4/7/2022

Whimbrel populations differ in trans-atlantic pathways and cyclone encounters.

2021 Nature Scientific Reports

Watts, Smith, Hines, Duval, Hamilton, Keyes, Paquet, Pririe-Dominix, Rausch, Truitt, Winn and Woodard

ABSTRACT – Each year hundreds of millions of birds cross the Atlantic Ocean during the peak of tropical cyclone activity. The extent and consequences of migrant-storm interactions remain unknown. We tracked whimbrels from two populations (Mackenzie Delta; Hudson Bay) to examine overlap between migration routes and storm activity and both the frequency and consequence of storm encounters. Here we show that Mackenzie Delta and Hudson Bay whimbrels follow diferent routes across the ocean and experience dramatically diferent rates of storm encounters. Mackenzie Delta whimbrels departed North America from Atlantic Canada, made long (x¯ = 5440 ± 120.3 km) nonstop flights far out to sea that took several days (x¯ = 6.1 ± 0.18) to complete and encountered storms during 3 of 22 crossings. Hudson Bay whimbrels departed North America from the south Atlantic Coast, made shorter (x¯ = 3643 ± 196.2 km) nonstop flights across the Caribbean Basin that took less time (x¯ = 4.5 ± 0.29) to complete and encountered storms during 13 of 18 crossings. More than half of Hudson Bay storm encounters resulted in groundings on Caribbean islands. Grounded birds required longer (x¯ = 30.4 ± 5.32 days) to complete trans-Atlantic crossings and three were lost including 2 to hunters and 1 to a predator. One of the Mackenzie Delta whimbrels was lost at sea while crossing the Intertropical Convergence Zone. Whimbrels use two contrasting strategies to cross the Atlantic including (1) a long nonstop fight around the core of storm activity with a low likelihood of encountering storms but no safety net and (2) a shorter fight through the heart of Hurricane Alley with a high likelihood of encountering storms and a safety network of islands to use in the event of an encounter. Demographic consequences of storm encounters will likely play a role in the ongoing evolution of trans-Atlantic migration pathways as global temperatures continue to rise.

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Decline of Eastern Black Rails (Laterallus jamaicensis jamaicensis) within the Chesapeake Bay Region, USA.

2021 Waterbirds

Watts, Brinker, Wilson, Smith and Hines

ABSTRACT – Eastern Black Rails (Laterallus jamaicensis jamaicensis) were surveyed during 1990, 2007, 2014 within the Chesapeake Bay region in Maryland and Virginia, USA. A network of point count locations (n = 182) was established and surveyed within tidal salt marshes. Occupancy declined during the study period from 0.84 ± 0.13 (ψ ± SE) in 1990 to 0.06 ± 0.02 in 2014. The annualized rate of decline was estimated to be 6.5%. Extinction and colonization rates between 1990 and 2014 were 0.81 ± 0.09 and 0.04 ± 0.02 respectively. Abundance declined from 1.98±0.05 Black Rails/point in 1990 to 0.26 ± 0.02 in 2014 with a 3.2% annualized rate of decline. Recruitment was 1.32 ± 1.35 between 1990 and 2007 and 0.003 ± 0.05 between 2007 and 2014. Species detection was negatively influenced by advancing season and waxing moon phase while individual detection was most strongly influenced by survey year and advancing season. Anecdotal observations of range-wide strongholds within the Chesapeake Bay suggest that sites have experienced significant declines with birds being extirpated by 2016. Declines throughout the core breeding area and within individual strongholds in the Chesapeake Bay are consistent with Black Rail declines in tidal habitats throughout the broader Northeast region.

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Influence of introduced peregrine falcons on the distribution of red knots within a spring staging site.  

2021 Plos ONE

Watts and Truitt

ABSTRACT – Predator recovery driven by single-species management approaches may lead to conservation conflicts between recovered predators and prey species of conservation concern. As part of an aggressive recovery plan, the Eastern Peregrine Falcon Recovery Team released (1975–1985) 307 captive-reared peregrine falcons (Falco peregrinus) and successfully established a breeding population within the mid-Atlantic Coastal Plain, a physiographic region with no historic breeding population and a critical spring staging area for migratory shorebirds. We examined the influence of resident falcons on the distribution of foraging red knots during spring migration. We conducted weekly aerial surveys (2006–2009) along the Virginia barrier islands during the spring staging period (25 April– 6 June) to map foraging red knots (Calidris canutus) and evaluated the influence of proximity (0–3, 3–6, >6 km) of beaches to active peregrine falcon nests on knot density (birds/km). Accumulated use of beaches throughout the season by red knots was significantly influenced by proximity of beaches to active falcon nests such that mean density was more than 6 fold higher on beaches that were >6 km compared to beaches that were only 0–3 km from active eyries. Whether or not an eyrie was used in a given year had a significant influence on the use of associated close (0–3 km) beaches. From 6.5 to 64 fold more knots used beaches when associated eyries were not active compared to when they were active depending on the specific site. Historically, red knots and other migratory shorebirds would have enjoyed a peregrine-free zone within this critical staging site. The establishment of a dense breeding population of falcons within the area represents a new hazard for the knot population.

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The costs of using night roosts for migrating whimbrels. 

2021 Journal of Avian Biology

Watts, Smith, Hines, Duval, Hamilton, Keyes, Paquet, Pririe-Dominix, Rausch, Truitt, Winn and Woodard

ABSTRACT – Migrant shorebirds operate within a series of landscapes and must adjust their daily activities to achieve seasonal time and energy objectives. Night roosts are essential landscape elements that provide safety from predators for many shorebird species. What costs migrants incur to use night roosts and how these costs vary across staging sites are poorly understood. We tracked 42 adult whimbrels Numenius phaeopus with satellite transmitters and used night locations to delineate 39 night roosts during spring and fall migration. We used daytime locations to measure round-trip commuting distances between night roosts and foraging areas and estimated daily commuting costs including distance, time and metabolic energy expenditure. We identified night roosts on offshore islands (n=20) and onshore locations including along habitat edges (n=13) and on topographic highs within extensive marshes (n=6). Mean daily commuting costs varied between roosts. Whimbrels took 3.9–52.1 min (median=15.2) to fly 3.1–42.2 km (median=12.3) which costs 6.1–82.4 kj (median=22.3) in lean mass energy expenditure and 8.1–109.2 kj (median=31.5) in leaving mass energy. Birds using offshore roosts had twice the commuting distance and associated costs compared to those using onshore roosts. The contribution of commuting costs to the premigratory energy budget ranged from 1.5 to 18.8% with costs for nearly 30% of roosts exceeding 10%. Commuting costs to and from night roosts appear to be biologically relevant within some staging sites and should be considered among other constraints faced by migrants during stopover periods when food or time is limiting.

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Aggregations of Polistes wasps over-wintering in artificial red-cockaded woodpecker cavities. 

2021 Southeastern Naturalist

Hines and Watts

ABSTRACT – We document blockage of artificial Dryobates borealis (Red-cockaded Woodpecker) cavities by family Sphecidae (mud daubers) and large mixed-species aggregations of wintering Polistes (paper wasps) in cavity inserts at Great Dismal Swamp NWR in southeast Virginia. The large aggregations that we encountered are the only known cases of more than 2 paper wasp species cohabitating. Activity of Red-cockaded Woodpeckers within a cluster lessened the likelihood that paper wasps will aggregate in cavities, but not the likelihood that mud daubers will nest in cavities. The moist and saturated soils that predominate our field site may explain why these insects are more abundant compared to drier, upland habitats. Additionally, removal of hardwood trees may increase the breeding season habitat quality for paper wasps that hunt and nest in areas that are more open, while simultaneously limiting potential winter hibernacula habitat, typically found in mature hardwood tree cavities for Red-cockaded Woodpeckers. Common cavity management and translocation techniques may need to be altered to mitigate greater paper wasp and mud dauber activity at Red-cockaded Woodpecker cavity inserts in Pinus serotina (Pond Pine) pocosin habitat. We suggest using graduated rubber stoppers rather than screens that fail to exclude insect taxa or conducting translocations prior to the formation of winter aggregations of paper wasps.

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The annual cycle for whimbrel populations using the Western Atlantic Flyway

2021 PLoS ONE

Watts, Smith, Hines, Duval, Hamilton, Keyes, Paquet, Pririe-Dominix, Rausch, Truitt, Winn and Woodard

ABSTRACT – Many long-distance migratory birds use habitats that are scattered across continents and confront hazards throughout the annual cycle that may be population-limiting. Identifying where and when populations spend their time is fundamental to effective management. We tracked 34 adult whimbrels (Numenius phaeopus) from two breeding populations (Mackenzie Delta and Hudson Bay) with satellite transmitters to document the structure of their annual cycles. The two populations differed in their use of migratory pathways and their seasonal schedules. Mackenzie Delta whimbrels made long (22,800 km) loop migrations with different autumn and spring routes. Hudson Bay whimbrels made shorter (17,500 km) and more direct migrations along the same route during autumn and spring. The two populations overlap on the winter grounds and within one spring staging area. Mackenzie Delta whimbrels left the breeding ground, arrived on winter grounds, left winter grounds and arrived on spring staging areas earlier compared to whimbrels from Hudson Bay. For both populations, migration speed was significantly higher during spring compared to autumn migration. Faster migration was achieved by having fewer and shorter stopovers en route. We identified five migratory staging areas including four that were used during autumn and two that were used during spring. Whimbrels tracked for multiple years had high (98%) fidelity to staging areas. We documented dozens of locations where birds stopped for short periods along nearly all migration routes. The consistent use of very few staging areas suggests that these areas are integral to the annual cycle of both populations and have high conservation value.

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Home range of a breeding male bald eagle (Haliaeetus leucocephalus) tracked via satellite telemetry in Kentucky.  

2021 Northeastern Naturalist

Slankard, Patton, Watts

ABSTRACT – Haliaeetus leucocephalus (Bald Eagle) is a well-studied species, and information on their nest abundance and population trends is widely available. However, research on the movements and home range of nesting Bald Eagles in the interior US is lacking. In this study, we used a solar-powered Argos platform transmitter terminal (PTT) with global positioning system (GPS) capabilities to monitor the movements of an adult, breeding male Bald Eagle, captured at Ballard Wildlife Management Area, KY, from 29 April 2012 to 23 October 2013. We generated minimum convex polygons (MCP) for comparisons to previous studies and used 95% and 50% fixed kernel density estimators (KDE) to estimate home-range size and core-use areas, respectively, during nesting and non-nesting periods. Estimates of home range and core-use areas were slightly larger during the non-nesting period (MCP = 420.0 km2 , 95% KDE = 1.6 km2 , 50% KDE = 0.2 km2 ) when compared to the nesting period (nesting MCP=415.0 km2 , 95% KDE =1.3 km2 , 50% KDE = 0.01 km2 ). Our home range and core-use estimates were smaller than previous studies using comparable methods, suggesting that habitat quality at this site may be high.

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Breeding phenology of the Eastern Black Rail (Laterallus jmaicensis).

2021 The Wilson Journal of Ornithology

Watts

ABSTRACT – The Eastern Black Rail (Laterallus jamaicensis jamaicensis) is listed as Threatened under the United States Endangered Species Act and as Endangered in 6 states along the Atlantic Coast. Black Rails are difficult to observe and documentation of definitive breeding evidence is limited. This, along with perceived overlaps between the breeding and migratory periods, has led to uncertainty about the breeding status of calling birds across a large portion of their range. To delineate breeding and migratory periods, I examined the phenology of breeding records (N ¼ 170) and documented ‘‘presumed migrants’’ (N ¼ 55) based on rails that hit radio towers, lighthouses, and buildings or were found in inner cities, on ships-at-sea, or on offshore islands. Nesting in Eastern Black Rails extends 3 months from mid-May to mid-August and peaks during the third week of June. Based on the available sample there is no evidence that egg dates vary with latitude along the Atlantic Coast. Presumed migrants were recorded from early March to early May and from early September to early November. Breeding observations and records of presumed spring migrants overlapped during the first 2 weeks of May. The overlap includes only 2.4% of breeding records. There was no overlap between records of presumed fall migrants and the breeding season.

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Recent advances in Eastern Black Rail (Laterallus jamaicensis jamaicensis) research: An introduction

2021 Waterbirds

Watts and Beisler