Animals experience a variety of environmental stressors, for example
climate and habitat change. These changes can alter the distribution and
population dynamics of species indirectly through disruption of behavioural
processes, including foraging. Collecting behavioural data, such as foraging
tracks, from multiple individuals can help to identify how response to habitat
change, is driven by factors such as resource distribution, intra-specific
competition and intrinsic factors such as sex and age. This thesis combined
behavioural and dietary information collected from individual European nightjars
Caprimulgus europaeus, to analyse variation in behaviour amongst the
population, in response to habitat change and the consequences this might have
in terms of future change and for beneficial management.
This population of nightjars showed significant individual variation in home
range size and habitat selection therein. Home ranges sizes increased by 1% and
decreased by 9% in wetland and newly cleared habitat respectively. This
indicated that although birds possess individual preferences for specific habitat
types, there are foraging constraints that affect multiple individuals. Foraging
behaviour changed most strongly in relation to habitat type, NDVI and more
weakly in relation to the lunar cycle and temperature. Time spent foraging
increased in cleared habitat (β: 0.03, R2 0.08, p: 0.07), which became more
available during the study. Males spent 33% of their time foraging compared to
females which spent only 18.6% of their time foraging, representing differing
breeding roles. However, strong methodological influence was clear, whereby an
increase in the fix interval from 3 to 5 minutes caused a 39% increase in step
length, unaccounted for by year or habitat change. Individual diet composition
differed and changed between years, in response to prey availability, however
common species occurred in 40-50% of samples. Overall nightjars selected for
larger moths compared to local availability. Collectively, my results and
demonstrated flexibility at the population level and the potential to respond
positively to habitat. As a species specialising in a spatially- and temporally varying prey resource, maintenance of complex habitat mosaics that encourage a
wide diversity of moth and other flying insect species, along with the diversity of
habitat types to encourage breeding and survival of all individuals.
