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Posts Tagged ‘California Oak Moth’

On Saturday, I co-led the youth bird-a-thon team organized by Point Blue Conservation Science, the Drake’s Beach Sanderlings.  We had a fun and hard day in the field.  Fun because we did manage to see some great birds ending with a total of 145 species.  Hard because the federal government shutdown, that is still in effect in the USA even as I write this, meant that all the national parks were closed.  National parks make up about half of the really good birding sites we usually visit on this bird-a-thon, so we really worked for the 145 total.

While birding, we saw something else that was pretty spectacular.  We got lucky, and happened to be out during a major California Oak Moth (Phryganidia californica) emergence.  It was spectacular!  Thousands of moths fluttering under and around the oaks.  Veritable blizzards of moths scattered across much of eastern Marin County.  At some places, this moth bonanza had attracted birds to the feast.  Yellow-rumped Warblers, in particular, were flocking to the same oak trees to catch and eat the moths.  This was only at some points, however, and it was interesting to note that the peak of the moth emergence was in the afternoon when bird activity was at its lowest.  Coincidence?  I am guessing, no.

California Oak Moths have two generations per year.  The adults are rather plain looking dusky grey or tan with a wingspan of about 3cm.  The adults only live for a short time,and do not eat.  Instead, the males do nothing but find a mate, and the females do nothing but find a mate and lay eggs on the oaks.  The caterpillars are black with a yellow stripe running down the center of the back.  These eat the leaves of several species of oak tree, and can be a significant pest.  In places where the population gets really large, whole oak trees can be defoliated by the caterpillars.  Healthy oaks generally recover, so these moths are not a major threat to the trees, but the effects can still be pretty dramatic.  The pupae are perhaps the most striking in appearance of all the life stages.  They are white, or sometimes yellow, with dramatic and complex patterns of black striping and spotting.  We were fortunate enough to see all three life stages on Saturday!  , and

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