|
|
The role of ultraviolet light in communication of birds
Šulc, Michal ; Sedláček, Ondřej (advisor) ; Albrecht, Tomáš (referee)
Recently, it has been found that the visual system of birds and humans differ remarkably, especially in the ability to perceive ultraviolet radiation. This component of the spectrum significantly affects various types of the birds' behaviour. UV reflection may be an indicator of the qualities of males, i.e. females often prefer individuals with expressive UV ornamentation. Likewise, parents can distribute the delivered food unevenly among their nestlings, depending on the nestlings' reflection of ultraviolet radiation. Recent studies also showed that the hosts of brood parasites may use UV spectrum as a key for recognizing the parasitic eggs from their own. The aim of my bachelor thesis is to review the current knowledge of the influence of UV radiation on sexual selection of birds, the interaction between parents and offspring and interactions between brood parasites and their hosts.
|
|
|
Extra-pair fertilizations and the opportunity for sexual selection in Barn swallows
Michálková, Romana ; Albrecht, Tomáš (advisor) ; Šálek, Miroslav (referee)
Generally it is assumed, that sexual selection drives the evolution of elaborate traits. The strength of sexual selection has traditionally been attributed to varinace in reproductive success among individuals. This variance is mainly caused by the number of mating partners and the number of sired offspring. Both males and females can increase their reproductive success by alternative reproductive strategies - extrapair copulations and intraspecific brood parasitism. In our study we tested the relationship between male ornamentation and success in extra-pair and within-pair paternity and the total male reproductive success in barn swallow (Hirundo rustica), a socially monogamous species with high levels of extrapair paternity. The results suggest more colourful throat to indicate male reproductive success. Dark rusty males were less often cuckolded and they have higher total fertilization success than drab ones. Tail length did not affect neither within- nor extra-pair fertilization success, however, previous studies have concluded that reproductive success of male barn swallows is positively related to the tail ornaments. Our results confirm that extra-pair paternity considerably increase variance in reproductive success among barn swallow males. We show that within-pair success may increase the...
|
|
|
Significance of predation for breeding ecology and conservation in shorebirds
Kubelka, Vojtěch ; Šálek, Miroslav (advisor) ; Albrecht, Tomáš (referee) ; Hötker, Hermann (referee)
Predation is the most common cause of reproduction failure and it strongly influences breeding performance in birds, impacting the whole species population dynamics as well as it represents a major force in the evolution of avian life-history strategies. Investigating the factors driving predation rates, or quantifying predation consequences, is highly relevant for evolutionary ecology as well as for species conservation, especially in a rapidly changing world. In this dissertation, I investigate links between nest and chick predation, environmental factors, life-history and anti-predatory strategies, together with consequences for population dynamics and conservation. I use shorebirds as a uniquely suitable model system for three reasons: i) they are globally distributed; ii) have predominant ground nesting strategy and high interspecific similarity in nest appearance to potential predators; iii) are sufficiently well- studied in terms of nest predation all over the world. In the two first sections of this dissertation, Predation in the agricultural landscape and Interspecific interactions and anti-predatory strategies, Chapter 2 supports the thermoregulatory hypothesis of nest lining size rather than anti-predatory adaptation. Chapter 3 discusses, from the perspective of predation, the twofold...
|
|
| |
|
|
Ornament expression and lifetime reproductive success in male barn swallows (Hirundo rustica)
Wnuková, Lucie ; Albrecht, Tomáš (advisor) ; Klvaňová, Alena (referee)
Within a lifetime of an individual, there are changes in the organism leading to an an impairment of phenotype, survival and reproduction. The expression of phenotypic traits often increases with age. Higher expression of these traits in the young age can lead to decreased probability of survival till the next season, influencing reproductive success of an individual. That is why organisms are challenged with trade-offs, when they have to allocate their limited resources either into the reproduction in form of expression of extravagant sex ornaments or into the life span. If the ornament evolved as a handicap, its exaggerated size could reduce viability of low quality individuals. Therefore, the ornament becomes a predictor of quality of its bearer and its size indicates the ability to survive till the next season. Both sexual ornamentation and inter-individual variation in life span may result in differences in reproductive success (fitness) and targeted by sexual or natural selection. Variability in reproductive success, mainly in monogamous species, can be increased also by sexual promiscuity and extra-pair mating and extra-pair copulations. This strategy can increase the opportunity for selection of traits that play role in choosing of extra-pair mate. In this work, I focused on two potential...
|
|
|
Latitudinal trend in feather growth rates and steroid hormone concentrations in avian feathers
Brzobohatá, Tereza ; Albrecht, Tomáš (advisor) ; Sedláček, Ondřej (referee)
Avian life histories range along the axis from slow to fast, with slow life histories being characterized by greater investments in future reproduction, and fast by greater investments in current reproduction. The concept of pace-of-life syndromes refers to the coevolution of life strategies and related physiological, immunological and behavioral traits. Avian species from tropical areas are characterised by slower life histories (longer parental care, later maturation, smaller clutches, reduced metabolic rate) when compared to temperate zone species. Within this latitudinal gradient, investments in the total amount (weight) of body feathers have also been shown to be reduced in tropical birds. It remains unclear, however, whether feather growth itself follows this latitudinal pattern, and is slower in tropical species. Tropical birds have lower basal levels of corticosterone and testosterone, however available studies are based mainly on analyzes of hormone concentrations from plasma. The first aim of this diploma thesis was to evaluate differences between tropical (Cameroon) and temperate zone (the Czech Republic) passerine species in investments in tail feather growth by using methods of comparative ptilochronology. The second aim of the diploma thesis was to analyze concentrations of steroid...
|
|
|
Physiology of Carotenoids Metabolism and Ornamental Signalisation in Animals
Gabrielová, Barbora ; Albrecht, Tomáš (advisor) ; Černý, Ondřej (referee)
This theses deal with the use and utilization of carotenoids in secondary ornamentation, particularly in birds. Carotenoids have an important role in animal organisms, and the honesty of carotenoid-based signalization has traditionally been ascribed to anti-oxidant functioning of carotenoids. However, this view has been changed recently showing the potentially harmful effect of carotenoids. The deposition of carotenoids in ornamentation is driven not only by carotenoid intake, but also by physiological processes within the organism. Importantly, when the conditions are suboptimal (and the oxidative stress increases) unstable long aliphatic chains of carotenoids derive into highly reactive non-colorful apo- carotenals. Hence carotenoids may act as classical handicaps, potentially harmful to organism, and this view changes our understanding of honesty of carotenoid-based signalization. The theses focus on summarizing the current knowledge on physiological functions of carotenoids and how they affect secondary coloration, and consist of three chapters. In the first one the basic description of carotenoids is provided, along with an overview of carotenoid classification. The second chapter deals with physiological aspects which affect the carotenoid intake, metabolisation, transport to ornaments, and hypotheses...
|
|
|
Acoustic and visual signalization in birds: Identification of key components and their role in sexual selection
Mikula, Peter ; Albrecht, Tomáš (advisor) ; Svobodová, Jana (referee)
This bachelor thesis is focused on describing visual and acoustic signals in birds and their potential role in the process of sexual selection. Evidence that acoustic and visual signals are sexualy selected is summarized. The key characters that can be utilized in comparative studies are determined. In the first chapter of the thesis are briefly outlined mechanisms of sexual selection and evolution of costly secondary male ornamentation. In the second chapter basic avian ornaments (colouration, acoustic signals) are described. The emphasis is on visual and acoustic structures which are costly to produce and serve as honest indicators of individual condition. The third chapter is devoted to the possible trade-offs between visual and acoustic signalization in birds. The last section summarizes hypotheses about potential relationships between visual and acoustic signalization (and trade-offs between these two types of ornamental traits) in relation to changing environmental conditions.
|
|
|
Investment in reproduction and nest defense in waterfowl
Javůrková, Veronika ; Albrecht, Tomáš (advisor) ; Remeš, Vladimír (referee) ; Weidinger, Karel (referee)
Investment in reproduction is considered to be crucial component of life history traits. Reproductive success is however constrained by generally unpredictable environmental conditions. Based on "bet hedging" theory, individuals are forced to eliminate such unpredictability via the mixed strategy to maximize their long-term fitness. Predation represents underlying factor affecting individual reproductive success, and it undoubtedly lies behind the evolution of alternative reproductive strategies such as extra-pair paternity and conspecific brood parasitism. Behavioral mechanisms related to nest defense are thought to be investment in reproduction in accordance with trade-off between actual and residual reproductive value. Despite the extensive interest in the principles associated with parental investment into the nest defense, studies describing in detail the pattern of particular antipredator strategies are rare. Similarly, mechanisms responsible for maintenance of egg- viability during prolonged egg-laying period in species delayed the onset of incubation are poorly understood. In accordance with mentioned themes, this thesis includes publications aimed at aspects of reproductive biology and antipredator behavior in Mallards (Anas platyrhynchos). Particular publications concretely documented: a)...
|
|
|
Condition dependence of sexually selected ornaments in birds
Tomášek, Oldřich ; Albrecht, Tomáš (advisor) ; Verhulst, Simon (referee) ; Šálek, Miroslav (referee)
Sexual ornaments important for mating success in many species are often assumed to evolve as condition-dependent signals of individual quality. Ornament expression can be associated with age and survival, thereby signalling individual viability. Here, we have tested viability signalling function of tail streamers and their importance for within-pair and extra-pair fertilisation success in the European barn swallow (Hirundo rustica rustica). In contrast to previous studies on this subspecies, our data suggest that tail length is not associated with fertilisation success in our population. Instead, the most important predictors of within-pair and extra-pair fertilisation success were female and male age, respectively. Our data supported viability signalling function of male tail streamers, as documented by age-related within- individual increase in their length. There was no evidence for senescence in this trait. Contrary to some previous studies, the viability signalling function of tail streamers was further supported by observed selective disappearance of males with shorter tails. Several physiological mechanisms have been proposed as maintaining signalling honesty. Among them, oxidative stress from highly reactive species (RS), including free radicals, attracted a considerable attention. Given...
|
guest ::
