scholarly journals Calling in the face of danger: Do nestling Red-winged Blackbirds (Agelaius phoeniceus) suppress begging in response to predator playbacks?

The Auk ◽  
2019 ◽  
Vol 137 (1) ◽  
Author(s):  
Ken Yasukawa ◽  
Jessica Sollenberger ◽  
Josie Lindsey-Robbins ◽  
Elizabeth DeBruyn
Keyword(s):  
Nest Predation ◽  
Agelaius Phoeniceus ◽  
American Crow ◽  
Corvus Brachyrhynchos ◽  
Accipiter Cooperii ◽  
Northern Flicker ◽  
The Face ◽  
Nestling Begging ◽  
Colaptes Auratus ◽  
Nest Predator

Abstract Nest predation is the most frequent cause of nest failure in birds such as the Red-winged Blackbird (Agelaius phoeniceus) that nest on or near the substrate. Nestlings should therefore exhibit adaptations to reduce the risk of nest predation. We tested the nestling antipredator hypothesis by examining the begging responses of Red-winged Blackbird nestlings to vocalizations of (1) an important nest predator (American Crow, Corvus brachyrhynchos), (2) a predator that rarely preys on nestlings (Cooper’s Hawk, Accipiter cooperii), and (3) a nonpredator (Northern Flicker, Colaptes auratus). We performed playbacks with (1) both parents present at the nest, (2) male at the nest, and (3) neither parent present. Following playback, we measured duration of nestling begging after the parent departed (begging persistence), bouts of otherwise normal begging when no parent was present (parent-absent begging), and calling without postural components of begging (nonpostural begging). When the male or both parents were present during playback, adults responded with alarm calls and nestlings significantly reduced parent-absent begging following American Crow and Cooper’s Hawk playbacks. Nonpostural begging was significantly reduced following Cooper’s Hawk playback, but there were no significant differences in the other begging variables. When neither parent was present, we found no significant differences in nonpostural begging in response to the 3 playback types, but parent-absent begging was significantly reduced following American Crow and Cooper’s Hawk playbacks when compared to Northern Flicker playbacks. These results show that nestlings suppress their vocal begging in response to calls of predators including Cooper’s Hawks even though they are not common nest predators.

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 Nest-predator prevalence along a mountain birch - alpine tundra ecotone

2011 ◽  
Vol 38 (6) ◽  
pp. 525
Author(s):  
Åshild Ø. Pedersen ◽  
Lasse Asmyhr ◽  
Hans Christian Pedersen ◽  
Nina E. Eide
Keyword(s):  
Nest Predation ◽  
Alpine Tundra ◽  
Mountain Birch ◽  
Pine Marten ◽  
Willow Ptarmigan ◽  
Generalist Species ◽  
Management Actions ◽  
Nest Predator ◽  
Predation Rates ◽  
Birch Forests

Context Nest predation is a major factor influencing life history and population dynamics of ground-nesting birds. The transitions between the northern boreal mountain birch forests and the low-alpine tundra are important habitats for the willow ptarmigan, Lagopus lagopus (Linnaeus, 1758). During the past decades, these landscapes have been extensively developed with cabin resorts in southern Norway, which has led to an increased number of roads and foot paths in relatively undisturbed habitats. Aims The aim of the present study was to investigate relative nest-predation rates in elevation gradients (ecotones) spanning from northern boreal mountain birch forests to low-alpine tundra in three locations with contrasting willow ptarmigan densities. Methods We conducted an artificial nest study by using baited track boards (n = 108). Track boards were placed along transects (200 m) in the following three habitat types: birch forest, edge habitat and low-alpine tundra. Predator prevalence was analysed in relation to study-design variables (location, habitat, study period) and the load of human infrastructure (i.e. distance to foot paths and roads), using generalised linear mixed-effect models assuming binomial distribution for the response variable. Key results Prevalence of avian predators was consistently high (range 38.2–85.3%), in contrast to much lower prevalence of mammalian predators (range 2.8–22.9%). Raven (Corvus corax) was the dominant nest predator, followed by hooded crow (C. cornix) and pine marten (Martes martes). Location, as contrasted by differences in willow ptarmigan density, was not significantly related to total relative predation rates. Species-specific predator prevalence was habitat specific and related to human infrastructure, but with opposite relative predation patterns between pine marten and raven. Hooded crow predation was similar across the ecotone and not related to human infrastructure. Conclusions Predator prevalence was habitat specific and affected by human infrastructure (distance to human foot paths). Our study confirmed that human activity might alter the predation rates by generalist species in these low-alpine environments. Implications We recommend that attractive willow ptarmigan habitat should be avoided when planning human infrastructure in alpine ecosystems. To reduce predation pressure in this ecosystem, it appears that generalist predators should be considered for management actions. Further research is needed to explain the underlying mechanism driving expansion of generalist species into alpine habitats. Such knowledge is also important in developing alternative management actions with focus other than predator control.

New and little-known species of feather mites (Acari: Analgoidea: Pteronyssidae) from birds in North America

2006 ◽  
Vol 138 (2) ◽  
pp. 165-188 ◽  
Author(s):  
Sergei V. Mironov ◽  
Terry D. Galloway
Keyword(s):  
North America ◽  
Tree Swallow ◽  
Feather Mites ◽  
New Host ◽  
Cliff Swallow ◽  
Northern Flicker ◽  
Picoides Pubescens ◽  
Colaptes Auratus ◽  
First Time ◽  
New Host Records

AbstractIn this paper, we review the pteronyssid feather mites of the genera Pteronyssus Robin, Scutulanyssus Mironov, and Stenopteronyssus Faccini and Atyeo found in the course of an investigation into ectoparasites of birds in Canada. Five new species of feather mites are described: Pteronyssus sphyrapicinussp. nov. from the Yellow-bellied Sapsucker, Sphyrapicus varius (L.); Stenopteronyssus proctoraesp. nov. from the Northern Flicker, Colaptes auratus (L.); Scutulanyssus progneisp. nov. and Scutulanyssus subissp. nov. from the Purple Martin, Progne subis (L.); and Scutulanyssus petrochelidonissp. nov. from the Cliff Swallow, Petrochelidon pyrrhonota (Vieillot). New host records are provided for Pteronyssus picoides Černy and Schumilo from the Downy Woodpecker, Picoides pubescens (L.), and for Scutulanyssus obscurus (Berlese) from the Cliff Swallow; Pteronyssus brevipes Berlese and Scutulanyssus hirundicolus Mironov are formally recorded in North America for the first time; and Pteronyssus centurus McDaniel and Price is reported for the first time in Canada, from Lewis' Woodpecker, Melanerpes lewis (Gray). Scutulanyssus tyrrelli (Canestrini) is reported for the first time in Manitoba from the Tree Swallow, Tachycineta bicolor (Vieillot). Keys are provided for all species of Pteronyssus and Scutulanyssus found in North America.

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