Geothlypis Trichas Research Articles

Bird Species Use of Bioenergy Croplands in Illinois, USA—Can Advanced Switchgrass Cultivars Provide Suitable Habitats for Breeding Grassland Birds?

Grassland birds have sustained significant population declines in the United States through habitat loss, and replacing lost grasslands with bioenergy production areas could benefit these species and the ecological services they provide. Point count surveys and autonomous acoustic monitoring were used at two field sites in Illinois, USA, to determine if an advanced switchgrass cultivar that is being used for bioenergy feedstock production could provide suitable habitats for grassland and other bird species. At the Brighton site, the bird use of switchgrass plots was compared to that of corn plots during the breeding seasons of 2020–2022. At the Urbana site, the bird use of restored prairie, switchgrass, and Miscanthus × giganteus was studied in the 2022 breeding season. At Brighton, Common Yellowthroat, Dickcissel, Grasshopper Sparrow, and Sedge Wren occurred on switchgrass plots more often than on corn; Common Yellowthroat and Dickcissel increased on experimental plots as the perennial switchgrass increased in height and density over the study period; and the other two species declined over the same period. At Urbana, Dickcissel was most frequent in prairie and switchgrass; Common Yellowthroat was most frequent in miscanthus and switchgrass. These findings suggest that advanced switchgrass cultivars could provide suitable habitats for grassland birds, replace lost habitats, and contribute to the recovery of these vulnerable species.

Bird‐habitat associations and local‐scale vegetation structure in lowland brushlands

AbstractBrushlands support a diverse suite of bird species, including species of conservation concern in the western Great Lakes region of central North America. Information on how to effectively manage lowland brushlands for birds and associations between breeding birds and local‐scale vegetation structure and composition is lacking. We surveyed lowland brushlands from 2016–2018 in Minnesota, USA, to assess bird‐habitat associations using avian point‐count surveys and fixed‐radius vegetation plots. We used Poisson regression models to assess the associations between breeding bird species richness, total abundance, and abundance of frequently detected species (using counts as an index for abundance) to woody stem density and height, patchiness of woody stem density, variation of woody stem height, and number of woody plant species. Sedge wrens (Cistothorus stellaris), the most abundant species, were negatively associated with multiple woody plant metrics and positively associated with patchiness. Common yellowthroats (Geothlypis trichas) were the second‐most abundant species and associated with low‐stature woody plants (<1 m based on average heights in study sites). Bird species richness, alder flycatchers (Empidonax alnorum), chestnut‐sided warblers (Setophaga pensylvanica), swamp sparrows (Melospiza georgiana), veeries (Catharus fuscescens), and yellow warblers (Setophaga petechia) increased with woody vegetation height. Chestnut‐sided warbler and Nashville warbler (Leiothlypis ruficapilla) abundances also increased with woody stem density. We suggest that managing lowland brushlands to promote diverse woody plant structure, including tall shrubs and areas with patchy, open herbaceous cover, by implementing temporally and spatially variable disturbance regimes, may benefit bird species that rely on lowland brushlands with a range of vegetation structure requirements.

Three grassland bird species’ responses to fire and habitat structure in southern Illinois, USA suggest broad benefits of grassland size and plant diversity

Grassland birds are the most rapidly declining bird guild in North America, largely due to extensive habitat loss and fragmentation. Because many grassland bird species have different habitat preferences, managing grasslands to provide habitat for a range of species can be a challenge. We used four years of data from southern Illinois, USA grasslands to estimate the influence of prescribed fire and habitat structure on nest survival, nest density, and abundance of three grassland bird species with different habitat preferences: Dickcissel (<em>Spiza americana</em>), Field Sparrow (<em>Spizella pusilla</em>), and Common Yellowthroat (<em>Geothlypis trichas</em>). We found that Dickcissels exhibited the strongest response to prescribed fire, as nest density and nest survival both increased after previously undisturbed grasslands were burned. Fire may have also benefitted Common Yellowthroats and Field Sparrows by reducing woody cover and increasing bare ground, both of which were characteristics associated with nest survival for these birds. Dickcissel abundance was positively related to plant diversity within a grassland and agriculture in the surrounding landscape (within 400 m of a grassland patch), and negatively related to edge-interior ratio. Field Sparrows demonstrated a positive association with woody cover and proximity to forests. Common Yellowthroats were associated with tall vegetation and agriculture in the surrounding landscape. Both Field Sparrows and Common Yellowthroats associated positively with habitat characteristics that reduced nest survival, suggesting potential adaptive mismatches. Our results suggest that periodic prescribed fire, increased plant diversity, and larger patch size may simultaneously benefit a broad variety of grassland bird species with different habitat preferences.

Habitat associations and conservation opportunities for priority birds on small, diversified farms in the northeastern USA

Abstract Although the impacts of intensive agriculture on biodiversity and strategies for mitigating these effects have been widely described, small-scale, diversified farms and the opportunities they present for bird conservation have been less thoroughly examined. This omission is potentially significant, because this form of agriculture represents a growing sector of the industry in the populous northeastern USA, and the diverse habitats on these farms contrast with larger, structurally homogeneous intensive agriculture. To evaluate bird-habitat associations and conservation opportunities for supporting species of conservation concern on these small, diversified farms, we conducted avian point count and vegetation surveys across 23 farms in western Massachusetts during the summers of 2017 and 2018. We used Poisson-binomial mixture models and canonical correspondence analysis to assess the effects of a suite of microhabitat-, field- and landscape-scale (1 km buffer around the field) variables on the abundance of bird species. Our results confirmed that shrubland birds, a group of species of elevated conservation concern, accounted for 52% of the total observations, including song sparrow (Melospiza melodia), gray catbird (Dumatella carolinensis), common yellowthroat (Geothlypis trichas) and American goldfinch (Spinus tristis). Species–habitat relationships were diverse; however, smaller field sizes, and increased cover of tall, dense, woody or non-productive vegetation types were associated with higher abundance of shrubland species as well as lower abundance of crop pests such as European starling (Sturnus vulgaris) and house sparrow (Passer domesticus). These findings support the hypothesis that small, diversified farms are supporting birds of high conservation concern, and we provide species-specific guidelines for farmers interested in conserving birds on their land.

Effects of Non-Native Shrubs on Caterpillars and Shrubland-Dependent Passerines within Three Transmission Line Rights-of-Way in Southeastern New Hampshire

Caterpillars (Lepidoptera, Hymenoptera: Symphyta) are a critical food that breeding passerines use for raising young and serve as an important source of carotenoids that support nestling growth and feather pigmentation. When non-native, invasive plants grow abundant enough to reduce native plant diversity they can cause a reduction in caterpillar abundance. The goal of this study was to determine whether a reduction in caterpillars caused by non-native, invasive shrubs affects nestling health and/or the reproductive success of a shrubland-dependent passerine, Geothlypis trichas trichas (Common Yellowthroat). I first quantified caterpillar abundance on the dominant native and nonnative shrubs comprising Common Yellowthroat territories in shrubby transmission-line rights-of-way and estimated total caterpillar abundance in each territory based on the shrub species composition. I then determined if differences in shrub species composition and caterpillar abundance affected: (1) adult Common Yellowthroat reproductive success, (2) nestling Common Yellowthroat diet composition, or (3) nestling Common Yellowthroat growth rate, plasma carotenoids, and carotenoid-based plumage color. Nonnative, invasive shrubs did not reduce caterpillar abundance until they comprised ≥55% of the shrub volume and significantly reduced the diversity and abundance of native shrubs in bird territories. Differences in caterpillar abundance among sites did not result in differences in Common Yellowthroat productivity, but where non-native shrubs comprised ≥55% of the shrub volume, adults increased their frequency of feeding visits to nestlings and fed nestlings the greatest proportion of non-caterpillar prey. Daily surveys of shrubland bird presence/absence at study sites indicated that most shrubland-dependent bird species were absent where non-native shrubs comprised ≥55% of the shrub cover; such conditions likely equated to habitat loss for bird species less able than Common Yellowthroats to adapt to low shrub diversity and low caterpillar abundance.

Molecular parallelism in signaling function across different sexually selected ornaments in a warbler

Extravagant ornaments are thought to signal male quality to females choosing mates, but the evidence linking ornament size to male quality is controversial, particularly in cases in which females prefer different ornaments in different populations. Here, we use whole-genome sequencing and transcriptomics to determine the genetic basis of ornament size in two populations of a widespread warbler, the common yellowthroat (Geothlypis trichas). Within a single subspecies, females in a Wisconsin population prefer males with larger black masks as mates, while females in a New York population prefer males with larger yellow bibs. Despite being produced by different pigments in different patches on the body, the size of the ornament preferred by females in each population was linked to numerous genes that function in many of the same core aspects of male quality (e.g., immunity and oxidative balance). These relationships confirm recent hypotheses linking the signaling function of ornaments to male quality. Furthermore, the parallelism in signaling function provides the flexibility for different types of ornaments to be used as signals of similar aspects of male quality. This could facilitate switches in female preference for different ornaments, a potentially important step in the early stages of divergence among populations.

Factors associated with arrival timing and condition of migrant landbird species in northeastern Pennsylvania

AbstractExtrinsic and intrinsic factors operating during and prior to the passerine spring migratory period have been associated with both migratory timing and condition. Here we take advantage of a long-term data set to answer questions about how extrinsic factors encountered on the wintering grounds (El Niño Southern Oscillation, ENSO) anden route(temperatures south of our study site) along with intrinsic factors (age, sex if possible) influenced both arrival timing and condition at our site in northeastern Pennsylvania. Older birds preceded younger, male Common Yellowthroats (Geothlypis trichas) preceded females and within a year later arriving Gray Cat-birds (Dumetella carolinensis) and Common Yellowthroats were in better condition. We found that Gray Catbirds and Common Yellowthroats migrating during warmer years arrived in better condition. Finally, we found evidence that ENSO, likely via influencing weather and food availability during the winter, was associated with arrival timing in Veery (Catharus fuscescens), Common Yellowthroats and possibly Gray Catbirds. Our results support the hypothesis that events experienced earlier, either between (wintering to migratory periods) or within (earlier vs. later in migration) phases of the avian annual cycle may carry over, influencing fitness later in time or in subsequent phases of the annual cycle.

Species-Specific Responses of Bird Song Output in the Presence of Drones

Drones are now widely used to study wildlife, but their application in the study of bioacoustics is limited. Drones can be used to collect data on bird vocalizations, but an ongoing concern is that noise from drones could change bird vocalization behavior. To test for behavioral impact, we conducted an experiment using 30 sound localization arrays to track the song output of 7 songbird species before, during, and after a 3 min flight of a small quadcopter drone hovering 48 m above ground level. We analyzed 8303 song bouts, of which 2285, from 184 individual birds were within 50 m of the array centers. We used linear mixed effect models to assess whether patterns in bird song output could be attributed to the drone’s presence. We found no evidence of any effect of the drone on five species: American Robin Turdus migratorius, Common Yellowthroat Geothlypis trichas, Field Sparrow Spizella pusilla, Song Sparrow Melospiza melodia, and Indigo Bunting Passerina cyanea. However, we found a substantial decrease in Yellow Warbler Setophaga petechia song detections during the 3 min drone hover; there was an 81% drop in detections in the third minute (Wald test, p &lt; 0.001) compared with before the drone’s introduction. By contrast, the number of singing Northern Cardinal Cardinalis cardinalis increased when the drone was overhead and remained almost five-fold higher for 4 min after the drone departed (p &lt; 0.001). Further, we found an increase in cardinal contact/alarm calls when the drone was overhead, with the elevated calling rate lasting for 2 min after the drone departed (p &lt; 0.001). Our study suggests that the responses of songbirds to drones may be species-specific, an important consideration when proposing the use of drones in avian studies. We note that recent advances in drone technology have resulted in much quieter drones, which makes us hopeful that the impact that we detected could be greatly reduced.

Which Bird Species Groups Use Highway Roadside Verges and Why?

Highway roadside verges (HRV) provide supplemental habitat for birds in intensive agricultural and suburban landscapes where the natural habitats are rapidly disappearing. The purpose of this study was to document the behavior of breeding bird species using the vegetation maintenance units (green shoulders, embankments, ditches, and banks) of HRV in 3 typical rural landscapes of southern Quebec, Canada. We observed the behavior of 722 individuals of 21 bird species. The most abundant ones (especially Sturnus vulgaris [European Starling] and Agelaius phoeniceus [Red-winged Blackbird]) foraged in the green shoulders, while others (such as Melospiza melodia [Song Sparrow], Spinus tristis [American Goldfinch], and Geothlypis trichas [Common Yellowthroat]) travelled or nested in the low vegetation in ditches and on the banks. Omnivorous species forage in the green shoulders and used the banks and ditches mainly for nesting-related behaviors, just like the few insectivorous species observed. The granivorous species were almost absent from studied HRV. Ground-foraging species used the shoulders to feed but nested in ditches and banks. Species foraging in low vegetation foraged mainly on the banks and used the ditches more for travelling. Reducing the mowing frequency of these 2 maintenance units would likely result in an increase in the vegetation cover and would thus provide additional nesting and foraging habitat for the species we recorded, 67% of which show a stable or declining population in North America.

Ecology of Eastern Equine Encephalitis Virus in the Southeastern United States: Incriminating Vector and Host Species Responsible for Virus Amplification, Persistence, and Dispersal.

Eastern equine encephalitis virus (EEEV; family Togaviridae, genus Alphavirus) is a mosquito-borne pathogen found in eastern North America that causes severe disease in humans and horses. The mosquito Culiseta melanura (Coquillett) (Diptera: Culicidae) is the primary enzootic vector of EEEV throughout eastern North America while several mosquito species belonging to diverse genera serve as bridge vectors. The ecology of EEEV differs between northern and southern foci, with respect to phenology of outbreaks, important vertebrate hosts, and bridge vector species. Active transmission is limited to roughly half of the year in northern foci (New York, New Hampshire, Massachusetts, Connecticut), while year-round transmission occurs in the southeastern region (particularly Florida). Multiple phylogenetic analyses indicate that EEEV strains circulating in northern foci are likely transported from southern foci by migrating birds. Bird species that overwinter or migrate through Florida, are bitten by Cs. melanura in late spring, and arrive at northern breeding grounds in May are the most likely candidates to disperse EEEV northward. Available data indicate that common yellowthroat and green heron satisfy these criteria and could serve as virus dispersers. Understanding the factors that drive the phenology of Cs. melanura reproduction in the south and the timing of avian migration from southern foci could provide insight into how confluence of these biological phenomena shapes outbreaks of EEE throughout its range. This information could be used to develop models predicting the likelihood of outbreaks in a given year, allowing vector control districts to more efficiently marshal resources necessary to protect their stakeholders.

Female ornamentation, incubation behavior, and reproductive success in a wild bird

In many species, both males and females possess sexual signals, but most research focuses on understanding signal expression in males. Females are often assumed to possess signals as a non-functional by-product of selection on males, but increasing evidence demonstrates functional explanations for variation in female signals. Theory suggests that—for many bird species—differences in long-term fitness associated with female signaling are more likely to be driven by variation in offspring quality than quantity, but research paradigms developed for studying male signals have primarily focused on counting offspring produced. Here, we tested the hypothesis that female ornamentation reliably signals the ability to incubate effectively. We used temperature loggers placed in the nest of common yellowthroat warblers (Geothlypis trichas) to record incubation behavior across multiple breeding attempts. Incubation bout length and the onset of daily activity were highly variable between females, but repeatable within females across multiple nesting attempts. Females with longer bouts and later onset of activity had higher hatching success. Wing length and plumage coloration were not related to incubation length or onset of activity, but were correlated with the total percentage of time spent on the nest each day. However, there was only a trend for repeatability in percentage of time spent on the nest and this measure was not correlated with any metrics of offspring quality or hatching success that we recorded. Therefore, we did not find any single aspect of incubation behavior that was (i) consistent, (ii) related to nestling quality or success, and (iii) signaled by ornamentation. Our results demonstrate the importance of variation in incubation behavior, but also suggest that ornaments are of limited utility as a signal of incubation ability in this species. Nevertheless, our study highlights the need to explore alternative fitness proxies in order to understand variation in female ornamentation. Choosing a high-quality mate is an important determinant of reproductive success and animals often attend to elaborate ornaments as signals of quality during mate choice. In many species, both males and females have ornaments, but most research has focused on male signals and female mate choice. We found that female incubation behavior is associated with both plumage ornaments and hatching success, but there was no single signal that provided reliable information about the aspects of incubation behavior that were related to reproductive success. Our findings suggest that understanding female ornamentation may depend on considering the specific ways that females contribute to offspring survival.

Differential reliance on aquatic prey subsidies influences mercury exposure in riparian arachnids and songbirds.

Cross‐ecosystem subsidies move substantial amounts of nutrients between ecosystems. Emergent aquatic insects are a particularly important prey source for riparian songbirds but may also move aquatic contaminants, such as mercury (Hg), to riparian food webs. While many studies focus on species that eat primarily emergent aquatic insects, we instead study riparian songbirds with flexible foraging strategies, exploiting both aquatic and terrestrial prey sources. The goal in this study is to trace reliance on aquatic prey sources and correlate it to Hg concentrations in common riparian arachnids (Families Tetragnathidae, Opiliones, and Salticidae) and songbirds (Common Yellowthroat Geothlypis trichas, Spotted Towhee Pipilo maculatus, Swainson's Thrush Catharus ustulatus, Song Sparrow Melospiza melodia, and Yellow Warbler Setophaga petechia). We used stable isotopes of δ13C and δ15N and Bayesian mixing models in MixSIAR to determine the reliance of riparian predators on aquatic prey sources. Using mixed effects models, we found that arachnid families varied in their reliance on aquatic prey sources. While songbird species varied in their reliance on aquatic prey sources, songbirds sampled earlier in the season consistently relied more on aquatic prey sources than those sampled later in the season. For both arachnids and songbirds, we found a positive correlation between the amount of the aquatic prey source in their diet and their Hg concentrations. While the seasonal pulse of aquatic prey to terrestrial ecosystems is an important source of nutrients to riparian species, our results show that aquatic prey sources are linked with higher Hg exposure. For songbirds, reliance on aquatic prey sources early in the breeding season (and subsequent higher Hg exposure) coincides with timing of egg laying and development, both of which may be impacted by Hg exposure.

Biases obscure whether sexes and ages of window-killed fall migrants die in proportion to their frequency in the migrating population

The timing of migratory passage for sexes and ages of birds is difficult to document because migration is spread out over time and space. We compared sex and age ratios from 10 species of birds that were banded in Wisconsin during fall migration to a sample of autumn window-killed birds from Chicago, Illinois. We assumed that these specimens were a random sample of the migrating population because dates of passage in Wisconsin either predate or were coincident with specimens recovered in Chicago. More juveniles than adults collided with windows, which is expected because of the higher number of juveniles in the fall migratory population. For Connecticut Warbler (Oporornis agilis), Dark-eyed Junco (Junco hyemalis), Ovenbird (Seiurus aurocapilla), and White-throated Sparrow (Zonotrichia albicollis), statistically fewer adults collided with windows than expected. It is possible that adults of these species, who have made at least 2 prior successful migratory journeys, might have experienced some degree of learning to avoid windows. For specimen data, ratios of males to females were approximately equal, except for Swamp Sparrow (Melospiza georgiana; 1:0.82). However, banders were unable to determine sex for a high percentage of each species, ranging from 98.5% undetermined sex for Hermit Thrush (Catharus guttatus) to 48% for Common Yellowthroat (Geothlypis trichas). Taken at face value, banding records for Common Yellowthroat, Dark-eyed Junco, and White-throated Sparrow indicated a much higher percentage of males, whereas for Song Sparrow (Melospiza melodia), females were much more common; 6 species showed no apparent difference in sex ratio between the banding and window samples. In species for which banders declined to identify an individual's sex for a high percentage of birds, we questioned whether the identification of sex in the remaining small percentage was accurate. Thus, we considered the alternative possibility that the specimen data were in fact the most appropriate null hypothesis, and if so, it would suggest that banders have misidentified sexes consistently in 4 species, and ages in 7 species.

Stopover ecology of fall migrating landbirds at an inland stopover site in northeastern Pennsylvania dominated by nonnative vegetation

Landbirds are especially vulnerable during migration as they move through novel habitats and encounter enhanced predation risk, unpredictable food resources, enhanced competition, and inclement weather. Further, numerous studies suggest exotic vegetation species have the potential to alter habitat quality, in turn affecting the fitness of migratory birds. The purpose of this study was to evaluate fitness correlates associated with fall migrant use of shrubland habitat dominated by nonnative honeysuckle (Lonicera spp.) in northeastern Pennsylvania. Additionally, we looked for differences in stopover ecology between demographic cohorts (age, and in the case of Common Yellowthroat [Geothlypis trichas], both age and sex). We used estimates of mass change as our primary fitness indicator, assuming that evidence of positive mass change reflects fat deposition and hence indicates quality habitat. Our results suggest that of 7 species, 1 gained mass, 5 neither gained nor lost mass, and 1 lost mass. Further, while we found little evidence of age or sex differences in migratory timing, we did find evidence that older birds gained mass at a higher rate than younger in 2 species and that, while male Common Yellowthroats maintained mass while using our site, females lost mass. We conclude that our exotic-dominated shrubland habitat does not provide high-quality stopover habitat for most species.

Breeding Bird Occurrence Across a Gradient of Graminoid- to Shrub-Dominated Fens and Fire Histories

Population declines of birds affiliated with grasslands and grass-shrub habitats have been identified as a critical conservation concern. The effects of woody encroachment into grassland-dominated systems, which may contribute to species declines, has been examined mainly in upland systems. We examined occurrence of bird species across a gradient of graminoid- to shrub-dominated wetlands in the Upper Peninsula of Michigan and describe the habitat characteristics associated with their probability of occurrence at segment (100 × 100 m) and landscape (200 m buffer) scales. Because fire can suppress woody encroachment, we also examined the role of fire history, extending from 50 y on birds and habitat characteristics. We focused on seven species closely affiliated with grassland and grass-shrub habitats, but also found in wetlands: Sedge Wren (Asio flammeus), LeConte's Sparrow (Ammodramus leconteii), Savannah Sparrow (Passerculus sandwichensis), Bobolink (Dolichonyx oryzivorus), Common Yellowthroat (Geothlypis trichas), Swamp Sparrow (Melospiza georgiana), and Alder Flycatcher (Empidonax alnorum). We used nonparametric, multiplicative regression models to relate habitat variables and fire history to probability of species occurrence. Unlike studies in upland grasslands, none of the top models included measures of litter or graminoid height, and the highest probability of occurrence often was where graminoid cover was at intermediate rather than highest levels. Measures of woody cover or structure were important to all seven species modeled. We observed few clear differences in habitat metrics across fire history categories beyond the first year of burning. Years since last burned was in the best model for four of the seven species, despite high variability of habitat metrics within fire history categories; those species were more likely to occur in segments burned 15–19 y earlier. Infrequent light- to moderate-severity fires in fens had little effect on focal species occurrence beyond the first year after burning and little long-term effect to suppress woody cover.

Pollen analysis as an ecological proxy for the assessment of habitat use of the endangered Black-polled Yellowthroat (Geothlypis speciosa) and sympatric Common Yellowthroat (G. trichas)

Domínguez-Vázquez, G., S. Raygadas, J. L. León-Cortés and A. Pérez-Arteaga. 2021. Pollen analysis as an ecological proxy for the assessment of habitat use of the endangered Black-polled Yellowthroat (Geothlypis speciosa) and sympatric Common Yellowthroat (G. trichas). Avian Conservation and Ecology 16(2):2. https://doi.org/10.5751/ACE-01856-160202

Detection of Babesia odocoilei in Ixodes scapularis Ticks Collected from Songbirds in Ontario and Quebec, Canada.

Songbirds widely disperse ticks that carry a diversity of pathogens, some of which are pathogenic to humans. Among ticks commonly removed from songbirds, the blacklegged tick, Ixodes scapularis, can harbor any combination of nine zoonotic pathogens, including Babesia species. From May through September 2019, a total 157 ticks were collected from 93 songbirds of 29 species in the Canadian provinces of Ontario and Québec. PCR testing for the 18S gene of Babesia species detected Babesia odocoilei in 12.63% of I. scapularis nymphs parasitizing songbirds in Ontario and Québec; none of the relatively small numbers of Ixodes muris, Ixodes brunneus, or Haemaphysalis leporispalustris were PCR-positive. For ticks at each site, the prevalence of B. odocoilei was 16.67% in Ontario and 8.89% and 5.26% in Québec. Of 31 live, engorged I. scapularis larvae and nymphs held to molt, 25 ticks completed the molt; five of these molted ticks were positive for B. odocoilei. PCR-positive ticks were collected from six bird species—namely, Common Yellowthroat, Swainson’s Thrush, Veery, House Wren, Baltimore Oriole, and American Robin. Phylogenetic analysis documented the close relationship of B. odocoilei to Babesia canis canis and Babesia divergens, the latter a known pathogen to humans. For the first time in Canada, we confirm the transstadial passage of B. odocoilei in I. scapularis molting from larvae to nymphs. A novel host record reveals I. scapularis on a Palm Warbler. Our findings show that B. odocoilei is present in all mobile life stages of I. scapularis, and it is widely dispersed by songbirds in Ontario and Québec.

THE IMPORTANCE OF RESTORATION AT AN URBAN RIPARIAN SITE IN SOUTHWESTERN OREGON FOR NON-BREEDING BIRDS

Riparian systems support disproportionately high biodiversity and are critical for avian conservation in the western United States, yet much historic riparian habitat has been lost or degraded. Restoration of riparian vegetation and associated ecological processes is a high priority, and birds can serve as indicators of restoration success. Here, we analyze data from 17 y of constant-effort mist netting at an urban riparian restoration site to examine changes in capture rates from 2001 to 2017. Capture rates of 4 of 17 species commonly using the site during autumn, and 6 of 14 species using the site during winter, increased over time, and more so in the restored area compared to the mature riparian reference area. This suggests that these birds increased use of the restored habitat area as riparian tree and shrub plantings matured. Birds that responded positively to restoration included several species that breed in and are considered indicators of coniferous forest habitats (Purple Finch, Oregon Junco, Hermit Thrush, and Fox Sparrow) that often inhabit riparian areas during the non-breeding season. Species that breed in riparian habitat did not show as consistent or as strong of a non-breeding season response to restoration. Riparian birds associated with open, wet herbaceous vegetation (Common Yellowthroat and Lincoln's Sparrow) declined in the restored area in autumn while maintaining stable capture rates in the reference area. Three species of finch (Spinus spp.) used the restored habitat, and the site as a whole, in far fewer numbers during the autumn dispersal and migration period in the years following restoration, likely owing to invasive teasel removal efforts. Taken together, these results suggest that restoration actions can result in trade-offs that benefit some birds while reducing suitable habitat for others. Birds complete important activities in the autumn and winter, including dispersal, migration stopover, and molt, so restoration work that supports bird populations during the non-breeding season, even at relatively small urban sites, can make important contributions to their conservation. However, managers should consider the goals of restoration actions in the context of species- or guild-specific responses to restoration-associated changes in vegetation structure.

Detection and density of breeding marsh birds in Iowa wetlands.

Accounting for imperfect detection is an important process when obtaining estimates of density or abundance for breeding birds, and this is particularly true when researchers are monitoring birds to assess the success of restored wetlands. Due to the dramatic decline in areal cover and habitat quality, wetland restoration in the Prairie Pothole Region (PPR) is critically important to breeding birds. The Shallow Lakes Restoration Project (SLRP), a partnership between the Iowa Department of Natural Resources and Ducks Unlimited, Inc., aims to restore degraded shallow lakes throughout the Iowa PPR. We conducted unlimited-radius point counts with call-broadcast surveys for breeding marsh birds at 30 shallow lakes in various stages of restoration in 2016 and 2017. Our goals were to assess the impact of covariates on detection probability and estimate density of these species at non-restored, younger (1-5 years since restoration), and older (6-11 years since restoration) restorations. Detection probability ranged between 0.07 ± 0.009 (SE) for Red-winged Blackbird and 0.40 ± 0.09 (SE) for Common Yellowthroat. Percent cattail had a positive quadratic effect on detection probability for four species, with detection decreasing sharply as percent cattail increased and increasing slightly with 100% cattail cover. Wind speed negatively influenced the detection probability of Pied-billed Grebes but had a negative quadratic effect on the detection probability of Marsh Wrens. Both restored shallow lakes had greater densities of breeding Pied-billed Grebes, Marsh Wrens, and Yellow-headed Blackbirds than non-restored shallow lakes, but there was no significant difference between younger and older restorations. Including both habitat and environmental covariates on models for detection probability can improve the precision of estimates for density and should be considered when assessing bird populations pre- and post-restoration of shallow lakes.

Wetland water-management may influence mercury bioaccumulation in songbirds and ducks at a mercury hotspot.

Mercury is a persistent, biomagnifying contaminant that can cause negative behavioral, immunological, and reproductive effects in wildlife and human populations. We examined the role of wetland water-management on mercury bioaccumulation in songbirds and ducks at Kellys Slough National Wildlife Refuge Complex, near Grand Forks, North Dakota USA. We assessed mercury concentrations in blood of wetland-foraging songbirds (80 common yellowthroats [Geothlypis trichas] and 14 Nelson's sparrows [Ammospiza nelsoni]) and eggs of upland-nesting ducks (28 gadwall [Mareca strepera], 19 blue-winged teal [Spatula discors], and 13 northern shoveler [S. clypeta]) across four wetland water-management classifications. Nelson's sparrow blood mercury concentrations were elevated (mean: 1.00 µg/g ww; 95% CL: 0.76-1.31) and similar to those reported 6 years previously. Mercury in songbird blood and duck eggs varied among wetland water-management classifications. Songbirds and ducks had 67% and 49% lower mercury concentrations, respectively, when occupying wetlands that were drawn down with water flow compared to individuals occupying isolated-depressional wetlands with no outflow. Additionally, songbirds within impounded and partially drawn-down wetland units with water flow had mercury concentrations that were 26-28% lower, respectively, than individuals within isolated-depressional wetlands with no outflow. Our results confirm that mercury concentrations in songbirds at Kellys Slough continue to be elevated and suggest that water-management could be an important tool for wetland managers to reduce bioaccumulation of mercury in birds.