Modeling Avian Nest Survival in Program MARK

Understanding the factors infl uencing nesting success is a primary goal of many studies. To do this effectively, more advanced tools than Mayfi eld’s ad hoc estimator are needed. The recent development of a nest-survival model in program MARK provides a powerful and fl exible tool for the study of avian nest survival that can incorporate seasonal variation in survival and nest-specifi c covariates. We briefl y review the model and its development, illustrate how to include the effects of daily nest age and observer visits to nests, and conclude with an example analysis of Red-winged Blackbird (Agelaius phoeniceus) nest survival in Iowa. In this example, we found evidence for stagespecifi c differences in nest survival, seasonal patterns in nest survival that were best explained by a quadratic-time trend, and that survival differed between years. An exploration of several nestspecifi c covariates revealed that blackbird nest survival was positively affected by nest height, weakly affected by nest placement (nests placed in living vegetation may have experienced slightly higher survival), and unaffected by clutch size and within- and between-cell nest placement

Wildlife-habitat Relationships: Concepts and Applications

The study of wildlife populations often includes a habitat component, and understanding the functional relationship between a species and its habitat is challenging. The theoretical and analytical tools for doing so are many, and there are numerous texts that focus on but a fraction of this material. Morrison et al. provide a broad yet thorough overview of wildlifehabitat relationships in a well organized and easy to read book that includes background material, summarizes contemporary techniques for measuring these relationships, and offers links to management strategies

The Influence of Habitat on Nest Survival of Snowy and Wilson\u27s Plovers in the Lower Laguna Madre Region of Texas

Snowy Plovers (Charadrius alexandrinus) and Wilson’s Plovers (Charadrius wilsonia) are two shorebird species that nest along the Gulf Coast of the US. We modeled the daily nest survival of both species in the lower Laguna Madre region of Texas during the 2003 and 2004 breeding seasons as a function of nest age, year, day in the season, maximum daily temperature, daily precipitation, and habitat features at three spatial scales (microhabitat, a 25-m radius of the nest, and landscape). Daily survival of Snowy Plover nests increased with nest age ( Age = 0.03, 95% confi dence limits were –0.01, 0.07, on a logit scale), but did not vary between years. Nests inland had substantially lower daily survival than nests on the coast ( Inland = –0.18, 95% confi dence limits were –1.03, 0.67, on a logit scale). The presence of a conspicuous object at the nest site increased daily nest survival. A quadratic trend occurred on the coeffi cient of variation (CV) for low vegetation (CV used as an index of low vegetation spatial heterogeneity) at the 25-m scale for Snowy Plover nests. Daily nest survival of Wilson’s Plovers was best explained by a combination of two habitat metrics at the microhabitat scale. Less vegetation at the immediate nest site increased daily survival ( Veg = –1.35, 95% confi dence limits were –2.28, –0.42, on a logit scale) while daily nest survival was higher for nests with lower contagion at the microhabitat scale ( Contagion = –0.87, 95% confi dence limits were –1.65, –0.10, on a logit scale). We found no evidence for yearly differences or an effect of weather on the daily nest survival of either species. Our results illustrate the role that selected habitat features play in the nest survival of Snowy and Wilson’s plovers and further our understanding of their nesting ecology. We anticipate that our results will assist in the identifi cation and protection of habitats critical to breeding populations of these and other shorebird species

Egg crypsis in a ground-nesting shorebird influences nest survival

Coloration of exposed eggs of ground-nesting birds is thought to reduce predation, with camouflaged eggs that more closely match the area around the nest having greater survival. We tested this hypothesis using digital photographs of 374 Mountain Plover (Charadrius montanus) nests and the substrate surrounding each nest to produce covariates in nest survival models. Covariates included values representing the difference between the color of the eggs and that of the substrate, the average egg and substrate colors, and variation in both egg and substrate color. Nest survival decreased as the difference between the color of the eggs and substrate increased (accounted for by two different methods of quantifying color and increased with increasing variability in substrate color, although after model-averaging these effects were not well-supported. Model-averaged estimates of daily nest survival ranged from 0.90 to 0.98 (unconditional SEs from 0.004 to 0.129). Our results support the egg crypsis hypothesis because eggs that closely match their surroundings have greater survival

Density and Abundance of Mountain Plovers in Northeastern Montana

Estimates of local abundance for declining species provide important information necessary for conservation measures. We estimated the density and abundance of Mountain Plover (Charadrius montanus) in Phillips and Valley counties in north-central Montana in 2004 using distance sampling methodology. Sampling efforts were stratified to include active prairie dog (Cynomys sp.) colonies, an Area of Critical Environmental Concern (ACEC) specifically established for Mountain Plover, and all other habitats. The density of plovers was greatest on prairie dog colonies (7.20 ± 0.42 [SE] plovers/km2) and much lower on both the ACEC (1.60 ± 0.31 plovers/km2), and all other habitats (0.07 ± 0.01 plovers/km2). An estimated 1,028 (95% CI = 903–1,153) plovers inhabited this region in 2004, most (74%) on prairie dog colonies. Our results highlight the importance of prairie dog colonies to plovers in this region and suggest that as much as 10% of their continental population may breed in north-central Montana

An Assessment of the Status of White-Faced Ibis (Plegadis chihi) in the Great Plains

Recent increases of White-faced Ibis (Plegadis chihi) in the Great Plains have been considered a reoccupation of the species\u27 former range. Review of the published literature and specimen record, however, indicates that this species has only recently become a regular breeder in the Great Plains; thus, recent patterns of summering and nesting birds in the region are best considered a range expansion. Currently. this species is increasing in the Great Plains, where it is an uncommon migrant and local breeder. Extralimital records of this species arc also increasing, both along the Atlantic Coast and the Gull Coast, probably indicative o[ the health o[ the mid-continental breeding population. The status of this species in the Great Plains appears linked to fluctuations o[ core breeding populations, especially those in the Intermountain West

Factors affecting Burrowing Owl occupancy of prairie dog colonies

Understanding patch dynamics can help scientists better understand metapopulations and the relationships of animals that share a habitat. The Burrowing Owl (Athene cunicularia) is a well-known associate of prairie dog colonies, thereby linking conservation measures that benefit these species. We used occupancy modeling to determine how colony attributes (e.g., size and edge effects) and the loss of prairie dog colonies to sylvatic plague affected the occupancy of those colonies by Burrowing Owls in north-central Montana. We surveyed presence–absence of Burrowing Owls during a 13-yr period (1995–2007) and analyzed the data using a robust-design occupancy model in Program MARK. The proportion of colonies occupied by Burrowing Owls ranged from 0.41 to 0.54 across years while the probability of detecting the owls ranged from 0.22 to 0.92. Contrary to our predictions, colony edge effects and plague epizootics showed only weak or no effects on Burrowing Owl occupancy. Prairie dog colony size had the greatest effect on Burrowing Owl occupancy patterns. Colonization of prairie dog colonies by owls generally increased with colony area, whereas owl extinction initially dropped and then increased as a function of increasing colony area. We found no direct link between Burrowing Owl occupancy of prairie dog colonies and plague history, but our results reaffirmed the importance of colony size. Collectively, this information will help inform future conservation efforts for Burrowing Owls that occupy prairie dog colonies

Waterbird Use of Sheetwater Wetlands in Iowa’s Prairie Pothole Region

Large expanses of land across midcontinental North America have been heavily modified by installation of artificial drainage to convert prairie pothole wetlands into tillable areas. Drained potholes are observed as sheetwater wetlands in agricultural fields, are valued by migratory waterbirds, and have only been studied in limited contexts. We evaluated the use of agricultural sheetwater to migratory waterbirds in Iowa’s Prairie Pothole Region and hypothesized that wetland size would be an important predictor of waterbird use. We observed 1913 unique wetlands and documented waterbird use on 31% of observations of those wetlands. The most frequently detected waterbirds were Killdeer, Mallard, Blue-winged Teal, and Lesser Yellowlegs. Wetland size had a positive effect (P \u3c0.05) on waterbird species richness and abundance. The findings from this study will help inform future decisions on drainage practices and their impact on wildlife and indicate the need to examine this habitat type at larger temporal and spatial scales

Changing Seasons: Weatherbirds

The fall migration marks a transition between the breeding and non-breeding seasons. While some species, such as Mourning Dove, are still reproductively active well into autumn, most species that breed north of Mexico and the Caribbean have completed their primary breeding period, and those that migrate are making their way to wintering areas. The sojourn to nonbreeding sites includes some epic migrations, some of which are still being discovered--for example, the 11,000-km presumably non-stop flight of baueri Bar-tailed Godwits from coastal Alaska to New Zealand. Most species have much shorter flights, usually broken into segments, and other species reside in the same area year-round or make only facultative movements

Mountain Plover Responses to Plague in Montana

Plague is a bacterial (Yersinia pestis) disease that causes epizootic die-offs in black-tailed prairie dog (Cynomys ludovicianus) populations in the North American Great Plains. Through their grazing and burrowing, prairie dogs modify vegetation and landscape structure on their colonies in ways that affect other grassland species. Plague epizootics on prairie dog colonies can have indirect effects on species associated with colonies. The mountain plover (Charadrius montanus) preferentially nests on black-tailed prairie dog colonies and is thus negatively impacted by the loss of prairie dogs. We studied the effects of plague and colony spatial characteristics on the occupancy of 81 prairie dog colonies by nesting plovers in Phillips County, Montana, during a 13-year period (1995–2007). We used a robust design patch occupancy model to investigate how colony occupancy and extinction and colonization rates were affected by plague history, colony size, and colony shape. Here extinction and colonization rates refer to the probability that a colony loses/gains plovers in a subsequent nesting season, given that it had/lacked plovers in that breeding season. Colony occupancy was best explained by a model with no annual variation or plague effects. Colony extinction rates were driven by a combination of a quadratic of colony area, a 3-year plague response, and a measure of colony shape. Conversely, colonization rates were best explained by a model with a 4-year plague response. The estimated annual proportion of colonies occupied by plovers was 0.75 (95% confidence interval = 0.57–0.87). Estimated extinction probability ranged from a low of 0.07 (standard error [SE] = 0.02) in 2002 to a high of 0.25 (SE = 0.03) in 1995; colonization probability ranged from 0.24 (SE = 0.05) in 2006 to 0.35 (SE = 0.05) in 2000. Our results highlight how a bird that depends on prairie dogs for nesting habitat responds to plague history and other spatial characteristics of the colony. Ultimately, this information will broaden our understanding of the impact of plague on species other than the host