Temporal patterns in avian ecology and behaviour – a multi-scale approach

<p><strong>Time is a fundamental aspect of nature that shapes life on Earth. Organisms have evolved biological rhythms to synchronize their behaviour and physiology with cyclical environmental fluctuations. Temporal ecological patterns are especially pronounced in birds, influencing key behaviours such as migration, breeding, foraging, and daily activity patterns. However, anthropogenic disturbances, such as species introductions, increased commercial aviation, and urbanization, disrupt the timing of cyclical natural events. In this thesis, I examined temporal patterns in avian ecology and behaviour in the context of natural and human-induced environmental variation across different ecological scales.</strong></p><p>Bird collisions with aircraft are a serious and increasing threat to human safety worldwide. In chapter 2, I investigated the biogeographical patterns in the seasonality of bird strikes. Strikes were generally higher in late-autumn and summer seasons on both hemispheres. Seasonal trends were not symmetrical between the hemispheres, as bird strikes in the Northern Hemisphere were more seasonally concentrated. Results suggested periods of peak bird strikes may coincide with the fledging season, while hemispherical asymmetry in the seasonality of bird strikes may correspond with the latitudinal differences in avian migration. These findings bridge a gap between aviation safety and macroecology, providing insights that could inform future wildlife hazard management strategies at airports.</p><p>In New Zealand, conservation initiatives have successfully restored threatened bird populations, enabling detailed studies of local ecological processes. In chapter 3, I analysed seasonal patterns in bird-plant interactions using a long-term dataset of a restored forest bird community in a mainland sanctuary. Flower and fruit visitation peaked at opposite times of the year, in spring and autumn, respectively. Flowers were available to birds for approximately half the year and fruits for the other half. Dietary diversity of birds was higher for fruits than for flowers. Seasonality in flower and fruit visitation was generally unrelated to peak periods in the consumption of individual plant species. Future use of this and other long-term datasets could be essential to evaluate the biodiversity outcomes of conservation strategies such as fenced sanctuaries through time.</p><p>The introduction of non-native plant species alters plant communities worldwide, requiring native animals to adapt their foraging behaviour to include novel food resources. In chapter 4, I examined seasonal foraging patterns of the New Zealand kākā (Nestor meridionalis septentrionalis) on native food resources, and on an exotic conifer with year-round canopy seed storage. Foraging frequency and dietary niche breadth of kākā were higher at certain times of year. Kākā exhibited seasonal shifts in their diet, sequentially switching between flowers, tree sap, fruits, and ground-foraged seeds, while consuming wood-boring invertebrates year-round. Additionally, kākā fed on radiata pine (Pinus radiata) seeds throughout the year, demonstrating dietary opportunism. As kākā disperse further into urban areas, understanding their dietary plasticity for novel resources may be essential for future conservation management.</p><p>In chapter 5, I investigated the nocturnal behaviour of wild kākā, which are typically considered to be diurnal birds. I compared the occurrences of different behaviours and vocalizations between night and day. Results demonstrate what is, to my knowledge, the first account of partial nocturnality in a parrot species. Approximately one in five kākā encounters occurred at night. Kākā engaged in a variety of behaviours and vocalizations during both day and night, with higher foraging observed during the day, and higher movement observed at night. These findings serve as a potential starting point for further studies on the effects of demographic factors such as age and sex, and other external factors such as level of urbanization, on this behaviour.</p><p>Together, these studies contribute to our understanding of temporal variation in avian ecology through a multi-scale approach, emphasizing the interconnectedness of natural and anthropogenic environments. The thesis provides novel insights into avian temporal trends, from global patterns in bird strikes to the daily activity of an endemic parrot. As disturbances like climate change and habitat modification continue to alter the timing of natural events, understanding their impact on avian behaviour and ecological interactions becomes increasingly crucial.</p>