Vol. 55]
1938
]
PETTINGILL,
Intelligent
Behavior
ofClapper
Rail
INTELLIGENT
BEHAVIOR
IN
THE
BY OLIN SEWALL PETTINGILL,
CLAPPER
411
RAIL
JR.
Plates14-15
OF twenty nestsof the Northern ClapperRail (Railuslongirostris
crepitans)foundat CobbIsland,Virginia,June24-26, 1933,onewasselectedfor
a studyof the nestingbirds. This particularnestwaslocatedat leasttwenty
feet from a salt marsh in a thick growth of sedgesborderingthe island's
broad sandbeach. So thick and rank was the surroundingvegetationand
so greatly did it slant in onedirectionover the nest that the nest was concealedfrom view evenfrom a positiondirectly aboveit. Within four feet
of the nest I placeda burlap blind and cut away the sedgeson one sideof
the nest to permit observationthrough a small openingin the side of the
blind facingthe nest.
On July 2, I enteredmy blind while the bird was absentfrom its nest.
After a ten-minutewait I suddenlynoticeda few sedgesmovingbehindthe
nest,then the headof the rail peeringthroughthem. It waspantingnoticeably, and its lower mandible was loweredwith each exhalationand closed
with eachinhalation. Slowly,cautiously,it steppedoverthe eggs,covering
them and adjustingthem for brooding. For fully five minutesthe rail (sex
undetermlned)incubated,remainingquiet exceptfor its heavy breathing.
At the end of that time someslightmovementon my part within the blind
frightenedthe bird, and it departedhurriedly. In a few minutesit returned, became suspiciousof my presence,and hastened away again.
Severaltimes within the next fifteenminutesit appearedand disappeared;
finallyit becameusedto soundsemanatingfromtheblindandstayedcalmly
on the nest. But the bird was not accustomedto the sharpsoundthat my
tripod causedwhen, slidingdownthe sideof the blind againstwhichit was
precariouslyleaning, it struck the ground. The rail, startled, was out of
sightin an instant. As it jumpedfrom the nestit accidentallypushedout
an eggwith its foot. When it returnedand beganto incubate,it immediately saw this eggrestingon the groundeight inchesaway from the edgeof
the nest. After gazingat the eggsteadilyfor nearlythreeminutes,it slowly
reachedout with its bill and with the tips of the mandiblespokedgentlyat
the surfaceandturnedit overa numberof times. Then, quite unexpectedly,
it graspedthe eggcrosswise
at the widestpart, lifted it up, and broughtit
back to the nestbesidethe other eggs.
Wishingto securephotographsof this impressive
behavior,I flushedthe
rall from the nest,set up my camerain the blind with the lensprojecting
throughthe holetoward the nest, and placedthe eggin the sameposition
it had occupiedwhen dislodged. The bird returned almostas soonas I was
412
P•'nrG•LL,
Intelligent
Behavior
ofClapper
Rail
[Auk
[Jllly
prepared. It repeatedthe performancewith little hesitationand with little
pokingat the egg'ssurface. In fact, the eggwas put back into the nest so
quicklythat I securedbut onephotograph,that of the bird startingto lift
the egg. AgainI flushedthe bird, removedthe eggas before,and againI
securedan exposure,that of the bird lifting the egg. Eight times more I
flushedthe bird and removedthe egg,and eachtime the bird returnedthe
egg!
My seriesof photographsof this egg-returningact was now complete
(seePlates14-15). I then experimented
furtherwith the rail, to the extent
of placingthe egga foot away from the nest,a distancesufficientto make
the bird leave the nest in orderto bring it back, yet easilyin line with the
bird's vision. This time the rail, after returning, steppedfrom the nest,
pickedup the egg,turnedaround,put the eggbesidethe others,and settled
on the nest.
The day followingthis experiencewith the ClapperRail, Cobb Island
wasfloodedby an almostunprecedented
high tide. Althoughthis particular
nest was locatedon the edge of the dry beach, it was low enoughto be
washedaway, as were all the other nestsin the vicinity. This disaster,
therefore,terminatedfurther experimentswith the nestingbirds, but it was
not without somereward. It brought me an experiencewith a brood of
ClapperRails that would otherwiseneverhave happened.
During the high tide I stayed in Captain GeorgeW. Cobb's house.
This was ideally locatedon the southernend of the islandand affordedan
extensiveview of a large portion of the island to the north. Placedback
from the beachbehinda ridgeof sanddunes,the houserestedon pilessome
sevenor eight feet above the salt marsh that beganbelow the houseand
stretched
far to the northwestward
and westward.
Protected
thus from
high water and the surf, it was a safeplaceundersuchconditions.
The tide that occurredon this day completelyinundatedthe marshand
cameto within one foot of the floor of Captain Cobb'shouse. While this
tide wasrising,I countedsix pairsof adult ClapperRails and their broods
swimmingabovethe marsh,striving desperatelyto reachthe dunes,which
were the only parts of the islandstill abovewater. But the northeastwind
was driving them to the southwardand made their attempts at reaching
shoreseeminglyuseless.Two broodsultimately cameashore;three others
weresweptpast the southernpoint of the islandto deathin the roughocean.
The sixth broodwas blowndirectlytowardthe house. My attentionwas
naturallydirectedtowardthewelfareof the familygroup.
As this broodrapidly drifted toward the house,I was able to discern
sevenyoungbirds,all of whichwereaboutof an equalage. I judgedthat
they were two weeksold. They were barelyable to keeptheir headsand
backsabovewater. Waves,freshlywhippedup by the wind, continually
Vol. 551
1938
J
PETTINGILL,
Intelligent
Beha•or
ofClapper
Rail
413
washedover them, soakingtheir downand makingthem lessbuoyanteach
time. They seemedabout to succumband were making no attemptsto
swim. The two parentbirds,however,werelargeenoughandstrongenough
to keeptheirheadsabovethe wavesbreakingoverthemandwereswimming
anxiouslyabouttheir young. Every nowandthenthe old birdswouldhead
towardthe dunesbut, seeingthat their offspringwerenot following,would
turn back and continueencirclingthem. In a very short time the rail
family wasfloatingalongpastthe house. CaptainCobband I soonrescued
the sevenyoungbirdsby plunginginto the water and gatheringthem up
and bringingthem to the porch. We placed them in a carton two feet
squareand closedthe four flaps. As a resultof our interferencethe parent
birdsmadeaway to the sanddunescallingloudly. Darknessset in before
the tide went out, and the youngrails passedthe night in the cartonon the
porch. While their down was soakedand they seemedutterly exhausted,
scarcelymovingwhen we touchedthem, they were old enoughand the
temperatureof the surrounding
air waswarmenoughto permittheirsurvival
withoutbrooding.
At sunrisethe next morningwe were awakenedby the calling of the
youngbirdsin the cartonand the noisyclatter of the parent birdswhich
werefranticallysearchingabout beneaththe house. Lookingthroughthe
windowon to the porch,we saw oneparent bird fly to the porchfloor and
walk directly to the carton. ,Several times it walked around the box,
strikingat the sidesasit did so. It jumpednimblyto the top andpickedup
the looseendof oneof the flapswith its bill, lifted it up, andflippedit over
backward. This alloweda smallopeningbetweenthe two underlyingflaps,
throughwhich it thrust its head. Immediately,it made a quick thrust at
oneof the youngbirds. To us it appearedas if the old bird had actually
graspedone of the young birds, but the young bird was too large to be
drawn throughthe opening. Consequentlythe adult let go and remained
on the box, continuingits clatter. When we went out on the porchto open
the box, the old bird flew to the marshgrassbelow. The youngbirdswere
strongenoughto hop out hurriedly,jump downfrom the porch,and follow
their parent away. We last saw the youngbirdsgoingthroughthe marsh
grass,respondingto the coaxingsoundsof their parent.
This episode,I found,wasnot newto CaptainCobb. During a hightide
of the previoussummerhe had rescueda brood of young rails scarcelya
week old. He had placedthem in an open box on his small hand-cart and
left them on oneof the dunesduringthe storm. The top of the box was
about three feet from the ground. Going back to his house,he observed
that in a shortwhilethe criesfromwithin the boxattractedthe parentbirds
to the vicinity. One adult, the bolderof the two, cameup and circledthe
cart a numberof times,walkedunderneathit, and then hoppedfirst to the
414
P•a•rxN(•ILL,
Intelligent
Behavior
ofClapper
Rail
['Auk
[July
edgeof the cart, then to the top edgeof the box with a young bird held
firmly betweenits mandibles. It jumpedto the groundwith the burdenand
put it down, and both disappearedinto the grass. Wishing to keep the
remainingbrood for a group of ornithologistswho were comingthe next
day, Captain Cobbremovedthe birdsto a largebox restingon the ground.
The open top of this box was at least three feet from the ground. To his
surprisethe samething happened. An adult bird returned,found its way
directlyto the top of the box withoutcirclingit, and removedanotheryoung
bird. Captain Cobb finally coveredover the top. Toward night an old
bird was back again and was standingand movingnervouslyabout on the
coversof the box. The youngbirdsthat had beenpreviouslyremovedwere
nowhereto be seen,havingpresumablyremainedin the grasswith the other
parent.
To my mind these acts of egg-returningand young-carryingshowed
intelligentbehavior. I grant that they had as their basisthe instinctive,
cyclicaldrives to incubate all the eggsand to solaceby broodingall the
complainingyoung. Yet, in submitting to the driving force of instinet,
they showedat least a coatingof intelligentbehaviorby readily adapting
themselvesto eertaln circumstances
that were not a part of their ordinary
reproductiveroutine.
Let me analyzetheseeasesmore fully, to showin what ways intelligent
behaviorwas evident. The eggwas out of •he nest and obviouslycouldnot
be coveredwith the others. It was downamongthe deadgrasses
over the
edgeof the nest; it couldnot be easilyrolled back over theseentanglements
with the bill; it could not even be reachedfrom the nest with the bill, in the
last instance. Similarly the youngwere separatedfrom the adult by the
sidesof the earton;they couldnot be coaxedout. Wherewith mostspecies
of birds the eggwould have remainedin situ and the adult might or might
not haveforsakenits ownnestto incubatethe dislodgedegg,andwherewith
most speciesof birds the youngwould have remainedin the earton until
death by exposureor until removal by some animate means, the rail,
throughthe mediumof its long and strongbill, founda way of overcoming
the conditions,whichit instinctivelyrealizedwerewrong;and it foundthis
way by its capacityto adjustitself to a new situation. Thus by lifting the
objectsbodily it was able to changethe conditionsto suit its instinctive
mental pattern.
Let me further analyzetheseeasesfor evidenceof intelligentbehavior.
The secondtime and the timesthereafterthat the rail returnedthe eggto
the nest, it actedwith little hesitation. It did not fumbleat the eggnor
moveit about,but pickedit up andreturnedit deliberately. It evengrasped
the eggdeliberatelywhenit left the nestto bring it back. The adult rail
that Captain Cobb observedreturned to the taller box the secondtime,
THE Auld, VOL. 55
PLATE 14
CLAPPER RAIL APPROACHING ITS NEST
AN EGG DISPLACED OUTSIDE THE NEST
TnE At•, Von. 55
PLATE 15
CLAPPERI•AIL SEIZING DISPLACEDEGG
DISPLACEDEGG TO IVEST
Vol. 55]
1938
J
PETTINGILL,
Intelligent
Behavior
ofClapper
Rail
415
flew directly to the top, went in, and did not bother to circle it as it had
circledthe boxon the hand-cart. Theserailslearnedby experience.Where
they hesitatedthe first time, they acted more deliberatelythe secondtime.
Had their actsbeeninstinctive,they wouldnot have learnedby experience.
But they did profit by experience,and their behaviorwas, to my mind,
intelligent.
Departmentof Zoology,CarletonCollege
Northfield,Minnesota