3/26/12
We had high hopes as we set out on a beautiful,
cloudy day, just a day after a rain that
had blanketed the area. Darren said he would
not be satisfied with anything less than 30 bird
species. Darren wound up not satisfied. We
observed 25 species, which is 5 above the median
for a week 13 but way below the maximum, 37, which
is also the maximum observed for any week of the year.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
The hightlight for me was the little flock of Chipping
Sparrows seen in the maintenance yard. This is only
the second time this bird species has been recorded on
the walks. The first time was earlier this year.
So that was neat.
The other neat thing was the Common Yellowthroat sighting.
It was a brilliant male perched on a big boulder. Earlier
in the day I had seen a female or a juvenile so there is
more than one of this species on campus. Neat.
The date: 3/26/2012
The week number: 13
The walk number: 1136
The weather: 60°F, partly cloudy
The walkers: Alan Cummings, Darren Dowell, Matt Bradford, Vicky Brennan, Viveca Sapin-Areeda, Kent Potter, Tom Palfrey
The birds (25):
House Sparrow
Mourning Dove
House Finch
Anna's Hummingbird
American Crow
Yellow-rumped Warbler
European Starling
Lesser Goldfinch
Band-tailed Pigeon
Snowy Egret
Red-shouldered Hawk
Dark-eyed Junco
Orange-crowned Warbler
Black Phoebe
Turkey Vulture
Chipping Sparrow
Nuttall's Woodpecker
House Wren
Ruby-crowned Kinglet
Red-whiskered Bulbul
Bushtit
Common Raven
Yellow-chevroned Parakeet
Hummingbird, Selasphorus
Common Yellowthroat
Respectfully submitted,
Alan Cummings
3/28/12
http://birdwalks.caltech.edu/index.html
3/19/12
The temperature was even cooler than last week
and we had fewer birders, as Alan and Darren were
both absent. The walk nevertheless began very
well. Kent brought a snowy egret and the
Maintenance yard was quite productive. We left
with 17 species and I am thinking that we are
going to bust through the thirty bird barrier, as
we had in the preceding two weeks, but the
playing field, track, and Tournament Park yielded
almost nothing (a house sparrow that we were
happy to get from the playing field and a
band-tailed pigeon from Tournament Park). We
managed to pick up a few species in the second
half of the walk and got some very nice views of
a small flock of western bluebirds (east side of
Wilson near Mead), perhaps the same group we saw
a couple of weeks ago. However, the numbers of
new species advanced slowly. Some regulars like
the yellow-chevroned parakeet that have been
reliably ensconced at mid-day in one of the
silk-floss trees outside the student services
building on Holliston, appear to have moved on.
Finally, we arrive at the Throop ponds, the
official end of the walk. A snowy egret is
foraging along the shore of the lower pond. He
puts on a great show by catching a minnow but he
doesn't add to the species total because Kent had
seen him earlier. I don't hear or see the
common yellowthroat but this wasn't unexpected
given the lack of Alan's portable song
contraption and my inability to hear him unless
he is singing within two or three meters of me
(this has happened a couple of times but not
today). I walk up to the second pond, hoping to
see our mallard on mallard rock but he isn't
there. This leads to a lightly flushing
annoyance over a drake's lack of consideration
(he was there at 3 PM and again at noon on
Tuesday) when the gelding thought evaporates in
the extended chatter of a mountain chickadee,
only a few meters away. We had our last bird of
the day and 22 for the walk. This total is
respectable and well above both minimum (12) and
median (19) but the construct of expectation
posed by the preceding two weeks of stellar
species counts and an early great start made it
somehow disappointing. I had allowed myself to
be caught up in a numbers game.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
For the bird of the week, I would like to
nominate the pair of American robins we saw in
the Maintenance yard. The light was so harsh
that the breasts appeared almost yellow at times
but the birds were close enough so that pose,
field markings, and ultimately the red breasts
were all bringing internally consistent
indicators of species. We also had a bird in bad
light perched at the top of a tree. This bird
was patient but did not provide a good look.
After much looking, mulling, and consultation we
went with the identification of a female hooded
oriole and I wrote this down on the tracking
list. However, the identification kept gnawing
at me as the walk proceeded and, by the time we
turned east off of Wilson, I had crossed it out.
Hooded orioles are currently present in the area,
though rare (most of them are coming through
later in the Spring) but the id was shaky and, I
think, ultimately not up to our standard level of
confidence for calling a bird.
So, with the hooded oriole discarded, the bird of
the week is the American robin. If you look at
Alan's probability plot for this species, you
will see two large masses of sightings, early and
late in the year, which is consistent with a
wintering bird that migrates away from Caltech in
the Spring. The apparent duopoly is artificial
because the wintering season cuts across the
artificial boundary between successive calendar
years. This becomes really apparent if you
simply shift the x-scale and plot from weeks -25
to +26 (i.e., from late June in one year to late
June in the next year) instead of weeks 1 to 52.
This procedure yields a distribution with the
bulk of the data looking like a reasonably good
Gaussian (I haven't tested it) centered roughly
around week 8 (i.e., late February) and a second,
smaller, peak centered around week 42 (mid- to
late October). My Fearless Fosdick suggestion is that
the small peak is driven by general migration of
robins passing through Caltech on their way here
or to other wintering locales and that the large
peak reflects local wintering birds whose daily
track, which probably runs over a couple of
kilometers, happens to intersect our route at
just the right time. We don't see a migration
peak in the Spring but I suppose that this may be
a hidden shoulder in the large peak. We also
don't see robins in the sumemr, which suggests
that we don't have a lot of robin nesting
activity on campus, although they are known to
nest in the general area.
If you take a four year running average of
American robin sightings to damp out some of the
year-to-year variability and account for
artificially splitting seasons by using calendar
years, you get a cyclical variation with an
apparent wavelength of about 14 years and minima
around years 1995 and 2009. The late eighties
peak was ten or eleven sightings per year versus
seven or eight in the early two thousands,
suggesting that our local population of robins
experienced a decline in population from highs in
the eighties, perhaps something as simple as
shifts in preferred berry-bearing bushes. Robins
are predominately frugivores (fruit eaters) in
the Fall and winter, so much so, that they are
viewed as agricultural pests in the berry
industry (e.g., cherries, blueberries, and
grapes). The minima in sightings per year are
similar at about five, suggesting stabilization,
but I worry that this may be compounded by a
greater average number of birders on the walk
increasing the probability of seeing a smaller
number of robins. We see this phenomenon in the
sightings of turkey vultures on the bird walk.
The numbers have been increasing in recent years
but this is because more people, on average, are
looking for them.
If you are a virus and you want to generate a
global pandemic in some species, you need a
designated victim, a vector by which the disease
is transmitted, and a super spreader, which need
not be the same species as the intended victim.
Ebola creates a very nasty deadly disease for
humans but it's not, at least in its recent
incarnations, a pandemic threat because it kills
an infected human so fast and in such a horrible
way that the victim has few chances to spread the
disease to other humans. You can think of West
Nile Virus (WNV) as a sort of Ebola for crows. If
an infected mosquito (the vector) bites an
uninfected crow, it transmits WNV to the crow.
If a second uninfected mosquito then bites the
now infected crow, it too will become a carrier.
However, once infected, the crow tends to die
quickly so that he has relatively few
opportunities to propagate the disease through
additional mosquito bites. Enter the robin.
American robins are widespread and numerous in
North America and they tend to roost communally.
Mosquitoes prefer robins to other birds like
sparrows (don't ask me why) and robins can
tolerate WNV far better than crows. American
robins are the super spreaders of WNV and this
gives us the makings of a crow pandemic. So, if
you don't like crows and view WNV as a way to
drop the local crow population (you also have to
not like other members of the crow family like
jays and ravens), you should thank your lucky
robins.
The date: 3/19/2012
The week number: 12
The walk number: 1135
The weather: 53°F, sunny
The walkers: John Beckett, Viveca Sapin-Areeda, Kent Potter, Vicky Brennan
The birds (22):
Northern Mockingbird
House Sparrow
Mourning Dove
House Finch
Anna's Hummingbird
American Crow
European Starling
Hummingbird, Selasphorus
Common Raven
Yellow-rumped Warbler
Snowy Egret
Western Bluebird
Red-whiskered Bulbul
Ruby-crowned Kinglet
Cooper's Hawk
Lesser Goldfinch
Spotted Towhee
Black Phoebe
American Robin
Band-tailed Pigeon
Bushtit
Mountain Chickadee
-- John Beckett
Respectfully submitted,
Alan Cummings
3/26/12
http://birdwalks.caltech.edu/index.html
3/12/12
The temperature was cooler than last week by 20 degrees but the birds were in great abundance
and in a fine fettle. In the Maintenance yard, Darren was practically on fire, calling out species
and waving in various directions faster than the rest of us could turn our heads but the visuals
came eventually. Overall, we encountered 30 species and, had it not been for a 35 species walk
in week 11 of last year (second best all time), we would have tied the record for the week.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
Although there was a fair amount of overlap in species with the walk last year and we had nine
species that we didn't see then, the 2011 week 11 walk cleaned up on hawks (including a
Swainson's), towhees, wrens, and warblers and we just couldn't match the collection. I have to
admit that I would certainly like to have seen another Swainson's hawk but we have nothing to
complain about. We had a very good walk.
I have come to think of thirty bird walks as a fairly standard signature of the Spring migration.
It's a very good week when we hit thirty but it doesn't bear a histrionic caricature breasting
decades. After all, we had 32 birds last week and, last year, we had five walks with thirty or
more species. However, this shows a lack of context. From a historical perspective, 30+ species
walks are extraordinary with only ten such walks all time (out of 1134 walks), all but one in the
band of weeks nine to thirteen (the record dips to a mere 29 in weeks fourteen and fifteen), and
all ten of these 30 species walks can be found in one of three years, 2006, 2011, and 2012. So,
we are walking in lucky times.
Although I had thirty species to choose from, there was no obvious candidate for the bird of the
week. Usually, I try to pick an unusual bird or an unusually good view of a bird but, this week,
we didn't really have a reasonable candidate. Identifications were solid but not special. So, I
will go with another of Melanie's new lifers, a decent but not spectacular look at a red-crowned
parrot camped out on Wilson but not talking.
Red-crowned parrots are the dominant Caltech area parrot right now but this hasn't always been
the case. They've been in the San Gabriel Valley since at least the early 70s but we first
encountered them on a walk in 1996. Between 1996 and 2006, we would see them in two
pulses, centered around weeks 8 and 48. So, these were mostly Fall/winter birds for us. We
didn't see red-crowned parrots at all between 2007 and 2009 but, we had seven sightings in 2010
and ten last year. The new pattern of sightings is, however, completely different from what it
was a decade ago. Our red-crowned parrots are now Spring birds with a skewed peak cresting
around week 20 and a drift to the odd sighting during the Summer. There has been a paradigm
shift and the timing suggests that we now have a local breeding population that goes elsewhere
after the nurseries break up. Since red-crowned parrots are secondary hole nesters, our local
woodpeckers must be working overtime to accommodate the demand.
We have two parrots (red-crowned and yellow-headed) and two parakeets (yellow-chevroned
and red-masked) that currently frequent Caltech. Visually, the quick way to separate the parrots
from the parakeets is through the tail. Parrots have relatively stubby tails and parakeet tails are
pointy.
However, I want to discuss a different approach to identification. Each of these four
species has a distinctive voice and, with a little practice, you can identify which one you are
dealing with solely based on the sound. In fact, I would suggest that this grouping of four exotic
feral avian species may be the best place to start building an auditory vocabulary for local birds.
They are loud and, generally, not shy. They talk a lot, especially when in flocks, and, even better,
I can actually hear them. So, how do you sort them out short of seeing a flock in action and,
over time perhaps, learning to associate a particular call with a particular species? Generally, if
you ask a birder about where to go to hear bird songs and calls, you are sent to the Cornell site
(http://www.allaboutbirds.org). This is a well organized site specializing in American birds and
you will get a typical song and, perhaps, a typical call. However, exotics like parrots and
parakeets are not included in the Cornell site and you will, based on what this site has to offer,
often find yourself with a slim collection of voice relative to what the bird of interest can
produce, even if it happens to have your bird. You don't gain anything on this front if you have
a subscription to the Birds of North America, which is also run through Cornell. It is fairly rich
in information (I use it as a back stop for background on birds of the week) but does not have a
value added vocal component. This is a problem for building an auditory vocabulary because
many species of birds have flight calls, perching calls, songs for males, songs for females,
assorted non-call noises and seasonal and regional dialects on all of the above. So, unless your
Cornell bird happens to mesh with your local target, you may have a hard time getting a sense for
either the variations or the commonalities.
An alternative site more suited for picking up some
auditory expertise is (thank you George Rossman) xeno-canto (http://www.xeno-canto.org),
which has an extensive collection of calls and songs, currently with representation for nearly
8000 species of birds (i.e., about 80% of all bird species). There are, just to pick something at
"random" because I happened to have heard one the other day, 56 recordings of the white-
breasted nuthatch. There are four recordings of red-crowned parrots (listed under red-crowned
amazon), none for a yellow-headed amazon (you can't win them all but here are a couple of
recordings if you want to pursue the species: http://www.youtube.com/watch?v=EmpFBIhYBgU
and http://www.westernsoundscape.org/audio/yellow-headed-parrot-pasadena.mp3), 17 for red-
masked parakeets and 21 for yellow-chevroned parakeets. Personally, I find going through a lot
of examples of something, whether it be a visual or auditory problem, a much better way to get a
sense for a bird species than memorizing one recording or image and hoping that you can stuff
your bird into the same frame. That's a dangerous proposition if you have to do any judicious
cropping and blending to make the species fit.
The date: 3/12/2012
The week number: 11
The walk number: 1134
The weather: 60F, partly cloudy
The walkers: Alan Cummings, Viveca Sapin-Areeda, John Beckett, Melanie Channon, Darren Dowell, Vicky Brennan
The birds (30):
Northern Mockingbird
House Sparrow
Mourning Dove
House Finch
Anna's Hummingbird
American Crow
Lesser Goldfinch
European Starling
Yellow-rumped Warbler
Mallard
Swift, Species
Orange-crowned Warbler
Cooper's Hawk
Dark-eyed Junco
Bushtit
Black Phoebe
Mountain Chickadee
American Goldfinch
Downy Woodpecker
Turkey Vulture
House Wren
Nuttall's Woodpecker
Ruby-crowned Kinglet
Common Raven
Red-whiskered Bulbul
Hummingbird, Selasphorus
Red-crowned Parrot
Band-tailed Pigeon
Yellow-chevroned Parakeet
Common Yellowthroat
-- John Beckett
Respectfully submitted,
Alan Cummings
3/16/12
http://birdwalks.caltech.edu/index.html
3/5/12
It was a warm day, nearly thirty degrees higher than the 54F of last Monday and the air seemed
to exude a feeling of Spring, if not summer. I have to admit that my expectations were not high
because of the unseasonably warm weather but the birds certainly knew the time. It is the time
of El Norte. It is time, at least for the early birds, to move into breeding grounds. Our Say's
phoebe is gone, off to the desert, but we had white-throated swifts swirling around Millikan and
saw our first house wren of the year. In absence and presence, these are sure signs of Spring.
Our common yellowthroat is still hanging around the Millikan ponds (actually the Indian
hawthorns to the east of the ponds). He was our last bird of the walk and he capped a four
warbler day. The common yellowthroat is in clear breeding plumage now, another sure sign of
Spring. We got a western tanager, a dark-eyed junco, though not before complaining that we
hadn't been seeing any, and an undeserved but happily accepted snowy egret. We also saw a
couple of chipping sparrows, the first new species for the Caltech bird list since the great rock wren
extravaganza of 2010 and we did fairly well with year-round residents. We ended, fittingly,
with the common yellowthroat and 32 species, our first 30 plus species walk of the year, a new
record species count for week 10, and our second new record for this year.
See the plots at
http://birdwalks.caltech.edu/bird_data/species_time.html
and
http://birdwalks.caltech.edu/bird_data/two_plots.htm
Before mentioning the obvious highlight chipping sparrows, it seems appropriate to say
something about the white-throated swifts. We have been seeing them off and on around town,
especially near the Colorado Street bridge over the arroyo, but only rarely around Millikan and
the ones that we have seen on campus but off walk didn't seem to want to stay with us long
enough to be captured at lunch time. This batch of birds seems more serious, for some reason,
and perhaps these are going to be nesting birds or, at least, persistent lunch time snackers. Over
the last dozen years, week 11 is the average for the first appearance of white-throated swifts on
the bird walk, so week 10 as the first sighting of the year is not atypical (also true of house
wrens, incidentally).
The Caltech bird walk was started in 1986 and we have been seeing white-throated swifts since
1987. It was, however, not until 2004 that we started consistently bringing in more than half a
dozen sightings a year (the running average has been six or more since 2000). Part of this may
reflect scheduling conflicts (swifts' scheduling, not ours) that leaves the swifts out of
visual/auditory range during the noon hour (we have this problem with starlings, easy to find at
8 AM and 5 PM but a hard catch at noon) and part of this may be due to the fact that the swifts
didn't make Millikan a regular center of attention until several years ago, even though the library
has been available for nesting and foraging since 1967. If you plot a four year running average of
the number of sightings per year as a function of leading (i.e., most recent) year, you get a steady
rise from 1994 to 2004, followed by a slow decline with a hint of another rise over the last
couple of years.
Within a given year, we can generally count on seeing our first white-throated swifts sometime
around week eleven, as noted above, and this is followed by a slow steady rise in probability,
peaking around week 20 (mid-May), followed by a slow decline to week 30 (mid-July),
consistent with local breeding and dispersal. There are additional pulses of sightings around
weeks 32 (early August) and 38 (mid-September), which are likely associated with migrating
swifts passing through on their way south, but we can have a swift sighting at any time of the
year. One thing I like about swifts, in general, is that they do practically everything in the air.
Obviously, they catch insects on the fly (they have small beaks but relatively large gapes so they
can swallow a large insect without first landing somewhere to pummel it into submission or break
it up into smaller pieces). White-throated swifts also preen in the air, take baths in the air (they
hit the water on the fly to soak up the water), and court in the air with chasing and communal
dives. The pair dives can be spectacular, sometimes dropping several hundred feet in the process.
I have seen a pair hit the ground in one of these dives but, usually, they (always a male and a
female) break up before a collision occurs; it's not known whether this is strictly a courtship ritual
or if mating is involved. White-throated swifts have taken nicely to tall buildings, so
urbanization is not necessarily a bad thing for them, and they have been lately expanding their
breeding range northward, although overall numbers seem to be in decline.
So, we saw a couple chipping sparrows (after Darren heard them and tracked them down to a
tree by the driveway running towards Tournament Park). You might not think of this as a
shocking event but it is. This was the first ever occurrence for a chipping sparrow on the Caltech
bird walk. The Caltech bird list now stands at 136 categories (specific species plus ambiguous
catch alls like "hawk, species") and 121 separate species, not bad for a non Arboretum, non
wetlands, thoroughly urban institutional setting.
I've found the lack of Caltech chipping sparrows to be an oddity for some time. I see this species
at home (Sierra Madre) pretty consistently in the Spring and, at least in breeding plumage, these
birds are hard to confuse with anything else. In the Spring, they will have a dark bill, a
prominent rusty red cap with no medial strip, and a sharply defined, virtually definitive, dark eye
streak with a whitish supercilium between the streak and cap. These are hard to miss features if
you have a decent look at the bird, so it would seem that we must never have gotten a decent
look at one over the last couple of decades. I'm told that chipping sparrows sound a lot like
dark-eyed juncos. Dark-eyed juncos are not especially common for us, so we would certainly
have tried to locate any talking bird that sounded even remotely like a dark-eyed junco. I don't
think we missed any chipping sparrows because of auditory misidentification. It's a curiosity (I
tend to put our lack of Costa's hummingbirds in the same cabinet). During Spring migration,
chipping sparrows usually move in small flocks of a few to a few dozen, with periodic stops for
refreshment. That's probably what we encountered, a small flock stopping at Caltech for the day
before moving on. In the Fall, chipping sparrows tend to travel in large flocks and that's
potentially easy to miss.
I'll leave you with a couple chipping sparrow nuggets. The first is that, although you would be
correct in thinking that chipping sparrows eat mostly seeds, they also eat a lot of insects and
spiders during the breeding season, a third or more of their diet (you can get similar observations
for hummingbirds with respect to nectar/insect loadings in the diet). These are high energy
snacks and are likely important for fledging success (a decline in house sparrows in Britain can be
tied to a decline in the local spider population). A second tidbit is that chipping sparrows appear
to be an example of taxonomic over-splitting of species. There are three named subspecies
currently accepted by the American Ornithological Union but mitochondrial DNA shows no
differences among them. That doesn't mean that there aren't genetic differences but it does
suggest that a little suspicion may be in order and, naturally, that fits in with the Caltech way.
The date: 3/5/2012
The week number: 10
The walk number: 1133
The weather: 81F, partly cloudy
The walkers: Alan Cummings, John Beckett, Darren Dowell, Vicky Brennan, Viveca Sapin-Areeda
The birds (32):
Northern Mockingbird
House Sparrow
Mourning Dove
House Finch
Anna's Hummingbird
American Crow
Mallard
Red-shouldered Hawk
White-throated Swift
Yellow-rumped Warbler
Black Phoebe
Lesser Goldfinch
Ruby-crowned Kinglet
Orange-crowned Warbler
Nuttall's Woodpecker
Gull, species
House Wren
Common Raven
American Robin
Chipping Sparrow
Red-whiskered Bulbul
Dark-eyed Junco
Red-tailed Hawk
Bushtit
Western Tanager
Townsend's Warbler
Hummingbird, Selasphorus
Cooper's Hawk
Band-tailed Pigeon
Yellow-chevroned Parakeet
Snowy Egret
Common Yellowthroat
-- John Beckett
Respectfully submitted,
Alan Cummings
3/9/12
http://birdwalks.caltech.edu/index.html