Avian Flight Initiation Distances in Urban Habitat Islands

  • 章 肖祺

Student thesis: Master's Thesis


With the effect of industrialization the entire world is becoming progressively urbanized thus concerns for biodiversity and ecosystem health in urban areas are receiving significant attentions Urban parks serve not only for human recreation but also can be critical habitats for urban wildlife Yet conflicts with human recreational needs and disturbances may lead to negative impact on individual wildlife and biodiversity Birds are one of the commonest vertebrates in urban areas and are highly sensitive to environmental changes Thus birds are often good indicators of ecological conditions in urban areas Immediate escape flights in response to predators or other external stressors are the typical behavioral responses of birds which can have carry-over effects on foraging and feeding success home range size reproductive decisions and body condition Flight initiation distance (FID) refers to the distance that animals being away from an approaching predator while starting to flee It represents a trade-off between the avoidance of life-threatening hazards and behaviors that may increase fitness FIDs can serve as a quantitative measure of a bird’s tolerance to threats or human disturbance and may suggest how well a bird has been adapted to chronic environmental stress Studies on birds’ FIDs in urban areas not only aid to our understanding of mechanisms behind this behavior but also help contribute to avian conservation in human-modified settings under the current trend of global environmental changes Eurasian tree sparrows are native species in Taiwan extremely common in urban areas and are constantly associated with human settlements and activities However the populations of tree sparrows are decreasing around the world In addition common myna an invasive species introduced to Taiwan in the 1970s is also commonly seen in urban areas Bird surveys had suggested that the mynas’ population soared in western Taiwan which will probably pose a threat to native bird species like sparrows Thus sparrows and mynas will be suitable species for the study of urbanization effect on wild birds This study tested hypotheses that avian FIDs are affected by avian characteristics and environmental factors like park’s size urbanization degree vegetation structure and human disturbances From November 2016 to March 2017 I surveyed FIDs of sparrows and mynas in 48 parks of three categories of areas that were selected randomly from Tainan City Moreover I measured the area degree of urbanization vegetation structures pedestrian density and dog density of each park and birds’ flock sizes as well Finally using Mann-Whitney U test differences in sparrows and mynas’ FIDs flock sizes and habitat preference were studied Using linear regression and stepwise multiple regression to study effects between FIDs and avian characteristics or environmental factors A total of 446 FIDs were record including 239 sparrows’ FIDs and 207 mynas’ FIDs Sparrows displayed significantly shorter FIDs than mynas but with smaller variation meanwhile mynas had FIDs that were more flexible Sparrows’ mean flock size was significantly larger than mynas Pedestrian density and urbanization degree were negatively related to both mynas’ and sparrows’ FIDs and they are the most and second important factors that related to FIDs The result also indicated that the common mynas compared to the tree sparrows preferred the environment with less tree and shrub coverage more grass coverage and lower pedestrian density The distances to the nearest cover (DNC) and grass coverage near birds were positively related to both mynas and sparrows’ FIDs Unleashed dogs adversely affect both species; while leashed dog density interestingly had little effect on either species’ FIDs For sparrows parks’ average motorcycle density was positively correlated with their FIDs For mynas light condition was significantly correlated with their FIDs My study indicates that mynas were less tolerant to pedestrians than sparrows The larger variation in mynas’ FIDs may indicate that mynas have a better learning ability for different environments than sparrows which may partly explain the reasons for mynas invasion More potential refuges for birds like trees and shrubs and less unleashed dogs may help reduce the impacts of disturbances on wild birds As for the mean shrub coverage of Tainan parks was low and unleashed dogs were very common Accordingly the appropriately increase of Tainan parks’ shrub coverage is recommended by the author and I advocate citizens to leash the dogs while walking dogs in parks; as well as do not abandon their pets to reduce the disturbance to urban wild fauna
Date of Award2018 Sep 1
Original languageEnglish
SupervisorYa-Fu Lee (Supervisor)

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