Robert J. Gates

Seasonal Movements of Sage Grouse in Southeastern Idaho

We studied seasonal movements of sage grouse (Centrocercus urophasianus) on, and adjacent to, the Idaho National Engineering Laboratory (INEL) in southeastern Idaho from summer 1977 through fall 1983. The study area included a mountain valley and sagebrush (Artemisia spp.) lowlands. Sage grouse used contiguous areas for wintering and breeding but moved as far as 82 km from winter and breeding areas to summer range. Juvenile sage grouse (n = 32) moved a mean distance of 14.9 km from summer to winter ranges and adult grouse (n = 33) moved a mean distance of 11.3 km. Male sage grouse from the mountainvalley population moved farther to summer range than did mountain-valley females and both sexes from lowland populations (P < 0.05). Movements by male and female sage grouse during fall were generally slow and meandering. Movements by females during spring were also slow and meandering compared to the relatively rapid and direct movements by males. Distances moved were not entirely influenced by the proximity of seasonal habitats, suggesting that seasonal movements tend to be traditional. Sage grouse populations should be defined on a temporal and geographic basis. Protection of sagebrush habitats within a 3.2 km radius of leks may not be sufficient to ensure the protection of year-long habitat requirements. J. WILDL. MANAGE. 52(1):116-122 Sage grouse occupy seasonal habitats, using mesic areas during summer (Klebenow 1969, Wallestad 1971) and sagebrush habitats during winter (Eng and Schladweiler 1972, Beck 1977, Remington and Braun 1985). Grouse occupying sagebrush habitats at relatively low elevation are sometimes nonmigratory (Wallestad 1975), and sage grouse inhabiting mountain valleys or areas with distinct elevational gradients are often migratory (Dalke et al. 1960, Connelly 1982). However, information on the timing and distance of seasonal movements and the spatial relationships of seasonal ranges to migration routes and breeding complexes is often lacking. Only Dalke et al. (1963) and Berry and Eng (1985) attempted to delineate these relationships. This information is necessary for defining sage grouse populations, identifying population habitats, and evaluating impacts of land use changes on this species; thus, allowing meaningful management practices to be implemented. The INEL and adjacent lands in southeastern Idaho contain mountain-valley and sagebrushlowland areas that differ in topography and precipitation (Connelly 1982, Gates 1983). Recognizing these differences, we hypothesized that seasonal movements of sage grouse occupying these areas might differ. Thus, we compared seasonal ranges and movement patterns of sage grouse using separate breeding ranges in mountain-valley and lowland areas. Our objectives were to (1) describe sage grouse seasonal movements; (2) define sage grouse seasonal ranges with respect to each other and to breeding complexes, and migration routes in both mountainvalley and lowland areas; and (3) suggest an approach to defining migratory sage grouse populations. This study was supported by the Office of Health and Environmental Research, U.S. Department of Energy. Technical assistance was supplied by the Idaho Department of Fish and Game, the U.S. Fish and Wildlife Service, and the Bureau of Land Management. We thank all of the individuals from the above agencies who contributed to this effort. We are especially grateful to O. D. Markham and W. J. Arthur for administrative guidance, advice, and field assistance. Field assistance was also provided by D. K. Halford and J. C. Hoag during various portions of this study. Earlier drafts of this manuscript were reviewed by R. E. Autenrieth, I. J. Ball, W. B. Sidle, L. D. Flake, and R. L. Present address: Idaho Department of Fish and Game, 5205 South 5th Avenue, Pocatello, ID 83204. 2 Present address: Cooperative Wildlife Research Laboratory, Southern Illinois University, Carbondale, IL 62901.

Energetic Carrying Capacity of Actively and Passively Managed Wetlands for Migrating Ducks in Ohio

Abstract Habitat conservation strategies of the North American Waterfowl Management Plan (NAWMP) are guided by current understanding of factors that limit growth of waterfowl populations. The 1998 implementation plan of the Upper Mississippi River and Great Lakes Region Joint Venture (UMR and GLRJV) assumed that availability of foraging resources during autumn in wetlands actively managed for waterfowl was the primary limiting factor for duck populations during the nonbreeding season. We used multistage sampling during autumn and spring 2001–2004 to estimate energetic carrying capacity (ECC) of actively and passively managed wetlands in Ohio, USA, and examine this assumption. Energetic carrying capacity during autumn was similar between actively and passively managed wetlands each year. Averaged across years, energetic carrying capacity was 3,446 and 2,047 duck energy-days (DED)/ha for actively and passively managed wetlands, respectively. These estimates exceeded the UMR and GLRJV assumption that 1,236 DED/ha were provided by managed wetland habitats. Energetic carrying capacity declined each year by >80% between autumn and spring migration. Consequently, ECC of actively and passively managed wetlands was low during spring (𝑥̄ = 66–242 DED/ha). These results suggested that duck foraging resources in actively and passively managed wetland habitats are abundant during autumn, but overwinter declines may create food-limiting environments during spring.

Intraspecific nest parasitism of wood ducks in natural cavities : Comparisons with nest boxes

Abstract Wood duck (Aix sponsa) hens are known to lay eggs in nests of other wood ducks. Low levels of intraspecific nest parasitism can increase the number of ducklings produced, but at high levels, increased numbers of eggs are offset by reduced hatching success and elevated nest abandonment. Such effects have been observed in nest boxes, stimulating interest in the role of intraspecific nest parasitism in natural cavities. We found high rates of nest parasitism (85% of nests) in natural cavities by applying microsatellite genetic markers to examine maternity for clutches laid in floodplain and upland forests. Clutch sizes, number of parasites per nest, and the number of parasitic eggs deposited per nest were greater in tree cavities located in floodplain than in upland forests (35.2%, 63.6%, 75.0% greater, respectively; P < 0.05), although the proportions of nests parasitized were similar (100% of floodplain nests versus 80% of upland nests, P = 0.11). We compared our data to almost 40 years of published data from studies of wood ducks using artificial nest boxes. Clutch sizes in natural cavities were smaller than reported for 3 populations using nest boxes (10.3%, 29.4%, and 49.2% smaller; P < 0.05), except when only floodplain nests were considered (5.0% larger, 11.6% and 28.8% smaller, P > 0.05). Fewer parasites (1.5 ± 0.1 parasites) contributed to nests in tree cavities than in 1 box-nesting population (2.7 ± 0.04, P < 0.05). We suggest that the high parasitism rates observed in natural cavities reflect the accuracy of microsatellite techniques relative to other methods and that conspecific nest parasitism is pervasive among wood ducks, even in natural tree cavities that are more widely dispersed and well hidden than nest boxes. However, despite the large proportion of cavity nests parasitized during this study, parasitism did not severely depress breeding productivity, as observed in some box-nesting populations. Long-term and experimental research on factors contributing to extremely large clutches in nest boxes could improve the efficacy of nest-box programs.

Breeding Biology of Wood Ducks Using Natural Cavities in Southern Illinois

Information on breeding biology of wood ducks (Aix sponsa) acquired largely through studies of artificial nest boxes may not represent natural cavities where most wood ducks are produced. We studied nesting biology of wood ducks using natural cavities in southern Illinois during springs 1993-95. Forty-four radiomarked females were tracked to nest sites, but these represented only 56% of resident females alive during the breeding season. Most (82%) nests were in upland forest beyond the Mississippi River floodplain where birds were captured. Six of 23 (26%) nests were parasitized, which is a rate higher than previously reported for natural cavities (12%), but is less than in nest boxes (40%). Nest success (64%) was higher than reported elsewhere in natural cavities (40%), but below that in nest boxes (66-75%). Success rates did not differ between floodplain (80%) and upland (59%) nests (P = 0.205). Duckling survival to fledging was high (42%), despite lengthy (x = 1.4-3.2 km) movements over mostly upland terrain. In our study, 2.9 ducklings fledged per nest attempt, compared to 3.8 ducklings per nest attempt from boxes in Tennessee. Low nesting effort and high rates of nest parasitism could have resulted from suboptimal habitat conditions in 1994 and 1995. In 1994, dry conditions during prenesting, followed by sudden flooding during egg laying and early incubation, were associated with a shorter nesting season (91 vs. 132 days), smaller proportions of nesting birds (42 vs. 57%), more nest parasitism (43 vs. 18%), and lower survival (55 vs. 81%) compared to 1995, when conditions were dry, but water levels were stable. Upland forests may be important sources of wood duck production in other areas where extensive loss and fragmentation of floodplain forest have occurred.

Partial Clutch Predation, Dilution of Predation Risk, and the Evolution of Intraspecific Nest Parasitism

Abstract Distributing eggs among multiple nests may have a selective advantage over laying eggs in one nest when stochastic events, such as predation, affect individuals of the same phenotype differently. However, an earlier analysis revealed that the mean fitness of such an egg-spreading strategy is equal to putting all eggs in one nest when predation destroys entire clutches. However, if predation typically results in partial clutch loss, distributing eggs among multiple nests may provide a selective advantage. We investigated the possibility that partial clutch loss could favor egg-spreading strategies by modeling mean fitness under a variety of egg-distribution strategies with partial nest predation. We found that higher fitness resulted from distributing eggs among multiple nests that contained at least as many eggs as a single nest containing the eggs of one female. The highest fitness resulted when eggs were in large clutches, because of predator-dilution effects. The fitness differences among egg-distribution strategies increased as predation rates, frequency of partial clutch loss, and the number of eggs destroyed in each partial predation event increased. We also examined the invasibility of pure and mixed parasitic and nesting strategies. Nest parasites may increase their fitness by spreading eggs among multiple nests that contain more eggs than would be present if they were nesting alone, but only a pure parasitic strategy can invade a population of nonparasites when the number of eggs laid is constrained.

REDUCED NEST PREDATION OF CAVITY-NESTING WOOD DUCKS DURING FLOODING IN A BOTTOMLAND HARDWOOD FOREST

Abstract ABSTRACT The importance of flooding to birds that nest in bottomland hardwood forests is poorly understood, in part because floods are difficult to predict. A large flood occurred in 2002, during our study of cavity-nesting Wood Ducks (Aix sponsa) in the Mississippi River floodplain. Nests were depredated prior to and after, but not during, the four-week flood. This observation prompted a retrospective analysis of flooding, nest predation, and nest success for our three-year study period of 2000–2002 and with a dataset extending back to 1995. Nest predation was lower and nest success was higher in the floodplain during floods. Flood conditions did not significantly affect nest success or nest predation rates in the adjacent upland, but nest success in upland forest was higher than in the floodplain during dry periods. Historically, spring flooding of riparian areas may to some extent have mitigated nest predation in bottomland forests.

Projected Availability of Natural Cavities for Wood Ducks in Southern Illinois

Abstract Wood ducks (Aix sponsa) and other species use tree cavities in forested wetlands and adjacent upland forests for nest sites and cover. The availability of tree cavities suitable for nesting is important to the population dynamics of hole-nesting species, but there is little quantitative information on how forest succession and maturation affect densities of suitable nest sites in eastern deciduous forests. Several studies have measured availability of tree cavities for nesting wood ducks, but data on cavity formation and persistence rates are needed to model changes in cavity abundance. We measured abundance and persistence of tree cavities suitable for nesting wood ducks in southern Illinois, USA, during 1993–2002. We simulated changes in abundance of nest cavities in the Mississippi River floodplain and adjacent upland forests using estimates of tree cavity densities by tree-diameter size classes and 10-year cavity persistence rates by tree species. Cavities were disproportionately common in the largest size classes, but tree species varied in their propensity to form cavities. Beech (Fagus grandifolia; 0.41 cavities/tree) and sycamore (Plantanus occidentalis; 0.50 cavities/tree) were prolific cavity producers, whereas a small proportion (0.05 cavities/tree) of cottonwoods (Populus deltoides) contained cavities. Kaplan–Meier estimates of annual and 10-year cavity persistence averaged 0.95 and 0.64, respectively. Cavity persistence also differed among species (P = 0.02): cottonwoods had the lowest (0.54) and sycamores had the highest (0.89) 10-year tree cavity persistence rates. Tree fall (50.0%), cavity floor deterioration (37.5%), and narrowing of the cavity entrance (12.5%) were the most prevalent causes of tree cavity loss. Forest stand projections indicated that cavity abundance will increase up to 34% over recent levels during the first 10 years and by 44% after 50 years. Most of this increase will be contributed by tree species that are not commonly used by wood ducks, but cavities will increase in oaks (Quercus spp.) and beeches as the forest matures into cavity-bearing size classes. Sycamores will steadily contribute cavities, but cottonwood is predicted to provide fewer cavities due to low survival of cavity-bearing size classes. Our results suggest that availability of nest and den sites for cavity-dependent wildlife will increase as eastern deciduous forests mature over the next half century. Cost-effectiveness of artificial nest box programs should be reevaluated in light of projected changes in tree cavity availability as deciduous forests mature in the eastern United States.

Habitat influences Northern Bobwhite survival at fine spatiotemporal scales

ABSTRACT Habitat quality influences individual survival at widely varying spatial and temporal scales. Understanding interactions between habitat and survival among individuals in declining populations that occupy highly modified landscapes can inform conservation strategies aimed at improving survival and population growth. We used radiotelemetry to monitor space use and daily survival of wintering Northern Bobwhites (Colinus virginianus) at the northern end of their range to test for fine spatial- and temporal-scale relationships between individual survival and habitat composition around radio-locations in agricultural landscapes in Ohio, USA. Habitat composition within daily and seasonal movement ranges of individuals (n = 189) during periods without snow cover did not explain variation in daily survival rates. However, mortality increased substantially in the presence of snow cover, and availability of woody cover and row crops within 95 m of an individual radio-location were positively associated with daily survival during those periods. A similar relationship between row crop availability and survival was supported at a larger scale that reflected composition of seasonal ranges (300-m buffer) but was less influential than fine-scale influences of woody cover and row crops. Our results suggest that previously documented selection for woody cover in our agricultural study areas was an adaptive behavior to improve individual survival during periods of snow cover. Positive associations between survival and row crop cover at daily and seasonal range scales suggest that agricultural landscapes confer improved survival probabilities when underlying constraints on occupancy related to woody cover are met. Collectively, our results suggest that targeted conservation practices focused on provision of suitable woody cover in agricultural landscapes in the northern end of the Northern Bobwhites range has potential to improve winter survival and perhaps abate long-term population declines in the region.

Explaining Hunting Participation in Ohio: A Story of Changing Land Use and New Technology

Long-term per-capita participation in hunting is declining in the United States, although trends vary by region and type of hunting activity. Numerous studies have identified diverse factors affecting individuals’ likelihood of participating in hunting, but relatively few have examined factors influencing involvement at a broader scale. Landscape and cultural changes associated with urbanization coupled with the distractions of entertainment technologies have been implicated as factors negatively influencing hunting participation at the broad, sociocultural scale. By examining factors related to Ohio hunting license and deer permit sales at the county-level (2007), we found that access to huntable lands, agriculture–forest matrix characteristics, proliferation of entertainment technologies, rurality, and racial/ethnic demographics were associated with participation rates. Although exurbanization drives parcelization and land use change, some regions are not yet saturated with technological infrastructure (e.g., southeastern Ohio) or have unique population demographics (e.g., Amish) that are likely to deter future declines in hunting participation.

Evaluation of Three Methods to Estimate Density and Detectability from Roadside Point Counts

ABSTRACT Roadside point counts are often used to estimate trends of bird populations. The use of aural counts of birds without adjustment for detection probability, however, can lead to incorrect population trend estimates. We compared precision of estimates of density and detectability of whistling northern bobwhites (Colinus virginianus) using distance sampling, independent double-observer, and removal methods from roadside surveys. Two observers independently recorded each whistling bird heard, distance from the observer, and time of first detection at 362 call-count stops in Ohio. We examined models that included covariates for year and observer effects for each method and distance from observer effects for the double-observer and removal methods using Akaikes Information Criterion (AIC). The best model of detectability from distance sampling included observer and year effects. The best models from the removal and double-observer techniques included observer and distance effects. All 3 methods provided precise estimates of detection probability (CV = 2.4–4.4%) with a range of detectability of 0.44–0.95 for a 6-min survey. Density estimates from double-observer surveys had the lowest coefficient of variation (2005 = 3.2%, 2006 = 1.7%), but the removal method also provided precise estimates of density (2005 CV = 3.4%, 2006 CV = 4.8%), and density estimates from distance sampling were less precise (2005 CV = 9.6%, 2006 CV = 7.9%). Assumptions of distance sampling were violated in our study because probability of detecting bobwhites near the observer was <1 or the roadside survey points were not randomly distributed with respect to the birds. Distances also were not consistently recorded by individual members of observer pairs. Although double-observer surveys provided more precise estimates, we recommend using the removal method to estimate detectability and abundance of bobwhites. The removal method provided precise estimates of density and detection probability and requires half the personnel time as double-observer surveys. Furthermore, the likelihood of meeting model assumptions is higher for the removal survey than with independent double-observers.