Factors influencing Northern Bobwhite recruitment, with implications for population growth

McConnell, Mark D.; Monroe, Adrian P.; Chandler, Richard B.; Palmer, William E.; Wellendorf, Shane D.; Burger, L. Wes; Martin, James A.

doi:10.1642/auk-18-49.1

Cited by 19 publications

(38 citation statements)

References 35 publications

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“…We observed lower survival for 30‐day (71%) and 90‐day (36%) post‐hatch periods compared to those reported in other studies (Puckett et al , Mueller et al , Suchy and Munkel ) but slightly higher than what was proposed as a minimum monthly period survival (67%) required for population stability (Sandercock et al ). Bobwhite abundance on our study area was stable during this study but exhibited significant annual swings in autumn density (McConnell et al ), supporting the minimum chick survival rate posited for population stability by Sandercock et al (). Despite intensive habitat management efforts on our study site, annual variation in chick survival was substantial, ranging from 14.6% to 76.9% for 90‐day survival periods.…”

Section: Discussionsupporting

confidence: 85%

“…In our study, when chick survival rates were higher and lower than average (±95% CIs), such as in 2002 and 2007 (Fig. ), subsequent autumn abundance increased and decreased, respectively (McConnell et al ). As such, annual fluctuation in chick survival may be a more salient determinant of population growth than expected (Sandercock et al ).…”

Section: Discussionmentioning

confidence: 45%

“…Data in these cases rarely exist for recently hatched individuals because of the difficulty of tracking altricial young from the fledgling stage or the difficulty of capturing young for precocial birds, compounded by logistical constraints such as small body size, rapid growth, and limited marking techniques. As a result, population models often rely on quantification of annual population growth rates from limited data, data‐imputation of estimates derived from individuals of different life stages, or simulation, which may lead to inaccurate estimates of population growth and spurious inference (Streby and Andersen , McConnell et al ). Therefore, empirically derived estimates of chick survival are important for validating population models, informing management actions, and facilitating conservation decisions.…”

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confidence: 99%

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Northern Bobwhite Chick Survival and Effects of Weather

2019

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Reliable vital rates for all life stages are necessary to identify limiting factors in wildlife populations and inform sound wildlife management. The difficulty associated with capturing and tagging precocial young, such as northern bobwhite chicks (Colinus virginianus), and linking variation in recruitment to ecological conditions has contributed to significant knowledge gaps in their population ecology. During 1999-2017, we captured and patagial-tagged ≤12-day-old bobwhite chicks (n = 3,576) and estimated their survival from time of capture (Jun-Sep) to fall and winter (Nov and Jan) recapture and winter (Feb) recovery. We used Burnham's model implemented in Program MARK to integrate mark-recapture and dead-recovery (via harvest) data to estimate survival for the 19-year study. By including weather covariates, we also evaluated explicit hypotheses related to temperature and precipitation effects on chick survival. We found inter-annual, intra-annual, and intra-seasonal variation in chick survival with an average annual daily survival estimate of 0.9887 (95% CI = 0.9321, 0.9918). Precipitation amount and number of precipitation (>0.635 cm) events during the first 4 weeks post-tagging decreased the daily survival rate of chicks curvilinearly. Average minimum daily temperature and maximum daily temperature effects on survival were negligible, but an interaction between minimum temperature and cumulative precipitation during the first 14 days post-tagging affected survival. We recommend population modelers incorporate intra-and inter-annual variation in chick survival to improve predictions. Observed variation in chick survival rates portends a significant opportunity to improve population management for bobwhites and other game birds.

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Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 45%

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Northern Bobwhite Chick Survival and Effects of Weather

2019

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“…Sandercock et al () used population modeling to impute that adult survival was the primary factor affecting population trends rather than variation in productivity in mostly declining populations. McConnell et al (), however, indicated that recruitment was more important than survival in a stable population. Thus, managers often reduce meso‐mammals in an attempt to increase reproductive success of bobwhites for purported increases in autumn recruitment and abundance (Stoddard , Côté and Sutherland , Newton ).…”

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Reduction in meso‐mammal nest predators improves northern bobwhite demographics

et al. 2019

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Nest predation is the major cause of nest failure in northern bobwhites (Colinus virginianus; i.e., bobwhites). Control of mid‐sized mammalian nest predators (i.e., meso‐mammals) is often conducted to increase reproductive success on lands managed for bobwhites. Nest predation by meso‐mammals, however, is only one part of a complex predator‐prey trophic system. There is limited understanding of the effect of nest predators on bobwhite demographics, which creates uncertainty about the efficacy of nest predator control. We quantified demographic effects on bobwhite populations from reducing meso‐mammals on 4 study areas managed for bobwhites in northern Florida and southwestern Georgia, USA, during 2000–2006. After 1 year of pre‐treatment monitoring (2000), we reduced meso‐mammal nest predator abundance through trapping over 3‐year intervals, March to September, on 2 sites using a crossover design. Efficacy of trapping was demonstrated by a 43% reduction in scent station visitation rates of meso‐mammals. Meso‐mammal control increased all demographic metrics including a 30% increase in nesting propensity, a 10% increase in nest success, and a 43% increase in chicks produced. Despite significant regional variation in breeding season survival rates, this equated to an average 18% increase in autumn density on trapped sites. Decision‐makers should weigh the tradeoffs between bobwhite population goals and costs of meso‐mammal control, where those that value maximum bobwhite density and reduced annual variation should likely implement control of meso‐mammals. © 2019 The Wildlife Society.

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“…Our models were most realistic when density dependence was relatively strong. This is expected for a species with a life history such as that of the bobwhite (Fowler 1981, Guthery 2002 and density dependence has been estimated empirically (McConnell et al 2018, Yeiser et al 2018. For simplicity, we chose a linear form across all vital rates.…”

Section: Discussionmentioning

confidence: 99%

Predation Management and Spatial Structure Moderate Extirpation Risk and Harvest of Northern Bobwhite

et al. 2020

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Density dependence, immigration, and emigration can considerably influence wildlife population demographics. Population models used to evaluate common actions like predator management and harvest in the absence of these processes may lead to poor management decisions. We built a novel population simulation model for the northern bobwhite (Colinus virginianus; bobwhite) that included implicit spatial structure (ingress and egress of individuals), density dependence, and harvest. We used 42 years of data (1970-2012) from a relatively stable population to create and validate the simulation model. We then used this simulation model to predict the effect of meso-mammal trap and removal, a management action that increases bobwhite fecundity, on population abundance, cumulative harvest through 50 years, and extirpation risk. We conducted a population sensitivity analysis to understand the implications of meso-mammal trap and removal to populations with varying vital rates. Incorporating ingress and egress of individuals and density dependence improved the understanding of bobwhite population dynamics and reduced the uncertainty about the efficacy of predator management across a range of environmental conditions. Increased number of immigration sources decreased extirpation risk and increased bobwhite abundance. A key outcome of our modeling process was that density-dependent processes did not fully compensate for harvest. Cumulative harvest through 50 years increased with increasing harvest rate but started to decline when harvest rate was >0.35 for populations with meso-mammal removal and 0.25-0.30 for populations without meso-mammal removal. Meso-mammal removal increased the harvest capacity of populations and produced greater harvest opportunity over time. Meso-mammal removal also buffered populations from extirpation risk resulting from too few immigration sources. Practitioners often ignore the contribution of immigration and emigration to local demographics or assume density-independent vital rates; however, recent literature reviews and our study indicate that these processes are important to the understanding of animal ecology and management. In the interest of the conservation of species that are hunted and at risk of extirpation in some geographies, predator management may increase hunter success and be a tool to reduce extirpation risk, although the degree of effectiveness likely varies geographically. This manuscript could serve as a framework for predicting the effects of management on bobwhite at the population level.

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Factors influencing Northern Bobwhite recruitment, with implications for population growth

Cited by 19 publications

References 35 publications

Northern Bobwhite Chick Survival and Effects of Weather

Northern Bobwhite Chick Survival and Effects of Weather

Reduction in meso‐mammal nest predators improves northern bobwhite demographics

Predation Management and Spatial Structure Moderate Extirpation Risk and Harvest of Northern Bobwhite

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