Doctor of Philosophy
School of Biological Sciences
Delgado-Velez, Carlos Andres, Spatial patterns of bird-parasite interactions along an urbanisation gradient, Doctor of Philosophy thesis, School of Biological Sciences, University of Wollongong, 2015. https://ro.uow.edu.au/theses/4436
Urbanisation is a fast growing phenomenon worldwide which has direct and indirect impacts on biodiversity. Urbanisation affects particular species but also biotic relationships and interactions. Changes in host-parasite interactions have the potential to be one of the important consequences of urbanisation, influencing the species able to exploit, establish and succeed in urban landscapes. However, how urbanisation influences the prevalence and impact of parasites and the susceptibility of different birds has not been studied in detail, especially in areas such as Australia and many Oceanic islands. The risk of parasitism is predicted to increase in cities due to changes in climatic conditions, habitat loss, habitat conversion, increased temperature, fragmentation and a greater presence of human-modified landscapes.
Integrating ecological and physiological approaches, this thesis analyses the distribution and diversity of three groups of bird parasites along an urbanisation gradient in New South Wales, Australia, and investigates how parasites and haematological and body condition may influence the structure of urban-bird communities. Given the paucity of information available in Australia, this thesis provides an inventory of a portion of Australia parasite fauna and tested whether parasite loads could influence the ability of some birds to inhabit cities. I particularly focused on two species of birds which are not particularly common in urban areas.
Contrary to expectations, my research does not support a positive association of urbanisation and bird parasites, nor does it identify detrimental effects on the immune system and body condition of the host. Instead, results suggest that urbanisation does not necessarily result in high parasitism and lower immune system in urban-sensitive birds. This thesis found that some parasites such as louse flies, ticks and haemosporidians are less prevalent (or even disappear) while others might be either more prevalent (e.g. Coccidian parasites) or kept unchanged in urban areas (e.g. lice). My study was unable to detect a general pattern of loss of body condition associated with urban development for the species sampled suggesting that urbanisation effects are complex and might be site-, parasite- and host-specific related.
This thesis identified four new lineages of haemosporidians, indicating great potential for Australian bird parasites to be fundamentally unique. The poor knowledge available on the relationship among parasites and wildlife still requires further consideration across more species in order to determine how parasites are affected by urbanisation and whether they play a role in the establishment and success of birds in cities. At present parasite load does not appear to be a cause of the decline in urban birds.