Causes and consequences of expanding American Crow populations

2001 ◽  
pp. 331-363 ◽  
Author(s):  
John M. Marzluff ◽  
Kevin J. McGowan ◽  
Roarke Donnelly ◽  
Richard L. Knight
Keyword(s):  
American Crow

The American Crow

1895 ◽  
Vol 40 (1030supp) ◽  
pp. 16467-16468
Keyword(s):  
American Crow

American Crow (Corvus brachyrhynchos)

2002 ◽  
Author(s):  
N. A. Verbeek ◽  
C. Caffrey
Keyword(s):  
American Crow ◽  
Corvus Brachyrhynchos

WEST NILE VIRUS DEVASTATES AN AMERICAN CROW POPULATION

The Condor ◽  
10.1650/7646 ◽  
2005 ◽  
Vol 107 (1) ◽  
pp. 128 ◽  
Author(s):  
Carolee Caffrey ◽  
Shauna C. R. Smith ◽  
Tiffany J. Weston
Keyword(s):  
West Nile Virus ◽  
West Nile ◽  
American Crow

scholarly journals Occurrence and variability of tactile interactions between wild American crows and dead conspecifics

2018 ◽  
Vol 373 (1754) ◽  
pp. 20170259 ◽  
Author(s):  
Kaeli Swift ◽  
John M. Marzluff
Keyword(s):  
Information Acquisition ◽  
Alarm Call ◽  
Controlled Experiments ◽  
Theme Issue ◽  
Risky Behaviour ◽  
American Crow ◽  
Alarm Calling ◽  
Adaptive Value ◽  
American Crows ◽  
The Dead

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’.

scholarly journals West Nile Virus Devastates an American Crow Population

The Condor ◽  
2005 ◽  
Vol 107 (1) ◽  
pp. 128-132 ◽  
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.

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

The Condor ◽  
2006 ◽  
Vol 108 (3) ◽  
pp. 518-529 ◽  
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.

scholarly journals Morphological Description of American Crow, Corvus brachyrhynchos, Populations in Southern Quebec

2009 ◽  
Vol 123 (2) ◽  
pp. 133 ◽  
Author(s):  
Antoinette Ludwig ◽  
Michel Begras-Poulin ◽  
Stephane Lair ◽  
Denise Belanger
Keyword(s):  
North America ◽  
Function Analysis ◽  
Age Groups ◽  
Morphological Description ◽  
American Crow ◽  
Age And Gender ◽  
Adult Age ◽  
Measurement Protocol ◽  
Public Health Authorities ◽  
And Gender

The American Crow has always been a much scrutinized bird in North America but, since the emergence of West Nile Virus (WNV) in North America in 1999, public health authorities’ attention to it has been raised another notch. In Québec, like everywhere else in North America, part of the WNV surveillance programme was based on detection of WNV mortality in crow populations. During the summer of the 2005 surveillance season, we followed an age and gender determination protocol, as well as a morphological measurement protocol, on dead crows sent in for WNV status determination, to improve our knowledge of the crow population in Québec. Statistical analysis of the measurements revealed that age and gender were important factors in the morphological characterisation of the American Crow. Bill depth and head-to-bill length appeared as the most important morphological variables for gender prediction through a discriminant function analysis. We also realized that, in adult age groups, our WNV positive carcasses had lower mean weights than carcasses that tested negative for WNV, in adult age groups.Depuis toujours, la corneille d’Amérique est un oiseau très étudié, mais, depuis l’apparition du virus du Nil occidental (VNO) en Amérique du Nord en 1999, l’attention des autorités en santé publique sur cet oiseau a encore augmenté. Au Québec, comme ailleurs en Amérique du Nord, une part importante du programme de surveillance pour la détection du VNO a été basée sur la détection des mortalités liées au VNO dans les populations de corneilles. Pour améliorer notre connaissance de cette espèce au Québec, nous avons mis à profit la récolte des carcasses au cours de l’été 2005 dans le cadre du programme de surveillance en instaurant un protocole de détermination de l’âge, du genre ainsi qu’une prise des mesures morphologiques sur ces mêmes carcasses. L’analyse statistique des résultats a montré qu’à la fois l’âge et le genre étaient des facteurs importants dans la caractérisation morphologique de la corneille d’Amérique. À l’aide de l’analyse discriminante, il est apparu que la profondeur du bec ainsi que la distance tête-bec étaient les mesures les plus importantes pour prédire le genre de l’oiseau. Nos analyses nous ont également permis d’observer que, dans les groupes d’oiseaux adultes, les carcasses positives pour le VNO étaient en moyenne moins lourdes que les carcasses négatives.

Age Determination in the American Crow

The Condor ◽  
1936 ◽  
Vol 38 (3) ◽  
pp. 99-102 ◽  
Author(s):  
J. T. Emlen,
Keyword(s):  
Age Determination ◽  
American Crow
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