Species and Community Profiles - San Francisco Estuary ...

Other Birds
Figure 7.1 Christmas
Bird Count data for
Snowy Egret — Approximate
geographic
location of Count
circles indicated by
dashed lines
National Audubon
Society’s Audubon Field
Notes, and its successor
publications, American
Birds, and Field Notes,
Volumes 24-51.
Marin County (southern), and Arroyo Cheap Thrills.
For all of these counts, the numbers are comparable and
show no substantial changes in the last 25 years. The
aggregate number of birds counted in the nine CBC
circles shown in Figure 7.1 can be approximated by
summing the mean number recorded on each count.
This aggregate mean, 1,112 birds, represents a lower
bound of the birds present in San Francisco Bay, as not
all estuarine habitats are sampled within these circles,
and it is likely that some birds were missed during these
counts. Comparisons of Palo Alto CBC and Summer
Bird Count (SBC) data obtained in the same count circle
allow a comparison of summer and winter numbers using
identical census protocols. These data show essentially
the same population in both the summer and winter
seasons, and it appears that this species is permanently
resident in this portion of the Bay.
Historical Distribution – Within California,
Grinnell and Miller (1944) considered the snowy egret
to be a year-round resident below the 1,000-foot elevation
level in the southern three-fourths of the State,
which includes the San Francisco Bay Area. Elsewhere
it was found only in the summer or as a vagrant. They
326 Baylands Ecosystem Species and Community Profiles
described the Sacramento, San Joaquin, and Colorado
River valleys as the chief location for this egret, but noted
that it was found coastally from Marin County south to
San Diego County.
Prior to 1880, this species was considered locally
common in the State (Grinnell and Miller 1944). Plume
hunting, however, was as devastating to this species on
the Pacific Coast as it was in the East, and starting in
the 1880s, this species was nearly wiped out in the State.
By the early 1900s, it was thought to be extinct within
California. By the 1920s, it was considered a rare straggler
to the Bay Area with only two locations noted
(Grinnell and Wythe 1927). By the early 1940s, however,
this species had started to recover and in favored
places was locally common. Even by 1940, however, the
only known breeding site was in Los Banos (Grinnell and
Miller 1944).
By the early 1950s, in the South Bay, this species
was considered an uncommon winter visitant (Sibley
1952). Emily Smith (Audubon Field Notes 9:51) considered
ten birds at Alviso on 30 August 1954 to be notable,
and this was the largest number reported for the Middle
Pacific Coast Region in that season. A survey of South