Production of plumage ornaments among males and females of two closely related tropical passerine bird species

Autumn and winter time-energy budgets were constructed for brown thornbills, Acanthiza pusilla, and eastern yellow robins, Eopsaltria australis, inhabiting a temperate wet forest in south-eastern Australia. Birds spent 84-88% of daylight hours foraging in both seasons, but decreased the metabolic cost of other activity in winter by spending more time on energetically inexpensive behaviours. Estimated daily energy expenditures were either seasonally constant or increased (thornbill) or decreased (robin) in winter by no nore than l0%, depending on the assumed degree of substitution for the thermoregulatory requirement. Thornbills increased foraging efficiency in winter to compensate for the reduction in absolute foraging time. Less dramatic changes in behavioural strategies were required to achieve energy balance than have been recorded for many small north temperate birds. Brown thornbills used an energetically expensive, active search foraging technique to capture small, cryptic prey at a fast rate. Yellow robins employed an inexpensive, 'sit-and-wait' strategy to capture larger, more conspicuous prey at a slower rate. Both species had similar time investments in foraging, but allocated greatly differing proportions of energy to active foraging and resting alert. These contrasting strategies offer the potential for performing several activities simultaneously in the yellow robin and for reducing foraging and vigilance investments through exploiting gregariousness in the brown thornbill.

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Anti-predator behavior along elevational and latitudinal gradients in dark-eyed juncos

Current Zoology ◽

10.1093/cz/zoz046 ◽

2019 ◽

Vol 66 (3) ◽

pp. 239-245 ◽

Cited By ~ 2

Author(s):

Madelin Andrade ◽

Daniel T Blumstein

Keyword(s):

Human Impacts ◽

Bird Species ◽

Passerine Bird ◽

Latitudinal Gradients ◽

Junco Hyemalis ◽

Predator Density ◽

Elevational Gradients ◽

Main Driver ◽

Flight Initiation ◽

Predator Behavior

Abstract Flight-initiation distance (FID), the distance between an individual and experimenter when it begins to flee, can be used to quantify risk-assessment. Among other factors, prior studies have shown that latitude explains significant variation in avian FID: at lower latitudes, individuals and species have longer FIDs than those living at higher latitudes. No prior studies have focused on the effect of elevation on FID. Given the similar patterns of seasonality, climate, and potentially predator density, that covary between latitude and elevation, birds at higher elevations might tolerate closer approaches. We asked whether elevation or latitude would explain more variation in the FID of a common passerine bird species, dark-eyed juncos (Junco hyemalis). Juncos live in a variety of habitats along both latitudinal and elevational gradients. We found that statistical models containing elevation as a variable explained more of the variation in FID than did models containing latitude. We also found, unexpectedly, that birds at higher elevation fled at greater distances. While more predators were sighted per hour at higher elevations than at lower elevations, the frequency of predator sightings did not explain a significant amount of variation in FID. This result questions whether predator density is the main driver of risk perception along elevational gradients. Nonetheless, because elevation explains more variation in FID than latitude in at least one species, these findings have direct implications on how human impacts on birds are managed. Specifically, those designing set-back zones to reduce human impact on birds may consider modifying them based on both latitude and elevation.

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Evidence of breeding activity of subadult Turdus thrushes in Argentina

Revista Brasileira de Ornitologia ◽

10.1007/bf03544463 ◽

2019 ◽

Vol 27 (3) ◽

pp. 149-152

Author(s):

Exequiel Barboza ◽

Patricia Capllonch ◽

Fernando Diego Ortiz ◽

Alex E. Jahn

Keyword(s):

Population Dynamics ◽

Life History ◽

Bird Species ◽

Life History Strategies ◽

Brood Patch ◽

Breeding Condition ◽

Different Populations ◽

Males And Females ◽

Breeding Seasons ◽

Subadult Female

AbstractLittle is known about the age at which many Neotropical bird species first attempt to breed. We evaluated the breeding condition of 515 adult and subadult males and females among four species of Turdus thrushes (T. nigriceps, T. chiguanco, T. amaurochalinus and T. rufiventris) in Tucumán, Argentina during three breeding seasons (2015 to 2018). We registered a total of 126 individuals with brood patches and cloacal protuberances, which accounted for 24.5% of thrushes in breeding condition that we sampled. Forty thrushes had a brood patch (31.7% of those in breeding condition), of which 11 were subadults (8.7%). Eighty-six thrushes (68.3%) had a swollen cloacal protuberance, 18 of which were subadults (14.3%). Only a few of the subadults in breeding condition built nests, incubated eggs or raised nestlings. Of 130 nests we found, only 3 belonged to a subadult thrush (in all cases, a subadult female with an adult social mate), one of which was successful. Further research on these patterns among various Neotropical bird species could lead to important insights into the life history strategies that characterize different populations, and how these ultimately affect their population dynamics.

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Sex-Specific Selection Drives the Evolution of Alternative Splicing in Birds

Molecular Biology and Evolution ◽

10.1093/molbev/msaa242 ◽

2020 ◽

Cited By ~ 1

Author(s):

Thea F Rogers ◽

Daniela H Palmer ◽

Alison E Wright

Keyword(s):

Gene Expression ◽

Sex Differences ◽

Alternative Splicing ◽

Bird Species ◽

Gene Expression Level ◽

Expression Level ◽

Selection Pressures ◽

Specific Adaptation ◽

Beneficial Effects ◽

Males And Females

Abstract Males and females of the same species share the majority of their genomes, yet they are frequently exposed to conflicting selection pressures. Gene regulation is widely assumed to resolve these conflicting sex-specific selection pressures, and although there has been considerable focus on elucidating the role of gene expression level in sex-specific adaptation, other regulatory mechanisms have been overlooked. Alternative splicing enables different transcripts to be generated from the same gene, meaning that exons which have sex-specific beneficial effects can in theory be retained in the gene product, whereas exons with detrimental effects can be skipped. However, at present, little is known about how sex-specific selection acts on broad patterns of alternative splicing. Here, we investigate alternative splicing across males and females of multiple bird species. We identify hundreds of genes that have sex-specific patterns of splicing and establish that sex differences in splicing are correlated with phenotypic sex differences. Additionally, we find that alternatively spliced genes have evolved rapidly as a result of sex-specific selection and suggest that sex differences in splicing offer another route to sex-specific adaptation when gene expression level changes are limited by functional constraints. Overall, our results shed light on how a diverse transcriptional framework can give rise to the evolution of phenotypic sexual dimorphism.

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