9/26/11
The conditions were practically balmy. You have
to go all the way back to June 6 to find a lower
temperature and, perhaps partially as a result,
we had a large and generally happy group of eight
walkers. The number of species was a modest 15
and this seems to largely reflect our picking up
just three from Alan's list of standards (we
typically pick up six or seven).
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
This seems to be the year of the chickadee. If
you combine all sightings of mountain chickadees
between 1986 and 2010, you get nine, never more
than two in any given year. For 2011, we have
three so far, a quarter of total sightings for
Caltech's birdwalk. Nor is this a single bird.
This week we saw a chickadee in three widely
separated locations. Now, perhaps this is one
bird with an odd sense of humor or a weirdly
timed foraging pattern but I don't think so.
This is THE YEAR of the chickadee. As I
mentioned in a previous walk report, there is a
tendency for juveniles to disperse to the
lowlands after fledging but we've been seeing
unusually large numbers of chickadees on walks
and people have been telling me about the
chickadees they've been seeing in places like
their back yards. Often they haven't seen any
mountain chickadees during the Summer or Fall in
years or even decades. This is a bumper crop for
us and it is either a really good thing,
reflecting a bumper crop of juvenile chickadees,
or a really bad , such as a conifer crop failure
leading to serious habitat pressures. In the
latter case, we may be seeing adults as well as
juveniles. Naturally, I prefer the former
explanation to the latter.
Sometimes the word for bird is birthday, a
marking time of celebration or anxious
prevarication (we all know which when we are).
The day may be known in advance or it may be a
season's coming, not engaged through the ticking
tide of an autocratic calendar but established
through the delicate tangency of an avifaunal
tell. This week it was the timing of Kent that
brought the season to the rest of us. He noticed
a warbler dancing through the leaves in a tree
just south of the Tournament Park parking lot,
gleaning for arthropods and oblivious to
searching eyes. At first Kent got only back and
tail, teasers daring him to make a call but he
couldn't bring himself to do it. Perhaps he had
an orange-crowned warbler. Perhaps it was
something entirely different. Finally, after
numerous hops, Kent had a broadside and we had a
Townsend's warbler, the first of the season.
Sometime around week 40, we start to see
warblers. Some of these, like Yellow and
Wilson's warblers are mostly heading south and we
either catch them migrating by during a brief
window or we don't. For orange crowned warblers
it's an exchange. There are birds dispersing
from Alaskan breeding grounds who plan to stay
here for the winter and our much less numerous
summer locals who, having stayed here for the
summer, start heading back out to the Channel
Islands. Other warblers like yellow-rumps,
black-throated grays, and Townsend's warblers
also wintering here. Among these, the Townsend's
are generally here first.
Of course, our birds are special birds. There are
two leaves to the Townsend's warbler's breeding
portfolio. Most of them breed in mainland
British Columbia and southern Alaska and these
birds migrate to Mexico and Central America.
It's possible that we see some of them as they
move north or south but the "literature" seems
pretty unclear on the matter and, perhaps, we
don't actually see any of them. On the other
hand, we do see our winter Townsend's warblers.
They breed exclusively on Victoria Island and the
Queen Charlotte Islands off of British Columbia.
Although they look very similar to their mainland
brethren, our birds have measurably shorter wings.
Usually, when you think of an old growth poster
bird, it's the Northern Spotted owl but the
Townsend's warbler is also an old growth canary.
They like to nest in mature spruce and do
noticeably poorer when forced to smaller trees or
there is too much open canopy in the vicinity of
a mature tree. They do not fare at all well in a
managed forest or even in old growth forest near
clear cut areas (presumably due to higher
predation levels). Enjoy them while you can.
The date: 9/26/11
The week number: 39
The walk number: 1110
The weather: 67°F, partly cloudy
The walkers: Alan Cummings, Viveca Sapin-Areeda,
Carole Worra, Melanie Channon, Kent Potter, John
Beckett, Hannah Dvorak-Carbone, Vicky Brennan
The birds (15):
Mourning Dove
Anna's Hummingbird
Crow
Mallard
Bushtit
Mountain Chickadee
Black Phoebe
Lesser Goldfinch
Red-masked Parakeet
Band-tailed Pigeon
Red-whiskered Bulbul
House Wren
Townsend's Warbler
Common Raven
Hummingbird, Selasphorus
--- John Beckett
Respectfully submitted,
Alan Cummings
9/29/11
http://birdwalks.caltech.edu/index.html
9/19/11
It was a multigenerational Cummings extravaganza
as Travis, Alan's son was with us. He's only
been on the walk a couple of times previously
(last seen in 2004), making him a quarter % level
occurrence, but he has what must be some sort of
genetic thing within the Cummings clan, a
natural, seamless and, I think infectious,
approach to birding. I was especially impressed
by his sense of direction with sounds and, of
course, the home run luck he brought along. We
had some really interesting birds among the 14
species we picked up but, like the sultan of
swat, we also struck out a lot with no hawks or
other soaring birds, no house sparrows, and no
mourning doves.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
So, what is the highlight bird of the week? We
actually have a variety of plausible candidates.
Vicki brought an orange-crowned warbler (probably
a late Channel Island bird) to the beginning of
the walk and Travis caught a mountain chickadee
(a one % occurrence bird) at the end. The
chickadee was foraging high in the canopy above
the Millikan ponds. Both of these species are
fine rare birds for us but each of them has taken
a recent turn as the highlight bird of the week.
So, when the pretenders step aside, there is
really no question that the highlight for this
week was a juvenile great blue heron working
along the southern shore of the lower Millikan
pond. This is only our fifth great blue heron
sighting on the birdwalk (i.e., a half percent
level occurrence), so it was a pretty
extraordinary culmination to the walk.
The first Caltech occurrence of a great blue
heron, although not on a bird walk day, actually
made the LA Times (check out the first entry in
the publicity section, which is from 1989).
Travis had seen our bird earlier in the day but
not later, so we were hopeful but not expectant
as we walked up to the Millikan ponds. We arrived
to find a heavy entourage of groupies lining the
walkway north and east of the lower pond. They
were pointing excitedly and snapping pictures.
The heron was on the southern side thinking about
options given the large number of potential
predators. He calculated interference potential
and decided that security was acceptable along
the southern perimeter and started moving over to
a viable hunting position. He was surprised by a
moving rock that he had planted a foot on (a
turtle), which led to a brief flutter, but he
recovered quickly and kept moving. We didn't see
him get anything but the pond has plenty of fish
of variable size and maybe even an edible turtle
or two.
Our coastal great blue herons are resident (i.e.,
non-migratory) but juvenile great blue herons
like ours disperse within a few weeks of
fledging, probably in June or July, and only 10
or 20% of them make it through the first year.
Our bird has only been on his own for a couple of
months. He appears to have discovered how the
urban cornucopia can provide food for a hungry
bird but it's less certain that he also
understands the equally stark dangers. Typical
of his species, our bird was alone in foraging
(great blue herons are locally territorial) and
looking for fish (they also go after small
rodents, birds, reptiles, insects, crustaceans,
and amphibians, basically animate anything that
moves that he also thinks he can swallow.
I've seen conflicting rationalizations of the
name great blue heron so I'm not sure what to
tell you. It is generally asserted that the blue
in great blue refers to the blue tinged gray
feathers covering much of the body but I've also
seen it claimed that the blue in the name refers
to the lores (the feathers between the eye and
the bill). During breeding season, these
feathers are a genuinely sharp in your face blue.
The lores make more sense to me (there's no
mistaking that color) but pay your money and take
your choice.
So, now we come to the question of the day:
"What's the difference between a heron and an
egret?" I was once asked this by a fellow
passenger on an airport shuttle who noticed that
I was reading a book on acorn woodpeckers, which
apparently suggested that I was some sort of bird
expert as opposed to the actual case of my being
generally bird ignorant but curious about the
acorn woodpeckers in my neighborhood. My
response was "Heron starts with H and egret
starts with E". I was being a little facetious
(it did get a laugh) but not entirely. Egrets
and herons are both wading birds with S-shaped
necks that fly (neck folded up in a tight
S-shape) and hunt similarly. They are all in the
heron family (Ardeidae; i.e., all egrets are
actually herons). It's not a matter of size.
Great egrets are not that much smaller than great
blue herons and are much bigger than the smaller
herons like the green heron we occasionally see
on campus. It's not a matter of color. Herons
tend to be colored and egrets white but reddish
egrets are fairly dark and juvenile little blue
herons and the white morphs of great blue herons
are white. So what's the difference?
Basically, it's a matter of taxonomically
tortured guesswork on the part of nineteenth
century naturalists who were overly impressed by
feather plumes but the differences can also be
seen through the prism of high fashion. Ladies
of the late nineteenth and early twentieth
century required massive quantities of feathers
for their hats, hair, and dresses. If you were
unfortunate enough to be a heron that produced
showy plumes, you were probably an egret and in
serious trouble. If you were somewhat less
attractive to the millinery trade, you were
probably a "heron" or a bittern (another type of
heron).
Great blue herons were hunted for their feathers
but they don't have much in the way of plumes, so
their losses were as nothing compared to what the
egrets went through. At the turn of the century,
prime great egret plume feathers, which are
produced during the breeding season, were worth
substantially more than their weight in gold
(several birds to the ounce). Of course, the
guys with the guns never saw more than pennies on
those dollars but even the crumbs of the industry
fed a lot of economic incentive and it's not
surprising that carnage followed with millions of
birds being killed every year. Nor was this
restricted to egrets. I once read a birding
report from the late nineteenth century in which
the author describes his birding trip, a tour
through a lady's hat. His list of two dozen
species was an echo of the prematurely dead. The
most popular species marked for death changed
with abundance and style and the Audubon Society,
whose founding one could reasonably say was born
in fashion, was somewhat successful in exposing
ladies of culture to the consequences of their
millinery preferences. Moving ladies off of
great and snowy egrets was, however, not entirely
good news. Other birds replaced them.
Apparently it took a while for the ladies to
figure out that retaining a fashion forward
feather orientation without a snowy egret simply
meant that some other species (or perhaps many of
them) would be used to fill the gap.
Feather-inspired bird hunting died away only when
fashion decided, more or less of its own accord,
to move away from feathers. So, can we use
fashion designers to motivate taxonomy?
Certainly, but its not phylogenetically reliable.
Fashion lives in its own world and, while the
subtleties of crepe may breed in many lanes, the
choices made in fashion often bear little
connection to any natural genetic reality.
According to DNA, great egrets are more closely
related to great blue herons, whose feathers were
much less desirable, than they are to snowy
egrets, whose showy plumes, like those of great
egrets, very nearly led to their extinction. Some
egrets belong with classic herons and some
classic herons belong with the egrets. It's a
mess but it's an entrenched mess. Get used to it.
The date: 9/19/11
The week number: 38
The walk number: 1109
The weather: 82°F, full sun
The walkers: Alan Cummings, Travis Cummings, John
Beckett, Tom Palfrey, Vicki Brennan
The birds (14):
Scrub Jay
House Finch
Anna's Hummingbird
Acorn Woodpecker
Crow
Red-masked Parakeet
Downy Woodpecker
Black Phoebe
Orange-crowned Warbler
Lesser Goldfinch
Band-tailed Pigeon
Great Blue Heron
Mountain Chickadee
Bushtit
--- John Beckett
Respectfully submitted,
Alan Cummings
9/23/11
http://birdwalks.caltech.edu/index.html
9/12/11
The weather was flirting with being nice, which
was a big improvement over the previous several
weeks, and we had seven walkers, the most since
June. The number of bird species was a much less
impressive 14 but I feel the sensing aura of
transition as the great nadir of summer birding
cracks like the Spring ice on a river, slowly at
first, groaning the loss and, perhaps, settling
through a cold spell, but then breaking in the
steadily cascading riot of winter plumage.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
Between weeks 35 and 40 or so, we begin to see
winter residents like white-crowned sparrows,
American goldfinches, American robins, cedar
waxwings, and various warblers. Do we have the
cusp of a great winter? I don't know but I intend
to find out.
This week, Beth caught a flock of cedar waxwings,
the first of the season and the earliest first
Fall sighting we've ever had, so there is no
thinking about who the bird of the week might be.
This was not a close view but there was an aural
component and this flock was the announcing drum
of season. The Fall is here. Usually, we see
cedar waxwings in flocks of dozens and,
occasionally, hundreds as they winter here or
pass us by heading south. They act as if
following a hive mind and are constantly looking
for concentrated food sources, bushes and trees
full of berries capable of feeding the flock.
Cedar waxwings are elegant looking birds but not
fast learners. The individual cedes thought to
the flock. A flock of cedar waxwings alights
upon a suite of bushes on a Texas highway median
and starts to work the abundant berries.
Something disturbs them and the flock blasts up
right into passing traffic. The flock is safe
but two birds die. It twirls for a moment and
settles back into the berry bonanza being offered
by the median. They eat again but something
disturbs them and the flock flushes into the sky.
One or two birds die. This goes on for weeks and
hundreds die. We give on the one hand and kill
on the other. Cedar waxwings are highly
vulnerable to habitat loss, reflective windows,
and traffic near fruiting bushes.
I had thought that cedar waxwings were obligate
frugivores, that is, birds that eat solely fruit
and the enclosed seeds. This is essentially true
during the winter when we see them. However,
they will eat flowers if there are no berries and
they actually eat a fair amount of insects during
the summer, mostly at high yield sites like major
hatchings but also through gleaning while looking
for fruit. Cedar waxwings also engage in the
occasional flycatching exercise, although they
aren't particularly good at it. I don't want to
give the wrong impression. If you add it all up,
the annual diet of a cedar waxwing is still about
85% fruit. Chicks tend to get fed insects very
early in life but they are on a full berry diet
by the time they fledge. Unlike most open
nesting birds their size, cedar waxwings don't
have a lot of trouble with cowbirds, which are
nest parasites. Cowbird chicks can't handle an
all fruit diet and they starve to death before
they can fledge no matter how often their
surrogate parents feed them. A female cowbird may
be able to lay an egg in less than a minute and
lay more than thirty in a season but if the chick
is guaranteed to die, it's probably not a
productive exercise and you are likely to move on
to a more accommodating species. For the most
part, cowbirds seem to have this one figured out.
One aspect of cedar waxwings that I find
intriguing (probably my eight year old
subconscious talking) is that they have a very
fast throughput for digestion. The berry you see
being eaten now is coming out the other end in
twenty minutes. This is really fast for a bird
but remember that berries are at their best for a
limited period of time and you can only hold a
limited number of berries in your body at any
given time. By having fruit pass through the gut
quickly, you are maximizing the total number of
berries you can eat while they are still there to
be eaten.
Cedar waxwings don't actually sing but they do
have a variety of calls they use for communication
within the flock environment. They vocalize at a
very high frequency but those with acute hearing
can pick it up. My cat, Gentille, could pick it
up and it is through her that I too could "hear"
them. Sometimes, a winter rain would leave a
blue glass day and we would go birding together.
I open the window and the damp earth lifting the
air would leave her breathing the pale shadows of
the evening into flaring nostrils. She would
give them life and, in moments, resolve who had
lived and who had died, who killed, who came into
her yard, and who had pissed on her azaleas. She
knew them all and, one by one, she'd soothe them
into the dawn where the feathered voices beckoned
to her ears and I, standing on the wharf, would
follow those twisting creatures of the now and
watch her sail into a flock of cedar waxwings.
There is no line of sight but her ears say six
for sure, chortling over pittosporum berries and
calling to each other, out of their minds and far
beyond me. The berries are too high for prey but
she likes their calls and stays, touring bird to
bird, until finally sated, they choose to fly
away. I, kneeling through the glimpsing door of
her ears, watch them go in sheets furling like a
flag against the evening. In her dream, in my
dream, they sing again in their brightly colored
echoes but they play a little closer to the
ground.
The date: 9/12/11
The week number: 37
The walk number: 1108
The weather: 82°F, sunny
The walkers: Alan Cummings, John Beckett, Kent
Potter, Hannah Dvorak-Carbone, Vicki Brennan,
Beth Moore, Melanie Channon
The birds (14):
Rock Dove
Scrub Jay
Mourning Dove
House Finch
Anna's Hummingbird
Crow
Red-masked Parakeet
Bushtit
House Wren
Cedar Waxwing
Black Phoebe
Lesser Goldfinch
Hummingbird, Selasphorus
Yellow-chevroned Parakeet
--- John Beckett
Respectfully submitted,
Alan Cummings
9/16/11
http://birdwalks.caltech.edu/index.html
9/6/11
It was another tough hot day, 94°F at the start
and 99°F by the end of the walk. Yes. Yes. It
could have been worse and we were, admittedly,
well under the record of 108°F (fortunately, for
me, I wasn't on that one). The birds were not
receptive to the idea that they should be
cavorting around in front of us in this hot
weather and we managed only 11 species, a tad
below the median of 13 and far below the week 36
record high of 18.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
The only good thing about
these totals is that they are, hopefully, the
last of the worst. Starting next week, record
highs are all in the twenties through the
remainder of the year and the medians climb
steadily.
Tournament Park and the driveway from Wilson
along the track usually hold the best birding of
our walk. Many of our highlight birds are found
in this area and, in fact, I suspect it's
actually most of them although I'm too lazy to
try and prove it. This time, we find a fairly
active collection of lesser goldfinches near the
gate before we enter the park but then it's an
avian ghost town, dead quiet. This was bad news.
I had walked through the gate thinking we might
get to 15 species or so, in spite of the
difficult conditions, but my expectations were
dropping by the minute. Even the crows were
silent. Finally, illumination comes. A large
bird breaks cover near George and flies across
the park towards the parking lot. He sees
banding on the tail and is "70% sure" that this
is a red-shouldered hawk. Kent and I had a
terrible angle on the bird and couldn't help, so
we were stuck with hawk species and not much
liking it. As George put it, "this was much
better than that" but it wasn't. The bird wasn't
talking (red-shouldered hawks are the most
vocalizing in our area). We hadn't gotten a good
enough look. We needed more. We move out into
the parking lot, hoping the hawk has decided to
stop in one of the trees there rather than flying
out of our range. It wasn't looking good but
then the hawk flushed once again and, this time,
it was Kent who picked up the best view. He saw
a lot of white spots on the back (I call them
spangles), too many and too prominent for a
juvenile red-tailed hawk, inconsistent with an
accipiter. We had a red-shouldered hawk.
Although the red-shouldered hawk was fun and
compensated somewhat for the several species we
might otherwise have picked up, the highlight
bird of the day actually came at the beginning of
the walk. George caught sight of two black spots
gliding across the campus above Millikan.
Binoculars revealed a pair of turkey vultures. A
dead graduate student mouldering in the sun might
have kept them on campus for a while but there
wasn't one, so they went gliding off to the south.
My subconscious vision of the way vultures feed
was polluted by childhood views of birds shoving
their necks into some rotted antelope carcass on
the African plains. Turkey vultures will
certainly not pass on a chance to eat at a large
carcass, like a deer, but the local socially
dominant turkey vultures will defend it so a
subordinate turkey vulture only gets to stand
around watching somebody else eat. Why bother?
It's much more productive to fly around and find
a chunk of dead rabbit or squirrel that you get
to consume all by yourself or with a few of your
social equals. Turkey vultures get by mostly on
a diet of small dead rodents.
Vultures apparently have a very good sense of
smell. One of the advantages of having a nephew
go through an "everything vulture" phase is that
you get to page through the Christmas vulture
books before sending them on and this left me
remembering an assertion from one of these books
that a vulture could detect a dead mouse buried
under a foot of manure from 200 feet up (that
little story was just too irresistible for my
subconscious eight year old to forget and it
apparently also impressed my nephew). Now, I
don't know if this is true (I haven't seen a
write-up for this particular experiment in the
literature) but I can tell you that in the 1940s,
oil companies would leak test their gas lines by
injecting small amounts of methyl mercaptan
(think rotten cabbage smell) and then drive along
the pipeline looking for turkey vultures. A
vulture investigating your pipeline gives you the
location of your leak.
Based on Alan's probability plot for turkey
vulture sightings, you are most likely to see a
turkey vulture in the early part of the year
(weeks 2-20 with a maximum around week 10) with
another burst around weeks 38-42. Most of our
turkey vultures are resident but there is also a
migratory component and that may account for the
blip in the Fall and some fraction of the early
year sightings. The number of turkey vulture
sightings on Caltech bird walks has been
increasing steadily. We've gone from 0-3
sightings per year in the 1980s and early
nineties to 6 or so in recent years (7 in 2010
and 7, so far, in 2011). If you take a three
year running average between 1997 and 2011, T =
0.3Y + 1.6, where T stands for the number of
turkey vulture sightings per year and Y stands
for the year number with 1997 being zero (i.e.,
we are accessing sightings data back to 1994, so
1997 is the first year with a computable three
year average). The r square for this is 0.9,
which implies a really strong correlation. Does
this mean that the population of turkey vultures
has exploded over the last decade? Well, no.
As the medical community seems to perpetually
rediscover, correlation does not mean cause. We
do not have twice as many dead rodents not
running around today as there were twenty years
ago. The secret is success but not that of the
vulture. The average number of walkers on the
Caltech birding walk has been increasing with
time since the mid-nineties and, if you plot
number of turkey vulture sightings per year,
again using a three year running average, against
the average number of walkers (W), you get T =
0.5W + 1.4 (r square = 0.7). It's not that there
are more turkey vultures (maybe there are but
this is not the way to tell). It's that each
extra pair of eyes scanning the skies for soaring
birds makes it more likely that you will see the
turkey vultures that are there to be seen. A
final feature of Alan's sightings data I'd like
to point out is that there are sinusoidal
variations about the first line I gave you with
peak to peak ranges of five or six years. There
are similar variations about lines describing
turkey vulture census counts for other parts of
the country when they are plotted against year.
This is probably an endemic feature of turkey
vulture life. I haven't seen it discussed but
this sounds suspiciously like the population
cycle for a local rodent (e.g., ground
squirrels). We are, perhaps used to the idea of
predator-prey populations cycling together
(usually with a time lag), so it really shouldn't
be surprising that the population of a scavenger
might also cycle with the prey. All right. I'll
say it. Turkey vultures are a part of the great
cycle of life.
The date: 9/6/11
The week number: 36
The walk number: 1107
The weather: 94°F, full sun
The walkers: John Beckett, George Rossman, Kent Potter
The birds (11):
House sparrow
Mourning Dove
House Finch
Anna's Hummingbird
Acorn Woodpecker
Crow
Turkey Vulture
Lesser Goldfinch
Red-masked Parakeet
Red-shouldered Hawk
Red-whiskered Bulbul
--- John Beckett
Respectfully submitted,
Alan Cummings
9/12/11
http://birdwalks.caltech.edu/index.html