Tuesday, February 20, 2007

15 New North American Bird Species?

A recent article discussed how genetic tests have revealed up to 15 possible "splits" in birds in Canada and the US. These birds include Northern Fulmar, Solitary Sandpiper, Western Screech Owl, Warbling Vireo, Mexican Jay, Western Scrub-Jay, Common Raven, Mountain Chickadee, Bushtit, Winter Wren, Marsh Wren, Bewick's Wren, Hermit Thrush, Curve Billed Thrasher and Eastern Meadowlark. The study stated that DNA diverged by at least 2.5% in different populations of these species, therefore indicating a species separation. Alternatively, they also mention that some species that are currently viewed as separate species are not as genetically divergent: "The Snow Goose and Ross's Goose, for instance, shared 99.8 percent of DNA and the black-billed magpie and the yellow-billed magpie 99.6 percent. Gulls such as the Glaucous and Iceland Gulls were 99.8 percent the same."

So what does this mean to us as birders? The article doesn't state what the AOU's views are on this or what will be done with the data from the study. Listers are probably ecstatic at the idea of getting some "easy ticks" on their lists if some of these species are split. My hope is that these genetic splits are across some type of definitive geographic boundary or that there are field marks that will make these populations easy to distinguish. I'm always open to an ID challenge, but I fear that our field guides will fill with lots of lookalike species that cross boundaries and make identification frustrating or impossible in the field. From a new birder's perspective, these ID challenges can be very overwhelming. On the flip side, I'm intrigued by these discoveries and anxious to see how this plays out. Your thoughts?

7 comments:

Jeffrey said...

So glad you had a good time in CR. I love it there. Also, have you been to see the Smith's Longspur at Jones's Beach? In your area...

To the question at hand: There is really no formula that can be employed as yet to determine species relatedness. Is it 99.9%? 99.5%? It is more complicated than simple percentages could determine. It probably varies by species and the genes (or non-genes) involved. Since the late 1990s the trend has been to "pro-actively" split species that genetics have shown to be reproductively isolated, sometimes whether or not "speciation" has occurred, since that is nebulously defined. This has not been consistant for all birds, however. Birders are eager for a split between Greater and the putative "Carribean" Flamingo, and Green-winged vs Common (Eurasian)Teal (both already accepted by European Ornithologists, but curiously not by the AOU). On the other hand, the possibility of a split in the Red Crossbill complex gives listers fits, since it would be nigh-impossible to determine species to all potential 9 species. Most would have to go unidentified. Tropical birders have also described vocalizations in the Amazon that differ between currently recognized species. One prominent birder estimates that the real number of birds on the planet is closer to 50,000 than the almost 10,000 currently accepted. It boggles the mind for those of us who have puzzled over brief glimpses of simalarly plumaged tropical birds that plumage might not be enough...This is a proven fact for the sub-oscine passerines (i.e. look-alike flycathers like tropical and couch's kingbird, where vocalization is everything). If this is the same for all birds, or if other traits like molt timing (see painted bunting sub-species)need to be considered, than it is way, way more complicated than what we've become used to. Sorry for the long response...It's something I've been thinking a lot about lately!

Patrick Belardo said...

Jeffrey, Unfortunately I haven't had time to look for the Longspur. I don't think it's still being seen. If it's around this weekend, I'll head over there.

Thanks for the great insights. The whole concept of species is confusing to me (and it seems it is to a lot of people). I always thought that speciation involved the ability to breed and produce viable offspring. If a Common Raven lives in the Grand Canyon and has a 10% difference in genetics to a Common Raven living in NJ, then it seems that these scientists are encouraging the ornithological world to consider these separate species since they are geographically isolated and don't breed with each other. But, if I took one of the NJ Ravens and drove it to the Grand Canyon, would it breed with the Grand Canyon ravens and produce viable offspring? If so, then is it really a separate species?

dguzman said...

I'm interested to see what happens with the hermit thrush; will both species' vocalizations be the same spectacular songs? Or will that be the way to tell them apart, kind of like the eastern and western meadowlark? I'm just a beginner, and I've still to ID a hermit thrush, but it's on my "nemesis birds" list!

Jochen said...

This is something that has been discussed very often and in very much detail in Europe especially regarding the large Gulls there. I read a few great publications at home, written for birders and therefore more easy to understand, but didn't bring them with me for my one-year stay in the US, so I cannot really comment in a competent way.
If several species are examined and shown to differ only very, very slightly in their genes, it is always my feeling that we cannot say much more about their specific status than that they are very closely related to each other. After all, even the most slight mutation or genetic difference that is barely detectable might be enough - through affecting reproductive behaviour - to cause a reproductive isolation, hence producing two separate species that just won't mix anymore and will probably be very different-looking in a couple of 100,000 years.
So in this respect I would say genetics are pretty much useless. Who'd doubt that California Gulls and Ring-billed Gulls are clearly separate species just because they share almost all of their genes?

The GREAT aspect about genetics however is that it may indicate where birders weren't looking closely enough at birds. The fact that there is a significant difference genetically between the two "sub"-species of Solitary Sandpiper doesn't mean we have to doubt genetics or any species concept. No, it means we simply have to doubt that we know the species well enough. Obviously the different Solitaries can easily tell the difference and that's what matters because they don't recognize each other as a potential reproductive mate. If WE humans see any differences between them or not doesn't matter. It only means we have to look more closely and I am sure we'll then soon find field marks that will allow us to separate them just like they can tell each other apart.
Or the Ravens. To us they sure look all the same but if you were one of these Eastern ravens and were confronted with a bird from the West, you'd probably feel like a human looking at a chimp.

About the species concept: yes, a species is basically a community of individuals that share a common gene pool, meaning they can mate and reproduce fertile offspring.

But of course it is not that simple. There are cases e.g. where two forms can mate and produce fertile offspring, but this hybrid offspring isn't quite as "fertile" as pure birds, meaning they have on average smaller clutch sizes. This might already be enough to isolate the main populations completely as you only have a stable area of hybridisation in a zone of range overlap but no influx of these "strange" genes / hybrids beyond that.
Or in another scenario, the offspring of such mixed pairs might include infertile males but fertile female birds. Here, too there's no possibility for a free and complete gene flow and we have a justification to call them separate species, even though there'll always be a few hybrid birds we struggle to identify (or would mistakenly call proof of a clinal variation).

Gosh, this has been a long comment. Hope it wasn't too boring and helped in any way.
Cheers and good birding, there's quite a few things to go and find out now to improve our understanding of bird distribution and identification. Who's going to be the first in the East to clearly identify a Western Solitary Sandpiper? Are they vagrants or regularly occuring etc.?
Great new questions everyone should be eager to answer! And spring miration is on its way...

Patrick Belardo said...

Jochen,

Thanks for the great comment. It was very enlightening. There's so much still for me to learn.

I'm going to do some personal research on those Solitaries so I can be the first!

Jochen said...

Well, I suppose you're challenging me: I had planned to be the first!

The race is on then
;))

Gyorgy Szimuly (SzimiStyle) said...

Interesting note. I am always checking the list updates and many times surprised that one species is lumped with another while obviously different looking and geographically separatable subspecies are belonging to the same genus.

BTW, the article link doesn't work.
Cheers: Szimi