Population Irruptions of Northern Bobwhite: Testing an Age‐Specific Reproduction Hypothesis

Abstract

Age-specific reproduction has been suggested for northern bobwhite (Colinus virginianus) and has been hypothesized as a factor contributing to population irruptions. However, little research has been conducted on the subject. We conducted a laboratory and field study to determine if age-specific reproduction occurred in northern bobwhites. Our objectives were to compare 7 reproductive measures (% F nesting, date of first incubated nest, egg-laying rate, nesting rate, clutch size, egg mass, and egg hatchability) between first-and second-year breeders and determine if differential reproduction was impacted by diet quality. The laboratory study consisted of a 2 3 2 factorial experiment with age and diet quality (low protein [12%] and high protein [24%]) as the factors. Data for the field study represented a 6-year data set of bobwhite reproduction (May-Sep 2000-2005 obtained from an ongoing radiotelemetry study in southern Texas, USA. We documented similar productivity (i.e., % F laying, egg-laying rate, and egg mass) and timing of laying (i.e., date of first egg) between juvenile (n ¼ 33) and adult bobwhites (n ¼ 27) in our laboratory study. However, females on the high-protein diet exhibited a greater egg-laying rate than females on the low-protein diet. Under field conditions, we also documented no difference in productivity (% F nesting, nesting rate, clutch size, egg hatchability) and timing of nesting (date of first incubated nest) between age classes (n ¼ 59 juv and 32 ad). Our findings do not support early suppositions of age-specific reproduction in quail. Quail irruptions should not be influenced by population age structure as it relates to agespecific reproduction. (JOURNAL OF WILDLIFE MANAGEMENT 71(3): 895-901; 2007)

Reproduction and Microhabitat Selection in a Sharply Declining Northern Bobwhite Population

“…Apparent nest success overestimates nest survival (Mayfield 1961, Johnson 1979), but apparent nest success is less biased in Northern Bobwhite studies because most nests are found at a similar stage of incubation . Apparent nest success (47.6%, 10 of 21 nests successful) was within the range of published estimates (rangewide average 5 0.42, range 0.25-0.63; Sandercock et al 2008) and was similar to reported median values from Texas (49%; Hernandez et al 2007), Oklahoma (48%; Cox et al 2005), and Florida (45%; DeVos and Mueller 1993).…”

“…Study Site.-This study was conducted in a 125-km 2 area without fixed study area boundaries in west-central Cumberland County, New Jersey, USA (39u 229 N, 75u 159 W; hereafter the ''focal area'') during the Northern Bobwhite breeding season (1 May-30 Sep 2006-2007. Cumberland County is within the Outer Coastal Plain physiographic region, bordering Delaware Bay.…”

Assessment of northern bobwhite survival and fitness in the West Gulf Coastal Plain ecoregion

“…Estimates of nest success were comparable (in 2013) or higher (in 2014) to those reported in Texas (49%) [ 65 ], New Jersey (45.4%) [ 66 ]; Florida (41%) [ 67 ], and Kentucky (31.7%) [ 68 ]. Average clutch size on Felsenthal NWR was higher than the assumed range-wide average of 12 eggs [ 1 ]; and, with the exception of the hatchability rate in 2013; (77%), the pooled hatchability rate (86%) was in range compared to rates reported in the literature (80% - 96%) [ 20 ].…”

An electronic system to collect distance‐sampling data during helicopter surveys of northern bobwhite

“…Consequently, 95% confidence intervals tended to be wide for study sites with relatively low number of detections. Bobwhite populations on southwestern rangelands are strongly influenced by weather and density fluctuates drastically (Hernández et al 2005, 2007). Thus, survey effort required to reach a sufficient number of detections or a target level of precision may be considerable during population lows.…”