Bird of the Week 4/13 - 4/17

This week’s bird is the: Medium Ground Finch

1. I was recently introduced to the Medium Egret, a mid-sized (surprise!) egret that ranges from India to Indonesia to Japan. I think a lot of bird names are bad, but being called “medium” is just sad… The Little Egret is cute, the Great Egret is great, but the Medium Egret is just…. medium?

2. So I wanted to see how many of the >10,000 birds in the world have the word “medium” in their name. Turns out, it’s just three (phew). Along with the Medium Egret, there is the Medium Tree-Finch and the Medium Ground-Finch, both birds of the Galapagos Islands.

3. The Medium Ground-Finch was made medium famous because of its association with Charles Darwin, who recorded this species and other closely related birds when he visited the Galapagos. Eventually, this group of species became known as “Darwin’s Finches.”

   

4. Darwin’s Finches have a wide range in beak sizes, each of which is adapted to eat food of varying sizes (the small-billed Small Ground-Finch eats smaller seeds, the large-billed Large Ground-Finch eats larger seeds). All come from a common ancestor that reached the Galapagos from the mainland. In case you were wondering, the Medium Tree-Finch, along with the Small and Large Tree-Finches, are also in the Darwin’s Finch group, but mainly eats bugs.

5. In addition to the early impact of Darwin’s Finches on the development of the theory of evolution, recent research demonstrated evidence of evolutionary processes occurring in real time. Climate variability can change the availability of seeds of particular sizes in the Galapagos. When small seeds are abundant, smaller billed Medium Ground-Finches do great and produce a lot of small-billed chicks. Then, when the climate changes and bigger seeds are more abundant, bigger-billed individuals do better! As a result, the average bill size among populations fluctuates each year.

6. BONUS: Research shows that being the having the most medium-sized bill among Medium Ground-Finches is not a great strategy. Instead, the most fit individuals (those that have the most offspring), either have a slightly smaller or larger than average bill.

So to bring this full circle, I like the name medium in this case because it reflects something really interesting about the biology of this bird and it’s close relatives. Medium Egret on the other hand…

Have a great week!