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Recognize this bird? Thinking of yesterday’s post? Well, think again. This is an entirely different species. Yesterday’s post contained a Downy Woodpecker, but this here is a Hairy Woodpecker. So, what are the differences?
These birds do look incredibly alike, I’ll admit it. These most noticeable differences are size (hard to tell from two separate photos, but the Hairy is slightly larger) and bill length, with the Hairy having a longer bill. The differences are more than skin deep though. To be designated as a separate species, genetic evidence is key. These genes often determine breeding compatibility, and so looking at mating is a good way to measure those genetic differences. This has lead to the widespread use of the Biological Species concept, which argues that if two critters can’t mate and create offspring that can survive and go on to make more babies then they are two different species. The most well known example of this concept in action is the mule, a cross between a horse and a donkey. The cross makes offspring that can survive, but mules are infertile, and can’t reproduce, thus the horse and the donkey are two different species. Hybrids have been found between Hairy and Downy Woodpeckers, but they are thought to be unsterile. Other genetic evidence has also placed them surprisingly far apart given their many similarities. Their similarities likely are an example of convergent evolution, where two species acquire many of the same adaptations not from their common ancestor, but from a shared way of life, which pushes them to evolve beneficial characters to that niche. Nature has a funny way of creating a design that works and echoing across the many forms of life we have on our planet. at Summerside, Prince Edward Island