Nest Depredation Research Articles

Do artificial nests simulate nest success of greater sage-grouse?

Artificial nests have been used to study factors affecting nest success because researchers can manipulate them more than natural bird nests. Many researchers have questioned the validity of generalizing the results from artificial nests onto naturally occurring nests. Other studies have assessed the validity of artificial nest studies by simultaneously comparing overall depredation or daily survival rates, depredation timing, predator species, or habitat characteristics of artificial and natural nests. To evaluate how well artificial nests simulated nest success of greater sage-grouse (Centrocercus urophasianus; hereafter, sage- grouse), we used the unique approach of monitoring artificial nests (n = 69) placed in the natural nest bowls of sage-grouse in southern Wyoming, USA, during 2010 to 2011. Brown chicken eggs were placed in natural sage-grouse nests 7 to 14 days after the hatch or depredation of natural sage-grouse nests to compare artificial nest fate to the fate of natural sage-grouse nests. As secondary objectives, we placed cameras next to a subset of artificial nests to identify which predator species were depredating nests, and we assessed the effects of corvid (black-billed magpie (Pica hudsonia) and common raven (Corvus corax)) density, nest-site characteristics (i.e., anthropogenic development, landscape variables, and microhabitat) date of depredation, and presence of a camera near nest bowls on the depredation rate of all artificial nests. We found that depredation of artificial nests paralleled the fate of natural sage- grouse nests. Depredations were more likely to occur earlier in the summer (June to early July rather than late July to early August). Depredation of artificial nests was negligible as time progressed past the typical sage-grouse nesting season, supporting the hypothesis of predators using a search image to detect eggs. We also found that shorter perennial grass height and greater magpie densities were positively associated with the depredation rates of artificial nests. Camera-recorded depredation events verified that 4 badgers (Taxidea taxus), 2 magpies, and 1 domestic cow depredated artificial nests. Artificial nests may give managers insight into the expected nest success rates of sage-grouse in areas of conservation interest. However, care must be taken regarding placement and timing of artificial nests for reliable conclusions to be drawn from artificial nest studies. Furthermore, identifying predators based on artificial nests likely leads to inaccurate assessment of local species composition of nest depredators.

Agri-evironmental schemes and active nest protection can increase hatching success of a reintroduced farmland bird species

Throughout Europe ground-nesting farmland bird species are rapidly declining and have become a conservation concern. Intensive agriculture and high nest predation rates are major factors causing the decline. Species conservation efforts often focus on habitat enhancement to increase the quantity and quality of available habitat structures (habitat enhancement hypothesis) or active nest protection by fencing and predator control (predation mitigation hypothesis). Within the context of a reintroduction project of grey partridges (Perdix perdix) into two regions of Switzerland, we investigated breeding habitat preferences and hatching success in relation to properties of the habitat surrounding the nest. Then we tested whether predator exclusion by fencing can increase hatching success. The location and hatching success of 121 nests were observed by radio-tracking and available habitats in both regions were mapped. Grey partridges preferred nesting habitats in highly heterogeneous wildflower areas, which had been implemented as biodiversity promoting areas (BPA) and nest fencing significantly increased hatching success. Likewise, increased proportions of wildflower BPAs tended to enhance hatching success, which is probably related to higher availability of cover in these structures. Increasing proportions of cover vegetation around the nest had a positive effect on hatching success. Increasing the quality of rural habitats by providing heterogeneous habitat structures as well as reducing predator access to nests by fencing can increase hatching success in grey partridges and is likely to benefit other ground-nesting birds as well. In fact, high amounts of cover vegetation around the nest can compensate for nest fencing by hampering nest depredation.

Toucans descend to the forest floor to consume the eggs of ground-nesting birds

Toucans (Ramphastidae) are mostly frugivorous birds with important links to seed dispersal in the Neotropics. They are less frequently observed to prey upon invertebrates, small vertebrates, and canopy and cavity bird nests. As part of a nest predator study, we created artificial tinamou (Tinamidae) ground-nests and monitored them with camera traps in La Selva Biological Station (Costa Rica) and surrounding forest fragments. The camera traps revealed two species of toucan descend to the ground to consume the eggs. We are unaware of any other reports of toucans depredating nests on the forest floor. We suggest that toucans might be more opportunistic than expected, particularly in disturbed or fragmented habitats where fruiting trees can be sparse. Toucans could conceivably limit the abundance of other birds via nest depredation on the forest floor and exert selection pressure via eco-evolutionary feedbacks.

Sharp-Tailed Grouse Nest Survival and Nest Predator Habitat Use in North Dakota's Bakken Oil Field.

Recent advancements in extraction technologies have resulted in rapid increases of gas and oil development across the United States and specifically in western North Dakota. This expansion of energy development has unknown influences on local wildlife populations and the ecological interactions within and among species. Our objectives for this study were to evaluate nest success and nest predator dynamics of sharp-tailed grouse (Tympanuchus phasianellus) in two study sites that represented areas of high and low energy development intensities in North Dakota. During the summers of 2012 and 2013, we monitored 163 grouse nests using radio telemetry. Of these, 90 nests also were monitored using miniature cameras to accurately determine nest fates and identify nest predators. We simultaneously conducted predator surveys using camera scent stations and occupancy modeling to estimate nest predator occurrence at each site. American badgers (Taxidea taxus) and striped skunks (Mephitis mephitis) were the primary nest predators, accounting for 56.7% of all video recorded nest depredations. Nests in our high intensity gas and oil area were 1.95 times more likely to succeed compared to our minimal intensity area. Camera monitored nests were 2.03 times more likely to succeed than non-camera monitored nests. Occupancy of mammalian nest predators was 6.9 times more likely in our study area of minimal gas and oil intensity compared to the high intensity area. Although only a correlative study, our results suggest energy development may alter the predator community, thereby increasing nest success for sharp-tailed grouse in areas of intense development, while adjacent areas may have increased predator occurrence and reduced nest success. Our study illustrates the potential influences of energy development on the nest predator—prey dynamics of sharp-tailed grouse in western North Dakota and the complexity of evaluating such impacts on wildlife.

Influence of Habitat Type and Prescribed Burning on Feral Swine Depredation of Artificial Quail Nests

Feral swine (Sus scrofa) have increased both spatially and numerically in the Rolling Plains of northwest Texas. Resource managers have little information on the interrelationships between feral swine and native species such as the northern bobwhite (Colinus virginianus). Nest predation by feral swine could adversely affect bobwhite reproduction. Honey mesquite (Prosopis glandulosa) and redberry juniper (Juniperus pinchotii) are the dominant woody plants in northwestern Texas and prescribed burning is used to manage both species. Two experiments were conducted to determine the extent of feral swine depredation on artificial quail nests. In 1992-93, we monitored nest loss in mesquite and juniper habitats for six weeks. Total depredation reached 85 and 98% after three and six weeks respectively, during 1992, compared to 60 and 92% in 1993. Feral swine depredation of artificial bobwhite nests was 33% across years and was evenly distributed between vegetation types. During three-week periods in June and July 1994, depredation was greater (P<0.001) in an unburned (90%) pasture than in unburned areas within a burned (32%) pasture. Decreased predator activity in the burned pasture was probably due to temporary prey displacement and less forage. Feral swine depredation of artificial bobwhite nests was 14% in 1994. Feral swine could potentially have negative impacts for northern bobwhites in mesquite and juniper habitats of northwest Texas.

Predators and Prickly Paradigms: Nesting Ecology of Bobwhites and Scaled Quail in West Texas

Sporadic recruitment appears to be the impetus for the irruptive population patterns observed along the western edge of northern bobwhite (Colinus virginianus) range. We investigated hen survival, nest selection strategies, and reproductive success of sympatric northern bobwhites and scaled quail (Callipepla squamata) in west Texas. Radio-marked bobwhites, along with a smaller sample of sympatric scaled quail, were monitored during the spring and summer of 1994 and 1995. Predation was the major source of mortality, with mammals and raptors responsible for about 60 and 30 percent of the mortalities observed, respectively. We used TrailMaster camera systems to document the presence and behavior of various nest predators. Raccoons (Procyon lotor) appear to be the dominant nest predator in this area, accounting for over 80 percent of the nests destroyed. Photographic surveillance of artificial nests provides some clues for making objective assessments of predators involved in nest depredations. The amount and kinds of egg shell evidence at a nest site varied with egg size (chicken vs quail). We found egg shell evidence at 83 percent of nests using chicken eggs, but only at 3 percent of nests using quail eggs. We predict that snakes are overrated in their importance as a nest predator, when such diagnoses are based solely on the absence of physical evidence (i.e., no egg shells). Our results suggest that pricklypear (Opuntia spp.) was a key nesting microhabitat. Overall, 12 of 21 bobwhite and 8 of 12 scaled quail nests were located in pricklypear. Subsequent investigations revealed that nests situated in pricklypear were afforded higher survival, especially in more arid sites with less traditional nesting cover (e.g., Schizachyrium scoparium). Initial results with intensive, short-term mammal removal suggest that nest survival can be increased for about $0.35 per hectare.

Macrohabitat Composition Surrounding Successful and Depredated Northern Bobwhite Nests

Relationships among macrohabitat and depredation of northern bobwhite (Colinus virginianus) nests are poorly understood. Yet, macrohabitat composition may influence the nest predator community and, therefore, the vulnerability of northern bobwhite nests to depredation. We determined if macrohabitat composition surrounding bobwhite nests influenced nest placement, nest success, and which predators were responsible for depredating nests. We characterized macrohabitats at 2 scales, 8 and 16 ha, by surrounding both bobwhite nests, and an equal number of random locations, with a circular buffer. Random points were placed within the area used by bobwhites on our study area. We then determined the acreage of each macrohabitat category within each circular buffer to determine the macrohabitat composition. Macrohabitat categories included hardwood forested drains, upland pine forests burned in March of the same calendar year, upland pine forests burned in March of the previous calendar year, and fields. We documented nest predators using infrared video cameras placed at the nest site. We monitored 104 bobwhite nests on Tall Timbers Research Station (TTRS) during 1999 and 2000. Size of the circular buffer around nests did not qualitatively affect results. Area (ha) of upland pine forests and fields were similar at depredated nests, hatched nests, and random locations. However, there was an average of 81% and 56% more area of hardwood drain in the circular buffers associated with random locations than at successful and depredated nests, respectively. Area of upland pine forests and fields were similar for nests depredated by raccoon (Procyon lotor), armadillo (Dasypus novemcinctus) and snake (Elaphus spp.). However, there was an average of 6.1 and 3.3 times more area of hardwood drain surrounding nests that were depredated by snakes relative to nests depredated by raccoons and armadillos, respectively. While our sample sizes were low, bobwhites exhibited a tendency to place nests in landscapes with less hardwood drain than were generally available on the study area. Macrohabitat surrounding nests influenced the type of nest predator to depredate nests. To minimize depredation of bobwhite nests by snakes, we suggest nesting cover should be developed away from drain edges.

Depredation Patterns and Northern Bobwhite Nest Success in Field Borders

Northern bobwhite (Colinus virginianus) populations have declined because of habitat loss and fragmentation. Field borders provide additional habitat for northern bobwhites and other wildlife that depend on early-succession habitat. However, their proximity to woods as well as other edge types may result in increased bobwhite nest depredation. We examined if northern bobwhite nest survival in field borders decreased with increasing proximity to edges such as woods, crop fields, ditches, and roads; effects of year, camera presence, and field border width also were considered. We examined if snakes are the primary nest predator with 24-hr video camera surveillance. We searched for and monitored northern bobwhite nests on ~ 77 ha of field borders in southeast North Carolina during summers 2010 and 2011. We found 26 nests and monitored them every 3–4 days. Fourteen nests were monitored with cameras. We built nest survival models using the covariates of distance to nearest woody edge, crop field, ditch, and road as well as year, camera effect, and field border width. The most explanatory model was constant northern bobwhite nest survival with an estimated daily nest survival 6 SE of 0.9512 6 0.0119 (AICc weight 1⁄4 0.23). Models with covariates suggested similar daily nest survival rates. Four snake and two mammalian predation events were recorded on camera. Distance to edge types and field border width did not appear to influence the outcome of nests in an agriculture-dominated landscape. Thus, landowners and managers in an agriculture-dominated landscape may have flexibility with field border placement and distance to edge type as they relate to nest success.

Comparative Breeding Biology of Three Insectivorous Songbirds in Dutch Dune Grasslands

Scholars agree that changes in vegetation have been influencing population sizes of ground-foraging songbirds in Dutch dune grasslands. Due to a lack of knowledge concerning the breeding biology of these species, the mechanisms linking vegetation change and population development remain unclear. Here, I describe the breeding biology of three co-occurring insectivores in Dutch dune grasslands: Meadow Pipit Anthus pratensis, European Stonechat Saxicola torquatus and Northern Wheatear Oenanthe oenanthe. The nestling diet of Meadow Pipits contained many dipterans, such as crane flies (Tipulidae), but almost no beetles and relatively few noctuid caterpillars, whereas beetles and noctuid larvae were important in the diets of both European Stonechat and Northern Wheatear nestlings. Mean brood size was smallest in Meadow Pipit and equal in European Stonechat and Northern Wheatear. Nest depredation was similarly high in the open-nesting Meadow Pipit and European Stonechat, resulting in lower nest success compared ...

Can hedgerow management mitigate the impacts of predation on songbird nest survival?

Nest predators can have significant impacts on songbird reproductive success. These impacts may be amplified by habitat simplification and here we test whether sympathetic management of farmland hedgerows can reduce nest depredation, especially by corvids. We test whether songbirds select nest sites according to structural features of hedgerows (including nest visibility and accessibility), and whether these features influence nest predation risk. Songbirds selected nesting sites affording higher vegetation cover above the nest, increased visibility on the nest-side of the hedgerow and reduced visibility on the far side of the hedge. Nest survival was unrelated to corvid abundance and only weakly related (at the egg stage) to corvid nest proximity. Nest survival at the chick stage was higher where vegetation structure restricted access to corvid-sized predators (averaging 0.78 vs. 0.53), and at nests close to potential vantage points. Overall nest survival was sensitive to hedgerow structure (accessibility) particularly at low exposure to corvid predation, while the overall impact of corvid exposure was dependent on the relationship involving proximity to vantage points. Nest survival over the chick stage was much higher (0.67) in stock-proof, trimmed and mechanically cut hedgerows, (which tended to provide lower side visibility and accessibility) than in recently laid, remnant or leggy hedgerows (0.18). Long-term reductions in the management of British hedgerows may therefore be exposing nesting songbirds to increased predation risk. We recommend regular rotational cutting of hedgerows to maintain a dense woody structure and thereby reduce songbird nest predation.

Habitat Selection of Wild Pigs and Northern Bobwhites in Shrub-Dominated Rangeland

Abstract Sus scrofa L. (Wild Pig) are known to eat the eggs of ground-nesting birds, but it is unknown to what extent they have an impact on populations of Colinus virginianus L. (Northern Bobwhite). We combined data from 2 prior studies conducted on a large ranch in South Texas to assess comparative habit use and selection by Wild Pigs and Bobwhites. Both species were distributed throughout the ranch, but their preferred habitats were very different. Bobwhites favored upland habitats, particularly areas with deep, sandy soils, while Wild Pigs favored low-lying habitats with clay soils. We conclude that depredation of Bobwhite nests by these invasive mammals may be restricted by the thermoregulatory requirement for Wild Pigs to stay near riparian areas. The extent of this effect will depend on the availability and spatial arrangement of water and riparian areas on the landscape.

Effects of common raven and coyote removal and temporal variation in climate on greater sage-grouse nesting success

Predator removal has been simultaneously proposed and criticized as a mitigation measure for low reproductive rates of prey species, including greater sage-grouse (Centrocercus urophasianus; hereafter “sage-grouse”). Depredation of sage-grouse nests can limit their productivity. In Wyoming, lethal removal of common ravens (Corvus corax: hereafter “ravens”) and coyotes (Canis latrans) has been conducted by USDA/APHIS/Wildlife Services (WS) for the protection of livestock. During 2008–2011, we evaluated sage-grouse nest success in study sites (1) where WS initiated a raven removal program, (2) WS removed coyotes, and (3) WS did not manipulate ravens and/or coyotes. Precipitation and temperature were analyzed individually and as interactive effects with coyote removal numbers as sources of annual variation in nest success. Over the course of our study, raven densities decreased at study sites with WS raven removal, while sage-grouse nest success in those study sites was higher during years with reduced raven density. Temperature effects on nest success were dependent on timing with successful nests having cooler temperatures prior to the nesting season (conditions promoting water retention and grass growth) and warmer temperatures the week before nest fate (conducive to degradation of sage-grouse odorants used by mammalian predators). Lower nest success was associated with more lethally removed coyotes interacting with greater precipitation suggesting mesopredator release. Raven removal may have a place in sage-grouse management as an interim mitigation measure when sage-grouse populations are subjected to high densities of ravens. However, long-term solutions are necessary, such as reducing supplemental food sources and perch structures used by ravens.

No effect of blood sampling or phytohaemagglutinin injection on postfledging survival in a wild songbird.

The injection of phytohaemagglutinin (PHA) and sampling of blood are widely used in studies of wild vertebrates to assess components of immune and endocrine function and health state and to obtain genetic material. Despite the pervasive use of these techniques in the life sciences, their potential effects on survival are rarely considered. For example, whether injection of the immunogen PHA into body parts critical for locomotion (e.g., the prepatagium, or wing web, in birds) affects survival has not been tested. Here, we test whether injection of PHA into the wing web and blood sampling from nestling house wrens affects their subsequent recruitment and survival as breeding adults. Capture‐mark‐recapture analysis on a large sample of young (N = 20,152 fledglings from 3959 broods) treated over 10 years revealed that neither PHA injection nor blood sampling affected individual survival and detection probability. Recruitment as a breeder varied among years, but this variation was not attributable to sampling effort, or the percent of all adults identified at the nest during a given year. Variation in the percent of adults identified was primarily attributable to the effect of nest depredation on our ability to capture nesting pairs. Our results indicating lack of an effect of blood sampling and immune stimulation on survival are encouraging, but we recommend further work to assess the potential negative effects of all commonly used techniques on the survival of study subjects in the wild, including the potential costs associated with mounting various immunological responses.

Nest Site Selection and Nest Depredation of Carolina Chickadees

Nest location is an important factor that influences nestlings’ success. Poor nest location could lead to exposure to predators and to a lack of nearby resources. We examined nest site selection and nest depredation of Carolina chickadees (Poecile carolinensis) from 2011–2015 at a field site with artificial nest boxes. In this cavity-nesting species, both members of a breeding pair inspect multiple cavities before deciding on a location to build a nest. We examined whether Carolina chickadee nest location preference and predation rates were related to factors such as proximity to the forest edge, a water source, neighboring cavities, and buildings, as well as the forest type the nest was located in. We found that Carolina chickadee nests that were closer to the forest edge were depredated more often; however, despite this increased risk of nest loss near the forest edge, the chickadees did not prefer boxes located away from the edge. The other factors that we measured were not related to nest box occupancy or predation risk. Future research should focus on why these birds continue to nest in more dangerous edge locations and on what other factors affect their nest selection decisions.

Population dynamics of endangered blanding's turtles in a restored area

Habitat protection and restoration are used to promote recovery in endangered reptile species, yet the long-term consequences of these efforts can be difficult to assess. Measuring the effects of habitat restoration on turtles can be especially difficult because of long generation times and consequent time lags between restoration activities and population-level responses to these activities. We collected 24 years of mark-recapture, size structure, and nest survival data on a population of International Union for Conservation of Nature (IUCN)-Endangered Blanding's turtles (Emydoidea blandingii) inhabiting a large restored wetland-upland complex in Wisconsin, USA. We used these data to examine survival and recruitment in the population and the response of individual aggregations of nesting females to recent restoration of an extensive upland prairie-oak barrens nesting habitat. The population exhibited positive growth over the 24-year period (λ = 1.03) based on temporal asymmetry mark-recapture models. Population growth rates were greatest in a recently restored prairie-barrens nesting area because of relatively high recruitment of nesting females. Females nesting in the recently restored prairie-barrens habitat were smaller and decreased in size over time compared to females using 2 older nesting areas, suggesting that recruitment was relatively high because of an influx of young breeding females. Nest depredation probability decreased with increasing distance from forest edges, suggesting that the recent clearing of woody vegetation in recently restored habitat increased reproductive success. Collectively, our results highlight the potential benefits of habitat restoration to turtles and identify upland habitats as a key to promoting population growth in turtles with complex habitat requirements. © 2015 The Wildlife Society.

Spatio-Temporal Patterns in the Depredation of Waterfowl Nests and Simulated Nests in the Prairie Pothole Region, USA

Abstract Nest depredation is the leading cause of waterfowl nest failures in much of the Prairie Pothole Region, USA. In 2006 and 2007, spatial and temporal patterns of nest depredation were evaluated on 248 waterfowl nests and 88 simulated waterfowl nests in North Dakota, USA. The hypothesis that predators are able to locate adjacent nests using an area-restricted search once they find the first nest and that ducks will space their nests apart to reduce this from happening was tested. However, no evidence was found to support either part of this hypothesis or that density-dependent depredation was occurring. This lack of support, along with no relationship between nest density and nest success, indicate that density-dependent depredation may not have been a problem in our study area. Artificial nests were used to test the hypothesis that meteorological conditions impact nest depredation rates. Artificial nests were more likely to be depredated when either temperature or dew point was high. It was hypothe...

Observations of Territorial Breeding Common Ravens Caching Eggs of Greater Sage-Grouse

Abstract Previous investigations using continuous video monitoring of greater sage-grouse Centrocercus urophasianus nests have unambiguously identified common ravens Corvus corax as an important egg predator within the western United States. The quantity of greater sage-grouse eggs an individual common raven consumes during the nesting period and the extent to which common ravens actively hunt greater sage-grouse nests are largely unknown. However, some evidence suggests that territorial breeding common ravens, rather than nonbreeding transients, are most likely responsible for nest depredations. We describe greater sage-grouse egg depredation observations obtained opportunistically from three common raven nests located in Idaho and Nevada where depredated greater sage-grouse eggs were found at or in the immediate vicinity of the nest site, including the caching of eggs in nearby rock crevices. We opportunistically monitored these nests by counting and removing depredated eggs and shell fragments from the nest sites during each visit to determine the extent to which the common raven pairs preyed on greater sage-grouse eggs. To our knowledge, our observations represent the first evidence that breeding, territorial pairs of common ravens cache greater sage-grouse eggs and are capable of depredating multiple greater sage-grouse nests.

Increased abundance, but reduced nest predation in the chestnut-backed antbird in costa rican rainforest fragments: surprising impacts of a pervasive snake species

Understory insectivorous birds often disappear from fragmented tropical rainforest landscapes before mechanisms such as increased rate of nest depredation can be evaluated. Here, we took advantage of chestnut-backed antbird (Myrmeciza exsul), a representative rainforest understory insectivore that persists in fragments (unlike many other understory species), to identify variables influencing nest predation rate and to test the hypothesis that nest predation underlies avian extirpation in tropical fragments. We compared nest predation rates, bird density, and predator identities in three habitats of lowland Caribbean Costa Rica: two fragments, a peninsular reserve (La Selva Biological Station), and unfragmented rainforest. Our results suggest an inversely density-dependent nest predation pattern: In fragments, chestnut-backed antbirds reached their highest density and—contrary to predictions—experienced their lowest nest predation rates; La Selva on the other hand experienced the lowest density and highest predation rate. Because nest predation decreased with fragmentation, it appears not to explain declines of understory insectivores from forest fragments generally. Nest survival models indicated that habitat best explained nest predation likelihood, whereas edge, annual, and nest age effects were unimportant. Video surveillance documented both bird-eating snake (Pseustes poecilonotus) causing 80% of nest loss overall (37 of 46 nests) and a larger variety of predators in fragments; thus, landscape factors influenced an understory bird’s nest predation. Given the large effect on our focal species, Pseustes likely affects other understory nesters, a topic warranting further study. Tropical reserve conservation plans should consider potential impacts of specialized nest predators on vulnerable understory birds.

Effects of Vegetation Structure and Artificial Nesting Habitats on Hatchling Sex Determination and Nest Survival of Diamondback Terrapins

Abstract It is often the case that multiple factors contribute to wildlife population declines such that management will require simultaneous, integrated interventions to stabilize and recover populations. Diamondback terrapins Malaclemys terrapin are a species of high conservation priority, and local populations can be threatened by multiple factors, including bycatch in commercial and recreational crab pots, vehicle strikes on coastal roads, nest depredation from subsidized and introduced predators, and terrestrial habitat alteration. Mitigation of just one of these factors will often be insufficient for recovering at-risk populations; thus, information to manage multiple threats is needed. We measured the effects of natural vegetation structure and constructed (artificial) nesting habitat on hatchling sex ratios and nest depredation for a declining terrapin population on Jekyll Island, Georgia. Nest temperatures were highest on constructed nesting mounds, intermediate in open grass areas, and coolest under the shrub-dominated hedgerows. Higher nest temperatures led to shorter incubation times for nests on mounds and open habitat, such that all surviving nests on nesting mounds and open areas produced female hatchlings. In contrast, surviving nests under hedge produced 85% male hatchlings. Raccoon Procyon lotor predation rates of simulated (chicken egg) nests were highest on nesting mounds (95.3%), followed by hedge (84.4%) and open habitats (45.2%). Our results demonstrate that vegetation management can positively affect both production of female hatchlings and nest survival. Artificial nest mounds were successful at producing female hatchlings, but we documented high predation of simulated (chicken egg) nests despite structures to exclude predators. Further modifications to nest boxes atop constructed nesting mounds are needed for these devices to effectively contribute to population management. We suggest the relatively low cost and maintenance associated with removing shrubs and trees can be a viable strategy to manage large areas of nesting habitat for the increased production of female turtles, and to reduce the impacts of subsidized predators.

Responses of cavity‐nesting birds to fire: testing a general model with data from the Northern Flicker

Census‐based studies document changes in population size of animal species in response to wildfires, but mechanisms involving behavior of individuals and the effects on reproductive success are usually unknown. I developed a conceptual model explaining the persistence of cavity‐nesting birds on the landscape after fires depending on carrying capacity (food supply) of the habitat and the philopatry and territoriality of the species. The breeding density, nest site characteristics, and reproductive success of Northern Flickers Colaptes auratus was studied before and after low‐ to moderate‐severity fires on replicated plots. The density and spatial distribution of nests did not change in a consistent way after fires, but the rates of cavity excavation increased and characteristics of nest sites changed as such decay class of the tree. Laying dates were delayed and clutches were smaller in freshly excavated vs. reused cavities on the burned sites. Breeding philopatry caused a shift to older age classes in the population. Depredation of nests by small mammals increased during the first three years after fires, reducing the number of young produced per nest attempt on burned plots. The study shows that, even when fire does not reduce the density of breeding pairs, there may be detrimental effects detected only by monitoring the behavior and reproduction of individuals.