Cryptic Species in the Avian World

Nature Talk
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Last month, Cornell released a statement on how citizen science (like eBird and iNaturalist) has aided in the finding of cryptic species through audio recordings. This article showed up on my social media feed at the most appropriate time, just after I thought about this same subject while birding.

The following two images shows a Mountain (oriantha) White-crowned Sparrow I photographed and recorded in Oregon. They are also considered the Rocky Mountain subspecies as they breed throughout this range. Normally, identifiers will look for the large, pink bill and dark lore but look at the spectrogram closely. You can listen to the recording here.

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Now we have the Gambel’s White-crowned Sparrow. These birds are significantly more common in Oregon despite being the migrant subspecies. They are typically identified by their orange bills and pale loral region, comparative to the Mountain WCSP. The photo was taken a couple years ago but the recording was taken today. Note the distinct differences. Recording here.

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To further install the cryptic species idea, this is how I got the above recording of the Gambel’s. I could hear them from quite a ways but I was not close enough for a decent recording. But as I got closer to their brambles, they stopped singing, dive into the thickets and continuously do their tisp calls. So I pulled up the Audubon app on my phone and those who have it can pull it up too but if you don’t, here’s the website link. I played “Song #1”… nothing. I played “Song #2” and almost immediately, twenty sparrows popped out of the brush and one after another they were singing. “Song #3” and “Song #4” produced the same results as the first song, absolute silence. I played song two again and the sparrows came out again in full force, providing me with excellent audio.

Directly after this experience, it got me wondering about cryptic species. Why did the Gambel’s White-crowned only respond to one song and only one song? They acted like the other songs were of a foreign language. Is it because they are actually a cryptic species and will stay in their respective flocks, like crossbills and grosbeaks? Thoughts and other possible North American cryptic species?

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Not endemic to North America, but I seem to remember reading European and North American Herring gulls will not respond to the call of each other.

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Also don’t know about USA examples, but island Chaffinches have totally different calls too and are not recognised by mainland birds.

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If I heard someone speaking Bakongo, I would certainly have nothing to contribute to the conversation. But that doesn’t mean that a Congolese person and I are different cryptic species. I don’t see why an avian species cannot have different languages in different regions just as the human species does.

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I believe it depends on perspective and intelligence. The Red Crossbill is very likely a cryptic species because they feed on specific pine cones, their ecological differs but most important of all, their flight calls are different. Crossbills seem to only associate themselves with another of their type and when you combine the other features I mentioned, they start creating reproductive barriers. This is all associated with call.

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Songs are just a clue that two populations may be different species. The birds are then further studied before a conclusion can be made.

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