Successive Pairs Research Articles

A translational rodent model of individual differences in sensitivity to the aversive properties of ethanol.

A strong relationship exists between individual sensitivity to the aversive properties of ethanol and risk for alcohol use disorder (AUD). Despite this, our understanding of the neurobiological mechanisms underlying the subjective response to ethanol is limited. A major contributor to this lack of knowledge is the absence of preclinical models that enable exploration of this individual variability such as is possible in studies of humans. Adult male and female Long-Evans rats were trained to associate a novel tastant (saccharin) with acute exposure to either saline or ethanol (1.5 g/kg or 2.0 g/kg i.p.) over three conditioning days using a standard conditioned taste aversion (CTA) procedure. Variability in sensitivity to ethanol-induced CTA was phenotypically characterized using a median split across the populations studied. When examining group averages, both male and female rats exposed to saccharin paired with either dose of ethanol exhibited lower saccharin intake relative to saline controls indicative of ethanol-induced CTA. Examination of individual data revealed a bimodal distribution of responses uncovering two distinct phenotypes present in both sexes. CTA-sensitive rats exhibited a rapid and progressive reduction in saccharin intake with each successive ethanol pairing. In contrast, saccharin intake was unchanged or maintained after an initial decrease from baseline levels in CTA-resistant rats. While CTA magnitude was similar between male and female CTA-sensitive rats, among CTA-resistant animals females were more resistant to the development of ethanol-induced CTA than males. Phenotypic differences were not driven by differences in baseline saccharin intake. These data parallel work in humans by revealing individual differences in sensitivity to the aversive properties of ethanol that emerge immediately after initial exposure to ethanol in both sexes. This model can be used in future studies to investigate the neurobiological mechanisms that confer risk for AUD.

A preliminary global investigation into potential impacts on successful captive breeding for two species of Rhyticeros hornbill.

Asian hornbills have limited ex situ breeding success, yet these species are some of the most threatened of birds, in need of managed breeding programs. To optimize breeding and increase the sustainability of such populations, it is necessary to assess and improve their husbandry and welfare. Evidence to improve reproduction can be gathered through global husbandry surveys. A survey was sent out to all European Association of Zoos and Aquaria and Association of Zoos and Aquarium holders of the wreathed hornbill (Rhyticeros undulatus) and Papuan hornbill (R. plicatus) to determine predictors for ex situ breeding success. This research found that pairs that have spent more years together (p = .016) and that adding additional proteins to the diet (p = .006) are two significant predictors of breeding success for wreathed- and Papuan hornbill pairs. This paper found a general trend that successful hornbill pairs prefer nest boxes that are situated outside (p = .054). The behaviors of calling to each other and sitting in close proximity showed a general trend and were observed more frequently in successful pairs and, therefore, could be good indicators of bonded pairs. We recommend that ex situ institutions allow their hornbill pairs time to form strong bonds, and that pair compatibility is monitored regularly to ensure that such interactions are positive and not consistently negative. An increase in the percentage of dietary proteins, priorand during the breeding season appears to stimulate pairs to breed. If the management and husbandry alterations presented in this study are implemented, the sustainability of Rhyticeros hornbill populations may be enhanced.

Factors Associated with Reproductive Success in Captive Vancouver Island Marmots (Marmota vancouverensis)

The Vancouver Island marmot (Marmota vancouverensis) is Canada’s most endangered endemic mammal. In 1997, a conservation breeding-for-release program was established to supplement wild marmot populations. Retrospective analyses of captive breeding studbook records since 2000 indicate the age of the sire and the dam significantly impacted the odds of successfully weaning a litter. Dams and sires between 5 and 7 years of age had more than double the odds of reproductive success compared to older animals. Successful reproduction by the dam in the previous year also doubled the odds of successfully weaning a litter in subsequent years. Assessment of adrenal function via fecal glucocorticoid analyses indicated established breeding pairs had decreased stress compared to new pairs (5.74 ± 0.28 ng/g vs. 7.60 ± 0.34 ng/g; p < 0.0001). Pairs that were ultimately successful at weaning pups in a breeding season had decreased stress compared to unsuccessful pairs (6.05 ± 0.34 ng/g vs. 7.22 ± 0.28 ng/g; p = 0.0006). These endocrine results suggest social buffering via familiarity and breeding/pair bond formation may be decreasing stress in established and successful pairs, respectively. The results of this study will be used to assist in the captive breeding management of this species to optimise numbers of animals produced to supplement the wild populations.

Vibrio fischeri: a model for host-associated biofilm formation.

Multicellular communities of adherent bacteria known as biofilms are often detrimental in the context of a human host, making it important to study their formation and dispersal, especially in animal models. One such model is the symbiosis between the squid Euprymna scolopes and the bacterium Vibrio fischeri. Juvenile squid hatch aposymbiotically and selectively acquire their symbiont from natural seawater containing diverse environmental microbes. Successful pairing is facilitated by ciliary movements that direct bacteria to quiet zones on the surface of the squid's symbiotic light organ where V. fischeri forms a small aggregate or biofilm. Subsequently, the bacteria disperse from that aggregate to enter the organ, ultimately reaching and colonizing deep crypt spaces. Although transient, aggregate formation is critical for optimal colonization and is tightly controlled. In vitro studies have identified a variety of polysaccharides and proteins that comprise the extracellular matrix. Some of the most well-characterized matrix factors include the symbiosis polysaccharide (SYP), cellulose polysaccharide, and LapV adhesin. In this review, we discuss these components, their regulation, and other less understood V. fischeri biofilm contributors. We also highlight what is currently known about dispersal from these aggregates and host cues that may promote it. Finally, we briefly describe discoveries gleaned from the study of other V. fischeri isolates. By unraveling the complexities involved in V. fischeri's control over matrix components, we may begin to understand how the host environment triggers transient biofilm formation and dispersal to promote this unique symbiotic relationship.

Laboratory evaluation of interspecific mating between Zeugodacus fruit flies and Bactrocera dorsalis

AbstractThe increasing number of tephritid pest invasions worldwide highlights the importance of interspecific interactions among tephritid pests. The melon fly [Zeugodacus cucurbitae (Coquillett)], the pumpkin fruit fly [Zeugodacus tau (Walker)], and the oriental fruit fly [Bactrocera dorsalis (Hendel)] (all Diptera: Tephritidae) are neotropical fruit flies with overlapping distributions. Their interactions during mating hours have rarely been observed in nature due to their nocturnal behavior. Here, laboratory studies were conducted under no‐choice and choice conditions to quantify interspecific mating. The interactions during mating hours resulted in interspecific mating, which reduced conspecific mating success and interrupted mating activity patterns. Successful interspecific mating pairs of Z. cucurbitae and Z. tau were recorded in no‐choice and choice tests. Interspecific mating between male Z. cucurbitae and female Z. tau significantly reduced conspecific mating in Z. tau. Observations of the diel mating activity patterns showed that male Z. cucurbitae initiated calling behaviors earlier than Z. tau males, giving Z. cucurbitae more chances to court Z. tau. Though males of neither Zeugodacus species formed mating pairs with B. dorsalis, Zeugodacus males reduced conspecific mating in B. dorsalis in the choice trials. Thus, interspecific interactions among Z. cucurbitae, Z. tau, and B. dorsalis affected conspecific mating; interrupted conspecific mating activity patterns were recorded in all three species. This information could be used to improve management practices.

Weight and protozoa number but not bacteria diversity are associated with successful pair formation of dealates in the Formosan subterranean termite, Coptotermes formosanus.

New colonies of Formosan subterranean termites are founded by monogamous pairs. During swarming season, alates (winged reproductives) leave their parental colony. After swarming, they drop to the ground, shed their wings, and male and female dealates find suitable nesting sites where they mate and become kings and queens of new colonies. The first generation of offspring is entirely dependent on the nutritional resources of the founder pair consisting of the fat and protein reserves of the dealates and their microbiota, which include the cellulose-digesting protozoa and diverse bacteria. Since termite kings and queens can live for decades, mate for life and colony success is linked to those initial resources, we hypothesized that gut microbiota of founders affect pair formation. To test this hypothesis, we collected pairs found in nest chambers and single male and female dealates from four swarm populations. The association of three factors (pairing status, sex of the dealates and population) with dealate weights, total protozoa, and protozoa Pseudotrichonympha grassii numbers in dealate hindguts was determined. In addition, Illumina 16S rRNA gene sequencing and the QIIME2 pipeline were used to determine the impact of those three factors on gut bacteria diversity of dealates. Here we report that pairing status was significantly affected by weight and total protozoa numbers, but not by P. grassii numbers and bacteria diversity. Weight and total protozoa numbers were higher in paired compared to single dealates. Males contained significantly higher P. grassii numbers and bacteria richness and marginally higher phylogenetic diversity despite having lower weights than females. In conclusion, this study showed that dealates with high body weight and protozoa numbers are more likely to pair and become colony founders, probably because of competitive advantage. The combined nutritional resources provided by body weight and protozoa symbionts of the parents are important for successful colony foundation and development.

Comparison of nestling diet between first and second broods of great tits Parus major in urban and forest habitats

To understand why early broods tend to be more successful than late broods we investigated the nestling diet and reproductive success of great tit pairs that had both a first and a second brood in the same breeding season. We found that in forest habitats great tit parents delivered similar composition and amount of food per nestlings throughout the breeding season, resulting in similar nestling body mass and survival in both first and second broods. In urban habitats, however, although parents provided similar amounts of food to the second broods they tended to deliver fewer caterpillars. In parallel with this, we observed lower nestling survival in second urban broods than in first broods even though the body mass of surviving nestlings was similar to that of the first broods. These findings suggest that although parents produce smaller second broods in both habitats, they are able to compensate for lower food availability in forest habitats but not in urban habitats, thus leading to reduced food quality and lower offspring survival in urban second broods.

Personality Characteristics Predictive of Social Pairing Outcome in Orange-Winged Amazon Parrots (Amazona amazonica)

ABSTRACT Most wild parrot species live in flocks, enriched by the environment and conspecific interactions. Captive parrots often live individually and are prone to behavioral maladaptation. If captive parrots and their behavior become intolerable, they are commonly relinquished to rescue organizations. This study aims to create parrot personality assessments for use by rescuers adding newly acquired parrots to shared environments. The study involved 20 orange-winged Amazon parrots (10 M, 10 F). Observers familiar with each bird scored its personality and analyses determined three sets of personalities: Social, Guarded, and Nervous Each parrot was paired with its 10 heterosexual counterparts and its interactions monitored remotely and captured on video. Pairing trials occurred over 72 hours in a specially designed pairing structure. Parrot personality could predict pairing success. Social-Guarded and Social-Nervous were more successfully paired, with individuals maintaining a close distance to one another and displaying increased rest-stretch behavior. Time of day influenced success with Social-Nervous pairs successful at all times of day, Social-Social pairs in the AM, and Guarded-Guarded pairs in the PM period. The study results suggest that rescues can use personality assessment and specific behaviors during cohabitation to predict OWA novel pairing outcomes.

Declining territory occupancy and productivity in a Welsh Red-billed Chough Pyrrhocorax pyrrhocorax population

ABSTRACT Capsule Much of the UK’s largest population of Red-billed Chough Pyrrhocorax pyrrhocorax shows long-term decline in territory occupancy and productivity. Underlying mechanisms need urgent study to improve conservation delivery for this species in Wales. Aims Periodic census data have shown a localized decline of Red-billed Choughs in Wales, which supported 66% of the UK breeding population in 2014. The aim is to explore the nature of this decline using long-term study data to search for patterns in territory occupancy and breeding performance. Methods Data from annual monitoring of breeding territories in mid- and north Wales, across 25 years and representing 74% of the Welsh population, were analysed to test for variation in occupancy and breeding metrics in relation to territory type, geographic region, and protection status. Results Most territories were coastal, where occupancy fell by 12%. Occupancy of inland territories fell by 72%, accounting for just 24% of territories by 2019. The number of chicks fledged per occupied territory fell by 25% across all territories, but the brood size of successful pairs only fell 9% with neither varying by territory type. Nest success rate fell 17% on the coast but 33% inland. Trends in occupancy and breeding metrics showed little variation between geographic regions and protection status. Conclusion The severe decline of inland nesting Red-billed Choughs could lead to rapid local extinction, but the slower decline in the coastal population is also of concern. Declining breeding performance is a plausible driver of population decline. As current conservation delivery appears ineffective, the mechanism of decline needs urgent study to identify necessary protection measures.

Breeders’ age, nest-site characteristics and climatic conditions but not density-dependent effects determine Bonelli’s Eagle breeding performance: A long-term study (2002–2021)

Abstract The conservation of endangered species is a crucial topic in conservation biology due to the important ecological roles these species play in their respective ecosystems. Top predators are particularly vulnerable to the variation in environmental conditions. The Bonelli’s Eagle (Aquila fasciata) is a long-lived bird of prey that fulfills its role as a top predator in Mediterranean ecosystems, but its overall population has declined in the Iberian Peninsula in recent decades. As with other long-lived species, the Bonelli’s Eagle reaches its maximum fitness at maturity, highlighting the importance of assessing how intrinsic and extrinsic factors affect population dynamics over time. In this study, we conducted annual surveys of a Bonelli’s Eagle subpopulation in the eastern Iberian Peninsula from 2002 to 2021. Our results indicate that the large decline observed in the number of occupied territories, fledged chicks, and successful pairs is not due to negative density-dependent effects but rather influenced by various environmental and demographic factors. These factors include breeders’ age, nest-site characteristics, climatic conditions, and previous breeding costs. We found that productivity was higher in territories with high winter precipitation and temperatures, as well as in coastal areas, leading to earlier laying dates. Additionally, the presence of subadult individuals in the breeding pair decreased breeding performance. Interestingly, the variability in the number of fledglings in each territory was driven by previous breeding costs. Prioritizing efforts to mitigate adult mortality and conserve suitable habitats becomes imperative to halt the ongoing decline of this population and also to enhance productivity, ultimately facilitating the restoration of the species to previous population levels.

Evaluation of Contrast Radiography and Computed Tomography in Sex Determination of Gila Monsters (Heloderma suspectum)

Abstract Sex determination in reptiles is important for implementing appropriate husbandry, successful pairing for breeding programs, and reproductive medical care. In reptile species that are not sexually dimorphic, accuracy in sex determination is dependent upon methods other than physical observation. Preferred sexing techniques should be quick, noninvasive, and reliable, and they should be able to be performed by veterinarians with a broad range of reptile experience. Vast anatomical differences among reptiles make the efficacy of these techniques highly variable between species. This study evaluated hemipenis contrast radiography and computed tomography techniques, previously described in other Heloderma species, to determine reliability in sexing 23 Gila monsters (Heloderma suspectum). The results were compared to the sex determined by coelomic ultrasound, which indicated that there were 8 females and 15 males. Identification of hemipenes in males was shown in 1/15 (7%) by contrast radiography and 9/15 (60%) by hemipenis contrast computed tomography. Outline of the cloacal rim in females was seen in 100% (8/8) by contrast radiography and 100% (8/8) by contrast computed tomography. Our findings suggest that contrast radiography and computed tomography are not reliable methods for sex determination in Gila monsters, and that coelomic ultrasound is currently the most reliable, noninvasive technique for this species.

Ultrafast Proton Transfer and Contact Ion-Pair Formation in Formic Acid Clusters.

The ultrafast proton transfer dynamics of homogeneous formic acid clusters (FA)n, n < 10, are investigated with femtosecond time-resolved mass spectrometry. We monitor the proton transfer pathway following Rydberg state electronic relaxation and find that successful ion pair formation increases logarithmically with cluster size. Ab initio calculations demonstrate similar excitation/relaxation behavior for each cluster, revealing a contact ion pair forms between two molecules composing the cluster before finally a formate anion (HCOO-) is dissociated by the probe pulse. The sub-ps time scale for rearrangement and proton transfer increases almost linearly with cluster size, requiring ∼67 fs per additional formic acid molecule and ranging from 213 ± 51 fs for the trimer to 667 ± 116 fs for FA9. The near-linear trends measured for both rearrangement lifetime and ion pair formation suggest that proton transfer is unlikely in the formic acid dimer but becomes prominent in small clusters.

Electronic effects of redox-active ligands on ruthenium-catalyzed water oxidation

The process of water oxidation presents a significant challenge in the development of artificial photosynthetic systems. This complexity arises from the necessity of charge accumulation, involving four electrons and four protons, and O–O bond formation. The strategy of using redox-active ligands in conjunction with metals is recognized as an effective approach for managing this charge accumulation process, attracting considerable attention. However, the detailed mechanisms by which the electronic effect of the redox-active ligands affect the reactivity of the catalytic centers remain ambiguous. In this study, the electronic effect of a series of mononuclear Ru complexes furnished with redox-active ligands ([(LRN5–)RuIII-OH]+, R = OMe, 3a; Me, 3b; H, 3c; F, 3d; CF3, 3e) was examined on water oxidation. A correlation was observed between redox potentials and substituent constants (σpara), indicating that different successive redox pairs are influenced by electron effects of varying intensities. Particularly, the ligand-centered oxidation (E {[(LN5–)+•RuIV=O]2+/[(LN5–)RuIV=O]+}) shows a greater dependence than the metal-centered PCET oxidations, E(RuIII-OH/RuII-OH2) and E(RuIV=O/RuIII-OH). The critical intermediate, [(LN5–)+•RuIV=O]2+, formed through ligand-centered oxidation, triggers O–O bond formation via its reaction with water. The rate constants of this crucial step can be effectively modulated by the substituents of the ligand. This study provides intricate insights into the role of the redox-active ligand in regulating the water oxidation process and further substantiates the effectiveness of the synergistic interaction of redox ligands and metals in controlling the multi-electron catalytic process.

Genomic dissection of endemic carbapenem resistance reveals metallo-beta-lactamase dissemination through clonal, plasmid and integron transfer

Infections caused by metallo-beta-lactamase-producing organisms (MBLs) are a global health threat. Our understanding of transmission dynamics and how MBLs establish endemicity remains limited. We analysed two decades of blaIMP-4 evolution in a hospital using sequence data from 270 clinical and environmental isolates (including 169 completed genomes) and identified the blaIMP-4 gene across 7 Gram-negative genera, 68 bacterial strains and 7 distinct plasmid types. We showed how an initial multi-species outbreak of conserved IncC plasmids (95 genomes across 37 strains) allowed endemicity to be established through the ability of blaIMP-4 to disseminate in successful strain-genetic setting pairs we termed propagators, in particular Serratia marcescens and Enterobacter hormaechei. From this reservoir, blaIMP-4 persisted through diversification of genetic settings that resulted from transfer of blaIMP-4 plasmids between bacterial hosts and of the integron carrying blaIMP-4 between plasmids. Our findings provide a framework for understanding endemicity and spread of MBLs and may have broader applicability to other carbapenemase-producing organisms.

Pupillometry in the follow-up of patients undergoing EVT - prediction of space-occupying hemispheric infarction

BackgroundDespite benefits of endovascular treatment (EVT) for large vessel occlusion (LVO) ischemic stroke, space-occupying brain edema (BE) represents a detrimental complication. In critical-care settings, CT-imaging is needed for monitoring these patients. Yet, bed-side techniques with the potential to predict whether patients develop BE or not would facilitate a time- and cost-efficient patient care. We assessed clinical significance of automated pupillometry in the follow-up of patients undergoing EVT.MethodsFrom 10/2018 to 10/2021, neurocritical-care-unit patients were retrospectively enrolled after EVT of anterior circulation LVO. We monitored parameters of pupillary reactivity [light-reflex-latency (Lat), constriction- and redilation-velocities (CV, DV), percentage-change-of-apertures (per-change); NeurOptics-pupilometer®] up to every hour on day 1–3 of ICU stay. BE was defined as midline shift ≥ 5 mm on follow-up imaging 3–5 days after EVT. We calculated mean values of intra-individual differences between successive pairs of parameters (mean-deltas), determined best discriminative cut-off values for BE development (ROC-analyses), and evaluated prognostic performance of pupillometry for BE development (sensitivity/specificity/positive-/negative-predictive-values).Results3241 pupillary assessments of 122 patients [67 women, 73 years (61.0–85.0)] were included. 13/122 patients developed BE. Patients with BE had significantly lower CVs, DVs, and smaller per-changes than patients without BE. On day 1 after EVT mean-deltas of CV, DV, and per-changes were significantly lower in patients with than without BE. Positive-predictive-values of calculated thresholds to discriminate both groups were considerably low, yet, we found high negative-predictive-values for CV, DV, per-changes, and mean-deltas (max.: 98.4%).ConclusionOur data suggest associations between noninvasively detected changes in pupillary reactivity and BE early after LVO-EVT. Pupillometry may identify patients who are unlikely to develop BE and may not need repetitive follow-up-imaging or rescue-therapy.

Breeding biology of Red-backed Shrikes (Lanius collurio): distribution, performance and post-fledging survival in Denmark

Agricultural intensification and habitat degradation across Europe have caused declines since the 20th century in populations of birds adapted to open landscapes, such as the Red-backed Shrike (Lanius collurio). Effective conservation strategies require knowledge on species’ breeding biology. To understand the status of the Danish breeding population better, we investigate which factors affect their breeding parameter (i.e. distribution, performance, post-fledging survival and behaviour). Our focus on the post-fledging period addresses present knowledge gaps due to the importance of this, yet under-studied, phase of passerines’ breeding cycle. We studied breeding pairs on different habitat types with Denmark-wide Citizen Science data, complemented by data of local projects in Northern Zealand and Northern Jutland (Denmark). Significantly fewer pairs were found in agricultural habitats and more in forests, semi-natural open habitats and synanthropic habitats. Pairs in forests had a significantly higher breeding productivity compared to agricultural or semi-natural open habitats for data from the years 2000 to 2021. Some project sites showed significantly higher number of fledglings compared to others, indicating that these sites are potential core areas for breeding productivity. Over the last two decades, the mean breeding productivity across Denmark was stable with 2.3 fledglings per successful pair. The survival rate of ringed fledglings increased during the post-fledging period, likely due to their increase in more active and independent behaviour. The relatively low breeding productivity found in this study calls for further studies including detailed data from potentially secondary habitats like agricultural areas to understand the effects of habitat on population fluctuations.

Lone male loser? Effects of spatial isolation on male pairing success in the Ortolan Bunting (Emberiza hortulana)

Cover photo: Male Ortolan Bunting. Photo: Frode Falkenberg. In small, isolated or fragmented bird populations, past studies have shown that there can be a high proportion of unpaired males. Low male pairing success is suggested to be the result of female-biased natal dispersal and low female recruitment. Indirect evidence indicates that such an effect operates among populations with different degrees of isolation, but little is known of how isolation affects male pairing success within populations. The Norwegian population of Ortolan Buntings (Emberiza hortulana) is distributed in about 50 discrete patches in an area of nearly 500 km2. In this study, we examined whether patch isolation and individual male isolation affected male pairing success. The population has a strongly male-biased sex ratio, with almost half of all males being unpaired. We found that male pairing successs was negatively related to isolation of patches and isolation of individual males in most analyses, and with significant effects in particular in some analyses of individual isolation. Patch population size was measured as the total number of males observed in a particular patch in a specific year and did not have an effect on male pairing success, and was not related to patch isolation. Even though some tests were statistically significant, the magnitude of effects were small and there was large variance in male pairing success. Variance in success suggests that other factors than isolation such as male age or experience may be just as important for male fitness within our study population. Furthermore, we suggest that small effects of isolation were due to the ability of Ortolan Buntings to move large distances within the breeding season, and that isolation effects on small spatial scales are more likely for species with restricted dispersal, such as resident species or species with high population density.

Steady state visual evoked potentials reveal a signature of the pitch-size crossmodal association in visual cortex

Crossmodal correspondences describe our tendency to associate sensory features from different modalities with each other, such as the pitch of a sound with the size of a visual object. While such crossmodal correspondences (or associations) are described in many behavioural studies their neurophysiological correlates remain unclear. Under the current working model of multisensory perception both a low- and a high-level account seem plausible. That is, the neurophysiological processes shaping these associations could commence in low-level sensory regions, or may predominantly emerge in high-level association regions of semantic and object identification networks. We exploited steady-state visual evoked potentials (SSVEP) to directly probe this question, focusing on the associations between pitch and the visual features of size, hue or chromatic saturation. We found that SSVEPs over occipital regions are sensitive to the congruency between pitch and size, and a source analysis pointed to an origin around primary visual cortices. We speculate that this signature of the pitch-size association in low-level visual cortices reflects the successful pairing of congruent visual and acoustic object properties and may contribute to establishing causal relations between multisensory objects. Besides this, our study also provides a paradigm can be exploited to study other crossmodal associations involving visual stimuli in the future.

Are the Steps on Likert Scales Equidistant? Responses on Visual Analog Scales Allow Estimating Their Distances.

A recurring question regarding Likert items is whether the discrete steps that this response format allows represent constant increments along the underlying continuum. This question appears unsolvable because Likert responses carry no direct information to this effect. Yet, any item administered in Likert format can identically be administered with a continuous response format such as a visual analog scale (VAS) in which respondents mark a position along a continuous line. Then, the operating characteristics of the item would manifest under both VAS and Likert formats, although perhaps differently as captured by the continuous response model (CRM) and the graded response model (GRM) in item response theory. This article shows that CRM and GRM item parameters hold a formal relation that is mediated by the form in which the continuous dimension is partitioned into intervals to render the discrete Likert responses. Then, CRM and GRM characterizations of the items in a test administered with VAS and Likert formats allow estimating the boundaries of the partition that renders Likert responses for each item and, thus, the distance between consecutive steps. The validity of this approach is first documented via simulation studies. Subsequently, the same approach is used on public data from three personality scales with 12, eight, and six items, respectively. The results indicate the expected correspondence between VAS and Likert responses and reveal unequal distances between successive pairs of Likert steps that also vary greatly across items. Implications for the scoring of Likert items are discussed.

Factors influencing incubation behavior and nesting success of yellow‐billed loons in Arctic Alaska

AbstractReductions in nest attendance can increase predation risk and, therefore, reduce nesting success of ground‐nesting birds. We recorded the incubation behavior, nest predators, and nesting success of yellow‐billed loons (Gavia adamsii) at 2 adjacent study areas with differing amounts of industrial activity on the Arctic Coastal Plain of Alaska, USA, during 2008–2015 and 2019. Successful pairs had higher incubation constancies (97.3 ± 1.7% [SE], n = 96 nests) than failed pairs (91.6 ± 3.1%, n = 79 nests) and took fewer and shorter recesses than failed pairs. The intrusion of conspecifics into territories significantly lowered the daily incubation constancy of nesting pairs. Daily incubation constancy also declined as the daily maximum temperature increased, especially during periods with little wind. Both conditions contributed to nest failure. Predation was the primary cause of nest failure, with glaucous gulls (Larus hyperboreus) and parasitic jaegers (Stercorarius parasiticus) accounting for 41% of the nest failures. These avian predators took advantage of unattended nests, underscoring the consequence of disrupting incubation behavior. In both study areas, nest survival decreased as recess frequency increased. In the Colville Delta study area, loons with territories composed of separate nesting and brood‐rearing lakes had lower nest survival than loons that used 1 lake for both activities. In the National Petroleum Reserve‐Alaska study area (NPR‐A), loons nesting on shorelines and peninsulas had lower nest survival than those nesting on islands and nest survival decreased as the proportion of days with intruders increased. The overall probability of a nest hatching ≥1 egg in the Colville Delta study area was 0.40 (95% CI = 0.26–0.54) and was 0.68 (95% CI = 0.40–0.91) in the NPR‐A study area. Our results demonstrate the importance of nest attendance by yellow‐billed loons in warding off nest predators on the Arctic Coastal Plain of Alaska and provide a mechanism that shows how a warming Arctic climate could negatively affect yellow‐billed loons.