Corvids in Combat: With a Weapon?

2007·2.1 MB·English

by  Russell P Balda

Short Communications
The Wilson Journal ofOrnithology 1 19(1);100—102, 2007
Corvids in Combat: With a Weapon?
Russell R Baida'
—
ABSTRACT. 1 report on an incident involving a ing the crow for about 10 sec. The crow paid
Steller’s Jay (Cyanocitta stelleri) and an American no heed to the scolding jay as it continued
Crow iCorvus hrachyrhynchos) at a feeding platform. feeding. The Jay on the platform then made
Afterrepeated failures to drive the crow from the plat-
form by scolding, approaching and diving at it, thejay feinting movements toward the crow with its
flew into a bush where it worked vigorously to break bill extended in the direction of the crow. The
off a stick. Having broken off the twig, the jay, with jay cautiously and haltingly approached the
stick in bill, approached the crow and thru.st the point- crow as if to attempt to pull its tail or peck it.
ed stick at it. The crow lunged at the jay which then The jay approached to within 7-10 cm of the
dropped the stick. The crow picked up the stick and crow and appeared to be in the throes of a
aflbeiwrdafhtoerldtihnegjaayn.oTbhjiecstaapnpdearussintog biteinthae wfierastpocna-.sleikoef “fight or flight’’ conflict. The crow then
way during an aggressive action against another bird. turned to face thejay and hopped in its direc-
Received 19 October 2005. Accepted 27July 2006. tion. The jay quickly hopped backwards. The
jay again approached the crow making jab-
bing motions toward it as it continued to scold
On 26 April 2004 at 0655 hrs MST I ob- loudly. Each time the jay approached, the
served the following interaction at a bird feed- crow turned to face it and make a slight lung-
ing station in Flagstaff, Arizona at 2,000 m ing movement toward it. This exchange was
elevation. The feeding platform measured X performed six times. The jay then flew to the
1
m and was within 2.3 m of the window roof of the house directly above the crow and
t1hrough which the ob.servations were made. scolded loudly for 5—6 .sec. The crow contin-
The roofoverhang was 2.2 m. from the center ued to pick seeds from the platform. The jay
of the platform and 2.7 m above it. then swooped down toward the crow just
missing its head and back. The crow jumped
OBSERVATIONS at the jay but no bodily contact occurred. The
A solitary American Crow (Corvii.s hrci- jay again flew onto the roof and called loudly
chyrhyncho.s) was on the platform eating for 5—6 sec. Thejay then dived a second time
seeds. A pair ofSteller’s Jays {Cyanocitta stel- at the crow, again narrowly missing its head
leri) flew into a mountain mahogany {Cerco- and back. The crow continued to feed from
the platform.
carpiis montami.s) shrub that borders the plat-
form. The platform was stocked daily with a The jay then flew into the mountain ma-
variety of seeds commonly eaten by local hogany and vigorously worked with its bill to
break off a twig from a dead branch. The jay
birds. Steller’s Jays regularly feed at the plat-
form, eating and carrying suntlower seeds off succeeded in breaking the twig from the
to cache. Crows only occasionally visit the branch and held it in its bill so that it pointed
platform and are selective about which .seeds forward. The twig was about 10 cm in length,
they pick up in their bills. Thus, they feed and about 0.75 cm in diameter. The twig end
deliberately and slowly, and spend consider- in the jay’s bill was rather blunt; in contrast,
able time on the platform. the other end was pointed. The jay then flew
One of the Steller’s Jays flew to the edge to the feeding platform with the twig in its
of the platform and scolded loudly while fac- bill. Thejay lunged at the crow with the point-
ed end of the twig directed at the body of the
crow. The stick missed the crow by only a few
' Avian Cognition Laboratory, Department of Bio- cm. As the jay approached, the crow lunged
logical Science.s, Northern Arizona University, Flag-
staff, AZ 8601 1, USA; e-mail: quickly at it. The jay flew up with a startled
[email protected] jump backwards, wings extended, and again
100
SHORT COMMUNICATIONS 101
landed on the platform and dropped the twig DISCUSSION
onto the platform. The crow then picked up Tool use by birds has received considerable
the twig in its bill and lunged at the jay with recent attention (Lefebvre et al. 2()02; Emory
the stick pointed at the Jay. The twojays then and Clayton 2()04a, 2()04b). These authors
flew off and the crow followed them with the conclude that tool use by birds is more com-
twig in its bill. mon than previously thought. Lefebvre et al.
Was the twig a weapon? If so, do we define (2002) recently catalogued all reported cases
a weapon as a tool? In animal behavior, usual of tool use by all birds that were published in
definitions of a tool indicate that tools must 68 short note sections of journals as well as
be extensions ofthe body ofthe organism that previous reviews. They found 39 “true” use
are used in a way that allows the organism to of tools (objects detached from the substrate
exploit a resource or situation that could not and held in foot or mouth, McFarland 1982)
be exploited without the object used as a tool. and 86 “borderline” cases (defined as objects
Also, in the case of birds, the tool must be an that are of the substrate such as anvils, wedg-
extension ofthe bill or feet. In the usual sense, es, thorns, and bait) (Hansell 1987, Vauclair
the meaning of “extension of the bill” would 1997). The Common Crow used the most
refer to a feeding apparatus, but bills are also techniques {n = 5) with other members ofthe
used by birds in aggressive interactions. Thus, Corvidae also possessing an impressive rep-
even in the strictest sense this case appears to ertoire of tool uses. For example. Blue Jays
be one of tool use. The twig was a tool that {Cyanocitta cristatci), close relatives of Stell-
was used as a spear or a lance to be thrust at er’s Jays, were observed tearing paper and us-
a potential enemy as an extension of the bill. ing it to rake in food from outside their cages
The purpose for using the twig as a weapon (Jones and Kamil 1973). The New Caledonian
was, ostensibly, to drive the crow from the Crow (Corvus moneduloides) may use the
feeding platform, something thejay had failed most complex tool construction and use be-
to do by scolding, approaching aggressively, havior of any known bird. They have been
and aerial attack. The jay may have viewed observed constructing tools of different types
the crow as a food competitor or as an im- to solve different types offoraging challenges.
pediment blocking its access to the feeder. Useful tools are then carried around during
Whether or not it was the jay’s intention to foraging bouts (Hunt 1996; Chappell and Ka-
use the twig as a weapon when it returned to celnik 2002, 2004).
the feeding platform with it, the twig appeared Tool use by corvids should not be that sur-
to take on this function. The crow’s intentional prising given their large brain (Marzluff and
use of the twig as a weapon is more problem- Angell 2005) and considerable cognitive abil-
atic given that it had previously “lunged” at ities (Emery and Clayton 2004a, 2004b; Em-
the jay without a tool. An alternate explana- ery 2006). Lafebvre et al. (2002) found a pos-
tion might be that the crow picked up the twig itive correlation between true tool use and
out of curiosity and then lunged at thejay be- brain size. Tools used as weapons, however,
cause it was close by. seem less common in birds. Corvids have
The jay broke the twig off the shrub. The been known to drop objects on humans that
twig was of such a length and width that it are threatening nests or offspring (Caffrey
could be easily manipulated by the jay. This 2001), and Boswell (1983) cites a case of a
behavior can be cautiously interpreted as Black Eagle (Aquila verrecnixii) dropping
weapon construction. Having failed to drive sticks on nest intruders.
the crow from the platform using three other Behaviors that are classically associated
methods, thejay used a twig as a lance against with lance or spear use were observed in this
the crow. Possibly, the crow then proceeded bout. The jay first selected and prepared an
to use this newly acquired weapon against the object that could readily be used as a spear,
jay. In this scenario both species were us- and then lunged at the crow with the spear,
ing a tool against each other, first the jay the crow startled the jay which then dropped
against the crow and then the crow against the the twig. The crow retrieved the twig and pos-
jay. sibly used it against r/?cjay. The current report
102 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 119, No. 1, March 2007
may be the first incident of a bird holding an tion ofavian intelligence. Transactionsofthe Phil-
object and using it in a weapon-like fashion osophical Society, Series B 361:23-43.
during an aggressive action against another Emory, N. J. and N. S. Clayton. 2004a. Comparing
the complex cognition ofbirds and primates. Pag-
bird. The incident reported herein adds to our es 3-55 in Comparative vertebrate cognition: are
understanding of how a variety of items in a primates superior to non-primates (L. J. Rogers
bird’s environment may be used to aid in pur- and G. Kaplan, Editors). Kluvser Academic/Ple-
suit ofresources and to gain control over their num, New York, USA.
living space. Emory, N. J. and N. S. Clayton. 2004b. The men-
tality of crows: convergent evolution of intelli-
ACKNOWLEDGMENTS gence in corvids and apes. Science 306:1903-
1907.
These observations were made while the authorwas Hansell. M. 1987. What’s so special about using
supported by NSF Grant 9982883. Russell Benford, tools? New Scientist 1542:54-56.
John Marzluff, and two thoughtful reviewers are Hunt, G. R. 1996. Manufacture and use ofhook-tools
thanked for providing helpful reviews and suggestions by New Caledonian Crows. Nature 379:249-251.
on an earlier draft. Judith Baida helped with, and con- Jones, T. B. and A. C. Kamil. 1973. Tool-making and
firmed, the observations presented herein. tool using in the northern Blue Jay. Science 180:
1076-1078.
LITERATURE CITED
Lelebvre, L., N. Nicolakakis, and D. Boire. 2002.
Boswell, J. 1983. Tool-using and related behaviourin Tools and brains in birds. Behaviour 139:939-
birds: more notes. Avicultural Magazine 94-108. 973.
Callrey, C. 2001. Goal-directed use of objects by Marzluee,j. M. andT. Angell. 2005. Inthecompany
American Crows. Wilson Bulletin 13:114-115. ofcrows and ravens. Yale University Press, New
Chappell, J. and A. Kacelnik. 2002. Tool selectivity Haven, Connecticut, USA.
in a non-primate, the New Caledonian crow. An- McFarland. D. 1982. The Oxford companion to ani-
imal Cognition 5:71-78. mal behavior. Oxford University Press, Oxford,
Chappell, J. and A. Kacelnik. 2004. Selection oftool United Kingdom.
diameter by New Caledonian crows (Corviis mo- Vauclair, j. 1997. Animal cognition: an introduction
neduloides). Animal Cognition 7:121-127. to modern comparative psychology. Harvard Uni-
Emory, N. J. 2006. Cognitive ornithology: the evolu- versity Press, Cambridge, Massachusetts, USA.
The Wilson Journal of Ornithology 1 19(1):102—105, 2007
Turkey Vultures Use Anthropogenic Thermals to Extend Their Daily
Activity Period
James T. Mandel'-'* and Keith L. Bildstein^
—
ABSTRACT. We describe predictable nocturnal mon throughout much of their extensive range. Re-
soaring flight in Turkey Vultures (Cathartes aura) ceived 5 December2005. Accepted3 May 2006.
feeding at a landfill in eastern Pennsylvania. Birds
feeding at the landfill returned to their roosts each
evening by gaining altitude while soaring in thermals
above flared methane vents at the site. Our results Turkey Vultures (Cathartes aura) are en-
highlight behavioral plasticity in this species, which, ergy minimizers like most avian scavengers
in part, may explain why Turkey Vultures are so com- (sensu Schoener 1971, Ruxton and Houston
2002). Individuals at rest maintain low meta-
' James T. Mandel, DepartmentofEcology and Evo- bolic rates for their body mass and reduce
lutionary Biology, Corson Hall. Cornell University, their core body temperature at night in appar-
Ithaca. NY 14850, USA. ent efforts to conserve energy (Heath 1962,
~ Keith L. Bildstein, Hawk Mountain Sanctuary,
Acopian Center for Conservation Learning, 410 Sum- Wasser 1986). Turkey Vultures in flight usu-
mer Valley Rd.. Orwigsburg. PA 17961. USA. ally soar and glide when flying between roosts
CoiTesponding author; e-mail: [email protected] and previously located food, when searching