Bobwhite Nesting Ecology and Modern Agriculture: A Management Experiment

Northern bobwhite (Colinus virginianus) populations have declined on a continental scale. One factor implicated in the decline is habitat loss through agricultural modernization. To better understand the relationship between northern bobwhite and modern farming, and to examine farm habitat improvement methods, we monitored bobwhite (N = 218) from April to September 1993 and 1994 on two study areas, western (WSA) and eastern (ESA), each divided into one filter strip (FS) (treatment) and one non-filter strip (NFS) (reference) section on Alligator River National Wildlife Refuge's farming units in Dare County, North Carolina. Filter strips were 9.4 m wide planted and natural vegetation buffer zones surrounding drainage-ditches in crop fields. Using radio-telemetry, we followed bobwhite, identified nest incubations and hatchings, and monitored hatched broods. We examined the null hypotheses that number of captures, distances to first nest from capture site, number of nest incubation initiations, nest success, and adult and brood survival would be identical on FS and NFS sections. With equal effort, there were 142 and 65 bobwhite captured on the WSA FS and NFS sections, and 75 and 48 bobwhite captured on the ESA FS and NFS sections, respectively. Pooling data across areas, sections, and years, 42 quail initiated 53 clutches. There were 31 and 3 incubations initiated on the WSA FS and NFS sections, respectively. There were 13 and 6 incubations initiated on the ESA FS and NFS sections, respectively. Pooling across areas, sections, and years there was 1 incubation/3 and 1 incubation/8 transmittered bobwhite on FS and NFS sections, respectively. Pooling clutch (N = 28) data for all areas, sections, and years, clutches averaged 11.7 (SE = 0.75), and declined over time (P = 0.006). Nest success, pooled across years for section, was 32% (N = 44, 14 successful) and 44% (n = 9, 4 successful) for FS and NFS sections, respectively, and did not differ (P > 0.05). Pooling across sections by year, nesting success did not differ between years (P = 0.11), but differed between early (≤ 15 Jul) and late (> 15 Jul) periods (19.4% and 54.5%, respectively, P — 0.02). Quail on NFS areas exhibited greater movements from capture site to first nest. Pooling survival data across areas, sections, and years sub-adult/ adult survival from 1 April to 29 September was 33% (95% CI = 24% - 42%). Brood survival to 28 days (N = 5) ranged from 0%-100% and averaged 68% (SE = 17%). Higher nesting success and high brood survival in the later periods were correlated with maturation of broadcast-planted soybeans.

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