Shore & Waterbirds

Contributed Paper
ROOM: HCCC, Room 19
SESSION NUMBER: 35
 

8:10AM Piping Plover Habitat Selection during Different Biological Phases
Samantha G. Robinson; Henrietta A. Bellman; Katie M. Walker; James D. Fraser; Daniel H. Catlin; Sarah M. Karpanty
The piping plover (Charadrius melodus, ‘plover’) is a beach nesting shorebird that breeds from April through September. When plovers first arrive on the breeding grounds they select and defend territories. Then they transition to egg-laying and incubation, followed by tending to precocial broods, and finally returning to a post-nesting stage after nest failure, or after chicks have fledged or died. Since biological requirements and constraints may differ among these periods, we hypothesized that habitat selection might also differ. We compared habitat selection among pre- and post- nesting adults, nesting adults, brood-tending adults, and pre-fledged chicks, and compared important variables among periods. We used variables that addressed access to foraging habitat, predation risk, and flood risk, and compared plover use locations to random locations. Compared to random points, pre- and post-nesting adults selected areas that were less vegetated, at lower elevations, closer to foraging habitats, and farther from development. Adults with nests selected areas that were less vegetated, farther from vegetation and development, and were closer to bayside foraging areas. Adults with broods selected areas farther from development and closer to moist sand. Chicks selected habitats that were farther from vegetation, and were closer to foraging habitats. Habitat selection by pre- and post-nesting adults were consistently different than other biological periods. For example, pre- and post-nesting adults selected habitats 52% and 43% farther from vegetation than nesting adults and chicks respectively, and 78%, 97%, and 112%, closer to bayside foraging habitat than adults with active nests, adults with broods, and chicks, respectively. Due to these differences, we should consider all relevant biological periods when improving or creating plover habitat. Habitat management for nesting plovers should focus on maintaining vegetation-free sand and access to foraging habitat, as variables associated with these factors were influential for most biological periods.
8:30AM Comparing Survival and Population Growth of Two Atlantic Coast Piping Plover Populations
Chelsea Weithman; Samantha Robinson; Kelsi Hunt; Audrey DeRose-Wilson; James Fraser; Sarah Karpanty; Daniel Catlin
Species listed under the U.S. Endangered Species Act are required to meet certain recovery goals for delisting. These goals are developed early and often may need to be updated or refined to be more biologically relevant or realistic as information becomes available. The Atlantic Coast piping plover (Charadrius melodus) has been listed as threatened in the U.S. for more than 30 years but has yet to meet recovery goals for delisting through much of its range. Initial recovery goals included maintaining a reproductive output of 1.5 chicks per pair for 5 years and assumed equal rates of survival for adults throughout the range, but recent results suggest that demographic rates may vary with latitude. We developed demographic and population growth estimates for two breeding subpopulations of piping plovers on Fire Island, New York (Latitude ~40.7°N) and on the Outer Banks of North Carolina (Latitude ~35.3°N) 2013-2017. Breeding success (nest success and pre-fledge chick survival) varied annually but was lower in NC than NY. Average adult true survival in NY (0.73 ± 0.04) was similar to rates reported previously for this species, but average survival in NC was lower (0.65 ± 0.07). Annual post-fledging survival for both sites, however, was higher than had been previously reported for piping plovers (range: 0.42-0.69 for NY; 0.50 and 1.0 for NC). While the estimated reproductive output needed for a stationary population for both sites was similar (1.06 fledged chicks per pair for NY; 1.08 for NC), only the NY population achieved or exceeded these values during our study. Our findings suggest that an understanding of variable subpopulation demographic rates may be essential to developing recovery goals. Moreover, recovery objectives may be achieved faster if management strategies targeted population-specific demographic rates.
8:50AM Taken By Storm: Shifts in Habitat Selection of an Imperiled Shorebird Following a Major Disturbance Event
Katie Walker; James Fraser; Daniel Catlin; Shannon Ritter; Samantha Robinson; Henrietta Bellman; Audrey DeRose-Wilson; Sarah Karpanty; Steven Papa
The intensity of Atlantic Ocean hurricanes is predicted to increase, and, although disturbance is recognized as a fundamental driver of ecological processes, the benefits of hurricanes to ecological systems are seldom acknowledged. In October 2012, Hurricane Sandy overwashed Fire and Westhampton Islands, barrier islands in New York, flattening dunes and burying vegetation. To reduce future overwashing, subsequent engineering attempted to stabilize the islands. The objective of this study was to determine how a threatened shorebird, the piping plover (Charadrius melodus), responded to changes in dry sand habitat that occurred after Hurricane Sandy. We modeled nest-site selection before and after Hurricane Sandy using logistic regression. Prior to the hurricane, piping plovers selected nest-sites far from the ocean and bay and at high elevations. Following the hurricane, piping plovers selected nest-sites predominantly in or near storm overwash habitat, which was near to and had unobstructed access to the ocean and newly-created bayside foraging habitats. Regions overwashed by storms contained the most suitable piping plover habitat across all new habitat types. By 2017, the piping plover population increased 50%, with most pairs nesting in new habitats. We further observed imperiled seabeach amaranth (Amaranthus pumilis), numerous nesting shorebirds and seabirds, and 25 migratory shorebird species in Hurricane Sandy-created suitable habitat, illustrating the importance of natural coastal disturbance for early-successional species. In this study, only 45% of suitable piping plover habitat was protected from recreational use and few piping plovers used unprotected habitats. Thus, our results suggest that the ecological benefits of increased storminess may only persist by coupling coastal stabilization efforts with conservation.
9:10AM Drivers of Migratory Red Knot Presence along Virginia’s Barrier Islands
Erin L. Heller; Sarah M. Karpanty; James D. Fraser; Shannon J. Ritter; Jonathan B. Cohen
Every year during spring migration, thousands of federally threatened migratory red knots (Calidrus canutus rufa) use Virginia’s barrier islands as stopover habitat to regain the fat required to continue flights to breeding grounds. We investigated the effects of prey and other shorebird abundances, human activities, tide, distance to roost, and year on red knot site use from 2007-2017 by collecting sediment core samples containing prey and counting red knots, other shorebirds, and associated factors across 11 barrier islands in Virginia. During peak migration (May 14-28), we estimated that 3600-11900 red knots used the islands each year. Prey distribution was not continuous, but where present, 430-3000 coquina clams (Donax variabilis), 150-56700 blue mussels (Mytilus edulis), and 1200-21000 other prey items (e.g., crustaceans, annelids) were available/m2 shoreline. Red knot abundance varied by island (Kruskal-Wallis, p<0.05) and year (Kruskal-Wallis, p<0.05). Hog and Parramore Islands supported the highest red knot abundances/km; 2012 and 2015 had the highest red knot abundances/Virginia barrier island shoreline. A logistic regression model including blue mussel, coquina clam, crustacean, and other shorebird abundances, distance to roost, and year best explained the variation in red knot presence or absence at a given site (AIC wt = 0.39), followed by a model with coquina clam, crustacean, and other shorebird abundances, distance to roost, and year (AIC wt = 0.23, ΔAIC = 1.10). Over time, red knot foraging sites had more prey than unused sites (Chi-square, p<0.05). Our results suggest that red knots select sites based on prey abundance and that they prefer foraging sites closer to known night roosts. Since the red knot is federally threatened and uses Virginia’s barrier islands during spring stopover, understanding the factors that affect red knot site selection in Virginia is imperative to successful management practices in Virginia and the larger mid-Atlantic stopover.
9:30AM Geographic and Sexual Variations in Spacing Behaviors of American White Pelicans
Ryo Ogawa; Guiming Wang; D. Tommy King; Martha A. Sovada; Fred L. Cunningham
The annual cycle of migratory birds is composed of nesting, wintering, and migratory periods. Such a complicated annual cycle may create spatiotemporal variations in spacing behaviors of migratory birds. We hypothesized that migratory birds would adjust their movement patterns according to the different phases of annual life cycle. Our objective is to determine differences in movement speeds and home ranges of American white pelicans (Pelecanus erythrorhynchos) among seasons, wintering locations, sexes, and years. We attached GPS transmitters to 20 pelicans captured at Chase Lake, North Dakota, and 40 at the wintering grounds of Alabama, Mississippi, and Louisiana from 2002 to 2016. We compared circadian hourly movement distances by seasons (spring migration, nesting, autumn migration, and wintering periods), populations wintering at the Northern and Southern Gulfs of Mexico, and sexes with hourly consecutive GPS location data. We estimated nesting and wintering home ranges using plug-in kernel density estimators and spring and autumn migratory paths using dynamic Brownian bridge movement models. We used linear mixed models to test for differences in home ranges and migratory paths among the seasons, populations, sexes, and years with bird identity as a random effect. During nesting seasons, male pelicans moved faster than females, and had larger home ranges during nesting than wintering seasons. Males wintering at north had larger home ranges and greater movement speeds than at south, which supports McNab’s energy constraint hypothesis. During migratory periods, pelicans moved faster in spring migration than autumn migration, which was especially pronounced in populations wintering at south. Nesting and wintering home ranges and migratory paths became smaller over the period of study years. Our results suggest the spatiotemporal heterogeneity of avian migratory and movement patterns during the annual cycle.

 

Contributed Paper
Location: Huntington Convention Center of Cleveland Date: October 9, 2018 Time: 8:10 am - 9:50 am