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) 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 and assessed the effect of restoration areas on demographic processes during 2013–2018. We also recorded individual locations of adults and pre-fledge chicks to evaluate effects of post-Hurricane Sandy landscape features on resource selection of adults and chicks, and behavior and survival of plover broods. We 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 also evaluated the effects of post-Hurricane Sandy landscape features on resource selection, behavior, and survival of plover broods during 2013–2019.
We observed positive population growth in three of five years and overall growth through the study (λ ̅=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 (λ ̅=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 closer to 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 in the local red fox (Vulpes vulpes) population. If human interventions were reduced or modified in such a way as to create, maintain, and improve habitat, plover populations likely would reach higher numbers, and the potential for achieving recovery goals would be increased. Future restoration areas projects could use Great Gun as a model, although design criteria could be improved to increase access to moist, flat, low energy foraging sites. Efforts to increase immigration of novel breeding adults into the system, primarily by habitat creation or maintenance, are likely to have the greatest local effect on population growth but may not improve regional population persistence if habitat creation is only local. Management to improve reproductive output is likely to have a positive effect on population growth if there is suitable habitat to support recruits and will improve regional population persistence by producing emigrants. When improving or creating plover habitat, managers should consider habitat needs both for 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. / Doctor of Philosophy / 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 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 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 and 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 features on plover chick habitat, foraging, and survival. Plover chicks avoided vegetation, and selected flatter areas, but selected sites closer to development as time since Hurricane Sandy increased. Chicks spent more time foraging in moist substrates, and less time foraging when there were more plovers nesting in a management unit. Chick survival also was lower when more plovers were nesting in a management unit and was greater for earlier hatched broods. Further, chick survival was higher following a sharp decline in the local red fox (Vulpes vulpes) population.
Overall, Hurricane Sandy was a positive force for this local plover population and local efforts to allow hurricane storm surges to modify the island in the future will improve long-term population persistence. Efforts to increase immigration of novel adults into Fire Island and Westhampton Island, primarily by habitat creation or maintenance, are likely to have the greatest local effect on positive population growth. Improving reproductive output is likely to have a positive effect on local and regional population growth, particularly by maintaining a low red fox population, if there is suitable habitat to support recruits. When improving or creating plover habitat, managers should consider habitat needs for plovers across the whole breeding season rather than just nesting. Habitat management should focus on maintaining vegetation-free sand, and access to low-elevation, flat foraging habitat. Habitat creation also may increase habitat amount and therefore local population growth.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/97725 |
| Date | 16 April 2020 |
| Creators | Robinson, Samantha G. |
| Contributors | Fish and Wildlife Conservation, Catlin, Daniel H., Fraser, James D., Prisley, Stephen P., Karpanty, Sarah M. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
Page generated in 0.0031 seconds