The coastline of the northern Gulf of Mexico (NGOM) represents important non-breeding habitats for 28 species of migratory shorebirds. As processes of climate change accelerate, these habitats are expected to experience dramatic land loss. In addition, the NGOM has experienced several natural and human mediated disasters over the last decade, including Hurricane Katrina and the Deepwater Horizon Oil spill (DWH). Predicting the impacts of these events requires an understanding of the interactions between shorebirds and their habitats. However, the migration ecology of shorebirds on the NGOM has not been well studied. To better understand the effects of the DWH and the importance of NGOM habitats to the migration ecology of shorebirds I carried out two related studies. First, I investigated the potential for long term, large-scale effects of oil exposure to migratory shorebirds through both a literature review, and by investigating the exposure to DWH oil in seven species of shorebirds that winter or stopover along the NGOM. I found that through migratory carry-over effects, oil spills and other environmental disasters, have the potential to impact ecosystems far from the event. Exposure results suggest as many as 1 million shorebirds were impacted by direct exposure to oil, and many more may have been negatively affected by disturbance from cleanup activities in oiled habitats. Second, I investigated the migration ecology of three near-arctic breeding species of shorebirds (Semipalmated sandpipers (Calidris semipalmatus), Western Sandpiper (C. mauri) and Dunlin (C. alpina), by measuring within- and among-species variation in habitat use, stopover duration, and refueling rates, as measured by plasma metabolites, across 3 habitat types. I found that among species, shorebirds vary in their migration ecology according to the distance to the next stopover site, suggesting NGOM habitats may be particularly important to longer-distance â"u20acœjumpâ"u20acù migrants (Dunlin). I also found that while shorebirds are found across all habitat types sampled, the back bay habitats of barrier islands provided a higher quality habitat (as evidenced by higher prey biomass, and a higher refueling rate) than traditional coastal mudflats or remnant wetlands, highlighting the importance of considering shorebird ecology in barrier island restoration plans. / 1 / Jessica Renee Henkel

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Distributional and ecological dynamics of Neotropical migratory birds at stopover sites where they maintain critical fat reserves during migration remain poorly understood in North American aridlands. I examined spatiotemporal abundance and timing of migrants relative to 1) upland and riparian habitats, 2) post-fire landscape mosaics, and 3) phenological synchrony and overlap of migration with tree flowering in southeastern Arizona's Madrean Archipelago (2009-2011), and 4) abundance, habitat breadth, and foraging substrates relative to tree flowering along the Colorado River in southwestern Arizona and northwestern Sonora, Mexico (2000-2003). I explored these dynamics relative to local weather conditions and El Niño Southern Oscillation (ENSO) climate phenomena. In Madrean habitats, migrants showed three non-exclusive responses to high precipitation, snowfall, and low minimum temperatures associated with El Niño in 2010; migration timing adjustments, habitat shifts, and reduced abundances suggesting migration route shifts. Foliage-gleaning insectivores were most abundant in high severity burns, disproportionate to their availability, and decreased with time since fire (TSF); flycatchers were most abundant in low-moderate severity and increased with TSF. Migrant abundance increased with tree flowering. Phenological overlap declined with increasing difference in timing of these events. Overlap was lowest in 2011 in riparian habitat due to low willow (Salix goodinggii) flowering, despite high migrant abundance, but lowest in 2010 in montane conifer, despite high pollen cone production by Douglas-fir (Pseudotsuga meziesii), suggesting temperature limitation of insect abundance at high elevations, but water limitation of plant phenology at lower elevations. Along the Colorado River, migrant abundance and habitat breadth had inverse positive and negative quadratic relationships, respectively. Abundance increased with tree flowering, but only in 2003 during severe drought. Habitat breadth increased with monsoon precipitation. Foraging substrate use tracked flowering, shifting from willow to mesquite (Prosopis sp.); the overlap coincided with peak abundance and narrowest habitat breadth. Maintenance of diverse vegetation and post-fire landscape mosaics in the Madrean Archipelago should benefit migratory bird diversity. Flowering phenology likely provides large-scale cues of local-scale stopover habitat condition associated with interannual climatic variation. Management and restoration of upland habitats and large riparian woody perennials will be critical for migratory bird conservation in aridlands.

Most migrating songbirds are required to stopover to rest and replenish their fat reserves, and suitable stopover habitat is vitally important to their survival and success securing territories at their breeding and wintering grounds. Identifying and protecting stopover locations and movement corridors is essential to connecting all life stages of these species, yet there remain significant knowledge gaps regarding the utilization of stopover sites and fine-scale movements during migration, particularly at inland stopover areas. We investigated the factors that influence stopover duration and migration rate of ten migratory songbirds within the Silvio O. Conte National Fish and Wildlife Refuge in the Northeastern United States during two fall and spring seasons in 2015 and 2016 at 5 banding sites using automated telemetry. We expected that fat and mass would influence stopover duration and migration rate, in that birds with larger fat stores and greater masses would make shorter stopovers, and migrate faster than leaner birds. We also expected that birds would move faster in spring, and minimize time later in the season, by making shorter stopovers and migrating faster as the season progresses. A lower percentage of our focal species departed the banding sites within 24 hours compared to other studies in coastal and urban sites, indicating that more birds made stopovers. Sixteen percent of birds made prolonged stopovers (> 7 days) in spring, and 38 % in fall, highlighting the importance of the refuge for long term refueling. Spring birds made shorter stopovers, and traveled at faster rates than fall birds, suggesting there is may be more pressure for early arrival at breeding grounds. Spring birds captured with significant fat loads made shorter stopovers, and traveled faster than leaner birds. Spring birds also appeared to employ a time minimization strategy, with birds captured later in the season making shorter stopovers. Migration rate of spring birds decreased with distance from the capture site, indicating many birds needed to make additional stopovers. Fall birds that made longer stopovers migrated at faster rates. Fall birds captured later in the season made longer stopovers, and subsequently traveled at faster rates once they departed to possibly minimize time on migration. Variation in stopover behavior was evident among sites and species and this may suggest habitat or site characteristics that affect their value for migrating birds, which should be taken into consideration when conservation planning or vulnerable species. The extensive use of this inland National fish and wildlife refuge by migratory birds, and the fact that birds are acquiring energy reserves that are facilitating successful migration suggests this region is an important corridor for migrating songbirds.

Social information affects the movement decisions of animals and is often an essential factor in habitat selection. Social information should be especially relevant to long-distance migrating birds that navigate over long distances through unfamiliar habitats to find resources to survive. This information likely varies in both availability and importance at the different spatial scales relevant to migrating birds. Using the common yellowthroat as a case study, I tested whether cues might be available in the songs of locally breeding birds at the continental, within-site, and within-territory scales. At the continental scale, I described the geographic variation in song among genetic groups and subspecies, which may provide useful information for migrants navigating across the continent. I found differences in song structure including the duration of silences between notes, number of notes, and bandwidths which might provide cues. Additionally, bandwidth was related to habitat density. At the within-site scale, I tested whether there is a relationship between song, habitat structure, habitat quality, bird size, and bird quality. I found no evidence that song variation is an available source of information about habitat type or quality to migrants exploring habitat variation at the within-site scale. At the same scale, I tested whether migrating common yellowthroats use the presence of song to find habitat by broadcasting song recordings in suitable and unsuitable habitat patches, but did not lure any migrants. However, when I compared the distance between local singing males and the capture locations of migrant common yellowthroat in a passive mist-netting array to the distances expected by chance, I found that migrants were further away from singing local males than expected, perhaps to avoid costly aggressive interactions. At the within-territory scale, I tested whether a singer's location is predictive of microhabitat structure or food abundance, and whether song rate or duration is predictive of a local male's activities. I found that the location of a singing bird may provide migrants with information about the location of food and structurally denser habitat. Song variation may also predict the likelihood of attack should a migrant intrude in the local male's territory.

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The Piping Plover (Charadrius melodus) is an imperiled shorebird that inhabits sandy beaches along the North American Atlantic Coast. The species' decline has been attributed to habitat loss, disturbance, and predation throughout its range, although most conservation efforts have focused on increasing reproductive output during the breeding season. On the coast of North Carolina, Piping Plovers breed in areas with large amounts of recreational and tourism use. Beach recreation is known to reduce nest success, chick survival, and potentially fitness in other parts of the species' range. To reduce potential negative effects from human activities on breeding Piping Plovers, managers close areas to pedestrian and vehicle access using exclusion buffers delineated by symbolic fencing. However, the reproductive success and population size of Piping Plovers in parts of North Carolina has not appeared to increase as a result of these management strategies, despite the importance of the park and its protections to these birds on their southward migration in the fall. To understand how disturbance and attempts to mitigate it affected plover demography, we examined Piping Plover population dynamics, brood movement, and migration in North Carolina from 2015–2017. We monitored 46 nests and 19 broods, and we used a logistic exposure nest survival model and Cormack-Jolly-Seber model to estimate reproductive success. We uniquely banded 77 adults and 49 chicks to understand annual survival and fidelity rates using a live encounter mark-recapture model. During the pre-fledge period, we observed movements of Piping Plover broods, and we gathered information on their environment that may affect their behavior. We recorded 191 brood locations, collected 132 focal chick behavior samples, and 113 potential disturbance environmental samples. We used multiple linear regression to evaluate several hypotheses regarding daily and hourly brood movement rates. We also conducted 22 migratory surveys after the breeding season in 2016 at an area in Cape Hatteras National Seashore thought to be used by large numbers of south-bound migrating Piping Plovers. We used integrated Jolly-Seber and binomial count models on resighting and count data to estimate stopover superpopulation and stopover duration of migrating birds based on their breeding region of origin. Annual survival of adults from North Carolina (x ̅ = 0.69, SE = 0.07) was not different from another population on Fire Island, New York (x ̅ = 0.73, SE = 0.04), but the North Carolina population annually had low reproductive success, primarily due to low rates of chick survival. As a result, the North Carolina population was predicted to decline during the study period (λ<1 each year). Historically this population has not met the estimated rate of reproductive output needed for a stationary population (1.07 chicks per pair, SE = 0.69); therefore, it is likely the population is sustained by immigration from an unknown source. Daily (x ̅ = 71.5m/24hr) and hourly (x ̅ = 183.3m/hr) brood movements each had considerable variation (Daily: SD = 70.6, range = 0.0–327.2m; Hourly: SD = 262.3, range = 0.2–1450.9m). Chicks did not appear to move in response to the environmental factors we examined. The rate of brood movement suggests regular daylight monitoring is necessary to adequately protect unfledged broods from anthropogenic disturbance under current management methods. We found that 569 Piping Plovers (95% CI: 502–651), nearly 15% of the estimated Atlantic Coast population, stopped at a single area in Cape Hatteras National Seashore, North Carolina during fall migration. Birds stayed an average 4–7 weeks, depending on the breeding region from which they migrated, and they primarily used a relatively new protected area. These findings suggest that North Carolina is an important area for Piping Plover ecology during multiple stages of their annual cycle. / Master of Science / A federally threatened species, the Piping Plover (Charadrius melodus) lives on sandy beaches along the North American Atlantic Coast. On the coast of North Carolina, Piping Plovers breed in areas with large amounts of recreational and tourism use. To reduce potential negative effects on breeding Piping Plovers from human activities, land managers close areas to pedestrian and vehicle access. However, the plover population there has not appeared to grow as a result of these management strategies, but large numbers of migrant Piping Plovers have capitalized on this management. Recent work that hypothesized population dynamics in North Carolina may function differently than other Piping Plover populations, and this study was designed to test that hypothesis. To understand how disturbance, and attempts to mitigate it, affected plover demography, we studied Piping Plover population dynamics, chick movement, and migration in North Carolina from 2015–2017. We monitored breeding efforts of Piping Plovers and used banding techniques to understand survival of chicks and adults. We observed behavior and movements of Piping Plover chicks before they fledged and gathered information on habitat they selected and potential risks that may alter their behavior. We also conducted migratory surveys after the breeding season at an area thought to be used by large numbers of Piping Plovers. Survival of adult plovers from North Carolina was not substantially different from that of plovers from other areas, but the North Carolina population had low reproductive success caused by low chick survival, and we estimated the population was declining. However, historically this population has not had enough breeding success to maintain itself; therefore, it is likely the population relies on plovers that immigrate to North Carolina from elsewhere. Plover brood movement was variable, and did not move in response to several environmental factors. The rate of brood movements we observed suggest regular daylight monitoring is necessary to adequately protect unfledged broods from anthropogenic disturbance and mortality using current management methods. We found that nearly 15% of Atlantic Coast plovers stopped at a single area in Cape Hatteras National Seashore, North Carolina, during fall migration, staying an average 4–7 weeks. These findings suggest that North Carolina is a unique area to Piping Plover ecology during multiple stages of their annual cycle.