The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
Uygar Özesmi - One of the best experts on this subject based on the ideXlab platform.
-
generalizability of artificial neural network models in ecological applications predicting nest occurrence and breeding success of the red winged Blackbird agelaius phoeniceus
Ecological Modelling, 2006Co-Authors: Uygar Özesmi, Stacy L. Özesmi, Raleigh J RobertsonAbstract:Separate artificial neural network (ANN) models were developed from data in two geographical regions and years apart for a marsh-nesting bird, the Red-Winged Blackbird Agelaius phoeniceus. Each model was independently tested on the spatially and temporally distinct data from the other region to determine how generalizable it was. The first model was developed to predict occurrence of nests in two wetlands on Lake Erie, Ohio in 1995 and 1996. The second model was developed to predict breeding success in two marshes in Connecticut, USA in 1969 and 1970. Independent variables were vegetation durability, stem density, stem/nest height, distance to open water, distance to edge, and water depth. The nest occurrence model performance on the training data were at an average cross entropy, or concordance index (c-index), of 0.75. Within geographical region testing in two different wetlands resulted in c-indices of 0.66 and 0.53. The breeding success model performance was at a c-index of 0.75 on the training data and at c-indices of 0.47 and 0.53 for within region testing. When we tested the nest occurrence model on fledged nestling data we obtained c-indices of 0.69 and 0.47 in Clarkes Pond in 1969 and 1970, respectively, and 0.43 and 0.52 in All Saints Marsh in 1969 and 1970, respectively. When we tested the fledged nestling model on the nest occurrence data, we obtained c-indices of 0.70 and 0.41 in Stubble Patch in 1995 and 1996, respectively, and 0.54 and 0.55 for Darr in 1995 and 1996, respectively. With input variable relevances, sensitivity analyses and neural interpretation diagrams we were able to understand how the different models predicted nest occurrence and breeding success and compare their differences and similarities. Important variables for predicting nest site selection/breeding success in both models were vegetation durability and distance to open water. Both models also predicted increasing nest occurrence/breeding success with increasing water depth under the nest and increasing distance to edge. However, relationships for prediction differed in the models. Generalizability of the models was poor except when the marshes had similar values of important variables in the model, for example water depth. ANN models performed better than generalized linear models (GLM) on marshes with similar structures. Generalizability of the models did not differ in nest occurrence and breeding success data. Extensive testing also showed that the GLMs were not necessarily more generalizable than ANNs. The results from this study suggest that ANN models make good definitions of a study system but are too specific to generalize well to other ecologically complex systems unless input variable distributions are very similar.
-
An artificial neural network approach to spatial habitat modelling with interspecific interaction
Ecological Modelling, 1999Co-Authors: Stacy L. Özesmi, Uygar ÖzesmiAbstract:Spatial models for habitat selection of marsh-breeding bird species were developed using artificial neural networks. The habitat models included single and multiple species artificial neural networks for Red-Winged Blackbird (Agelaius phoeniceus) and marsh wren (Cistothorus palustris). Data for the study came from two diked wetland basins on southwestern Lake Erie, USA. The single species artificial neural network model performed better than the logistic regression model except in the presence of interspecific interaction with marsh wren. A multiple species habitat model was developed using data from one basin that included both nesting Red-Winged Blackbirds and marsh wrens. The multiple species neural network model performed better than the logistic regression model in the presence of interspecific interaction and could simultaneously predict the nest locations of both species. Using neural interpretation diagrams, relevances, and sensitivity analyses, we determined the mechanisms of habitat selection in Red-Winged Blackbirds and marsh wrens. Habitat selection in marsh-breeding bird species was a non-linear process that could not be sufficiently understood in terms of general linear models. The non-linear structure of the neural network model not only predicts habitat selection better, but with a critical evaluation through neural interpretation diagrams, relevances and sensitivity analyses can lead to a better understanding of the mechanisms of habitat selection. As predictive tools single species neural network models were too specific in cases where the system changed to include interacting species. In these cases linear models might be better predictors but not necessarily provide a better understanding. In the presence of two interacting species we suggest the use of a neural network model that is trained with a data set from a wetland where all the interacting species are present. In the absence of the interacting species the dynamics will change and habitat selection can be based on an entirely different set of rules and relationships. Therefore, the decision on which neural network model to use must be based on an in-depth understanding of the ecology of the system under study.
-
a spatial habitat model for the marsh breeding red winged Blackbird agelaius phoeniceus l in coastal lake erie wetlands
Ecological Modelling, 1997Co-Authors: Uygar Özesmi, William J MitschAbstract:A spatial model was developed to predict the distribution of a marsh-nesting bird species, Red-Winged Blackbird (Agelaius phoeniceus L.) in Lake Erie coastal wetlands. The study site was in two diked wetland basins in Ottawa County, Ohio, USA. Geographic Information System (GIS) was used for data handling, storage, analyzing and running the model. Nests of birds were located, and vegetation durability, vegetation height, vegetation density, water depth, open water and structural aspects of the study basins were quantified by low altitude aerial photography and extensive field work for ground truthing. Spatial variables such as distance to open water edge, distance to wetlands edge, and friction maps by spread over depth and stem density for simulating predator access to wetlands were generated using the GIS. Model variables and coefficients were determined using logistic regression. Vegetation durability, distance to open water and depth of water significantly (P < 0.01) affected the nesting outcome. Results show that the probability of a bird nesting in a location within a marsh increased with increasing vegetation durability, water depth, and with decreasing distance to open water edge. Model verification and validation indicated that the model did not show any interspecific interactions or clumping of nest sites defined by behavioral constraints. Results were in accordance with the conclusions of previous studies looking at breeding success of Red-Winged Blackbird. This study validated the processes affecting nest site selection of Red-Winged Blackbirds with extensive data and statistical analyses. The methodology and versatile character of the GIS-based spatial model enables adaptations to any other marsh-nesting bird species and geographic area. Data needed for the model are relatively easy to obtain and the model provides micro-habitat scale results that can be used by wetland conservationists and managers.
Jack W. Bradbury - One of the best experts on this subject based on the ideXlab platform.
-
acoustic directionality of red winged Blackbird agelaius phoeniceus song relates to amplitude and singing behaviours
Animal Behaviour, 2008Co-Authors: Gail L. Patricelli, Marc S. Dantzker, Jack W. BradburyAbstract:Sound waves typically radiate from a vocalizing animal with unequal amplitude in different directions; this may profoundly affect communication, favouring adaptations that use or compensate for this directionality. Previous studies suggest that variation in directionality among vocalization types is related to function, with vocalizations such as alerts being relatively omnidirectional, thus maximizing the number of surrounding receivers, and vocalizations such as courtship calls being relatively directional, thus reducing eavesdropping by beaming sounds at the targeted receiver. Here we examine variation within a vocalization type, bird songs, to test hypotheses about how variation in song directionality relates to singing behaviour and the social context of singing. We measured the directionality and amplitude of Red-Winged Blackbird songs in the field using calibrated microphones encircling the bird. We found variation in directionality among song types, possibly allowing males to select songs from their repertoires with directionality to suit the social context. We found support for the hypothesis that the amplitude and directionality of songs are related, with more-directional songs delivered at higher amplitudes. In addition, we found support for the hypothesis that directionality is negatively related to the degree of male rotation on the perch between vocalizations, suggesting that males may combine omnidirectional songs and rotation to broadcast their songs, and may face the receiver and produce directional songs during direct interactions. We also observed variation in directionality among note types within songs. These results suggest that directionality plays an important role in shaping song structure and singing behaviour in Red-Winged Blackbirds.
-
Differences in acoustic directionality among vocalizations of the male Red-Winged Blackbird (Agelaius pheoniceus) are related to function in communication
Behavioral Ecology and Sociobiology, 2007Co-Authors: Gail L. Patricelli, Marc S. Dantzker, Jack W. BradburyAbstract:Studies of animal acoustic communication have found that the frequency and temporal structure of acoustic signals can be shaped by selection for efficient communication. The directionality of acoustic radiation may also be adapted for communication, but we know relatively little about how directionality varies with signal function, sender morphology, and the environment in which the sound is transmitted. We tested the hypothesis that the directionality of a vocalization is adapted to its function in communication. This hypothesis predicts that vocalizations that are directed to multiple conspecifics (e.g., advertisements and alarms) will be relatively omnidirectional because this will maximize the number of neighbors and mates that receive the signal, and that vocalizations directed to particular individuals will be relatively directional because this will maximize detection of the signal by the targeted receiver and minimize eavesdropping. To test these predictions, we measured the directionality and amplitude of Red-Winged Blackbird ( Agelaius pheoniceus ) vocalizations in the field by recording vocalizations simultaneously on eight calibrated microphones encircling the bird. We found significant variation in directionality among vocalizations. Supporting our predictions, we found that the most omnidirectional vocalizations were those used to alert conspecifics to danger, and the most directional vocalizations are those used during courtship and solicitation of copulation, when the costs of eavesdropping are likely to be high. These results suggest that the directionality of Red-Winged Blackbird vocalizations is shaped by selection for effective communication. This study is the first to provide statistical support for the hypothesis that directionality is related to the function of a signal in communication.
Susanna Ogle - One of the best experts on this subject based on the ideXlab platform.
-
laying sequence variation in yolk carotenoids and egg characteristics in the red winged Blackbird agelaius phoeniceus
Journal of Avian Biology, 2015Co-Authors: Jennifer L Newbrey, Kevin J. Mcgraw, Cynthia A. Paszkowski, Susanna OgleAbstract:In many bird species with asynchronous hatching, smaller, later-hatched nestlings are out-competed for food by their larger, earlier-hatched siblings and therefore suffer increased mortality via starvation. It is thought that female birds can either maintain or reduce the survival disadvantage of later-hatched nestlings by differentially allocating maternal resources across the eggs of a clutch. Carotenoid pigments are an example of resources that female birds allocate differentially when producing a clutch, but laying sequence patterns for these pigments remain poorly studied in North American songbirds. We examined intraclutch variation in yolk carotenoids and egg metrics in 27 full clutches of Red-Winged Blackbird Agelaius phoeniceus eggs collected from eight wetlands in central Alberta, Canada. We predicted that carotenoids would decrease across the laying sequence, as in this species, later-hatched, marginal nestlings suffer greater mortality than earlier-hatched, core nestlings. We found nine carotenoid pigments in Red-Winged Blackbird egg yolks, including two that have never been described from avian yolks: α-doradexanthin and adonirubin. As predicted, concentrations and amounts of most carotenoids decreased across the laying sequence, suggesting that female Red-Winged Blackbirds depleted their carotenoid resources as they laid more eggs. However, egg mass and yolk mass both increased across the laying sequence, suggesting that female Red-Winged Blackbirds may use other maternal resources to compensate for the size and survival disadvantage experienced by later-hatched, marginal nestlings.
-
Laying‐sequence variation in yolk carotenoids and egg characteristics in the red‐winged Blackbird Agelaius phoeniceus
Journal of Avian Biology, 2014Co-Authors: Jennifer L Newbrey, Kevin J. Mcgraw, Cynthia A. Paszkowski, Susanna OgleAbstract:In many bird species with asynchronous hatching, smaller, later-hatched nestlings are out-competed for food by their larger, earlier-hatched siblings and therefore suffer increased mortality via starvation. It is thought that female birds can either maintain or reduce the survival disadvantage of later-hatched nestlings by differentially allocating maternal resources across the eggs of a clutch. Carotenoid pigments are an example of resources that female birds allocate differentially when producing a clutch, but laying sequence patterns for these pigments remain poorly studied in North American songbirds. We examined intraclutch variation in yolk carotenoids and egg metrics in 27 full clutches of Red-Winged Blackbird Agelaius phoeniceus eggs collected from eight wetlands in central Alberta, Canada. We predicted that carotenoids would decrease across the laying sequence, as in this species, later-hatched, marginal nestlings suffer greater mortality than earlier-hatched, core nestlings. We found nine carotenoid pigments in Red-Winged Blackbird egg yolks, including two that have never been described from avian yolks: α-doradexanthin and adonirubin. As predicted, concentrations and amounts of most carotenoids decreased across the laying sequence, suggesting that female Red-Winged Blackbirds depleted their carotenoid resources as they laid more eggs. However, egg mass and yolk mass both increased across the laying sequence, suggesting that female Red-Winged Blackbirds may use other maternal resources to compensate for the size and survival disadvantage experienced by later-hatched, marginal nestlings.
Ken Yasukawa - One of the best experts on this subject based on the ideXlab platform.
-
THE “predator early warning system” of Red-Winged Blackbirds
Journal of Field Ornithology, 2020Co-Authors: Nicole Burton, Ken YasukawaAbstract:Male Red-Winged Blackbirds (Agelaius phoeniceus) are known to give alarm calls in response to the approach of a predator, and to encode information about the level of threat in their calling behavior. To determine whether such sentinel males alert females, we conducted a simple field experiment in which we measured the distances at which incubating females flushed from their nests in response to the approach of a human observer. Using a matched-pairs design, we measured flushing distances with a sentinel male present (mean 19.8 m), and when the same male was absent from his territory (mean 10.4 m). Female Red-Winged Blackbirds flushed from their nests at significantly greater distances when males were present than when males were absent. These results and those of other studies support the existence of a “predator early warning system” in the Red-Winged Blackbird.
-
Yellow-billed Cuckoo Hatched and Fed by a Red-Winged Blackbird
The Wilson Journal of Ornithology, 2010Co-Authors: Ken YasukawaAbstract:Abstract I observed a Red-Winged Blackbird (Agelaius phoeniceus) nest in southcentral Wisconsin, USA that received a Yellow-billed Cuckoo (Coccyzus americanus) egg. The cuckoo egg was laid after the Blackbird clutch was complete and the female had begun incubation. The parasitic egg was considerably different in size and color, but was accepted by the female Red-Winged Blackbird. The female, but not the male, also cared for the nestling, which was strikingly different in plumage, gape markings, and begging behavior, and which grew despite its 3–4 day hatching delay relative to its nest mates. Rapid development and exaggerated begging behavior of the Yellow-billed Cuckoo nestling may enable a parasitic cuckoo nestling to compete successfully with host nestlings for food.
-
epaulet color and sexual selection in the red winged Blackbird a field experiment
The Condor, 2009Co-Authors: Ken Yasukawa, David A Enstrom, Patricia G Parker, Thomas C JonesAbstract:Abstract. The epaulets of male Red-Winged Blackbirds (Agelaius phoeniceus) function in both intersexual and intrasexual contexts, but there is little evidence that they covary with reproductive success in this well-studied species. We used path analysis of male/territory traits, mating success, and reproductive success of unmanipulated males to estimate current directional selection. Territory size had a positive effect on number of within-pair mates. Number of extra-pair mates had a positive effect on number of extra-pair fledglings, and number of within-pair and extra-pair fledglings had positive effects on total number of fledglings. We also reddened epaulets of free-living territorial males to determine whether manipulated and control males differ in territorial behavior, mating success, or reproductive success. Compared with control males, males with reddened epaulets incurred elevated rates of trespassing and territorial challenges, lost their territories more often, and were unable to produce extra...
-
impact of brood parasitism by brown headed cowbirds on red winged Blackbird reproductive success
The Condor, 1999Co-Authors: Ethan D Clotfelter, Ken YasukawaAbstract:We examined brood parasitism by Brown-headed Cowbirds (Molothrus ater) on a prairie-nesting population of Red-Winged Blackbirds (Agelaius phoeniceus) from 1984 to 1997 and the extent to which parasitism affected host reproductive success. During this 14-year period, 2-32% of redwing nests were parasitized per year. Two measures of cowbird parasitism, the proportion of nests parasitized and the number of cowbird eggs laid per year. significantly increased over time. Increases in these estimates of the intensity of parasitism were independent of annual changes in nesting density of Red-Winged Blackbirds. Clutch size was reduced in parasitized nests, most likely as a result of host egg removal by cowbirds, but hatching success was similar between parasitized and unparasitized nests. Red-Winged Blackbirds abandoned more than one-third of all parasitized nests. We estimated the cost of abandonment in terms of increased failure rate and decreased fledgling production of re-nesting attempts. When we excluded abandoned nests from the analysis, there was no difference in the probability of success between parasitized and unparasitized nests. Nestlings from parasitized nests were similar in mass and tarsus length to nestlings from unparasitized nests, but parasitized nests produced fewer redwing fledglings per successful nest. The success of unparasitized nests was negatively related to the intensity of cowbird parasitism, suggesting that cowbirds are predators as well as brood parasites of redwing clutches.
-
response to playback of nestling begging in the red winged Blackbird agelaius phoeniceus
Animal Behaviour, 1998Co-Authors: Julie E Burford, Teresa J Friedrich, Ken YasukawaAbstract:Abstract Nestling birds may honestly signal their need for food to provisioning adults, or begging might be a manipulative attempt to coerce additional food from providers, but in either case, providers respond to an increase in begging with an increase in feeding. We used playback of begging calls recorded from nestlings to determine whether male and female Red-Winged Blackbirds increase their feeding rates in response to an apparent increase in begging. Both females and males fed broods at significantly higher rates after 5-min begging call playbacks than before, although only eight of 30 males were observed to feed nestlings in this study. In contrast, using the same playback design, neither females nor males altered their feeding rates significantly in response to broadcasts of noise. These results and others suggest that begging vocalizations are a basis for short-term adjustments in the rate at which nestling birds are provisioned. These results are also compared with those of a similar study of the same species, in which playback had no significant effect on rates of provisioning.
David F. Westneat - One of the best experts on this subject based on the ideXlab platform.
-
Seasonal variation in ejaculate traits of male Red-Winged Blackbirds (Agelaius phoeniceus)
Behavioral Ecology and Sociobiology, 2012Co-Authors: Stefan Lupold, Tim R. Birkhead, David F. WestneatAbstract:Many reproductive traits, including ejaculate characteristics, usually show remarkable seasonal variation, but the potential for such dynamics in sperm morphology has been overlooked. Several studies have revealed high within-male repeatability in sperm morphology, but samples have typically been collected within a few hours or days, and the consistency of sperm morphology over longer periods remains unexplored. Here, we tested whether ejaculate traits, including sperm morphology, sperm number, and sperm velocity, exhibit seasonal phenotypic plasticity in a long-lived seasonal breeder, the Red-Winged Blackbird ( Agelaius phoeniceus ). We found absolute and/or relative flagellum length and sperm velocity to increase across the season, whereas sperm numbers within ejaculates declined. Sperm morphological traits were further positively associated with harem size or the total number of offspring that fledged in each male’s territory, suggesting that sperm morphology is likely to be linked to male reproductive quality. The underlying mechanisms of these patterns of seasonal variation remain unresolved, but we discuss our results in the context of dynamics of reproductive hormones, testicular structures and function, and reproductive behavior.
-
geographical variation in sperm morphology in the red winged Blackbird agelaius phoeniceus
Evolutionary Ecology, 2011Co-Authors: David F. Westneat, Stefan Lupold, T R BirkheadAbstract:Many species differ genetically, physiologically, and morphologically between geographically distinct populations, typically in response to variation in ecological and climatic variables. Little is known, however, about geographical variation in sperm morphology. Sperm morphology is under strong sexual selection, has been shown to evolve rapidly, and often co-varies with other reproductive traits (e.g., testis size or mating system) that differ between populations in some species. The aim of this study was to establish whether sperm morphology varies between populations of the Red-Winged Blackbird (Agelaius phoeniceus), a species with an enormous breeding range and marked inter-population variation in both body size and mating system. We found (1) highly significant variation in sperm morphology among study sites, (2) a gradual increase in sperm length from the southwest to the northeast of the breeding range, and (3) a strong negative association between sperm length and body size. However, the relationship with the mating system remains unclear. Several hypotheses to explain these patterns are proposed.
-
paternity and paternal behaviour in the red winged Blackbird agelaius phoeniceus
Animal Behaviour, 1995Co-Authors: David F. WestneatAbstract:Abstract The relationship between paternity and male parental behaviour was investigated in an eastern population of Red-Winged Blackbirds. Data collected over four seasons revealed substantial variation in paternity and the frequency of male provisioning. The feeding of nestlings by males increased non-linearly with the age of the nestlings but did not differ within or between seasons. Average relative provisioning by males to individual nests was not associated with the proportion of nestlings sired by the territory owner (determined through multi-locus DNA fingerprinting), either in a bivariate analysis or a multivariate analysis with those variables found to be associated with male parental care in other studies of Red-Winged Blackbirds. Males provisioned significantly less frequently at nests of older females, but paternity was not associated with female age. The later in the season a female settled, the higher her mate's paternity in her brood, yet male provisioning was not associated with female settlement date. Estimated total provisioning by males (sum of all feeding trips over all nests in each male's territory) was not associated with average paternity in bivariate and multivariate analyses. Total provisioning by males was positively associated with the number of days in the season the male had a brood in a bivariate test, but not with male age, the number of females nor male condition in either bivariate or multivariate analyses. The lack of a relationship between paternity and paternal effort fits predictions of recent theory on the potential effects of reduced paternity on paternal behaviour given (1) the lack of consistent patterns of paternity among nests of different order, time of season and male and female age and (2) generally weak associations between possible behavioural cues about paternity and actual paternity.
-
Estimating average within-group relatedness from DNA fingerprints
Molecular Ecology, 1992Co-Authors: Hudson K Reeve, David F. Westneat, David C QuellerAbstract:We present a detailed analysis of a regression and an equivalent band-sharing technique for estimating mean within-group relatedness from DNA fingerprint data. First, we show that the relatedness estimate obtained from this technique tends to underestimate the pedigree relatedness in random-mating populations, but that the degree of underestimation will be small unless DNA fingerprint similarity among unrelated individuals is unusually high. We derive the exact asymptotic downward bias as a function of allele frequency and probabilities of identity by descent. We suggest some methods for removing the small downward bias in the regression estimate. Secondly, we show that the technique yields accurate estimates of parent-offspring, full, and half-sibling relatedness in natural populations of the Red-Winged Blackbird Agelaius phoeniceus and indigo bunting Passerina cyanea.