Frequency Of Brood Parasitism Research Articles

Understanding nest success and brood parasitism in the endangered Black-capped Vireo: comparisons with two sympatric songbirds

Abstract Nest predation and brood parasitism likely cause declines in many songbird species, yet the rate of these declines varies among species. Simultaneously studying co-occurring species with overlapping territories provides an opportunity to identify differences among the species that may explain differential reproductive success. We monitored nests of three co-occurring songbird species to determine whether the federally endangered Black-capped Vireo (Vireo atricapilla) experienced lower reproductive success than Northern Cardinals (Cardinalis cardinalis) and White-eyed Vireos (V. griseus) on private lands with and without trapping of brood parasites. We assessed if habitat metrics and nesting phenology were associated with nest success and frequency of brood parasitism by Brown-headed Cowbirds (Molothrus ater) to determine if these characteristics explain poor reproductive success. We monitored 188 nests in shrubland and ecotones with woodlands in central Texas from 2006–2008. We found species-spec...

Southwestern Willow Flycatchers (Empidonax Traillii Extimus) in a Grazed Landscape: Factors Influencing Brood Parasitism

AbstractBrood parasitism by Brown-headed Cowbirds (Molothrus ater; hereafter “cowbirds”) is an important factor contributing to the endangered status of the Southwestern Willow Flycatcher (Empidonax traillii extimus, hereafter “flycatcher”). We report on factors that influence brood parasitism on the flycatcher using seven seasons of nest data (n = 491 nests) collected in riparian patches comprising cottonwood (Populus fremontii), willow (Salix spp.), and boxelder (Acer negundo) along the Gila River in southwest New Mexico. We quantified habitat and landscape characteristics that might be associated with higher levels of parasitism and assessed the correlation between those and the observed incidence of nest parasitism. Given that cowbirds associate with cattle, we were particularly interested to determine whether the distance to active summer grazing would influence the frequency of brood parasitism. We found an apparent negative trend between the distance to grazing and brood parasitism, but this trend was not statistically significant. Rather, brood parasitism was more strongly correlated with characteristics of the habitat. Specifically, nests in larger patches, and nests built near the patch edge adjacent to the river, were more susceptible to parasitism, which suggests that these areas are preferred nesting habitat for cowbirds because of a potentially greater abundance of hosts. Parasitism was significantly lower within the core of large patches, but the insulating effect was not evident in small and medium-sized patches. Higher nest height was strongly correlated with lower probability of parasitism, most notably for nests in boxelders. Nests in boxelders were less susceptible to parasitism, whereas nests in willows were more susceptible to parasitism. We discuss the results in the context of other studies. We recommend that management efforts to recover the flycatcher should focus on increasing quality habitat, and we suggest that cattle management should focus on eliminating the adverse effects of grazing on riparian health as a more feasible option than removing cattle far enough from riparian corridors so as to preclude parasitism.Empidonax traillii extimus en un Paisaje con Pastoreo: Factores que Influyen sobre el Parasitismo de la Nidada

Brood parasitism by brown-headed cowbirds and the expression of sexual characters in their hosts

Interspecific brood parasites may use the secondary sexual characters of the hosts to decide which species to parasitize. Hence, species with conspicuous and well-recognisable traits may have higher chances of becoming parasitised. Using North American birds and their frequent brood parasite, the brown-headed cowbird Molothrus ater, we tested the relationship between features of song and plumage coloration of hosts and the frequency of brood parasitism while controlling for several potentially confounding factors. Relying on two sets of analysis, we focused separately on the evolutionary view of the parasite and the host. From the cowbird's perspective, we found that males of heavily parasitized species posit songs with low syllable repertoire size, shorter inter-song interval and have brighter plumage. From the host's perspective, a phylogenetic analysis revealed similar associations for features of song, but not for plumage characteristics that were unrelated to brood parasitism. These comparative findings may imply that brood parasites choose novel hosts based on heterospecific signals; and/or host species working against sexual selection escape from brood parasitism by evolving inconspicuous sexual signals. Although our data do not allow us to distinguish between these two evolutionary scenarios, our results suggest that selection factors mediating cowbird parasitism via host recognition by heterospecific signals may have an important role in the evolutionary relationship between brood parasites and their hosts.

Brood Parasitism and Egg Transfer in Cave Swallows (Petrochelidon Fulva) and Cliff Swallows (P. Pyrrhonota) in South Texas

AbstractWe studied the frequency of intraspecific brood parasitism and physical transfer of eggs between nests in colonially nesting Cave Swallows (Petrochelidon fulva) and Cliff Swallows (P. pyrrhonota) in south Texas in 2001. Although the eggs of the two species look similar, frequency of brood parasitism in each species was unaffected by presence of the other species, which suggests that the parasitism we observed was largely by conspecifics. We detected brood parasitism in 4.6–5.0% of Cave Swallow nests and in 10.7–11.9% of Cliff Swallow nests. Brood parasitism was not significantly related to colony size in either species, to eventual success of the host nest, or to overall colony nesting success (a measure of environmental risk). We detected evidence of physical transfer of eggs in 0.7–2.0% of nests of these species. Cliff Swallows parasitized nests more often than Cave Swallows, but the frequencies of brood parasitism and egg transfer in the two species in south Texas appeared broadly comparable to those reported for Cliff Swallows in Nebraska, despite geographic differences in habitat, seasonality, breeding phenology, and levels of sociality between the populations.

BROOD PARASITISM AND EGG TRANSFER IN CAVE SWALLOWS (PETROCHELIDON FULVA) AND CLIFF SWALLOWS (P. PYRRHONOTA) IN SOUTH TEXAS

Abstract We studied the frequency of intraspecific brood parasitism and physical transfer of eggs between nests in colonially nesting Cave Swallows (Petrochelidon fulva) and Cliff Swallows (P. pyrrhonota) in south Texas in 2001. Although the eggs of the two species look similar, frequency of brood parasitism in each species was unaffected by presence of the other species, which suggests that the parasitism we observed was largely by conspecifics. We detected brood parasitism in 4.6–5.0% of Cave Swallow nests and in 10.7–11.9% of Cliff Swallow nests. Brood parasitism was not significantly related to colony size in either species, to eventual success of the host nest, or to overall colony nesting success (a measure of environmental risk). We detected evidence of physical transfer of eggs in 0.7–2.0% of nests of these species. Cliff Swallows parasitized nests more often than Cave Swallows, but the frequencies of brood parasitism and egg transfer in the two species in south Texas appeared broadly comparable t...

THE RELATIONSHIP OF HABITAT AND SPATIAL DISTRIBUTION OF NESTS WITH BROWN-HEADED COWBIRD PARASITISM OF RED-WINGED BLACKBIRDS

I studied the relationship of nesting habitat and the spatial distribution of Red-winged Blackbird (Agelaius phoeniceus) nests with the frequency of brood parasitism by Brown-headed Cowbirds (Molothrus ater). For all nests combined, parasitism was over 18 times more frequent in the upland habitat. It is unlikely that the low frequency of parasitism in the marshes was due solely to an increase in the incidence of aggregate nesting. For aggregated nests, parasitism was over nine times more common in upland habitat than in marshes. Because Red-winged Blackbirds are known to react to and deter cowbirds when cowbirds are detected near nests, I assessed whether the ability of Red-winged Blackbirds to detect cowbirds may contribute to the low parasitism frequency observed in marshes. Red-winged Blackbirds nesting in marshes more often reacted aggressively to female cowbird mounts 1 m from a nest than those in upland habitat, indicating that cowbirds are more likely to be molested near nests in marshes. In upland habitat the frequency of parasitism of unaggregated nests was three times greater than that of aggregated nests. These results suggest that Red-winged Blackbirds can defend their nests against cowbirds and successfully prevent brood parasitism and that the effectiveness of nest defense varies with habitat and the spatial distribution of nests. This study provides the first direct evidence that hosts can sometimes prevent parasitism.

Use of Clutch Size to Infer Brood Parasitism in Wood Ducks

Total clutch size often is used to infer the frequency of brood parasitism in wood ducks (Aix sponsa), but the accuracy of this method is unknown. By monitoring nest boxes daily, we determined parasitism rates in 35 nests over 2 years and then compared these rates with those that would have been inferred using published clutch size criteria. Clutch size alone gave an inaccurate estimate of parasitism. The criterion «>12 eggs» slightly overestimated (+3%) the true parasitism rate, while «>13 eggs» slightly underestimated it (−8%)

Effects of Brood Parasitism and Nest-Box Placement on Wood Duck Breeding Ecology

Intraspecific brood parasitism occurs frequently among Wood Duck (Aix sponsa) populations nesting in artificial structures. To assess the effects of such parasitism on population ecology, we analyzed 12 years of Wood Duck nesting records (1976-1987) from a study site in northeastern Illinois. Hatchability of eggs (ducklings produced/total eggs laid) was inversely correlated with population density, with the frequency of parasitism, and with the number of eggs laid per nest. The hatchability of all eggs laid in nests that had been parasitized (16-44 eggs) was 57.5% vs. 67.3% for eggs laid in "normal" nests (7-15 eggs). The negative consequences of parasitism were due mainly to nest abandonment, damaged eggs, and eggs laid after the start of incubation, and occurred despite the consistent availability of suitable unused boxes. The frequency of brood parasitism was strongly affected by box placement. During 1976-1987, parasitism occurred in 49.5% of boxes erected singly in highly visible locations, in 49.5% of boxes erected in highly visible groups, but in only 29.8% of boxes that had been erected singly in visually occluded habitat. Mean clutch sizes for the visible-isolated (15.7 eggs) and visible-clumped (16.3 eggs) boxes were significantly higher (F = 4.49, P = 0.012) than for the well-hidden boxes (12.4 eggs). Hatchability in successful well-hidden nests was 82.0% vs. ca. 74.0% in successful visible boxes. The data suggest that reduced parasitism and increased hatchability occur when artificial nesting structures are placed in habitats and at densities resembling the natural circumstances in which Wood Ducks evolved. These results have implications not only for the study and management of A. sponsa populations, but also for the placement of nest boxes in behavioral and ecological studies of other cavity-nesting birds.