ML387000151
Spotted/Eastern Towhee (Rufous-sided Towhee) Pipilo maculatus/erythrophthalmus
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A Spotted-Eastern Type Pipilo Towhee, with largely black wings, tail, dorsum, head, throat and upper breast. Black “hood” cleanly demarcated from white lower breast/stomach, contrasting with bright rufous flanks, crissum, etc. Two tertials on each wing are tipped in white. The outer ~4? primaries are completely or mostly white from about halfway down, most of the way to their tips. The Towhee gave two types of calls with about equal frequency: A Spotted-like “mew” and an Eastern-like “che-wink!” The Spotted calls sounded a bit less drawn out and gravelly to my ear than Spotted calls I am used to, but apparently this is consistent with other Spotted Towhee populations. And the difference was rather small (negligible?). I suppose the question here is whether this is a pure Eastern Towhee mimicking a Spotted “mew” call or an Eastern x Spotted hybrid. Traditional theory dictates that oscines genetically inherit their calls, and that their calls are not learned; however, published anecdotes (Cohen 1899) and work done in the last century (Greenlaw et. al 1998) casts doubt on this claim within the Pipilo towhees. Since Greenlaw and colleagues proposed that Pipilo towhee calls may be more complex than standard oscine calls and could be learned, no further work has been done on this topic. Yet, regardless of the aforementioned work, it seems quite possible that Pipilo towhee “che-wink!” and “mew” type calls are more complex than other traditional oscine-type calls, e.g. chips, (Jaramillo, Lehman pers. comm.) and thus this is just an Eastern that has learned the Spotted Towhee “mew” call. It has also been noted that apparently pure Easterns will often call with a Spotted type “mew,” both within the hybrid zone (Easterla, Mutchler pers. comm.) and well outside of the hybrid zone (Wee pers. comm.), although unfortunately this hasn’t been documented, to my knowledge. The single biggest wrench in the system is a single bird that has been observed in Nebraska, born to Eastern and hybrid parents, and that appeared phenotypically pure (Strand pers. comm.), unfortunately not documented. The question is raised: how rare is such a bird? Previous authors have treated phenotypically pure birds within the hybrid zone as genetically pure, as well (Sibley and West 1959, Greenlaw 2020), using such a conclusion as a basis to establish assortative mating as a means of speciation. Even if all phenotypically pure birds within the hybrid zone are hybrids, the chances of a hybrid appearing in California are still lower than a pure individual. Yet in reality, it is probably most likely that such hybrids are significantly rarer, making the chances a pure bird would show up exponentially more likely. If one thing can be concluded, it is that if this bird is rejected on the basis of hybridization, no out of range Spotted or Eastern Towhees should be accepted unless they are actively calling individuals, meaning there should be no accepted Eastern Towhee records in the West. Questions for further consideration include of call dialects within Eastern Towhee: Most Eastern Towhees in New England give “che-wink!” calls consistent with this bird, yet the “che-wink!” calls of Easterns within the hybrid zone are apparently different, at least in summer (Swain pers. comm.). Could this be a means of establishing this bird’s origins lie outside of the hybrid zone? A second question to ponder is at the rate Eastern Towhees will mimic Spotted “mew” calls. Are all Easterns mewing within the hybrid zone and elsewhere “discrete hybrids” as this bird might be? Or do all Easterns possess this capability, as has been suggested in places outside of the hybrid zone, e.g. Minnesota (Wee pers. comm.). An intriguing bird. Personally, I am fine with this as a pure individual.
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