IN THIS ISSUE...
RESEARCH & LAND MANAGEMENT
- Game Bird Seminar/Fall Field Day
- Carolina Field Day at Heatherstone Farm
- Experimental Wiregrass Plots Remapped
- Red-cockaded Woodpeckers on Dixie Plantation
- Hurricane Michael Impacts Woodyard Hammock
- Bobwhites in the Eye of the Storm
Fall 2018 | Vol 11 | No 4
Bobwhites in the Eye of the Storm
While the devastating effects of hurricanes headline the news and social media, from wind-torn towns and cities to flooded interstates and washed out roadways, their impacts on wildlife, and bobwhite in particular, are frequently part of the conversation during or following such events. Numerous studies have shown that birds have an uncanny “sixth sense” for detecting storm events well in advance—as much as 5–7 days—of approaching storms. Birds, like mammals, can detect changes in barometric pressure, and are also believed to detect infrasound (low frequency sound) emitted from large storm events like hurricanes and tornados. These built-in detection devices provide an innate mechanism to alter behavior in response to approaching storms. In bobwhites, we observe both adults and broods shift into heavy feeding mode in preparation for hurricane events.
Figure 1a&b.Two radio-tagged broods intensively monitored (checked every 30 minutes during daylight hours) on 2 separate days. Day 1 was a normal daily foray, 3-weeks prior to a hurricane event (location marked by red flags) and Day 2 was 1 day prior to a hurricane event (locations marked by green flags). During normal daily movement bouts 29% (left figure) and 49% (right figure) of brood locations were in fields exhibiting foraging behavior compared to 71% and 67% the day prior to the hurricane event.
While some birds leave the area in the path of a hurricane altogether, bobwhites ignore the evacuation notice and hunker down, seeking cover to wait out the storm. How they fare, we have discovered, is largely dependent on their age and the amount of rainfall. This year we experienced two hurricanes on our study sites being monitored with radio-tagged birds: one in North Carolina with Hurricane Florence and, of course, the more recent Hurricane Michael, here closer to home in the Red Hills and Albany regions. I am pleased to report that the effects of Hurricane Michael on direct bird mortality was negligible on the bobwhite population. We did not lose a single radio-tagged adult bird on any of our three study sites (Tall Timbers, Dixie, and Albany) to the storm. In addition to adult birds, we had several radio-tagged chicks being monitored during this time on Tall Timbers and Dixie Plantation. We observed less than 4% loss of our radio-tagged chicks due to the storm, which is phenomenal.
Hurricane Florence, on the other hand, was much more impactful on both adults and chicks. We observed about a 20% mortality of adults directly associated with the storm event in North Carolina. Bobwhite chick loss was also much higher on our North Carolina study site where the majority (nearly 100%) of chicks less than 4 weeks of age succumbed to the impacts of the storm. In addition, we observed ~55% loss of chicks that were 4-8 weeks of age, while chicks greater than 8 weeks of age fared much better and similar to adult birds. Nesting was also impacted by Hurricane Florence, with about half of our nests being destroyed by flooding and/or induced abandonment, likely related to stress.
A big difference on the level of impact between these two major storm events on bobwhites was timing (age of chicks) and amount of rainfall. The majority of the chicks on the ground during Hurricane Michael were 4+ weeks old, compared to variable chick ages in North Carolina, where some were as young as 1 week old when Hurricane Florence hit. Also, reports of 35 inches of rainfall resulted in large-scale flooding on our study site in North Carolina, compared to only 1–4 inches observed from Hurricane Michael here in the Red Hills and Albany region. As such, when bobwhites are in the eye of the storm and when it comes to hurricane impacts timing and amount of rainfall is everything!