The project has finally come to an end. The team carried out the following activities in the third and final year of the grant.
The PhD Student spent three months at their field site near Askham in the Kalahari Desert. During this time, she obtained behavioral and body temperature data for two species: Namaqua Dove and White-backed Mousebird, using the same approaches as during the first and second field seasons. The data collected consisted of a) body temperatures using VHF temperature-sensitive transmitters, b) behavioral observations to quantify the temperature-dependence of heat dissipation behavior, and c) experimental manipulations of hydration status to test hypotheses concerning the interacting effects of hydration status and thermoregulation.
Behavioral analyses and body temperature data collected so far reveal several key findings. One major question was establishing whether HD50 values vary between captive and free-ranging birds. Their data suggests that, for all but Cape Turtle-Doves, HD50 is either slightly higher or slightly lower under captive conditions. Omnivorous species tend to have lower HD50 in captivity whilst granivores and frugivores have higher HD50 in captivity. Of the four species we were able to examine, no changes in heat dissipation behavior with water restriction were observed for the two frugivorous species. For these two species HD50 on water restricted (WR) days was almost identical to ad libitum (AL) HD50, where water was freely available. There remains more than 10 °C variation in captive HD50 values, providing the interspecific variation necessary to test hypotheses concerning the physiological basis of these behavioral differences. Frequency distributions of daytime body temperatures for eight species reveal relatively high body temperatures, with modal values between 41 and 43 C for all species investigated.
As expected, the three columbids (i.e., doves and pigeons) appear to show slightly lower values compared to passerines. Preliminary data of body temperature for the water restriction experiments do not reveal any obvious differences in patterns of thermoregulation on hot days between conditions of ad libitum water availability (AL) and water restriction (WR). There appear to be no major shifts in modal body temperature with water restriction for any species tested. There are however interesting interaction effects between air temperature and water restriction, suggesting that on only on water restricted days body temperature increases with increases in air temperature.
In summary, progress remains good. They have now collected data for nine species, which was the total envisaged at in the original proposal. The PhD student is in the process of analyzing this very large data set (the number of body temperature data, for instance, runs into many thousand for each species).
|Michelle and Nicholas discovering various Arizona desert species during their behavioral data collection fieldwork in Arizona, July 2014. Photo courtesy: Dr. McKechnie.|