The Rusty Blackbird- Recent Research to Fuel Conservation Strategies

Symposium

 

Symposia will be available on-demand on their scheduled date, then again at the conclusion of the conference.

 
The Rusty Blackbird (Euphagus carolinus) is a widespread North American species that has shown chronic long-term and acute short-term population declines, based both on breeding season and wintering surveys. Rusty Blackbirds are ecologically distinct from other blackbirds, depending upon boreal wetlands for breeding and bottomland wooded-wetlands for wintering. This symposium will include presentations on recent Rusty Blackbird research including life cycle modelling, parasites, geospatial tracking and genetics. Research updates will provide segue to a meeting of the International Rusty Blackbird Working Group (IRBWG) after the symposium. The IRBWG meeting will focus on developing a long-term conservation strategy for this species. All are welcome to the symposium and the working group meeting.

 

Bird Blowflies and Rusty Blackbirds: Is There a Climate Change Connection?
Carol R. Foss; Terry L. Whitworth
The Rusty Blackbird has experienced a dramatic population decline accompanied by a range retraction to the north and higher elevations. This phenomenon suggests a climate change connection, but no mechanism has been identified to date. The discovery in 2015 of bird blow fly larvae on Rusty Blackbird nestlings near the southeastern edge of the breeding range has raised the possibility that these parasites might be contributing to the species’ decline. We documented puparia of Protocalliphora shannoni and P. metallica in Rusty Blackbird nests during 2015-2019. Numbers and distribution have varied annually, with proportions of analyzed nests parasitized ranging from 17% (2019) to 79% (2018). Maximum numbers of puparia per nest ranged from 15 (2019) to 77 (2015). We present basic information about bird blow flies and what we have learned about their patterns of occurrence in Rusty Blackbird nests in our northern New England study area.
Molt Ecology of Rusty Blackbird in Southern Yukon
Pam Sinclair
Rusty Blackbird is a Special Concern species in Canada due to population declines. It nests in boreal forest wetlands, and winters in bottomland hardwood forest in the southeastern USA. Rusty Blackbirds typically finish nesting in June, but remain in the boreal region until early October. A complete or near-complete feather-molt occurs from July to September. Studies have used feather samples to investigate migratory connectivity, genetics and toxicology, with the assumption that the feathers were grown on the breeding grounds. Thus the timing of molt and post-fledging movements are important to understand. We captured 904 Rusty Blackbirds between late July and early October 2005-2010 in southern Yukon. Adults were captured from 28 July to 21 September with molt observed from the first capture until 12 September. Juveniles were captured from 15 August to 6 October, with molt observed until 26 September. Adults grew a complete set of flight and body feathers, and hatch-year birds did almost the same, retaining only a few juvenile underwing coverts. Thus hatch-year birds began molting very shortly after completing the growth of their juvenile plumage in July. Most birds were captured at a landfill site, which had a higher proportion of hatch-year birds, and a higher proportion of molting birds, than two sites in natural habitats. Individual birds were re-captured up to 35 days after first capture; birds that had finished molting had gained weight, while most molting birds did not. Birds banded at the Whitehorse landfill were observed in subsequent breeding seasons in nesting habitat 3.5 to 9.5 km away, providing some evidence that molt may occur close to breeding sites. These results point to the importance of late summer/early fall for Rusty Blackbirds, which must find sufficient resources for a complete molt and also attain body condition sufficient for migration to wintering grounds.
Full Annual Cycle Ecology of Rusty Blackbirds Revealed Through Archival GPS Tracking
Jay Wright; Jim Johnson; Erin Bayne; Carol Foss; Luke Powell; Jeremiah Kennedy; Peter Marra
In order to develop effective species recovery plans for declining migratory birds, it is necessary to take a full annual cycle approach. In particular, it is important to know 1) the migratory connectivity of different populations, 2) how much time individuals spend in each phase of the annual cycle, and 3) what habitats individuals are using throughout the year. We used archival GPS tags, recently miniaturized for use on passerines, to answer these questions for three populations of a rapidly declining songbird, the Rusty Blackbird. Between 2015 and 2018, we deployed 30 tags on individuals breeding in Alaska, Alberta, and New Hampshire. We recovered 7 of these tags, which collected between 17 and 194 GPS points over the course of the year. Several of these tags provided daily location data during migration, a level of detail rarely seen for migratory songbirds. Among the three study populations, migratory connectivity was moderate (MC = 0.489), with the Mississippi alluvial valley as an important wintering area for both Alaskan and Albertan birds. Partitioning of the annual cycle between stationary and migratory periods varied between populations, likely due to differences in distance traveled (1,200 km for New Hampshire vs. 5,200 km for Alaska birds), but most birds exhibited extended stopovers (>10 days) during both migrations, as well as multiple wintering sites. Habitat use was primarily tied to emergent and woody wetlands throughout the year, but the relative importance of these habitats varied between annual cycle stages and behavior (roosting vs. foraging).
Carryover Effects of Nesting Diet Composition on Post-Fledging Rusty Blackbird Survivaland Movement
Patricia Wohner; Carol Foss; Robert Cooper
Rusty Blackbirds (Euphagus carolinus) are of conservation concern due to population decline since at least the 1970s. The causes of decline are still unclear. In an effort to understand potential causes of decline, we studied the effects of variation in adult and nestling diet on survival and movement up to 6 weeks post-fledging. We hypothesized that increased proportions of dragonfly larvae in the diet result in nestlings with increased body condition that affects fledgling survival and ability to disperse more quickly to foraging habitat. We conducted our study from May to July during 2009 to 2012 in Northern New Hampshire, Vermont, New Brunswick, and Nova Scotia. We determined proportional diet composition using stable isotope analysis and survival and movement using radio-telemetry. We found Rusty Blackbird adults and nestlings consume a large proportion of adult and larval dragonflies (Odonata spp.) during nesting. In addition, Rusty Blackbirds consume varying proportions of caddisfly (Trichoptera) and mayfly (Ephemeroptera) larvae. Plasma and red blood cell tissues that sample short- and intermediate- term diet (i.e., <3days versus <14 days respectively) indicate that nestlings require increasing proportions of certain food items as they grow and that adults adjust their diet over the same time frame. Variation in nesting diet has repercussions for post-fledging.
Rusty Blackbird Use of Commercial Spruce-Fir Forests of Northern New England
Luke Douglas; Amber Roth; Carol Foss
The Rusty Blackbird (Euphagus carolinus) has experienced a steep population decline since the 1970s, with qualitative accounts suggesting that the species’ numbers have been falling since prior to the 1950s. The reason for this decline is still not fully understood, though recent work suggests that habitat destruction and disturbance in the breeding and wintering ranges is a likely cause. The species is a habitat specialist that relies on spruce-fir stands located near wetlands for breeding in the boreal and Acadian forests of North America. Historically the natural disturbance regime in this region included agents such as beaver and spruce-budworm outbreaks, though over the last century anthropogenic change due to commercial logging has become more commonplace. How Rusty Blackbirds react to intensive commercial forestry practices within their breeding range has yet to be critically assessed. Our research seeks to evaluate Rusty Blackbird nesting and fledgling habitat selection and survival in intensively managed forests in Maine and New Hampshire that contain practices such as clearcutting and pre-commercial thinning. Through the use of radio telemetry, GIS, and habitat measurements, we have begun to describe how the species is using these commercial landscapes. Birds during the 2019 field season were confirmed nesting in wetlands, naturally regenerating stands, and stands that had undergone pre-commercial thinning. A second field season is planned for summer 2021 which will incorporate state LIDAR data to describe habitat characteristics. This research will be used to revise management guidelines for the species.
Genes on the Landscape: Population Genomics of Rusty Blackbirds
Sarah Sonsthagen; Robert Wilson; Luke Powell; Steven Matsuoka; James Johnson; Dean Demarest
Spatial organization of suitable habitat across the landscape plays an important part in how populations maintain genomic (i.e. movement of genes) and landscape (i.e. ability of an individual to move across the landscape) connectivity. Here we analyzed reduced representation genomic (ddRAD) and mitochondrial (mt) DNA sequence data from rusty blackbirds (n=205) sampled across their breeding distribution to assess genomic connectivity and identify markers that may be useful to evaluate migratory connectivity. Spatial genomic structure was analyzed using methods that reflect different temporal scales: 1) principal components analysis to identify major trends in the distribution of genomic variation; 2) maximum likelihood clustering analyses to test for the presence of multiple genomic groupings; 3) shared co-ancestry analyses to assess contemporary relationships; and 4) effective migration surfaces to identify regions that deviate from a null model of isolation by distance. Rusty blackbirds are structured across locales (pairwise mtDNA ФST=-0.046-0.677; ddRAD ФST=0.002-0.082) with strong demographic breaks between eastern (Newfoundland and New England/Canadian Maritimes) and other sites in Canada and Alaska. The following sampled locales clustered together: 1) southcentral and interior Alaska (with subtle structure detected for southcentral sites), 2) central Canada (Alberta and Manitoba), 3) Ontario, 4) New England and Canadian Maritimes, and 5) Newfoundland. We identified loci (n=1880) with elevated levels of genomic structure (ФST>0.1) that will be useful in assigning non-breeding individuals to putative breeding regions to elucidate migratory connectivity. Patterns of genetic structure were concordant across marker types indicating that dispersal tendencies are likely similar between sexes. Observed genomic structure across the breeding distribution indicates that effective dispersal is restricted. Evaluating migratory connectivity will provide insight on whether geographic partitioning in the genomic structure is attributable to behavioral or physical barriers to dispersal, and aid full annual cycle conservation efforts targeting this declining species.
The Coastal Route: Rusty Blackbird Migration East of the Appalachians
Pascal Cote; Camille Begin-Marchand; Francois Gagnon; Carol Foss; Patricia Wohner; Junior A. Tremblay
Migration is the least-studied phase of the life cycle for many songbird species, yet is critical for understanding the full life cycle ecology of declining species. We employed the Motus Wildlife Tracking System, and opportunistically one light GPS logger, to investigate migration patterns of the Rusty Blackbird, a species of conservation concern in the United States and Canada. We deployed nanotags on 65 migrating Rusty Blackbirds at the Observatoire d’oiseaux de Tadoussac (OOT) (Quebec, Canada) during September of 2017 to 2019, one GPS logger on a breeding male in New Hampshire during June 2018, and nanotags on 9 breeding individuals in New England (8 in Coos County, NH and 1 in Oxford County, ME) during June 2019. Motus receiving stations detected migratory movements of 34 of the OOT birds and eight of the NE birds. Of the OOT birds detected in the United States, 9 followed a coastal route for at least part of their migration and 8 followed a more inland route. Three were last detected in New England and 13 in the mid-Atlantic region; one was detected in South Carolina but at no point in between. All but one of the New England birds followed a coastal route. Three were last detected in the mid-Atlantic region and 5 in the southeastern states. We present and discuss migration routes and phenology for the tagged individuals.
A Full-Annual Cycle Model to Understand Factors Limiting Rusty Blackbird Populations in Eastern versus Western Flyways
Clark S. Rushing; Luke L. Powell; Steven M. Matsuoka
The Rusty Blackbird has lost 90% of its global population since 1970 and is projected to lose another 50% in the next 19 years. Since 2005, researchers with the International Rusty Blackbird Working Group (Working Group, rustyblackbird.org) have collaborated on a variety of breeding and wintering studies to understand the species’ resource requirements and limiting factors. This collective effort has filled major information gaps on Rusty Blackbird ecology and natural history requirements; however, identifying the causes of its steep decline has remained elusive. In this study we used an integrated population model (IPM) to (1) assess the past contributions of fecundity and age-specific seasonal survival probabilities to Rusty Blackbird population growth in eastern versus western flyway populations of Rusty Blackbirds and (2) project future patterns in population growth in each flyway over a 20-year period under scenarios of current vital rates and realistic increases in vital rates. We analyzed a combination of breeding and winter data on Rusty Blackbirds collected from standardized surveys of abundance (Breeding Bird Survey and Christmas Bird Count) and demographic studies (mark-resighting, summer and winter telemetry, and nest monitoring) conducted by Working Group members from 2005-2015. We used the IPM to estimate past population growth, vital rates (fecundity, age-specific seasonal survival), and the contributions of vital rates to population growth in western versus eastern flyways, the former linking breeding and wintering data between Alaska and Mississippi, the latter New England and South Carolina/Georgia. We then used the IPM to project future annual population growth over 20 years into the future under scenarios where recent rates of fecundity and age-specific seasonal survival were continued versus proportionally increased in the future. We present our preliminary findings on the key vital rates influencing past declines and the magnitude vital rates must be increased to recover populations.
Rusty Blackbird Population and Habitat in Nova Scotia
Cindy Staicer; Shanni Bale; Charlotte Rigolot; Caleb Gibbons; Thomas Baker
The Rusty Blackbird (RUBL; Euphagus carolinus), listed as Endangered in Nova Scotia, Canada, declined markedly between the 1st (1986-1990) and 2nd (2006-2010) Maritimes Breeding Bird Atlases. This study focused on the Nova Scotia population in subsequent years and habitat use by breeding birds. We conducted surveys across the province and augmented our samples with sightings from other field biologists and birders. Our first objective was to determine the level of persistence of RUBLs at sites where found in the 2nd Atlas and whether this persistence could be explained by habitat change. Approx. half of the sites occupied during the 2nd Atlas were revisited between 2012-2019; RUBLs persisted at only 30% of these sites. We assessed habitat change (mostly through forest harvesting) at the revisited sites at two scales – territory or home range (60 ha, 437 m radius) and landscape (78.5 km2, 5 km radius) – using visual analysis of satellite imagery. The second objective was to identify habitat features important to RUBLs in Nova Scotia. We used the same two scales to compare environmental data in GIS layers at sites (1) where we found RUBLs, (2) where we looked for but did not find them, and (3) at points in a systematic 1×1 km grid across the province. Base layers included wet area mapping, flow accumulation, forest inventory data, and roads. Variables included saturated soils (water table <0.5 m from surface); area of water bodies; stream length; road length; distance to streams, waterbodies and roads; proportion of forest, the different tree species, and cover type; and the mean and standard deviation of canopy closure and tree height. Compared to random sites, RUBL sites had more saturated soil, longer stream length, a higher and more closed second story, more intolerant hardwood cover, and more roads.
FRIDAY 3:00PM – 4:00PM Panel Discussion

 
Organizers: Kate Slankard, Kentucky Department of Fish and Wildlife Resources, Frankfort, KY; Carol Foss, New Hampshire Audubon, Concord, NH
 

Symposium
Location: Virtual Date: October 1, 2020 Time: -