Fatty acid profiles of eggs and nestlings of Great tit (Parus major): are there differences between growing up in the city or in the forest?

Abstract

Nowadays, urbanization is expanding over natural habitats, imposing changes on animal communities. Cities provide abundant supplementary food, but its nutritional are different from what birds can find in nature, for instance in the content of fatty acids (FAs). FAs fulfil important physiological functions, being essential in a multitude of processes throughout the life of animals. However, FAs are probably most crucial at early life stages, when cells and tissues are rapidly growing and developing. Exploring the differences in the FA profiles between urban and non-urban animal populations at early life stages is important to understand how urbanization affects bird communities through differences in diet. The aims of this study were to 1) identify the FA profile in Great tit (Parus major) egg yolk and blood plasma of nestlings, and to 2) compare these FA profiles between an urban and non-urban populations. In addition, we (3) test for differences in nestling morphological development between an urban and non-urban population, using the change in tarsus length between two stages of growth as proxy of overall growth. The final aim was to investigate the potential influence of FAs on growth: testing which, if any, functional classes of FAs showed a relationship with tarsus growth. Inter-population differences in FA profiles were found, for both eggs and nestlings. These differences may have an impact on the viability of the eggs, potentially constraining the development of the embryos or the nestlings, or even imposing metabolic diseases. Regarding FA profiles in nestlings, the balance between ω-6 and ω-3 polyunsaturated FA (PUFAs) was higher in the forest, and the same was true for the proportion of total PUFAs. The inflammatory response is influenced by the balance between ω-6 and ω-3 PUFAs, and peroxidative damage of total PUFAs can be induced by oxidative stress, inducing membrane dysfunction. However, further assessment is needed to determine if diet influences the oxidative and inflammatory status of the individuals, and whether maternal diet in cities is inducing changes in embryo development and nestling growth.

Popular Abstract

The impact of micro- and macro-nutrients from anthropogenic food sources on bird health

Urbanization is expanding throughout the world over natural habitats, imposing changes on bird communities among other animals. Habitat fragmentation and degradation, pollution and local climatic abnormalities are just some of the detrimental factors that birds have to deal with. Even though urban populations exhibit higher densities and survive better the winter, several negative effects of living in the city could be expected. So the importance of assessing how urban and natural populations differ, and understanding which are the mechanism operating, are crucial for conservation.

One key factor that influences bird communities is the disponibility of food, and cities are characterized by the provision of abundant supplementary food, in particular mixes of seeds with sunflower seeds as the most abundant. These mixes usually contain high levels of linoleic acid (n-6 polyunsaturated fatty acid, PUFA), oleic acid (n-9) and stearic acid (saturated fatty acid, SFA) and very low levels of n-3. The intake of dietary n-3 PUFAs is linked to health: low levels can result in malnutrition, and they also are regulators of complex metabolic- and immune-pathways. n-3 PUFAs downregulate generation of reactive oxygen species and free radicals, and up-regulate some of the protective antioxidant defenses such as glutathione, hence reducing oxidative stress.

The maternal diet may affect significantly the chick embryo development. An adequate proportion of both n-3 and n-6 fatty acids is needed for the successful development of the embryo, because some specific PUFAs are needed for an adequate development of some organs and immunoregulatory properties among others. For that reason the embryos have compensatory mechanisms to incorporate the adequate proportions, mechanisms that have evolved to compensate within a range of proportions from the diet, hence drastic deviations may reduce the viability of the eggs or constraining the development of the nestlings. Hence, modification of the dietary fatty acids of the females in the urban habitats could imply that the differences between populations are reflected since early stages of life. Therefore, exploring the differences in the fatty acid profile between urban and rural populations at these early stages, and the relation of these potential differences with the oxidative and antioxidant status, are key questions to understand how urbanization is affecting bird communities. During my thesis I will explore the differences in the fatty acid profile between eggs and nestlings from urban and rural habitats. The model species of the study are Great Tit (Parus major), one of the most common species in Swedish cities and forests. In addition, they breed in nest boxes, providing an easy way to get information.


Advisor: Caroline Isaksson
Master´s Degree Project 60 credits in Molecular Ecology 2015
Department of Biology, Lund University

• author: Toledo, Alejandra
• supervisor: Caroline Isaksson; Martin Andersson
• organization: Degree Projects in Biology
• course: BIOP34 20141
• year: 2015
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 5277203
• date added to LUP: 2015-04-22 11:25:03
• date last changed: 2015-04-22 11:25:03