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opencc-zeroOct 2022View details →

Flagellum tapering and midpiece volume in songbird spermatozoa

In contrast to numerous studies on spermatozoa length, relatively little work focuses on the width of spermatozoa, particularly the width of the midpiece and flagellum. In flagellated spermatozoa, the flagellum provides forward thrust while energy may be provided via mitochondria in the midpiece and/or through glycolysis along the flagellum itself. Longer flagella may be able to provide greater thrust but may also require stronger structural features and more or larger mitochondria to supply sufficient energy. Here we use SEM imaging to investigate the ultrastructure of spermatozoa from 55 passerine species in 26 taxonomic families in the Passerides infraorder. Our data confirm the qualitative observation that the flagellum tapers along its length, and we show that longer flagella are wider at the neck. This pattern is similar to mammals, and likely reflects the need for longer cells to be stronger against shearing forces. We further estimate the volume of the mitochondrial helix and show that it correlates well with midpiece length, supporting the use of midpiece length as a proxy for mitochondrial volume, at least in between-species studies where midpiece length is highly variable. These results provide important context for understanding the evolutionary correlations among different sperm cell components and dimensions.

opencc-by-4.0Nov 2022View details →

Supplementary material to "Habitat detection, habitat choice copying, or mating benefits: what drives conspecific attraction in a nomadic songbird?"

Abstract <ol> <li>Conspecific attraction during habitat selection is common among animals, but the ultimate (i.e., fitness-related) reasons for this behavior often remain enigmatic.</li> <li>We aimed to evaluate the following three hypotheses for conspecific attraction during the breeding season in male Wood Warblers (Phylloscopus sibilatrix): the habitat detection hypothesis, the habitat choice copying hypothesis, and the female preference hypothesis. These hypotheses make different predictions with respect to the relative importance of social and non-social information during habitat assessment, and whether benefits accrue as a consequence of aggregation.</li> <li>We tested the above hypotheses using a combination of a two-year playback experiment, spatial statistics and mate choice models.</li> <li>The habitat detection hypothesis was the most likely explanation for conspecific attraction and aggregation in male Wood Warblers, based on the following results: 1) males were attracted to conspecific song playbacks, but fine-scale habitat heterogeneity was the better predictor of spatial patterns in the density of settling males; 2) male pairing success did not increase, but instead slightly decreased, as connectivity with other males (i.e., the number and proximity of neighboring males) increased.</li> <li>Our study highlights how consideration of the process by which animals detect and assess habitat, together with the potential fitness consequences of resulting aggregations, are important for understanding conspecific attraction and spatially clustered distributions.</li> </ol>

opencc-zeroNov 2022View details →

Data for: Similar environmental cues guide timing of breeding and seasonal shifts in songbird social structure

Seasonally breeding animals often exhibit different social structures during non-breeding and breeding periods that coincide with seasonal environmental variation. Therefore, ongoing climate change may play an important role in determining the future structure of animal societies, especially if climate determines when seasonal shifts in social structure occur. However, we know little about the environmental cues that determine the timing of seasonal shifts in social structure, a lack of knowledge that contrasts with our well-defined knowledge of the environmental cues that trigger a shift to breeding physiology in seasonally breeding species. Here we tested whether the environmental cues that drive seasonal shifts in social structure are similar to those that determine timing of breeding in the red-backed fairywren (Malurus melanocephalus), an Australian songbird. Social network analyses revealed that social groups, which are highly territorial during the breeding season, interact in social "communities" on larger ranges during the non-breeding season. Interactions among non-breeding groups were related to rainfall, with more rainfall leading to reductions in home range size and fewer interactions among non-breeding social groups. Similarly, onset of breeding was also determined by rainfall during the non-breeding season, with greater rainfall leading to earlier breeding. These findings reveal that for some species, the cues that determine the timing of shifts in social structure across seasonal boundaries can be similar to those that determine timing of breeding. This study increases our understanding of how social structure and the selection pressures that result from different social structures might respond to changing climates.

opencc-zeroJan 2023View details →

High virulence is associated with pathogen spreadability in a songbird-bacterial system

How directly-transmitted pathogens benefit from harming hosts is key to understanding virulence evolution. It is recognized that pathogens benefit from high within-host loads, often associated with virulence. However, high virulence may also directly augment spread of a given amount of pathogen, here termed "spreadability". We used house finches and the conjunctival pathogen Mycoplasma gallisepticum to test whether two components of virulence– the severity of conjunctival inflammation and behavioral morbidity produced– predict pathogen spreadability. We applied ultraviolet powder around the conjunctiva of finches that were inoculated with pathogen treatments of distinct virulence and measured within-flock powder spread, our proxy for "spreadability". When compared to uninfected controls, birds infected with a high-virulence, but not low-virulence, pathogen strain, spread significantly more powder to flockmates. Relative to controls, high-virulence treatment birds both had more severe conjunctival inflammation– which potentially facilitated powder shedding– and longer bouts on feeders, which serve as fomites. However, food peck rates and displacements with flockmates were lowest in the high-virulence treatment relative to controls, suggesting inflammatory rather than behavioral mechanisms likely drive augmented spreadability at high virulence. Our results suggest that inflammation associated with virulence can facilitate pathogen spread to conspecifics, potentially favoring virulence evolution in this system and others.

opencc-by-4.0Jan 2023View details →

RoboFinch: a versatile audio-visual synchronized robotic bird model for laboratory and field research on songbirds

Raw data and R script for the behavioral data published in the Journal Methods in Ecology and Evolution with the title: RoboFinch: a versatile audio-visual synchronized robotic bird model for laboratory and field research on songbirds All data and source files for the RoboFinch construction can be found here:  https://doi.org/10.5281/zenodo.7520589

opencc-zeroDec 2022View details →

High heterogeneity in genomic differentiation between phenotypically divergent songbirds: A test of mitonuclear co-introgression

Comparisons of genomic variation among closely related species often show more differentiation in mitochondrial DNA (mtDNA) and sex chromosomes than in autosomes, a pattern expected due to the differing effective population sizes and evolutionary dynamics of these genomic components. Yet, introgression can cause species pairs to deviate dramatically from general differentiation trends. The yellowhammer (Emberiza citrinella) and pine bunting (E. leucocephalos) are hybridizing avian sister species that differ greatly in appearance and moderately in nuclear DNA, but that show no mtDNA differentiation. This discordance is best explained by adaptive mtDNA introgression—a process that can select for co-introgression at nuclear genes with mitochondrial functions (mitonuclear genes). To better understand these discordant differentiation patterns and characterize nuclear differentiation in this system, we investigated genome-wide differentiation between allopatric yellowhammers and pine buntings and compared it to what was seen previously in mtDNA. We found significant nuclear differentiation that was highly heterogeneous across the genome, with a particularly wide differentiation peak on the sex chromosome Z. We further investigated mitonuclear gene co-introgression between yellowhammers and pine buntings and found support for this process in the direction of pine buntings into yellowhammers. Genomic signals indicative of co-introgression were common in mitonuclear genes coding for subunits of the mitoribosome and electron transport chain complexes. Such introgression of mitochondrial DNA and mitonuclear genes provides a possible explanation for the patterns of high genomic heterogeneity in genomic differentiation seen among some species groups.

opencc-zeroMar 2023View details →

Data for: Emigration and survival correlate with different precipitation metrics throughout a grassland songbird's annual cycle

Many exogenous factors may influence demographic rates (i.e., births, deaths, immigration, emigration), particularly for migratory birds that must cope with variable weather and habitat throughout their range and annual cycle. In midcontinental grasslands, disturbance (e.g., fire and grazing) and precipitation influence variation in grassland structure and function, but we know little about when and why precipitation is associated with grassland species' vital rates. We related estimates of detection, survival, and emigration to a priori sets of precipitation metrics to test the putative alternative factors influencing movement and mortality in grasshopper sparrows (Ammodramus savannarum). This species is a migratory songbird that exhibits exceptionally high rates of within-season and between-season dispersal. Between 2013 and 2020, we captured and resighted grasshopper sparrows in northeastern Kansas, USA, compiling capture histories for 1,332 adult males. We tested predictions of climatic hypotheses explaining variation in survival and emigration throughout a grasshopper sparrow's annual cycle; both survival and emigration were associated with the El Niño-Southern Oscillation precipitation index (ESPI). Survival was positively related with ESPI during winter, and temporary emigration was curvilinearly related to breeding season ESPI lagged 2 years, with the highest site fidelity associated with intermediate rainfall values. The relationship between rainfall and temporary emigration likely reflects the influence of weather over multiple years on vegetation structure with consequent effects on local demography. This study provides compelling support for the idea that grassland species respond to high interannual variability by adopting dispersal strategies unlike those of many well-studied migrant birds. Furthermore, the results imply that the consequences of increasing climatic extremes may not be immediately apparent, with demographic consequences lasting for at least a few years.

opencc-zeroJul 2023View details →

Data for: Early life conditions influence fledging success and subsequent local recruitment rates in a declining migratory songbird, the Whinchat Saxicola rubetra

<ol> <li>Life history traits and environmental conditions influence reproductive success in animals, and consequences of these can influence subsequent survival and recruitment into breeding populations. Understanding influences on demographic rates is required to determine the causes of decline. Migratory species experience spatially and temporally variable conditions across their annual cycle, making identifying where the factors influencing demographic rates operate challenging.</li> <li>Here, we use the Whinchat Saxicola rubetra as a model declining long-distance migrant bird. We analyse 10 years of data from 247 nesting attempts and 2519 post-fledging observations of 1193 uniquely marked nestlings to examine the influence of life history traits, habitat characteristics and weather on survival of young from the nestling stage to local recruitment into the natal population.</li> <li>We detected potential silver spoon effects where conditions during the breeding stage influence subsequent apparent local recruitment rates, with higher recruitment for fledglings from larger broods, and recruitment rate negatively related to rainfall that chicks experienced in-nest. Additionally, extreme temperatures experienced pre- and post-fledging increased fledging success and recruitment rate. However, we could not determine whether this was driven by temperature influencing mortality during the post-fledging period or later in the annual cycle.</li> <li>Brood size declined with hatching date. In-nest survival increased with brood size and was highest at local temperature extremes. Furthermore, nest survival was highest at nests surrounded with 40–60% vegetation cover of Bracken Pteridium aquilinum within 50m of the nest.</li> <li>Our results show that breeding phenology and environmental factors may influence fledging success and recruitment in songbird populations, with conditions experienced during the nestling stage influencing local recruitment rates in Whinchats (i.e. silver spoon effect). Recruitment rates are key drivers of songbird population dynamics. Our results help identify some of the likely breeding season mechanisms that could be important population drivers.</li> </ol>

opencc-zeroSep 2023View details →

Data from: Songbird species that display more-complex vocal learning are better problem-solvers and have larger brains

Complex vocal learning, a critical component of human spoken language, has been assumed to be associated with more-advanced cognitive abilities. Tests of this hypothesis between individuals within a species have been inconclusive and have not been done across species. In this work, we measured an array of cognitive skills - namely problem-solving, associative and reversal learning, and self-control - across 214 individuals of 23 bird species, including 19 wild-caught songbird species and two vocal nonlearning species. We found that the greater the vocal learning abilities of a species, the better their problem-solving skills and the relatively larger their brains. These conclusions held when controlling for non-cognitive variables and phylogeny. Our results support a hypothesis of shared genetic and cognitive mechanisms between vocal learning, problem-solving, and bigger brains in songbirds.

opencc-by-4.0Sep 2023View details →

Manipulation of photoperiod induces fat storage, but not fat mobilization in the migratory songbird, Dumetella carolinensis (Gray Catbird) 1.

Datasets for "Manipulation of photoperiod induces fat storage, but not fat mobilization in the migratory songbird, Dumetella carolinensis (Gray Catbird)" publication in the Journal of Comparative Physiology B.

Figure 4 in Natural noise affects conspecific signal detection and territorial defense behaviors in songbirds

Figure 4 Spotted towhee predictors from the AICc top model for PC1approach (a), PC2fly (b), and PC3song (c). (a) Towhees approach more slowly and maintain a greater distance from the speaker as sound level increases. Shading represents 95% CI and rug plot denotes sound level of individual trials. California spotted towhees fly more frequently on control trials (b) and display a weaker song response during treatment-off trials (c) than on all other trials, within and among populations (see [a] for color legend). (b–c) Violins denote kernel density probabilities differentiated by trial type (x axis) and population (color), with means (±1 SE) connected by dotted line; boxplots denote median and quartiles, and whiskers show 1.5 times the interquartile range; points represent individual trials; and asterisks denote significant contrasts corresponding to 95% CIs (see Supplementary Appendix Table A3 for values). Data displayed as untransformed components.

Figure 2 in Natural noise affects conspecific signal detection and territorial defense behaviors in songbirds

Figure 2 Site design schematic of Idaho and California study areas. Tripods represent loudspeaker setups. aAny trial with chorusing cicadas was counted as cicada treatment, regardless of the trial type (treatment-on, treatment-off, control). bControl sites had the same layout as treatment sites, but with mock loudspeaker setups. cWe excluded cicada trials from analysis for spotted towhees due to low sample size.

Figure 3 in Natural noise affects conspecific signal detection and territorial defense behaviors in songbirds

Figure 3 Lazuli bunting predictors from the AICc top model for PC1fly (a) and PC3approach (b) response variables. (a) Buntings fly more as sound level increases in the presence of cicada noise (dashed line) and fly less as sound level increases in the absence of cicada noise (solid line). Rug plot indicates sound level for individual trials differentiated by presence/absence of cicadas (see [b] for color legend). (b) As sound level increases, buntings approach the conspecific speaker more slowly and maintain a greater distance from it. (a & b) Shaded bands denote 95% CIs. Data displayed as untransformed components.

Figure 1 in Natural noise affects conspecific signal detection and territorial defense behaviors in songbirds

Figure 1 Spectrograms (a) of spotted towhee song (left) and lazuli bunting song (right) in quiet control conditions. (b) Power spectra of the three treatments are overlayed with bunting and towhee song power spectra. Power spectra are normalized to a relative peak amplitude of 70 dB (re 1 dimensionless sample units). Treatment noise and song spectra overlap substantially, suggesting high masking potential.