{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/139665"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/139665","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"A System-Level Analysis of Migratory Shorebird Habitat Use, Diet, and the Influence of Climate-Driven Ecosystem Change in the Virginia Barrier Islands","abstract":"Migratory shorebirds rely on high-quality coastal staging habitats to refuel during migration, but these sites are threatened by climate change. The Virginia barrier island system supports over 100,000 shorebirds annually, including federally threatened red knots (Calidris canutus rufa) and other state and regional species of conservation concern such as dunlin (Calidris alpina) and semipalmated sandpipers (Calidris pusilla). The goals of my thesis were: 1) to advance understanding of the foraging ecology of these imperiled shorebird species in the understudied mudflat habitats of the coastal lagoon behind the barrier islands, and 2) to examine how a changing climate may impact red knots by altering barrier island habitats and the invertebrate prey that sustain them during migration. I compared habitat use and prey availability across sand, peat, and mudflat substrates during spring migration (May 14 – June 2, 2023 – 2024) and used fecal DNA metabarcoding to examine diet and prey selection on mudflats. Mudflats supported comparable shorebird numbers and invertebrate densities to barrier island sand substrate. The composition of shorebird and invertebrate communities differed across substrates. Dunlin and semipalmated sandpipers primarily used mudflats and consumed mostly crustaceans while red knots primarily foraged on barrier islands, feeding mainly on bivalves. Red knots foraging on mudflats preferred bivalves. Dunlin similarly showed a preference for bivalves but to a lesser extent than red knots. Semipalmated sandpipers exhibited a generalist diet strategy. All species consumed diatoms, providing the first evidence of biofilm grazing in this system. These findings highlight the ecological importance of mudflats in supporting diverse shorebird foraging strategies. To assess how climate-driven ecosystem change influences red knots and their prey, I used piecewise structural equation modeling integrating long-term data from peak spring migration when red knots are most abundant in Virginia (May 21 – 28, 2009 – 2023). I found that red knots were indirectly influenced by climate change via bottom-up effects on invertebrate prey mediated by barrier island morphology. Prey responses were taxon-specific, suggesting future change may alter invertebrate community structure. I then examined how barrier island morphology has changed since long-term red knot monitoring began in 2007. Half of the barrier islands in our study area significantly narrowed in island width or beach width between 2007 and 2023, though a lack of system-level trends in either indicated relative stability for the barrier island system as a whole. However, accelerated geomorphic change and increasing climate variability may alter foraging conditions, with broader implications for red knot population resilience. My research highlights the importance of preserving habitat heterogeneity at coastal staging sites and incorporating climate-driven landscape-scale processes into conservation planning for migratory shorebirds along the U.S. Atlantic flyway.","abstract_html":"Migratory shorebirds rely on high-quality coastal staging habitats to refuel during migration, but these sites are threatened by climate change. The Virginia barrier island system supports over 100,000 shorebirds annually, including federally threatened red knots (Calidris canutus rufa) and other state and regional species of conservation concern such as dunlin (Calidris alpina) and semipalmated sandpipers (Calidris pusilla). The goals of my thesis were: 1) to advance understanding of the foraging ecology of these imperiled shorebird species in the understudied mudflat habitats of the coastal lagoon behind the barrier islands, and 2) to examine how a changing climate may impact red knots by altering barrier island habitats and the invertebrate prey that sustain them during migration. I compared habitat use and prey availability across sand, peat, and mudflat substrates during spring migration (May 14 – June 2, 2023 – 2024) and used fecal DNA metabarcoding to examine diet and prey selection on mudflats. Mudflats supported comparable shorebird numbers and invertebrate densities to barrier island sand substrate. The composition of shorebird and invertebrate communities differed across substrates. Dunlin and semipalmated sandpipers primarily used mudflats and consumed mostly crustaceans while red knots primarily foraged on barrier islands, feeding mainly on bivalves. Red knots foraging on mudflats preferred bivalves. Dunlin similarly showed a preference for bivalves but to a lesser extent than red knots. Semipalmated sandpipers exhibited a generalist diet strategy. All species consumed diatoms, providing the first evidence of biofilm grazing in this system. These findings highlight the ecological importance of mudflats in supporting diverse shorebird foraging strategies. To assess how climate-driven ecosystem change influences red knots and their prey, I used piecewise structural equation modeling integrating long-term data from peak spring migration when red knots are most abundant in Virginia (May 21 – 28, 2009 – 2023). I found that red knots were indirectly influenced by climate change via bottom-up effects on invertebrate prey mediated by barrier island morphology. Prey responses were taxon-specific, suggesting future change may alter invertebrate community structure. I then examined how barrier island morphology has changed since long-term red knot monitoring began in 2007. Half of the barrier islands in our study area significantly narrowed in island width or beach width between 2007 and 2023, though a lack of system-level trends in either indicated relative stability for the barrier island system as a whole. However, accelerated geomorphic change and increasing climate variability may alter foraging conditions, with broader implications for red knot population resilience. My research highlights the importance of preserving habitat heterogeneity at coastal staging sites and incorporating climate-driven landscape-scale processes into conservation planning for migratory shorebirds along the U.S. Atlantic flyway.","abstract_has_math":false,"creators":["Lapenta, Kristy"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Fisheries and Wildlife Science","degree_department":"Fish and Wildlife Conservation","school":null,"contributors":[],"advisors":[],"committee_chairs":["Karpanty, Sarah M."],"committee_members":["Boettcher, Ruth","Hunter, Elizabeth Ann"],"year":2025,"date_issued":"2025-11-17","date_published":"2025-11-17","updated_at":"2026-07-22T22:18:58Z","subjects":["Migratory shorebirds","foraging ecology","fecal DNA metabarcoding","diet","conservation","red knot","climate change","coastal ecosystems"],"languages":["en"],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:44657"],"render_values":[{"text":"vt_gsexam:44657","href":null,"code":true}]}]},"links":{"outbound_url":"https://hdl.handle.net/10919/139665","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Karpanty, Sarah M."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Boettcher, Ruth","Hunter, Elizabeth Ann"]},{"key":"dc:contributor.department","label":"Department","values":["Fish and Wildlife Conservation"]},{"key":"dc:creator","label":"Author","values":["Lapenta, Kristy"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2025-11-18T09:00:10Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2025-11-18T09:00:10Z"]},{"key":"dc:date.issued","label":"Date","values":["2025-11-17"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Fisheries and Wildlife Science"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Migratory shorebirds","foraging ecology","fecal DNA metabarcoding","diet","conservation","red knot","climate change","coastal ecosystems"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:44657"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/10919/139665"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Migratory shorebirds rely on high-quality coastal staging habitats to refuel during migration, but these sites are threatened by climate change. The Virginia barrier island system supports over 100,000 shorebirds annually, including federally threatened red knots (Calidris canutus rufa) and other state and regional species of conservation concern such as dunlin (Calidris alpina) and semipalmated sandpipers (Calidris pusilla). The goals of my thesis were: 1) to advance understanding of the foraging ecology of these imperiled shorebird species in the understudied mudflat habitats of the coastal lagoon behind the barrier islands, and 2) to examine how a changing climate may impact red knots by altering barrier island habitats and the invertebrate prey that sustain them during migration. I compared habitat use and prey availability across sand, peat, and mudflat substrates during spring migration (May 14 – June 2, 2023 – 2024) and used fecal DNA metabarcoding to examine diet and prey selection on mudflats. Mudflats supported comparable shorebird numbers and invertebrate densities to barrier island sand substrate. The composition of shorebird and invertebrate communities differed across substrates. Dunlin and semipalmated sandpipers primarily used mudflats and consumed mostly crustaceans while red knots primarily foraged on barrier islands, feeding mainly on bivalves. Red knots foraging on mudflats preferred bivalves. Dunlin similarly showed a preference for bivalves but to a lesser extent than red knots. Semipalmated sandpipers exhibited a generalist diet strategy. All species consumed diatoms, providing the first evidence of biofilm grazing in this system. These findings highlight the ecological importance of mudflats in supporting diverse shorebird foraging strategies. To assess how climate-driven ecosystem change influences red knots and their prey, I used piecewise structural equation modeling integrating long-term data from peak spring migration when red knots are most abundant in Virginia (May 21 – 28, 2009 – 2023). I found that red knots were indirectly influenced by climate change via bottom-up effects on invertebrate prey mediated by barrier island morphology. Prey responses were taxon-specific, suggesting future change may alter invertebrate community structure. I then examined how barrier island morphology has changed since long-term red knot monitoring began in 2007. Half of the barrier islands in our study area significantly narrowed in island width or beach width between 2007 and 2023, though a lack of system-level trends in either indicated relative stability for the barrier island system as a whole. However, accelerated geomorphic change and increasing climate variability may alter foraging conditions, with broader implications for red knot population resilience. My research highlights the importance of preserving habitat heterogeneity at coastal staging sites and incorporating climate-driven landscape-scale processes into conservation planning for migratory shorebirds along the U.S. Atlantic flyway."]},{"key":"dc:description.abstractgeneral","label":"General Abstract","values":["Migratory shorebirds travel great distances and rely on coastal areas to rest and feed during migration, but these habitats are under increasing pressure from rising sea levels, warming oceans, and stronger storms. The Virginia barrier island system, located along the Eastern Shore of Virginia, is a chain of mostly undeveloped barrier islands that support over 100,000 shorebirds each year. This includes the federally threatened red knot and other declining species such as dunlin and semipalmated sandpipers. I compared shorebird habitat use and food availability on mudflats and barrier islands during spring migration (May 14 – June 2, 2023 – 2024) to understand how important mudflats are for shorebirds. I then collected droppings from red knots, dunlin, and semipalmated sandpipers on mudflats and used DNA analysis to identify their diets. I then studied diet preferences by comparing what they ate to what was available. Mudflats and sandy barrier island habitats had similar numbers of shorebirds and invertebrates, but each shorebird species used each habitat differently. Dunlin and semipalmated sandpipers mostly fed on mudflats, mainly eating crustaceans. Red knots mainly used barrier island habitats, but when they fed on mudflats, they mainly ate bivalves. All species ate biofilm, a paste-like mixture of diatoms and other unicellular algae that grows on mudflats, which is the first evidence of this in Virginia. Red knots and dunlin preferred to eat bivalves, while semipalmated sandpipers showed no preferences. To explore how climate change affects red knots, I analyzed 10 years of spring migration data (May 20 – 28, 2009 – 2023), along with information on prey, barrier island features, sea-level rise, and storms to test how they are connected. I found that sea-level rise and storms affected beach and island width, which altered prey availability and indirectly affected red knots. I also examined how beach and island width have changed from the beginning of long-term red knot monitoring in 2007 to 2023. While half the islands in our study area narrowed over time, the system as a whole did not change in a major way for this measure. However, other research predicts that faster sea-level rise and stronger storms will greatly change barrier islands in the future. Based on our findings, these changes could alter prey communities and indirectly harm red knots. This work shows that protecting many types of coastal habitats is important in Virginia and all along the Atlantic coast, and that the effects of climate change need to be a part of future conservation planning to protect migratory shorebirds."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["ETD"]},{"key":"dc:title","label":"Title","values":["A System-Level Analysis of Migratory Shorebird Habitat Use, Diet, and the Influence of Climate-Driven Ecosystem Change in the Virginia Barrier Islands"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Karpanty, Sarah M."],"dc:contributor.committeemember":["Boettcher, Ruth","Hunter, Elizabeth Ann"],"dc:contributor.department":["Fish and Wildlife Conservation"],"dc:creator":["Lapenta, Kristy"],"dc:date.accessioned":["2025-11-18T09:00:10Z"],"dc:date.available":["2025-11-18T09:00:10Z"],"dc:date.issued":["2025-11-17"],"dc:description.abstract":["Migratory shorebirds rely on high-quality coastal staging habitats to refuel during migration, but these sites are threatened by climate change. The Virginia barrier island system supports over 100,000 shorebirds annually, including federally threatened red knots (Calidris canutus rufa) and other state and regional species of conservation concern such as dunlin (Calidris alpina) and semipalmated sandpipers (Calidris pusilla). The goals of my thesis were: 1) to advance understanding of the foraging ecology of these imperiled shorebird species in the understudied mudflat habitats of the coastal lagoon behind the barrier islands, and 2) to examine how a changing climate may impact red knots by altering barrier island habitats and the invertebrate prey that sustain them during migration. I compared habitat use and prey availability across sand, peat, and mudflat substrates during spring migration (May 14 – June 2, 2023 – 2024) and used fecal DNA metabarcoding to examine diet and prey selection on mudflats. Mudflats supported comparable shorebird numbers and invertebrate densities to barrier island sand substrate. The composition of shorebird and invertebrate communities differed across substrates. Dunlin and semipalmated sandpipers primarily used mudflats and consumed mostly crustaceans while red knots primarily foraged on barrier islands, feeding mainly on bivalves. Red knots foraging on mudflats preferred bivalves. Dunlin similarly showed a preference for bivalves but to a lesser extent than red knots. Semipalmated sandpipers exhibited a generalist diet strategy. All species consumed diatoms, providing the first evidence of biofilm grazing in this system. These findings highlight the ecological importance of mudflats in supporting diverse shorebird foraging strategies. To assess how climate-driven ecosystem change influences red knots and their prey, I used piecewise structural equation modeling integrating long-term data from peak spring migration when red knots are most abundant in Virginia (May 21 – 28, 2009 – 2023). I found that red knots were indirectly influenced by climate change via bottom-up effects on invertebrate prey mediated by barrier island morphology. Prey responses were taxon-specific, suggesting future change may alter invertebrate community structure. I then examined how barrier island morphology has changed since long-term red knot monitoring began in 2007. Half of the barrier islands in our study area significantly narrowed in island width or beach width between 2007 and 2023, though a lack of system-level trends in either indicated relative stability for the barrier island system as a whole. However, accelerated geomorphic change and increasing climate variability may alter foraging conditions, with broader implications for red knot population resilience. My research highlights the importance of preserving habitat heterogeneity at coastal staging sites and incorporating climate-driven landscape-scale processes into conservation planning for migratory shorebirds along the U.S. Atlantic flyway."],"dc:description.abstractgeneral":["Migratory shorebirds travel great distances and rely on coastal areas to rest and feed during migration, but these habitats are under increasing pressure from rising sea levels, warming oceans, and stronger storms. The Virginia barrier island system, located along the Eastern Shore of Virginia, is a chain of mostly undeveloped barrier islands that support over 100,000 shorebirds each year. This includes the federally threatened red knot and other declining species such as dunlin and semipalmated sandpipers. I compared shorebird habitat use and food availability on mudflats and barrier islands during spring migration (May 14 – June 2, 2023 – 2024) to understand how important mudflats are for shorebirds. I then collected droppings from red knots, dunlin, and semipalmated sandpipers on mudflats and used DNA analysis to identify their diets. I then studied diet preferences by comparing what they ate to what was available. Mudflats and sandy barrier island habitats had similar numbers of shorebirds and invertebrates, but each shorebird species used each habitat differently. Dunlin and semipalmated sandpipers mostly fed on mudflats, mainly eating crustaceans. Red knots mainly used barrier island habitats, but when they fed on mudflats, they mainly ate bivalves. All species ate biofilm, a paste-like mixture of diatoms and other unicellular algae that grows on mudflats, which is the first evidence of this in Virginia. Red knots and dunlin preferred to eat bivalves, while semipalmated sandpipers showed no preferences. To explore how climate change affects red knots, I analyzed 10 years of spring migration data (May 20 – 28, 2009 – 2023), along with information on prey, barrier island features, sea-level rise, and storms to test how they are connected. I found that sea-level rise and storms affected beach and island width, which altered prey availability and indirectly affected red knots. I also examined how beach and island width have changed from the beginning of long-term red knot monitoring in 2007 to 2023. While half the islands in our study area narrowed over time, the system as a whole did not change in a major way for this measure. However, other research predicts that faster sea-level rise and stronger storms will greatly change barrier islands in the future. Based on our findings, these changes could alter prey communities and indirectly harm red knots. This work shows that protecting many types of coastal habitats is important in Virginia and all along the Atlantic coast, and that the effects of climate change need to be a part of future conservation planning to protect migratory shorebirds."],"dc:description.degree":["Master of Science"],"dc:format.medium":["ETD"],"dc:identifier.other":["vt_gsexam:44657"],"dc:identifier.uri":["https://hdl.handle.net/10919/139665"],"dc:language.iso":["en"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["Migratory shorebirds","foraging ecology","fecal DNA metabarcoding","diet","conservation","red knot","climate change","coastal ecosystems"],"dc:title":["A System-Level Analysis of Migratory Shorebird Habitat Use, Diet, and the Influence of Climate-Driven Ecosystem Change in the Virginia Barrier Islands"],"dc:type":["Thesis"],"thesis:degree_discipline":["Fisheries and Wildlife Science"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:18:58Z"}