Meeting Abstract
The impact of temperature on avian reproduction has been investigated from several angles, most recently focusing on shifts in phenology in relation to climate change. The major focus of these investigations has been on changes to egg laying and hatching dates, whereas changes in male fertility levels with environmental conditions remain largely unexplored. For birds, the role of temperature in mediating changes in sperm motility has only been evaluated in the context of artificial insemination. This ignores the potential impact that high ambient temperature may have on sperm stored just under the skin in the seminal glomerulus of passerine species. In the wild, zebra finches (Taeniopygia guttata) are known to suppress breeding in the hottest months of summer, and following short intense heatwaves (sustained periods > 40°C). To investigate the possibility that a reduction in sperm function might constrain reproduction in extreme heat conditions, we looked at changes in sperm motility and morphology over an experimental two-week heat exposure of 30° or 40°C in captive birds. Compared to the 30°C birds, males housed at 40°C showed consistently higher cloacal temperatures (averaging 2°C warmer). They also exhibited a decrease in average sperm swimming speed and the proportion of motile sperm across time, and a significant increase in the percentage of abnormal sperm. Our laboratory results are consistent with results we obtained from wild, free-living zebra finches breeding during a short-term heatwave (i.e. 3 days of 40-43°C). Our findings suggest that high climatic temperatures could potentially reduce fertility and limit the length of the breeding season of birds by impacting sperm quality. These results are particularly relevant in the context of an increasing frequency of heat waves resulting from climate change.
