8/29/11 (revised)
We picked up 16 species under difficult
conditions (temperatures in the low nineties,
moderately humid, and no cloud cover) and
acquired an excellent highlight bird. Our
species total was well below the week 35 record
high of 21 but safely above the median of 12 and
way above the record low of 7.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
It looked like it was might be a tough sell and a
light crowd. The temperature promised to be in
the mid-nineties by the time the walk was over
and two of our three regulars were going to be
absent. Alan was on a well-deserved vacation and
Vivica was busy hopping airports with her
husband, who is a private pilot. He gets to fly
to interesting places and she gets to hunt for a
pileated woodpecker. It sounds like a great
relationship to me. Melanie, who has been making
a fair number of walks, of late, was also out of
town. If all of the occasional walkers were also
on vacation or decided that a nice
air-conditioned lunch inside was better than a
hot walk outside, I could be doing the walk by
myself. So, I put on my best cajoling outfit
and talked George Rossman into coming or, rather,
he was kind enough to allow himself to be talked
into coming. We got a nice view of a red-tail
from California Blvd. as we were waiting but we
weren't joined by anybody else and launched off
into the walk at noon. Darren caught up with us
a couple of minutes later as we stood at the
corner of the tennis court trying to decide
whether or not a call George had heard was a
lesser goldfinch. I couldn't hear it (ergo, not
a starling but not necessarily a goldfinch) but
George's description sounded just like a Vivica
lesser goldfinch rendition, although not nearly
as animated. I was mulling over whether or not
this should count as a species (we had no visual,
George was a little uncertain on the call and,
given that he knows lesser goldfinch calls quite
well, that meant that I also needed to be
uncertain), when Darren walks up and asks if we
had heard the lesser. I took that as a
confirmation for species number two and off we
went, now the three musketeers. The Maintenance
yard didn't yield a lot but I can tell you that's
where I feel Alan's absence most profoundly
because, if he's not there, I am usually on
spider flushing duty and, although I have yet to
swallow one, I did get a mouthful of webbing once
(tripped) and I also encountered a spider
crawling down my ear trying to get away from me
(I get shivers just typing that one in;
fortunately both of us survived). The species
count started picking up in Tournament Park,
including the bird of the day, which I describe
below. We failed to get any acorn woodpeckers on
Wilson, as is often the case when it is hot and
cloudless. Acorn woodpeckers usually have a
favored hang out for hot sunny weather that is
sometimes visually accessible but we don't know
where that is yet. We were at 13 species but
late acquisitions of yellow chevron-winged
parakeets and bushtits put us up to 15.
The highlight of the day was in the Tournament
Park parking lot. Darren and George were working
on a Nuttall's when Darren suddenly announces
that we had a chickadee. My response to this
was, "You're kidding!" However, Darren
immediately responded with "No, I'm not," and
indeed he was not. I saw a pasty little bird
from the side in the upper canopy of a tree and
George got a solid visual from the front. Darren
whips a camera out of his knapsack, hoping to get
a photo, but he wasn't fast enough. Our bird,
having spent several minutes with us, decided
that he had finished the local cuisine. He pops
through two trees in rapid succession and leaves
our field of view before Darren can get a shot
off.
My surprise over getting a mountain chickadee
reflects the rarity of sightings for this species
on Caltech bird walks (this is a 1% kind of
occurrence for us). We have only nine previous
sightings of mountain chickadees, none in week 35
(four were in weeks 8-10 and four in weeks 39-44)
and we haven't seen a chickadee since 2007.
Mountain chickadees are common at higher
elevations in the San Gabriels but, during August,
especially if the coniferous seed crop is poor,
juveniles often drop to lower elevations as they
disperse from their natal territories. It is
likely that our bird was in an egg a couple
months ago and, if he is very lucky, he will back
up the mountain, strong enough to carve out his
own territory sometime next winter. It's not
clear exactly where this territory might be
beyond saying that it won't be in or near his
natal territory. He will be finding a life-long
mate, although chickadees are willing to "trade
up" on occasion by dropping their current mate in
favor of an older bird who lost his or her mate.
We can also be confident that he will be staying
in southern California because our mountain
chickadees are part of an isolated population
that hasn't talked to anybody from Arizona or New
Mexico in about a million years. I don't expect
that our bird will be breaking with this
tradition.
The date: 8/29/11
The week number: 35
The walk number: 1106
The weather: 91°F, full sun
The walkers: John Beckett, George Rossman, Darren Dowell
The birds (16):
House Sparrow
Mourning Dove
House Finch
Anna's Hummingbird
Crow
Red-tailed Hawk
Lesser Goldfinch
Red-whiskered Bulbul
Red-masked Parakeet
House Wren
Nuttall's Woodpecker
Hummingbird, Selasphorus
Mountain Chickadee
Black Phoebe
Yellow-chevroned Parakeet
Bushtit
--- John Beckett
Respectfully submitted,
Alan Cummings
9/9/11
http://birdwalks.caltech.edu/index.html
Editor's note: total was 16 not 15 as originally reported.
8/22/11
The beginning was inauspicious. We had a grand
total of one pre-walk species scattered among
five walkers. Typically, we get three or four
pre-walk species this way and, although all of
these birds are usually seen again during the
walk, only a few fond memories have flowed from
such anemic state of sourcing. Darren and
Melanie picked up a black phoebe vocalization by
the tennis courts but our species total had not
improved markedly by the time we left the
Maintenance yard. All of us were hoping to make
up some ground in Tournament Park but, as we
exited the Maintenance yard, we were greeted by a
backhoe tearing up asphalt and generally making a
noisy nuisance of itself. Even worse, all
possible routes to the park were being guarded by
a suspicious orange coated supervisor who was, I
am sure, not looking upon us with any great
favor. So, we dawdle over the playing field and
think ourselves fortunate when the construction
crew suddenly breaks for lunch. Weren't we
lucky!? We pass them by to make the gate to
Tournament Park, feeling the faint echoes of
people who have just escaped a terrible fate, but
were soon frustrated by an entry frozen with a
heavy chain. Gandalf didn't make the walk and
neither of Alan's master keys could master the
lock. Nor was there any appetite for climbing a
ten-foot chain link fence, even if it hadn't
meant giving a cluster of interested four year
olds a really bad idea, and that left us with
just two options. We could skip the most
species-rich segment of the walk or take a detour
around the gyms and swimming pool and approach
the park from the back end. We chose the latter
and we chose well. The species list shot up with
a yellow-chevron-winged parakeet, red-whiskered
bulbul, yet another summer orange-crowned
warbler, a western tanager, and a Nuttall's
woodpecker among others. Both the tanager and
the Nuttall's were new lifers for Melanie. We
supplemented the harvest with acorn woodpeckers
and house sparrows on Wilson and, upon seeing a
few bushtits by the ticket office, we found
ourselves holding a new record high for week 34
with 18 species, two above the previous mark.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
The record high of 14 for week 33, which we
failed to breach last week, is beginning to look
like the bottom of a ravine.
There were a number of highlights. The Nuttall's
always seemed to be on the wrong side of the tree
(for us, anyways), but by posting birders on both
sides, we all obtained some very good looks. I
think our bird may have been a little frustrated
because he shuddered in front of me and let off a
series of sharp chirps that even I could hear.
Also, towards the end of the walk, we were graced
by a juvenile male lesser goldfinch molting into
adult plumage, his soon to be solid black crown
still shredded with numerous flecks of green. He
was having a good time on the lawn adjacent to
San Pasqual, straining dandelion seeds and
ignoring the birders just a few feet away.
Although not part of a bird story, we also saw a
bee hive smothered in bees; a swarm was about to
take off.
I've described above some of the pleasant
interludes deserving of mention for our walk but
the western tanager has a special place. This
bird was near Morrisroe and yielded identity
slowly but surely, a yellow bird of robin size,
pinkish beak (i.e., light colored), clearly
marked wing bars, and more patience in gleaning
than you would have expected from a typical
oriole (I didn't get an angle on the tail but I'm
sure it was notched). There was no vocalization.
We either had a juvenile western tanager or an
adult female. I suspect an adult because we are
at the leading edge of the Fall migration rather
than the back end where juveniles are more common
but it could have been either. Western tanagers
are relatively rare for us. We average about one
sighting a year but the captures are very spotty.
Prior to this January, we hadn't even seen a
tanager on the walk in over five years. This
year, we already have four sightings, the most
ever for a calendar year, and we have an
opportunity for more because the Fall migration
is just beginning. The vast majority of western
tanagers winter in southern Mexico or Central
America, although a few winter on the west coast,
which accounts for our occasional winter
sighting. In the Spring, usually sometime during
weeks 17-20, western tanagers pass through
Pasadena on their way to breeding grounds mostly
well to our north, and, in the Fall, we get the
southward migration with sightings most commonly
occurring in weeks 39-41. This year, we have two
sightings in successive weeks in January
(probably the same bird), a little odd but not
extraordinary, a sighting in week 13, about a
month before normal, and now a sighting in week
34, about a month before normal. We've been
having a very strange abundant year for tanagers.
Perhaps the oddest thing about western tanagers
is a general lack of information. Sure, there's
been some attention paid to tanager nesting
habits and those brilliant orangey-red feathers
on the adult males and their origin
(rhodoxanthin). We think perhaps we possibly
maybe might know that juveniles tend to hang out
for a while at intermediate places during
migration to molt because this reduces drag and
hence energy costs, but we know next to nothing
about what these birds do in Mexico or how the
population responds to different environmental
stimuli of which we provide plenty. You would
think that an insectivore that doesn't turn her
beak up at berries or even seeds, that likes the
margins between light and dense canopies (think
clear cutting, fires, and transitional
urbanization), and is vulnerable to cowbird
parasitism would attract a lot of serious
scientific attention for the potential insight
into the implications of habitat modification.
The population dynamics are, however, rather
poorly understood. I don't know if this speaks
to fad or is just a curious oversight.
With some birds, we can't avoid an interaction.
The observation or its attempt influences
behavior, as we found with the Nuttall's, and
this can be bad for a bird if too much energy is
consumed or we incite the attention of a real
predator. Some birds seem oblivious or aware but
uncaring. Our lesser goldfinch is in one of
these classes although it would perhaps have been
better were he not. Similarly, we generally have
no meaningful communion with a soaring bird
because he is far away and neither of us is on
the other's menu. For tanagers, who often forage
fairly high in the canopy, we are like a mist of
the bird's breath. This is only one bird that
lingers in her leaves for a day or a few days
before flying away with the evening (western
tanagers are nocturnal migrants although we have
no clue just how high they like to fly or what if
any celestial cues or guides they tend to use)
but the pause, however lightly stated, is in its
purest form. It is a natural flux captured with
the lightest of touch to mark the season's senses
of another place. We don't know where but in our
walking hides the holding moment of an individual
compelled in time. It is time. We have time.
It is time to see the Yucatan. It is time for us
to walk and to watch.
The date: 8/22/11
The week number: 34
The walk number: 1105
The weather: 80°F, partly cloudy
The walkers: Alan Cummings, John Beckett, Melanie
Channon, Darren Dowell, Vivica Sapin-Areeda
The birds (18):
House Sparrow
Mourning Dove
House Finch
Anna's Hummingbird
Acorn Woodpecker
Crow
Red-masked Parakeet
Black Phoebe
Lesser Goldfinch
Hummingbird, Selasphorus
Band-tailed Pigeon
Yellow-chevroned Parakeet
Orange-crowned Warbler
Red-whiskered Bulbul
Wren, species
Nuttall's Woodpecker
Western Tanager
Bushtit
--- John Beckett
Respectfully submitted,
Alan Cummings
9/7/11
http://birdwalks.caltech.edu/index.html
8/15/11
The big news of the day is that Alan's back is
back. He was walking a little gingerly but he
was also so mobile that it was Alan who was in
the lead and dictating the pace of the group. The
rest of us were littered in his wake. I thought
he might crater towards the end of the walk but
it didn't happen, so we have, once again, Alan's
march towards the big three zero (his one
thousandth walk).
The acorn woodpeckers were also back in force.
We saw three of them clustered together on a palm
tree, another flying in, and a fifth individual
at the top of a small oak in the Avery Garden,
hanging upside down. We all thought this last
sighting was very strange behavior for an acorn
woodpecker. Personally, I think he's been
watching too many bushtit videos. We spent a
little time sex typing the three woodpeckers on
the palm tree (one male, one female, and one
shy). In case you're interested, you look for a
black band between the white above the bill and
the red crest. Both sexes have an extensive red
crest but the red feathers on the males and
juveniles reach all the way down to white; in the
females, there is a black band between the red
and white. Incidentally, the juveniles carry
male plumage for their entire first year, which
led some early researchers to think there was a
heavy duty skew in the population towards the
males. The true male/female ratio is fairly close
to one.
Our species total for the day was 11, short of
the week 33 record high (14) but not too bad
considering the conditions and, of course, the
time of year.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
There were no rare captures for
this week, so I thought to linger for a parsing
moment on the meaning of a composition. Sridhara
brought his camera and, although noon is usually
a terrible time for easy photography, you can
still get lucky on occasion and the practice of
finding a strong composition is, to me at least,
more enthralling than whether or not you happen
to get a good photo. I know that Sridhara got at
least one excellent composition. There were
several red-masked parakeets in Tournament Park,
some in full panoply, nibbling on flowers or
seeds, and one bird providing only a partial
view. This parakeet had the usual prominent
white eye ring of his species surrounded by a
cherry red crown, then green with a hint of
shoulder red and a yellow-taupe bill, all framed
by the grayish brown notch of a tree with an out
of focus background contributing a soothing mesh
of duller green and suffused light. The bird,
curious about the clicking apparition flashing
light thirty feet below, was paying close
attention and, in the process, becoming lost in
pose. It reminded me, for no particularly good
reason, of Rembrandt's painting "Young Girl at a
Half-Open Door".
I don't know how Sridhara's story ended, as the
lighting was quite difficult, but it really
doesn't matter. This was an ephemeral
composition that some techno-bauble's resolution
could potentially have shared but not immured.
Having turned from the moment, however, I found
myself drawn to the opportunity. This bird
belongs in Ecuador. What's he doing here? The
answer, of course, lies in a breeding descent
from escapees or an intentional release. We have
no reports of this species on Caltech walks prior
to 1999 and broader surveys for the San Gabriel
Valley show a population of red-masked parakeets
rising from a couple dozen in 1997 to many times
that today. This is a bird on the ascent. Such a
response, however, bears another obvious fruit.
To what extent are we following the pet trade in
our walks? Red-masked parakeets (generally
referred to as red-masked conures or
cherry-headed conures in the pet trade) are
fairly popular as pets, although they are
definitely not for everyone because they can be
quite noisy (your ideal neighbor is either far
away or deaf). Many releases probably reflect
the inability of an owner to deal effectively
with their bird but a lot are likely accidental
escapes or intentional releases due to wild fires
(the Bel-Air fire of 1961 apparently provided the
core of west LA's feral bird population). If
you'd like a sense for the personality of
red-masked parakeets, you should pop some popcorn
and watch "The Wild Parrots of Telegraph Hill".
A perusal of the Caltech bird list yields at
least ten species introduced into southern
California through controlled or uncontrolled
releases and they come from a litany of the
broader world (red-crowned parrot - Brazil; house
sparrow - Europe; yellow chevron winged parakeet
- Brazil, Bolivia, and northern Argentina;
red-masked parakeet - Ecuador and northern Peru;
red-whiskered bulbul, common pea fowl and spotted
dove - India and south east Asia; yellow-headed
parrot - Mexico and Central America; European
starling - Europe; rock dove - Europe, northern
Africa and southern Asia; Budgerigar -
Australia). So, red-masked parakeets are not
alone in belonging elsewhere. Most of the people
who care about such things, also consider the
brown-headed cowbird to be an introduced species.
These birds used to mind their own business,
following the bison herds up and down the Great
Plains and adding mobility to their lives by
adding their speckled eggs to sparrow and warbler
nests (they are nest parasites). We kill off the
bison they depend on over an alarmingly short
period and, for many bird species, the silence of
a disaster like this might have been the sound of
extinction but, for cowbirds, it marked a great
awakening. We brought cattle and other livestock
through the Great Plains and introduced
brown-headed cowbirds to the revolutionary
concept that you can go east or west as well as
north and south. They were in Pasadena by the
early 1900s and they have been thriving ever
since at the local extinction cost of many open
nesting birds. Another possible introduced
species, cattle egrets, didn't get to the U.S.
until the 1940s but it's possible they actually
flew across the Atlantic without any help from
us. Let's see. It's eleven, twelve, or
thirteen (more if I missed some). However you
count, there are only 119 specific species in the
Caltech birding list, which means that roughly
ten per cent of the species we have seen on our
walks belong someplace else and, in the last
couple of walks, it has been more like twenty per
cent (2/11 and 3/13). I think we must be gods or
idiots. On the one hand, we exterminate our only
major native parakeet because the locals view
them as competition and food, not necessarily in
that order (Carolina parakeet), but we have, on
the other hand, introduced a wide variety of
exotic parakeets and other species into areas
without a consideration of consequence. Some
have produced stable feral populations locally
and others, like house sparrows and starlings,
have taken over the country.
The date: 8/15/11
The week number: 33
The walk number: 1104
The weather: 82°F, sunny
The walkers: Alan Cummings, John Beckett, Vivica
Sapin-Areeda, Kent Potter, Sridhara Chakravarthy
The birds (11):
House sparrow
Mourning Dove
Anna's Hummingbird
Acorn Woodpecker
Crow
Lesser Goldfinch
Common Raven
Bushtit
Red-masked Parakeet
Black Phoebe
Hummingbird, Selasphorus
--- John Beckett
Respectfully submitted,
Alan Cummings
8/19/11
http://birdwalks.caltech.edu/index.html
8/8/11
Alan is still down for the count, enough so that he had to cancel attending
a conference in China this week. So, here we were, alas, Alanless again.
The walk was nevertheless pleasant weather-wise compared to last week, 10 degrees
cooler and a lot drier and our bird count of 13 was a respectable showing,
although a couple shy of the week 31 record of 15.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
With a little luck we
could have tied the record as we saw a (nonphoebe) flycatcher near Morrisroe
that none of us could get a glass on before he dropped out of sight and,
later, Viveca saw what might have been a female oriole fly into a tree near
our northern turn off from Wilson but several minutes of coaxing failed to
yield the bird. On a more positive note, there were half a dozen band-tailed
pigeons ensconced around the Tournament Park area, which could be good for
us in the coming weeks, but the highlight of the day was seeing three acorn
woodpeckers along Wilson. Our typical acorn woodpecker sighting is of one,
or often more, birds hanging out on the trunks of palm trees towards the top.
They are most active early and late in the day, which is a disadvantage for
noon hour walkers but our odds are not too bad if there are woodpeckers to
be had. There just haven't been any acorn woodpeckers to be had for quite
a while. They are year-round residents in California (some from Arizona do
migrate) but families come and go, particularly if there is an acorn crop
failure or, more likely for Caltech, the destruction of a granary. Hopefully,
this family is going to stick around for a while. We have plenty of growing
acorns and the family is just in time to take advantage of the Fall harvest.
Perhaps it is a prurient sliver in ourselves that is the heart of
fascination but a discussion about acorn woodpeckers always seems to devolve
into snickery allusions to communal breeding. So, let's get that out of the
way. It is, after all, a serious and legitimate oddity among birds. There
are north of ten thousand species of birds in the world but in only ten will
you find two or more females laying eggs in the same nest (ostriches play the
same game although they have a very different, harem-based social system) and
in only 140 bird species do you see females consistently using multiple mates
in a given season (opportunistic polyandry, if you want to get fancy). In
California, acorn woodpeckers form family groups with one or two (occasionally
three) related breeding females (e.g., sisters) and 1-7 related breeding
males (usually 1-3), none of whom are related to the breeding females.
There are also typically some nonbreeding helpers (0-10) that are progeny
from previous seasons. This basic social fabric appears to be optimized for
1-2 breeding females and a total family size of about six. The females are
enforced synchronous breeders because a female will destroy any eggs laid in
her nest by other members of the same family until she starts laying eggs of
her own (yes, that means she is likely destroying her sister's eggs). This
may not sound very ethical from a humano-centric anthropomorphizing sort of
perspective but late hatching chicks in a clutch will generally starve to death.
Our female has a very good reason for keeping any head starts down to a minimum
and I can guarantee that her sister would do the same thing to her overly early
eggs were the roles to be reversed.
If you watch an acorn woodpecker for a while, you may see him fly out
20 or 30 feet and then pop back to more or less the same place he
started from. Your bird just got a wasp or a bee and I'm
sure he would tell you that it was really quite tasty. Flycatching is a major
and preferred source of food for acorn woodpeckers. They also eat beetles and
other insects and a family will usually have a favored sap-sucking tree. In
fact, acorn woodpeckers generally eat much more other stuff than acorns. So,
what's the big deal about the acorns? During the breeding season in the Spring
(they will occasionally also breed in the Fall if there is an exceptionally good
acorn harvest), there are a lot of insects around but the chicks get most of
them (high in protein, high in energy) and the adults eat acorns to make up for
some of this gifted protein loss. This is the essence of acorn hoarding. By
making do with acorns, which you can in principal, store up for a time of need,
you greatly increase the fledging weight and health of your chicks. So, where
does the communal breeding come in? A family will usually own one or more
source oak trees, although I have seen my local family storing walnuts on
occasion, one or more granaries (dead limbs, dead standing trees, telephone
poles), and a favorite anvil, where things can be pummeled before
consumption (crossbars on telephone poles are popular). This all takes
so much work to develop and defend that I tend to think of acorn woodpeckers
as the gardeners of the bird world. The acorns are only edible for about a
year and the previous Fall season's acorns tend to be consumed by summer, so
you are always working with the most recent acorn crop. Your granaries need
constant guarding because the local riff-raff like scrub jays or squirrels
would like to steal from your larder and the acorns shrink as they dry so you
can't just pop an acorn into a hole and expect it to be sitting there when you
want it a few months later. You are going to have to move it to a smaller hole
and, if you don't have a suitable smaller hole, you are going to have to make
one. If your old acorn hole gets too big or rotted out to be useful, you need
to make a new one. Has your old nest hole rotted out or been taken over by
starlings? Make a new one. At some point, you are resource limited but if
you have more males and females involved, or potentially involved, in producing
your chicks, there are more birds near you likely to help in caring for them.
More birds allow you to better defend against intruders into your territory.
More birds allow you to optimize your larder hoarding and more birds means
greater socialization. Also, this is good for the helpers. The down side
of the breeding scheme used by acorn woodpeckers is that breeding opportunities
for young birds can be quite limited. They aren't allowed to mate with their
parents and trying to move in with another family will lead to a quick
expulsion from the territory. The only time a breeding opportunity opens up
in a saturated area is when somebody dies. Since they can't go off and
breed immediately, at least not locally, the helpers often stay in their
natal territories and develop life skills, which gives them a better chance
of snagging breeding spots when an opportunity does come along. On the whole,
I would say that acorn woodpeckers have developed a robust but flexible
solution to an interesting resource problem. I'm a fan.
On another note, I think it might be worth pointing out that next week's
walk has the lowest record high bird count for any week of the year (14).
This is a very accessible total on a good summer day, so we have a shot
at making a little history.
The date: 8/8/11
The week number: 32
The walk number: 1103
The weather: 76F, sunny
The walkers: John Beckett, Vivica Sapin-Areeda, Kent Potter
The birds (13):
Northern Mockingbird
House Sparrow
Mourning Dove
House Finch
Anna's Hummingbird
Acorn Woodpecker
Crow
Red-masked Parakeet
Band-tailed Pigeon
Red-whiskered Bulbul
Selasphorus Hummingbird
Black Phoebe
Lesser Goldfinch
--- John Beckett
Respectfully submitted,
Alan Cummings
8/13/11
http://birdwalks.caltech.edu/index.html
8/1/11
Alan is improving by the day but a two mile walk,
or even a one mile walk, was just out of the
question. The usual rule is that you must do at
least half a walk in either time or space to be
credited with having been on it. I offered Alan
credit for the walk if he just made it to the
Maintenance Yard, a very good deal, considering
his office is in Cahill, which is essentially on
top of the starting point for the walk. Alan,
however, declined. That back is still one sick
puppy.
Before the walk, I heard a promising "rumor" from
a reliable source (George Rossman) that there had
been three acorn woodpeckers along Wilson at 10
AM. We didn't see them during the walk but I'm
hoping this means our palm trees have recovered
from their haircuts and that we will again see
the occasional acorn woodpecker. This species
lives in extended family groups and the whole
tribe tends to abandon an area if their granaries
are disturbed or a local oak tree chopped down
(i.e., you can go from frequent sightings to no
sightings almost instantly). I'm sure that
Caltech's palm pruning exercise was a big loss
but, perhaps, the memories of those evil times
are beginning to slip away.
It was a hot humid walk for us and I don't think
the birds were crazy about the weather either.
The conditions improved somewhat as the walk went
along (on a relative basis, mind you). The
temperature rose several degrees but the humidity
also dropped by several percent. On the positive
side, we had a three hummingbird day, which is
pretty good considering how hummer poor the last
few weeks have been, but we only made ten species
overall. I thought we were doomed to a single
digit day but, towards the end of the walk, we
picked up a lesser goldfinch, which put us into
double figures. To quote Vivica, "We worked hard
for them. I'm exhausted." I can't say I was
exhausted but I blasted through a liter of water
immediately after returning to my office and an
hour later I was still wet from the accumulated
sweat. My walk companions, Melanie and Vivica,
deserve gold stars.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
The highlight bird has to be the black-chinned
hummingbird. This is one of those species we
sporadically see rather frequently, ten times
each in 2007 and 2008 but in most years, it's
more like 0-2. We actually saw two of these birds
this week, probably both juveniles, one just
outside the Tournament Park parking lot and the
other on Wilson next to Morrisroe, although I
suppose it is possible that these were they same
bird.
Life is pattern and black-chinned hummingbirds
are a good example of how some of these patterns
intersect our walks. If you were to pull up
Alan's probability plot for this species, you
would probably conclude there was not much to see
but do a simple histogram and a clear pattern
emerges. There are two peaks. The first, which
has the highest maximum, occurs in the Spring,
during weeks 16-20 (i.e., mid-April to mid-May),
and there is a second peak with a long tail that
starts around week 24 (mid-June) and tails off
into mid-August. Although the maximum for this
second peak is lower, there are more than half
again as many sightings. So, what does this
mean? Our black-chinned hummingbirds winter in
Mexico. During the Spring, most of them migrate
past us to find suitable, preferably riparian,
nesting territories to the north, although a few
do choose to breed in our area. First, the males
come through and then, about a week later, the
females pass by. Exactly which couple of weeks
this happens varies from year-to-year and, in
most years, we get 0-1 sightings from this group.
In mid-to-late June, the male black-chins migrate
back down to Mexico, pretty much in a lump as
they did coming north. The adult females and,
especially, the juveniles lag behind and take
their time in migrating. This leads to a
tail-off in Caltech sightings after June for any
given week but since there are a third more birds
involved, spread out over a much longer time
period, we end up with more sightings from the
southward migration.
And now for the factoid of the day: black-chinned
hummingbirds currently hold the record for the
smallest genome among all bird species (910
million base pairs) and, in fact, they currently
hold the record for all amniotes. You shouldn't
think of this as a source of disparagement,
however, because it clearly works for them.
The date: 8/1/11
The week number: 31
The walk number: 1102
The weather: 87°F, sunny and humid
The walkers: John Beckett, Melanie Channon, Vivica Sapin-Areeda
The birds (10):
House Sparrow
House Finch
Anna's Hummingbird
Crow
White-throated Swift
Red-masked Parakeet
Bushtit
Hummingbird, Selasphorus
Black-chinned Hummingbird
Lesser Goldfinch
-- by John Beckett
Respectfully submitted,
Alan Cummings
8/8/11
http://birdwalks.caltech.edu/index.html