the way it was in suburban habitats
patfoley at csus.edu
Mon Jan 21 17:14:58 EST 2002
Do you have any documentation for your claim that there has been no downward
trend in butterfly numbers in the Bay Area? My experience (undocumented) in
Davis is that Moth numbers are way down over the last twenty years. It is
regrettable that population size estimates have been so spotty.
patfoley at csus.edu
Paul Cherubini wrote:
> Richard Worth wrote:
> > Barb, I know what you are talking about. I grew up in San Jose during the
> > wonder years of the 70's and there were many more butterflies around
> > even then. I noticed species in our yard that you have to be in the
> > hills to find now, like coronis frits and chalcedon checkerspots.
> > Looking back, in the short period of time from the early 70's to the
> > late 80's, I noticed a huge drop in numbers of butterflies. The
> > lemon bushes across the street regularly had Monarchs in numbers in
> > the spring and summer, as well as cardui, zelicaon and others and
> > LOTS of healthy honey bees. The Monarchs used to fill
> > the sky over at the beach in the fall. There were also a great many
> > Gulf Frits around the passion vines. The trees were loaded, even
> > then, compared with today's numbers. A very visible decline. It
> > seems the beginning of the end in California was around 1980.
> Richard, I also grew up in the San Francisco Bay Area in the late
> 60'/early 70's and worked there in the early 80's. I conducted Lincoln
> Index population estimates of some monarch overwintering sites in
> the region such as the one at Natural Bridges in Santa Cruz. Other
> researchers continued annual population estimates in the 80's and 90's.
> No one has noticed any pattern of decline in monarch numbers in
> in the region in 35 years of monitoring. True, there are wild year to
> year fluctuations and periods when there are 3 "good" monarch years
> in a row or 3 "low" years in a row, but no discernable upward or downward
> population trends. Ditto for the situation at the overwintering sites
> in Mexico.
> The decline in honey bees in San Jose, Calif. is understandable
> considering how many fruit orchards were removed from the region
> in the 70's and 80's and how many wild colonies of honey bees
> were wiped out by varroa mites.
> Zelicaon (Anise Swallowtail) is still abundant in the S.F. Bay
> Area (e.g. Coyote Hills Regional Park and Arderwood State Historic
> Farm in Fremont, CA ). Afterall, the host plant of zelicaon is an
> abundant and exotic urban weed (Anise). Cardui and the Calif.
> Tortoishell still swarm periodically through the Bay Area and Los Angeles
> (the former did last spring). I remember Gulf Frits being abundant
> in the 60's then dissappearing for many years following the Dec. 1972
> freeze that killed most of its host plants (garden passion vines).
> Another freeze in Dec 1990 knocked the passion vines back a seond time.
> To this day, however, the Gulf Frit has continued to be common
> butterfly in the milder, less freeze devastated parts of the Bay Area such
> as in Oakland and Berkeley.
> In sum, I do not agree with your view that there has been "a huge drop"
> in butterfly abundance in the S.F. Bay Area over the past 30 years -
> just some localized drops where new subdivisions and industrial parks have
> been built.
> Paul Cherubini
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