not be as difficult as northern Nutting’s vs. Ash-throated, which are very similar despite not being closely related.

Speaking of how similar Nutting’s is to Ash-throated it may surprise some to learn that when Nutting’s Flycatcher was first described it was a controversial species. At first given the similarity of Nutting’s and Ash-throated (especially when you could only work with specimens) as well as variation within the tail pattern of each taxa, that the two were considered one species with widespread intergradation.  It was not until 1961 when a paper published by Wesley E. Layon put this notion to rest. Combining both field work and examining a large number of specimens he was able to show that there was likely little if any hybridization and that plumage and vocalizations conformed to species. I highly recommend this paper as it is still considered to be the best for identification criteria for Nutting’s Flycatcher vs. Ash-throated. As an aside, if there ever was a chance of hybridization between the species it was in the Bill Williams when in March 2012 the Nutting’s was hanging out with an Ash-throated before being driven away by a second Ash-throated. Now instead of hybrids we have a pure pair breeding!

This Nutting's Flycatcher has been observered by many, but perhaps you have also seen "Nutting's" Flycatchers in Costa Rica? If so you may have actually seen a different species. Here 19 Jan 2013 BWR NWR LP Copyright (c) 2013 David Vander Pluym

This “Phillips’s” Flycatcher has been observed by many, but perhaps you have also seen “Nutting’s” Flycatchers in Costa Rica? If so you may have actually seen a different species. Here 19 Jan 2013 BWR NWR LP Copyright (c) 2013 David Vander Pluym

If the split is accepted the issue of naming will come up and if you are interested in that I would strongly suggest reading the proposal as perhaps instead of seeing a Nutting’s Flycatcher you actually saw a Phillips’s Flycatcher or a Ridgway’s Flycatcher.

Though unlike several of the other proposals a split is unlikely to give most birders a new tick, it is still an interesting split and helps to illustrate the importance of vocalizations in species limits. Humans are very visual animals, and because of this we often forget that for other animals this might not be the most important aspect for them in finding a mate.

-DVP

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About David Vander Pluym

Birder biologists currently living and working in the Lower Colorado River Valley. When not out in the field I spend a lot of my time reading and writing about birds. I have always been drawn to areas under birded and species that we know little about.
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