Thomas V. Dailey

Reproductive strategies, success, and mating systems of northern bobwhite in Missouri

To better understand the reproductive mechanisms that enable northern bobwhite (Colinus virginianus) to recover from high annual mortality, we studied the reproductive strategies, success, and mating systems of 321 radio-marked bobwhite in northern Missouri during 1990-92. Seventy-four female and 43 male bobwhite incubated 159 nests. Females exhibited apparent monogamy during 60% of nesting attempts and apparent polyandry during 40%. Over the entire nesting season, 71% of females were polyandrous. Of those birds alive 15 April (n = 112 F, n = 148 M), 40.2% of females and 13.5% of males successfully hatched ≥1 nest. Seventy-four percent of females (n = 42) and 26% of males (n = 50) surviving until 1 September successfully hatched ≥1 nest. Nesting females that survived the nesting period incubated a mean of 1.8 nests (SE = 0.13), and males incubated 1.0 nests (SE = 0.04). Of those birds that failed on an initial nesting attempt, 57.9% of females (n = 38) and 2 of 23 males incubated ≥1 renest. Of those females that were successful on their initial nesting attempt, 25.7% attempted second nests. Female first nests represented 45.9%, female renests 20.1%, female double-clutch attempts 5.7%, and male-incubated nests 28.3% of all nests located. Nest survival was 43.7% (SE = 3.9). The reproductive system of northern bobwhite enables recovery from low annual survival or periodic catastrophic declines and may be an adaptation to fluctuating resources in ephemeral, dynamic habitats.

Survival and cause-specific mortality of northern bobwhite in Missouri

Efforts to understand fluctuations in northern bobwhite (Colinus virginianus) abundance illustrate inadequate knowledge of demographic processes. Therefore, we estimated seasonal survival, annual survival, and cause-specific mortality of 1,001 radio-marked bobwhite in northern Missouri. Annual survival was 5.3 ± O.5% and did not differ between ages (P = 0.33) or sexes (P = 0.48). Fall-spring survival (15.9 ± 0.8%) was less than spring-fall survival (33.2 ± 2.7%, P < 0.001). Females had lower fall-spring survival (13.7 ± 1.1%) than males (17.6 ± 1.1%, P = 0.02). Male-biased sex ratios likely result from differential fall and winter survival. Avian (28.7%) and mammalian (25.7%) predators were primary natural mortality agents. Hunter-retrieved (22.9%) and -unretrieved (5.3%) kill resulted in 28.2% harvest-related mortality. During springfall, males experienced higher avian mortality (26.5%) than females (20.0%) (P = 0.09). Greater vulnerability of males to avian predators may represent a cost of displaying. Each incubation and brood-rearing attempt reduced survival by 16% when compared with nonreproductively active birds during a similar period. Bobwhites must be highly productive to replace annual population losses

Effect of Water Restriction on Feed Intake of White-Tailed Deer

We offered 9 male white-tailed deer (Odocoileus virginianus) feed and water ad libitum for 34 days, and measured intake of both daily. We provided separate groups (3 x 3 balanced, simple crossover design) 33, 67, and 100% of ad libitum water intake for 4 days. Mean dry-matter intake (DMI) (g/kg body wt [BW]VP.7) for 3-4 days prerestriction was compared to each of the 4 days on restriction. Dry matter intake decreased (P < 0.01) for deer receiving 33% of ad libitum water intake on days 3 and 4. One deer refused feed on day 4. There was a difference (P < 0.05) in mean DMI on day 3 between the group receiving 100% of ad libitum water and the group that received 33% of ad libitum water. Differences in DMI existed on day 4 among all 3 groups (P < 0.05). The group receiving 33% of ad libitum water lost more weight than the other groups (P < 0.05). Because of lower than expected BW losses by the water-restricted animals, it appears that white-tailed deer possess some degree of physiological adaptation to dehydration. High daily maximum temperatures (36 C) may have exacerbated the effect of water restriction on DMI. Because of high temperatures and frequent summer droughts in southern Texas, the need for adequate water for whitetailed deer may be critical. J. WILDL. MANAGE. 52(4):602-606 Knowledge of the role of water in deer physiology and ecology in hot, arid environments is limited. Experimental studies examining the role of water in deer physiology are limited, and most work has addressed ad libitum water intake or distribution and habitat preferences of deer in relation to water (Elder 1954, Welch 1960, Michael 1968, Longhurst et al. 1970, Hervert and Krausman 1986). The need for supplemental water may be especially important in southern Texas because prolonged periods of high temperature and drought are common (Norwine and Bingham 1986, Rappole et al. 1986). Understanding water needs of deer could help explain their productivity, forage selection, and activity patterns. Robbins (1983:24) noted that wildlife biologists have often used water development without adequate understanding of the importance of water to target species. We report the effect of water restriction on feed intake of white-tailed deer in a hot environment. We thank A. Aguilar, L. G. Arguelles, and D. A. Boyer for assistance with animal handling; R. L. Bingham and N. E. Koerth for assistance with statistical analyses; and J. H. Rappole and F. S. Guthery for review of this manuscript. This project was partially funded by National Institute of Health Grant 506-RR-08107.

Experimental comparisons of diet selection by mountain goats and mountain sheep in Colorado

Mountain goats (Oreamnos americanus) and mountain sheep (Ovis canadensis canadensis) graz- ing on the same alpine sites chose similar diets during summer but not during winter. Their diets were dominated by forbs in early summer; however, intake of graminoids increased with advancing season. Neutral detergent solubles and crude-protein levels of summer diets of both species declined, whereas unlignified cell wall concentrations increased as summer progressed. During winter, mountain sheep chose diets containing more graminoids, unlignified cell wall, and in vitro digestible dry matter, and less dicots, neutral detergent solubles, and lignin than those selected by mountain goats. Our findings of seasonal differences in diet overlap are consistent with contemporary competition theory. We conclude that mixtures of dicots and graminoids in winter habitats of sympatric mountain goats and mountain sheep can reduce the potential for food competition between these species. J. WILDL. MANAGE. 48(3):799-806 Adams et al. (1982) predicted that in- troduced mountain goats would become competitors with mountain sheep in Col- orado. Predicting the potential for food competition depends on knowledge of diet similarity for mountain goats and sheep that forage in the same habitat. Previous comparisons of mountain goats and mountain sheep focused on free-ranging animals where differences in diets were confounded by dissimilarity in forage availability within the habitats where each species fed (Geist 1971:272, Pallister 1974, Stewart 1975). Moreover, these studies were limited to botanical characteristics of diets; lack of information on dietary nutritional attributes renders this ap- proach inadequate for a thorough under- standing of trophic relationships between species (Janzen 1979, Hobbs et al. 1983).

Use of Total Body Electrical Conductivity to Predict Northern Bobwhite Lipid Mass

Several studies have developed models to predict lipid mass of live birds from a measure of total body electrical conductivity (TOBEC), yet few studies have assessed the validity of these models with independent data. We used independent datasets from Illinois (n = 38), Indiana (n = 94), and Missouri (n = 41) to develop and validate multivariable regression models (calibration equations) predicting lipid mass of live northern bobwhites (Colinus virginianus) from measurements of body mass and TOBEC. We assessed the validity of each model by determining the mean difference between predicted and observed lipid mass for bobwhites used in constructing the other 2 models (prediction error). First-order models (i.e., lacking interactions and quadratic terms) were selected as most useful for predicting lipid mass for all 3 datasets (R 2 = 0.71-0.92, Ps < 0.01). Mean predicted lipid mass was < 19.1% (2.32 g) of observed means. Large prediction errors associated with 1 dataset may have resulted from differences in methods. Models for the other 2 datasets (Indiana, Missouri) were relatively accurate: mean prediction errors were <3.4% of observed means. Removing TOBEC from Indiana and Missouri models changed their accuracy little; mean prediction errors for these cross-validated models were <2.3% of observed means. Consequently, the benefits of using models with TO-BEC cannot always be assured.