Waiting for the rain

The boom and bust nature of bobwhite populations is all too well known for many South Texans. Populations peak during years of abundant rainfall and bust during years of drought. Although this population phenomenon is common knowledge to many quail enthusiasts, quantitative data are lacking regarding the reproductive response of bobwhites to rainfall. Questions are often asked such as "Exactly how much is reproduction depressed during dry periods?' and "How quickly and to what degree do they respond to rainfall?'

Historically, rainfall peaks occur in South Texas during June and September, with the latter generally resulting from late-season tropical storms or hurricanes. Despite historical patterns, there are no normal rainfall patterns in South Texas. The 2005 nesting season proved to be one of these unusual years, at least for bobwhites.

The beginning of the nesting season (May?June) was extremely dry. This dry period subsequently was dotted by a significant rainfall event during mid-July when Hurricane Emily made landfall in northern Mexico. This storm generated rains throughout much of South Texas, with Brooks County (location of CKWRI's The South Texas Quail Research Project) receiving about 5?6 inches of rain. Using data from The South Texas Quail Research Project, we were able to document bobwhite reproduction before and after the rainfall event.

In our research, we have 50 or more radio-marked bobwhites under study at all times and we have been monitoring these bobwhites 2?3 times/week. This monitoring scheme provided the necessary data for the temporal comparison before (1 May?15 July) and after (16 July?15 September) the rain. Here's how bobwhites responded.

Nest production was slow in 2005, with our first nest not being located until May 20th, about 3 weeks later than usual. It is normal behavior for bobwhites to remain paired throughout the breeding season (March?September) with covey formation initiating thereafter. However, during the dry period of 2005, bobwhites that had been paired at the start of the breeding season began forming coveys (4?6 bobwhites/covey) during mid-June to mid-July. In fact, during this dry period, many hens (70%) never attempted to nest. However, when the rains of Hurricane Emily came, bobwhites began pairing again and resumed nesting shortly thereafter (approximately 2.5 weeks). Twelve hens that had not nested prior to the rain did so after the rainfall. This resumed nesting activity caused the nesting rate to increase from 0.3 nests/hen before the rain to 0.7 nests/hen after the rain.

There is no doubt that the mid-season rain of Hurricane Emily positively benefited bobwhite reproduction in South Texas. Unfortunately, dry conditions resumed in August and possibly limited the magnitude of response. Although nesting rates doubled following the rainfall event in mid-July, overall, 2005 nesting rates were still poor compared to the previous 2 years when good production occurred (2 nests/hen).

Mother Nature is beyond the control of biologists and managers. Besides providing the best habitat we can for quail year-round and managing harvest, all we can do is hope Mother Nature doesn't have bobwhites waiting for the rain for too long.