OF WING AND ONE HALLUX
P. O. Box 430, Jeffrey City, Wyoming 82310
E-mail: jmorrow@trib.com
This paper appears in
Bulletin of the Texas Ornithological Society
May 2003 36 (1) pages 2 - 5
Photos and Text are copyrights of the Morrows
ABSTRACT- On 6 December 2001 an immature female Harris' Hawk was found surviving in the wild missing half of one wing and the hallux of one foot. Apparent cause of injury was exposure to a high voltage electric current. We hypothesize that Harris' Hawks are able to survive in the wild after sustaining serious injury more readily than other species of raptors because Harris' Hawks are unique among raptors by cooperatively hunting and sharing food among group members.
INTRODUCTION
On 6 December 2001 we observed two adult Harris' Hawks (Parabuteo unicinctus) while trapping and banding Harris' Hawks for a longevity study. The adult hawks were perched on a horizontal section of a utility pole on the side of Highway 44 in Webb County Texas approximately 13 miles (21 km) west of the town of Freer. In the grassy area beside the road opposite the pair of hawks, we deposited a bal-chatri trap containing a pigeon (Berger and Mueller 1959). We parked and watched from our vehicle about 400 meters away. After 45 minutes the adults had not approached the trap so we drove over to retrieve the trap. Upon arriving at the site, we found an immature female Harris' Hawk, as determined by plumage and wing chord (Hamerstrom and Hamerstrom 1978). This hawk had entangled several of its toes in the trap's nooses. While banding this hawk, we discovered that she was missing part of the right wing and the back toe (hallux) of the left foot.
All primaries except primary number 1 on the injured right wing were absent, although she still had an intact alula (Figure 1). All secondary feathers were present on the damaged wing. Scar tissue had formed at the point of loss on the injured wing and P1 was growing in as an adult feather.
 Figure 1: Front of immature female Harris' Hawk showing the missing end of the right wing. Dark feather at point of loss is an emerging adult primary feather. Note intact alula above emerging adult primary feather. The foot near the face of hawk is missing the hallux. |
The entire hallux of the left foot was missing (Figure 2). The talons on the remaining three front digits of the left foot were damaged, were flaky and appeared whitish in color. The point where the hallux had attached to the foot was also completely healed over with scar tissue, indicating that the injuries occurred at least two months previously (Redig, DMV - personal communication).
 Figure 2: Feet of injured Harris' Hawk; normal right foot and left foot missing hallux. Note the left foot has completely healed. |
Except for the noted injuries, this young bird appeared to be in fine health; her weight (940 g) was normal for her age (mean 935.1 g, range 789-1137 g: Hamerstrom and Hamerstrom 1978). Upon release the hawk flew approximately 50 meters in a labored semi-arc to the right and landed about 3 meters high in a mesquite tree (Prosopis juliflora).
DISCUSSION
We presume that the immature Harris' Hawk missing part of its
wing and hallux described above was a victim of a high voltage
electric current. Power line electrocution is a common cause
of Harris' Hawk mortality where power poles are common (Whaley
1986; Bednarz and Hayden 1988). Hunting Harris' Hawks utilize
the highest unobstructed perches available which, in most cases,
are electrified utility poles (Bednarz 1995). Eighty-six percent
of the Harris' Hawks captured and banded during our longevity
study in year 2001 (n=77) were lured down from their perches
on electrified utility poles.
The authors have witnessed a falconer's adult Harris' Hawk and a fledgling peregrine falcon (Falco peregrinus) electrocuted by high voltage electric currents from landing on electrical transformers. In the case of the Harris' Hawk, the explosion from the hawk grounding out the transformer burned a large section of primary and secondary feathers from the Harris' Hawk's right wing and flashed gold colored metals onto several of the talons, toe and leg scales. Months later, the talons turned white and disintegrated but were replaced after a year. The peregrine falcon had the electric current enter the base of the foot, burning tissue up into the pad of the foot. The electricity exited by the base of the tail, leaving a large hole that burned the emerging tail feathers, causing four to fall out within two weeks. The peregrine survived and at 100 days of age started to replace the lost tail feathers with adult tail feathers. The foot injury left a core of dead tissue in the center of the ball of the foot, which later developed a bacterial infection with Escherichia coli and Staphylococcus aureus. In both cases of electric shock, the birds were nursed back to health by the falconer. We suspect that neither of these birds would have survived in the wild because the severity of their injuries would have prevented them from hunting.
Ornithological literature is sparse on reports of birds living with injuries in the wild. One report from the 1920's mentions three birds who had survived injuries that were killed while collecting scientific specimens: 1) a Rough-legged Hawk (Buteo lagopus) that had only one foot, the other was a healed stump; 2) a Great Horned Owl (Bubo virginianus) was skeletonized to reveal shattered and healed ulna and metacarpal bones; 3) a Steller's Jay (Cyanocitta stelleri) surviving at least a year with a wing injury that rendered it virtually flightless (McCabe and McCabe 1928). A more recent report of passerines missing a foot is attributed to metal bird bands (Amata 1999). One published account from Texas describes a Golden-fronted Woodpecker (Melanerpes aurifrons) living with an injured tongue (Husak 1999). In May 2002, we captured and banded an adult female American Robin (Turdus migratorius) in a mist net. The robin's tongue was broken as it became entangled in the mist net while it struggled to avoid attack by an opportunistic Loggerhead Shrike (Lanius ludvicianus). Three months later we recaptured this same banded robin. It had a healed stub of a tongue (approximately 1/2 of it's tongue was missing) but the bird appeared to be healthy and was within 5% of its initial capture weight in spite of its injury.
The authors have captured and banded numerous raptors surviving
with serious injuries in the wild: an adult golden eagle (Aquila
chrysaetos) and an American kestrel (Falco sparverius), each
with one non-functional eye (clouded); an adult redtail (Buteo
jamaicensis) with a broken tarsus that healed in a manner rendering
the foot permanently closed; an adult redtail with a foot hanging
by the flexor tendon of the tarsometatarsus, and an adult prairie
falcon (Falco mexicanus) missing the patagium web of it's wing.
All of these injured raptors were surviving in the wild, as their
injuries had healed. Notably all were adult birds.
Proportionately, we have captured more Harris' Hawks surviving
in the wild with serious injuries than any other species of diurnal
raptors: 5 out of 240 (2.08%) Harris' Hawks - compared to 5 out
of 5733 (0.09%) other raptor species including various accipiters,
buteos, harriers, kites, falcons and eagles. In addition, we
have observed serious injuries of wild Harris' Hawks in both
immature and adult birds, in contrast to other injured raptor
species, which are invariably adult birds. An immature Harris'
Hawk starting its first molt was found with a healed broken wing.
It was incapable of flight but was in excellent health (Morrow
1996). While raptor banding we have observed an adult Harris'
Hawk with a dead eye, an adult Harris' with arthritis so it was
unable to properly stand or fly when temperatures approached
10 degrees Celsius, and an immature male Harris' Hawk with a
broken and healed right leg (personal observations).
We hypothesize that injured Harris' Hawks enhanced survival rate is due to their unique social attributes. Harris' Hawks live in family groups that exhibit cooperative hunting techniques, sharing food with each other in the context of a complex social order (Mader 1975; Ellis, et. al. 1993, and Bednarz 1995). Thus, we hypothesize that injured Harris' Hawks do not necessarily have to catch prey themselves. Their family group members may share food with them, thus helping to prevent severely injured Harris' Hawks from starving.
The two adult Harris' Hawks perched in the vicinity where
the injured immature Harris' Hawk was trapped were most likely
part of the young hawk's family group, probably her parents.
We suggest the possibility that other Harris' Hawks, whether
they are direct family members or socially gregarious unrelated
birds, are helping severely handicapped Harris' survive in the
wild in situations where other raptors would have perished due
to their injuries affecting their ability to capture prey.
ACKNOWLEDGEMENTS
We would like to thank Texas Parks and Wildlife Department for their cooperation. We thank the following persons for helping review the manuscript: Mara McDonald, Tony Head, Sumner Dana, Matthew Vasquez and Jessica Young. We would like to also extend special thanks to Dr. Pat Redig for reviewing the photographs and giving his professional opinion.
LITERATURE CITED
AMATA, J. A. 1999. Foot Losses of Metal Banded Snowy Plovers. Journal of Field Ornithology. 70 (4): 555-557.
BEDNARZ, J. C. AND T. J. HAYDEN. 1988. Harris' Hawk. In Proceedings of the Southwest Raptor Management Symposium and Workshop (R. L. Glinski et al., eds.), National Wildlife Federation, Washington, D. C. p. 71-82.
BEDNARZ, J. C. 1995. Harris' Hawk (Parabuteo unicinctus) In The Birds of North America. The Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington, D. C. No. 146, p. 1, 18.
BERGER, D. D. AND H. C. MUELLER. 1959. The bal-chatri: a trap
for the birds
of prey. Bird Banding 30: 18-26.
ELLIS, D. H., J. C. BEDNARZ, D. G. SMITH, AND S. P. FLEMMING. 1993. Social foraging classes in raptorial birds. Bioscience 43: 14-20.
HAMERSTROM, F. AND F. HAMERSTROM. 1978. External sex characteristics of Harris' Hawks in winter. Raptor Res. 12: 1-14.
HUSAK, M. S. 1999. Observation of survival by a Golden-fronted Woodpecker with an injured tongue. Bulletin Texas Ornithological Society 32 (1):42-44.
MADER, W. J. 1975. Biology of the Harris' Hawk in Southern Arizona. Living Bird. 14: 59-85.
MCCABE, T. T. AND E. B. MCCABE. 1928. Notes on Certain Injured Birds. Condor. 30: 190-191.
MORROW, L. 1996. Harris' Hawks in Chained Brush: Selected notes. Journal of the North American Falconers' Association. Vol. 35: 57.
REDIG, PATRICK T. DVM, PhD; The Raptor Center; College of Veterinary Medicine, Minnesota - personal communication.
WHALEY, W. H. 1986. Population ecology of the Harris' Hawk in Arizona. Raptor Research 20: 1-15.
Author contact information:
Jill Morrow, Ph.D.
Post Office Box 430
Jeffrey City, Wyoming 82310
Phone: 307-544-9009
Email: jmorrow@trib.com
Lance Morrow (same as above)
