Incipient Speciation of the Island Scrub-Jay
A picture of the acorn eating island scrub-jay.
A picture of the pine nut eating island scrub-jay.
I found an interesting article about the divergence of beak characteristics in the island scrub-jay found on Santa Cruz island. Katie Langin earned her Ph.D. studying the island scrub-jay and found that there were two types of populations of scrub-jay based on their beaks. One group has long, shallow beaks that allow them to remove food from pine cones while the other group has shorter, stouter beaks that are good at hammering open acorns. The first group lives mostly in the pine forests on the island and the second group lives in the neighboring oak forests. There is no physical barrier which separates the two groups but they tend to breed with the birds found in the area they live in so birds with long, shallow beaks will tend to mate with other birds that have long, shallow beaks, etc. The evolution of the island scrub-jay has been going on for a million years on Santa Cruz island. There are less than 3,000 scrub-jays that live on Santa Cruz island which doesn’t seem like a large population to me. It is impressive how these birds can evolve such distinct subgroups while confined to an island.
Katie Langin “Evolution Works in Fast, Localized, Mysterious Ways” WildThings Slate’s Animal Blog, Feb. 6 2015.