The most extreme example l know of Scrubjay predation involves baby Wood Ducks.
A conservation biologist based at UC Davis named John Eade had documented over
6000 Wood ducklings leaving their nest boxes at four study sites when he spoke
at OSU three years ago. As a native of British Columbia he was quite fond of
Scrubjays, a rarity there when he began life. Most nest box exits were
documented automatically with some very inexpensive hardware, but Dr. Eadd was
present for one occasion where the mother departed with the first four
ducklings . More continued to fall from the nest box and a Scrubjay grabbed
them one at a time and carried them to its own nest or some stash site. Then a
male California Quail appeared and easily drove off the Scrubjay. The surviving
four to half dozen ducklings walked off en masse with their non-webfooted
guardian. I've often wondered if they got an adequate diet under that foster
relationship. Dr. Eade did not hesitate to volunteer a compromised objectivity:
He no longer likes Scrubjays. The presence of coyotes in San Diego canyons
has been proven to benefit ground nesting birds because the coyotes eliminate
cats. Feral or domestic, they taste the same to Canis latrans. Wolves in turn
reduce coyote numbers when they are present. Coyote numbers have increased
dramatically in the Willamette Basin during my 2/3 century observation at the
expense of foxes. Foxes are extremely abundant in nw Europe/Scandanavia to the
point of being unhealthy for their own species. The current resurgence of Canis
lupus should bring them into balance. There are at least 12,000 wolves in
Europe west of Russia now, more than in the USA south of Canada. Will
the wolves stop the spread of golden jackals? This species we typically
associate with Africa had made it to Denmark in the past decade , where its
advance may be slowed by the 80 km anti-swine fence now "guarding" the frontier
with Germany. No credible biologist believes the fence will stop pigs(they are
accomplished swimmers) but it bolsters the Socialdemocrats' bone fides as
anti-immigrant. No humor or irony intended, l' m deadly serious. The
Socialdemocrats have recovered all the votes they lost to the Danish Peoples'
Party when they were perceived as soft on immigration. Sent from my
Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Jay Withgott <withgott@xxxxxxxxxxx>
Date: 10/1/21 6:57 PM (GMT-08:00) To: BOO List <boo@xxxxxxxxxxxxx> Subject:
[boo] Re: the suggestion that the absence of earth worms was a factor in robin
decline Jeff and all — In my neighborhood in SW Portland (Multnomah Village —
the “Village” part of the name would have been added by the influx of
well-meaning starry-eyed gentrifiers like me well after the time of your
childhood, Jeff), Fox Squirrels were common when we moved here 18 years ago.
Since that time, Gray Squirrels have steadily replaced them. Fox Squirrels are
now a rarity, and hang on in small numbers mostly in the larger parks as
opposed to the residential areas. Hybrids are fairly common, and I sometimes
now see squirrels that look to be likely backcrosses, seemingly 3/4 Gray and
1/4 Fox. So the Grays appear to be both outcompeting the Foxes and genetically
swamping them. Meanwhile the native Chickarees (Douglas Squirrels) continue
their long gradual downward trend; we have seen them roadkilled on several
occasions, and we expect them to be gone within the next decade as infill and
traffic continue to intensify. I actually have quite a lot of quantitative data
on all of this, but because there is no “E-Mammal” community-science database,
my data are cast about on countless scraps of paper and half-finished
spreadsheets and tucked away in folders and old laptops and whatnot, and I
probably will never find the time to put them all together into an accurate
graph complete with statistical analysis to prove my points.Re: Crows, I have
been of the opinion (or, I suppose to be honest, the presumption) that the
massive increase in Crows in Portland is a major contributor to an increase in
nest predation on songbirds and thus a decrease in songbird populations. Your
observations from Virginia, Lori, are interesting, so perhaps I’m wrong. And
one reason I could be wrong actually involves Scrub-Jays. In my neighborhood
in the early days we were constantly battling the Scrub-Jays who seemed to be
everywhere at all times and destroying virtually every passerine nest we knew
of. They would patrol vigilantly from treetops for days just waiting for a
Chickadee nest from one of our boxes to fledge, and then would swoop down and
attack the fledglings before we could do anything about it. But, in recent
years as the Crow numbers have skyrocketed, Scrub-Jay numbers have fallen
considerably, and they do not seem pose the same level of threat to smaller
nesting birds. My GUESS is that the Crows are essentially keeping the
Scrub-Jays in check. Perhaps Crows are attacking enough Scrub-Jay nests —
giving them a taste of their own medicine, as it were — that they have put a
dent in the local population. This is all anecdotal, but the human mind likes
anecdotes.Jay WithgottPortlandOn Oct 1, 2021, at 9:59 AM, Jeff Gilligan
<jeffgilligan10@xxxxxxxxx> wrote:Hi Jim and allScrub Jays were common in my
neighborhoods long before the collapse of the robin populations. While I was
going to wait until I had more time, I will summarize my long history with
Scrub Jays in the Portland area. Gabrielson and Jewett’s Birds of Oregon
referred to a Scrub Jay colony on Sauvie’s Island, which implied that they were
not generally in urban Portland. As a kid I the 1950s and early 1960s they
were absent and then scarce, before gradually becoming common. In perhaps
1962 or so, I had a bit of an interest in birds after having been on bird walks
as even a five year old. One Sunday my mom and sister had walked home from
church, and met a guy who was feeding what they called Blue Jays by hand. I
was interested, and went to the location about ten blocks away. The guy
agreed to feed the jays, and he went into the front yard with bread in his
hand. Two Scrub Jays soon arrived and fed from his hand. To this day, I have
not seen Scrub Jays respond like that, though I have hand-fed Gray Jays a
number of times.Over the next several year, Scrub Jays started appearing in
various areas of the neighborhood.Many years later, my mom who was at the time
feeding Scrub and Stellers Jays, told me about a bird he had never seen,
describing it the size of the jays, with a crest, white under-parts, and a
checkered pattern on the wings. I said it was probably a Blue Jay, to which
she demurred, since she was still calling the other two species Blue Jays, but
had to change her identification when I showed her an illustration of a Blue
Jay.Jeff GilliganOn Oct 1, 2021, at 4:52 AM, jim destaebler
<jdestaebler@xxxxxxxxx> wrote:
Hi All, Just to flog this subject a bit more, what about Scrub-jays?
From natives of the northwest, I've heard that they have only been here since
the eighties some time. I spent years working on passerine nest monitoring
projects, and they are a common cause of nest failure. Robins are very tight
sitters and something as small as a Scrub-jay might not cause a Robin to
immediately give up a nest, but Scrub-jays are very persistent predators.The
absence of Robins is probably the result of a combination of factors, including
local reproductive failure. A lack of birds immigrating to vacant territory is
also part of the picture.Jim
