Cryptic and extensive hybridization between ancient lineages of American crows

Observations of some mammals and birds touching their dead provoke questions about the motivation and adaptive value of this potentially risky behaviour. Here, we use controlled experiments to determine if tactile interactions are characteristic of wild American crow responses to dead crows, and what the prevalence and nature of tactile interactions suggests about their motivations. In Experiment 1, we test if food or information acquisition motivates contact by presenting crows with taxidermy-prepared dead crows, and two species crows are known to scavenge: dead pigeons and dead squirrels. In Experiment 2, we test if territoriality motivates tactile interactions by presenting crows with taxidermy crows prepared to look either dead or upright and life-like. In Experiment 1, we find that crows are significantly less likely to make contact but more likely to alarm call and recruit other birds in response to dead crows than to dead pigeons and squirrels. In addition, we find that aggressive and sexual encounters with dead crows are seasonally biased. These findings are inconsistent with feeding or information acquisition-based motivation. In Experiment 2, we find that crows rarely dive-bomb and more often alarm call and recruit other crows to dead than to life-like crows, behaviours inconsistent with responses given to live intruders. Consistent with a danger response hypothesis, our results show that alarm calling and neighbour recruitment occur more frequently in response to dead crows than other stimuli, and that touching dead crows is atypical. Occasional contacts, which take a variety of aggressive and sexual forms, may result from an inability to mediate conflicting stimuli. This article is part of the theme issue ‘Evolutionary thanatology: impacts of the dead on the living in humans and other animals’.

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West Nile Virus Devastates an American Crow Population

The Condor ◽

10.1093/condor/107.1.128 ◽

2005 ◽

Vol 107 (1) ◽

pp. 128-132 ◽

Cited By ~ 3

Author(s):

Carolee Caffrey ◽

Shauna C. R. Smith ◽

Tiffany J. Weston

Keyword(s):

West Nile Virus ◽

North America ◽

Late Summer ◽

Total Loss ◽

West Nile ◽

American Crow ◽

Corvus Brachyrhynchos ◽

American Crows

Abstract In its spread west across North America in 2002, West Nile virus (WNV) reached a population of marked American Crows (Corvus brachyrhynchos) in Stillwater, Oklahoma, in late summer. Within two months, 46 of 120 individuals were missing or known to be dead, 39 of which (33% of the population) are estimated to have died for WNV-related reasons. In 2003, 56 of 78 marked crows disappeared or were found dead between June and November. Five of the 28 juvenile losses were possibly unrelated to WNV, thus we estimate that 65% of our population died because of this pathogen in 2003. The total loss of 72% of population members, including 82% of juveniles, in a single year of WNV exposure raises concern for precipitous declines in American Crow populations in coming years. El Virus del Nilo Occidental Devasta una Población de Corvus brachyrhynchos Resumen. En su diseminación hacia el oeste de América del Norte durante 2002, el Virus del Nilo Occidental alcanzó a fines del verano una población marcada de Corvus brachyrhynchos en Stillwater, Oklahoma. En menos de dos meses, 46 de los 120 individuos registrados desaparecieron o murieron, 39 de los cuales (33% de la población) estimamos que murieron por causas relacionadas con el virus. En 2003, 56 de los 78 cuervos marcados desaparecieron o fueron encontrados muertos entre junio y noviembre. Cinco de las 28 pérdidas de juveniles posiblemente no estuvieron relacionadas con el virus, por lo que estimamos que el 65% de nuestra población murió a causa de este patógeno en 2003. La pérdida total del 72% de los miembros de la población, incluyendo el 82% de los juveniles, en un solo año de exposición al virus plantea preocupaciones en cuanto a la posibilidad de una disminución precipitada de las poblaciones de C. brachyrhynchos en los próximos años.

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The Inflected Alarm Caw of the American Crow: Differences in Acoustic Structure Among Individuals and Sexes

The Condor ◽

10.1093/condor/108.3.518 ◽

2006 ◽

Vol 108 (3) ◽

pp. 518-529 ◽

Cited By ~ 1

Author(s):

Jessica L. Yorzinski ◽

Sandra L. Vehrencamp ◽

Kevin J. McGowan ◽

Anne B. Clark

Keyword(s):

Individual Differences ◽

Function Analysis ◽

Acoustic Measurements ◽

American Crow ◽

Acoustic Structure ◽

Corvus Brachyrhynchos ◽

Call Structure ◽

American Crows ◽

The Status ◽

Family Membership

Abstract Previous research on individual differences in the acoustic structure of vocalizations and vocal recognition has largely focused on the contexts of parent-offspring interactions, territory defense, sexual interactions, and group cohesion. In contrast, few studies have examined individual differences in the acoustic structure of mobbing and alarm calls. The purpose of this study was to explore individual differences in the acoustic structure of the inflected alarm caw of the American Crow (Corvus brachyrhynchos). The alarm caws of 15 wild, marked individuals were recorded and 25 acoustic measurements were made automatically using customized software. A stepwise discriminant function analysis showed that 20 of the 25 variables were important in discriminating among individuals, with 65% classification success. We used factor analysis to reduce the large number of variables to a set of seven meaningful call features. All of these features differed among individuals, suggesting that American Crows have the potential to discriminate among individual birds on the basis of call structure alone. Five of the features differed between the sexes, with call frequency being the most significant. One clearly subordinate male clustered with the females, raising the possibility that social status partially determines the sex-based differences. Encoding of individual identity in alarm contexts may be adaptive if receiver vigilance and approach urgency depend on the status, reliability, or family membership of the alarm signaler.

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Experimental Inoculation of European Starlings (Sturnus vulgaris) and American Crows (Corvus brachyrhynchos) with Mycobacterium bovis

Avian Diseases ◽

10.2307/1592917 ◽

2001 ◽

Vol 45 (3) ◽

pp. 709 ◽

Cited By ~ 15

Author(s):

K. L. Butler ◽

S. D. Fitzgerald ◽

D. E. Berry ◽

S. V. Church ◽

W. M. Reed ◽

...

Keyword(s):

Mycobacterium Bovis ◽

Sturnus Vulgaris ◽

European Starlings ◽

Corvus Brachyrhynchos ◽

American Crows ◽

Experimental Inoculation

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Evaluation of lasers to disperse American crows, Corvus brachyrhynchos, from urban night roosts

International Journal of Pest Management ◽

10.1080/09670870210151689 ◽

2002 ◽

Vol 48 (4) ◽

pp. 327-331 ◽

Cited By ~ 10

Author(s):

W. P. Gorenzel ◽

B. F. Blackwell ◽

G. D. Simmons ◽

T. P. Salmon ◽

R. A. Dolbeer

Keyword(s):

Corvus Brachyrhynchos ◽

American Crows

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West Nile Virus Activity in a Winter Roost of American Crows (Corvus brachyrhynchos): Is Bird-To-Bird Transmission Important in Persistence and Amplification?

Journal of Medical Entomology ◽

10.1093/jme/tjv040 ◽

2015 ◽

Vol 52 (4) ◽

pp. 683-692 ◽

Cited By ~ 18

Author(s):

M. G. Hinton ◽

W. K. Reisen ◽

S. S. Wheeler ◽

A. K. Townsend

Keyword(s):

West Nile Virus ◽

West Nile ◽

Corvus Brachyrhynchos ◽

Virus Activity ◽

American Crows

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Increases in apoptosis and declines in Bcl-XL protein characterise testicular regression in American crows (Corvus brachyrhynchos)

Reproduction Fertility and Development ◽

10.1071/rd06079 ◽

2007 ◽

Vol 19 (3) ◽

pp. 461 ◽

Cited By ~ 16

Author(s):

Luwanda K. Jenkins ◽

Wallace L. Ross ◽

Kelly A. Young

Keyword(s):

Breeding Season ◽

Sertoli Cells ◽

Cell Loss ◽

Terminal Deoxynucleotidyl Transferase ◽

Rapid Reduction ◽

Corvus Brachyrhynchos ◽

Testicular Regression ◽

American Crows ◽

Low Levels ◽

Testis Mass

The present study investigated the cellular changes observed during testicular regression in American crows. Testes from adults caught during the early (March), progressing (April), peak (early May), transitional (late May), and post- (June) breeding season were examined. Apoptosis was assessed by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) and Bcl-XL protein immunolabelling. Testis mass increased two-fold from March to early May (P < 0.05), then declined 19-fold by June (P < 0.001) without corresponding changes in body mass (P > 0.05). Testicular activity, evaluated using a spermatogenic index, increased nearly two-fold from March to early May and declined nine-fold in June (P < 0.001). Seminiferous tubule diameter declined four-fold in June compared with earlier months (P < 0.001). In all testes, TUNEL-positive germ cells were detected at low levels, with the highest levels observed in late May (P < 0.001). In contrast, TUNEL-positive Sertoli cells were maintained at low levels in March–April and increased nine-fold in early May (P < 0.001). The Bcl-XL immunostaining was detected in Sertoli cells in March–early May; however, staining was most intense in March–April and substantially weaker by early May. These data suggest that the seasonal rise in testicular competence occurs slowly in American crows; however, testis function is terminated rapidly after the breeding season. Furthermore, it is likely that Sertoli cell apoptosis followed by massive germ cell loss is responsible for the rapid reduction in testis mass.

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