Hylocichla Research Articles

Corticosterone stress response and plasma metabolite levels during breeding and molt in a free-living migratory songbird, the wood thrush ( Hylocichla mustelina)

Many birds face energetic trade-offs between different life history stages, such as reproductive effort, feather molt and the non-breeding period. Little is known about how physiological measures of condition (corticosterone, plasma metabolites) in free-living birds change from nesting stages to the post-breeding molt period or whether this is influenced by prior reproductive effort. We evaluated whether corticosterone (CORT) and plasma metabolite levels vary with date, nest stage and sex in a free-living migratory songbird, the wood thrush ( Hylocichla mustelina). We also tested whether (1) baseline CORT levels early in the season were predictive of subsequent reproductive success and (2) whether prior reproductive effort influenced CORT levels and blood metabolites during molt. Baseline CORT levels decreased with date during both the incubation stage and nestling stage, but did not vary significantly across stage of breeding season. Stress-induced CORT declined with date during incubation and varied significantly across breeding stage, with lower levels during feather molt. Profiles of the metabolites of β-hydroxybutyrate, glycerol, and triglyceride did not vary significantly with date or breeding stage. Only triglycerides varied significantly with sex, with females having higher levels than males. Reproductive output was highly variable (0–10 fledglings per season) but baseline CORT levels in females during the first incubation period of the season was not related to subsequent reproductive output. Prior reproductive effort, measured as the cumulative number of young hatched during the breeding season, was positively related to stress-induced CORT during molt. High reproductive effort in wood thrush appears to have physiological carry-over effects into the molt period which could potentially affect rate of molt and preparation for fall migration.

Influence of exurban development on bird species richness and diversity

Exurban development is an accelerating land use trend in the United States with new housing units emerging in formerly closed forests. Conservation practitioners and planners suspect exurban development alters ecological processes and biodiversity to a considerable larger extent than suspected by inhabitants of exurban development areas, but empirical support for this assertion is lacking. To examine the consequences of exurban development, we studied forest bird communities in exurban development and forests located in and around Shenandoah National Park and Massanutten Mountain in northern Virginia, USA. We conducted point-count surveys for birds three times at 106 sample locations from April to July 2006. We recorded 44 species in total; 30 species were present in both exurban development and forests, 9 species were only found in exurban development, and 5 species only in forest. Bird species composition differed significantly between land-use types based on analysis in a multi-response permutation procedure (MRPP; P < 0.01). Relative bird abundance for forest specialist species changed significantly in exurban development versus forest (t test, P < 0.05). Three species, American Robin Turdus migratorius, Northern Cardinal Cardinalis cardinalis, and Common Grackle Quiscalus quiscula were indicators of exurban development. Indicators of forest were Carolina Chickadee Poecile carolinensis, Eastern Towhee Pipilo erythrophthalmus, and Wood Thrush Hylocichla mustelina. Our study demonstrates that exurban development alters bird community composition and relative abundance of forest specialist species.

Dead Birds

I didn't know exactly when my feelings for birds changed. I had once gone for walks in the state park near my home expecting a gift, knowing that I would see a bird that would delight me. I awaited the spring migration of birds through the Piedmont of South Carolina, where I live like a prisoner anticipating release, marking the days and watching and waiting for signs of its coming. First, out of the cold, almost silent, barren winter woods, the lengthening days of January and February would bring the renewed song of the resident birds: cardinals, Carolina wrens, brown thrashers, and robins. Then the fresh, budding leaves of poplar and oaks of March, April, and early May would produce the hatching of caterpillars and other insects. That would entice north, migrating waves of vireos and wood thrush, varied species of subtly beautiful warblers, and bold and brightly colored grosbeaks and tanagers. Each morning, with increasing excitement, I would record these in my journal. But last spring was different. I seldom took the time to look for birds and wrote nothing. For reasons I didn't understand, much of my enthusiasm for birds and most of the rest of life had died.

Modeling spatial variation in avian survival and residency probabilities

The importance of understanding spatial variation in processes driving animal population dynamics is widely recognized. Yet little attention has been paid to spatial modeling of vital rates. Here we describe a hierarchical spatial autoregressive model to provide spatially explicit year-specific estimates of apparent survival (phi) and residency (pi) probabilities from capture-recapture data. We apply the model to data collected on a declining bird species, Wood Thrush (Hylocichla mustelina), as part of a broad-scale bird-banding network, the Monitoring Avian Productivity and Survivorship (MAPS) program. The Wood Thrush analysis showed variability in both phi and pi among years and across space. Spatial heterogeneity in residency probability was particularly striking, suggesting the importance of understanding the role of transients in local populations. We found broad-scale spatial patterning in Wood Thrush phi and pi that lend insight into population trends and can direct conservation and research. The spatial model developed here represents a significant advance over approaches to investigating spatial pattern in vital rates that aggregate data at coarse spatial scales and do not explicitly incorporate spatial information in the model. Further development and application of hierarchical capture-recapture models offers the opportunity to more fully investigate spatiotemporal variation in the processes that drive population changes.

Evaluation of Habitat Suitability Models for Forest Passerines Using Demographic Data

ABSTRACT Habitat suitability is often used as a surrogate for demographic responses (i.e., abundance, survival, fecundity, or population viability) in the application of habitat suitability index (HSI) models. Whether habitat suitability actually relates to demographics, however, has rarely been evaluated. We validated HSI models of breeding habitat suitability for wood thrush (Hylocichla mustelina) and yellow‐breasted chat (Icteria virens) in Missouri, USA. First, we evaluated HSI models as a predictor of 3 demographic responses: within‐site territory density, site‐level territory density, and nest success. We demonstrated a link between HSI values and all 3 types of demographic responses for the yellow‐breasted chat and site‐level territory density for the wood thrush. Second, we evaluated support for models containing HSI values, models containing measured habitat features (e.g., tree age, tree species, ecological land type), and models containing management treatments (e.g., even‐aged and uneven‐aged forest regeneration treatments) for each demographic response using model selection. Models containing HSI values received more support, in general, than models containing only habitat features or management treatments for all 3 types of wildlife response. The assumption that changes in habitat suitability represent wildlife demographic response to vegetation change is supported by our models. However, differences in species ecology may contribute to the degree to which HSI values are related to specific demographic responses. We recommend validation of HSI models with the particular demographic data of interest (i.e., density, productivity) to increase confidence in the model used for conservation planning.

Modeling Spatial Variation in Avian Survival and Residency Probabilities

The importance of understanding spatial variation in processes driving animal population dynamics is widely recognized. Yet little attention has been paid to spatial modeling of vital rates. Here we describe a hierarchical spatial autoregressive model to provide spatially explicit year-specific estimates of apparent survival (ϕ) and residency (π) probabilities from capture–recapture data. We apply the model to data collected on a declining bird species, Wood Thrush (Hylocichla mustelina), as part of a broad-scale bird-banding network, the Monitoring Avian Productivity and Survivorship (MAPS) program. The Wood Thrush analysis showed variability in both ϕ and π among years and across space. Spatial heterogeneity in residency probability was particularly striking, suggesting the importance of understanding the role of transients in local populations. We found broad-scale spatial patterning in Wood Thrush ϕ and π that lend insight into population trends and can direct conservation and research. The spatial model developed here represents a significant advance over approaches to investigating spatial pattern in vital rates that aggregate data at coarse spatial scales and do not explicitly incorporate spatial information in the model. Further development and application of hierarchical capture–recapture models offers the opportunity to more fully investigate spatiotemporal variation in the processes that drive population changes.

Use of landscape metrics to predict avian nest survival in a fragmented midwestern forest landscape

Habitat fragmentation fundamentally affects trophic interactions and ecosystem function. Understanding how the landscape matrix modulates such interactions can improve our understanding of fragmentation ecology. Studies of breeding birds provide clear examples of the consequences of habitat fragmentation, but the landscape context of these effects are unclear. We sampled avian nesting success in 12 moderately-large forest patches (>250 ha) embedded in different types of landscapes in southern Illinois, USA. We then evaluated eight models that predicted the probability of nest success and brood parasitism by Brown-headed Cowbirds. These models incorporated landscape composition (% grassland, % agriculture, fragmentation), year and seasonal effects, conspecific density, predator density, and combinations of these variables. Temporal factors (stage of nesting cycle, seasonal effects, annual variation) had the most effect on nesting success; landscape factors had little influence on nesting success. The rate and intensity of brood parasitism were significantly influenced by the amount of grassland for the Wood Thrush, but not for the Acadian Flycatcher. Fine-scale management of the matrix surrounding the patches may dictate the local abundance and movements of nest predators and parasites. Other major nest predators may prefer the forest interior and at least partially compensate for the lower abundance of nest predators that depend upon the matrix. Overall, landscape metrics were weak predictors of avian nesting success in complex landscapes that have diverse predator communities.

Seed dispersal effectiveness by understory birds on Dendropanax arboreus in a fragmented landscape

This study analyzes dispersal effectiveness of understory birds that feed on fruits of the tropical tree Dendropanaxarboreus in a fragmented forest at Los Tuxtlas, east-central Mexico. The quantity and quality components of effectiveness were estimated in three different sites: continuous forest, 40 ha forest fragment, and 3 ha forest fragment. The quantity component was estimated through relative abundance, frequency of visits to fruits, and number of seeds in fecal samples. The quality component was estimated by analyzing germination of seeds defecated by birds and seed deposition patterns by birds. Seed deposition patterns were estimated by comparing the number of seeds found in fecal samples and the number of reproductive adults of D. arboreus in each site. Results showed that dispersal effectiveness of birds varied among sites. Turdus grayi was the most effective disperser in continuous forest, while Hylocichla mustelina was the most effective one in 40 and 3 ha forest fragments. These birds are contributing to the gene flow between fragments and continuous forest because they are able to use forest or riparian remnants, living fences, and isolated trees.

Misdirected Parental Care by a Male Eastern Towhee at a Wood Thrush Nest

Misdirected parental care, or care directed toward unrelated young, has been recorded for many bird species. The Wood Thrush (Hylocichla mustelina) is not known to practice this behavior or allow other species to attend to its young. We observed a Wood Thrush nest with three Wood Thrush nestlings and one Brown-headed Cowbird (Molothrus ater) nestling being attended by a male Eastern Towhee (Pipilo erythrophthalmus). The towhee fed the young of both species in the nest for at least 5 days and was subsequently observed feeding a Wood Thrush fledgling. The towhee also participated in nest maintenance and defense. The proximate cause of towhee attendance at the Wood Thrush nest remains unknown, but begging calls from the nestlings may have stimulated the behavior.

Redbud Trees (Flowering Judas)

Redbud Trees (Flowering Judas) Helen M. Lewis (bio) In Early Spring Forming a tunnel of blossoms along the road to War, West Virginia The Redbud trees burst forth with knots of red, rosy, purple flowers on naked branches, Circling the trunk like the red kerchiefs worn by coal miners who fought on Blair Mountain. Clinging perilously to mountainsides they make a shrouded gateway to the Billion Dollar Coalfield. But The Billion Dollars left the coalfields. Each spring the red buds tell that story and point to the destruction just over the hill. The mountains have provided a place of refuge for people, animals, trees and flowers, A homeplace in which to settle, work, live, for a diversity of people, wild flowers and grouse. A sanctuary, a haven for mussels, salamanders, Baptists, wood thrush and pileated woodpeckers. Now scavengers are removing the mountains to dig out the coal– Giant machines turn forested hills to moonscapes Cover streams and valleys with “overburden,” reduce the mountains to rubble. Holding fast in the arms of the mountains, Wearing their red badge of courage The Redbuds resist their removal and protest the devastation of their living place [End Page 68] They are also called Judas trees. Named for the Judas who hung himself in shame from a Redbud tree And dangled the blood money from the branches. The Flowering Judases blush with shame. They shout “Shame” to the Judases destroying God’s creation. As the blossoms fade, the heart shaped leaves wave to passers by, Crying out for the wilderness: Wake up, the earth is being destroyed. Change your ways of thinking, acting, being You are part of all living creatures. Recognize your kinship, interdependence Listen—Put your ear to the ground. Listen to the voices from the mountains. Listen to the prophets, the hemlocks, the dogwoods, fish in the streams, the bacteria in the soil, all living things. The mountains have provided a fortress: support and strength to survive, For immigrants, moonshiners, Indians, copperheads, escaped slaves and servants. A safe place—“a place to rest your eyes.” When the mountains are gone where do we get our strength? Where do we find the rock to hide behind or beneath? Where do we find solace and rest for our eyes? Put a sign in your yard—Obey the Laws of Nature. [End Page 69] Helen M. Lewis Helen M. Lewis has been a pioneer in Appalachian Studies as a sociology professor in the Virginia coalfields and as Loyal Jones’s successor at the Berea College Appalachian Center. Her activism included serving as Director of the Highlander Center. She now lives in North Georgia. Copyright © 2009 Berea College

Variation in the extra-pair mating systems of Acadian Flycatchers and Wood Thrushes in forest fragments in southern Ontario

The application of molecular tools to studies of avian mating systems has revealed that most songbird species engage in extra-pair matings. However, little is known about the possible effects of habitat fragmentation on extra-pair mating systems. During the breeding seasons of 2002 and 2003, we quantified the frequency of extra-pair matings in Acadian Flycatchers (Empidonax virescens) and Wood Thrushes (Hylocichla mustelina) nesting in forest fragments in southern Ontario. Acadian Flycatchers are at the limit of their northern range in southern Ontario and occurred at low densities (0.005-0.015 males/ha). Across forest fragments, 14% of young Acadian Flycatchers were the result of extra-pair fertilizations. In contrast, Wood Thrushes were common in forest fragments, with breeding densities ranging from 0.37 to 1 males/ha. Extra-pair mating was common among Wood Thrushes, with 40% of young the result of extra-pair matings. Compared to populations studied in less fragmented habitats in Pennsylvania, rates of extra-pair paternity in Ontario were lower for Acadian Flycatchers and higher for Wood Thrushes. Our results demonstrate that rates of extra-pair mating can vary across landscapes. However, the extra-pair mating systems of Acadian Flycatchers and Wood Thrushes appear to respond differently to fragmentation. We suggest that low breeding densities on fragments may be mediating the low rates of extra-pair mating observed in Acadian Flycatchers in southern Ontario, whereas changes to the behavioral tactics of male and female Wood Thrushes in southern Ontario may explain the high levels of extra-pair mating.

Fitting probability models to population dynamics data

Methods for modeling population dynamics in probability using the generalized point process approach are developed. The life history of these populations is such that seasonal reproduction occurs during a short time. Several models are developed and analyzed. Data about two species: colonial spiders ( Stegodyphus dumicola) and a migratory bird (wood thrush, Hylocichla mustelina) are used to estimate model parameters with appropriate log maximum likelihood functions. For the spiders, the model is fitted to provide evolutionary feasible colony size based on maximum likelihood estimates of fecundity and survival data. For the migratory bird species, a maximum likelihood estimates are derived for the fecundity and survival rates of young and adult birds and immigration rate. The presented approach allows computation of quantities of interest such as probability of extinction and average time to extinction.

Forest birds and forest management in Ontario: Status, management, and policy

This paper presents a summary of presentations and discussions at a 3-day workshop on research and management of forest birds in Ontario forests. While many forest birds in Ontario do not appear to be negatively affected over the long term by forest management, some species were noted as declining using Breeding Bird Atlas data and more research is required to understand the causes, some of which may well be related to habitat change on the wintering grounds. For example, the aerial foragers as a group have declined significantly during the past 20 years. Recent research suggests landscape convergence between managed and fire-origin stands for bird species over time, but negative effects were suggested for boreal chickadee (Poecile hudsonsicus), brown creeper (Certhia familiaris), and some cavity-users, although there is no evidence of declines in these species from the current atlas data. This inconsistency needs to be evaluated. In Carolinian forests, even small-scale tree harvesting in this already highly fragmented landscape can have deleterious effects on breeding success for some species, such as wood thrush (Hylocichla mustelina) and rose-breasted grosbeak (Pheucticus ludovicianus). New modelling techniques and meta-analyses seem to hold considerable promise as tools to help managers understand key habitats, species that require special attention, and as predictive models of forest management effects. A large number of recommendations to improve the management of forest birds are provided and as is a suggested research agenda to improve our understanding of key factors affecting birds in managed forests. Key words: forest birds, forest management, boreal forest, Great Lakes–St. Lawrence forest, Carolinian forest, indicators, modelling, cavity nester, spruce budworm, forest policy, Ontario

Tracking Long-Distance Songbird Migration by Using Geolocators

We mapped migration routes of migratory songbirds to the Neotropics by using light-level geolocators mounted on breeding purple martins (Progne subis) and wood thrushes (Hylocichla mustelina). Wood thrushes from the same breeding population occupied winter territories within a narrow east-west band in Central America, suggesting high connectivity of breeding and wintering populations. Pace of spring migration was rapid (233 to 577 kilometers/day) except for one individual (159 kilometers/day) who took an overland route instead of crossing the Gulf of Mexico. Identifying songbird wintering areas and migration routes is critical for predicting demographic consequences of habitat loss and climate change in tropical regions.

Age-specific reproduction and survival of individually marked Wood Thrushes,Hylocichla mustelina

Several nonexclusive, sometimes contradictory, hypotheses have been employed to explain age-related changes in reproduction and survival among vertebrates. We evaluated these hypotheses with observations collected from a 31-year study of individually marked Wood Thrushes (Hylocichla mustelina). Age-specific fledgling production, survival probabilities, and derived life table columns are presented here. Additionally, we report "genetic value," or the number of young remaining to be recruited into the breeding population by individuals of age x. Controlling for age of mate, the presence of some individuals in multiple years, and the effect of year of breeding, reproduction and survival peaked in middle-aged birds of each sex and declined later in life for the oldest individuals. We could not exclude the selection hypothesis (removal of inferior individuals) as an explanation for improved female reproduction until middle age. The age at last reproduction was a significant determinant of age-related reproductive success, indicating a disappearance of low-quality individuals. Yearling females that did not successfully reproduce had greater within-season emigration than all other age classes of each sex, regardless of the reproductive success of other classes. For males, we favored the constraint hypothesis (improved reproduction with experience) to explain greater reproductive output with increasing age until at least middle age. For each sex, the age of the mate independently influenced all measures of reproductive performance, but there was generally a linear or quadratic, rather than interactive, effect of the mate's age on reproduction. For both sexes, hypotheses of age-related reproduction were only partially supported because of effects of senescence, or a decline in reproductive output or survival probabilities with increasing age. Senescence may confound attempts to examine or apply general hypotheses of age-related reproduction that assume a monotonic relationship between age and reproduction or survival.

Relationship between energetic condition and indicators of immune function in thrushes during spring migration

Evidence suggests that the ability of an animal to maintain its immune system and (or) mount an immune response depends on its nutritional health and energetic condition. Migration is a period within an animal’s annual cycle when energetic condition varies, especially after a long, nonstop flight over a large ecological barrier. Our objective was to determine if measures of immune function in migrating Wood Thrush ( Hylocichla mustelina (J.F. Gmelin, 1789)), Swainson’s Thrush ( Catharus ustulatus (Nuttall, 1840)), Gray-cheeked Thrush ( Catharus minimus (Lafresnaye, 1848)), and Veery ( Catharus fuscescens (Stephens, 1817)) were related to the energetic condition of the birds at a stopover site during spring migration. We present data on total leukocyte, lymphocyte, and heterophil counts, heterophil/lymphocyte ratio, serum immunoglobulin gamma G (IgG) concentration, and immune response to phytohemagglutinin. Thrushes arriving at the stopover site in poor energetic condition had low leukocyte and lymphocyte counts. Heterophil/lymphocyte ratio, heterophil count, and IgG concentration were not related to energetic condition. Furthermore, immune response to phytohemagglutinin was positively related to change in mass and days spent in captivity, suggesting that immune function may improve during stopover. We suggest that migrating thrushes arriving at a stopover site in poor energetic condition may also be in poor immunological condition and may have increased susceptibility to disease or parasite infection.

Autumn Stopover Near The Gulf Of Honduras By Nearctic-Neotropic Migrants

Abstract The southeastern Yucatan Peninsula hosts high numbers of transient Nearctic-Neotropic migrants during autumn migration, but the importance of this region during migratory stopover has not been addressed. We studied autumn stopover body mass gains among passerine migrants in tropical lowland forest 20 km inland from the Gulf of Honduras. Most individuals captured had some subcutaneous fat. Ten of 15 taxa with sufficient sample sizes had significant positive diel (24 hr) gains in a body condition index. Estimates of net mass gains in these 10 taxa suggested they all were depositing fat; average individuals in four of these taxa were depositing sufficient fuel to undertake an entire night of migration after only 1 day of fattening: Empidonax spp., Red-eyed Vireo (Vireo olivaceus), Gray Catbird (Dumetella carolinensis), and Northern Waterthrush (Seiurus noveboracensis). Two (Wood Thrush [Hylocichla mustelina] and Common Yellowthroat [Geothlypis trichas]) of the four species apparently not gaining mas...

Effects of Hemlock Woolly Adelgid on Breeding Birds at Fort Indiantown Gap, Pennsylvania

To determine how Tsuga canadensis (eastern hemlock) decline caused by Adelges tsugae (hemlock woolly adelgid) affects bird communities in Pennsylvania, we surveyed breeding birds in hemlock and forested non-hemlock habitats in 2003 and 2004 at Fort Indiantown Gap, PA and monitored nesting Empidonax virescens (Acadian Flycatcher), a hemlock specialist in Pennsylvania. Of the nine species more abundant in hemlocks than other forested habitats, only two, the Acadian Flycatcher and Dendroica virens (Black-throated Green Warbler), were positively associated with living hemlocks. Contopus virens (Eastern Wood-pewee), Myiarchus crinitus (Great-crested Flycatcher), and Hylocichla mustelina (Wood Thrush) were negatively associated with the amount of living hemlocks and were apparently benefiting from the increased number of dead trees and canopy gaps associated with the adelgid infestation. Acadian Flycatcher nest sites had more living hemlocks and were less impacted by adelgid than random sites. Nest success did not differ by habitat variables. Initially, hemlock decline will negatively impact hemlock specialists while providing habitat for opportunistic species. Some specialist species might persist by shifting habitats, but long-term studies are needed.

Wood thrush nest success and post‐fledging survival across a temporal pulse of small mammal abundance in an oak forest

1. Synchronized mass production of seed crops, such as acorns, produces a resource pulse that may have far-reaching consequences for songbird populations through its effects on avian predators. Seed production in these forests represents only the first of several pulsed events. Secondary pulses emerge as mast-consuming rodents numerically respond to seed production and tertiary pulses emerge as generalist predators, such as raptors, numerically respond to rodents. In turn, these two groups reduce nest productivity and juvenile survivorship 1 and 2 years, respectively, after the initial pulse in seed production. 2. At our study site in south-eastern New York, USA, autumn acorn abundance (primary pulse) largely determines rodent abundance (secondary pulse) the following spring. We tested the hypotheses that the population dynamics of a shrub-nesting passerine (wood thrush Hylocichla mustelina), is influenced by rodents through the: (a) direct effect of predation by rodents; (b) indirect effect of rodents on the abundance of raptors (tertiary pulse); and (c) indirect effect of rodent abundance on raptor diet. The latter specifically hypothesizes that a crash in the rodent population in the wake of region-wide failure of acorn production leads to an extreme diet shift in raptors that increases post-fledging mortality in birds. 3. We conducted a 3-year study to examine variation in wood thrush nest success and fledgling survival, using radio telemetry, across a pulse of rodent abundance (i.e. low, medium and high). We also updated and reanalysed regional wood thrush population growth rates as a function of the annual variation in rodent abundance. 4. Fledgling survivorship, but not nest success, varied in relation to annual rodent abundance. Raptors and eastern chipmunks Tamias striatus were the most commonly identified predators on fledglings. Fledgling survivorship was greatest at intermediate rodent abundance consistent with a shift in raptor diet. Regional rate of wood thrush population growth showed a unimodal relationship with rodent abundance, peaking during years with intermediate rodent abundance. This unimodal pattern was due to wood thrush population growth rates near or below zero during rodent population crashes. 5. The telemetry study, pattern of regional abundance and synchronized population dynamics of coexisting thrushes suggest a common mechanism of behavioural changes in raptors in response to declines in rodent prey, which in turn affects thrush population dynamics.

Uncertainty in spatially explicit population models

Spatially explicit population models (SEPMs) are often used in conservation planning. However, confidence intervals around predictions of spatially explicit population models can greatly underestimate model uncertainty. This is partly because some sources of uncertainty are not amenable to the classic methods of uncertainty analysis. Here, we present a method that can be used to include multiple sources of uncertainty into more realistic confidence intervals. To illustrate our approach, we use a case study of the wood thrush (Hylocichla mustelina) in the fragmented forest of the North Carolina Piedmont. We examine 6 important sources of uncertainty in our spatially explicit population model: (1) the habitat map, (2) the dispersal algorithm, (3) clutch size, (4) edge effects, (5) dispersal distance, and (6) the intrinsic variability in our model. We found that uncertainty in the habitat map had the largest effect on model output, but each of the six factors had a significant effect and most had significant interactions with the other factors as well. We also found that our method of incorporating multiple sources of uncertainty created much larger confidence intervals than the projections that incorporated only sources of uncertainty included in most spatially explicit population model predictions.