364
WonT.,NotesonHurnrningbirds
at Chiriqui,
Panama
NOTES ON HUMMINGBIRDS
BY
C. BROOKE
AT CHIRIQUI,
[Auk
L July
PANAMA
WORTH
HUMMINGBIRDS
are amongthe mostdistinctivecreatures
of the tropical Americanavifauna,yet muchremainsto be learnedabouttheir
specific
habits. Amongthe manyobservations
of Panamanian
hummingbirdswhich I recordedin my journal during the summerof
1937 at Chiriqui, the following were of particular interest. I was
much surprisedto find that severalspecies
of hummingbirds
have
quite characteristic
songs,utteredfrom a perchwith the sameregularity as the 'set'songsof passerine
birds. OnceI had learnedthe
identity of the singer,I found it possibleto detectits presenceby
ear with the samecertaintythat a United Statesornithologistfeels
in identifyingwarblersand sparrowsby their songs.
Fewof the hummingbirds
had songs
whichcouldbe calledmusical.
The one which cameclosestto consonance
and harmonywas that of
a small specieswhich, unfortunately,I failed to identify. Its song
wassomethinglike the thin first attemptat singingof a youngSong
Sparrow,having a lisping and slightlydisconnected
quality which
suggested
lack of practiceor skill. The song,nevertheless,
wasvery
constantin its style,and I usedto hear it frequentlyin the late afternoon and early eveningalongthe Rio Garachfi,particularlyon rainy
days. The singersat quietly near the end of a small twig, intermittently throwing its head back to sing, when its throat could be
seenpulsatingwith the expiratory effort. Betweensongsit would
perch quietly, perhapspreeninga few feathers,again with typical
passerineabandon.
Speciesof hummingbirdswhich sang thus were also possessed
of
the commonharshinsect-likebuzzesand twitteringsgivenduring pursuit of one another. In this type of vocal demonstrationhummingbirds seemto resembleone anotherclosely,while their 'set' songsare
widely different and specificallycharacteristic.
The song of Bangs'sHermit, Phak'thornisguy coruscus,is very
soft and can be heard for only a very short distance. It has the
peculiareffectof seemingto proceedfrom a more remoteposition
than the singer. Its character,besidesthat of ventriloquism,is remarkablefor the jumble of notesof which it is composed,
suchas
might be producedby severalbirdsat one time. BeforeI had identified the song,in fact, I thoughtthat I washearingfainfly the hunger
criesof a nestful of fledglingwoodpeckers,
or of someother holenesting bird. As I searchedand searchedfor the nest, the sounds
Vøl'n0'l
WORTH,
Noteson Hummingbirds
at Chiriqui,Panama
365
would shift their direction,for the hummingbirdwould fly to a new
perchasI nearedit, and I had finally decidedto give up the hunt in
exasperationwhen I was amazedto seea Bangs'sHermit producing
the entire illusory chatteringitself. It sat quite still, only turning
its head slowlyfrom sideto side,and uttering a seriesof low liquid
twitterings. ThereafterI frequentlyheardthe samesong,and I then
becameaware that Bangs'sHermit was a very commonspeciesin
the forestsof Chiriqui.
The most persistentsinger of all was De Lattre's Saber-wing,
Campylopterus
hemileucurus,
althoughits songwas lessdefinitely
'set.' This hummingbirdwould often sing for an hour at a time:
chick chick chick chick chick chick chick-ta-lil chick-t'lil chick-ta-lil
chick chick chick chick chick chick chick-t'lil chick chick--and so on
endlessly
it wouldsingloudly. The rhythmwasperfectlyregular,the
intervalsbetweenchicksbeingone-halfor two-thirdsof a second. The
song'got on my nerves'after spendinga morning in the forest. It
wouldseemto becomelouderuntil it filled my earsand ! couldhear
nothing else.
I cannot state for all the speciesof hummingbirdsI observed
whether the femalesever sing,but in the caseof De Lattre's Saberwing, at least,phonationof this sort seemsconfinedto the males.
Closelyassociated
with the phenomenon
of songis the hum of hummingbirds. Pettingillhasrecordedvibrationfrequencies
of seventyfivewing-beats
per secondduringforwardflightin the Ruby-throated
Hummingbird,Archilochuscolubris,and fifty to fifty-fivewing-beats
per secondduringhovering(Bird-Lore,39: 194, 1937). Most of the
hummingbirds
at Chiriquiproduceda hum aboutthreeoctaves
below
middleC, whichsuggests
sixty-four
vibrationsper second.Pettingill's
recordsare basedon actualphotographic
analyses
with a high-speed
camera,while mine are purelythe resultsof personaljudgment. It
happens,however,that I possess
that peculiarfacultyknownby
musicians
as'absolute
pitch,'sothatI am confident
of thefrequency
stated above.
The toneof thehummingwasnot a pureone. In the background
therewasa raspingnote caused,I believe,by frictionamongthe
feathers,
probablyin theregionof the wings'insertioninto the body.
The actualhumming,moreover,
wassubjectto variationsin pitch
whichcovereda rangeof approximately
threehalf-tones(i.e., from
sixty to seventy-two
vibrationsper second).The highestpitch was
producedwhile the birds were feeding,particularlyif they had to
probedeeplyinto a blossom,when their headswere out of the nor-
WORTH,
Noteson Hummingbirds
at Chiriqui,Panama
366
['Auk
L July
mal relationshipto their bodiesand the excursionof their wings
wasrestrictedby crampedquarters. The next-highestpitch wasproduced at the moment
of acceleration
when the birds darted
off.
Once
started,the pitch droppedanotherhalf-tone,while the lowestnote
of all was producedduring uncomplicatedhovering,that is, while
the bird took its bearingspreparatoryto its next move. Thus:
Maneuver
Uncomplicated
Normal
Hovering Flight
Pitch
B
C
Frequency
60
64
Accelerated
Flight
C •
68
Feeding
D
72
So far as an estimateof the speedof flight of the variousspecies
is concerned,
I canonly saythat theyall frequentlyflewwith extreme
rapidity. On oneoccasion
I wasproceeding
alonga foresttrail when
I heard the pursuit-squeakings
of a pair of hummingbirds
aheadof
me. They cameinto view at a distanceof a hundredyardsand then
speddirectlydown the trail about a foot from the ground,banking
heavily three timesin order to get past three almostimperceptible
bends in the trail. Their speedwas such that unlessthey had
bankedtheywould haveshotoff into the forest. As they passedme I
could see only a streak of birds, and for this reason I cannot state
their identity. My estimate,which is only very casual,is that they
coveredthe hundred yardsin three secondsor less;their speedat this
rate would havebeen at leastseventymilesper hour. Whateverthe
speedof this particularpair of birdswas,I do not regardit asexceptional for any of the hummingbirds. The Ruby-throatedHummingbird hasbeentimedat fifty-fivemilesper hour duringnormalcruising
flight (Allard, in Auk, 51: 84, 1934).
The high pitch producedduring feedingwasespeciallynoticeable
in Bangs'sHermit. With its long decurvedbill, this bird has some
difficultyin properlyapproaching
a bananablossom,
for it mustprobe
within and betweenthe parallel tiersof tubular flowers,and theseare
situatedin a vertical position. The bird would fare better if its
beak were recurveddorsally,for under existingcircumstances
it is
necessary
for it to maneuverinto a positiondirectly below its goal
and then to thrust its bill straight upward into the blossoms.It
seemsto find this position awkward and difficult to maintain. On
one occasionI watcheda Bangs'sHermit probingits way systematicallyalongthe rowsof blossoms
whena largeinsect,whichI believe
wasoneof the carnivorous
nocturnalcrickets,suddenlyappearedon
Vol.•0-I
WORTH,
Noteson Hummingbirds
at Chiriqui,Panama
367
a part of the main globularbananabud just belowthe lowesttier.
The insectmayhavehadeggsor youngconcealed
in oneof the flower
crypts,for it guarded a set area on the bud and did not allow the
hummingbirdto probethe blossoms
in that vicinity. Unfortunately
it was becomingdark, and I could not see all the details of this
engagement,
althoughI stoodonly a few yardsaway. The hummingbird seemedto acknowledge
the insect'spower or authority,for it
did not infringe on the dangerzone,though it workedsystematically
to its very edge. The insectoccupieda strategicpositionto ward
off the bird, for to insertits bill the hummingbirdhad to approach
the flower until its breast touchedit, with the body then vertical in
position. During normalhoveringthe bird'sbodywasheld at about
forty-fivedegreesfrom the horizontal. As long as the insectmaintaineda stancebelowcertainblossoms,
it couldsuccessfully
hold the
bird at bay. This presupposes
that the bird recognized
somedangerous quality, such as a sting or severebite, in the insect. Were the
flowersdisposed
horizontally,or were the bird'sbill curvedupward,
the Phak'thorniswould not have had to touch its breast to the bud, and
the insectwouldhavehad lessjurisdictionoverthe bird'sfeeding.
Bangs'sHermit suspends
its nestat the tip of a blade of a palm
leaf. Its two eggsare dull white in color and average17.5x 11 mm.
in their dimensions.A large number of Chiriqui hummingbirds
adopta similarsitefor their nests,accordingto SefiorT. B. M/Snniche,
my hostat Boquete. I foundapproximately
the samemethodin use
by the BronzyLeastHermit, Glaucishirsutaaenea,exceptthat the
nestsof thisspecies
wereinvariablysuspended
from a ribbonof banana
leaf.
The BronzyLeast Hermit, not previouslyrecordedfrom the Republic of Panama,is very commonin banana grovesof the Rio
Garach•regionin Chiriqui. I wasfortunatein observingthree occupiednestsof this species,
and all agreedin their locationand structure. Banana leaves,when old, becomesplit transversely
in many
placessothat the bladeof the leaf hangsin ribbonsfrom the midrib.
Wherethe midrib is nearlyhorizontalthe ribbonsdependvertically.
The hummingbirds
selectoneof theseribbons,preferablyoneabout
an inch in width. The nestis placedon the underor inner sideof
thisribbon,to whichit is fastened
by the useof downyplant fibersand spiderwebswhich encirclethe ribbon tightly. No anchorage
to the midrib is used. On this foundationthe nestcup is erected,
ratherhigh (thatis,closeto themidrib). It is largeanddeep,being
veryloosely
built of rootlets,sothat the eggsmaybe seenthroughthe
368
WORTH,
NotesonHummingbirds
at ½hiriqui,
Panama
['Auk
L July
structurefrom below. There is an attemptat concealment
evidenced
by the placingof additional material below the nest to the very tip
of the leaf-ribbon. The nest is both secureand waterproof,for it is
protectedby the main blade of the leaf overhead. Shouldthe midrib be broken,the ribbon will still hangverticallydue to the weight
of the nest,and rain which might then gain accessto it will easily
drain out throughits open structure. The nestswere usuallyplaced
about ten feet from the ground. ! watchedone during its construction. The cupwasnot yet finishedand the adult, to affixnew fibers,
still had to hover at its work. It workedwith its feet on the partially formed lip of the nest, its wingsvibrating, and manipulated
somethingwith its head and beakat the edgesof the leaf-ribbonabove
any point where I could seeactual nestingmaterial. I felt sure that
it was working at the fiber and spider-webguy-wireswhich must be
the critical point in sucha precariousstructure. The eggs,which
are laid in June and July, were invariablytwo in number,measuring
15x9 and 16x9 mm. in one case. They were placedin the nests
with their oppositepolesmutuallyadjacent.
The young birds were quiet most of the time. They huddled
deeply in the nest when ! examined them; indeed it was possible
to invert the entire nestwithout emptyingout the fledglings. Their
natal
down harmonized
well with
the rootlets, fibers, and small
amount of lichen adoming the rim of the cup, so that one might
look into the nestbut scarcely
seeyoungbirdsin it. In feedingthe
youngthe parentwould perchon the edgeof the nestand seemingly
probe them with its curvedbill in true hummingbirdstyle. Then it
would fly off a few feet and, hovering,run its tonguein and out
severaltimes,and then return to feed the youngagain. It apparently had to get clearof the nest'scloselyoverhanging
roof (the midrib of the bananaleaf) to regurgitatea new portionof its crop'scontents. Having done so, it would then return to the nest and deliver
the new consignment
to its young. This forcingof the bird to sally
forth for free regurgitationduring feedingof the youngmay afford
an unexpected
protectionto thisspecies,
for it can therebydetectthe
approachof intruderssoonerthan it otherwisewould.
At least twenty-fivespeciesof hummingbirdsare known to occur
in the Chiriqui region. In this sketch! have reportedspecifically
on only three. ! havetried,however,to point out the degreeof individuality which characterizes
each species.
Departmentof Zo61ogy
SwarthmoreCollege,Swarthmore,Pennsylvania