Biology subjects

Baldassarre, D. T.

Publications and source records attributed to Baldassarre, D. T..

6 recordsLinked to original sources

bioRxiv2026

Colorful connections: pigment-based plumage and breeding condition are associated with gut microbiome variation in the Common Yellowthroat

Carotenoid- and melanin-based plumage coloration traits are key signals in avian communication and sexual selection as they are often thought to provide "honest" information about individual condition and fitness. These traits arise through distinct but interconnected physiological and genetic pathways. Recent work suggests that there may be a link between host-associated gut microbiota and the functional pathways leading to pigment-based plumage coloration, but this remains largely unexplored in wild populations. To address this gap, we tested whether variation in plumage coloration, as well as breeding condition, is associated with gut microbiome variation in wild populations of male Common Yellowthroats (Parulidae: Geothlypis trichas). We quantified multiple plumage coloration traits and characterized gut microbiome bacterial diversity using 16S rRNA metabarcoding. Through a comprehensive modeling framework, we found that individuals with brighter, more orange-tinted breast feathers and smaller cloacal protuberances (a proxy for breeding condition) exhibited higher gut microbiome diversity. At the taxonomic level, Methylobacterium-Methylorubrum, a carotenoid-producing bacteria, showed strong associations with multiple plumage traits, including mask area, breast feather hue, and saturation. Our results demonstrate that gut microbiome diversity is associated with variation in carotenoid-based coloration traits and breeding condition in Common Yellowthroats. More broadly, these results highlight the potential for host-microbiome interactions to shape phenotypic variation through physiological pathways in wild animal populations.

ecology↗

bioRxiv2024

Bird Name-a-thon: Categorizing English bird names using crowdsourcing

Common names of species are important for communicating with the general public. In principle, these names should provide an accessible way to engage with and identify species. The common names of species have historically been labile without standard guidelines, even within a language. Currently, there is no systematic assessment of how often common names communicate identifiable and biologically relevant characteristics about species. This is a salient issue in ornithology, where common names are used more often than scientific names for species of birds in written and spoken English, even by professional researchers. To gain a better understanding of the types of terminology used in the English-language common names of bird species, a group of 85 professional ornithologists and non-professional contributors classified unique descriptors in the common names of all recognized species of birds. In the AvianLexiconAtlas database produced by this work, each species common name is assigned to one of ten categories associated with aspects of avian biology, ecology, or human culture. Across 10,906 species of birds, 89% have names describing the biology of the species, while the remaining 11% of species have names derived from human cultural references, human names, or local non-English languages. Species with common names based on features of avian biology are more likely to be related to each other or be from the same geographic region. The crowdsourced data collection also revealed that many common names contain specialized or historic terminology unknown to many of the data collectors, and we include these terms in a glossary and gazetteer alongside the dataset. The AvianLexiconAtlas can be used as a quantitative resource to assess the state of terminology in English-language common names of birds. Future research using the database can shed light on historical approaches to nomenclature and how people engage with species through their names.

zoology↗

bioRxiv2024

Subtle, but perceptible, sexual dichromatism and disassortative mating based on plumage reflectance in Black Terns (Chlidonias niger)

In birds, sexual selection on plumage often leads to sexual dichromatism and male ornamentation. However, even in drab species with no obvious sexual dichromatism, both sexes may still use plumage for mate choice. A previous study found weak sexual size dimorphism in North American Black Terns (Chlidonias niger surinamensis), but no assortative mating based on morphology. However, the relevance of plumage variation to mate choice is yet untested. Here, using reflectance spectrometry and avian visual modeling revealed that Black Tern males and females exhibited a subtle but significant difference in brightness (males darker). Importantly, the achromatic contrast between the sexes should be perceptible during mate choice. Moreover, there was evidence of disassortative mating for plumage color, but not brightness: more black and saturated birds paired with more gray and unsaturated birds. There was no relationship between plumage color or brightness and body mass. This finding suggests that visual signals unrelated to body condition may be relevant to Black Tern mate choice. The pattern of disassortative mating was unexpected, and potential benefits of choosing a mate dissimilar from oneself are discussed. This study highlights the importance of considering the avian visual system when studying plumage variation elusive to human observers.

animal behavior and cognition↗

bioRxiv2023

Plural breeding among unrelated females and other insights on complex social structure in the cooperatively breeding Variegated Fairywren

Cooperatively breeding species vary widely in degree of social complexity, and disentangling relationships among group members can reveal the costs and benefits of cooperation. Here, we explore the social system of a relatively unstudied cooperatively breeding bird, the Variegated Fairywren (Malurus lamberti), and explore how social complexity and group dynamics may affect cooperation and conflict. We used a combination of field-based population monitoring and detailed social association observations to determine group membership annually across four breeding seasons (2014 - 2017), and used a ddRAD-seq genotyping method to determine genetic relationships within social groups. Social groups ranged in size from 2 - 8 individuals and nearly half of all social groups had multiple adult individuals of both sexes. Approximately two-thirds of those groups exhibited plural breeding, in which multiple females within the same social group nested individually on the same territory. Genetic relationships were diverse across social groups, and many consisted of a combination of relatives and non-relatives of each sex. Notably, although related females often were present within a social group, co-breeding females in the same social group were never closely related to each other. Given extensive variation in relatedness among group members, cooperation in the Variegated Fairywren is likely maintained by a combination of direct and indirect fitness benefits.

ecology↗

bioRxiv2022

Urbanization enhances multiple carotenoid-based signals despite poor body condition in male and female Northern Cardinals

If humans aim to sustainably coexist with wildlife, we must understand how our activity impacts the communication systems of urban animal populations. We know much about the effects of anthropogenic noise on bird song, but relatively little about how avian visual signals are affected by urbanization. One way such an effect may occur if urbanization alters the food available to species with color based on carotenoids, which they must obtain from their diet. Over three years, we compared a comprehensive suite of visual signals in male and female Northern Cardinals (Cardinalis cardinals) in a rural and an urban population. We predicted that urban birds would have enhanced carotenoid-based signals as they likely have access to more carotenoids from invasive plants, especially honeysuckle (Lonicera spp.), that thrive in cities. We used reflectance spectrometry, digital image analyses, and avian visual models to quantify hue, saturation, and brightness of chest (male), underwing (female), and bill (male and female) signals. Compared to rural males, urban males had redder chest feathers in one year and redder bills in every year. Urban females had more saturated underwing color than rural females in every year. These color differences were sufficient to be distinguished by the avian visual system. Urbanization did not affect female bill color. Interestingly, urban birds had significantly reduced mass-related body condition compared to rural birds. These results show that both male and female urban birds can display enhanced carotenoid-based signals despite being in relatively poor condition. The consequences of this color enhancement are unknown, but it could affect the information content of the signals and the dynamics of the social and mating systems. These results stand in stark contrast to the predominant trend in birds of decreased color in urban areas and highlight the complex and varied potential effects of urbanization on animal communication.

evolutionary biology↗

bioRxiv2020

Widlfire affects circulating hormone levels and the expression of male sexual plumage in a tropical songbird

Natural disturbances like drought and wildfires are expected to increase in prevalence, so understanding how organisms are affected is a key goal for conservationists and biologists alike. While many studies have illustrated long-term effects of perturbations on survival and reproduction, little is known of short-term effects to physiology and sexual signal expression. Ornamental traits have been proposed as reliable indicators of environmental health, yet studies are lacking in the context of natural disturbances. Here we present short-term responses of male Red-backed Fairywrens (Malurus melanocephalus) to wildfire near the onset of the typical breeding season. Males of this species are characterized by plastic expression of sexual plumage phenotypes in their first breeding season. Using two populations with Fairywren captures before and after separate wildfires we illustrate that wildfire suppressed molt into ornamented plumage, including in third year males that typically show little plasticity in ornamentation. Baseline plasma corticosterone was elevated in males sampled after fire, but condition (furcular fat stores) was unaffected. Although testosterone levels did not decrease following fire, we found a positive correlation between testosterone and plumage ornamentation. In addition, males molting in ornamental plumage had higher circulating levels of testosterone than males molting in unornamented plumage following fire. Collectively, these findings suggest that wildfires inhibit or greatly delay acquisition of ornamentation in young males without exerting obvious effects on condition, but rather through subtle effects on testosterone and corticosterone circulation. This natural experiment also reveals that expression of alternative male reproductive phenotypes in this species is sensitive to environmental conditions and more plastic than previously assumed.

ecology↗