Date: 3/28/24 9:58 am From: Carol Thompson <cthompson871...> Subject: Re: Merlin and chickadee identification
This has been very informative. Thanks for the observations and background info from everyone.
Carol Thompson
Foristell, MO
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From: Missouri Wild Bird Forum <MOBIRDS-L...> on behalf of Shelby Palmer <spalmer1998...>
Sent: Wednesday, March 27, 2024 2:34 PM
To: <MOBIRDS-L...> <MOBIRDS-L...>
Subject: Re: Merlin and chickadee identification
The question of the hybrid zone width across its length is tricky because of the lack of genetic work anywhere besides west-central MO and east PA. As Jay said, 15-20 km is the estimate made by Mark Robbins and colleagues' work (and supported by my data) in west-central MO. To my knowledge, no genetic work has been published to inform us as to whether that estimate can be extrapolated to east MO. It would be cool to expand genetic sampling efforts eastward to help us zero in on where the hybrid zone is relative to the Missouri River (and to make birders' lives easier).
As far as the chickadee ID issue goes, I mostly jumped in here to support Edge's original statement with recent empirical data. Chickadees most definitely learn their songs from nearby neighbors, which—combined with the genetic hybridization—makes identification to species in and near the zone basically a shot in the dark. Well outside of the zone, I do believe species identifications should stay true to the range maps, even though Merlin may sometimes say otherwise.
Shelby Palmer
PhD Student
Dept. of Biology
University of Florida
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From: Missouri Wild Bird Forum <MOBIRDS-L...> on behalf of Jay McEntee <jaymcentee...>
Sent: Wednesday, March 27, 2024 1:52 PM
To: <MOBIRDS-L...> <MOBIRDS-L...>
Subject: Re: Merlin and chickadee identification
Details on the paper I mentioned:
Alexander, A., M. B. Robbins, J. Holmes, R. G. Moyle, and A. T. Peterson (2022). Limited movement of an avian hybrid zone in relation to regional variation in magnitude of climate change. Molecular Ecology 31:6634–6648.
Studies of natural hybrid zones can provide documentation of range shifts in response to climate change and identify loci important to reproductive isolation. Using a temporal (36–38 years) comparison of the black-capped (Poecile atricapillus) and Carolina (P. carolinensis) chickadee hybrid zone, we investigated movement of the western portion of the zone (western Missouri) and assessed whether loci and pathways underpinning reproductive isolation were similar to those in the eastern portion of the hybrid zone. Using 92 birds sampled along the hybrid zone transect in 2016 and 68 birds sampled between 1978 and 1980, we generated 11,669 SNPs via ddRADseq. These SNPs were used to assess movement of the hybrid zone through time and to evaluate variation in introgression among loci. We demonstrate that the interface has moved ~5 km to the northwest over the last 36–38 years, that is, at only one-fifth the rate at which the eastern portion (e.g., Pennsylvania, Ohio) of the hybrid zone has moved. Temperature trends over the last 38 years reveal that eastern areas have warmed 50% more than western areas in terms of annual mean temperature, possibly providing an explanation for the slower movement of the hybrid zone in Missouri. Our results suggest hybrid zone movement in broadly distributed species, such as chickadees, will vary between areas in response to local differences in the impacts of climate change.
On Wed, Mar 27, 2024 at 12:48 PM Jay McEntee <jaymcentee...><mailto:<jaymcentee...>> wrote:
The best evidence on the current position of the hybrid zone in western MO, and on its movement over time, is in a paper which I'm attempting to attach here (but suspect won't make it through to the listserv). To my knowledge, central and eastern Missouri continue to be more of a mystery as there has been little genetic data collected.
The hybrid zone is indeed narrow where it's been measured (depending on how you calculate it, <20 km in western MO), but its position is varying over time, and 'species-typical' songs might make it further into the range of the other species than genes do, as mentioned. I think that's part of Shelby's suggested caution about ID (human and Merlin) in the vicinity of the zone. Even if you're not technically in the hybrid zone, you might hear a single song and conclude you've heard a Black-capped when you've heard a Carolina Chickadee that's incorporated Black-capped song into its repertoire. So the confusion generated by contact between the two species has a greater width than the hybrid zone itself.
While the hybrid zone is narrow, many of the birds within hybrid zone populations are hybrids, in that they have mixed genetic ancestry (including not just F1s but later-generation hybrids and/or backcrossed individuals).
The hybrid zone is fairly narrow. I saw a study done at Hawk Mountain years ago, which found that the fledging success of mixed pairs was about 10% of that of homogeneous ones. This suggests that the actual number of hybrids may be small. Only DNA testing would show for sure. Bird songs are at least partially learned, so birds growing up in a mixed population might well sing intermediate songs. Also, since birds of the two species are presumably competitive it would make sense that they would react to each other’s songs. Species are in the end artificial human constructions. In nature, there are only breeding populations. I believe that it is easy to over think these issues. If the birds do not always care, why should we.
David Becher
Saint Louis
From: Missouri Wild Bird Forum <MOBIRDS-L...><mailto:<MOBIRDS-L...>> On Behalf Of sgg.bluesfan
Sent: Wednesday, March 27, 2024 11:39 AM
To: <MOBIRDS-L...><mailto:<MOBIRDS-L...> Subject: Re: Merlin and chickadee identification
Well,
If there is a consensus that at least all mid Missouri Chickadees should be changed in Ebird, please post out here and it will reach other birders.
Before Metlin I had based on my own ear considered my yard in Jefferson City Carolinas, but if it takes DNA to confirm I will be glad to change my lists.
I always found it interesting that Merlin did say mine were Carolinas but less than 30 miles north Eagle Bluffs were Black Capped.
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I'm glad to see this conversation happening, as I've also noticed quite a few chickadee observations (of both species) that are pretty well out of range on the MO eBird rare bird alert emails. I did my master's thesis at MSU on the relationship between song and genetic ancestry in Black-capped/Carolina chickadees and did all my field work in the hybrid zone in Henry County, MO (Sparrowfoot Park and Clinton) in 2021-2023. Can confirm (with the genetic data to back it up) that neither song nor morphological characteristics are good indicators of whether a chickadee is Black-capped, Carolina, or of mixed ancestry. In Sparrowfoot Park, most chickadees were 'bilingual' (would switch back and forth between species-typical BCCH and species-typical CACH song) and many also sang intermediate song variants; when the genetic work was completed, Sparrowfoot turned out to be mostly a combination of pure Carolina chickadees (which all, at some point, sang textbook BCCH song) and hybrids. Another location in Clinton had chickadees that sang almost exclusively BCCH-typical song, but had a range of genetic backgrounds from pure BCCH to majority-CACH individuals. Additionally, from a preliminary scan of the morphological data, the differences in body measurements that could be attributed to species was far less than could be attributed to sex (with males across genetic backgrounds larger and heavier than females).
All this to say, I'm of the belief that geography is a far better predictor of chickadee species than Merlin's sound-based ID, and even than the eye/ear of a trained birder. In addition to having been a MO birder for ~15 years, I have held pure BCCH and pure CACH in my hand within the span of a few days, purposefully looking for the established field marks, and am absolutely not convinced that I could tell them apart through binoculars in the field. And if you're in (or think you're near) the hybrid zone, all bets are off and in my opinion all chickadees sighted should be listed as Black-capped/Carolina chickadee.
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