Piping Plover Habitat and Demography Following Storm-Induced and Engineered Landscape Change Samantha Grace Robinson
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Piping plover habitat and demography following storm-induced and engineered landscape change Samantha Grace Robinson Dissertation submitted to the faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy In Fisheries and Wildlife Conservation James D. Fraser (Co-Chair) Daniel H. Catlin (Co-Chair) Sarah M. Karpanty Stephen P. Prisley March 19, 2020 Blacksburg, Virginia Keywords: behavior, Charadrius melodus, habitat creation, habitat selection, Hurricane Sandy, population dynamics, survival © 2020, Samantha G. Robinson Piping plover habitat and demography following storm-induced and engineered landscape change Samantha Grace Robinson ACADEMIC ABSTRACT Understanding the effects of large-scale disturbances and associated management actions on imperiled species can increase conservation value of future management. Piping plovers (Charadrius melodus; plover) are federally threatened and endangered, disturbance-dependent shorebirds, nesting on broad, sparsely vegetated beaches, sandbars, and lakeshores. In October 2012, Hurricane Sandy storm surges cleared vegetation and opened old and new inlets through Fire Island and Westhampton Island, New York, creating plover habitat. Storm effects prompted an island-wide stabilization project, and certain sections of Fire Island were designed to create and/or improve plover habitat (hereafter, restoration areas) to mitigate possible habitat loss or degradation. Many plover populations range-wide appear to be habitat-limited, and we anticipated positive population growth following habitat creation. To help predict what might happen to the plover population following Hurricane Sandy, we evaluated the effects of habitat-creating events at several other locations in the range, evaluating the hypothesis that plover population sizes are habitat limited. We estimated the amount of habitat available before and after four significant storm and flooding events by classifying pre- and post-disturbance aerial imagery and evaluated the population changes that occurred after disturbance-related habitat alterations. Following these habitat creating events, nesting habitat increased 27%–950%, and, subsequently, these plover populations increased overall 72%–622% (increase of 8–217 pairs in 3 to 8 years after the disturbance, average 12– 116% increase annually). The demographic changes likely were driven by some combination of productivity and immigration occurring simultaneously with regional increases. We then evaluated population and suitable habitat change on Fire Island and Westhampton Island following Hurricane Sandy. We developed an integrated population model to determine the primary contributors to population dynamics and assessed the effect of restoration areas on demographic processes during 2013–2018. We also recorded individual locations of adults (2016–2018) and pre-fledge chicks (2013–2019) to evaluate effects of post- Hurricane Sandy landscape features on resource selection of adults and chicks, and behavior and survival of plover broods. We also evaluated whether breeding stage (pre-breeding, nesting, brooding, post-breeding), simple breeding stage (breeding, not-breeding), or instantaneous behavior class (parental, non-parental) best explained habitat selection during the 5-month plover breeding season. We observed positive population growth in three of five years and overall growth through the study (휆̅=1.12). Immigration and reproductive output were correlated with population growth (r = 0.93 and 0.74, respectively). Compared to the rest of the study area, restoration areas had higher chick survival but lower nest survival and breeding fidelity, and population growth (휆̅=1.09) in restoration areas was similar. For adult plovers, behavior class best explained habitat selection. Compared to non-parental plovers, plovers engaged in parental behavior (incubating, brooding, and accompanying chicks, hereafter ‘parental’) selected areas closer to bay intertidal habitats and with more dry sand. Non-parental plovers avoided areas with more dry sand and did not select for or against bay intertidal habitats. Additionally, non-parental plovers avoided development more than parental plovers and avoided areas of lower elevation more than parental plovers. In each year, there was more suitable habitat for parental plovers than non-parental plovers. Plover broods selected for flatter sites with less vegetation but selected for sites farther from development as time since Hurricane Sandy increased. Chick foraging rates were highest in moist substrates and were negatively influenced by nesting plover density. Chick survival was negatively influenced by nesting plover density and was greater for earlier hatched broods. Further, chick survival was higher following an outbreak of sarcoptic mange that greatly reduced the local red fox (Vulpes vulpes) population. Because immigration and local reproductive output, given fairly constant adult survival, were the primary drivers of population growth on Fire Island and Westhampton Island, efforts to increase immigration of novel breeding adults into the system, primarily by habitat creation or maintenance, are likely to have the greatest effect on local population growth. Maintaining open habitat below the 50% vegetation threshold will preserve habitat suitability and reduce local plover densities which will positively influence habitat for adult plovers throughout the breeding season, in addition to plover chick survival and foraging rates. Reduction of human interventions such as beach stabilization will allow continuous disturbance of habitats, and naturally remove vegetation. However, efforts to increase immigration may not improve regional population persistence if habitat creation is only local, therefore, management to improve reproductive output, which also has a positive effect on population growth but will also benefit regional populations through emigration, is needed. As we found that broods following the outbreak of sarcoptic mange had higher survival to fledge, maintaining the low red fox population will likely improve population growth. Regional habitat enhancement projects, such as restoration area creation, can be used to bolster plover populations and temporarily reduce local plover densities. Future restoration efforts could use the larger restoration area in this study as a model, although design criteria could be improved to increase access to moist, flat, low energy foraging sites and vegetation management will be necessary to maintain vegetation below the suitability threshold. When improving or creating plover habitat, managers should consider habitat needs of plovers of all life stages. Habitat management should focus on maintaining vegetation-free sand and access to low-elevation foraging habitat. Allowing hurricanes such as Hurricane Sandy to alter the landscape naturally will create these landscape features. Piping plover habitat and demography following storm-induced and engineered landscape change Samantha Grace Robinson GENERAL AUDIENCE ABSTRACT Piping plovers (Charadrius melodus) are federally threatened and endangered shorebirds that nest on sandy beaches, sandbars, and lakeshores. In October 2012, Hurricane Sandy created substantial habitat on Fire Island and Westhampton Island, New York, which could have acted as plover habitat. However, concerns about mainland safety from future storms prompted an island- wide project, building dunes planted with beach grass, to improve the ability of Fire Island to protect the mainland. However, planted dunes had the potential to negatively affect newly created habitat, and certain sections of Fire Island were designed to create plover nesting habitat. Because of the natural and engineered habitat creation, we predicted that the population would increase. To illustrate that habitat creating events lead to plover population increases, we used freely available aerial imagery and identified all areas of dry and moist sand in study areas. We then used local plover monitoring data to relate habitat change to plover population change and found that for several hurricanes and floods in the piping plover range, habitat increases led to population increase. We then evaluated population change on Fire Island and Westhampton Island, and found that the population increased 90% following Hurricane Sandy, and the increase was primarily due to new immigrant adults, and local reproductive success. The created restoration areas had similar reproductive output and population growth to the rest of the study area. To determine the areas on Fire Island and Westhampton Island that were adequate habitat for piping plover adults, we compared habitat used by plovers to what was available on the island. Because the plover breeding season is dynamic in that birds move through breeding stages that may have different constraints, and because habitat protections are typically only focused on breeding stages, we evaluated differences in habitat selection by breeding stage and behavior. We determined that habitat use differed between adults exhibiting parental behaviors and adults exhibiting all other behaviors. Non-parental plovers avoided dry sand. Both parental and non-parental plovers avoided development and high elevation sites. Overall, more sand was suitable for parental plovers than non-parental plovers. Because reproductive output also was influential to the population increase on Fire Island, we evaluated effects of landscape