
Michael S. WebsterCornell University | CU · Department of Neurobiology and Behavior
Michael S. Webster
PhD
About
211
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Introduction
Skills and Expertise
Additional affiliations
September 2009 - present
Publications
Publications (211)
Vegetation structural complexity surrounding nests can either provide concealment for intruders and mates or make it more difficult for hosts to recognize parasitic eggs. We investigated whether shading and vegetation aggregation increase extrapair paternity (the presence of broods with half‐siblings) and intraspecific brood parasitism (IBP, the oc...
Island organisms often evolve phenotypes divergent from their mainland counterparts, providing a useful system for studying adaptation under differential selection. In the white-winged fairywren (Malurus leucopterus), subspecies on two islands have a black nuptial plumage whereas the subspecies on the Australian mainland has a blue nuptial plumage....
When monitoring the nesting biology of wild birds, nests are often found after the eggs have been laid and incubation has commenced. Candling – the use of a bright light to illuminate egg contents – is a useful method for estimating embryo development and incubation stage. This information is used to estimate when incubation started and predict whe...
We observed a congregation of Rufous Whistlers Pachycephala rufiventris perform courtship displays toward each other on multiple occasions, a previously undocumented behaviour. We posit that the location of the courtship behaviour represented a communal display area and the behaviour arose either because of individuals congregating at an establishe...
When monitoring the nesting biology of wild birds, nests are often found after the eggs have been laid and incubation has commenced. Candling—the use of a bright light to illuminate egg contents—is a useful method for estimating embryo development and incubation stage. This information is used to estimate when incubation started and predict when eg...
Sex allocation theory predicts that females should bias their offspring sex ratios when the fitness benefits of producing sons or daughters differ depending on rearing environment. The Trivers-Willard hypothesis proposes that whether females produce more sons or daughters depends on food availability via both intrinsic maternal condition and differ...
Vocal production learning (the capacity to learn to produce vocalizations) is a multidimensional trait that involves different learning mechanisms during different temporal and socioecological contexts. Key outstanding questions are whether vocal production learning begins during the embryonic stage and whether mothers play an active role in this t...
Island organisms often evolve phenotypes divergent from their mainland counterparts, providing a useful system for studying adaption under differential selection. Some island birds have melanic plumage differing from the color of mainland conspecifics, a trait proposed as an insular adaptation. In the white-winged fairywren ( Malurus leucopterus ),...
James River
The American Ornithological Society (AOS) offers two service awards, the Peter R. Stettenheim Service Award and the Marion Jenkinson Service Award, to recognize AOS members who have provided continued, exceptional service to ornithology and to the Society. This year, James Rivers is awarded the Marion Jenkinson Service Award.
James Rive...
During the breeding season, male Red-backed Fairywrens (Malurus melanocephalus) can exhibit ornamented (red-black) or unornamented (brown, resembling females and juveniles) plumage. These distinct plumage types represent alternative reproductive tactics and are associated with behavioural differences during the breeding season. However, we lack an...
Carotenoid pigments underlie most of the red, orange, and yellow visual signals used in mate choice in vertebrates. However, many of the underlying processes surrounding the production of carotenoid-based traits remain unclear due to the complex nature of carotenoid uptake, metabolism, and deposition across tissues. Here, we leverage the ability to...
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 an...
Understanding the demographic drivers of range contractions is important for predicting species' responses to climate change; however, few studies have examined the effects of climate change on survival and recruitment across species' ranges. We show that climate change can drive trailing edge range contractions through the effects on apparent surv...
Seasonally breeding animals often exhibit different social structures during non-breeding and breeding periods that coincide with seasonal environmental variation and resource abundance. However, we know little about the environmental factors associated with when seasonal shifts in social structure occur. This lack of knowledge contrasts with our w...
Despite much research on mimicry, little is known about the ecology of dynamic mimetic signals involving mimicry of multiple species. Some of the most conspicuous examples of phenotypically plastic mimicry are produced by oscine passerines, where vocal production learning enables some species to mimic multiple models and flexibly adjust what they m...
Ornamentation, such as the showy plumage of birds, is widespread among female vertebrates, yet the evolutionary pressures shaping female ornamentation remain uncertain. In part this is due to a poor understanding of the mechanistic route to ornamentation in females. To address this issue, we evaluated the evolutionary history of ornament expression...
The interface between field biology and technology is energizing the collection of vast quantities of environmental data. Passive acoustic monitoring, the use of unattended recording devices to capture environmental sound, is an example where technological advances have facilitated an influx of data that routinely exceeds the capacity for analysis....
Sperm competition is thought to impose strong selection on males to produce competitive ejaculates to outcompete rival males under competitive mating conditions. Our understanding of how different sperm traits influence fertilization success, however, remains limited, especially in wild populations. Recent literature highlights the importance of in...
Historically, bird song complexity was thought to evolve primarily through sexual selection on males; yet, in many species, both sexes sing and selection pressure on both sexes may be broader. Previous research suggests competition for mates and resources during short, synchronous breeding seasons leads to more elaborate male songs at high, tempera...
Both abiotic environmental conditions and variation in social environment are known to impact the acquisition of sexual signals. However, the influences of abiotic environmental and social factors are rarely compared to each other. Here we test the relative importance of these factors in determining whether and when male red-backed fairy-wrens, Mal...
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 sexu...
Temporal coordination of duets consists of nonrandom overlap, alternation or association between rhythms of acoustic elements. Since duet coordination presumably requires high attentiveness between signallers, the coalition quality hypothesis suggests it may indicate the ability or motivation of partners to engage cooperatively in aggressive intera...
Assessing diversity of discretely varying behaviour is a classical ethological problem. In particular, the challenge of calculating an individuals’ or species’ vocal repertoire size is often an important step in ecological and behavioural studies, but a reproducible and broadly applicable method for accomplishing this task is not currently availabl...
Animals produce a wide array of sounds with highly variable acoustic structures. It is possible to understand the causes and consequences of this variation across taxa with phylogenetic comparative analyses. Acoustic and evolutionary analyses are rapidly increasing in sophistication such that choosing appropriate acoustic and evolutionary approache...
The existence of distinct traits in island versus mainland populations offers opportunities to gain insights into how eco‐evolutionary processes operate under natural conditions. We used two island colonization events in the white‐winged fairywren (Malurus leucopterus) to investigate the genomic and demographic origin of melanic plumage. This avian...
In socially monogamous species, male reproductive success consists of ‘within‐pair’ offspring produced with their socially‐paired mate(s), and ‘extra‐pair’ offspring produced with additional females throughout the population. Both reproductive pathways offer distinct opportunities for selection in wild populations, as each is composed of separate c...
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 sexu...
Carotenoid pigments produce most red, orange and yellow colours in vertebrates. This coloration can serve as an honest signal of quality that mediates social and mating interactions, but our understanding of the underlying mechanisms that control carotenoid signal production, including how different physiological pathways interact to shape and main...
In pair-bonding species, male reproductive success consists of "within-pair" offspring produced with their socially-paired mate(s), and "extra-pair" offspring produced with additional females throughout the population. Both reproductive pathways offer distinct opportunities for sexual selection to operate in wild populations, as each are composed o...
Most of the diversity in the mating systems of birds and other animals comes at higher taxonomic levels, such as across orders. Although divergent selective pressures should lead to animal mating systems that diverge sharply from those of close relatives, opportunities to examine the importance of such processes are scarce. We addressed this issue...
Duets in breeding pairs may reflect a situation of conflict, whereby an individual an‐ swers its partner's song as a form of unilateral acoustic mate guarding or, alternatively, it may reflect cooperation, when individuals share in territory defense or safeguard the partnership. The degree of coordination between the sexes when responding to solo v...
Abstract Behavioral barriers to gene flow often evolve faster than intrinsic incompatibilities and can eliminate the opportunity for hybridization between interfertile species. While acoustic signal divergence is a common driver of premating isolation in birds and insects, its contribution to speciation in mammals is less studied. Here we character...
Duetting has been intensively studied, but we still have little consensus about its fitness consequences. Some studies suggest that duetting functions in acoustic mate guarding to prevent cuckoldry (acoustic paternity guarding hypothesis), whereas other studies argue that duetting is a cooperative behavior to defend common resources (territory defe...
The forces shaping female plumage color have long been debated but remain unresolved. Females may benefit from conspicuous colors but are also expected to suffer costs. Predation is one potential cost, but few studies have explicitly investigated the relationship between predation risk and coloration. The fairy-wrens show pronounced variation in fe...
Behavioral changes, such as those involved in mating, foraging, and migration, can generate reproductive barriers between populations. Birds, in particular, are known for their great diversity in these behaviors, and so behavioral isolation is often proposed to be the major driver of speciation. Here, we review empirical evidence to evaluate the im...
Animals in social aggregations use signals of quality or motivation to attract mates and intimidate rivals. Theory indicates that honesty can be maintained in these signals if the costs of signalling affect low-quality individuals more than they affect high-quality individuals. Considerable research has focused on identifying the nature of those co...
Thermal variation poses a problem for nesting birds and can result in reduced offspring growth rates and survival. To increase the thermal stability of the nest, females can adjust nest characteristics and nest attendance in response to changes in environmental conditions. However, it is unclear how and to what extent females modify parental behavi...
Behavioral changes, such as those involved in mating, foraging, and migration , can generate reproductive barriers between populations. Birds, in particular, are known for their great diversity in these behaviors, and so be-havioral isolation is often proposed to be the major driver of speciation. Here, we review empirical evidence to evaluate the...
Information on genetic relationships among individuals is essential to many studies of the behavior and ecology of wild organisms. Parentage and relatedness assays based on large numbers of SNP loci hold substantial advantages over the microsatellite markers traditionally used for these purposes. We present a double-digest restriction site-associat...
Information on genetic relationships among individuals is essential to many studies of the behavior and ecology of wild organisms. Parentage and relatedness assays based on large numbers of SNP loci hold substantial advantages over the microsatellite markers traditionally used for these purposes. We present a double-digest restriction site-associat...
Duetting is a collective behavior and might have multiple functions, including joint territory defense and mate guarding. An important step toward understanding the adaptive function of bird song is to determine if and how singing behavior varies seasonally. However, seasonal patterns for duetting species are different from the pattern described fo...
When males compete for mates, they often defend paternity through mate guarding. In addition to physical guarding, in vocal species, especially duetting birds, individuals may duet with their mates in order to guard them. The acoustic mate-guarding hypothesis posits that duetting deters rivals. We experimentally tested the effectiveness of physical...
Geographic variation in song is widespread among birds, particularly in species that learn vocalizations. The relationship between geographic distance and song variation is likely related to the degree of isolation between populations. To assess this effect of geographic isolation on song divergence, we examined patterns of geographic song variatio...
Extra-pair paternity (EPP), where offspring are sired by a male other than the social male, varies enormously both within and among species. Trying to explain this variation has proved difficult because the majority of the interspecific variation is phylogenetically-based. Ideally, variation in EPP should be investigated in closely related species,...
Our understanding of trait evolution is built upon studies that examine the correlation between traits and fitness, most of which implicitly assume all individuals experience similar selective environments. However, accounting for differences in selective pressures, such as variation in the social environment, can advance our understanding of how s...
In cooperative species, parental investment may be shared with auxiliaries. Kin selection and other types of benefits have been proposed to explain the evolution of helping behavior. Auxiliaries are expected to be more helpful when closely related to the breeders. In this context, breeders may adjust parental investment in at least three ways: (a)...
Single nucleotide polymorphisms (SNPs) are preferred over microsatellite markers in many evolutionary studies, but have only recently been applied to studies of parentage. Evaluations of SNPs and microsatellites for assigning parentage have mostly focused on special cases that require a relatively large number of heterozygous loci, such as species...
Many studies of sexual selection assume that individuals have equal mating opportunities and that differences in mating success result from variation in sexual traits. However, the inability of sexual traits to explain variation in male mating success suggests that other factors moderate the strength of sexual selection. Extrapair paternity is comm...
When mates are limited, individuals should allocate resources tomating tactics that maximize fitness. In species with extra-pair paternity (EPP), males can invest in mate guarding, or, alternatively, in seeking EPP. Males should optimize fitness by adjusting investment according to their attractiveness to females, such that attractive males seek EP...
Data for Model 1: Testing the effects of ecological and social factors on the probability of siring extra-pair young
Data for Model 2: Testing the effect of food availability on breeding distance
R code
In males it is frequently testosterone (T) that activates the expression
of sexually selected morphological and behavioral displays, but the
role of T in regulating similar traits in females is less clear. Here, we
combine correlational data with results from T and gonadotropinreleasing
hormone (GnRH) manipulations in both sexes to assess the
role...
Single nucleotide polymorphisms (SNPs) are preferred over microsatellite markers in many evolutionary studies, but have only recently been applied to studies of parentage. Evaluations of SNPs and microsatellites for assigning parentage have mostly focused on special cases that require a relatively large number of heterozygous loci, such as species...
Although long-distance migratory songbirds are widely believed to be at risk from warming temperature trends, species capable of attempting more than one brood in a breeding season could benefit from extended breeding seasons in warmer springs. To evaluate local and global factors affecting population dynamics of the black-throated blue warbler (Se...
Many vocal animals recognize kin using vocal cues, in territorial contexts and in rearing young, but little is known about the developmental and evolutionary mechanisms that produce vocal kin recognition systems. In the cooperatively breeding red-backed fairy-wren (Malurus melanocephalus), females give specific “in-nest calls” while incubating thei...
Cooperative breeding is a phenomenon whereby breeding and nonbreeding individuals collectively provision young. Nonbreeding group members ("helpers") may gain indirect and/or direct fitness benefits by breeding in a group, but there has been conflicting evidence regarding the benefits to breeders. In fact, the presence of helpers may sometimes be d...
Prenatal imitative learning is an emerging research area in both human and non-human animals. Previous studies in Superb Fairywrens (Malurus cyaneus) showed that mothers are vocal tutors to their embryos and that better imitation of maternal calls yields more parental provisions after hatching. To begin to test if such adaptive behavior is widespre...
When individuals mate outside the pair bond, males should employ behaviours such as aggression or vocal displays (e.g. duetting) that help assure paternity of the offspring they care for. We tested whether male paternity was associated with aggression or duetting in the red-backed fairy-wren, a species exhibiting high rates of extra-pair paternity....
Nutritional stress can have lasting impacts on the development of traits involved in vocal production. Cross-fostering experiments are often used to examine the propensity for vocal learning in a variety of taxa, but few studies assess the influence of malnourishment that can occur as a byproduct of this technique. In this study, we reciprocally cr...
Individuals within social groups commonly combine vocal signals, forming duets. Although these displays have been described
across taxa, their function is not fully understood. In birds, territory defense is a well-supported function of duetting,
but additional functions are likely. Extrapair paternity (EPP) is common in birds, and males at risk of...
Sexual selection on multiple signals may lead to differential rates of signal introgression across hybrid zones if some signals contribute to reproductive isolation but others facilitate gene flow. Competition among males is one powerful form of sexual selection, but male behavioral responses to multiple traits have not been considered in a system...
Darwin's finches are, to say the least, an iconic species for the study of evolution. Starting with Darwin's own writings through to the pioneering field studies of David Lack, this clade of birds came to symbolize adaptation and the creative force of natural selection. But it is really through the work and writings of Peter and Rosemary Grant that...
Variation in song structure and song production of birds are thought to relate to variation of both androgen levels and neural nuclei in the song system, as typically these nuclei are larger in males than in females, vary in size among males and are sensitive to steroid hormones. We investigated the relationships among song and note structure, sing...
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 campest...
Environmental factors can shape reproductive investment strategies and influence the variance in male mating success. Environmental effects on extrapair paternity have traditionally been ascribed to aspects of the social environment, such as breeding density and synchrony. However, social factors are often confounded with habitat quality and are ch...
Morphological and behavioural traits often covary with each other, and the links between them may arise from shared physiological mechanisms. In particular, androgens such as testosterone have emerged as prime candidates for linking behaviour and morphology due to the environmental sensitivity and pleiotropic effects of these hormones. In this stud...
WPP Model Table 1
EPP Model Table 1
Double brooding Model Table 1
Table 2
Poisson Model