Anyone who has much studied biology in general, birds in particular, or evolution specifically has undoubtedly encountered “Darwin’s Finches” and the remarkable diversity in bill shape that evolved among a species related to tanagers (not true finches) that became geologically isolated on the Galapagos Islands. Darwin visited the islands, which straddle the equator approximately 560 miles west of Ecuador, in 1835. There he collected (his servant shot) an array of birds featuring 18 different bill shapes. The variation correlated with the different foods each type of food the birds had adapted to take advantage of on the islands. As all of the species Darwin identified originated from a single type in genus Geospiza, Darwin’s Galapagos finches have long been held up as an example of how evolution works. It’s a complex process that occurs over time and I don’t want to oversimplify it. However, for the purpose in this article, it is useful to think of 1) an underutilized food source and 2) genetic isolation. The original tanager-like specimens of a single type in genus Geospiza became isolated on the Galapagos islands. Given an absence of competition from other species of birds and an abundance of various foods – insects & invertebrates, berries, seeds of different size -, various forms of the original type of Geospiza evolved different bill shapes and sizes (and even different body types) as they keyed in on a given kind of food.

Somehow, I think, (speculate), vocalizations must have played a key role in the genetic isolation that concurred with the move toward food specialization among these Galapagos finches. Most species of birds have a variety of calls and songs, each of which conveys a specific meaning. Black-capped Chickadees, for example, communicate with at least 15 different sounds (let us think of them as words) differentiating everything from the approach of different kinds of predators (one vocalization for ground predators, another for aerial predators) to vocalizations used during breeding, to identify food sources, and so forth.

Bird vocalizations play an important role in differentiating similar species. For example, although certain thrushes to the untrained eye appear quite similar, their songs are different enough to easily distinguish. Similarly, the Pacific Wren found in west coast states from California to Alaska is nearly identical in appearance to the Winter Wren which is found in the east and midwest. But the songs of the two species are different. Thus, they are genetically isolated from each other as much by their vocalizations as by geography. After all, they have wings. They are thus able to transcend geographical boundaries. Their songs – agreeable to members of their own tribe, a foreign language to others – helps keep the two populations separate.

Apparently a good bit of the above applies to Red Crossbills. I have photographs of Red Crossbills from Montana that show a recognizable difference from the Red Crossbills we encountered at Chignik Lake. The Montana birds have larger bills. What causes the difference? Probably diet. The Montana birds we saw were feeding on the seeds of Ponderosa Pine cones. My guess is that it takes a more substantial bill to get into the harder, tighter pine cones than it takes to pry apart the looser scales of the softer Sitka Spruce cones found at Chignik Lake and other locales in Alaska.

But, again, crossbills have wings. So, no doubt playing an important part in genetic fidelity among different types of crossbills are their various vocalizations. According to Audubon, there are as many as eight different types of Red Crossbills in North America, and these varying types are most reliable distinguished by their different calls. At least eight. I’ve read elsewhere that there are as many as 11 different types. This is relatively recent insight. In T. Gilbert Pearson’s Birds of America (© 1917), the Red Crossbills of North America are called American Crossbills; there is no mention of diversity among what was then a sparsely-studied species.

So, just as ichthyologists have come to understand the significant genetic variation that can exist among a given species of fish – such as Steelhead or Coho Salmon – as each kind of Steelhead or Coho has adapted to thrive in a given river system – ornithologists are coming to understand that there can be a great deal of intra-species variation among birds as each type within the species has evolved features allowing it to thrive in a specific habitat.

To me, the take-away lesson here is that we should not merely be focusing on the preservation of life forms on the species level, but that instead we should be dedicated to the preservation of each unique biome and ecosystem.