Field Flicker Research Articles

Neural Substrates for Early Data Reduction in Fast Vision: A Psychophysical Investigation.

To ensure survival, the visual system must rapidly extract the most important elements from a large stream of information. This necessity clashes with the computational limitations of the human brain, so a strong early data reduction is required to efficiently process information in fast vision. A theoretical early vision model, recently developed to preserve maximum information using minimal computational resources, allows efficient image data reduction by extracting simplified sketches containing only optimally informative, salient features. Here, we investigate the neural substrates of this mechanism for optimal encoding of information, possibly located in early visual structures. We adopted a flicker adaptation paradigm, which has been demonstrated to specifically impair the contrast sensitivity of the magnocellular pathway. We compared flicker-induced contrast threshold changes in three different tasks. The results indicate that, after adapting to a uniform flickering field, thresholds for image discrimination using briefly presented sketches increase. Similar threshold elevations occur for motion discrimination, a task typically targeting the magnocellular system. Instead, contrast thresholds for orientation discrimination, a task typically targeting the parvocellular system, do not change with flicker adaptation. The computation performed by this early data reduction mechanism seems thus consistent with magnocellular processing.

Understanding microchromosomal organization and evolution in four representative woodpeckers (Picidae, Piciformes) through BAC-FISH analysis.

The genome organization of woodpeckers has several distinctive features e.g., an uncommon accumulation of repetitive sequences, enlarged Z chromosomes, and atypical diploid numbers. Despite the large diversity of species, there is a paucity of detailed cytogenomic studies for this group and we thus aimed to rectify this. Genome organization patterns and hence evolutionary change in the microchromosome formation of four species (Colaptes campestris, Veniliornis spilogaster, Melanerpes candidus, and Picumnus nebulosus) was established through fluorescence in situ hybridization using bacterial artificial chromosomes originally derived from Gallus gallus and Taeniopygia guttata. Findings suggest that P. nebulosus (2n=110), which was described for the first time, had the most basal karyotype among species of Picidae studied here, and probably arose as a result of fissions of avian ancestral macrochromosomes. We defined a new chromosomal number for V. spilogaster (2n=88) and demonstrated microchromosomal rearrangements involving C. campestris plus a single, unique hitherto undescribed rearrangement in V. spilogaster. This comprised an inversion after a fusion involving the ancestral microchromosome 12 (homologous to chicken microchromosome 12). We also determined that the low diploid number of M. candidus is related to microchromosome fusions. Woodpeckers thus exhibit significantly rearranged karyotypes compared to the putative ancestral karyotype.

Gain Changes in Response to Full Field Flicker

Gain Changes in Response to Full Field Flicker

Multiple traits predict reproductive success and assortative mating in mutually ornamented Campo flickers (Colaptes campestris campestris)

Multiple traits predict reproductive success and assortative mating in mutually ornamented Campo flickers (Colaptes campestris campestris)

New, diagnostic flicker test for optic neuritis shows specific stages following disease onset

BackgroundPreviously, results of the digital flicker test (DFT) have shown distinct patterns in acute optic neuritis (ON) and healthy eyes. We aimed to examine the diagnostic potential of the DFT in acute ON and to investigate the temporal development of the DFT response following ON while comparing with visual evoked potentials (VEP). MethodsThe DFT examines the subjective brightness of a flickering field, varied in 11 different frequencies from 0 to 60 Hz, compared to a steady field. Previous studies have indicated a pronounced darkness enhancement at medial frequencies in acute ON eyes. Darkness enhancement at medial frequencies was expressed as a quantitative covariate (DFTDE). Results were compared with healthy controls and follow-up measurements were compared with VEP. Results112 patients were examined <31 days of onset (median 14.0 days (IQR:12.25)). 104 of 112 patients showed an abnormal flicker test (sensitivity 93%). DFT was abnormal in 2 of 55 healthy controls. The DFT showed normalization in 34% at 3 months, 36.4% at 6 months and 71.4% at >8 months from ON onset compared to 13.3%, 22.4% and 28.6% for VEP. Changes to the pattern of the DFT results were shown at specific stages during and following ON. ConclusionsThe DFT is an easy-to-use and sensitive diagnostic test for acute ON. The flicker test shows a more pronounced temporal evolution following ON than VEP and may be of use monitoring the course of ON.

Multi-scale nest survival analysis suggests new cavities improve nest success for the Green-barred Woodpecker, but not the Campo Flicker, in a threatened woodland of Argentina

Abstract Understanding factors affecting nest survival of woodpeckers in threatened landscapes is a key tool for land managers, particularly when conservation depends on public policies. However, information of Neotropical woodpeckers breeding in southern temperate forests is noticeably sparse despite the worrying conservation status of these ecosystems and woodpeckers’ key role as cavity providers. Our objective was to assess the relationship between tree cavity features, vegetation structure, and landscape configuration on the nest survival of the Green-barred Woodpecker (Colaptes melanochloros) and the Campo Flicker (C. campestris). We monitored nests of these woodpeckers during 3 breeding seasons from 2015 to 2018 in a woodland of east-central Argentina threatened by selective tree logging and soil material extraction. We recorded features that presumably influence nest survival at a micro-scale (cavity, cavity-tree features, and foliage cover around the cavity) and a macro-scale (forest cover and shape index within a 500-m circle around the nest). We did not find support for a relationship between daily nest survival rates (DSR) and cavity features, vegetation structure, or landscape configuration. However, new cavities were more successful than reused ones for the Green-barred Woodpecker. We also found a surprisingly high rate (~33% of nest failures) of nest abandonment for both species. Abandonment may be a factor regulating this population and causes of abandonment warrants further investigation. Given the importance of new cavities to the success of Green-barred Woodpeckers, our results indicate the preservation of medium-size trees (20 cm &amp;lt; diameter at breast height [DBH] &amp;lt; 50 cm) with wood softened by degradation processes (preferred by the species to excavate cavities) would facilitate persistence both of this woodpecker and the cavity nesting community. Effective audit of soil material extraction and controlled selective timber logging practices (including preservation of mature trees) in compliance with existing regulations could contribute to this type of habitat maintenance.

Wood density and tree size used as cues to locate and excavate cavities in two Colaptes woodpeckers inhabiting a threatened southern temperate forest of Argentina

Nest-site selection is crucial for birds' breeding success and, therefore, studies on this topic are critical in order to understand what features species need. This is particularly important in areas with conservation issues, where habitats and/or trees with the required features may be scarce. However, little information is available on the nest-site selection patterns of woodpeckers breeding in southern temperate forests, where tree logging considerably reduced forest cover and, hence, availability of trees suitable for cavity excavation. In addition, previous studies did not include assessments at different spatial scales nor including quantitative wood density data. Therefore, the main objective of this study is to assess nest-site selection patterns (at the habitat and cavity-tree scales) of the Campo Flicker Colaptes campestris and the Green-barred Woodpecker C. melanochloros breeding in a threatened southern temperate forest of central-east Argentina. Moreover, we report the first wood density data of the trees used by these two woodpeckers when excavating cavities and assess niche partitioning by comparing their cavities and cavity-trees to one another. To assess selection at a habitat scale (recording forest cover and edge of stands and trees), we compared selected breeding habitats to randomly found habitats. At a tree-scale (recording tree height, diameter, wood density and wood decay status), we compared cavity-trees to randomly found trees. Most cavities were excavated in medium (DBH = 20–35 cm) or large (>35 cm) size trees with wood density < 0.5 g/cm3. Generalized linear models indicated that woodpeckers’ propensity to excavate a new cavity was negatively correlated with tree wood density (which was negatively correlated to wood decay status) and positively to tree size. Both woodpecker species focused more importantly on tree features compared to habitat features when excavating cavities. Because forest patches containing mid- and large-sized trees with main stems and/or branches with wood softened by decay processes have become less abundant in these forests due to uncontrolled logging actions, we emphasize the need to conserve trees with these characteristics to ensure the availability of the preferred features of these woodpeckers.

Impacts of the invasive European Starling on two neotropical woodpecker species: agonistic responses and reproductive interactions

ABSTRACT The European Starling (Sturnus vulgaris) – hereafter ‘starling’ – has been introduced in many countries, and its South American population recently started expanding exponentially. This invasive species has a worldwide negative impact on the breeding performance of woodpeckers, competing for cavity use. Nevertheless, information is still lacking regarding southern temperate neotropical woodpeckers nest defence strategies and starling effects on woodpeckers’ breeding performance. We monitored Campo Flicker (Colaptes campestris) and Green-barred Woodpecker (Colaptes melanochloros) nests in a native southern temperate forest of central-eastern Argentina, to detect interactions with starlings and to assess the effect of starlings presence on woodpeckers’ breeding performance. We assessed whether woodpeckers perform defensive behaviours against the starlings by exposing taxidermied starling models to woodpecker breeding pairs. We detected interactions with starlings at 11% of the nests. These nests had a significantly higher probability of being abandoned during the early stages (until the third incubation day), compared to nests without interactions. Moreover, woodpeckers attacked and made distress calls more frequently in response to the presentation of the starling, compared to predator and non-competing species models. We also documented evidence of joint nesting, as four breeding pairs of woodpeckers shared their nest chamber with starlings. Our results indicate that neotropical woodpeckers are more likely to abandon their cavity when they interact with starlings. As the starling is expanding quickly in Argentina, this information points at the need to develop management programmes to control the impacts of this invasive species on the native fauna, especially on species with conservation concerns.

Visual snow syndrome: a review on diagnosis, pathophysiology, and treatment.

Visual snow is considered a disorder of central visual processing resulting in a perturbed perception of constant bilateral whole-visual field flickering or pixelation. When associated with additional visual symptoms, it is referred to as visual snow syndrome. Its pathophysiology remains elusive. This review highlights the visual snow literature focusing on recent clinical studies that add to our understanding of its clinical picture, pathophysiology, and treatment. Clinical characterization of visual snow syndrome is evolving, including a suggested modification of diagnostic criteria. Regarding pathophysiology, two recent studies tested the hypothesis of dysfunctional visual processing and occipital cortex hyperexcitability using electrophysiology. Likewise, advanced functional imaging shows promise to allow further insights into disease mechanisms. A retrospective study now provides Class IV evidence for a possible benefit of lamotrigine in a minority of patients. Scientific understanding of visual snow syndrome is growing. Major challenges remain the subjective nature of the disease, its overlap with migraine, and the lack of quantifiable outcome measures, which are necessary for clinical trials. In that context, refined perceptual assessment, objective electrophysiological parameters, as well as advanced functional brain imaging studies, are promising tools in the pipeline.

Management of retinitis pigmentosa by Wharton\u2019s jelly derived mesenchymal stem cells: preliminary clinical results

PurposeThe aim of this study is to determine if umbilical cord Wharton’s jelly derived mesenchymal stem cells implanted in sub-tenon space have beneficial effects on visual functions in retinitis pigmentosa patients by reactivating the degenerated photoreceptors in dormant phase.Material and methodsThis prospective, open-label, phase-3 clinical trial was conducted between April of 2019 and October of 2019 at Ankara University Faculty of Medicine, Department of Ophthalmology. 32 RP patients (34 eyes) were included in the study. The patients were followed for 6 months after the Wharton’s jelly derived mesenchymal stem cell administration, and evaluated with consecutive examinations. All patients underwent a complete routine ophthalmic examination, and best corrected visual acuity, optical coherens tomography angiography, visual field, multifocal and full-field electroretinography were performed. The quantitative results were obtained from a comparison of the pre-injection and final examination (6th month) values.ResultsThe mean best corrected visual acuity was 70.5 letters prior to Wharton’s jelly derived mesenchymal stem cell application and 80.6 letters at the 6th month (p = 0.01). The mean visual field median deviation value was 27.3 dB before the treatment and 24.7 dB at the 6th month (p = 0.01). The mean outer retinal thickness was 100.3 μm before the treatment and 119.1 μm at 6th month (p = 0.01). In the multifocal electroretinography results, P1 amplitudes improved in ring1 from 24.8 to 39.8 nv/deg2 (p = 0.01), in ring2 from 6.8 to 13.6 nv/deg2 (p = 0.01), and in ring3 from 3.1 to 5.7 nv/deg2 (p = 0.02). P1 implicit times improved in ring1 from 44.2 to 32.4 ms (p = 0.01), in ring2 from 45.2 to 33.2 ms (p = 0.02), and in ring3 from 41.9 to 32.4 ms (p = 0.01). The mean amplitude improved in 16 Tds from 2.4 to 5.0 nv/deg2 (p = 0.01) and in 32 Tds from 2.4 to 4.8 nv/deg2 (p = 0.01) in the full-field flicker electroretinography results. Full field flicker electroretinography mean implicit time also improved in 16 Tds from 43.3 to 37.9 ms (p = 0.01). No ocular or systemic adverse events related to the two types of surgical methods and/or Wharton’s jelly derived mesenchymal stem cells itself were observed during the follow-up period.ConclusionRP is a genetic disorder that can result in blindness with outer retinal degeneration. Regardless of the type of genetic mutation, sub-tenon Wharton’s jelly derived mesenchymal stem cell administration appears to be an effective and safe option. There are no serious adverse events or ophthalmic / systemic side effects for 6 months follow-up. Although the long-term adverse effects are still unknown, as an extraocular approach, subtenon implantation of the stem cells seems to be a reasonable way to avoid the devastating side effects of intravitreal/submacular injection. Further studies that include long-term follow-up are needed to determine the duration of efficacy and the frequency of application.Trial registrationSHGM56733164. Redistered 28 January 2019 https://shgm.saglik.gov.tr/organ-ve-doku-nakli-koordinatorlugu/56733164/203 E.507.

Sensitive Assessment of Acute Optic Neuritis by a New, Digital Flicker Test

Background: The Aulhorn flicker test (AFT) previously showed promise in diagnosing acute optic neuritis (ON) albeit with suboptimal sensitivity. A new, digitalized version of the AFT (the DFT) has not previously been examined in acute ON. Objectives: To examine the sensitivity, specificity and reproducibility of the DFT in acute ON. Method: The DFT assesses the subjective brightness of a flickering field (1–60 Hz). In normal subjects, brightness enhancement occurs at intermediate frequencies, whereas in acute ON darkness enhancement (DE) is hypothesized. AFT and DFT measurements were obtained in acute ON patients (≤31 days from first symptom) with DE as a quantitative covariate. Reproducibility of the DFT end point was assessed in the form of an intraclass correlation. Results: 30 untreated first-time acute ON patients and 55 healthy controls were examined. AFT and DFT were performed 12.7 days (range: 4–30) following ON onset. The DFT showed a sensitivity of 0.93 (95% CI = 0.78–0.99) to a specificity of 0.96 (95% CI = 0.87–1.00). The AFT showed a sensitivity of 0.76 (95% CI = 0.56–0.90) to a specificity of 1.00 (95% CI = 0.93–1.00). No significant correlation was shown between DFT and visual acuity. The intraclass correlation of the DFT end point in healthy subjects was 0.84. Conclusions: We present a new DFT in acute ON displaying a high specificity of 0.96 and a sensitivity of 0.93. Our study indicates the DFT to be an accurate and easy-to-use tool in diagnosing acute ON, which may be especially helpful in atypical cases.

Distribution of CR1-like transposable element in woodpeckers (Aves Piciformes): Z sex chromosomes can act as a refuge for transposable elements.

Birds have relatively few repetitive sequences compared to other groups of vertebrates; however, the members of order Piciformes (woodpeckers) have more of these sequences, composed mainly of transposable elements (TE). The TE most often found in birds is a retrotransposon chicken repeat 1 (CR1). Piciformes lineages were subjected to an expansion of the CR1 elements, carrying a larger fraction of transposable elements. This study compared patterns of chromosome distribution among five bird species, through chromosome mapping of the CR1 sequence and reconstructed their phylogenetic tree. We analyzed several members of Piciformes (Colaptes campestris, Colaptes melanochloros, Melanerpes candidus, and Veniliornis spilogaster), as well as Galliformes (Gallus gallus). Gallus gallus is the species with which most genomic and hence cytogenetic studies have been performed. The results showed that CR1 sequences are a monophyletic group and do not depend on their hosts. All species analyzed showed a hybridization signal by fluorescence in situ hybridization (FISH). In all species, the chromosomal distribution of CR1 was not restricted to heterochromatin regions in the macrochromosomes, principally pair 1 and the Z sex chromosome. Accumulation in the Z sex chromosomes can serve as a refuge for transposable elements. These results highlight the importance of transposable elements in host genomes and karyotype evolution.

Genetic diversity of Toxoplasma gondii isolates obtained from free-living wild birds rescued in Southeastern Brazil.

Recent studies carried out in Brazil have shown that strains from the same Toxoplasma gondii genotype can infect humans, domestic animals (dogs and cats) and animals slaughtered for human consumption (pigs, sheep, goats, and chickens), suggesting a common infection route. However, little is known about the importance of free-living wild birds within this epidemiological context. The objective of this work was to isolate, genotype, and evaluate the virulence for mice of new isolates of T. gondii obtained from free-living wild birds from the state of Minas Gerais, Southeastern Brazil. From August 2016 to June 2017, T. gondii was isolated from the hearts and brains collected from 6 out of 45 free-living wild birds, namely, a roadside hawk (Rupornis magnirostris), a campo flicker (Colaptes campestris), a southern caracara (Caracara plancus) and a tropical screech-owl (Megascops choliba), all rescued in Belo Horizonte. One isolate was obtained from a toco toucan (Ramphastos toco), rescued in Cristiano Otoni, and another was obtained from southern caracara, rescued in Santa Luzia. Five different genotypes were identified by PCR-RFLP. A unique genotype was shared in two different isolates obtained from a southern caracara and a toco toucan. This genotype has never been previously described in any other host or place. Three isolates were classified as of intermediary virulence and three isolates as avirulent for mice. The combined analysis of alleles ROP18/ROP5 (a serine/threonine kinase, and a polymorphic pseudokinase, respectively) was effective in determining the virulence of five of all the isolates with the exception of that from R. magnirostris. Atypical isolates of T. gondii obtained from free-living wild birds rescued in the state of Minas Gerais share the same genotypes of strains that infect humans, domestic animals, and animals slaughtered for human consumption.

Genomic Organization of Repetitive DNA in Woodpeckers (Aves, Piciformes): Implications for Karyotype and ZW Sex Chromosome Differentiation

Birds are characterized by a low proportion of repetitive DNA in their genome when compared to other vertebrates. Among birds, species belonging to Piciformes order, such as woodpeckers, show a relatively higher amount of these sequences. The aim of this study was to analyze the distribution of different classes of repetitive DNA—including microsatellites, telomere sequences and 18S rDNA—in the karyotype of three Picidae species (Aves, Piciformes)—Colaptes melanochloros (2n = 84), Colaptes campestris (2n = 84) and Melanerpes candidus (2n = 64)–by means of fluorescence in situ hybridization. Clusters of 18S rDNA were found in one microchromosome pair in each of the three species, coinciding to a region of (CGG)10 sequence accumulation. Interstitial telomeric sequences were found in some macrochromosomes pairs, indicating possible regions of fusions, which can be related to variation of diploid number in the family. Only one, from the 11 different microsatellite sequences used, did not produce any signals. Both species of genus Colaptes showed a similar distribution of microsatellite sequences, with some difference when compared to M. candidus. Microsatellites were found preferentially in the centromeric and telomeric regions of micro and macrochromosomes. However, some sequences produced patterns of interstitial bands in the Z chromosome, which corresponds to the largest element of the karyotype in all three species. This was not observed in the W chromosome of Colaptes melanochloros, which is heterochromatic in most of its length, but was not hybridized by any of the sequences used. These results highlight the importance of microsatellite sequences in differentiation of sex chromosomes, and the accumulation of these sequences is probably responsible for the enlargement of the Z chromosome.

Helping enhances productivity in campo flicker (Colaptes campestris) cooperative groups.

Reproductive adults in many bird species are assisted by non-breeding auxiliary helpers at the nest, yet the impact of auxiliaries on reproduction is variable and not always obvious. In this study, we tested Hamilton's rule and evaluated the effect of auxiliaries on productivity in the facultative cooperative breeder campo flicker (Colaptes campestris campestris). Campo flickers have a variable mating system, with some groups having auxiliaries and others lacking them (i.e., unassisted pairs). Most auxiliaries are closely related to the breeding pair (primary auxiliaries), but some auxiliaries (secondary auxiliaries) are unrelated females that joined established groups. We found no effect of breeder quality (body condition) or territory quality (food availability) on group productivity, but the presence of auxiliaries increased the number of fledglings produced relative to unassisted pairs. Nonetheless, the indirect benefit of helping was small and did not outweigh the costs of delayed breeding and so seemed insufficient to explain the evolution of cooperative breeding in campo flickers. We concluded that some ecological constraints must limit dispersal or independent breeding, making staying in the group a "best-of-a-bad-job" situation for auxiliaries.

Flicker adaptation or superimposition raises the apparent spatial frequency of coarse test gratings

Independent channels respond to both the spatial and temporal characteristics of visual stimuli. Gratings <3cycles per degree (cpd) are sensed by transient channels that prefer intermittent stimulation, while gratings >3cpd are sensed by sustained channels that prefer steady stimulation. From this we predict that adaptation to a spatially uniform flickering field will selectively adapt the transient channels and raise the apparent spatial frequency of coarse sinusoidal gratings. Observers adapted to a spatially uniform field whose upper or lower half was steady and whose other half was flickering. They then adjusted the spatial frequency of a stationary test (matching) grating on the previously unmodulated half field until it matched the apparent spatial frequency of a grating falling on the previously flickering half field. The adapting field flickered at 8Hz and the spatial frequency of the gratings was varied in octave steps from 0.25 to 16cpd. As predicted, adapting to flicker raised the apparent spatial frequency of the test gratings. The aftereffect reached a peak of 11% between 0.5 and 1cpd and disappeared above 4cpd. We also observed that superimposed 10Hz luminance flicker raised the apparent spatial frequency of 0.5cpd test gratings. The effect was not seen with slower flicker or finer test gratings. Altogether, our study suggests that apparent spatial frequency is determined by the balance between transient and sustained channels and that an imbalance between the channels caused by flicker can alter spatial frequency perception.

Frequency noise processes in a strontium ion optical clock

A recent comparison of the frequencies of a pair of optical clocks based on the 674 nm 2S1/2–2D5/2 optical clock transition in 88Sr+ has highlighted the need to understand factors affecting frequency instability. We have developed statistical models to show that our clock is capable of reaching the quantum projection noise limit; for our clock using 100 ms probe pulses, this is ∼3 × 10−15/√τ. However, this optical clock uses atomic transitions with a linear Zeeman shift, which can lead to a degradation in stability in the presence of magnetic field noise. We show that this generally leads to an increase in white frequency noise, even in cases dominated by magnetic field flicker or random walk noise. By taking into account both the quantum projection and magnetic field noise we are able to explain our observed frequency instabilities. This analysis will relate to any optical clock with a linear Zeeman shift where cancellation of this shift is achieved by interrogating pairs of components. Furthermore, implementing automatic control of lasers and minimization of micromotion requires pausing of the frequency servo occasionally; this leads to only a small degradation of frequency stability.

Towards an optimization of stimulus parameters for brain-computer interfaces based on steady state visual evoked potentials.

Efforts to construct an effective brain-computer interface (BCI) system based on Steady State Visual Evoked Potentials (SSVEP) commonly focus on sophisticated mathematical methods for data analysis. The role of different stimulus features in evoking strong SSVEP is less often considered and the knowledge on the optimal stimulus properties is still fragmentary. The goal of this study was to provide insight into the influence of stimulus characteristics on the magnitude of SSVEP response. Five stimuli parameters were tested: size, distance, colour, shape, and presence of a fixation point in the middle of each flickering field. The stimuli were presented on four squares on LCD screen, with each square highlighted by LEDs flickering with different frequencies. Brighter colours and larger dimensions of flickering fields resulted in a significantly stronger SSVEP response. The distance between stimulation fields and the presence or absence of the fixation point had no significant effect on the response. Contrary to a popular belief, these results suggest that absence of the fixation point does not reduce the magnitude of SSVEP response. However, some parameters of the stimuli such as colour and the size of the flickering field play an important role in evoking SSVEP response, which indicates that stimuli rendering is an important factor in building effective SSVEP based BCI systems.

Nestling use of alternative acoustic antipredator responses is related to immune condition and social context

Birds present a variety of antipredator responses, including the use of acoustic signals that may be directed to other individuals or to the predator. We tested competing hypotheses regarding antipredator responses by analysing patterns of variation in the use of distress calls in campo flicker, Colaptes campestris campestris, nestlings. More specifically, we tested whether immune response and social context (presence or absence of other individuals of the social group) were associated with variation in use of acoustic signals in response to human handling. Individuals with higher immunocompetence used proportionally more harsh, low-pitched calls (‘scream’ notes) than individuals with lower immunocompetence, while the latter used mostly tonal, high-pitched calls (‘week’ notes); in both cases there was no influence of the social context on call type. Individuals responded to the social context by giving fewer scream notes and week notes in the presence of adults of the social group than when the adults were absent. Although playbacks are necessary to determine the function of the calls, our results indicate that campo flicker nestling antipredator calls could be used to attract other individuals of the group to help defend the nestling. Also, the use of proportionally more scream notes by healthier individuals suggests that these notes could act as an honest signal of the nestlings’ physiological condition.

Experimental infection of one-day-old chicks with Salmonella Serotypes Previously isolated from poultry facilities, wild birds, and swine

In order to maintain the high production and export rates achieved by the Brazilian poultry industry, it is necessary to prevent and control certain disease agents, such as Salmonella spp. Using bacterial cultures, the aim of the present study was to investigate the prevalence of Salmonella spp. in specimens collected from broiler facilities. Local wild birds were also sampled, as well as the feces of swine housed on the poultry farm. After sample collection, the isolated serotypes were subsequently inoculated into broiler chicks to determine their effects. Positive samples were collected from the following locations in the poultry facilities: poultry litter (S. serotype 4,5,12:R:-; S. Heidelberg; S. Infantis), broiler feces (S. Heidelberg; S. serotype 6,7:R:-; S. serotype 4,5,12:R:-; S. Tennessee), water (S. Glostrup; S. serotype 6,8:d:-;), and lesser mealworms (Alphitobius diaperinus) found in the litter (S. Tennessee). Among the 36 wild birds captured, S. Heidelberg was isolated from one bird's organs and intestinal contents (Colaptes campestris), and S. Enteritidis was isolated from another bird's intestinal contents (Zenaida auriculata). Salmonella Panama and Salmonella Typhimurium were isolated from swine feces. One-day-old chicks (150) were divided into 10 groups of 15 animals each. Each group was orally inoculated with a previously isolated serotype of Salmonella. Soft stools were observed on the cage floor and around the birds' cloaca between 3 and 12 days post-infection (dpi). The different serotypes of Salmonella used to inoculate the chicks were re-isolated from the spleen, liver, and cecal content samples of the infected birds on 15 and 21 dpi.