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Full thesis document accompanied by all data files and R scripts to reproduce analyses in both data chapters (2 & 3). / Animals should favour breeding locations that maximize their lifetime reproductive output. Parents ought to rear young in sites that positively affect offspring but sometimes these same sites inflict costs on parents. How parents balance their own needs against those of their offspring when selecting a site for reproduction remains unclear, particularly in animals that provide extended parental care at one location. Further, few studies have linked variation in life history traits to reproductive site choices within a single species. In this thesis, I addressed both knowledge gaps by studying the plainfin midshipman (Porichthys notatus), a marine toadfish where fathers provide sole parental care to broods of young in intertidal and shallow subtidal nests for up to two months. In Chapter 2, I measured the costs incurred by caring males and the benefits conferred to offspring in nest sites along a tidal gradient. Males suffered similar rates of body condition deterioration in all nests across the intertidal gradient. Young developed more quickly in intertidal nests compared to subtidal nests, but broods in the highest intertidal nests suffered the highest mortality rates, despite receiving more parental care from the males at these nest sites. We found the most competitive males in lower intertidal nests, a trend that agrees with life history theory—in species with relatively slow offspring development, parents should accrue greater reproductive benefits from nest sites where offspring benefits are highest. In Chapter 3, I describe a laboratory experiment designed to examine how warm water and air exposure (two abiotic conditions that vary dramatically within the intertidal) affect development and survival of plainfin midshipman young, and how these effects vary with maternal traits. Exposure to warm water enhanced embryonic and larval development rates; this effect was attenuated by air exposure. Juveniles raised in warm water also exhibited superior swimming performance, while air-exposed young suffered higher mortality rates. Although larger juveniles emerged from larger eggs, development rates were similar across egg sizes. Offspring survival increased with maternal body condition in cold water but decreased with maternal body condition in warm water. Juvenile body sizes increased with maternal condition in cold water without emersion, and in warm water with emersion—the two ecologically relevant rearing environments. Thus, low condition mothers might accrue greater benefits by depositing their eggs in nests at higher tidal elevations—where development is more rapid—further supporting the idea that among-individual variation in the expression of life history traits might influence nest site preferences in these fish. In sum, my research (Chapters 2 & 3) elucidates the link between life history traits and the spatial component of animal reproductive strategies. / Thesis / Master of Science (MSc)

Parents can have large effects on their offspring by influencing the early developmental environment. In birds, a major way that parents can influence the early developmental environment is through egg incubation. Not only is incubation necessary for hatching success, but small changes of <1C in average incubation temperature have large effects on post-hatch offspring morphology and physiology. However, incubation is energetically costly and time-consuming for parents, and thus parents must allocate resources between incubation and self-maintenance. This can lead to differences in parental incubation behavior and egg temperatures among and within populations. Understanding which factors influence incubation, and the subsequent effects for offspring, is crucial for understanding parental effects, non-genetic drivers of phenotypic variation, and how environmental changes affect avian populations. I used wood ducks (Aix sponsa) as a study species to investigate how factors (disturbance, clutch size, ambient temperature) that influence parental demands may affect parental incubation behavior, physiology, and egg temperatures, and subsequently how egg temperatures affect offspring behavior and physiology. In a field experiment, I found that nest disturbance (i.e., capture) reduced both parent prolactin concentrations and the amount of time that parents spent incubating (Chapter 1). Further, ambient temperature was positively and clutch size negatively related to egg temperatures. Notably, in large clutches, differences in average incubation temperature among eggs within nests were large enough (i.e., >1C) to lead to different offspring phenotypes within broods (Chapter 2). Then, in a series of experiments in which I controlled incubation temperature, I provided evidence that lower average incubation temperatures lead to a reduced ability of ducklings to exit the nest cavity (Chapter 3), a more proactive behavioral phenotype (Chapter 4), a smaller body size, and a reduced efficiency in food consumption (Chapter 5), compared to those incubated at higher temperatures. Together, my dissertation illustrates how disturbances, clutch size, and ambient temperature can influence an important aspect of avian parental care, which has wide-ranging effects on offspring traits and fitness. This has broad implications for understanding the evolution of clutch size, development of behavior, and the effects of anthropogenic changes on wildlife. / Doctor of Philosophy / Animal parents can have large effects on the development of their offspring. In birds, an important way that parents affect their offspring is through incubation, where parents physically warm their eggs to stimulate embryo development. Eggs must be incubated in order to hatch, but recent research has shown that small changes (<1C/2F) in average incubation temperature have major consequences for the quality (e.g., size, ability to thermoregulate) of offspring after they hatch. However, parents must balance how they spend their time and energy between incubation and other important activities (e.g., eating, avoiding predators), and thus incubation behavior and temperature can vary among birds. Understanding which factors affect incubation, and the consequences of altered incubation temperatures for the offspring, will help us to better understand how animals care for their offspring and how environmental changes may influence offspring development. I investigated how human disturbance, environmental temperature, and the number of eggs in the nest influenced parental incubation behavior and egg temperatures, and subsequently how egg temperatures affected offspring behaviors. By studying wood ducks (Aix sponsa) in the wild, I found that parents spent less time incubating after a human disturbance (i.e., capture) than before (Chapter 1), egg temperatures increased as environmental temperatures increased, and egg temperatures decreased as the number of eggs in the nest increased (Chapter 2). Further, in nests with many eggs (>12), some eggs experienced much lower average incubation temperatures (>1C/2F difference) than others in the same nest (Chapter 2). Then, by studying wood duck ducklings in an aviary, I found that ducklings incubated at lower temperatures were less successful at exiting a nest (Chapter 3), exhibited bolder and more exploratory behaviors (Chapter 4), were smaller, and consumed less food (Chapter 5), than those incubated at a higher temperature. Together, my dissertation shows that the number of eggs in a nest, environmental temperatures, and human disturbances can influence parental behaviors, which then affect offspring. This has broad implications for understanding why birds lay the number of eggs that they do, how animal behaviors develop, and how environmental changes (including those caused by humans) can affect wildlife.

Mutualism is an understudied interaction in ecosystems throughout the world. Within the eastern United States, one fish-fish mutualism is the nest association between Nocomis and other cyprinids. I assessed the role of host parental care while testing for the selfish-herd effect. Additionally, I examined multiple nest associates in order to elucidate potential cheaters. I utilized gonadosomatic index (GSI) to compare reproductive condition among the bluehead chub Nocomis leptocephalus and its putative nest associates in Catawba Creek, Virginia. GSI of potentially obligate associates tracked host GSI more closely than weak associates, while weak associates spawned prior to Nocomis spawning. Given their GSI patterns and behavior, central stonerollers Campostoma anomalum may be cheaters in the interaction. I used multiple experiments to test for the selfish-herd effect, the role of parental care, and how relative risk influences reproductive decisions of associates. Most eggs were located in the bottom upstream quarter of nests, and a molecular analysis revealed that stonerollers and chubs constituted the majority of identified individuals. A comparison of host-associate ratios from four nest sections failed to identify the selfish herd effect. Another experiment found that host egg covering significantly reduced egg predation. Lastly, I assessed relative egg predation risk at four potential spawning locations; predation levels did not differ significantly at any location. While GSI patterns suggest that stonerollers may be cheaters, genetic evidence indicates that stonerollers spawn on Nocomis nests. Because GSI does not completely assess reproduction, secondary stoneroller reproduction on Nocomis nests may have been overlooked. / Master of Science

The behavior of humans and animals is an important component of conservation. The way people behave can cause environmental harm, but it also can be a solution to conservation challenges. Similarly, wildlife can respond to changing environments in ways that are detrimental to their survival, but they can also in some cases adapt or even thrive in human-impacted environments. In this dissertation, I discuss the ways in which human and hellbender behaviors relate to conservation. First, using survey and interview data, I explore the reasons why private landowners allow access to their property for research. I find that landowners are more likely to allow research on their property if they have previously allowed research, if they are interested in learning about the research taking place, if they have larger properties, and if they had positive attitudes towards conservation. Conversely, they are less likely to allow access to their property if they are concerned that doing so might restrict free use of their property. Other possible predictors that I investigate, such as landowner demographics, landowner trust in science, and landowner attitudes towards hellbenders are not significant predictors of allowing research. I next explore the effects of engaging landowners in research either via citizen science or "traditional" private lands research where scientists work on the landowner's property, but the landowner is not involved in data collection. I assess the effects of these types of engagement on landowner conservation knowledge, attitudes, awareness, and behavioral intentions and compare the effects across these two treatment groups and a control. I find similar changes in both the traditional and citizen science treatment groups, with involvement in the research leading to greater conservation knowledge, increased awareness of conservation concerns, more positive attitudes towards conservation, and/or more conservation behavioral intentions. However, I observe limited behavior change in any treatment group, and I identify a lack of efficacy and a hesitancy to accept responsibility for water quality degradation as possible barriers to behavior change. My investigations of animal behavior utilize custom-built underwater infrared camera technology to study hellbender reproductive behavior. I first add to current understanding of hellbender breeding behavior by describing the basic hellbender mating sequence, identifying the presence of potential alternative mating tactics, and describing two novel behaviors, including possible signal production via wave-based communication and a unique egg laying behavior by female hellbenders. I then measure the extent to which hellbender males (which provide the parental care) may help protect their offspring from low oxygen and high siltation, and I assess the possibility of trade-offs between parental care behaviors that benefit the eggs and self-maintenance behaviors that benefit the parent. I find that guarding male hellbenders increase both their parental care behaviors and their self-maintenance behaviors in response to low dissolved oxygen, but that they also show evidence of a trade-off between the two, with males ceasing parental care in favor of self-maintenance at sufficiently low levels of dissolved oxygen. Males show no parental response to high levels of silt. My findings add to our understanding of human and animal behavior and highlight the importance of behavioral flexibility to conservation. I find that hellbenders can to some extent modify their behaviors to compensate for the impacts of poor stream management on their own and their offspring's health, and I find that engaging landowners in research can encourage changes in awareness, attitudes, and behavioral intentions regarding conservation. / Doctor of Philosophy / The behavior of humans and animals is an important component of conservation. The way people behave can cause environmental harm, but it also can be a solution to conservation challenges. Similarly, wildlife can respond to changing environments in ways that are detrimental to their survival, but they can also in some cases change to survive or even thrive in human-impacted environments. In this dissertation, I discuss the ways in which human and hellbender behaviors relate to conservation. First, using survey and interview data, I explore the reasons why private landowners allow access to their property for research. I find that landowners are more likely to allow research on their property if they have previously allowed research, if they are interested in learning about the research taking place, if they have larger properties, and if they had positive attitudes towards conservation. Conversely, they are less likely to allow access to their property if they are concerned that doing so might restrict free use of their property. Other possible predictors that I investigate, such as landowner age and sex, landowner trust in science, and landowner attitudes towards hellbenders are not significant predictors of allowing research. I next explore the effects of engaging landowners in research either via citizen science, where landowners help collect data, or "traditional" private lands research where scientists work on the landowner's property, but the landowner is not involved in data collection. I assess the effects of these types of engagement on landowner conservation knowledge, attitudes, awareness, and planned actions and compare the effects across these two treatment groups and a control. I find similar changes in both the traditional and citizen science treatment groups, with involvement in the research leading to greater conservation knowledge, increased awareness of conservation concerns, more positive attitudes towards conservation, and/or more conservation planned actions. However, I observe limited behavior change in any treatment group, and I identify a lack of perceived ability to make a difference among landowners and a hesitancy to accept responsibility for water quality decline as possible barriers to behavior change. My investigations of animal behavior use custom-built underwater night-vision cameras to study hellbender baby-making. I first add to current understanding of hellbender breeding behavior by describing basic hellbender mating activities, identifying the possibility that some males sneak into other male's nests to mate, and describing two new behaviors, including possible signal production via sound or vibration and a unique egg laying behavior by female hellbenders. I then measure how much hellbender males (which provide the parental care) may help protect their eggs from low oxygen and high dissolved dirt, and I assess the possibility of trade-offs between parental care behaviors that benefit the eggs and self-maintenance behaviors that benefit the parent. I find that guarding male hellbenders increase both their parental care behaviors and their self-maintenance behaviors in response to low dissolved oxygen, but that they also show evidence of a trade-off between the two, with males stopping parental care in favor of self-maintenance at low levels of dissolved oxygen. Males show no parental response to high levels of dissolved dirt. My findings add to our understanding of human and animal behavior and highlight the importance of behavioral flexibility to conservation. I find that hellbenders can to some extent change their behaviors to compensate for the impacts of poor stream management on their own and their children's health, and I find that engaging landowners in research can encourage changes in awareness, attitudes, and planned behaviors regarding conservation.

<p>Natural and sexual selection and sexual conflict are forces shaping the evolution of reproductive behaviour, while constrained by factors like environment, physiology and life-history trade-offs. Parental care is costly both in terms of time and energy. In fish, filial cannibalism is a strategy for caring males to compensate for some of the energy loss. Human impact like eutrophication also alters the basics for animals living in that environment. It is fundamental to any species to adjust its behaviour to a changing environment. Studying sand goby males, I found trade-offs both regarding parental care allocations, like ventilation vs. predator defence, and investment in present vs. future reproductive success. Paternal sand gobies exposed to water with low oxygen levels increased their fanning effort but did not compensate by eating more eggs, even though an increased current parental effort should affect future reproductive success negatively. Investigating if patterns of filial cannibalism change with time of season, I found no correlation. Theory predicts that it should pay more to eat eggs early, when future mating potential is higher than late in the season. However, as early hatching fry are likely to gain higher fitness through larger size the next breeding season, this may provide an opposing selection pressure. In species with male care the only way a female can affect the level of post-spawning care is by choosing a good mate. A female preference to spawn in nests that already contain eggs of other females has been interpreted as a means to avoid filial cannibalism through a dilution effect or to decrease the costs of search time. Yet, in my study females did not avoid filial cannibalism by preferring large clutches to small ones. Oxygenation of the eggs might be a key factor, since both large and small females preferred spawning in nests with small clutches. Thus, as in most animals, trade-offs clearly govern the reproductive behaviour of sand gobies.</p>

In my work, I deal with motherhood from the perspective of mothers with severe visual impairment. I focused especially on parenthood planning, on the period of pregnancy, childbirth and stay in the maternity ward and on the care for the child from birth to the age of three. I was interested to find out, whether visually impaired mothers encounter prejudices on part of the well-sighted people, whether they were worried that they could give birth to a handicapped child, what are the difficulties that severely visually impaired mothers come across most often in the individual period of development of the child, if and how education of children is different from the perspective of visually impaired parents from the perspective of well-sighted parents and also whether the child growing up in a family with at least one visually impaired parent is deprived of something or whether, on the contrary, this family situation has any advantages for such child. The objective of my diploma thesis is to map out various aspects of life of visually impaired mothers with small children in the greatest detail, directly from the point of view of those women. I attempted to achieve this objective by means of a qualitative method research, in particular in the form of a structured interview with six visually impaired mothers.

A partir da utilização alegórica do conto A roupa nova do imperador, construímos analogias relacionadas à sustentação: da onipotência do bebê imperativo; das ilusões criadoras e das fantasias; e dos revestimentos fantasiosos sobre uma nudez psíquica constitutiva. Nas sobreposições fantasiosas, do bebê e da parentalidade, a interação foi considerada um encontro que abre espaço para a criatividade e o ineditismo da experiência. Logo, o cuidado, sustentado pela intersubjetividade e pela intercorporalidade, atestou o potencial transformador da interação e a importância das práticas parentais realizadas cotidianamente junto ao bebê. Isto posto, tivemos como objetivos investigar: o processo de constituição das interações diádicas e triádicas entre pai, mãe e bebê; as articulações entre o material de pesquisa e os referenciais familiares contemporâneos em torno da parentalidade, com ênfase na família constituída pelo casal heterossexual; a construção de um modelo de interação triádica; e as contribuições da metodologia utilizada. Sob a fundamentação teórica da Psicanálise, com destaque para a teoria winnicottiana, e dos Estudos Psicossociais, a pesquisa foi conduzida por uma adaptação do Método Bick de Observação Infantil, no qual duas tríades (pai-mãe-bebê), provenientes da cidade de Maceió/Brasil, foram observadas por três meses (6º ao 9º mês de idade dos bebês). Foram realizadas duas entrevistas semiestruturadas com cada casal. A análise conduziu uma discussão a respeito das categorias: processos interativos e práticas de cuidado; construção narrativa de setting; e, modelos de interação diádica e triádica. Os resultados apontam: a construção de práticas de cuidado e revestimentos parentais atualizados pelo encontro com o bebê, num processo de sustentação das interações diádicas e triádicas; e interações e revestimentos parentais que exerceram um caráter de sobreposição, com predominância de processos interativos diádicos em que pai e/ou bebê ocuparam posições de terceiros separadores e/ou excluídos. Concluímos que a possibilidade de um cuidado parental igualitário sustentou a existência de um modelo de interação triádica, enquanto o cuidado exercido a partir de um referencial parental hierárquico foi associado a um modelo de interação diádica / Considering the allegorical use of the tale The Emperors New Clothes, we have made some analogies to support: the omnipotence of an imperative baby; the importance of creative illusions and fantasies; and the coating process that creates fantasy on a constitutive psychic nudity. In the overlapping fantasies of the baby and the parent couple, interaction was considered to be an encounter in which space for creativity and novelty of experience is produced. Therefore, while care is supported by intersubjectivity and intercorporeality, it attests the transformative potential of interaction and the importance of the parental practices performed daily with the baby. Based on these remarks, this study aimed at investigating: the process in which dyadic and triadic interactions between father, mother and baby are produced; the relation between research material and references concerning parenting on contemporary family, with emphasis on families with heterosexual couples; the construction of a triadic interaction model and; the contributions of the methodology used. This study was based on Psychoanalysis, with emphasis on Winnicottian theory and Psychosocial Studies. Research was conducted using an adaptation of the Bick Method of Infant Observation, in which two triads (father-mother-baby) from the city of Maceió/Brazil were observed for three months (6th to 9th month of age of the babies). Two semi-structured interviews were conducted with each couple. Analysis was conducted through the following categories: interactive processes and care practices; narrative construction of settings; and, dyadic and triadic interaction models. Results show: the construction of care practices and parental coatings updated by the encounter with the baby, in a process that supports the dyadic and triadic interactions; and parental interactions and coatings that performed an overlapping aspect, with predominance of dyadic interactive processes in which father and / or baby occupied third-party positions and/or were excluded. We conclude that the possibility of an egalitarian parental care supported the existence of a triadic interaction model, while the care achieved by an hierarchical parenting reference was related to a dyadic interaction model

Objetivo: Analisar a influência dos cuidados maternos percebidos pelas mães sobre a frequência de aleitamento materno e aleitamento materno exclusivo, aos 3 e 6 meses de vida da criança em uma amostra expostas a diferentes ambientes intrauterinos. Métodos: Estudo observacional longitudinal, utilizando uma amostra de conveniência de mães e seus recém-nascidos, no qual os grupos foram classificados de acordo com as exposições maternas ocorridas no período gestacional, como diabetes mellitus, tabagismo ou desfecho do recém-nascido, como pequeno para idade gestacional, além de um grupo controle. Para algumas análises, os grupos em estudo foram subdivididos em grupo de condições intrauterinas adversas e grupo controle. A amostra foi selecionada em três hospitais de Porto Alegre, Rio Grande do Sul, Brasil, no período de 2011 a 2015. As mães e seus recém-nascidos foram avaliados ao nascimento, 7 e 15 dias, primeiro, terceiro e sexto mês de vida da criança. O aleitamento materno e o aleitamento materno exclusivo foram avaliados desde a entrevista do 15º dia até a entrevista do sexto mês de vida. Os questionários Parental Bonding Instrument (PBI), que avalia a percepção dos cuidados maternos e Edinburgh Postnatal Depression Scale (EPDS), que avalia a presença de sintomas depressivos após o parto, foram autoaplicados na entrevista do terceiro mês. Os testes utilizados foram ANOVA com post hoc de Tukey, teste Kruskal-Wallis com post hoc de Dunn, ANOVA de duas vias, ANCOVA e a Regressão de Poisson. As análises foram realizadas no programa Statistical Package for the Social Sciences versão 18.0. Resultados: A amostra foi composta de 212 duplas mãe/criança, 40 no grupo de mães com diabetes mellitus, 55 no grupo de tabagistas, 21 no grupo de nascidos pequenos para idade gestacional e 96 no grupo controle. A associação entre cuidado materno e amamentação entre os grupos em estudo mostrou que as mães que não praticavam mais o aleitamento materno no 3º mês de vida da criança apresentaram maiores escores na percepção de proteção e menores escores na percepção de cuidados maternos do que aquelas crianças que estavam em aleitamento materno exclusivo (p=0,038; p=0,017, respectivamente). O grupo controle apresentou maior escore na percepção de cuidados e menor escore na percepção de proteção materna em relação ao grupo de ambientes intrauterinos adversos (p=0,005, p=0,049, respectivamente). Em relação aos resultados da análise de regressão de Poisson entre amamentação, grupos, PBI e EPDS os dados mostram que, a cada um ponto a mais no protocolo de EPDS, o risco de não amamentar até 3 meses aumenta em 10,4% e até os 6 meses aumenta em 4,7% (p<0,001 e 0,004, respectivamente). Em relação ao aleitamento materno exclusivo, a cada um ponto a mais no protocolo de EPDS, o risco de não amamentar até 6 meses aumenta em 5,4% (p=0,002). As puérperas que perceberam restrição de carinho de suas mães aos 6 meses, apresentaram risco de 2,42% em relação à categoria de cuidado ótimo para não amamentar. Aquelas mães que perceberam suas mães como negligentes, apresentaram tendência de maior risco de 2,53% em relação à categoria de cuidado ótimo para não amamentar aos 6 meses de vida da criança. Conclusão: Os achados deste estudo sugerem que o estilo parental de baixo cuidado e de superproteção percebidos durante a infancia, interfere na frequencia do aleitamento materno e leva a sintomas depressivos após o parto. Demonstram, ainda, que os sintomas depressivos maternos após o parto influencia na frequencia da amamentação. / Objective: To analyze the influence of maternal care perceived by mothers on the frequency of breastfeeding and exclusive breastfeeding at 3 and 6 months of the child's life in a sample exposed to different intrauterine environments. Methods: A longitudinal observational study used a convenience sample of mothers and their newborns. They were classified according to maternal exposure occurring during pregnancy, such as diabetes mellitus, smoking or outcome newborn, the small for gestational age, and a control group. For some analyzes, the study groups were divided into two groups: the group of adverse intrauterine conditions and control group. The recruitment of participants was in three hospitals in Porto Alegre, Rio Grande do Sul, Brazil, from 2011 to 2015. The mothers and their newborns were evaluated at the newborns birth, 7 and 15 days, first, third and sixth month of child’s life. Breastfeeding and exclusive breastfeeding was evaluated from the 15th day to the sixth month of life, through questionnaires. The Parental Bonding Instrument questionnaires (PBI), which evaluates the perception of maternal care and Edinburgh Postnatal Depression Scale (EPDS), to assess the presence of depressive symptoms after delivery, were self-administered in the third month interview. The statistical tests used were ANOVA one-way with post hoc Tukey, Kruskal-Wallis test with post hoc Dunn, The two-way ANOVA, ANCOVA test and Poisson regression. Analyzes were performed using the Statistical Package for the Social Sciences version 18.0. Results: The sample was composed of 212 mothers with their child, 40 pairs in the diabetes mellitus group, 55 in the smokers group, 21 in small for gestational age group and 96 in the control group. The association between maternal care and breastfeeding among study groups showed that mothers who no longer practiced breastfeeding in the 3rd month of the child's life had higher scores in the perception of protection and lower scores in the perception of maternal care than those children who were in exclusive breastfeeding (p = 0.038, p = 0.017, respectively). The control group had higher scores of perceived care and lower perception of maternal protection in relation to the adverse intrauterine environment group (p=0.005, p=0.049, respectively). Regarding the results of the Poisson regression analysis between breastfeeding groups, PBI, and EPDS data show that each additional point on the EPDS protocol, the risk of not breastfeeding up to 3 months increased by 10.4% and up 6 months increases by 4.7% (p <0.001 and 0.004, respectively). Compared with exclusive breastfeeding, each additional point on the EPDS protocol, the risk of not breastfeeding up to 6 months increased by 5.4% (p = 0.002). The mothers realized that restriction affection from their mothers at 6 months had a risk of 2.42% compared to the great care category to not breastfeed. Those mothers who perceived their mothers as negligent tended to increase the risk of 2.53% compared to the great care category for not breastfeeding at 6 months of child's life. Conclusion: The findings of this study suggest that low care and overprotection parenting style perceived during childhood, interfere with the frequency of breastfeeding and leads to depressive symptoms after delivery. They also demonstrated those maternal depressive symptoms after birth influences breastfeeding frequency.

Environmental gradients can help shed light on the evolution of life history strategies such as parental investment. Parental investment is crucial for the fitness of many species. In this thesis, I examine reproductive investment dynamics in the Eurasian blue tit (Cyanistes caeruleus) in the French Pyrenees and assess potential differences in reproductive measures across an altitudinal gradient that creates variation in environmental “harshness”. Further, I investigate fine-scale aspects of bi-parental care, such as investment tactics in current reproduction, and sex differences in contributions to offspring care. To do so, I used a mixture of observational and experimental data, collected over a total of six breeding seasons from over 500 blue tits nests. I showed that breeding conditions are “harsher” due to colder temperatures with increasing elevation, leading to changes in reproductive timing and output. I found that increasing altitude leads to decreased hatching success. Nevertheless, clutch size and brood mortality is comparable across the gradient. A shift to a lower, but qualitatively comparable reproductive output may be part of a slower “pace of life” strategies pursued at high relative to low altitudes. From experimental data, I also found that parental investment is positively linked across different phases within one reproductive attempt. Finally, in line with theory, a temporary brood manipulation revealed that parents balance the benefits and costs of reproduction by partially compensating for changes in brood size. Parents also responded in similar ways to brood size. Overall, the findings presented in this thesis highlight the importance of mechanisms to fine-tune reproduction to maximise reproductive fitness. I suggest that initial reproductive decisions such as timing and amount of offspring produced heavily shape the success of a reproductive attempt. These results have implications for current versus future reproductive trade-offs in life history theory, in particular for short-lived species.