Marsha Sovada - Academia.edu (original) (raw)

Papers by Marsha Sovada

Abstract: Low recruitment rates prevail among ducks in the Prairie Pothole Region of North Americ... more Abstract: Low recruitment rates prevail among ducks in the Prairie Pothole Region of North America, primarily because of high nest depredation rates. The red fox (Vulpes vulpes) is a major predator of duck eggs, but fox abundance is depressed by coyotes (Canis latrans). We ...

Waterbirds, 2005

Chase Lake National Wildlife Refuge currently supports the largest breeding colony of the America... more Chase Lake National Wildlife Refuge currently supports the largest breeding colony of the American White Pelican ( Pelecanus erythrorhynchos ) in North America. The first written account of the colony's status was in 1905, when approximately 500 pelicans nested on two islands in Chase Lake. The colony grew to nearly 34,000 breeding birds by 2002. Surveys of breeding pelicans in the colony were sporadic from 1905 until 1972. Because the availability of foraging areas affects recruitment, pond counts from south-central North Dakota were used as an index of the relative availability of foraging areas. Pond counts varied widely in the 1970s and 1980s. In 1993, pond numbers increased dramatically, reached a peak in 1997, then declined but remained relatively high through 2002. Pelican numbers also increased in the mid-to late-1990s, possibly in response to increased and stable foraging opportunities. Because rising water in Chase Lake inundated the original nesting islands during that period, pelicans were forced to relocate nesting areas. Relocation provided more nesting space than the original islands, and nesting pelicans seemed to be gradually filling these areas. Threats to the Chase Lake breeding colony include disease, predation, and human disturbance. Research is needed to better understand the mechanisms that underlie the dynamics of AWPE metapopulations and their sub-units, including factors that influence nest-site selection, productivity, and survival of adults and young in large colonies.

The Journal of Wildlife Management, 1998

... 1994). Poisoning also has been reported to cause mortality in kit fox populations (Schito-ske... more ... 1994). Poisoning also has been reported to cause mortality in kit fox populations (Schito-skey 1975, Standley et al. 1992). ... Page 7. 1306 SWIFT Fox MORTALITY * Sovada et al. J. Wildl. ... MOHR, C. 0. 1947. Table of equivalent populations of North American small mammals. ...

The Journal of Wildlife Management, 1995

Journal of Mammalogy, 2007

We compared track-tube sampling with mark-recapture livetrapping and evaluated a track-tube index... more We compared track-tube sampling with mark-recapture livetrapping and evaluated a track-tube index, defined as the number of track tubes with identifiable small mammal tracks during a 4-night period, as a predictor of small mammal abundance estimates in North Dakota grasslands. Meadow voles (Microtus pennsylvanicus) were the most commonly recorded species by both methods, but were underrepresented in track-tube sampling, whereas 13-lined ground squirrels (Spermophilus tridecemlineatus) and Franklin's ground squirrels (S. franklinii) were overrepresented in track-tube sampling. Estimates of average species richness were lower from track tubes than from livetrapping. Regression models revealed that the track-tube index was at best a moderately good predictor of small mammal population estimates because both the form (linear versus curvilinear) and slope of the relationship varied between years. In addition, 95% prediction intervals indicated low precision when predicting population estimates from new track-tube index observations. Track tubes required less time and expense than mark-recapture and eliminated handling of small mammals. Using track tubes along with mark-recapture in a double sampling for regression framework would have potential value when attempting to estimate abundance of small mammals over large areas.

Journal of Mammalogy, 2004

Mammalian predation influences waterfowl breeding success in the U.S. northern Great Plains, yet ... more Mammalian predation influences waterfowl breeding success in the U.S. northern Great Plains, yet little is known about the influence of the landscape on the ability of predators to find waterfowl nests. We used radiotelemetry to record nightly movements of red foxes (Vulpes vulpes) and striped skunks (Mephitis mephitis) in two 41.4-km 2 study areas in North Dakota. Study areas contained either 15-20% grassland (low grassland composition) or 45-55% grassland (high grassland composition). Grasslands included planted cover, pastureland, and hayland. We predicted that the type and composition of cover types in the landscape would influence both predator movement across the landscape (as measured by the fractal dimension and displacement ratio) as well as localized movement (as measured by the rate of movement and turning angle between locations) within patches of different cover types. Red fox movements were straighter (lower fractal dimensions and higher displacements) across landscapes with a low grassland composition, indicating directed movement between the more isolated patches of planted cover. Striped skunk movements did not differ between landscape types, illustrating their movement along wetland edges, which had similar compositions in both landscape types. The high variability in turning angles by red fox in planted cover and pastureland in both landscape types is consistent with restricted-area foraging. The high rate of movement by red foxes in planted cover and by striped skunks in wetland edges suggests that spatial memory may influence movement patterns. Understanding the behavior of predators in fragmented prairie landscape is essential for managing breeding habitat for grassland birds and for predicting the spatial and temporal dynamics of predators and their prey.

Ecological Applications, 2005

Prairies and other North American grasslands, although highly fragmented, provide breeding habita... more Prairies and other North American grasslands, although highly fragmented, provide breeding habitat for a diverse array of species, including species of tremendous economic and ecological importance. Conservation and management of these species requires some understanding of how reproductive success is affected by edge effects, patch size, and characteristics of the landscape. We examined how differences in the percentage of grassland in the landscape influenced the relationships between the success of nests of upland-nesting ducks and (1) field size and (2) distance to nearest field and wetland edges. We collected data on study areas composed of 15-20% grassland and areas composed of 45-55% grassland in central North Dakota, USA during the 1996 and 1997 nesting seasons. Daily survival rates (DSRs) of duck nests were greater in study areas with 45-55% grassland than with 15-20% grassland. Within study areas, we detected a curvilinear relationship between DSR and field size: DSRs were highest in small and large fields and lowest in moderately sized fields. In study areas with 15-20% grassland, there was no relationship between probability of hatching and distance to nearest field edge, whereas in study areas with 45-55% grassland, there was a positive relationship between these two variables. Results of this study support the conclusion that both landscape composition and configuration affect reproductive success of ground-nesting birds. We are prompted to question conservation strategies that favor clustering moderately sized patches of nesting habitat within agricultural landscapes because our results show that such patches would have low nest success, most likely caused by predation. Understanding the pattern of nest success, and the predator-prey mechanisms that produce the pattern, will enable design of patch configurations that are most conducive to meeting conservation goals.

Biological Conservation, 2008

The American Midland Naturalist, 2001

... Prairie Nat. 23:131138. Jones, J. K, Jr, DM Armstrong, RS Hoffman, and C. Jones. 1983. Mamma... more ... Prairie Nat. 23:131138. Jones, J. K, Jr, DM Armstrong, RS Hoffman, and C. Jones. 1983. Mammals of the Northern Great Plains. Univ. ... (2007) Dietary Overlap of Swift Foxes and Coyotes in Northwestern Texas. ... SUSAN K. SKAGEN, AMY A. YACKEL ADAMS, ROD D. ADAMS. ...

The American Midland Naturalist, 1999

PLoS ONE, 2014

In the past decade, severe weather and West Nile virus were major causes of chick mortality at Am... more In the past decade, severe weather and West Nile virus were major causes of chick mortality at American white pelican (Pelecanus erythrorhynchos) colonies in the northern plains of North America. At one of these colonies, Chase Lake National Wildlife Refuge in North Dakota, spring arrival by pelicans has advanced approximately 16 days over a period of 44 years . We examined phenology patterns of pelicans and timing of inclement weather through the 44-year period, and evaluated the consequence of earlier breeding relative to weather-related chick mortality. We found severe weather patterns to be random through time, rather than concurrently shifting with the advanced arrival of pelicans. In recent years, if nest initiations had followed the phenology patterns of 1965 (i.e., nesting initiated 16 days later), fewer chicks likely would have died from weather-related causes. That is, there would be fewer chicks exposed to severe weather during a vulnerable transition period that occurs between the stage when chicks are being brooded by adults and the stage when chicks from multiple nests become part of a thermally protective crèche.