Quiscalus Quiscula Research Articles

The USDA APHIS WS Unified Model for Estimating DRC-1339 Bait Application Take Estimates as Effected by French Fry Bait Size

DRC-1339 (CPTH, 3-chloro-p-tolouidine) is an avicide registered to reduce local populations of selected bird species at feedlots, dairies, and staging areas near rice fields, and to prevent livestock depredation. Additionally, two registrations are specifically for controlling gulls and pigeons. U.S. Department of Agriculture Wildlife Services personnel historically have used a variety of methods to estimate take, including counting carcasses and quantifying reduction in bird activity. Because this avicide is slow-acting and birds usually succumb away from the bait site, carcass recovery provides poor estimates of take. Because of natural variability in bird numbers and activity, quantifying reductions in bird activity is also a poor gauge of efficacy. Scientists at the U.S. Department of Agriculture APHIS Wildlife Services National Wildlife Research Center developed and continue to adapt and refine a model using a bioenergetics approach to estimate consumption and the resulting mortality from DRC-1339 bait consumption. The model estimates take for the major baits used under the feedlot and staging area labels for European starlings, blackbirds, brown-headed cowbirds, and common grackles. Consumption of homogeneous baits (rice, cracked corn, fat pellets) has been well characterized, and take (i.e., mortality) is accurately predicted in the model. However, predictions of take when french fries were used as a bait for controlling starlings at feedlots in Washington State were less accurate. Thus, we modified the model to capture the feeding behavior of birds using this highly heterogeneous bait by removing the dependence on bait mass and simplifying the calculation of dose ingested. The modified model calculates dose directly from the amount of DRC-1339 per calorie consumed instead of from the DRC-1339 concentration per bait consumed. In this paper, we compare estimates of take based on french fry bait mass distributions and caloric contents determined for five different french fry bait types.

The green June beetle (Cotinis nitida) (Coleoptera: Scarabaeidae): local variation in the beetle’s major avian predators and in the competition for mates

The green June beetle (Cotinis nitida) was observed in northern Virginia for a second and third flight season. The study yielded some results that were consistent with earlier findings, namely that mate-locating beetles were vulnerable to attack by avian predators and matings occurred primarily early in the flight season. Novel findings included the following: (1) blue jays (Cyanocitta cristata) were the major predators, not common grackles (Quiscalus quiscala), (2) some jays appeared to selectively prey on female beetles, (3) competition for mates among male beetles could be so intense that some males attempted to copulate with already mated (unreceptive) females, and (4) the sex ratio of the beetle population feeding on wild blackberries remained near equality late in the flight season despite the fact that the sex ratio of the population of beetles at the emergence site became highly female-biased over time.

Vector-Host Interactions of Culiseta melanura in a Focus of Eastern Equine Encephalitis Virus Activity in Southeastern Virginia.

Eastern equine encephalitis virus (EEEV) causes a highly pathogenic mosquito-borne zoonosis that is responsible for sporadic outbreaks of severe illness in humans and equines in the eastern USA. Culiseta (Cs.) melanura is the primary vector of EEEV in most geographic regions but its feeding patterns on specific avian and mammalian hosts are largely unknown in the mid-Atlantic region. The objectives of our study were to: 1) identify avian hosts of Cs. melanura and evaluate their potential role in enzootic amplification of EEEV, 2) assess spatial and temporal patterns of virus activity during a season of intense virus transmission, and 3) investigate the potential role of Cs. melanura in epidemic/epizootic transmission of EEEV to humans and equines. Accordingly, we collected mosquitoes at 55 sites in Suffolk, Virginia in 2013, and identified the source of blood meals in engorged mosquitoes by nucleotide sequencing PCR products of the mitochondrial cytochrome b gene. We also examined field-collected mosquitoes for evidence of infection with EEEV using Vector Test, cell culture, and PCR. Analysis of 188 engorged Cs. melanura sampled from April through October 2013 indicated that 95.2%, 4.3%, and 0.5% obtained blood meals from avian, mammalian, and reptilian hosts, respectively. American Robin was the most frequently identified host for Cs. melanura (42.6% of blood meals) followed by Northern Cardinal (16.0%), European Starling (11.2%), Carolina Wren (4.3%), and Common Grackle (4.3%). EEEV was detected in 106 mosquito pools of Cs. melanura, and the number of virus positive pools peaked in late July with 22 positive pools and a Maximum Likelihood Estimation (MLE) infection rate of 4.46 per 1,000 mosquitoes. Our findings highlight the importance of Cs. melanura as a regional EEEV vector based on frequent feeding on virus-competent bird species. A small proportion of blood meals acquired from mammalian hosts suggests the possibility that this species may occasionally contribute to epidemic/epizootic transmission of EEEV.

Spatially explicit modeling of blackbird abundance in the Prairie Pothole Region

Knowledge of factors influencing animal abundance is important to wildlife biologists developing management plans. This is especially true for economically important species such as blackbirds (Icteridae), which cause more than $100 million in crop damages annually in the United States. Using data from the North American Breeding Bird Survey, the National Land Cover Dataset, and the National Climatic Data Center, we modeled effects of regional environmental variables on relative abundance of 3 blackbird species (red-winged blackbird, Agelaius phoeniceus; yellow-headed blackbird, Xanthocephalus xanthocephalus; common grackle, Quiscalus quiscula) in the Prairie Pothole Region of the central United States. We evaluated landscape covariates at 3 logarithmically related spatial scales (1,000ha, 10,000ha, and 100,000ha) and modeled weather variables at the 100,000-ha scale. We constructed models a priori using information from published habitat associations. We fit models with WinBUGS using Markov chain Monte Carlo techniques. Both landscape and weather variables contributed strongly to predicting blackbird relative abundance (95% credibility interval did not overlap 0). Variables with the strongest associations with blackbird relative abundance were the percentage of wetland area and precipitation amount from the year before bird surveys were conducted. The influence of spatial scale appeared small—models with the same variables expressed at different scales were often in the best model subset. This large-scale study elucidated regional effects of weather and landscape variables, suggesting that management strategies aimed at reducing damages caused by these species should consider the broader landscape, including weather effects, because such factors may outweigh the influence of localized conditions or site-specific management actions. The regional species distributional models we developed for blackbirds provide a tool for understanding these broader landscape effects and guiding wildlife management practices to areas that are optimally beneficial. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Woody cover does not promote activity of nest predators in residential yards

Urban development often affects resource availability in ways that can influence not only community structure, but key species interactions that shape population dynamics. Although some resources are unintentionally altered, others are deliberately changed to improve habitat for urban wildlife, particularly songbirds. We hypothesized that management strategies that encourage planting trees and shrubs (i.e. increasing woody cover) would inadvertently attract predators of bird nests, which are generally abundant within cities. To test this, we examined the relationship between percent woody cover, pooled across trees and shrubs, and diurnal activity patterns of nest predators in residential yards. We surveyed predator activity and characterized habitat using aerial imagery of seven suburban neighborhoods in Franklin County, Ohio during April–August 2011 and 2012. Predator activity varied widely among individual yards, but contrary to our hypothesis, the availability of woody cover at either yard or neighborhood scales was not a strong predictor of diurnal activity in yards for five common species of nest predators (Eastern gray squirrel, Sciurus carolinensis; common grackle, Quiscalus quiscala; brown-headed cowbird, Molothrus ater; blue jay, Cyanocitta cristata; and domestic cat, Felis catus). Thus, our study suggests that wildlife habitat management or gardening programs that recommend increasing woody cover do not necessarily attract some common predators of songbird nests in Midwestern landscapes. Additional research that identifies which habitat features beyond woody cover best predict nest predator activity will facilitate the creation of management recommendations that increase the conservation value of urban environments for songbirds.

Isolation of Escherichia coli O157:H7 and Salmonella from migratory brown-headed cowbirds (Molothrus ater), common Grackles (Quiscalus quiscula), and cattle egrets (Bubulcus ibis).

Zoonotic enteric pathogenic bacteria can live in the intestinal tract of birds and can be transmitted to food animals or humans via fecal contact. In the present study, cecal samples were collected from 376 migratory birds from species often associated with cattle during the fall migration in the Central Flyway of the United States. Brown-headed cowbirds (n=309, Molothrus ater), common grackles (n=51, Quiscalus quiscula), and cattle egrets (n=12, Bubulcus ibis) contained foodborne pathogenic bacteria in their ceca. Salmonella enterica was isolated from 14.9% of all samples, and Escherichia coli O157:H7 from 3.7%. Salmonella serotypes isolated included the following: Muenster, Montevideo, and Typhimurium. Our data suggest that migratory birds associated with cattle could be a vector for zoonotic enteric pathogenic bacteria to be disseminated across long distances.

The mating system and parental behaviour of the green June beetle (Cotinis nitida Linnaeus) (Coleoptera: Scarabaeidae) are exploited by avian predators

Males of the green June beetle (Cotinis nitida) search for females emerging from lawns. Upon detecting the female sex pheromone, a male will eventually drop down close to his potential mate. He then walks rapidly through the grass until he locates the female at which time he mounts his partner. If two or more males arrive more or less simultaneously, the first male to reach the female becomes her mate. The fight pattern of searching males makes them vulnerable to predatory common grackles (Quiscalus quiscala) and blue jays (Cyanocitta cristata), which attack flying or recently landed beetles. Later in the flight season, females flying low in a search for oviposition sites in the lawn are also targeted by grackles and blue jays, demonstrating that both sexually selected behaviour and naturally selected parental behaviour carry fitness costs for green June beetles.

Grassland bird communities on conservation and marginal grasslands in an agricultural landscape

Six years of point count data in eastern Nebraska and western Iowa, USA, were used to investigate how the community structure of grassland birds and the densities of four focal species (common yellowthroat, dickcissel, grasshopper sparrow and sedge wren) varied on conservation lands with differing management strategies (i.e., warm- versus cool-season grasses and low- to high-diversity plantings), and between conservation and unmanaged marginal grasslands (e.g., field borders and terraces). Model-selection results indicated that grasshopper sparrow and dickcissel densities were influenced by grassland type, with higher densities in parcels dominated by warm-season grasses. Species-specific changes in density in response to planting diversity reinforced the value of creating heterogeneous habitat for grassland birds. Densities for all four species were substantially lower in unmanaged marginal grasslands versus conservation parcels and the community structure between the two habitats differed significantly, with generalist species (e.g., American robins, common grackles and grassland species associated with shorter, sparse and patchy vegetation (e.g., horned lark and vesper sparrow)) largely replacing tallgrass specialists in unmanaged marginal grassland parcels.

Context‐dependent costs and constraints of begging and non‐begging activity by common grackle nestlings at the scale of the nanoclimate

Summary Environmental factors such as heat and solar radiation directly affect the open‐cup nest environment and can impact nestling body temperature. The aim of our research was to understand how open‐cup passerine nestlings use behavioural thermoregulation to mitigate solar heat gain and to measure the metabolic cost of begging and non‐begging activity under three light treatments: room light (<2 Wm−2), simulated shade (500 Wm−2) and simulated sun (1000 Wm−2). Our study coupled behavioural (field) and physiological (laboratory) experiments to explore the adaptive behavioural response of passerine nestlings to nest cup nanoclimates (sun and shade), using the common grackle (Quiscalus quiscula) as a model species. Non‐begging behaviour was evaluated in the field by randomly assigning nestlings to a homogeneous (all sun) or heterogeneous (sun and shade) nest environment; measuring body temperature (Tb); and identifying behaviours from videotaped footage. The Tb of nestlings without access to shade was significantly higher, and nestlings spent more time moving and panting, suggesting an increased metabolic expenditure. To test this, we duplicated the insolation nanoclimate under laboratory conditions using a 1·0 KW Sciencetech Illumination System and measured the energetic cost of begging and non‐begging activity using open‐system respirometry on non‐irradiated and irradiated nestlings. Our results suggest that, in grackle nestlings, the relationship between activity (begging and non‐begging) and energy expenditure is context‐dependent. Our results identified: (i) a reduction in energy expenditure associated with accessing the shade; (ii) expenditure on non‐begging activity equalled or exceeded expenditure on begging activity; and (iii) a potential behavioural constraint on begging imposed by exposure to a homogeneous sun environment (sun without access to shade). The combination of context‐dependent costs and constraints suggests the potential for strategic costs associated with the heterogeneous nest environment.

Nest predation in an anthropogenic landscape

Wood Thrushes (Hylocichla mustelina) are experiencing widespread population declines. Knowing the relative contribution of predator species to overall rates of nest predation of Wood Thrushes, and understanding how the thrushes are affected by temporal and landscape factors, may be important elements in choosing and devising effective management strategies. We used miniature video cameras to identify nest predators of Wood Thrushes in a highly fragmented landscape in Ontario. Eleven species of birds and mammals were recorded as nest predators. Birds accounted for almost twice as many predation events as mammals, and three species – Brown-headed Cowbird (Molothrus ater), Cooper's Hawk (Accipiter cooperii), and raccoon (Procyon lotor) – accounted for the majority. Species such as American Crow (Corvus brachyrynchos), Blue Jay (Cyanocitta cristata), eastern gray squirrel (Sciurus carolinensis), and Common Grackle (Quiscalus quiscula) that are often speculated to be important nest predators in agricultural and suburban landscapes contributed little or nothing to overall predation rates. We tested hypotheses concerning effects of nest stage, time of nesting season, forest size, forest cover, urban housing pressure, and prior predation events at a nest on the probability of nest predation. Our models showed only two of these factors to be significant: prior predation at a nest increased the chance of a subsequent predation event and increasing the measure of urban pressure reduced the chance of a predation event. The many alternate and easy food sources associated with humans might divert the attention of potential predators from nesting birds in urban forests.

Helminths of Common Grackles, Quiscalus quiscula (Icteridae), Associated with a Fish Hatchery in Ohio, U.S.A

ABSTRACT: Six helminth species (1 digenetic trematode, Conspicuum icteridorum; 2 cestodes, Choanotaenia sp., and 1 tentatively identified as Paricterotaenia sp.; 3 nematodes, Capillaria ovopunctatum, Chandlerella quiscali, Porrocaecum ensicaudatum) were found in 35 common grackles, Quiscalus quiscula, Linnaeus, 1758, examined from a fish hatchery near London, Ohio, U.S.A., in late May through July 2009 and 2010. Porrocaecum ensicaudatum had the highest prevalence (77%) followed by C. ovopunctatum (66%). Chandlerella quiscali had the highest mean intensity (8.0) followed by C. ovopunctatum (6.4), which also had the highest mean abundance (4.2). Gravid worms of all helminth species were found except for Choanotaenia sp. The mean helminth species richness for all examined birds was 2.5 ± 1.0. This survey herein is consistent with previous parasitological studies conducted on the helminths of common grackles. Although 74% of the examined common grackles had fish bones in their gizzards, helminths known to ut...

Comparison of two models for estimating mortality from baitings with Compound DRC-1339 Concentrate avicide

In the U.S., DRC-1339 baitings for blackbirds (Icteridae) are generally done under the pesticide label, Compound DRC-1339 Concentrate – Staging Areas. DRC-1339 is a slow-acting avicide and gives the birds enough time to leave the baiting sites. Carcass searches and other forms of onsite counts are ineffective. Instead, linear models (LM) are used. The LM are based on esophageal analyses of several blackbird species collected while feeding at staging area bait sites. Biases and large variances can occur with this type of sampling. As an alternative to the LM, we developed a semi-mechanistic model (SM) that combined mechanistic modeling of environmental and biophysical processes with statistical modeling of DRC-1339 toxicities, avian physical and physiological traits, and foraging behavior. We used simulated baiting scenarios in Missouri and Louisiana to quantify and compare mortality between the LM and SM. The SM accounted for meteorological and regional effects on feeding rates, and we ran the SM scenarios for both mild and inclement weather conditions during January, a month when DRC-1339 baitings frequently occur. Mortality was calculated for males and females of three blackbird species. We used brown rice as the delivery substrate in a mix consisting of 11.34 kg untreated and 0.45 kg 2% DRC-1339 treated rice (1:25 dilution ratio). Compared to the LM, estimates by the SM ranged from 5% higher for male common grackles [Quiscalus quiscula L] to 59% lower for male brown-headed cowbirds [Molothrus ater Boddaert]. On average, the SM was 29% lower (x¯ = 8635, SE = 274.6) than the LM (x¯ = 12,131, SE = 1530.8, P < 0.001). Mortality estimates by the SM were 21% lower (x¯ = 7630, SE = 235.2, n = 12) under inclement than mild conditions (x¯ = 9641, SE = 276.3, P < 0.001). Latitudinal difference between the states did not affect mortality estimates produced by the SM (P > 0.65). Unlike the LM, the SM used avian physiological and behavioral responses to environmental and meteorological conditions based on individual characteristics of the modeled blackbird species. It represents a scientifically rigorous and broad-scale approach that can be applied at all staging area baitings regardless of region or time-of-year. The SM will produce much lower mortality estimates compared to the LM when brown-headed cowbirds are the major species using staging area sites.

The Culex pipiens Complex in the Mississippi River Basin: Identification, Distribution, and Bloodmeal Hosts

Members of the Culex pipiens complex are the primary vectors of St. Louis encephalitis virus and West Nile virus in the Mississippi River basin (MRB). The Cx. pipiens complex in the MRB is composed of 4 taxa: Cx. p. pipiens form pipiens, Cx. p. quinquefasciatus, hybrids between Cx. p. pipiens f. pipiens and Cx. p. quinquefasciatus, and Cx. p. pipiens form molestus. Three studies on bloodmeal hosts with large sample sizes have been conducted on members of the Cx. pipiens complex in the MRB including 1 each on Cx. p. quinquefasciatus from Louisiana, Cx. p. pipiens-quinquefasciatus hybrids from Tennessee, and Cx. p. pipiens from Illinois. The top 8 bloodmeal hosts from each of the 3 sites accounted for 68-92% of bloodmeals. Only 14 species accounted for the top 8 bloodmeal hosts at each of the 3 sites. The most often utilized bloodmeal hosts for members of the Culex pipiens complex within the MRB are the American robin, Northern cardinal, human, raccoon, common grackle, house sparrow, mourning dove, dog, Northern mockingbird, blue jay, opossum, domestic horse, house finch and European starling. Human feeding varied widely among sites from 1% to 15.7% of bloodmeals. The proportion of bloodmeals taken on humans is an important epidemiological variable and future studies are needed to define the primary genetic and environmental factors that influence host utilization by members of the Cx. pipiens complex.

Theoretical Potential of Passerine Filariasis to Enhance the Enzootic Transmission of West Nile Virus

Vertebrate reservoirs of arboviruses are often infected with microfilariae (MF). Laboratory studies have shown that MF can enhance the infectivity of arboviruses to mosquitoes. Soon after being ingested, MF penetrate the mosquito midgut. If the host blood also contains virus (i.e., vertebrate is dually infected), penetrating MF may introduce virus into the hemocoel. This can transform otherwise virus-incompetent mosquito species into virus-competent species and simultaneously accelerate viral development, allowing mosquitoes to transmit virus sooner than normal. This phenomenon is termed microfilarial enhancement of arboviral transmission. The prevalence of MF is very high in many passerine populations in North America. Therefore, we investigated if microfilarial enhancement could have facilitated the establishment and rapid spread of West Nile virus (WNV) across the mid-western United States. Our investigations revealed that mosquitoes, WNV, and passerine MF do interact in nature because; 1) 17% of 54 common grackles (Quiscalus quiscula L.), 8% of 26 American robins (Turdus migratorius L.), and 33% of three eastern kingbirds (Tyrannus tyrannus L.) were concurrently microfilaremic and seropositive to WNV; 2) feeding activities of mosquitoes overlapped temporally with the appearance of MF in the blood of common grackles; 3) mosquitoes fed on common grackles and American robins in nature; and 4) mosquito ingestion of two taxonomically distant species of passerine MF (i.e., Chandlerella quiscali and Eufilaria spp.) resulted in penetration of mosquito midguts. To estimate the theoretical effect that MF enhancement could have on WNV transmission in areas of high MF prevalence, vectorial capacity values were calculated for Culex mosquitoes feeding on common grackles, whereby MF enhancement was either invoked or ignored. For Cx. pipiens, vectorial capacity increased over three-fold when potential effects of MF were included in the calculations. For Cx. tarsalis, the effect was less (i.e., 1.4-fold increase). Closer attention should be paid to the potential of MF to enhance mosquito transmission of arboviruses.

Habitat selection and ranges of tolerance: how do species differ beyond critical thresholds?

Sensitivity to habitat fragmentation often has been examined in terms of thresholds in landscape composition at which a species is likely to occur. Observed thresholds often have been low or absent, however, leaving much unexplained about habitat selection beyond initial thresholds of occurrence, even for species with strong habitat preferences. We examined responses to varying amounts of tree cover, a widely influential measure of habitat loss, for 40 woodland bird species in a mixed woodland/grassland landscape in eastern North Dakota, USA. We used LOESS smoothing to describe incidence for each species at three scales: within 200, 400, and 1200 m around sample locations. For the 200-m scale, we also calculated the most-preferred range of tree cover (within which at least half of observations were predicted to occur) for each species. Only 10 of 40 species had occurrence thresholds greater than about 10% tree cover. After initial occurrence, species showed three general patterns: some increased monotonically with tree cover; some increased up to an asymptote; some peaked at intermediate amounts of tree cover and then declined. These patterns approximate selection for interior woodlands and for edge-rich environments, but incidence plots provide greater detail in landscape-scale selection than do those categories. For most species, patterns persisted at larger scales, but for some, larger scales had distinctly different patterns than local scales. Preferred ranges of tree cover varied from <20% tree cover (common grackle, Quiscalus quiscula) to >60% (veery, Catharus fuscescens). We conclude that incidence patterns provide more information on habitat selection than do threshold measures for most species: in particular, they differentiate species preferring concentrated woodlands from those preferring mixed landscapes, and they show contrasting degrees of selectiveness. [Correction added on 16 October 2012, after first online publication: the section has been reworded].

Discrepancy between factors affecting nestling growth and survival and maternal success in Common Grackles

Multiple factors potentially affect nestling survival and maternal reproductive success. However, little is known about the relative importance of different factors when operating simultaneously or whether the same factors are important for nestlings and their mothers. We determined the effect of hatching asynchrony, individual egg size, mean egg size, nestling sex, and clutch initiation date on the survival of individual nestlings and on maternal reproductive success in Common Grackles (Quiscalus quiscula) from 2004 to 2006 in central Illinois. Factors most important to maternal success differed from those important for individual nestling growth and survival. Hatching asynchrony had the greatest within-nest influence on the fate of nestlings; the earlier a nestling hatched relative to siblings, the greater its mass and likelihood of fledging. Clutch size had the greatest influence on maternal reproductive success, with females with larger clutches fledging more young. Thus, both nestling survival and maternal success were largely determined by a single, albeit different, factor. A possible explanation for the apparent unimportance of most factors we measured in determining maternal success is that we did not consider variation among females. Individual variation in maternal attributes such as condition, size, age, experience, or mate quality may result in females tailoring clutch attributes (i.e., egg size, sex, and degree of hatching asynchrony) in ways that allow them to maximize their reproductive success. The discordance between factors that benefited mothers versus their offspring illustrates the importance of considering the maternal consequences of any factor that appears to affect offspring survival. Factors that increase the mass and survival of some offspring may not result in increased maternal reproductive success. RESUMEN Potencialmente, muchos factores afectan la sobrevivencia de los pichones y el exito reproductivo maternal. Sin embargo, se sabe poco sobre la importancia relativa de diferentes factores que operan simultaneamente o si algunos factores, en particular, son importantes para los pichones y sus madres. Determinamos el efecto del eclosionamiento asincronico, tamano de los huevos, tamano promedio de los huevos, sexo del pichon e iniciacion de la camada en la sobrevivencia individual de pichones y en el exito reproductivo de las hembras de Quiscalus quiscula, en trabajo que se llevo a cabo en la parte central de Illinois de 2004 al 2006. Los factores mayor importancia para el exito de las madres difirieron de los factores mas importantes para el crecimiento y sobrevivencia de pichones particulares. La asincronia en el eclosionamiento tuvo la mayor influencia en el destino del pichon; entre mas temprano nace el pichon, en relacion a sus hermanos, mayor su masa corporal y probabilidad de volar. El tamano de la camada tuvo el mayor impacto en el exito reproductivo de las madres, produciendo mas volantones aquellas madres con camadas de mayor tamano. Por tanto, ambos, la sobrevivencia de los pichones y el exito maternal fueron mayormente determinados por un solo factor, pero diferente. Una posible explicacion para la aparente poca importancia de muchos otros factores, que medimos para determinar el exito maternal, es que no consideramos variaciones entre hembras. La variacion individual en atributos maternos tales como su condicion, tamano, edad, experiencia o calidad de su pareja pudieran permitir que la hembra atempere particularidades de la camada (ej. tamano del huevo, sexo, y grado de asincronia en el eclosionamiento), que a su efecto le permita maximizar su exito reproductivo. La discordancia entre factores que benefician a la madre versus sus hijos ilustra la importancia de considerar las consecuencias maternales de cualquier factor que parezca afectar la sobrevivencia de los pichones. Factores que incrementan la masa corporal y sobrevivencia de los pichones, no necesariamente resultan en un incremento en el exito maternal.

Coal fly ash basins as an attractive nuisance to birds: Parental provisioning exposes nestlings to harmful trace elements

Birds attracted to nest around coal ash settling basins may expose their young to contaminants by provisioning them with contaminated food. Diet and tissues of Common Grackle ( Quiscalus quiscala) nestlings were analyzed for trace elements to determine if nestlings were accumulating elements via dietary exposure and if feather growth limits elemental accumulation in other tissues. Arsenic, cadmium, and selenium concentrations in ash basin diets were 5× higher than reference diets. Arsenic, cadmium, and selenium concentrations were elevated in feather, liver, and carcass, but only liver Se concentrations approached levels of concern. Approximately 15% of the total body burden of Se, As, and Cd was sequestered in feathers of older (>5 days) nestlings, whereas only 1% of the total body burden of Sr was sequestered in feathers. Feather concentrations of only three elements (As, Se, and Sr) were correlated with liver concentrations, indicating their value as non-lethal indicators of exposure.

Absence of Wolbachia Endobacteria in Chandlerella quiscali, an Avian Filarial Parasite

Chandlerella quiscali is a filarial nematode parasite of the common grackle (Quiscalus quiscula), a widespread bird species found throughout most of North America. Worms collected from wild-caught birds were morphologically identified as C. quiscali and tested for the presence of Wolbachia, an alphaproteobacterial endosymbiont required for reproduction and maturation by many filarial species. Although various methods, including polymerase chain reaction, in situ hybridization, and immunohistology, were used, we were unable to detect evidence of colonization with Wolbachia. Due to the widespread distribution of the grackle host, localization within the host, and high prevalence, C. quiscali may be among the most easily obtainable of Wolbachia-free filarial species. Further studies of C. quiscali and other Wolbachia-free filarial species may help to clarify the reason(s) that some filarial species require Wolbachia but others do not.

Population changes of urban land birds in the three years following the hurricane Katrina flood

There are few studies of wildlife population dynamics in the wake of natural disasters, and little is known about “normal” rates and trajectories of their recovery. I document the population trajectories of ten urban resident land bird species in New Orleans, USA, over a 30 km network of survey transects in the 3.4 years following the Hurricane Katrina flood of September 2005 and compare them to transects surveyed before the storm in 1994–2000. The avian community in January 2009 differed from that before the storm, chiefly in the increased dominance of European Starlings (Sturnus vulgaris) and the near disappearance of the formerly common Northern Cardinal (Cardinalis cardinalis), Common Grackle (Quiscalis quiscula), and Bronzed Cowbird (Molothrus aeneus; at least through August 2007). In total, resident populations after 3.4 years were at less than half the levels recorded before the storm, having increased only weakly from their post-storm lows. Individual species varied widely in their population changes over the 3 years that followed their initial declines, some declining farther and others increasing by more than threefold. Starlings regained the highest proportion of their pre-storm numbers. The first and probably the second nesting seasons after the storm both saw resident bird populations increase substantially, but then decline again markedly by mid-winter.

Anthraquinone-based bird repellent for sunflower crops

Non-lethal alternatives are needed to manage bird damage to confectionery and oilseed sunflower crops ( Helianthus annuus). Ring-necked pheasants ( Phasianus colchicus) can cause localized damage to newly planted sunflower, and blackbirds (Icterids) damage ripening sunflower annually in the United States of America. We conducted seed germination experiments, a repellent efficacy study with ring-necked pheasants and Avipel ® repellent (a.i. 50% 9,10-anthraquinone), and laboratory and field efficacy studies with common grackles ( Quiscalus quiscula) and Avipel ®-treated confectionery sunflower. Compared to the germination of seeds not treated with anthraquinone, we observed no negative effects of up to 12,223 ppm, 14,104 ppm, and 11,569 ppm anthraquinone seed treatments for germination of confectionery sunflower, oilseed sunflower, and canola seeds, respectively. Pheasants avoided emergent sunflower seedlings (12 days post-planting) from 15,800 ppm anthraquinone seed treatments during a caged preference test ( P = 0.045). We observed a positive concentration–response relationship ( P = 0.001) and predicted a threshold concentration (i.e., 80% repellency) of 9200 ppm anthraquinone for common grackles offered Avipel ®-treated confectionery sunflower seeds. Grackles also reliably discriminated between untreated sunflower and seeds treated with 1300 ppm anthraquinone in captivity ( P < 0.001). During our field efficacy study for ripening confectionery sunflower, we observed 18% damage among anthraquinone-treated enclosures and 64% damage among untreated enclosures populated with common grackles ( P < 0.001). Harvested seed mass averaged 2.54 kg (dry weight) among treated enclosures and 1.24 kg among untreated enclosures ( P < 0.001). Our laboratory and field efficacy data provide a reliable basis for planning future field applications of anthraquinone-based repellents for protection of sunflower crops. Supplemental field efficacy studies are necessary for development of an effective avian repellent and management of avian depredation of ripening agricultural crops, including oilseed sunflower.