Date: 9/15/20 2:46 pm
From: Al Eisner via <eisner...>
Subject: Re: [southbaybirds] Palo Alto and Alviso
On Mon, 14 Sep 2020, Bill Bousman wrote:

> Steve commented that he counted 14-16 Pectoral Sandpipers in New Chicago a
> few days ago.  This bird's passage numbers have changed quite a in the South
> Bay over the last 40 years.  I've attached a plot of the yearly maximum daily
> counts from 1981 to 2017.  From 1991 to about 2001 we had a period of large
> numbers of Pecs.  In the fall of 2001, we had a maximum daily count of 207,
> quite a show. The most recent year at all comparable to Steve's numbers was
> 2004 when we had 16.  Why these changes happen remains a mystery.  One always
> wonders if we've done something right locally and the birds came, or if we
> were just seeing the effects of a series of good nesting years in the arctic.
> Bill Bousman
> Menlo Park

Given the plot, Bill meant to type 1991 rather than 2001 above, Anyway,
in the two highest-count years, 1991 and 1996, the Pectoral flocks at
the Coyote Creek Riparian Station (then open to birders) were joined
each year by a Sharp-tailed Sandpiper. This also occurred in the
Pectoral year of 1997. Sharp-tailed arrival dates were (I think) the
end of September to early or mid October. I'm not suggesting the two
species came in together (I suspect most Pectorals are from the North
American breeding population, rather than Siberian, while Sharp-tailed
is strictly Siberian), but the rarer bird was perhaps attracted by the
Pectoral flocks (not all that dissimilar in size, shape, habits).
Bill probably has more information on the correlation.

Al Eisner

Al Eisner

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