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RESEARCH ARTICLE
Contents Vol 37(5)

Impact of harvest on survival of a heavily hunted game bird population

Virginie Rolland A D , Jeffrey A. Hostetler A , Tommy C. Hines B , H. Franklin Percival C and Madan K. Oli A
+ Author Affiliations
- Author Affiliations

A Department of Wildlife and Ecology Conservation, 110 Newins-Ziegler Hall, University of Florida, Gainesville, FL 32611, USA.

B Small Game Program, Florida Fish and Wildlife Conservation Commission (retired), 1314 SW 186th St., Newberry, FL 32669, USA.

C US Geological Survey, Florida Cooperative Fish and Wildlife Research Unit, Department of Wildlife and Ecology Conservation, University of Florida, Bldg 810, Gainesville, FL 32611, USA.

D Corresponding author. Email: vrolland@ufl.edu

Wildlife Research 37(5) 392-400 https://doi.org/10.1071/WR09177
Submitted: 22 December 2009  Accepted: 20 July 2010   Published: 11 August 2010

Abstract

Context. Despite their economic importance and intensive management, many game bird species, including the northern bobwhite Colinus virginianus, are in decline. Declines may be explained, at least in part, by low survival due perhaps to poor habitat quality, high predation or excessive hunting pressure.

Aims. This study sought to estimate and model annual/seasonal survival probabilities, to evaluate factors influencing them and to determine the cause-specific mortality rates for northern bobwhites subject to varying levels of harvest on the Babcock–Webb Wildlife Management Area (BW area), south Florida, USA.

Methods. We applied Cox’s proportional hazard models to data collected from 2066 radio-tagged bobwhites during 2002–2008 to test for intrinsic and extrinsic factors affecting survival and the non-parametric cumulative incidence function estimator to estimate cause-specific mortality rates.

Key results. Mean annual survival (0.091 ± 0.006) in the BW area was lower than most estimates reported for other bobwhite populations. Annual survival differed between adults (0.111 ± 0.008) and juveniles (0.052 ± 0.008), and varied among years. Survival in winter (October–March; 0.295 ± 0.014) was similar to that in summer (April–September; 0.307 ± 0.013). Density of food strips (i.e. long and narrow food plots) did not influence survival, but hunting effort (number of hunters per day per km2) had a substantial negative impact on survival. In the lightly hunted field trial zone, winter (October–March) survival was significantly higher (0.414 ± 0.035) than in the other more heavily hunted management zones (0.319 ± 0.016). Cause-specific mortality analyses revealed that bobwhite mortality during summer (April–September) was mainly due to raptor (39.7%) and mammalian predation (35.6%), whereas hunting was the primary cause of mortality during winter (47.1%).

Conclusions. Our results highlight the potential role of harvest as an important cause of the northern bobwhite population declines in south Florida. High mortality during winter may reduce recruitment of juveniles to the reproductive segment of the population, and ultimately the population growth.

Implications. Our results suggest that reduction in hunting pressure may be necessary to reverse the declining population trends in heavily hunted game species in public lands, such as the northern bobwhites in the BW area.


Acknowledgements

We thank R. Dimmick for leading field data collection efforts, and S. & A. Brinkley, G. Coker, D. Caudill, D. Holt, J. McGrady, J. Sloane, and J. Scott for their significant contribution to data collection. We are grateful to the many volunteers from the south-west Florida Chapter of Quail Unlimited who aided the research in many ways. We also acknowledge A. Singh for preliminary data analysis, K. Pollock and R. Dorazio for statistical advice, C. McKelvy and T. O’Meara for valuable advice throughout the study, and B. Sandercock, N. Hyslop, F. Johnson, and an anonymous reviewer for helpful comments on earlier drafts. Research was funded by the Florida Fish and Wildlife Conservation Commission, and the Department of Wildlife Ecology and Conservation, University of Florida.


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