Last June 15 we held the third annual “Fourth of July” butterfly count at Big Creek. I assisted four butterfly experts around the reserve, nets in hand, from about 9 AM to 5 PM. We counted all the butterflies seen, and identified them to species if possible. One type of butterfly, the Painted Lady, was so abundant that we could not effectively count them all, but nearly all the others seen were counted. Our counters (three from UC Berkeley and one from the Santa Cruz city museum) were so expert that, of 872 butterflies seen only 14 could not be identified. 36 species were seen, including 2 species of swallowtail, the California Orangetip, two sulfurs, a marble, a cabbage white, two hairstreaks, six blues, a copper, the California Sister, the Buckeye, an admiral, the Tortoiseshell, three checkerspots, two crescents, an anglewing, the Painted Lady, two fritillaries, the Monarch, the Ringlet, and five skippers! That’s a lot of species, but only a small fraction (only 5%) of the total diversity of moths and butterflies found on the reserve.Last year, with five counters, we saw roughly the same number and diversity of butterflies, but with seven different species! In general, there seemed to be fewer butterflies than last year, which the counters “made up for” by working harder and covering more miles. Julia Smith, a “birdologist” working at Big Creek, agrees. The Song Sparrows she is studying are laying fewer eggs, later in the season, than in previous years. Since they generally lay eggs in proportion to the amount of food they can gather, she concludes that there is a shortage of insect food this spring (including butterflies). Perhaps the cool weather in April and May is the cause. Insects generally thrive more and develop faster in warmer weather.
We have really “hit” the Milk Thistles hard this year, and relatively few of these spiny weeds can be found on the reserve. Five years ago these plants formed dense thickets on ridge tops and benches. Thanks to the cessation of cattle grazing (which creates bare ground favorable to thistle germination), improved road maintenance techniques, the drought, and the great efforts of our machete-wielding steward Feynner Arias, we still hope to reduce this weed to an “interesting exotic.” (9/9/91)