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Recently, the North American birding community had some exciting news. No, not the appearance of an Ivory Gull or super rare owl in someone’s backyard that then posed for a suite of photos taken by each and every birder that showed up. No, because that sort of thing is typically relegated to the realm of the birding dream. Oddly enough, the news in question doesn’t have anything to do with bird sightings yet it still acts as on of the more important and anticipated pieces of information of the birding year. This coveted publication becomes available to birders on an annual basis, and oh how the serious (aka obsessed) among us look forward to the news. Those of us who keep lists and are extra concerned about bird identification can’t wait to see the publication, the big news of the year, because it tells us whether or not we will be upping the life list with armchair ticks or subtracting from it by ways of the dreaded lump.

The Northern Emerald Toucanet was one of those sweet armchair ticks from a previous supplement.

As any birder in the know must have surmised, I’m talking about the AOU supplement to the checklist for the birds of North America. Although the checklist is already established, thanks to occasional species additions to the list (by way of adventurous or mal-adapted birds that fly in from Asia, Europe, or South America), and studies that assess and elucidate the evolutionary histories of everything from tyrant-flycatchers to foliage-gleaners and Yellow-rumped Warblers, changes to the list are inevitable and happen each and every year.

In Costa Rica, since our local national list almost always tracks changes made to the AOU list, we likewise need to keep up on the proposals for name changes, splits, and lumps that have been accepted. In 2018, thanks to a double lump and one split, many of us are going to be subtracting one bird from our Costa Rica lists. Ouch. This will affect Big Days totals! And lead to revisions of all field guides! But, on the plus side, we have one more species on the list, that of a regional endemic and one that I have been stressing the importance of seeing for some time because I was fairly certain that it was a separate species.

That brand newly recognized bird species is the Chiriqui Foliage-gleaner, the former excertus subspecies of the Buff-throated Foliage-gleaner restricted to humid forest habitats in southern Costa Rica and western Panama. As with many other taxa that turn out to better known as species, this one was recognized as perhaps being one by the people who first described it based on morphological differences. While we can’t see many differences in the field, detailed studies of the bird in the hand is another story and who knows what else the birds perceive? However, we do know that they don’t recognize the songs of Buff-throated Foliage-gleaners on the other side of the mountains and vice versa. That lack of song recognition coupled with large differences in DNA (6%) were enough to convince the checklist board to recognize the split. The next thing that comes to mind is whether or not the new species is threatened. Although it does need humid forests, since it can also occur in second growth and seems to be fairly common from the lowlands to lower middle elevations, the “C. Gleaner” doesn’t seem to be in trouble.

A Chiriqui Foliage-gleaner from Luna Lodge.

Now for those sad, hard knocks results for the lister, the lumps (and as with any lump, they tend to be painful).

After years of wondering which tanager with the red rump was a Passerini’s and which was a Cherrie’s while also wondering why the name just had to be changed from the perfectly descriptive Scarlet-rumped Tanager, lo and behold, these two are back to being the same species! The Scarlet-rumped Tanager is back in business in Costa Rica because of little genetic differences and equal recognition of each other’s songs. Nope, not enough time for enough divergence, no more need for Big Day worries about finding those Cherrie’s Tanagers in Carara.

The good old Scarlet-rumped Tanager.

The second lump concerns a wood-warbler and one that lives in a very limited area. Some years ago, DNA studies revealed the Masked Yellowthroat subspecies around San Vito to actually not be a Masked Yellowthroat after all. But, it stayed that way on the list because of the lack of additional studies to show what it really was. Now, after combining DNA studies and playback experiments, the special yellowthroat with the super small range in southern Costa Rica and adjacent Panama is listed as a subspecies of the Olive-crowned Yellowthroat. Since they sound and look quite similar and have very little genetic differences, even the most reluctant and die-hard of listers would have to admit that the birds are really the same biological species.

There was also one common name change. White-collared Seedeater is no more! Thanks to the elevation of West-Mexican birds to species rank (and with the cool name of Cinnamon-rumped Seedeater), the ones in Costa Rica are now known as Morelet’s Seedeater (Sporophila morelleti). If you have seen this bird north of Oaxaca, at least you can enjoy an armchair tick that sort of equalizes the removal of one of those lumped tanagers.

There were some other changes to scientific names and the splitting of the storm-petrels into two different families but I won’t talk more about that here. For more details, check out a summary of the supplement at the ABA blog, and the proposals for splitting and lumping the birds mentioned above. Now to get to work on updating birding apps for Costa Rica, Panama, and Belize.

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4 Responses to “Changes to the Costa Rica Bird List – Plus One, Minus Two”

  1. I’m not sure that I buy that Chiriqui Yellowthroat and Olive-crowned Yellowthroat look very similar. I’ve never seen a Chiriqui bird without significant gray along the top of the mask, and I’ve never seen an Olive-crowned with any gray at all on top of the mask. It also seems to me that Chiriqui YT is more of a marsh bird, while Olive-crowned is often found in grassy fields and margins. While the songs are extremely similar, I’m not a huge proponent of the new taxonomic position. I do wholeheartedly agree it’s not a Masked YT though!

  2. That’s true, there is that difference, and checking images of the female, she does have more gray on the head than the Caribbean counterpart. I agree, one is more of a marsh bird than the other although Olive-crowned does seem to prefer marshy areas and at least seems to need wet grass. It seems like Gray-crowned might outcompete it in drier, more open situations. Not entirely sure, but that’s my first impression, both respond to each other’s songs.
    Perhaps this is somewhat of a Golden-winged-Blue-winged Warbler taxo. situation (but without the cool hybrids)?
    Yeah, not a Masked for sure!

  3. Late to the game here but yes, they do look different. And if further study suggests that plumage differences are important for reproductive isolation in yellowthroats, then I think there could be a case that Chiriqui and Olive-crowned are different biological species. Given that they live in different places though, the best we can do is guess, and their near-identical songs and genetics (though based on very limited genetic sampling) argue to consider them the same species at present.

  4. @Ben- Thank you for your input Ben!

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