The status of Red-shouldered Hawk in Santa Clara County is described
in the Breeding Bird Atlas of Santa Clara County, California. A
brief summary is that this hawk was very rare in the county until
the early 1970s, when numbers increased rapidly. Using data from
the Palo Alto and San Jose CBC's that date back to the late 1950s,
the population increase through 2005 was about 13% a year within the
Palo Alto count circle and 17% in the San Jose circle. Both counts
have had good coverage over the last 50+ years and exceed the 95%
percentile for party-hours for all United States CBCs.
We started a summer bird count in the Palo Alto circle in 1981 and
the summer population increase was less than the winter numbers,
about 5% a year. Both the winter and summer increases show a p
value of less than 0.004.
Based on Bob Barnes's message, I've looked at the summer numbers
through 2016. The population increase is now closer to 3% per year,
rather than the earlier value of 5% a year. There has been a
decline in the total birds counted in the last three summers, but it
is not clear if this is an artifact of the normal variance of a
large data series or the start of a changed trend.
On 5/3/2017 4:22 PM, Bob Barnes bbarnes@...
See below for email message from noted bird guide artisit,
naturalist John Schmitt re Red-shouldered Hawk 80 to 90
territory abandonment in SoCal.
I think it would be good to learn through our observations
if a decline
is taking place elsewhere in California as well.
Serving as the messenger for John Schmitt,
Bob Barnes, Ridgecrest, Kern County, California
03MAY17 from John Schmitt...
I learned of some troubling news about Red-shouldered
Hawks; I was
in San Luis Obispo County (Morro Bay, Montana de Oro, San
Santa Margarita Valley/ Santa Margarita Lake-all prime
Hawk localities) on 26 APR leading some friends of mine on
birdwatching tour (with a strong emphasis on raptors). We
failed to either see or hear a single bird. I mentioned
this to Peter
Bloom (a well known long time raptor researcher) and his
"I'm not surprised". He went on to relate that there has
been a severe
population decline in Orange, Los Angeles, and San Diego
Counties (80 to
90 percent territory abandonment in some localities).
uncertain, but Pete mentioned that some thought
agrichemicals or West
Nile Virus may be involved. So I will be taking special
note of when
and where I see/hear Red-shouldered here in the (Kern
River) valley and
I alert you to perhaps do the same and maybe pass the news
on to others.
Good chatting with you.
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