Cheri L. Gratto-Trevor

Range-Wide Piping Plover Survival: Correlated Patterns and Temporal Declines

Abstract Geographically isolated breeding populations of migratory shorebirds may be demographically connected through shared nonbreeding habitats. We used long-term (1998–2008) mark–recapture data on piping plovers (Charadrius melodus) collected from 7 separate studies located throughout North America to conduct a range-wide analysis of after hatch year apparent survival (ΦAHY). Our objectives were to compare concurrent survival estimates from disparate breeding sites and determine whether estimates followed similar trends or were correlated among breeding populations with shared wintering grounds. Average survival estimates were higher for Great Plains populations (range  =  0.69–0.81) than for Great Lakes and Atlantic Coast populations (range  =  0.56–0.71). Linear trend models indicated that apparent survival declined in 4 out of 7 populations, was unchanged in 3, and was generally highest among Great Plains populations. Based on a post hoc analysis, we found evidence of correlated year-to-year fluctuations in annual survival among populations wintering primarily along the southeastern United States Atlantic Coast and Gulf Coast. Our results indicate shared overwintering or stopover sites may influence annual variation in survival among geographically disparate breeding populations. Declines in piping plover survival are a cause for concern, and our results highlight the need for conservation efforts to include habitat used during the migratory and wintering periods.

Subspecies Status and Population Genetic Structure in Piping Plover (Charadrius melodus)

ABSTRACT. Piping Plover (Charadrius melodus) is a migratory shorebird that is listed as endangered in Canada and the U.S. Great Lakes and as threatened throughout the rest of its breeding and winter range. We undertook a comprehensive molecular-genetic investigation to (1) address subspecific taxonomy, (2) characterize population genetic structure, and (3) infer past bottlenecks and demographic processes in this species. Analyses included individuals from 23 U.S. states and Canadian provinces and were based on mitochondrial DNA sequences (580 base pairs, n = 245) and 8 nuclear microsatellite loci (n = 229). Our findings provide support for separate Atlantic and Interior subspecies (C. m. melodus and C. m. circumcinctus, respectively). Birds from the Great Lakes region were allied with the Interior subspecies and should be referred to as C. m. circumcinctus. Population genetic analyses illustrated stronger genetic structure among Atlantic than among Interior birds, which may reflect reduced natal- and breeding-site fidelity of Interior individuals. Furthermore, analyses suggested that Interior birds previously experienced genetic bottlenecks, whereas there was no evidence of such patterns in the Atlantic subspecies. We interpret these results in light of 25 years of range-wide census data. Overall, differences between Interior and Atlantic Piping Plovers may reflect differences in spatiotemporal stability of nesting habitat between regions.

Flooding Affects Dispersal Decisions in Piping Plovers (Charadrius melodus) in Prairie Canada

ABSTRACT. Flooding can cause widespread nest failure and chick mortality in sandbar-and beach-nesting waterbirds, particularly when human activity has either altered natural hydrology or limited available nesting habitat. Such widespread reproductive failure could increase breeding-season dispersal, leading to the abandonment of established nesting sites. We examined how annual movement &psgr; varied by sex, reproductive success, and flooding in three Piping Plover (Charadrius melodus) breeding areas in Saskatchewan during 2002–2009, using a multistate capture-mark-recapture model in Program MARK (n = 782). On average, female Piping Plovers were twice as likely as males to disperse and both sexes were more likely to disperse following years of poor versus moderate reproductive success (minimum to maximum values: &psgr;no-fledglings, 0.0054–0.0998 vs. &psgr;two-fledglings, 0.0017–0.0607). In addition, breeding Piping Plovers exhibited higher dispersal following flood years, even in years of moderate reproductive success (minimum to maximum values: &psgr;males-flood, 0.0025–0.0653 vs. &psgr;males-noflood, 0.0019–0.0399; and &psgr;females-flood, 0.0092–0.1089 vs. &psgr;females-no flood, 0.0070–0.0666). Consecutive floods could force Piping Plovers to nest at artificially high densities in new habitats that may be ill-suited to reproductive success. Given the benefits of site familiarity to reproductive success and survival, we recommend that conservation planning consider dispersal of breeding adults, in addition to nests and chicks, when water levels are managed at nesting locations used by Piping Plovers.

FAT DYNAMICS OF ARCTIC-NESTING SANDPIPERS DURING SPRING IN MID-CONTINENTAL NORTH AMERICA

Abstract We measured fresh body mass, total body fat, and fat-free dry mass (FFDM) of three species of Arctic-nesting calidrid sandpipers (Bairds Sandpiper [Calidris bairdii], hereafter “BASA”; Semipalmated Sandpiper [C. pusilla], hereafter “SESA”; and White-rumped Sandpiper [C. fuscicollis], hereafter “WRSA”) during spring stopovers in the Prairie Pothole Region (PPR) of North Dakota, and evaluated the contribution of stored fat to (1) energy requirements for migration to their Arctic-breeding grounds and (2) nutrient needs for reproduction. All spring migrant WRSA (n = 124) and BASA (n = 111), and all but 2 of 99 SESA we collected were ≥2 years old. Male and female BASA migrated through North Dakota concurrently, male SESA averaged earlier than females, and WRSA males preceded females. Fat indices (ratio of fat to FFDM) of male and female SESA and WRSA averaged approximately twice those of male and female BASA. Total body fat of male and female BASA increased with date in spring 1980, but not in 1981; slopes were similar for both sexes each year. Male and female SESA arrived lean in 1980 and 1981, and total body fat increased with date in both years, with similar slopes for all combinations of sex and year. Male and female WRSA arrived lean in 1980–1981 and 1981, respectively, and total body fat increased with date, whereas females arrived with fat reserves already acquired in 1980. Interspecific and sex differences in migration schedules probably contributed to variation in fat storage patterns by affecting maintenance energy costs and food availability. Estimated flight ranges of BASA suggest that few could have met their energy needs for migration to the breeding grounds exclusively from fat stored by the time of departure from North Dakota. Estimated flight ranges of SESA and WRSA, along with fresh body masses of both species when live-trapped on or near their breeding grounds in northern Canada, suggest that major parts of both populations stored adequate fat by departure from temperate mid-continental North America to meet their energy requirements for migration and part of their nutrient needs for reproduction. Dinámica de la Grasa en Chorlos que Nidifican en el Ártico durante la Primavera en el Área Continental Central de América del Norte

Population genetics and evaluation of genetic evidence for subspecies in the Semipalmated Sandpiper (Calidris pusilla)

Abstract. Semipalmated Sandpipers (Calidris pusilla) are among the most common North American shorebirds. Breeding in Arctic North America, this species displays regional differences in migratory pathways and possesses longitudinal bill length variation. Previous investigations suggested that genetic structure may occur within Semipalmated Sandpipers and that three subspecies corresponding to western, central, and eastern breeding groups exist. In this study, mitochondrial control region sequences and nuclear microsatellite loci were used to analyze DNA of birds (microsatellites: n = 120; mtDNA: n = 114) sampled from seven North American locations. Analyses designed to quantify genetic structure and diversity patterns, evaluate genetic evidence for population size changes, and determine if genetic data support the existence of Semipalmated Sandpiper subspecies were performed. Genetic structure based only on the mtDNA data was observed, whereas the microsatellite loci provided no evidence of genetic differentiation. Differentiation among locations and regions reflected allele frequency differences rather than separate phylogenetic groups, and similar levels of genetic diversity were noted. Combined, the two data sets provided no evidence to support the existence of subspecies and were not useful for determining migratory connectivity between breeding sites and wintering grounds. Birds from western and central groups displayed signatures of population expansions, whereas the eastern group was more consistent with a stable overall population. Results of this analysis suggest that the eastern group was the source of individuals that colonized the central and western regions currently utilized by Semipalmated Sandpipers.

Effects of Extreme Tidal Events on Semipalmated Sandpiper (Calidris pusilla) Migratory Stopover in the Bay of Fundy, Canada

Abstract The objective of this study was to determine the implications of extreme tidal events on duration of stay and behavior of Semipalmated Sandpipers (Calidris pusilla) during migratory stopover in Cobequid Bay, Nova Scotia. This area is part of the Bay of Fundy and experiences the largest tidal range in the world. Radiotelemetry was used to monitor duration of stay of 30 adult and seven juvenile Semipalmated Sandpipers. Adults arriving in Cobequid Bay early in the migration period experienced a greater number of extreme high tides (> 15 m) that submerged preferred roost sites, and stayed on average 8.1 days longer than those that arrived later. Juvenile duration of stay was not significantly different from adults. When tides exceeded 15 m, Semipalmated Sandpipers engaged in over ocean flocking at high tide; however, this behavior was not observed when high tides were 13.6 m or less. These extra flights led to higher energy expenditure by early migrants, requiring an estimated 3.8 to 4.3-day increase in length of stay to reach the same mass as later migrants. In the future, predicted sea level rise could increase the frequency of extreme tidal amplitudes and result in greater energetic costs during Semipalmated Sandpiper stopover.