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

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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