6/25/12
There is a notion in some quarters that numbers
are important. They can be vital but it is easy
to grant them too much credence in a bird walk.
I tend to think of them as cute little morsels
that make for convenient writing but they are not
at the heart of the walk. They are just a
convenience. Nevertheless, I must admit this to
be a walk of great convenience. We had no idea
what the week's record was. If I had been
pressed, I would probably have suggested a number
in the low twenties but week 26 is the beginning
of the summer slump when you have to work for
your birds and adjust to lowered expectations.
Still, one must always keep in mind the temporal
context. The previous record for week 26 was only
17 and, even with our newly minted record of 19,
we won't see 20 species on a single walk again
until week 34, unless we happen to set a
startling new record against the tide. The
record for next week is 18 but then it drops to
15 the following week. So, why bother going on a
walk in July and August. The simple answer is
that numbers aren't everything.
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
This week, we were off to a flying start. We saw
two rock pigeons flying quickly down California
Blvd. from our initial starting place for the
walk. That's two weeks in a row for these guys.
I don't think any of us saw a mockingbird but we
did hear one and it provided an interesting
manifestation of differential hearing prowess.
We are on the driveway between Tournament Park
and Wilson, not far from Morrisroe, when Viveca
suddenly announces that she hears a mockingbird.
Now, none of the rest of us hears anything but
the odd street noise and my pencil, silent to the
song, holds in abeyance until, several paces
later, Melanie hears the unmistakable trilling
repetition of a mockingbird. A couple of steps
later, Vicky hears it, and finally, even I could
I hear it. It would have been interesting to
place Alan in this sequence but he was off on one
of his conference jaunts.
Ravens provided one highlight for the walk. As
we come up to Braun, we see three ravens on the
roof, one adult and two significantly smaller
juveniles (so small, we thought they might be
crows at first glance). The adult leaves the
juveniles at the crest of the roof, hops over to
the edge, leans over, and probes within a crevice
above an end-tile. A couple of seconds later
he/she pulls out a sparrow nestling, hops back up
to the crest of the roof, pummels the unfortunate
sparrow, and then feeds a begging youngster (as
an aside, if you get a chance to see down a
raven's throat and it's red, you have a juvenile
- the throat gets bluer with age). It was
fascinating in a gruesome sort of way.
I would say that red-masked parakeets made the
bird of the week. This was a classic example of
visual pattern recognition. The parakeets were
quiet and hanging out in a street tree next to
Morrisroe. Each of us walks under them until
Viveca stops short and, realizing that there is a
bird to be had, announces that she has some
parrots or parakeets. These soon became
red-masked parakeets but they left me with a
nagging question, which is the actual highlight.
Why are parakeets green? Birds aren't plants, so
there is no chorophyl game to parlay into green.
Is it some sort of pigment? Are these birds
playing light scattering experiments for our
benefit?
The starting point for bird colors is in pigment.
These are like paint, absorbing some wavelengths
of light and reflecting others (the ones you
see). They are mostly melanins (black to brown)
and carotenoids of various types, which are used
to make those over the top reds and yellows. Now,
turacos, which are from sub-Saharan Africa, do
use green pigments to generate a green color
(google "livingstone's turaco images" for a look)
but the vast majority of greens in the avian
world are not caused by the use of a green
pigment. So, I address this in a round about way
that begins with a riddle: What can you do with
a blue feather from a scrub jay, a green feather
from a parrot (or parakeet), a bottle of rubbing
alcohol, and a ten year old with a hammer? I did
not have a ten year old handy but I did have blue
and green feathers and alcohol (ideally, you
would have a red and/or a flamboyantly yellow
feather, too but I didn't have one). I filled an
egg cup with the alcohol and slid each feather
into the cup so that about half of the feather
was soaking and the other half dry. I checked
after an hour and the scrub jay feather had
become a dull brown where it had been soaked in
alcohol. The green of the parrot feather was
still there but a lot of brown was showing and
the remaining green was more of a yellowish olive
green than the bright green it started with.
After several hours, the parrot feather was still
showing hints of yellowish green near the edges
but the bulk of what had started out as a solid
green was now a solid brown. I declare victory.
I have succeeded in changing the color of a
feather. I didn't try a red feather because I
didn't have one but I will assert that this
exercise would not have impacted the red color,
except, perhaps to brighten it up a bit because
you are cleaning off some dust. So, what have
we learned? Alcohol takes out the blues and
bright greens, leaving brown to a yellowish
olivine green. I will assert without proof that
a bright yellow or red feather would have ignored
the alcohol. Now, take the feather out and let
the alcohol evaporate. Soon, the blue is back.
The green is back. The red, if you have it,
stays put. We have a reversal. Now, we are
ready for your ten year-old with the hammer. Let
him/her hammer half of the scrub jay feather.
The blue will go away and nothing you can do will
put humpty dumpty back together again. I confess
that I didn't try this since I didn't want to
sacrifice my only scrub jay feather. Besides, I
didn't have the critical ten-year old. So what
happened?
We have to start with the blue. The basic
coloring agent for any bird feather is melanin,
which gives you a dark undertone that leads to
browns and blacks if nothing else is done. For
scrub jays, the feather barbs contain an outer
colorless layer, which is underlain by a suite of
cells that have air pockets ranging anywhere from
30 to 300 nanometers across, below which you have
a dark layer. The key here is that the air
pockets are really tiny, less than the wavelength
of visible light, which is between 400 (violet)
and 750 (red) nanometers. Tiny air pockets can
scatter light and, if the dark layer underneath
absorbs everything except the light that was
scattered, you end up with a blue. If you fill
up the air pockets with alcohol, you no longer
have scattering because the air pockets are no
longer operative and you see just the dark layer
underneath, which absorbs most colors. Since,
the alcohol masked but did not destroy the
scattering entities, the blue comes back as soon
as the alcohol leaves. On the other hand, if
your ten-year old smashed those air pockets with
his hammer, the scattering centers were destroyed
and the blue will go away. Now, what I just gave
you is what you might call the standard model for
blue feathers. Recently, there has been work
suggesting that scattering can't be the whole
answer because a basic prediction you get
relating intensity of scattering and wavelength
of the incident light is not being met. You
should look up papers by Prum and coworkers if
you'd like to pursue it. According to Prum and
friends, the blues are instead caused by another
color generating phenomenon referred to as
interference, which would work if a set of
uniformly spaced, uniformly sized air pockets
were present. This proposition seems to have
taken the avian research world by storm but, as
Kurt Nassau in his book "Physics and Chemistry of
Color" says, "One does wonder why these blues are
not iridescent" (I'll let you look that term up).
There's something not quite right with Prum's
model but, there is also something wrong with the
standard scattering explanation, so I don't think
we have a definitive answer, yet. Ok. Let's
accept that the blue color of a jay's feather is
caused by an interaction between scattering (or
interference) of air pockets and absorption by
the dark layer. What about the green feather of
a parakeet? Here, we add one more wrinkle and
place a layer above the dark layer that contains
a yellow pigment. The yellow pigment absorbs
most wavelengths of light but it reflects yellow.
Mix yellow with blue and, voila! We have green!
We have our parakeet!
The date: 6/25/2012
The week number: 26
The walk number: 1149
The weather: 79 F, full sun
The walkers: John Beckett, Melanie Channon, Vicky Brennan, Viveca Sapin-Areeda
The birds (19):
Rock pigeon
Northern Mockingbird
House Sparrow
Mourning Dove
House Finch
American Crow
European starling
Black Phoebe
Cooper's Hawk
Spotted Towhee
Swift, species
Nuttall's Woodpecker
Red-whiskered Bulbul
Hummingbird, Selasphorus
Lesser Goldfinch
Red-masked Parakeet
Bushtit
Common Raven
Northern Rough-winged Swallow
--- John Beckett
Respectfully submitted,
Alan Cummings
7/5/12
http://birdwalks.caltech.edu/index.html
6/18/12
Beginnings can be endings. On my way to the
starting point for the walk, I generally pause on
the walkway above the Throop ponds and glance
down to see if a mallard is in residence. This
time, Melanie happens to accompany me and we get
the mallard but she then hears a bird whose song
she doesn't recognize. I am, of course
suspicious. Melanie has great ears and I know
who it is that sings here in the morning and in
the afternoon. I can not hear him unless he is
quite close (I have heard him a couple of times)
but I still know him well. I am a bit torn
between chasing down a lead and leaving but I
know the reality is that I have to ignore
Melanie's bird. In Alan's absence, I am
"leading" the walk, by which I mean I carry the
scepters of office, Alan's bird listing pad, a
Sibley and keys to the Maintenance yard. So, we
reluctantly turn away from the ponds and head
towards the starting point on the other side of
California. Luck is with us, however. Near
Millikan's head, we run into Vicky and find that
she has also been hearing something lyrical.
Well, now, we really need to get to the bottom of
this. Vicky offers to go warn Viveca, who we
could see, and anyone else who happened to be
waiting that the keys and I will be a couple of
minutes late. Melanie and I head back to the
ponds. I suggest that she dial up a common
yellowthroat on her phone and, upon listening to
it, she says "That's it!" Now, for a visual. We
see a bird out of the corners of our eyes pop
into the camellias next to Guggenheim but the
look is very bad. However, I see him pop out and
briefly skirt by an agapanthus. Melanie misses
him but, between her aural and my visual, we have
a very solid id and the inversion of a bird that
often ends the walk. We begin. In the end, we
had 23 species to keep the common yellowthroat
company for a total of 24 species, a new record
for week 25, eclipsing the previous record of 21
with nothing but net.
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
Desert gods are the hardest. They howl into a
hot wind and come closest only in the emptiness
of something vast, whether it be a crease of your
mind or buried in the hollows of a shifting dune.
These are gods of different names. They hover
over sacred places and, even dead, they leave the
harshest shards. That's what I felt as we came
into the Maintenance yard. We were standing
before the house of an old god. In 2002, a set
of Caltech walkers, including Alan, stood in this
place, held in the vision of the only owl to ever
be reported on the Caltech bird walk. Now, we
are in the nave and stand before a few rude
pipes, broken from the hollowed bones of Amiens.
Owl tree is a shattered dream. It lost a central
trunk in the great wind storm but there were
still twin towers spiraled in green. In a few
years, they would have covered the gap but, this
week, we are confronted by a ten foot stump.
There is no green and there is no owl tree.
The Maintenance yard was a challenge because the
little wheel loader was active and noisy but we
still picked up a spotted towhee and a Bewick's
wren (another excellent use of Melanie's phone)
by sound. I can also report an active collection
of common orb weavers in Alan's jungle. Alan has
a sense of pace that is faster than mine and,
when he is absent, the walk tends to be a little
slower. This was no exception. We were slow, so
slow that we barely made it out of Tournament
Park before Vicky had to leave (Vicky is on a
timer). It was also a luxuriating walk and that,
I think, contributed to our extravagant species
total. We think we may be hearing a house wren
from the back end of Tournament Park but we
aren't sure. If you are in a hurry, you move on
or send out a scouting party. Instead, we all
turn back to check it out. A hundred feet closer
and it is an unchallenged, unmistakable, clarion
song, even to me. House wren.
There were black phoebes everywhere. Upon
fledging, the male takes the juveniles out for
on-the-job training for a few days and you will
often see several of these birds together at this
time of year. Only one of them will be competent.
Dad flies over to the thin shaft of a weed.
Normally, he wouldn't use this because there are
better perches nearby but it is important to show
what is possible. He lands perfectly. The stalk
is motionless. He stays for a few seconds to
demonstrate that this is a viable observation
perch and then flies over to a tree. Each of his
children gives it a try and fails miserably, the
stalk whipping each time in a flurry of wings.
But they now know that it can be done and, in a
month or two, each of the survivors will be able
to
pull off a similar maneuver, flawlessly. The
school moves on to more solid perches and
concentrates on flying insects.
The black-chinned hummingbird was still pretty on
her nest but I'm pretty sure that I would get
general agreement that she was not the most
intriguing sighting of the day. We come up to the
corner of California and Wilson and Viveca sees
what she initially thinks are band-tailed pigeons
but, wonder of wonders, we actually have a pair
of rock pigeons perched on a light stanchion. We
last saw a rock pigeon in February and we now
have three sightings for the year, half of number
we had by this time last year and a pale shadow
of the 20+ sightings buy week 25 that would have
been typical of the 90s. We also picked up a
band-tailed pigeon later in the walk, presenting
us with our first triple dove/pigeon day since
last November. Things must be looking up if we
are seeing rock pigeons.
I must, of course, mention Melanie's new life
bird. On Wilson, there is a small group of
northern rough wing swallows that tends to hang
out near the solar panels on the Wilson Parking
structure during the early part of the summer. I
assume they are nesting somewhere in the rafters
but I've never tried to track down exactly where.
This time, they are foraging over the field in
front of Beckman, giving a nice demonstration of
swallow flying technique, and giving Melanie her
92nd bird. A hundred birds is a key marker in
the life of a birder. Provided you can
confidently identify a decent fraction of those
species, it indicates that you are beginning to
have a mastery of the common to less common
members of your local avian population and you
are serious enough to be looking for further
mastery. It is an easing from the duffer world.
As for Melanie, I expect that the first hundred
will not be the last.
The date: 6/18/2012
The week number: 25
The walk number: 1148
The weather: 77°F, hazy sun
The walkers: John Beckett, Melanie Channon, Vicky Brennan, Viveca Sapin-Areeda
The birds (24):
House Sparrow
Mourning Dove
House Finch
Anna's Hummingbird
American Crow
White-throated Swift
Black Phoebe
Mallard
Common Yellowthroat
Common Raven
Hummingbird, Selaphorus
Bewick's Wren
Spotted Towhee
Red-whiskered Bulbul
House Wren
Nuttall's Woodpecker
Bushtit
Lesser Goldfinch
Cooper's Hawk
Rock Pigeon
Northern Rough-winged Swallow
Yellow-chevroned Parakeet
Band-tailed Pigeon
Black-chinned Hummingbird
--- John Beckett
Respectfully submitted,
Alan Cummings
6/29/12
http://birdwalks.caltech.edu/index.html
6/11/12
The walk has a sensibility about it and a seeming memory as if there were souls drifting through
time. They are running on the tide; even former Is are running on the tide and when we flow
through a narrowing tree, I catch glimpses in the corner of my eye. We see a Cassin's vireo in an
oak on Wilson but a bushtit now hops into double exposure, Vicky's call. He has a moth in his
beak, still squirming for purchase. Both are all calling. Both are gone. All three are here even
though at least one of them is dead.
This was a walk of almost. We came in with a final total of 20 species, thanks to a couple of
white-throated swifts swirling around the library at the end of the walk. They left us just below
the current record of 21 for week 24; we would have had a tie but for our common yellowthroat
developing a sudden case of shy retirement. He has been a quite reliable responder to Alan's app
but not this week.
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
We had no unexpected or excessively rare birds for this time of year, unless
you want to count our nesting black-chinned hummingbird just on general principle but we did
very well with those birds we could reasonably expect, except for raptors. A cloudless sunny
day did not translate into any hawks and, given that our best hawk spotter, Viveca, was on the
walk, I take that to mean there weren't any up there for us to see. We saw no turkey vultures,
even though we have been seeing them lately and, at least so far, we have no summer Cooper's
hawks to report. The red-shouldered hawks who were courting over Tournament Park earlier this
Spring, apparently decided to nest elsewhere. Maybe that's one of the reasons we have been
doing so well with preyable birds.
Other than our seeing that bushtit with a moth across the street from Morrisroe, which I alluded
to above, I would say the unexpected highlight was to be found in the Maintenance yard. Both
Vicky and Viveca are hearing something nebulous in the corner oak next to where the cargo
containers used to be (it looks like the Childcare center is really going to be happening). It was a
curious sound and repetitious enough to draw all of us (I by hearsay). Eventually, we notice two
birds and, finally, Alan catches enough of a visual to call a pair of orange-crowned warblers.
One of them was a recently fledged juvenile begging (complete with wing shiver) and the other
an adult. This seems pretty clear evidence that we have a resident breeding population of orange-
crowned warblers around the Maintenance yard (i.e., not all of the southern California wintering
orange-crowned warblers end up going to Alaska). Technically, orange-crowned warblers are
resident in LA county but our usual summer orange-crowned warblers are from the Channel
Islands and post-breeding, so there is little if any singing for them and no sex. We (mostly
Darren) have been hearing a lot of singing over the last month. Perhaps, this is the beginning of a
year-round residency encompassing the campus.
The male common yellowthroat is always a highlight when we see him but he wasn't in a social
mood this time and we missed the pleasure. There was, however, an expected highlight as we
came up to the agapanthus patch outside the Central Engineering building. We see the black-
chinned hummingbird nest but it isn't occupied. This could be depressing. What happened? Did
we have a failed brood? The answer, with a little patience, buzzes over to a branch in the
sunlight by the wall. She perches there for a minute or so, providing an excellent view (you
could see the flecks on her throat) and, then, it was one of those highlight moments. She
stretches out one of her wings. She is showing mauve to the passing sun and creating an
enthralling sense of beauty. Finally, duty calls. She pops over to an agapanthus blossom for a sip
and then flies over to her nest where she settles in. Mom is back. Generally, you can expect a
female black-chinned to spend about a quarter of her time off nest during incubation, so our
finding her missing on our arrival was not out of the ordinary. Once the eggs (almost always
two) hatch, she will drop nest sitting down to half or less of her time, and then give it up entirely
about nine days after hatching. If we want a continuous collection of black-chinned
hummingbird sightings for the next few weeks, we will need to exercise ever greater degrees of
patience until the nestlings are big enough to poke the odd beak up above the rim of the nest.
If you look at a histogram of black-chinned hummingbird sightings on the Caltech walk, you can
talk yourself into three peaks. The first, between weeks 15 and 20 is a skewed distribution
falling off sharply from a peak at week 19. This likely reflects the Spring migration, with males
generally making up the earlier sightings (they go first to establish territories) and the females for
a given breeding area passing by a week or so after the males. There is a mostly broad central
peak of sightings between weeks 22 and 27 that is likely composed of late migrators and locally
breeding females. For the females who stay, it's two weeks of incubation, three weeks of
nestlings in and on the nest and another week or so of fledglings hanging out in the general
vicinity of the nest, still being fed periodically be their mother. We've had three years (2007,
2008, and 2012) in which we apparently or demonstrably had a locally breeding female whose
territory intersected the path of our walk. A third regime of sightings has a sharp peak centered
on week 31 (early/mid-August) with scattered sightings extending well into September. This is
associated with the Fall migration. Males again lead the way and females and juveniles take
their own good time, as they should.
Alan won't be able to make it for the next couple of weeks due to dueling conferences and, since
Alan runs the web site, you can expect some delays in posting although all reports will make it up
eventually. So, if you've been dancing around the edges of thinking about perhaps maybe trying
a walk, this would be a good time to transform a nascent fantasy into reality. We could use the
company.
I decided a long time ago not to pursue creative writing because I didn't think I had a talent for
writing fiction and I didn't want to be a journalist (it didn't occur to me at the time that one
might be able to make a living writing nonfiction). Nevertheless, I am planning a foray into the
world of investigative journalism. A coming bird of the week is likely to be from outside the city
limits of Pasadena based on interviewing a primary source (fair warning, Alan!). I know the core
of some internet sites to be composed of little more than travelogues from members' out of area
experiences with the remaining dribbles essentially consisting of a calendar of future local birding
walks. It is as if there were an insecurity in what they can see with a short drive or walk and a
comfort in what you can not see. To me, off walk walks are condiments. They can spice up a
meal but they should be left to the odd child's albatross. The main course should be every bird.
Every bird, no matter how apparently mundane, holds an interesting story and, if you watch and
listen, the bird will tell you what it is. The story will be a different one tomorrow.
The date: 6/11/2012
The week number: 24
The walk number: 1147
The weather: 76F, sunny
The walkers: Alan Cummings, Viveca Sapin-Areeda, John Beckett, Vicky Brennan
The birds (20):
Northern Mockingbird
House Sparrow
Mourning Dove
House Finch
Anna's Hummingbird
American Crow
Common Raven
European Starling
Mallard
Lesser Goldfinch
Black Phoebe
Spotted Towhee
Orange-crowned Warbler
Nuttall's Woodpecker
House Wren
Hummingbird, Selasphorus
Bushtit
Red-masked Parakeet
Black-chinned Hummingbird
White-throated Swift
--- John Beckett
Respectfully submitted,
Alan Cummings
6/15/12
http://birdwalks.caltech.edu/index.html
6/4/12
We were off to an excellent start. Kent comes in
with a duck and, then, Darren and Kent disappear
for a while but return with an orange-crowned
warbler. The Maintenance yard yields a couple of
good looks at some red-masked parakeets, a very
quick look at a couple northern rough-winged
swallows, which is a fairly rare bird for us
(only 15 sightings all time, so far, although
most of the somewhat more common "swallow
species" are likely to have been northern
rough-wings). Even better, we also seemed to be
nailing almost all of the not always common
common residents with the notable exception of
acorn woodpeckers. As is often the case when
times are good, however, a gray seam appears like
a clumsy foot stumbling over an unseen stone. We
have 16 species as we are about to enter
Tournament Park and Alan bursts out with a bald
faced assertion that we were "heading for a
record", the current record for the week being a
mere 19. I smelled a bad case of hubris and felt
like somebody on my baseball team had just walked
over to a pitcher throwing a no-hitter into the
eighth inning and tried to talk to him. This
just isn't done. The walk was now jinxed and we
were going to be lucky if we picked up another
two species and those just as a tease. My fears
were confirmed. Tournament Park was not
initially productive and it looked like we might
be doing a walk for the walk and not for the
numbers. "So," you might reasonably ask, "how
did we do in the end? ok?" Yes. "Better than
ok?" Yes. I think I can agree with that we ended
up doing better than ok and that my fears of a
jinx were, in the end, overblown. "Much better
than ok?" Certainly. "Extraordinarily beyond
ok?" Yes. "Arguably, the best walk of all
time?" Absolutely! We took home 27 species, a
full third beyond the previous record of 19 and
nearly double the median of 14. Congratulations
all around!
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
Now, some of you may be jaded by memories of 30+
species walks in the Spring and know that the
all-time record number of species on a walk is
37, ten species beyond what we saw this week.
So, how is it that I can claim greatness in the
thralldom of those kinds of numbers? The answer
lies in context. A great walk can be the memory
of a single glance or a singular species but what
makes a walk extraordinary in terms of sheer
numbers of species is how it stacks up against
the results of its peers, those walks conducted
in the same week in other years. Alan computes a
score for each walk defined by the number of
standard deviations that a species total lies
above the mean for all walks conducted during
that same week since 1986, when Alan started the
Caltech bird walk. I'm sure that some
comprehensive larded gobbeldygook statistical
analysis could be concocted that would be
"better" but it wouldn't be. Alan's metric
captures the flavor of greatness in a very simple
way. What's the record score? It's 3.233, which
you will perhaps not be surprised to learn, was
the week 13 bird walk from last year that still
holds the record for total number of species
(37). And how did we do this week? Compute the
score and you get 3.332. We have a new champion.
This was the highest scoring Caltech bird walk,
EVER!
In spite of all the accolades I described above,
deserved though they be, you can feel migration
in its presence and in its absence. We have
favored species, like kinglets and yellow-rumped
warblers, that won't be seen again until the Fall
and others we will be lucky to see but, if we do,
it will be on migration. These birds have
passed us by and are breeding to the north or in
the desert, or up in the mountains. They are
somewhere else. It is important, however, not to
forget that we have our own collection of
permanent residents and summer visitors and they
are very busy. This is breeding season and you
see it in courtship and nesting. You see it in
territorial disputes and begging juveniles. This
week, we spent several minutes staring at the
Nuttall's nesting hole south of the driveway
connecting Tournament Park to Wilson. A couple
of weeks ago, we saw both adults pop into this
hole but this time we didn't luck into any
visitations (it would have given us 28 species
for the walk and an even higher score but c'est
la vie). We also saw a bushtit nest in an oak
along Wilson (the northernmost mature oak south
of California if you are interested in checking
it out). We had seen this nest previously but
it's a very good example worthy of a second look,
independent of any activity that may or may not
be going on inside. Bushtits have tube shaped
nests constructed from spider web and other
flotsam, so that the lining is whitish. In my
experience, they are usually lined in the
interior with feathers on the bottom (plugging
any holes with insulation), and decorated on the
outside with debris from the host tree or bush.
We didn't see any activity in the host tree,
although bushtits were scattered all along
Wilson, so maybe the parents were out foraging,
or, perhaps, the young have already fledged.
We saw a third nest on Wilson at the top of
Braun. This wasn't as visually compelling as the
bushtit nest because the house sparrow nest is
tucked out of sight in the crevice formed by a
gap in one of the roof tiles but, now that we
know where it is, we may find this species a
somewhat easier capture for the next few weeks.
We encountered a fourth nest on Avery. This one
consisted of adobe braced against a pipe near the
feeder above the driveway. Black phoebes have
been reliable residents near Avery for the last
couple of years, so it was pretty clear that we
had at least a pair of them actively nesting in
the immediate vicinity. This year we know where
to look. The female is, as of Thursday, still
actively incubating her eggs (female black
phoebes do all of the incubating but the male is
a very active partner and keeps her well fed).
The nest is quite close to a door, which tells
you just how tolerant of human activity these
birds are. At some point, black phoebes must
have concluded that people were not black phoebe
predators, whether adult or juvenile, but that
they often provided good to excellent building
sites. The rest is a pleasant history. I always
find looking at occupied black phoebe nests to be
a cheery interlude but we were, as the tale
turns, not nested out. Our final and, I think,
our best nest of the day was sighted on Holliston
near the Central Engineering building. We see a
female black-chinned hummingbird on a branch.
Her long lithe body is the first thing you
notice, then the lack of a vestigial throat
patch, and the straight bill. We followed her
flitting around, thinking that we had just
acquired an excellent capture for so late in the
walk and so late in the migration. However, she
suddenly buzzes over to an interlocking set of
leaves and settles into a small amber cone
nestled between a pair of twigs. We have a
black-chinned hummingbird nesting on campus! The
male is long gone and our female will be handling
all aspects of incubation, feeding, fledging, and
preparation of her young for life. Most
black-chins migrate past us heading north but a
small fraction of the population nests in the San
Gabriel Valley and, very occasionally, one will
nest on or near campus, leading to a lot of
sightings. 2007 and 2008, each with 10
black-chinned hummingbird sightings (seven
sightings in eight weeks in 2007 and six in seven
weeks in 2008), are the only years that we
probably had a nesting bird. Excluding those
anomalies leads to an average of one sighting a
year since 1986 but, if our Holliston
black-chinned succeeds, we are about to have a
third most excellent black-chinned hummingbird
year. Besides, she is seriously cute.
I suppose that I must propose a bird of the week.
An easy case could be made for the black-chinned
hummingbird. I think I will, however, opt for a
couple of specks east of the Maintenance yard
sighted by Viveca and heading at a very rapid
clip to the west. By the time I got a glass on
them, they were specks in the west and I could
not have done better than the well-known "swallow
species," although I would have argued against a
bank swallow based on the fairly deliberate
flight pattern. Darren, who was more attuned to
Viveca's speck alerts, was able to get a much
better look and his look gave us a legitimate
northern rough-winged swallow. These birds have
not been well studied (in case you are wondering,
southern rough-winged swallows don't get any
further north than Panama and were not an
officially separate species until 1983) and I
suspect, but I can not prove, a composting of
intellectual laziness and misplaced aesthetic
sensibility. Tree, cliff, and barn swallows are
prettier. Bank swallows, which are fairly well
studied, like to nest and roost communally.
Decide to study a few hundred breeding pairs of
bank swallows and you may only have to find one
colony. Decide to study a comparable number of
northern rough-winged swallows and you will have
to work a lot harder, although you will often
have a few northern rough-winged swallows near
the outskirts of a bank swallow colony,
presumably because bank swallows actually dig
their own burrows but don't use all of them.
Northern rough-winged swallows are opportunists
when it comes to nesting sites with holes in
banks, crevices in cliffs, drainage pipes under
overpasses or bridges, all providing acceptable
sites (i.e., I'm not going to build my own burrow
but I'm pretty flexible about the hole someone
may have dug for me). Roosting sites may or may
not be communal. This is not a case of not
liking any neighbors; you will sometimes find
northern rough-winged swallows mixed in with bank
swallows and not infrequently near other northern
rough-winged swallows, especially during
migration. It's just that northern rough-winged
swallows don't specifically seek out a crowd.
That's my kind of society. For us, northern
rough-winged swallows are strictly breeding birds
of the summer, although that appears to changing
(as the decades go), as they are expanding their
wintering range northward. Most of them still
winter in Central America but you can already see
them reliably in winter near the Mexican border.
We may be up next.
The date: 6/4/2012
The week number: 23
The walk number: 1146
The weather: 70°F, cloudy
The walkers: Alan Cummings, Kent Potter, Viveca
Sapin-Areeda, John Beckett, Darren Dowell, Vicky
Brennan
The birds (27):
Scrub Jay
Northern Mockingbird
House Sparrow
Mourning Dove
House Finch
Anna's Hummingbird
American Crow
Mallard
Common Raven
Lesser Goldfinch
Black Phoebe
Orange-crowned Warbler
Red-masked Parakeet
Spotted Towhee
Northern Rough-winged Swallow
European Starling
House Wren
Band-tailed Pigeon
Bewick's Wren
Bushtit
White-throated Swift
Yellow-chevroned Parakeet
Hummingbird, Selaphorus
Turkey Vulture
Black-chinned Hummingbird
Common Yellowthroat
Red-whiskered Bulbul
--- John Beckett
Respectfully submitted,
Alan Cummings
6/8/12
http://birdwalks.caltech.edu/index.html