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- Jensen, Johan Kjellberg, et al.
(author)
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Urban tree composition is associated with breeding success of a passerine bird, but effects vary within and between years
- 2023
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In: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 201:3, s. 585-597
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Journal article (peer-reviewed)abstract
- Birds breeding in urban environments have lower reproductive output compared to rural conspecifics, most likely because of food limitation. However, which characteristics of urban environments may cause this deficiency is not clear. Here, we investigated how tree composition within urban territories of passerine birds is associated with breeding probability and reproductive success. We used 7 years of data of breeding occupancy for blue and great tits (Cyanistes caeruleus; Parus major) and several reproductive traits for great tits, from 400 urban nest boxes located in 5 parks within the city of Malmö, Sweden. We found that tits, overall, were less likely to breed in territories dominated by either non-native trees or beech trees. Great tit chicks reared in territories dominated by non-native trees weighed significantly less, compared to territories with fewer non-native trees. An earlier onset of breeding correlated with increased chick weight in great tits. Increasing number of common oak trees (Quercus robur) was associated with delayed onset of breeding in great tits. Notably, as offspring survival probability generally increased by breeding earlier, in particular in oak-dominated territories, our results suggest that delayed onset of breeding induced by oak trees may be maladaptive and indicate a mismatch to this food source. Our results demonstrate that tree composition may have important consequences on breeding success of urban birds, but some of these effects are not consistent between years, highlighting the need to account for temporal effects to understand determinants of breeding success and inform optimal management in urban green spaces.
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| 2. |
- Jensen, Johan Kjellberg
(author)
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Understanding the urban ecosystem : interactions between plants, animals, and people
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Cities are the pinnacle of human change to the environment, creating unique types of ecosystems which present many challenges to local organisms: habitat fragmentation, introduced species, and various pollutants. Being crucibles of anthropogenic effects, urban ecosystems offer opportunities to understand how humans impact nature. Moreover, since a majority of the world’s population resides in cities today, urban nature has become the most frequently encountered type of nature in everyday life. Studying urban ecology therefore has the potential to shed light on both sides of the interaction between people and nature. In this thesis, I used an interdisciplinary approach to explore the effects of urbanization on vegetation, arthropods, birds, and people. Studying several taxa, and using methods from Ecology, Physiology, Sociology, and Aerosol technology, I aimed to develop a holistic and multifaceted understanding of the urban ecosystem. Specifically, I investigated urban trophic interactions, how air pollution and nutrition may affect animal physiology, and how local wildlife influences children’s well- being and perception of nature. I outline three key findings from the six papers forming the basis of my thesis: (1) plant origin is a strong determinant for urban arthropod abundance and breeding success of birds. Namely, non-native trees show a negative effect, with a magnitude and consistency over years, which indicates that vegetation composition is a key driver limiting animal populations in cities. (2) urban birds are constrained by food quality (specific nutrients) during breeding, likely due to low abundances of certain arthropods in cities. Moreover, high quantities of low-quality food (e.g., from human sources) do not compensate for the urban birds’ dietary deficiency and may instead lead to reduced capacity to mount physiological responses to deal with air pollutants or infections. (3) children’s relation to nature (attitude and knowledge) is not impacted by urbanization but predicted instead by socioeconomic factors and the quality of nature close to their homes. These local differences call for more detailed approaches when studying cities since both social and environmental variation within urban areas can be more consequential than general divides. In this thesis, I demonstrate the importance of native vegetation in cities and food quality for urban animals. Local wildlife influences people and by better understanding the urban ecosystem, we are one step closer to building cities that will allow future generations to learn about species and enjoy nature near their homes.
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| 3. |
- Kjellberg Jensen, Johan, et al.
(author)
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Quantifying the influence of urban biotic and abiotic environmental factors on great tit nestling physiology
- 2023
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In: Science of the Total Environment. - : Elsevier B.V.. - 0048-9697 .- 1879-1026. ; 859
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Journal article (peer-reviewed)abstract
- There is a long history of avian studies investigating the impacts of urbanization. While differences in several life-history traits have been documented, either between urban and rural populations or across generalized urbanization gradients, a detailed understanding of which specific environmental variables cause these phenotypic differences is still lacking. Here, we quantified several local environmental variables coupled to urbanization (air pollution, tree composition, ambient temperature, and artificial light at night [ALAN]) within territories of breeding great tits (Parus major). We linked the environmental variables to physiological measures of the nestlings (circulating fatty acid composition [FA], antioxidant capacity and an oxidative damage marker [malondialdehyde; MDA]), to garner a mechanistic understanding of the impact of urbanization. We found that the antioxidant capacity of nestlings decreased with higher numbers of oak trees and levels of PM2.5 (airborne particulate matter with a diameter < 2.5 μm). Furthermore, the ratio of ω6:ω3 polyunsaturated FAs, important for immune function, was positively correlated with PM2.5 concentration, while being negatively associated with ambient temperature and number of non-native trees in the territory. Body mass and wing length both increased with the number of local oak trees. We also show, through a principal component analysis, that while the environmental variables fall into an urbanization gradient, this gradient is insufficient to explain the observed physiological responses. Therefore, accounting for individual environmental variables in parallel, and thus allowing for interactions between these, is crucial to fully understand of the urban ecosystem. © 2022 The Authors
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