You probably have birded very lengthy, you’re in all probability conscious that members of intently associated fowl species, when their ranges overlap, generally love one another very a lot, and have infants. Some even do that so usually that pictures of their hybrids can be included in fowl guidebooks. When this occurs significantly usually, such hybridization processes may end up in fully new species.
Right here in central Mexico, we now have one such case that’s so notable that it has been the topic of a great deal of scientific research. One current article, “Hybrid zone or hybrid lineage”, refers back to the concern in its subtitle as “Sibley’s traditional species conundrum in hybrid Pipilo towhees”. The conundrum in query is the affirmation by the ornithologist Charles G. Sibley, approach again in 1950, that every one Noticed Towhees in western central Mexico are the product of a hybridization gradient between the southwestern Collared Towhee, Pipilo ocai, and the japanese Mexican race of the true Noticed Towhee, Pipilo maculatus. (Again then, Sibley used the identify “Purple-eyed Towhee” for what we name Noticed Towhees immediately.)
I’ve, sadly, not but seen a Collared Towhee, regardless that they supposedly happen in my neck of the woods. Luckily, I’ve nice birder associates; these improbable photographs are by Alberto Lobato and René Valdez. Notice the white throat patch above a black collar, the orange mohawk crown, the olive again, and the one barely dusky flanks.
In distinction, the traditional Noticed Towhee of the western U.S. and japanese Mexico has an all-black head, a black again with shiny white spots, and orange flanks. This picture is mine, from the central Californian coast.
Our native variant of the Noticed Towhee, at present known as the (Olive-backed) Noticed Towhee, seems totally different than each. However upon learning the above photographs of Collared Towhees, I can see that Sibley could properly have been proper. Our birds have the black head and reddish flanks of the traditional Noticed Towhee, and the spotless olive again of the Collared Towhee. So are they a subspecies, or a hybrid intergrade?
To make issues much more sophisticated, our presumably hybrid Olive-backed Noticed Towhees can hybridize even additional with the Collared Towhee. Till not too long ago, I had solely seen a couple of examples of this. All had been distinguished by the refined variations of a extra greenish again of the pinnacle, barely lighter flanks, and a touch of the Collared Towhee’s reddish crown.
The explanation I’m writing about this topic now, is that simply this week I lastly noticed my private holy grail of hybrid towhees. The lighting didn’t enable me to see the colour of this fowl’s crown. And it by no means did give us the full-frontal view that may have been so useful. However my few photographs left little question; this fowl had a black colour, a white throat patch, and only a trace of a white line above the eyes. This was a transparent hybrid Pipilo maculatus x ocai. In truth, if Sibley’s concept from way back is appropriate, this fowl might properly be known as a hybrid hybrid.
I ought to in all probability add a private confession on the finish of this publish. Twice, in 2019 and 2022, I complained on this web site about having to make use of the identify Noticed Towhee for our regionally spotless birds. I’ve even begged, with no scientific foundation, for a taxonomic break up, in the event that they wouldn’t change that identify. I’ve accused bird-namers of being biased to their United States expertise of birds. (Admittedly, that’s nonetheless true for the Summer time Tanager, which we solely see right here within the winter.) However my analysis for this publish has proven me that this downside could also be way more sophisticated. In truth, when you transfer east from Morelia in the direction of lands occupied by conventional Noticed Towhees in japanese Mexico, you’ll apparently discover Olive-backed Noticed Towhees similar to mine… however with gentle spots on their wings, rising ever clearer as you progress in the direction of the rising solar.
I humble myself earlier than the complexities of the pure world.
Autor Paul Lewis
