Coastal Ruddy Turnstone declines
- David Suddjian’s post of a few days ago about declines in Ruddy Turnstones along the Santa Cruz coast inspired me to dig through the Northern California coastal Christmas Counts. Even given the well-known limitations of Christmas Count data, it seems clear that something is going on—at least along the coast from San Francisco to Monterey and at least in the last 5-10 years.
For what its worth, here’s what I found:
I looked at 11 coastal counts from Del Norte down to Monterey. After eliminating counts that either lacked significant numbers of RUTUs or have not been consistently compiled over the last 20 or so years, I was left with seven counts with analyzable data—West Sonoma, San Francisco, Crystal Springs (San Mateo coast AND west SF Bay shoreline), Ano Nuevo, Santa Cruz, Moss Landing and Monterey Peninsula.
Looking at the counts individually, it appears that five (Monterey, Santa Cruz, Crystal Springs, San Francisco and Ano Nuevo) have seen significant drop-offs in RUTUs in the last 5-10 years. In some cases, counts that consistently recorded 20-50 birds in the 70’s and 80’s are recently finding few or none. It is interesting that the two counts with the steepest declines (Monterey and Santa Cruz) are on either side of a count that has not shown any clear decline (Moss Landing). The other count that seems to be yielding typical numbers is West Sonoma.
When one combines all seven counts and looks at the average number of Ruddy Turnstones reported per count circle by year, a trend is evident (I’ll send the spreadsheet to anyone interested). If you just look at the six counts from San Francisco south that trend is more pronounced.
Looking at average numbers of RUTUs per count and comparing the decade from 1985 through 1994 to the seven years since 1994 one finds:
All seven counts: 85-94 = 26 +/-9
94-01 = 14 +/-6
Six counts from SF south: 85-94 = 24 +/-8
95-01 = 12 +/-6
I also looked at two SF Bay counts (Oakland and Hayward-Fremont) that generally report similar numbers of Ruddy Turnstones as the coastal counts. The Oakland count shows a decline similar to the coastal counts while the Hayward count seems relatively stable.
What, if anything, this all means is unknown, but it does bear watching over the next few years.