Songbird Conservation & Management

Contributed Oral Presentations

Contributed paper sessions will be available on-demand for the duration of the conference, then again at the conclusion of the conference.

 

Post-Fledging Survival, Habitat Associations, and Movements of Gray Vireos in New Mexico
Silas E. Fischer; Kathy Granillo; Henry M. Streby
Most studies of reproductive success and habitat associations of songbirds include only the nesting stage. But information from the post-fledging period, or the stage after young (hereafter, fledglings) leave the nest and prior to migration, can improve our understanding of demography and habitat requirements. Songbird annual population growth (ƛ) may be particularly sensitive to variation in fledgling survival, and fledglings of some species use areas with different habitat characteristics than those used for nesting. We used radio telemetry to study post-fledging survival, habitat associations, and movements of Gray Vireos (Vireo vicinor), a migratory songbird of conservation concern for which few annual cycle data are available. At Sevilleta National Wildlife Refuge (New Mexico) during 2017-2020, we tracked 90 Gray Vireo fledglings and found that 51% survived the monitoring period. We observed the highest mortality during the first few days post-fledging, consistent with other songbird studies. Focusing on predation-related mortalities to assess survival in relation to habitat, daily survival of fledglings was best predicted by and positively associated with age. During the first 12 days post-fledging at the 25-m-radius scale, fledglings used areas higher tree density (15 ± 9%) compared to random points (mean 9 ± 9%), but similar to nesting areas (15 ± 10%). Fledglings used oneseed juniper (Juniperus monosperma) trees during 88% of observations. Minimum daily distance traveled, distance from the nest, and associated variation increased with age, with some fledglings attended to by female parents traveling >2km from nests. Preliminary population models suggest that nest productivity and fledgling survival are sufficient for our study population to be numerically stable. Unless there is a post-fledging habitat component preferred by Gray Vireos and missing from our study area, results indicate that conserving large areas of nesting habitat may be sufficient for providing full breeding season habitat for this species.
Breeding Ecology of Blue-Winged Warblers in Managed Shrublands in Southwest Pennsylvania
Kristin Bomboy; Jeffery L. Larkin; Joseph Duchamp; Michael Tyree; Carol I. Bocetti
The Blue-winged Warbler (Vermivora cyanoptera) is a shrubland songbird experiencing annual population declines in Pennsylvania, and loss of early successional breeding habitat is thought to be contributing to their decline. Several studies have provided insight about breeding habitat characteristics for the closely related and more imperiled Golden-winged Warbler (Vermivora chrysoptera), however, few studies have examined breeding habitat characteristics of Blue-winged Warblers, and none have used radio telemetry to do so. We studied the breeding ecology of Blue-winged Warblers occupying managed shrublands in southwest Pennsylvania. We captured and attached radio-transmitters to adult males in early May and monitored their movements throughout the breeding season, then sampled vegetation within each male’s home range (95% KDE) and core territory (50% KDE). On average, Blue-winged Warbler home ranges (11.8 ± 5.3 ha) were 4.5 times larger than core territories (2.6 ± 1.3 ha). Core territories were primarily comprised of shrublands and early-successional forest, while home ranges were comprised of a mix of shrublands and early-, mid- and late-successional forest. Home ranges had less grass and goldenrod (Solidago spp.) cover than core territories. Furthermore, an average of 20.7% of observed locations fell within forested areas and average distance to an open area was 36 m. These results suggest that Blue-winged Warblers use a greater diversity of cover types during the breeding season than previously described. Similar to Golden-winged Warbler breeding habitat recommendations, managers should create a mosaic of shrublands and multi-aged forest to meet the breeding season needs of Blue-winged Warblers.
Variation in Space Use and Exposure to Potential Risk Factors during Migration Are Not Associated with Vermivora Warbler Population Trends
Gunnar R. Kramer; David E. Andersen; David A. Buehler; Petra B. Wood; Sean M. Peterson; Justin A. Lehman; Kyle R. Aldinger; Lesley P. Bulluck; Sergio Harding; John A. Jones; John P. Loegering; Curtis Smalling; Rachel Vallender; Henry Streby
Golden-winged Warblers (Vermivora chyrsoptera) and Blue-winged Warblers (V. cyanoptera) are Neotropical-Nearctic migrants experiencing varied regional population trends that have recently been linked to strong migratory connectivity and historical forest loss at population-specific nonbreeding areas. Preliminary evidence also suggests populations of Vermivora warblers may exhibit variation in space use during migration potentially leading to differential exposure to factors that influence mortality risk. Whether these factors experienced during migration are driving population trends of Vermivora warblers is unknown. We used geolocator data from 90 individual Vermivora warblers tracked during 2013-2017 to investigate whether variation in exposure to a suite of anthropogenic and natural risk factors was associated with recent breeding population trends. Overall, Vermivora warblers exhibited population-specific space use during migration and these differences were associated with variation in exposure to anthropogenic and natural risk factors. However, none of these risk factors helped explain additional variation in population trends after accounting for migratory connectivity (i.e., breeding and nonbreeding region). Our results suggest that factors experienced during migration are unlikely to be driving regional variation in recent Vermivora warbler population trends. We did find, however, that regional differences in projected changes in land use may differentially affect populations of Vermivora warblers during migration in the future. Maintaining suitable stopover habitat is critical for the successful conservation of migratory species, but our results suggest that factors experienced along migration routes are not currently limiting populations of Vermivora warblers.
Insights into Detection and Habitat Use of Black- and Yellow-Billed Cuckoos, Two Declining and Poorly Understood Species
Claire Johnson; Thomas J. Benson
Black-billed Cuckoos (Coccyzus erythropthalmus) and Yellow-billed Cuckoos (Coccyzus americanus) have experienced extensive range-wide population declines over the last several decades. However, as cuckoos are patchily distributed and hard to detect, population size and trend estimates are not well supported and habitat requirements are poorly understood. We set out to examine habitat use and detection probability for both species. We performed passive and call-broadcast surveys for cuckoos at 41 sites in northeastern Illinois and used radio telemetry to track Black-billed Cuckoos at a subset of sites. We examined the influence of habitat covariates on occupancy and the effect of call-broadcast and temporal and environmental covariates on detection probability. Each species was detected at > 50% of sites, and while sites were more likely to have both species than expected by chance, each appeared to use different areas within these sites. However, vegetation structure and composition did not consistently predict habitat use within and among sites for either species. Detection probability was increased substantially (up to 2.6 and 11 times for Yellow-billed and Black-billed Cuckoos, respectively) by using call-broadcasts, but varied throughout the breeding season and between species. Black-billed Cuckoos ranged widely within sites, and home range size varied among individuals. Our results suggest call-broadcasts are essential for understanding distribution and population trends. Unfortunately, the fact that broadcast surveys attracted cuckoos to a survey point, coupled with low detection probability and potentially large home ranges, may have obscured relationships between habitat covariates and use. Site-level variables and characteristics at actual use points may be more important for determining selection within and among sites. Improving our understanding of detection and habitat selection is an important step towards effective management for these two declining species.
Bird Banding Records Demonstrate That Some Northern Cardinals Disperse Long Distances
Daniel Shustack
Dispersal is an important ecological process that has implications for range expansion, gene flow and metapopulation dynamics. While there are a variety of methods for studying avian dispersal, banding and subsequent encounters of those marked birds provide information on dispersal rates and distances. I reviewed the BBL encounter records of the Northern Cardinal (Cardinalis cardinalis) in order to describe their dispersal patterns. Of the 11,640 encounters of banded Cardinals in the database, 2887 were appropriate for analysis because they represent random recoveries of dead cardinals as opposed to encounters from targeted research activities. Most cardinals remain within the 10-minute banding block in which they were banded, however, 21.9% were encountered at least one block away. The precision of banding and encounter locations limit fine-scale examination of dispersal distance, but young cardinals were slightly more likely to display natal dispersal (0.27 moved from their natal banding block) than adults were to display breeding dispersal (0.21 moved from their banding block). Most cardinals do not disperse very far; 95.4% of all cardinals were encountered within 25 km of their banding location. Natal dispersal distances averaged slightly larger than breeding dispersal distances. Only 2% of encounters were from cardinals encountered more than 100 km from the banding location. The longest cardinal movement in the BBL records is an individual (unknown sex and age) which moved 1800 km northward over 23 months. These long-distance movements appear to be exceptional and cardinals display a strong tendency to remain near their banding locations throughout their lives.
Predation Threat in a Variable Landscape: Connecting Predation Risk to Nesting Success for the Seaside Sparrow
Corina Diana Newsome; Elizabeth Hunter
Birds inhabiting Atlantic coastal marshes are experiencing significant and rapid changes to their habitat, specifically in the form of sea level rise and encroaching urbanization. In seaside sparrows (Ammospiza maritima; SESP), sea level rise presents an inherent threat to nest success in its potential to cause nest flooding. In addition to this direct threat, the ability for SESP to adaptively respond to sea level rise can be constrained by predation pressure. As SESP elevate their nests to avoid flooding, their nests become more vulnerable to predation. This research aims to understand the predictability of SESP nest predation threat in Georgia’s saltmarshes along two major gradients: distance to roads and distance to main rivers (rivers ≥150ft in width). First, using two focal sites in coastal Georgia, USA, we assessed mammalian predator occurrence along the two gradients of interest; we hypothesized that predator occurrence would increase with increasing closeness to roads and closeness to main rivers. Second, we recorded the occurrence of SESP nest predation events in the areas assessed for predator occurrence; we hypothesized that nest predation events would increase with increasing probability of predator occurrence. The pattern of mammalian predator occurrence supported our hypotheses along both gradients; however, SESP nest predation did not track mammalian predator distribution. Understanding the predictability of nest predation threat across SESP breeding habitat equips us with valuable information that could be used to address this major constraint to their ability to survive as sea level rise intensifies.
Long-Distance Natal Dispersal as a Resource Tracking Mechanism in Black-Backed Woodpeckers
Andrew Stillman; Teresa Lorenz; Philip Fischer; Rodney Siegel; Robert Wilkerson; Matthew Johnson; Morgan Tingley
Black-backed woodpeckers (Picoides arcticus) are strongly associated with recently burned forests in western North America where they specialize on resources present in dead and dying trees. However, the ephemeral and unpredictable occurrence of burned forests poses an intriguing puzzle for specialized species: how do individuals track the location of these resource patches and colonize newly burned forests? We used a combination of ground-based and aerial telemetry to track the natal dispersal movements of black-backed woodpeckers originating in burned forests of California and Washington. We built a bias-corrected dispersal kernel for the species and designed a novel Bayesian model to examine the factors that influence dispersal probability while accounting for imperfect detection. The bias-corrected median dispersal distance was 18.4 km with a maximum recorded distance of 51 km. Juveniles from older burned forests, where resources are increasingly scarce, dispersed longer distances and were more likely to leave their natal fire compared to juveniles from newer burns. Simulation analyses demonstrated that black-backed woodpeckers select for burned forests relative to available habitat while dispersing across the landscape. Our results provide strong support for the hypothesis that black-backed woodpeckers track resource pulses across fire-prone landscapes, with long-distance natal dispersal acting as a mechanism for rapid post-fire colonization of newly burned areas. These findings also highlight the management importance of wildland fires, and the resource-dense snag patches they create, to the persistence of this species in coniferous forests of the Western U.S.
Priority Birds in The New Jersey Pine Barrens
Phillip Coppola; Chris Williams
The New Jersey Pine Barrens (NJPB) are a fire-mediated ecosystem in a deteriorated state (dense understory and closed canopy) due to a long-standing philosophy of fire suppression and dormant season burning. In recent years, small-scale open forest management (e.g., thinning, clear-cutting, and burning) has occurred within the NJPB; however, the impact of such management on wildlife is unclear. During 2012, 2013, 2016, and 2017, we conducted repeated-visit point counts (n = 1,800) for breeding birds across 75 control and 75 treatment sites within the NJPB to assess the influence of forest structure at three strata levels (groundcover, midstory, and canopy) on breeding bird communities. We constructed a hierarchical community abundance model for Bird Conservation Region (BCR) 30 priority upland birds within three species suites: Forested Upland, Scrub-Shrub/Early Successional, and Grassland. At the overall community level, we found a negative relationship between bird abundance and live tree basal area (βbasal = −0.23, 95% CrI = [−0.40, −0.09]). At the BCR 30 suite level, we found no relationship between Forested Upland species abundance and any of the measured covariates; however, we found a negative relationship between percentage of woody groundcover and Scrub-Shrub/Early Successional suite-level abundance (βwoody = −0.21, 95% CrI = [−0.43, −0.01]), and negative relationship between horizontal visual obstruction at 2 m above ground level and Grassland suite-level abundance (βVOR2 = −0.12, 95% CrI = [−0.24, 0.00]). Furthermore, the two latter species suites exhibited a strong negative relationship with basal area (βbasal = −0.26, 95% CrI = [−0.51, −0.06]) and (βbasal = −0.37, 95% CrI = [−0.66, −0.13], respectively). We recommend open forest management that targets basal areas between ~0-15 m2/ha via selective thinning, shelter cutting, and small-scale clear cutting. Prescribed burning would maintain such conditions and have the added benefit of reducing fuel loads across this ~4,500 km2 landscape.

 

Contributed Oral Presentations
Location: Virtual Date: Time: -