Thursday, October 3, 2013

Island Scrub-Jay



You all saw this coming. How could I spend a field season on Santa Cruz Island without writing about it's famous scrub-jay? Santa Cruz Island is the only place in the world where this bird exists.


Meet yellow-white-blue. Yellow-white-blue was the jay that spent the most time on the grounds of Christy Ranch (my former residence), and thus the jay we saw the most. Yellow-white-blue is the most approachable jay we had. Here Y-W-Bu just caught a skipper, which you can see disintegrating in the wind.


Genetic work has shown that Island Scrub-Jays have likely been genetically isolated from Western Scrub-Jays for several hundred thousands of years. The northern Channel Islands (San Miguel, Santa Rosa, Santa Cruz, Anacapa) at one point formed a giant land mass, Santa Rosae Island, when sea levels were lower. It is thought that the jays colonized and diverged from Western Scrub-Jay while this super-island was extant. As sea levels rose, the populations on the other islands died out. An Island Scrub-Jay bone discovered on Santa Rosa Island was dated to be around 10,240 years old, and is the sole known piece of evidence of their residence on Santa Rosa Island, which is only 9 miles away from Santa Cruz.


Since Island Jays have been around for so long, this means they were likely affected by the presence of pygmy-mammoths, the only large grazing mammal known to inhabit Santa Cruz. Other extinct inhabitants of the northern Channel Islands include a gannet, a puffin, and a flightless goose!


The massive bill is one of the obvious features that sets Island Scrub-Jays apart from their western counterparts. They are also larger, longer-tailed, a darker shade of blue, and have a harsher call. Island Scrub-Jay has never been recorded on any of the other islands in modern times, and neither has Western Scrub-Jay. Their skeletal structure betrays the fact that these birds are poorly built for long-distance flights.


Here is a recently-fledged bird, one of very few that came from a successful clutch this year (directly/indirectly due to drought?). Younger Island Scrub-Jays may not breed for years, possibly because quality breeding territories are already occupied by older birds.


Island Scrub-Jays can be found wherever there are trees or thick chaparral...pretty much anywhere besides beaches and grasslands. Island Packers run trips to two different landing sites on the island, Scorpion Anchorage and Prisoner's Harbor. While there is a group of jays at the campgrounds at Scorpion, the birds are much, much easier to find at Prisoner's. Serious jay seekers should seek at Prisoner's, without a doubt.


One of the lesser-known field marks of Island Scrub-Jay is a blue vent, which you can see here. I find this field mark to be variable though, some birds appear rather gray down there.

Well that's the quick and dirty breakdown of Island Scrub-Jay. A final note...for reasons I cannot explain, many individual birds out there are named after famous (and not so famous) political figures. So instead of pishing for jays, just scream names of politicians into the brush...you cannot fail.

7 comments:

  1. There's gotta be some sort of politician joke considering our current government shut down in there somewhere, but I just cannot come up with it.

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  2. Really enjoyed this post. Excellent info., I think I would enjoy a class or seminar on the natural history of Santa Cruz Island. Well done!!

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    1. Thanks Spare. A lot of cool history/geology/biology out there.

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  3. Good stuff. But field marks, SS? Wouldn't a top "field mark" for this species be "hey - there's a scrub jay and I'm on Santa Cruz Island!"?

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    1. Looking at field marks is more fun than looking at a range map (well, for some of us). Besides, people should keep an eye out for Western Scrub-Jay out there...that would be a hell of a record. One did make it out to a offshore oil rig out that way a few years ago.

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