Effects of physical and social environment on zebra finches’ foraging intensity
The zebra finch (Taeniopygia guttata) is the most widely used passerine bird in captive research, yet little work has been done in the wild where physical and social conditions are more variable and their behaviour can be investigated in an ecological context. Zebra finches forage on the ground and are vulnerable to predation by a range of terrestrial and aerial predators. In this thesis, I explore how the physical and social environment affects their foraging decisions in captivity and in the wild. The decision to feed in a particular patch is an attempt to optimise the costs and benefits of feeding at that location. I used giving-up densities (GUD) – the density of food remaining in a patch after the forager(s) have exploited it, to measure the perceived risk of zebra finches to a variety of experimental treatments. In captivity, I investigated how zebra finches’ foraging intensity responded to characteristics of the captive environment such as the availability of perches, cover, and ground substrate. In the wild, I examined how their foraging intensity was affected by the distance to natural cover (vegetation) or their visual fields. I also explored effects of the local neighbourhood density of zebra finches in the wild. I further investigated captive zebra finches’ foraging intensity in different sized groups, as a function of the proximity to, and behaviour of neighbouring flocks. I show that zebra finches forage more intensively when they are close to vegetation and perceive cover as protective. I also found that foraging intensity increased non-linearly with group size and mass and sex mitigated how social and physical environments affected foraging intensity. Overall, my finding suggest that while foraging, zebra finches place greater emphasis on their social, compared to physical environments. My thesis highlights the importance of taking into account a wide range of social factors when investigating foraging decisions by animals.