Nest Predation and Cowbird Parasitism Create a Demographic Sink in Wetland-Breeding Song Sparrows

The Condor ◽  
1997 ◽  
Vol 99 (3) ◽  
pp. 622-633 ◽  
Author(s):  
Christopher M. Rogers ◽  
Mary J. Taitt ◽  
Gwen Jongejan
Keyword(s):  
Nest Predation ◽  
Song Sparrows ◽  
Cowbird Parasitism

scholarly journals First Evidence of Conspecific Brood Parasitism and Egg Ejection in Song Sparrows, With Comments on Methods Sufficient to Document These

The Condor ◽  
2006 ◽  
Vol 108 (2) ◽  
pp. 452-458
Author(s):  
Quresh S. Latif ◽  
J. Letitia Grenier ◽  
Sacha K. Heath ◽  
Grant Ballard ◽  
Mark E. Hauber
Keyword(s):  
Genetic Analysis ◽  
Brood Parasitism ◽  
Nest Predation ◽  
Molothrus Ater ◽  
Separate Study ◽  
Conspecific Brood Parasitism ◽  
Egg Ejection ◽  
Song Sparrows ◽  
Cowbird Parasitism ◽  
Egg Marking

Abstract Conspecific brood parasitism occurs in many songbird species but has not been reported in Song Sparrows (Melospiza melodia). In three separate study areas where breeding Song Sparrows experience heavy nest predation pressure and Brown-headed Cowbird (Molothrus ater) parasitism, we observed six instances in which newly laid eggs were attributable to female Song Sparrows other than the nest owners. We also recorded the ejection of a sparrow egg from each of two videotaped nests. In a fourth study area without cowbird parasitism, genetic analysis of parentage revealed no conspecific brood parasitism. Given that egg ejection can accompany conspecific parasitism in Song Sparrows, we suggest that daily nest checks are insufficient to document the frequency of this tactic in some species in the absence of egg marking, videotaping, or genetic analyses. Since standard nest monitoring techniques may fail to detect conspecific brood parasitism, this behavior could be more prevalent than currently thought.

scholarly journals Conflicting Temporal Changes in the Frequency and Intensity of Cowbird Parasitism on Four Common Hosts in Ontario over 130 Years

The Condor ◽  
2006 ◽  
Vol 108 (1) ◽  
pp. 238-242
Author(s):  
Celia M. McLaren ◽  
Todd J. Underwood ◽  
Spencer G. Sealy
Keyword(s):  
Molothrus Ater ◽  
Past Century ◽  
Cardinalis Cardinalis ◽  
Vireo Olivaceus ◽  
Song Sparrows ◽  
Limited Support ◽  
Before And After ◽  
Cowbird Parasitism ◽  
Northern Cardinals ◽  
Spizella Passerina

AbstractWe tested the hypothesis proposed by Friedmann (1963) that multiple parasitism (nests with more than one parasitic egg) by Brown-headed Cowbirds (Molothrus ater) is a recent phenomenon associated with increased densities of cowbirds. We used Ontario Nest Records Scheme data to quantify frequencies of parasitism and multiple parasitism on four common host species over the last 130 years. Frequency of multiple parasitism significantly increased over all decades only in Chipping Sparrows (Spizella passerina). We also analyzed data separately before and after 1970 because at about this time cowbird abundance began to stabilize and then decline. Pre-1970, multiple parasitism significantly increased on Chipping Sparrows and Song Sparrows (Melospiza melodia), but neither had significant trends post-1970. There were no significant trends in multiple parasitism on Red-eyed Vireos (Vireo olivaceus) or Northern Cardinals (Cardinalis cardinalis). For all time periods analyzed, there were no significant trends in overall frequency of parasitism on any species. Our results provide limited support for the hypothesis that temporal variation in parasitism patterns has followed changes in cowbird density over the past century.

scholarly journals Reassessing the Cowbird Threat

The Auk ◽  
2007 ◽  
Vol 124 (1) ◽  
pp. 210-223
Author(s):  
Liana Zanette ◽  
Daniel T. Haydon ◽  
James N. M. Smith ◽  
Mary J. Taitt ◽  
Michael Clinchy
Keyword(s):  
Nest Predation ◽  
Molothrus Ater ◽  
Nest Survival ◽  
Survival Rates ◽  
Song Sparrows ◽  
Parasitism Rates ◽  
Common Technique ◽  
Stochastic Simulation Model ◽  
The Common ◽  
Egg Removal

Abstract The demographic significance of parasitism by Brown-headed Cowbirds (Molothrus ater; hereafter “cowbirds”) has been debated for years, because manipulative studies are few and mathematical models of cowbird-host systems have not led to tests of their predictions. We combine results from a cowbird- removal experiment (Smith et al. 2002, 2003) with a stochastic simulation model that we developed, to reassess the effect of cowbirds on the annual reproductive success (ARS) and nesting success in Song Sparrows (Melospiza melodia). Our model followed the breeding success of individual Song Sparrow nests and extrapolated to output variables including ARS, nest survival, and parasitism rates. We parameterized the model with field data from cowbird control sites (i.e., cowbirds not manipulated) and found that output variables matched those observed. We used the reduced parasitism rates observed on cowbird-removal sites, reran the model, and compared output with observed values. On removal sites, ARS was greater than predicted by the model, which indicates that the model failed to account for some biological phenomenon that occurred when cowbirds were in the system. To assess what this phenomenon might be, we conducted further analyses that indicated that cowbirds may facilitate nest predation by “conventional” predators. Using elasticity analyses, we show that cowbirds have their largest effect on ARS through egg removal and that conventional predators are more important than cowbirds in directly affecting nest survival rates. We report that to assess the effect of cowbirds on nest survival, researchers must avoid using the common technique of comparing survival rates of parasitized and unparasitized nests within populations. Réévaluation de la Menace du Vacher

Relationship Between Nest Predation Suffered by Hosts and Brown-Headed Cowbird Parasitism: A Comparative Study

2006 ◽  
Vol 20 (2) ◽  
pp. 97-111 ◽  
Author(s):  
Jesús M. Avilés ◽  
Bård G. Stokke ◽  
Deseada Parejo
Keyword(s):  
Comparative Study ◽  
Nest Predation ◽  
Cowbird Parasitism
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