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Beginning with this issue, the Delta News will come to your email twice a year – in the winter and spring. Delta funds many bright students doing excellent research, but unless you were able to get to the Delta Research Symposium in July, you probably have not heard about any of their exciting results. So the winter issue will feature two or three short articles by Delta students reporting recent results of their research. This issue features articles by two Delta students doing great research. Mark Drever (Ph.D. Candidate, University of Guelph) writes about the results of his research on spatial synchrony of duck populations. Eric Lindstrom (M.S. Candidate, Southern Illinois University) writes about a technique to accurately determine breeding propensity in Mallards. Winter is not only a time to enjoy the results of the year, but it is time to start preparing for the next year of great projects and looking for ways to grow and strengthen the research heritage left by H. A. Hochbaum. We have received many new and exciting proposals for funding in 2005, which are currently being reviewed. The spring issue of the Delta News will highlight the newest research proposals we are funding. Elizabeth Loos SPATIAL SYNCHRONY OF PRAIRIE DUCKS
With this in mind, I examined the synchrony of 10 duck species counted in 23 aerial survey strata over the Prairie Pothole Region. As a measure of synchrony, I calculated cross-correlation coefficients, i,j, for each pairwise combination of survey strata based on population growth rates (ri,t) at each survey section. The mean cross-correlation coefficient was used as a measure of overall synchrony for each species, and its standard error (SEboot) was calculated using a bootstrap approach, where 95% confidence interval = observed mean cross-correlation coefficient 1.96 SEboot. As a follow-up test to look at how mean synchrony might vary with the ducks’ habitat preference, I compared the mean correlation coefficients with an index of habitat preference developed by Johnson and Grier (1988). This index provides a relative measure of wetland permanence used by duck species, with high values indicating use of shallow ephemeral wetlands and low values indicating use of deeper more permanent wetlands. Mean correlation coefficients varied from –0.0003 (redhead) to 0.310 (northern pintail) among the 10 duck species (Figure 1). Eight of the 10 species showed significant synchrony, and only Redhead and Canvasback, had mean correlation coefficients whose 95% confidence interval included zero. The two species that had the lowest mean correlation coefficients of the 10 species, canvasback and redhead, are regarded as strongly philopatric and may be less likely to disperse than other species. Dispersal between sites has the potential to synchronize population dynamics, and thus the lower proclivity of canvasback and redhead to disperse may explain their low overall mean synchrony relative to the other duck species. In addition, mean synchrony values were correlated with the Johnson and Grier (1988) index (Pearson’s r = 0.63, n = 10, P = 0.05), suggesting that species that use ephemeral more shallow wetlands tend to be more synchronized than species that use permanent deeper wetlands. If dispersal rates are tied to habitat conditions, then this pattern also supports the role of dispersal as synchronizing force in duck population dynamics.
Figure 1. Means and 95% confidence intervals for spatial synchrony for 10 breeding duck species and for pond counts in 23 survey strata of Prairie Pothole Region, 1975-1995. Synchrony was calculated as the mean cross-correlation coefficient between pairwise combinations of survey strata based on population growth rates (rt) at each survey stratum. Species are listed according to an index of habitat preference developed by Johnson and Grier (1988), with species listed first having a preference for shallow ephemeral wetlands and species listed last having a preference for deeper more permanent wetlands. WHAT PERCENTAGE OF MALLARDS BREED? Mallard breeding ecology has been extensively studied, but little is known about a female’s probability of breeding. Breeding probability (the proportion of sexually mature females within a population that lay ≥ 1 eggs during a given breeding season) is a vital component of waterfowl recruitment, and thus greatly affects population numbers. Factors such as food availability, habitat conditions, and social behavior play an important role in determining breeding probability. Despite its significance, mallard reproductive success has not been measured directly and estimates of breeding probability remain potentially biased. I am investigating a new method to estimate breeding probability in mallard populations.
The focus of my research was to develop a new technique that will allow biologists to estimate breeding probability in mallards by examining female ovaries following the breeding season. A mallard ovary resembles a cluster of grapes and is comprised of several individual follicles. When a hen lays an egg, one of these follicles ruptures leaving behind a temporary visible scar. The presence of these scars indicates egg-laying occurred during the most recent nesting season. Therefore, ovaries of non-breeding hens will not have ovulation scars. During 2002-2003, I conducted research at the Delta Waterfowl Research Station in Manitoba, Canada, and throughout California’s Central Valley using both captive and radio-marked, free-ranging mallard hens. I removed and examined ovaries from 48 females (with known laying histories) at 30-90 days following the completion of egg-laying. My results indicate that these scars remain identifiable up to 60 days post-laying in intact ovaries and up to 90 days in cross-sectioned ovaries viewed under a microscope. Using these techniques, researchers may be able to determine whether or not a hen laid eggs up to 2-3 months following the completion of egg-laying. In summary, breeding probability is difficult to accurately measure in mallard populations and its influence on population dynamics remains unclear. Results of this study (ovulation scars remain identifiable up to 3 months following egg laying) suggest that ovary examination may provide an alternative approach to estimate breeding probability in mallard populations. Previously, researchers have radio-marked a large number of pre-breeding females to evaluate reproductive performance in mallards, but these types of projects are often costly and logistically difficult. Radio-marking pre-breeding females may also adversely impact breeding behavior and current methods used to capture hens prior to radio-attachment likely exclude a large component of non-breeding individuals. Therefore, radio-telemetry studies may not be an optimal approach to estimate breeding probability in mallards or other waterfowl species. Instead, the future development and adoption of ovary examination may provide a new method to estimate this important vital rate. Applying this technique to unmarked females would remove confounding effects associated with “trapping bias” and potential physiological impacts caused by radio-transmitters. This study will enhance our understanding of mallard breeding populations and facilitate future management decisions. Finally, the development of this technique may lead to future studies addressing breeding probability estimates in other waterfowl species of concern, such as northern pintail and scaup.
Despite a rainy start, the Symposium (July 8 – 11) attracted over 75 attendees who listened to Delta students presenting their research findings and avidly discussed the future of waterfowl, waterfowl management and hunting. The Symposium was kicked off on Thursday evening by Jonathan Scarth, Delta’s Executive Vice President, who talked about the activities Delta is involved in today - from funding graduate student research to policy work for protecting and enhancing waterfowl habitat as well as actively supporting hunting. Friday and Saturday, graduate students presented the latest updates on their projects – topics ranged from Lesser Scaup in the boreal forest to vegetation in Mobile Bay, Alabama and the endangered Koloa duck in Hawaii. Guest speakers included Dr. Tom Nudds (University of Guelph) and Jeremy Kwolek (California Waterfowl Association). However, it wasn’t all hard work. Saturday, students had a chance to try their hand at clay shooting. Many students who had never even held a gun before were hooked on a new sport by the time it was over! Delta continually works to acknowledge excellence in our future resource managers and researchers. Saturday evening at our awards ceremony, Jean-Michel DeVink (University of Saskatchewan) was presented with the award for “Best Presentation by a PhD student”, sponsored by the California Waterfowl Foundation. Eric Lindstrom (Southern Illinois University) took home the award for “Best Presentation by a Master’s student”, sponsored by Dr. Rick Kaminski of Mississippi State University. Other award winners were: Peter Green Communications Award 1st: Karin Kettenring, University of Minnesota Delta extends a thank you to the following organizations and people whose support made the 2004 Delta Research Symposium possible: Acadiana (Lafayette, LA) Delta Chapter THANK YOU Thank you to Dr. Mike Webster from Washington State University and Dr. Bob Clark from the University of Saskatchewan for taking time out of their busy schedules to give presentations for Delta students working at Minnedosa, Manitoba. In 2002, Delta Waterfowl Foundation initiated a program to boost productivity of its students and help stimulate dissemination of scientific results to the scientific community. Delta Waterfowl firmly believes that scientific publications remain the best tool for communicating research findings to the rest of the scientific community. The 2003 Publication of the Year Award goes to Josh Ackerman for “Current versus future reproduction: an experimental test of parental investment decisions using nest desertion by mallards (Anas platyrhynchos)” (Behavioral Ecology and Sociobiology 54:264-273). Congratulations to Josh for capturing this top prize in Delta’s publication awards for the second consecutive year. Josh also was Delta’s most productive student in 2003, publishing 3 papers in top-tier journals (Journal of Wildlife Management, Animal Behavior, and BES). Josh did this work as part of his Ph.D. with John Eadie at the University of California, Davis. Josh is currently a Wildlife Biologist for USGS Western Ecological Research Center. Current research topics include density-dependent effects on mallard nest success and using radio-telemetry to assess exposure of waterbirds to contaminants in the San Francisco Bay. RECENT PUBLICATIONS BY DELTA STUDENTS AND STAFF (not reported in Spring 2004 newsletter) 2003 Dion, N., K.A. Hobson, and S. Lariviere. 2003. Does removal of duck nest predators affect the temporal patterns of predation for simulated nests of grassland songbirds? Canadian Field-Naturalist 117: 347-351. Koons, D.N. and J.J. Rotella. 2003. Have lesser scaup, Aythya affinis, reproductive rates declined in parkland Manitoba? Canadian Field-Naturalist 117:582-588. Larivière, S. 2003. Edge effects, predator movement, and the travel-lane paradox. Wildlife Society Bulletin 31: 315-320. Richman, S.E. and J.R. Lovvorn. 2003. Effects of clam species dominance on nutrient and energy acquisition by spectacled eiders in the Bering Sea. Marine Ecology Progress Series 261:283-297. Samelius, G., S. Larivière, and R.T. Alisauskas. 2003. Immobilization of arctic foxes with tiletamine hydrochloride and zolazepam hydrochloride (Zoletil®). Wildlife Society Bulletin 31: 192-196. 2004 Ackerman, J.T., A.L. Blackmer and J.M. Eadie. 2004. Is predation on waterfowl nests density dependent? – Tests at three spatial scales. Oikos 107:128-140. Anteau, M.J. and A.D. Afton. 2004. Nutrient reserves of lesser scaup (Aythya affinis) during spring migration in the Mississippi flyaway: a test of the spring condition hypothesis. Auk 121: 917-929. Hoover, A.K., F.C. Rohwer, and K.D. Richkus. 2004. Evaluation of nest temperatures to assess female nest attendance and use of video cameras to monitor incubating waterfowl. Wildlife Society Bulletin 32:581-587. Loos, E.R. and F.C. Rohwer. 2004. Laying-stage nest attendance and onset of incubation in prairie nesting ducks. Auk 121:587-599. Mehl, K.R., R.T. Alisauskas, K.A. Hobson, and D.K. Kellett. 2004. To winter east or west? Heterogeneity in winter philopatry in a central-arctic population of king eiders. Condor 106: 241-251. Pearse, A. 2004. Effects of predator removal on duck production. Wildlife Trends May/June 2004: 20-25. Pearse, A. and J.T. Ratti. 2004. Effects of predator removal on mallard duckling survival. Journal of Wildlife Management 68:342-350. Richman, S.E. and J.R. Lovvorn. 2004. Relative foraging value to lesser scaup ducks of native and exotic clams from San Francisco bay. Ecological Applications. 14:1217-1231. 2004 PRESENTATIONS AND POSTERS Delta would like to recognize current Delta students for communicating their study results to the research community through presentations and posters (chronological order). Oral Presentations Eric Lindstrom, M.S.Southern Illinois University. Dr. Mike Eichholz, advisor. “Developing a method to estimate breeding probability of mallards using postovulatory follicles." Co-authored with Mike Eichholz and John Eadie. 40th Annual meeting of the Illinois Chapter of The Wildlife Society (March 6, 2004). Ryan Harrigan, Ph.D. Boston University . Dr. Michael Sorenson, advisor. "Population Genetics, Phylogeography, and Systematics of Mallards (Anas platyrhynchos) and Amercian Black Ducks (Anas rubripes)." Co-authored with Michael Sorenson. Evolution Conference 2004 (June 26–30, 2004). Karin Kettenring, Ph.D. University of Minnesota. Dr. Susan M. Galatowitsch, advisor. "Seed germination and dormancy cycling in 10 Carex spp. - implications for prairie pothole wetland restoration." Co-authored with Susan M. Galatowitsch. Ecological Society of America Annual Meeting (August 1-9, 2004). Daniel W. Coulton, Ph.D. University of Saskatchewan. Drs. Bob Clark and Serge Larivière, advisors. “Sources of recruits to local parkland mallard populations: identifying natal origin using dD, d13C and d15N values in feathers.” Co-authored with Bob Clark, Serge Larivière and Keith Hobson. One Hundred and Twenty-second Stated Meeting of the American Ornithologists' Union in conjunction with the 2004 Annual Meeting of the Society of Canadian Ornithologists (August 16-21, 2004). Matt Kaminski, M.S. State University of New York-College of Environmental Science and Forestry (SUNY-ESF). Dr. Guy Baldassarre, advisor. "Mallard breeding ecology, waterbird use, and hydrophyte communities associated with managed wetlands in New York." Co-authored with Guy Baldassarre. Great Lakes Waterfowl Symposium (August 23-26, 2004). Eric Lindstrom, M.S. Southern Illinois University. Dr. Mike Eichholz, advisor. “Developing a method to estimate breeding probability of mallards.” Co-authored with Mike Eichholz and John Eadie. Great Lakes Waterfowl Symposium (August 23-26, 2004). Benjamin S. Rashford, Ph.D. Oregon State University. Dr. Richard M. Adams, advisor. "Conservation portfolios: Applying financial portfolio theory to wildlife conservation design." Co-authored with Richard M. Adams. The Wildlife Society's 11th Annual Conference (September 18 - 24, 2004). Poster Presentations Karin Kettenring, Ph.D. University of Minnesota. Dr. Susan M. Galatowitsch, advisor. "What drives recolonization patterns of Carex spp. in hydrologically restored prairie pothole wetlands - the role of seed arrival and seed germination." Co-authored with Susan M. Galatowitsch. Seed Ecology 2004 (April 29 - May 4, 2004). Jeffrey L. Peters, Ph.D. University of Maryland, Baltimore Co. Dr. Kevin Omland, advisor. “Star-like mtDNA phylogeny in Gadwall: Population expansion or selective sweep?” Co-authored with Elizabeth Humphries and Roland Cheung. One Hundred and Twenty-second Stated Meeting of the American Ornithologists' Union in conjunction with the 2004 Annual Meeting of the Society of Canadian Ornithologists (August 16-21, 2004). Delta will provide knowledge, future leaders, solutions and its passion for waterfowl to scientists, resource managers, waterfowlers, conservationists and the public to enhance waterfowl populations while securing the future of waterfowling. In order to achieve this, Delta:
Dr. Frank Rohwer, Scientific Director Delta Waterfowl is a product of its strong membership base. If you would like to help support our growing student program, please phone us toll-free at 1-877-667-5656 in Canada or at 1-888-987-3695 in the USA for details on our memberships which start as low as $25.00. If you are already a member, or would like to make a direct contribution to the student program, we invite you to make a donation to one of our many endowment funds that specifically target our research program. For details about this, please contact Jonathan Scarth, Executive Vice President, toll-free at 1-877-667-5656. |
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Contact Information | USA Toll Free 888-987-3695 | Canada Toll Free 877-667-5656 | Site Map | Privacy Policy © 2007 Delta Waterfowl Foundation - All Rights Reserved |
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Populations exhibit spatial synchrony to the degree that their numbers rise and fall in concert at several sites over their distribution. This topic has received much attention lately in the academic literature because it may provide some insights to the degree that population dynamics are driven by spatial processes. The topic of synchrony should also interest conservation biologists because theoretical studies have suggested that highly synchronized populations have lower viability than non-synchronized populations, likely due to the reduced probability of a ‘rescue effect’ where populations with low numbers can be subsidized by nearby populations with high numbers.
Scaup and northern pintail had the highest mean correlation coefficients of the 10 species considered. Numbers of both scaup and northern pintail are currently in decline, lending support to the contention that spatial synchrony is more intense during population declines. This synchronization of these species means that population dynamics will be driven by events that widespread over the prairies, implying that conservation efforts for highly vagile species like pintails may be best addressed at large spatial scales. 
Currently, researchers assume that 95 to 100 percent of prairie nesting mallards breed when spring habitat conditions on the breeding grounds are wet, yet little empirical evidence exists to support this claim. Instead, these estimates remain potentially biased high because they are derived from radio-marked, decoy-trapped hens that have already established breeding territories (i.e., pair water). Non-breeding hens are not likely to establish these breeding territories, and therefore, would be excluded from current breeding probability estimates.
Where can you find heated discussions about waterfowl, waterfowl management and duck hunting between top researchers, resource professionals and up and coming young people in North America? The easy answer is Delta’s annual Research Symposium. On July 8, students, professors, professionals, Delta staff and board members migrated from all across North America to the Delta Marsh, birthplace of the Delta Waterfowl Foundation for the 2004 Research Symposium.