Understanding how Temperature influences European Starling’s Reproductive Success

Many habitats face fluctuating temperatures year round. The animals that live there are typically able to adjust their behaviors to match these conditions. When temperatures become too extreme, however, it could potentially start having a negative effect on the animal’s reproductive success. In birds, for example, severe climate can affect their eggs and nestlings due to nestlings lacking the ability to thermoregulate. The parents then have to bear the responsibility of thermoregulation for their young, through a behavior called incubation or brooding. European starlings (Sturnus vulgaris) are a species of birds common across the United States where both parents incubate their eggs and or brood their nestlings. In order to understand how the weather could impact these birds, we used nest cameras to record the behaviors of starling parents from March to June of 2020. We then used NOAA historical weather data to assess whether temperatures during the daytime shaped the number of eggs these starlings laid (clutch size). We also checked to see if weather temperatures effected the incubation and brooding behaviors of parents when they were keeping their nestlings warm (thermoregulation). We hypothesized that extreme temperatures (too warm or too cold) would results in less eggs at the nest, and more parental care from the parents

The Effects of Provisional Rate on Offspring Growth in European Starlings

Offspring rarely have a linear growth rate and many external factors may be to blame for this. They may be most sensitive to their rearing conditions when they grow most rapidly. Parenting and provisional habits are similarly inconsistent and may depend on various factors including the energetic state of the parent or the food availability in the surrounding environment. Though not previously linked before, the connection between parental provisioning efforts and growth and success rate of the offspring may be immense. This study focused on European Starlings (Sturnus vulgaris). The hypothesis tested was that rapid offspring growth may be connected and coincide with an increase in parental provisioning habits. Nest boxes were studied over a course of several weeks, and videos were filmed every other day to allow analysis of provisioning rates. Nestlings were weighed every other day to determine growth rate of the offspring. We will be studying the habits and rates of the parental provisioning as well as other factors such as sex of the bird and weather. These are known factors that affect provisioning habits in birds. We will be presenting results on whether parental provisional care affects the growth rate of the offspring. This will allow scientists to better understand the nonlinear affect that provisioning habits have on the offspring at different stages of development

Costs and Benefits of Breeding Cooperatively in Fluctuating Environments in African Starlings

Global climate change is expected to increase the frequency of extreme and unpredictable weather in many parts of the world. As a result, a critical goal for biologists is to predict how organisms may come to cope with increased environmental variability. The key to making these predictions will be to understand how animals currently living in fluctuating environments are able to survive and reproduce under these conditions. Sociality (i.e. group living) and cooperative breeding (i.e. where more than two individuals care for young together) may both facilitate the colonization of highly fluctuating environments. However, the relative benefits of group living and engaging in alloparental care under variable conditions remain unclear. My dissertation examines the fitness consequences of living in one of the world’s most unpredictable habitats—the African savanna—in a population of free-living cooperatively breeding superb starlings (Lamprotornis superbus). In chapter 1, I examine whether adults benefit from living in large social groups of up to 50 individuals, which are among the largest known for any cooperatively breeding bird. In addition, I test whether group size serves to buffer against harsh environmental conditions. In chapter 2, I examine whether breeders gain reproductive benefits by having alloparents at their nest—I explore the type of reproductive benefits gained (i.e. improved reproductive success versus offspring care load-lightening), as well as whether these benefits occur in both harsh and benign conditions (i.e. temporal variability hypothesis), or are greatest under harsh conditions only (i.e. hard life hypothesis). In chapter 3, I explore whether offspring care load-lightening reduces the cost of reproduction incurred by breeders and alloparents by comparing four physiological mechanisms known to mediate reproductive costs. Lastly, in chapter 4 I test the long-standing assumption that cooperatively breeding species face reduced costs of reproduction by sharing offspring care relative to non-cooperatively breeding species. I compare the oxidative cost of reproduction in superb starlings to greater blue-eared glossy starlings (L. chalybaeus), a synoptic non-cooperatively breeding species. Taken together my dissertation findings demonstrate that group living and alloparental care do not solely buffer against harsh conditions in superb starlings, but instead provide individuals with the flexibility to modify their offspring care behavior according to environmental conditions, to the behavior of other group members, and to their physiological condition prior to breeding—this behavioral flexibility may in turn serve to mitigate fluctuations in the cost of living and breeding in variable environments

Multiple achromatic plumage signals of male quality in the snow bunting (Plectrophenax nivalis)

Although males can produce many ornaments, the evolution of multiple ornaments is not well understood. We investigated achromatic plumage traits in the context of multiple ornaments in Arctic-breeding snow buntings ( Plectrophenax nivalis ). We examined whether multiple ornaments: are providing multiple messages, are redundant, are unreliable signals or are aimed at different receivers. We measured plumage reflectance and pigmentation patterns that are differentially, but conspicuously advertised during male inter- and intra-sexual displays. Our results indicate that although several signals are redundant, different body regions appear aimed at different receivers. The wings of males--displayed during courtship--indicate male expected reproductive performance. Conversely, melanin reflectance displayed during intra-sexual threat displays signals territoriality. Different information provided by distinctive aspects of plumage may have differential importance in inter- versus intra-sexual communication. This study demonstrates that even relatively simple plumage traits can serve in complex communication

Effect of Diet on Window Collision Rate among Bird Species

Every year, over 500 million birds collide fatally with man-made structures, with window collisions playing a significant role in causing these deaths. Our research analyzes how a species’ diet can affect their rates of collision with windows. To explore this question, we analyzed the most common food sources of 87 species of birds from window collision data in metro Atlanta. Our results showed that 77% of species from window collisions (or 67 species) were primarily insectivorous. This reliance on insects as a food source could lead to a lifestyle that tends to bring these bird species in closer proximity to windows more frequently. Consequently, these birds may become more likely to collide with a window while foraging or hunting for food. From an environmental perspective, this research draws close attention to the need to consider diet when analyzing bird-window collisions and preventative measures. In addition, it provides an additional benchmark for assessing collisions, the bird’s diet, that can help target species that are most at risk and would require the most assistance

Effects of sibling competition on growth, oxidative stress, and humoral immunity: a two-year brood-size manipulation

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. . On the basis of annual differences in chicks' morphological traits and body masses close to fledging, we established that 2007 was a relative low-quality year and 2008 was a relatively high-quality year. Total antioxidant capacity (TAC) was significantly lower in experimentally enlarged broods, but only in the low-quality year (2007). Total oxidant status (TOS) was independent of brood size in both years but was 45% higher in the low-quality year. Consequently, plasma oxidative status (the ratio between TOS and TAC) was higher in 2007. In contrast, plasma IgY levels were higher in the experimentally enlarged broods and in the high-quality year (2008). Thus, immune function and oxidative stress showed inverse relationships with developmental conditions and annual variation in year quality. Finally, TOS and TAC were positively correlated, but only in the low-quality year (2007), and there was no relationship observed between IgY and markers of oxidative stress. Our results demonstrate the importance of taking into account year effects or ecological context when assessing environmental effects on physiological mechanisms underlying the life-history traits of chicks, such as oxidative stress. The University of Chicago Pres

Multiple achromatic plumage ornaments signal to multiple receivers

We investigated whether achromatic plumage traits can act as multiple ornaments in an Arctic-breeding passerine, the snow bunting (Plectrophenax nivalis). Specifically, we examine whether multiple ornaments are providing multiple differing messages, are redundant, are unreliable signals of male quality, or are aimed at different receivers. We measured plumage reflectance and pigmentation patterns made conspicuous during male inter-and intrasexual displays that advertise different plumage regions. Our results indicate that although several aspects of male plumage may have redundant messages, different body regions appear aimed at different receivers. The wings of males-displayed primarily toward females during courtship-appear to indicate a pair\u27s future reproductive performance. Conversely, melanin-based plumage reflectance displayed during intrasexual threat displays provides information on territory features and a male\u27s capacity to defend it (i.e., territory size, territory quality, testosterone levels). Taken together, we suggest that snow buntings have multiple ornaments that provide information of differential importance in inter-versus intrasexual communication. This study demonstrates that achromatic plumage traits can serve in complex communication. © 2012 The Author

The oxidative costs of territory quality and offspring provisioning

The costs of reproduction are an important constraint that shapes the evolution of life histories, yet our understanding of the proximate mechanism(s) leading to such life-history trade-offs is not well understood. Oxidative stress is a strong candidate measure thought to mediate the costs of reproduction, yet empirical evidence supporting that increased reproductive investment leads to oxidative stress is equivocal. We investigated whether territory quality and offspring provisioning increase oxidative stress in male snow buntings (Plectrophenax nivalis) using a repeated sampling design. We show that arrival oxidative stress is not a constraint on territory quality or the number of offspring fledged. Nevertheless, owners of higher-quality territories experienced an oxidative cost, with this cost increasing more rapidly in younger males. Males that provisioned offspring at a high rate also experienced increased oxidative stress. Together, these findings support the potential role of oxidative stress in mediating life-history trade-offs. Future work should consider that reproductive workload is not limited to offspring care, and other activities - including territory defence - may contribute significantly to the costs of reproduction. © 2013 European Society For Evolutionary Biology

Sex ratios and the city: Secondary offspring sex ratios, parental corticosterone, and parental body condition in an urban-adapted bird

The Trivers–Willard hypothesis states that mothers should adjust their offspring sex ratio according to their own condition and the environment they face during breeding. Past tests of this hypothesis have focused on how natural variation in weather, food availability, or predation pressure shapes sex allocation trade-offs. However, anthropogenic activities, such as urbanization, can alter all of the above characteristics presenting animals with novel challenges in optimizing their brood sex ratio. Previous research has examined how urban living influences individual body condition in several bird taxa, but few have explored subsequent impacts on secondary offspring sex ratio. One likely mediator of the link between environmental conditions, parental condition, and sex ratios is corticosterone (CORT), the primary glucocorticoid in birds. Research on CORT’s influence on sex ratios has focused solely on maternal CORT. However, for species with biparental care, paternal CORT or the similarity of maternal and paternal phenotypes may also help ensure that offspring demand matches parental care quality. To test these hypotheses, we explore offspring secondary sex ratios in European starlings (Sturnus vulgaris). We did not find an effect of site or parental body condition on the production of the more costly sex (males). Instead, we found preliminary evidence suggesting that the similarity of maternal and paternal CORT levels within a breeding pair may increase the likelihood of successfully fledging sons. Maternal and paternal CORT were not significant predictors of secondary sex ratio, suggesting that parental similarity, rather than parental CORT alone, could play a role in shaping secondary offspring sex ratios, but additional work is needed to support this pattern. Starlings are considered an urban-adapted species, making them a compelling model for future studies of the relationship between urbanization, parental body condition, and sex ratios

Diversity in warning coloration: selective paradox or the norm?

Aposematic theory has historically predicted that predators should select for warning signals to converge on a single form, as a result of frequency-dependent learning. However, widespread variation in warning signals is observed across closely related species, populations and, most problematically for evolutionary biologists, among individuals in the same population. Recent research has yielded an increased awareness of this diversity, challenging the paradigm of signal monomorphy in aposematic animals. Here we provide a comprehensive synthesis of these disparate lines of investigation, identifying within them three broad classes of explanation for variation in aposematic warning signals: genetic mechanisms, differences among predators and predator behaviour, and alternative selection pressures upon the signal. The mechanisms producing warning coloration are also important. Detailed studies of the genetic basis of warning signals in some species, most notably Heliconius butterflies, are beginning to shed light on the genetic architecture facilitating or limiting key processes such as the evolution and maintenance of polymorphisms, hybridisation, and speciation. Work on predator behaviour is changing our perception of the predator community as a single homogenous selective agent, emphasising the dynamic nature of predator-prey interactions. Predator variability in a range of factors (e.g. perceptual abilities, tolerance to chemical defences, and individual motivation), suggests that the role of predators is more complicated than previously appreciated. With complex selection regimes at work, polytypisms and polymorphisms may even occur in Mullerian mimicry systems. Meanwhile, phenotypes are often multifunctional, and thus subject to additional biotic and abiotic selection pressures. Some of these selective pressures, primarily sexual selection and thermoregulation, have received considerable attention, while others, such as disease risk and parental effects, offer promising avenues to explore. As well as reviewing the existing evidence from both empirical studies and theoretical modelling, we highlight hypotheses that could benefit from further investigation in aposematic species. Finally by collating known instances of variation in warning signals, we provide a valuable resource for understanding the taxonomic spread of diversity in aposematic signalling and with which to direct future research. A greater appreciation of the extent of variation in aposematic species, and of the selective pressures and constraints which contribute to this once-paradoxical phenomenon, yields a new perspective for the field of aposematic signalling.Peer reviewe