12/26/12
It is the end of the year. The sales are on.
The metaphorical chestnuts have all been
consumed. The wrapping paper has been ripped
away, revealing desire and disappointment. We
come to our last walk. How did we do? Our
species total for this walk was a modest 18 but
it capped a year totaling 1032 bird species.
This puts us in third place all time, behind 2011
(1088) and 2010 (1046). Are we good or are we
lucky? Most likely, we are neither. The number
of species per year can be treated as a linear
function of the number of person trips with an r
squared of 0.88, which is really good for a
natural phenomenon with a huge number of
potentially important contributions. In detail,
this has to be a nonlinear function that hooks
down to zero for no walks and flattens out at
some high, yet to be achieved number of walks.
There aren't an infinite number of birds to be
had, so the yield of birds per each additional
birder has to drop eventually, and if there
aren't any birders, it's hard to see how you get
any birds. Yes, the tree still falls and the
bird still sings but there is nobody there to
hear it. Although the correlation is real, there
is significant scatter around the line and it is
in the scatter that you must troll for variations
in the presence or absence of specific species on
campus, the great ears and eyes, the weather
conditions, the scatter level of the birders, the
number of walks in the year and the time it takes
to complete a walk. All this stuff is important
but it is second order. We are at the high bird
species end of the scatter, so it is fair to say
that we did reasonably well but, at the core, it
comes to a simple truism: more birders equals
more birds.
Our end of the year walk yielded a total of 18
species, slightly below the median for the week
(18 versus 19), leading to a negative score. We
were completely out of touch with the record high
of 28. Still, it was a very successful social
walk. The other Cummings, Travis, was with us,
as was Chip. Perhaps the good society depressed
the totals somewhat but if so, it is a trade that
I would make most any week.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
In birding news, the snowy egret is back at
Baxter pond and this gave us ten sightings for
the year, a new record (the old record was nine
set in 2002). With the startling exception of a
week 42 (Oct 15) sighting, earlier this year, all
of our snowy egrets have come in the winter
window between week 51 (mid-December) and week 16
(mid-April). Snowy egrets are a strictly
(almost) a winter/Spring bird for us.
I am tempted to talk about the snowy egret but,
instead, I think that I would like to say a few
words about a bird with baggage. Starlings don't
belong at Caltech, or in California, or Chicago,
or New York City, or anywhere else in North
America. They are old world birds derived from
one or both of two intentional releases in New
York City, 60 birds in 1890 and another 90 in
1891. It took a decade for the starlings to
establish themselves firmly within the city but
by 1920, they had a range encompassing a 1,000
square kilometers. It was over 12,000 square
kilometers by 1930, 25,000 by 1940, and 36,000 by
1950. Grinnell and Miller in their comprehensive
1944 book on California birds noted that a
starling incursion had only once been reported in
the state (occurred in the latter part of 1942).
By the 1950s, there were numerous stable breeding
populations within the state and, by the 1960s,
well before the Caltech bird walk had begun,
starlings had become endemic in California and,
presumably on campus (Alan was prescient in
organizing the walk but not prescient enough to
capture the onset of starling residency).
What's the secret to all this range expansion?
It comes in three forms. Once a starling breeds
in a particular area, it will do so for the rest
of its life (i.e., they are philopatric).
Juveniles, on the other hand, disperse far from
their natal territory; they will move tens to
hundreds of kilometers in search of new habitat
(the average is about 100). If they survive,
they establish new breeding grounds to which they
are loyal and the next generation moves further
out. The third key is a jingle that we made.
The starlings were pushing into areas in which we
had obliterated many of their most important
predators and over which we supplied ideal
foraging areas, pastures, feedlots, and urban
lawns. Thank you very much.
On the Caltech bird walk, we see starlings most
often during the breeding season with a
significant but sporadic presence during the
winter and a pulse, centered around weeks 39-40
that probably includes the contribution of
dispersing juveniles from other areas passing
through campus. We are least likely to see a
starling in the early Spring or in the Fall when
flocks are at their maximum size. We apparently
have starlings roosting on or near campus because
they are usually much easier to find during the
early morning or near dusk than they are around
noon when we would like to be seeing them. Once
they disperse from the roosting sites, however,
starlings can fly several dozen kilometers to
forage (usually more in the range of one or two
dozen kilometers), although it can be much less.
For a starling factoid, I offer you a serving of
angel rings. Early English radar operators of
the 1940s noticed faint rings emanating from
points on their screens with apparent speeds of
thirty or forty miles per hour. These features
were obviously too slow to be planes or rockets,
so they attributed the angel rings to some sort
of instrumental ghost and moved on. It wasn't
until well into the 1950s that angel rings
transformed from feathery ghosts to feathery
wings. Angel rings are caused by large flocks of
starlings leaving roosting areas and flying out
to foraging sites.
Starlings are secondary hole nesters. The
advantage to using cavities for nests lies in
their relative immunity against nest predation
and nest parasitism compared to open nests.
Crows and ravens can't get in and, although a
cowbird might be able to get in, she won't be
able to get out. A disadvantage is that an old
cavity nest is much more likely to have parasites
than an open nest. So, what can you do about it?
Terpenes! A male starling will fumigate a nest
by lining it with plants that yield, on average,
unusually high monoterpene emissions (and
emissions of other volatile compounds); he does
this a few days before he intends to start
advertizing the cavity and the nest result is an
antibacterial mat that also inhibits feeding and
reproduction in lice and feather mites.
Starlings have clearly ignored the best Medieval
human advice to bleed the malodorous vapors away.
We may have failed to figure it out but the
starlings know that your progeny are much more
likely to fledge if they aren't anemic due to
blood loss and they don't get sick because of the
pathogenic soup left by your predecessor.
Females choose in the starling world and, if your
potential mate is selecting for a high quality
cavity, excellent air fresheners, and a big
complex song repertoire, it behooves you, as a
male, to spend some of your winter looking over
the local cavity real estate, use terpeniferous
carpeting to generate that new cavity smell, and
burnish those songs.
Love comes easily to a male starling and he likes
to get a lot of it when he can. He will start
scouting potential sites long before the breeding
season. He wants to own multiple high quality
holes that are not too close together because the
ideal is two or three cavity nests with a female
and a clutch of several eggs in each. Once the
first (primary) female is thoroughly ensconced in
one cavity, he flies off to his next cavity and
tries to sing in another female. If his second
cavity is too close to the first, his primary
mate will fly out and try to entice him away or
attack her potential rival. Sometimes, it works
and her mate comes home or the potential
secondary mate is scared off. Sometimes, it
doesn't and she destroys any eggs in the
secondary nest (happens about half the time if
she is still incubating eggs of her own).
Sometimes, especially if the male has posed the
position of his second cavity and the timing of
his entreaties well, the primary female will
become an unwilling partner in the polygynous
world of starlings and her mate will end up with
two or more females. Mated female starlings
don't engage in affairs of their own very often,
although female rovers will engage in nest
parasitism, especially early in the breeding
season. Also, unlike those lothario sparrows who
will try to mate with practically anything of
similar size that moves, starling males are
mostly looking for full time mates, not one time
flings. Why does the primary female put up with
this behavior in her mate? She doesn't. As I
noted above, she will disrupt a secondary union
if she can. A secondary female is, however,
willing to work the polygynous angle, even though
she probably knows that she will get less male
participation in raising her brood than the
primary mate will and fledge fewer offspring than
she would have had she undertaken a monogamous
relationship. There is, nevertheless, a genetic
advantage. The sons of her polygynous union will
have a greater potential for successful
polygynous unions of their own so that, if you
count out to the second generation, the secondary
female in a polygynous relationship has more
grandchildren than she would have had via a
monogamous relationship with a less fit male or
no male at all (this is the so-called sexy son
hypothesis). Our starling has done the math and,
even accounting for all of the many problems and
difficulties of being a secondary mate, her
solution to progeny is a polygyny.
The date: 12/26/2012
The week number: 52
The walk number: 1176
The weather: 57 F, partly cloudy
The walkers: Alan Cummings, Travis Cummings, Chip
O'Connor, Viveca Sapin-Areeda, John Beckett,
George Rossman, Ashish Mahabal
The birds (18):
Northern Mockingbird
House Sparrow
Mourning Dove
House Finch
Anna's Hummingbird
American Crow
Yellow-rumped Warbler
Snowy Egret
Red-masked Parakeet
Red-tailed Hawk
Black Phoebe
Ruby-crowned Kinglet
Band-tailed Pigeon
Lesser Goldfinch
Bushtit
Turkey Vulture
Red-crowned Parrot
European Starling
--- John Beckett
Respectfully submitted,
Alan Cummings
1/15/13
http://birdwalks.caltech.edu/index.html
12/17/12 12/10/12 12/3/12
Pleasant walks are the distillation of a people
and the conditions. You have to like the people
and you have to like the conditions. Today, it
was cool but not cold, partly cloudy, with enough
sun to light the way but not so much that sun's
glare affected our ability to see any field
markings on our birds. We had a lively
collection of birders and, yes, I liked the
people. It was a pleasant walk. The walk was
also successful from a gross numbers perspective.
We had 23 species, which is, regrettably, below
the record of 27 set in 2009 but we were well
ahead of the minimum (11) and median (20) for the
day.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
Every good day has a highlight or two and this
walk failed to prove an exception. We did,
however, have to wait for the first highlight
until we get to Morrisroe. Up in a tree lapping
an adjacent yard off campus is a Townsend's
warbler. This is only our third Townsend's
sighting of the season, so he was a very welcome
bird but the rising heart was in the patience of
the bird, unusual for a Townsend's, and in the
art of the moment. A Townsend's warbler provides
a natural contrast of yellow and black,
invariably against a canopy of green. What made
this encounter special was the addition of
clusters of large red berries that the warbler
was periodically working through. It was like
dappled light in the seeming of a dream.
Caltech recently put in a small park on Wilson,
bounded by the south parking structure and
various buildings associated with student
housing. Apparently, Caltech has realized, and
continues to realize, that small open spaces can
be more important in defining the ambiance of the
campus than the largest ones are. The new
minipark on Wilson has a plot of Mexican sage
that should be attractive to hummingbirds and a
large pergola with a lot of visual potential,
although it is in serious need of vines. The
minipark is still a little prissy but once some
of the plantings mature, I think it will become a
popular way station. So far, the new pergola and
minipark have been a disappointment in terms of
birds. We see or hear the odd house finch but I
have yet to see a hummingbird working the Mexican
sage, although I admit that this, at least, is
likely a matter of our bad timing. I can't
believe there isn't a resident owner of the patch.
Today, we walk north on Wilson across the street
from the minipark and see a flock of several
dozen birds at the back of the lot. They are
likely to be lesser goldfinches, a species we
already have, but there is a reasonable
possibility that this is a mixed flock with at
least a sprinkling of American goldfinches. So,
Viveca and I wander across the street in search of
the less than obvious. We find, at the end of
the park, a gum tree with a levitation of hobnail
Christmas bulbs, green and brown with russet
hands flapping in a light breeze. Usually this
tree is empty except for leaves and seed pods
but, today, there is a smattering concert of
yellow, dozens of buttons opening and closing in
rippling waves that end in a great whoosh as a
mixed flock of goldfinches flashes across the
garden. We had our American goldfinch but a
richly caparisoned coat had become a threadbare
skeletal rack and the mating contrasts threatened
a decorated Christmas tree with a Timothy Burton
sketch. For a moment, I am intrigued by the
suddenly empty store and stare into the flagging
leaves and hobnail ornaments but then I turn to
follow the flock. Viveca is calling excitedly
and she draws me to another tree where she has
spotted an anomalous bird. She thinks. She
hopes. She knows. It is a black-throated gray
warbler, her favorite bird species.
I confess that I also have a great fondness for
black throated gray warblers. They are just too
elegant for words. However, we have been spoiled
recently and that is a worrisome aesthetic. In
the 1990s, we typically saw one or two black
throated grays a season and never more than four.
The winter of 2002-2003 yielded seven, perhaps a
symptom of the well-known Feenstra effect, as the
following season dropped back down to one sighting.
However, the numbers then started jumping up,
with five to seven each season between 2004-2005
and 2008-2009. In the winters of 2009-2010 and
2010-2011, we saw 14 black throated gray warblers
each season, driven largely by wintering birds in
Tournament Park. Unfortunately, black throated
grays appear to have abandoned Tournament Park,
as have the Townsends. Last winter (2011-2012),
we only saw three black throated grays and
Viveca's bird is the first of the 2012-2013
season. If you consider the pattern of sightings
by taking a four year running average on a
seasonal basis (i.e., you count from mid-year to
mid-year rather than using a calendar year) to
smooth out some of the noise, we hit a local
maximum, keeping in mind that there is a lag
because of the averaging, in 1993-1994 (3), a
minimum of 1 in 2000-2001 and another maximum
(10) in 2010-2011. This year, we completely
missed the Fall migration birds that must have
been passing through campus (hopefully) around
week 40. Were we so confused by the sudden
profusion of yellow-rumped warblers that we
missed the black throated grays, even though they
were present? Maybe, but I suspect not.
Usually, the first black throated grays show up a
week or two before the yellow rumps. We just
missed them. So, I'm hoping that Viveca's bird
proves to be a campus resident for the rest of
the winter with a schedule amenable to viewing.
Last winter may not have been the first toll of a
sharp decline to the one or two a season pace of
the 1990s. We may be lucky.
Since we saw both a Townsend's warbler and a
black throated gray, it seems appropriate to
compare sightings patterns for the two species.
If you take the four year running average on a
seasonal basis for Townsend's warblers, there is
a maximum around 1993-1995, a minimum around
2002-2004 and another maximum in 2007-2008. The
most recent minimum and maximum are phase shifted
relative to black throated gray warblers but the
overall pattern is similar. The pattern for both
birds appear to reflect effects that are larger
scale than the Station fire (2006) as the cycles
for both birds are operating independent of this
local anomaly with very long wavelengths, roughly
15-17 years. This is not a case of having some
devoted winter resident because 15 years, or even
half of that, greatly exceeds the life expectancy
of an individual bird. We are dealing with the
statistics of small polluted numbers of
observations due to a variety of effects like a
variable number of birders and individual birds
contributing multiple sightings, but the I will
speculate that the long wavelength is likely a
consequence of large scale effects on the
population dynamics of the two species and that
this is occurring either in the breeding
territories or on migration, since the two
species probably don't come to us from the same
place and probably don't follow the same
migration route The impacting cause, whatever it
is, affects different areas in the regions that
these birds breed in or pass through at different
times and this leads to variations in timing for
numbers of seasonal sightings on our walk.
The date: 12/17/2012
The week number: 51
The walk number: 1175
The weather: 63 F, partly cloudy
The walkers: Alan Cummings, Viveca Sapin-Areeda,
Carole Worra, John Beckett, Vicky Brennan, Kent
Potter
The birds (23):
Mourning Dove
House Finch
Anna's Hummingbird
American Crow
Yellow-rumped Warbler
Mallard
Black Phoebe
Bewick's Wren
Bushtit
Townsend's Warbler
Red-tailed Hawk
Band-tailed Pigeon
Ruby-crowned Kinglet
Lesser Goldfinch
Turkey Vulture
American Goldfinch
Black-throated Gray Warbler
Cedar Waxwing
Hummingbird, Selasphorus
Common Raven
Yellow-chevroned Parakeet
Snowy Egret
House Wren
--- John Beckett
Respectfully submitted,
Alan Cummings
1/8/13
http://birdwalks.caltech.edu/index.html
Sometimes the worst is best. Suffering is
transformed into fortitude. In an empty forlorn
abyss there is a new world in a complex of subtle
shades. There can be beauty in a curtaining
darkness. A dark grief becomes a Taj Mahal. You
flick the curtains and find light. We can learn
from devastation. We must learn from
devastation. Last week we had what is easily the
best December walk of all time with 31 species to
show for the exercise. This week, we are in
serious danger of falling into a single digit
morass with only a late band-tailed pigeon saving
us from a self imposed but mild form of infamy.
So, I troll the waters of our walk for an emerald
in the mud and find the discovery of the week:
entropy is conserved. If you split the
difference between last week and this week, you
have two nice twenty bird days. With a ten bird
day, you can only dream of twenty. Perhaps, next
week will be better.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
We had a ten bird winter score and a hard day for
highlights. So, rather than torture myself
trying to squeeze blood out of a turnip, I will
move straight to the bird of the day. My first
response to this walk was that choosing a bird of
the day was going to be difficult. The walk
contains no rare birds. There were no stellar
views of the birds that we did see and hear.
However, I have previously discussed only nine of
the ten species on today's list. This leaves me
arriving at the door with a bird cupped quietly
in my hands and I sing, for it is almost
Christmas, and forget, for a moment, that I do
not sing anymore. It is the mourning dove that
brings me to a foyer glide and I see a turquoise
ring.
As a factoid, I note that there are currently
more mourning doves than people in this country,
at least during the Fall migration, about 400
million. That's not something you can say of
very many birds and it is a testament to mourning
dove breeding patterns. A pair of mourning doves
will rarely have more than (or less than) two
eggs in a clutch as this seems to be optimal for
fledging but they can do several clutches in a
year. That's a good thing because everybody
likes a mourning dove. Cats, snakes, and hawks
are all major predators. We kill and eat about
20 million mourning doves a year ourselves,
through hunting (39 of the lower 48 states allow
mourning dove hunting). Since it takes five or
six shots to put one dove in a hunter's bag, on
average, we also kill some more doves than we
admit to because we leave a lot of lead shot on a
field. Doves like to consume lead shot lying on
the ground, which leads to lead poisoning, which
likely leads to reduced long term survival rates
and fecundity although this secondary consequence
of hunting appears not to have been well studied.
Now, I'm not going to complain about dove hunting
in this country. If you want birds to shoot at,
you have to support practices that encourage
stable bird populations. This leads to egregious
bird killing gimics like baiting (e.g., salting a
shooting zone with grain or salt) becoming
illegal. It leads to controlled seasons, bag
limits, changes in agricultural practices to
encourage year round populations, and, when
necessary, moratoriums on hunting. It leads to
money flowing from urban to rural areas without
direct government subsidies. It leads to bird
studies designed to help understand population
dynamics of game birds but this also leads to
better understanding of population dynamics for
other bird species. Mourning dove populations
have been declining recently in states that allow
dove hunting. "Ah," you say, "hunting is bad.
Let's stop the hunting." This would not,
however, be the appropriate response. We find
these things out because Fish and Game
departments in many states are attempting to
manage game bird populations so that hunting can
be supported. The root cause of declines in
mourning dove populations is much more likely to
be habitat loss than hunters. It's in building
parking lots over fields and reforestation
through decreased agriculture, leading to fewer
open ground fields with seeds scattered around. It's
not a simple problem because there are a lot of
interlocking pieces that affect many species but
I will assert that removing hunters will
increase, not decrease, the probability of losing
bird species in this country.
Ok. I am not going to beat up on hunters because
I don't think they deserve it and are, on
balance, a positive force for birds but I feel no
such compulsion about the National Rifle
Association (NRA), which I believe is long
overdue for a coup. Snap shots are difficult for
most people (five shots from my father meant five
dead birds instead of one, although some of the
lower rate for "average" hunters is caused by
more than one person shooting at the same bird
and lost dead birds). However, it also means
that the National Rifle Association has failed in
its original and primary objective. I'm not
talking about the grotesque misinterpretation of
the organization's legitimate role in society
that leaves the current leadership advocating
stupidities like having a loaded Glock in the
pocket of your daughter's second grade teacher or
Bushmasters in the gym. That's a recipe for a
lot of extra dead people. The NRA was actually
started (by a former Civil war general, George
Wingate, and a publisher, William Church) as a
way to improve the aim of the average potential
army recruit before a shooting war began by
supporting target shooting and shooting
competitions. The shooting ability exhibited by
Union troops was appalling. To give you one
pertinent quote from general Burnside, who was
the first president of the NRA: "Out of ten
soldiers who are perfect in drill and the manual
of arms, only one knows the purpose of the sights
on his gun or can hit the broad side of a barn."
I sincerely doubt that Burnside or Wingate would
have considered having a bunch of untrained or
haphazardly civilians running around our schools
with Gatling guns or artillery pieces to be a
concept of any merit but that's apparently not
how the modern NRA sees it.
The date: 12/10/2012
The week number: 50
The walk number: 1174
The weather: 73 F, sunny
The walkers: Alan Cummings, Viveca Sapin-Areeda, John Beckett, Vicky Brennan
The birds (10):
Mourning Dove
Anna's Hummingbird
Acorn Woodpecker
American Crow
Black Phoebe
Yellow-rumped Warbler
Ruby-crowned Kinglet
Red-tailed Hawk
Turkey Vulture
Band-tailed Pigeon
--- John Beckett
Respectfully submitted,
Alan Cummings
1/3/13
http://birdwalks.caltech.edu/index.html
Each walk is an intersection of birders, birds,
conditions, and time and this week was no
exception. The conditions I will note below but
I first wanted to point out a basic truism of an
alanless walk. It will typically be longer than
an alanated walk conducted under similar
conditions and, sometimes, much longer. More
time can mean more species simply because more
time means more opportunities. On the other
hand, it's a good thing that Alan isn't out of
town too often because the extra time is little
like playing hooky. It may be pleasant on
occasion but you can't do it all of the time.
Since I work far more hours than I am being paid
for, I'm not terribly concerned for myself but
others are on the clock. Does this cause
problems? Perhaps, but I think there has to be
some latitude on time. If the birding is
stellar, you should be able to take advantage of
it. The mechanism we use in response to a
lackadaisical pace relative to available time is
that you are expected and encouraged to peel off
the walk when you reach your time limit. People
do this every week, even when Alan is on patrol.
So, we had a very slow walk. The first piece of
this walk's puzzle lies in time.
There are numerous numerical measures of an
extraordinary walk. We had 31 species, a sweet
half dozen above the previous record of 25 for
week 49.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
Moreover, there are only a handful of
30+ species days in the history of the Caltech
bird walk. It has happened only nine times,
three from this year, four from 2011, and two
from 2006. None of the previous members of the
exclusive club hail from December. One occurred
in January (last year) but all of the others are
from weeks 9 through 13. Those latter walks make
sense. They are in the Spring migration window
when you would, on the face of it, most expect an
anomalously high species count. You have
permanent residents and a lot of winter residents
who have yet to leave and this provides a
relatively high potential base. Lathered on top,
we see migrants from the south of us heading
north. Still, it's a matter of luck and balance.
In the Fall, the platform provided by summer
residents is much lower, so the potential for a
really high raw species counts is suppressed. We
have records generally in the low to mid twenties
instead of in the high twenties and in the
thirties. In the deep winter, we have the
winter and year-round residents but migrational
movements are local and muted. So, a thirty bird
day in December qualifies as highly unusual.
I tried to establish in the previous paragraph
that thirty bird walks just don't happen in
December. If they are going to happen, they
happen in March. The obvious question may then
be what attracted such an anomalous wealth of
birds and the answer is, I think, fairly simple.
It was a matter of luck, time, and water. We did
not have a particularly steady accumulation of
species. Most of the sightings came from one of
two places, the Maintenance yard, which often
yields a species rich contribution, and back end
of the walk stretching from Avery garden to the
corner of San Pasqual and Holliston, which never
yields more than perhaps one new bird. That was
the luck. We had 24 birds as we hit Holliston
and we were flirting with the record, although we
didn't know it at the time. Usually, you can
reasonably hope to pick up another new species or
two between Holliston and the end of the walk,
which in this case would have put us into record
territory. Seven new species is, however,
unprecedented in my experience and it was this
big anomalous pulse that gave us nearly two extra
standard deviations. It was the difference
between a tie with or, perhaps, a slight
enhancement of the record number of species for
the week, leading to a positive but not stellar
score and something that dismantled the existing
record with a record score. I think the great
score had three root causes, some of which I have
already alluded to. The first cause was hunger.
We had a desultory rain for two days giving way
to partly cloudy conditions just prior to the
walk. We had a lot of hungry birds in the area.
The second cause appeared to be mixed flocks
riding out the rain more or less together. It
brought a lot of those hungry birds into close
proximity and since we were lucky enough to hit
two big dispersal points, it meant a lot of
species. The third cause was in a very slow
walk, which tends to happen when the sheriff is
out of town. Not having Alan certainly doesn't
often lead to new records but, if the conditions
are just right, that extra time can push you over
the top.
Most great walks contain a strong showing of the
birds you should reasonably expect to see with a
sprinkling of less common birds. This week, we
pulled in a number of rare birds. The first bird
that comes to mind is the nuthatch foraging high
on cedar above Holliston. Viveca was hearing
"something", which caused us to pause and then I
saw the bird. I can hear (and vocally id) a
nuthatch if he is relatively close, say within
five or ten meters, which happens more often than
you might think, but this bird was thirty meters
away, at least, a testament to Viveca's ears.
The white-breasted nuthatch was our third of the
year and 2012 now owns one third of all Caltech
bird walk nuthatches. We appear to be the
beneficiaries of a local nuthatch eruption. The
other rare bird we saw was a sparrow in the
Maintenance yard surveying the scene from a twig
on a boxed ficus that had been knocked over so
that the tree effectively formed a bush and
provided, for now, excellent cover for an
enterprising sparrow. The box for the tree had
broken, so instead of moving it over to Darren's
habitat in the parking lot for the gym, it was
left in the Maintenance yard and is, I expect,
not long for this world. This bird was facing
away from us, so at first, we could get no
further than sparrow species. It slowly drops
hints with little head flicks and a raised crest
until, finally, we were able to get a look at the
buff mustache and the side of the bird before he
dropped down and out of sight. We had a
Lincoln's sparrow. As is usual with sightings of
this bird, we had a loner.
For myself, I would have to say that the
highlight came over Avery garden. We had a
juvenile red-tailed hawk being harassed by a
common raven. The raven knew what he was doing
and the hawk, likely the juvenile we have been
seeing in this area over the last month or so,
did not. When first seen, they were heading into
the thermal above Avery, the raven behind and
slightly above the hawk. Both are carrying as
much canvas as they can; each is intent on out
sailing his opponent. The raven wants to drive
the hawk out of his territory. The hawk just
wants to be left alone. Slowly, the hawk begins
to circle within the thermal, gaining height.
The hawk knows that once you are in a thermal, a
crow has to do a lot of work to keep up with you.
Soon, the crow will give way, screaming their
vile curses in your wake. This time it isn't
working. The raven is not a crow. He is silent
and only the occasional flap shows that the hawk
is getting more lift. The raven is working a
little harder than the hawk but he is easily
keeping up. He dives and the hawk is forced to
flip and slash the air with his claws, losing
some altitude in the process. The raven views
this as a successful foray and retreats in good
order to his previous post above and in back of
the hawk. "This isn't working," the hawk thinks.
"He is clearly not a member of that despicable
putrid crow rabble I've been dealing with. This
is more serious and definitely more annoying."
He curls his wings and leaves the thermal,
trading altitude for speed. He is heading
straight for a treetop he sometimes uses for an
observation post. Perhaps, he can sit and wait
this guy out. The raven knows precisely what the
air currents are saying and he knows that the
hawk has not given himself a sufficient margin
for error. He dives at the hawk again, forcing
another back flip, taking the hawk out of his
desired flight path, and causing the hawk to
change his mind. The hawk abandons the tree idea
and works a wide circle back to the thermal. The
two birds spiral a dance. This time the hawk
works well up the thermal and then glides off to
the southwest out of our sight, presumably in
search of a better thermal. His silent black
companion glides with him.
The date: 12/3/2012
The week number: 49
The walk number: 1173
The weather: 65 F, cloudy to partly cloudy
The walkers: John Beckett, Kent Potter, Viveca Sapin-Areeda, Vicky Brennan
The birds (31):
Rock Pigeon
Northern Mockingbird
Mourning Dove
House Finch
Anna's Hummingbird
American Crow
Gull, species
Yellow-rumped Warbler
White-throated Swift
Downy Woodpecker
Dark-eyed Junco
Lesser Goldfinch
Red-whiskered Bulbul
Lincoln's Sparrow
Ruby-crowned Kinglet
Orange-crowned Warbler
Black Phoebe
Turkey Vulture
Red-tailed Hawk
Wren, species
Hummingbird, Selasphorus
Nuttall's Woodpecker
Common Raven
Band-tailed Pigeon
White-breasted Nuthatch
Cedar Waxwing
Mountain Chickadee
Cooper's Hawk
Townsend's Warbler
Bushtit
European Starling
--- John Beckett
Respectfully submitted,
Alan Cummings
1/3/13
http://birdwalks.caltech.edu/index.html