Notes on Western Meadowlark Migration

My mom recently asked me about the migratory habits of the Western Meadowlark (Sturnella neglecta).  I gave her what I knew off the top of my head, but realized that I did not know all that much detail on the subject, and so I went reading.  What surprised me most in what I found was just how little there was to find.  For being such a common species, there is a great deal that has not been recorded about their migratory biology.  For example, even the sizes of the flocks that Western Meadowlarks migrate in are not well documented.  This is a common situation for short and medium distance migrants, as much more focus has been on the study of long distance migrants.

Here is some of what is known.  After the breeding season, small loose flocks start to assemble.  This is usually in September and October depending on location.  These flocks can overwinter if conditions are mild, or they may migrate together if conditions are harsh.  In the northern and central portions of their range, Western Meadowlarks are diurnal migrants, and they can travel as far south as central Mexico.  While this can include individuals moving a distance of up to 1000 km (as indicated by a small number of band recoveries), most Western Meadowlarks seem to follow a pattern where the whole population moves a bit south as a loose unit, so the northern most breeding population will remain the northern most non-breeding population.  Birds that breed at higher elevations tend to be altitudinal migrants moving downslope during winter.  During migration and the non-breeding season, they generally seek out suitable habitat in sheltered valleys during periods of harsh weather.  Western Meadowlarks are actually non-migratory in much of the southern portions of their geographic range, a belt that stretches from Kansas to California.  Even less in known about the spring migration of this species, but migrants generally return to breeding grounds in March and April.

So, keep your eyes out for Western Meadowlark flocks.  You never know what you may learn!

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Oak Moth Emergence

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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