Hi Ontbirders, I suspect some of you will be interested in this. The story is a bit complicated but I will do my best to distill the essence of it here. If you want more details, please don't hesitate to email me privately.
You may remember from my last message of January 20th that Scott Kelso and I sequenced a mitochondrial gene (mtDNA) called COI and found that the Pakenham bird contained the mtDNA of a Baltimore Oriole. This told us nothing about the bird's direct parents but proved that somewhere in the female line there had been a Baltimore Oriole. So it is a hybrid, but to which degree we could say no more. Nuclear DNA is needed to identify the parents. But there are two issues here. 1. Nuclear DNA is typically much harder to obtain than mtDNA (fewer copies exist in the cells). We have found that sequencing nuclear genes from bird faeces is difficult to impossible as very few cells are in the droppings and there are also inhibitors that make it tough to sequence. We can sequence mtDNA from bird droppings, but even that can be tricky. 2. It turns out that Baltimore and Bullock's Orioles have almost identical nuclear DNA. The typical situation in close relatives is that the nuclear DNA is still somewhat divergent but the mtDNA is often identical (for example, Cinnamon and Blue-winged Teal cannot be told apart by mtDNA but differ in their nuclear DNA). It is very unusual that this is reversed in the 2 oriole species. In fact, it turns out that the resurrection of the two species from Northern Oriole was done largely because the mtDNA and morphology are almost always congruent. i.e. if it looks like a Bullock's, it has the mtDNA of a Bullock's and if it looks like a Baltimore it has the mtDNA of a Baltimore. This is only messed up within the hybrid zone (which is very narrow - only 160km across in Kansas for example). Based on the current taxonomic paradigm, this means that carrying the mtDNA of a Baltimore Oriole was highly suggestive that the Pakenham bird was a Baltimore. Because of its uniformity, we thought at fist that nuclear DNA would not be helpful. However, we finally found a single nuclear marker that had some repeatable pattern at the species level. The gene is called Beta Fibrinogen and there is a rapidly evolving non-coding piece (called an intron) that has 4 base pairs that match the morphological parent (e.g. an 'A' at one position is consistent with Baltimore while a 'G' is consistent for Bullocks). Only 4 base pairs consistently different for all of the nuclear DNA ever sequenced is remarkably little in terms of differentiation! And there are only a few sequences from this gene available in public databases so of course sample error remains a possible issue. The take home message here is that like most of the biological sciences, taxonomy does not always render black and white answers. Interpretation is required and the hypothesis is always open for further testing (in this case, when more sequences of beta fibrinogen are obtained, we may find out that this test we did does not hold up). So what did we find out today when the beta fibrinogen sequence came back? Based on what I state above (with appropriate caveats), both parents of the Pakenham bird were Bullock's Orioles. By applying purely stochastic principles, it is likely that the grandmother or great grandmother was a Baltimore Oriole (somewhere in the lineage there was a Baltimore). So, the bird is a hybrid, but not an F1 hybrid. The OBRC will have to decide what this means, but for me, it certainly means that I would tick this bird off on my list. More interestingly, it means that the Pakenham Oriole was not just a mega vagrant, it was a real needle in the haystack - a bird almost certainly from the narrow hybrid zone that runs south from Alberta and through Kansas. The probability of a hybrid getting here over a pure Baltimore is minute so it makes the find that much more interesting. As a final note, there are methods for determining the actual origin of a bird (by looking at decay of radioactive isotopes in feathers that would have been grown on the breeding grounds). This requires large sample sizes and a concerted effort so it is unlikely to be done for this bird (but it is alive and kicking in the Wild Bird Care centre if someone decides they want to do this). Feather and faecal analysis of vagrant birds is becoming a big deal in western Europe and will be increasingly common here. Each species will bring its own suite of interesting problems and offer a fantastic opportunity for us to learn more about the individual involved as well as about the species. Thanks very much to Ray Holland and Richard Waters for sharing this find with the community and to Bruce di Labio for getting the feather and faecal samples required to do this work to me. Good birding, Jeff -- Jeff Skevington, Research Scientist Canadian National Collection of Insects, Arachnids and Nematodes Agriculture and Agri-Food Canada 960 Carling Avenue, K.W. Neatby Building Ottawa, ON, K1A 0C6, Canada Phone: 613-720-2862 FAX: 613-759-1927 E-mail: jhskeving...@gmail.com _______________________________________________ ONTBIRDS is presented by the Ontario Field Ornithologists - the provincial birding organization. Send bird reports to birdalert@ontbirds.ca For information about ONTBIRDS including how to unsubscribe visit http://www.ofo.ca/site/page/view/information.ontbirdssetup Posting guidelines can be found at http://www.ofo.ca/site/page/view/information.ontbirdsguide
