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Semipalmated sandpiper (Calidris pusilla) migration to the Southern Hemisphere includes a 5‐day non‐stop flight over the Atlantic Ocean, whereas semipalmated plover (Charadrius semipalmatus) migration, to the same area, is largely over land, with stopovers for feeding and rest. We compared the number and 3D morphology of hippocampal astrocytes of Ch. semipalmatus before and after autumnal migration with those of C. pusilla to test the hypothesis that the contrasting migratory flights of these species could differentially shape hippocampal astrocyte number and morphology. We captured individuals from both species in the Bay of Fundy (Canada) and in the coastal region of Bragança (Brazil) and processed their brains for selective GFAP immunolabeling of astrocytes. Hierarchical cluster analysis of astrocyte morphological features distinguished two families of morphological phenotypes, named type I and type II, which were differentially affected after migratory flights. Stereological counts of hippocampal astrocytes demonstrated that the number of astrocytes decreased significantly in C. pusilla, but did not change in Ch. semipalmatus. In addition, C. pusilla and Ch. semipalmatus hippocampal astrocyte morphological features were differentially affected after autumnal migration. We evaluated whether astrocyte morphometric variables were influenced by phylogenetic differences between C. pusilla and Ch. semipalmatus, using phylogenetically independent contrast approach, and phylogenetic trees generated by nuclear and mitochondrial markers. Our findings suggest that phylogenetic differences do not explain the results and that contrasting long‐distance migratory flights shape plasticity of type I and type II astrocytes in different ways, which may imply distinct physiological roles for these cells. [ABSTRACT FROM AUTHOR]

Little is known about environmental influences on radial glia-like (RGL) α cells (radial astrocytes) and their relation to neurogenesis. Because radial glia is involved in adult neurogenesis and astrogenesis, we investigated this association in two migratory shorebird species that complete their autumnal migration using contrasting strategies. Before their flights to South America, the birds stop over at the Bay of Fundy in Canada. From there, the semipalmated sandpiper (Calidris pusilla) crosses the Atlantic Ocean in a non-stop 5-day flight, whereas the semipalmated plover (Charadrius semipalmatus) flies primarily overland with stopovers for rest and feeding. From the hierarchical cluster analysis of multimodal morphometric features, followed by the discriminant analysis, the radial astrocytes were classified into two main morphotypes, Type I and Type II. After migration, we detected differential changes in the morphology of these cells that were more intense in Type I than in Type II in both species. We also compared the number of doublecortin (DCX)-immunolabeled neurons with morphometric features of radial glial–like α cells in the hippocampal V region between C. pusilla and C. semipalmatus before and after autumn migration. Compared to migrating birds, the convex hull surface area of radial astrocytes increased significantly in wintering individuals in both C. semipalmatus and C. pusilla. Although to a different extent we found a strong correlation between the increase in the convex hull surface area and the increase in the total number of DCX immunostained neurons in both species. Despite phylogenetic differences, it is of interest to note that the increased morphological complexity of radial astrocytes in C. semipalmatus coincides with the fact that during the migratory process over the continent, the visuospatial environment changes more intensely than that associated with migration over Atlantic. The migratory flight of the semipalmated plover, with stopovers for feeding and rest, vs. the non-stop flight of the semipalmated sandpiper may differentially affect radial astrocyte morphology and neurogenesis. [ABSTRACT FROM AUTHOR]

Birds rely on consistent patterns of food availability on their breeding grounds to successfully complete their breeding cycle. Due to ongoing warming of the sub-Arctic, there is potential for a mismatch between the peak in available invertebrate biomass and the peak in food demand for shorebird chicks. During the summers of 2010 and 2011, we investigated the relationship between temperature and benthic and terrestrial invertebrate biomass, measured using three sampling techniques in Churchill, Manitoba. We also investigated the relationship between timing of breeding of Semipalmated Plovers (Charadrius semipalmatus) and timing of peaks in invertebrate biomass. In 2011, chick growth rates were also measured to examine whether hatching in synchrony with the peak in invertebrate biomass during the brood rearing period affected growth rates. In 2010, emergent and core invertebrate biomass were negatively related to soil degree days, whereas in 2011, core biomass increased with soil degree days and pitfall biomass increased with air temperature. Total invertebrate biomass (summed over trap types) peaked from 25 to 31 days before the median chick hatch date in 2010 and 10 days after the median chick hatch date in 2011. In 2011 we did not detect any effects of asynchrony on the growth of Semipalmated Plover chicks. These results may indicate that food resources in their environment remain adequate throughout the breeding season, despite inter-annual fluctuations in the timing of invertebrate peaks. [ABSTRACT FROM AUTHOR]

We examined diet of nonbreeding Semipalmated Plovers ( Charadrius semipalmatus Bonaparte, 1825) in the Cumberland Island estuary, Georgia, USA, through fecal sample analysis. We also examined prey size selectivity by Semipalmated Plovers for the most common prey item found in the fecal samples, which are polychaetes in the family Nereidae (= Nereididae). We compared the size distribution of polychaetes in Semipalmated Plover fecal samples from salt marshes and mudflats with the size distribution of polychaetes sampled from the two habitats. Semipalmated Plovers foraging on mudflats had less variable diets than those foraging on salt marshes, although the mean number of prey per Semipalmated Plover fecal sample was similar between the two habitats. Size selectivity by Semipalmated Plovers of nereid (= nereidid) polychaetes varied as a function of habitat, with Semipalmated Plovers eating larger polychaetes in salt marshes than in mudflats, although in both habitats Semipalmated Plovers avoided extremely small and (or) large ones. Semipalmated Plovers took fewer of the available prey groups and were more selective in sizes of the dominant prey group on mudflats, where prey densities were the highest. These observations are consistent with predictions from optimal foraging theory. [ABSTRACT FROM AUTHOR]

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The acquisition of body reserves by migrating shorebirds at specific staging sites is critical for reaching their breeding or wintering grounds. As many North American shorebird populations are declining, major staging sites need to be identified for effective conservation plans. Changes in body mass of Semipalmated Plover ( Charadrius semipalmatus Bonaparte, 1825) and Semipalmated Sandpiper ( Calidris pusilla (L., 1766)) juveniles, as well as length of stay and daily movements by Semipalmated Plover juveniles during fall migration, were studied in the St. Lawrence River Estuary in southern Quebec, Canada. Most juveniles of both species captured early in the migration period weighed less than the estimated mean fat-free mass. Body mass increased steadily in juveniles of both species during staging. Mean body masses of birds captured in our study area were similar to or higher than those of juveniles of both species captured along the North Atlantic coast. Length of stay of radio-tracked Semipalmated Plover juveniles ranged from 2 to 28 days. Body mass at capture and length of stay were negatively associated, suggesting that individuals refuelled before resuming their migration. Overall, these results provide evidence that the St. Lawrence River Estuary is an important staging site for Semipalmated Plover and Semipalmated Sandpiper juveniles. [ABSTRACT FROM AUTHOR]

Sex-related variation in survival is common in birds and, as it influences effective population size and population growth, is important for conservation and species management. Here we assessed incubation behaviour and sex-related survival in a threatened sexually monomorphic shorebird, the St Helena Plover Charadrius sanctaehelenae. Males incubated at night, the period of highest activity of cats, which are likely to be predators of breeding birds. In spite of behavioural differences between the sexes, adult survival was not significantly different between males and females, suggesting that sex-biased behaviour need not lead to sex-related survival, and thus behavioural differences may not impact upon the adult sex ratio. [ABSTRACT FROM AUTHOR]

Using marked individuals, we assessed directional selection and repeatability of nest-site characteristics of Semipalmated Plovers ( Charadrius semipalmatus Bonaparte, 1825) on Akimiski Island, Nunavut, Canada, 2002-2005, to test the hypothesis that long- and short-term selection patterns were in the same direction. Plovers placed nests in microsites (1 m2 scale) with more pebbles and less bare mud and vegetation than what was available in the environment, indicating long-term selection for these features. Linear (directional selection) effects were stronger than quadratic (stabilizing or disruptive) effects in 3 of 4 years and in the analysis of all data. In the combined 4-year sample, significant directional selection occurred in the opposite direction than that present when comparing used and available sites. Birds with more bare mud and vegetation and fewer pebbles at their nest sites were more successful than birds with pebbled nest sites. Repeatability of nest-site preferences was low and nonsignificant. Neither successful nor unsuccessful pairs chose significantly different nest-site characteristics in subsequent nesting attempts, but options for moving to different nest sites may be limited by interannual site fidelity. Wide individual variability and low repeatability of nest-site characteristics suggests behavioral flexibility in the population. Applying quantitative genetic techniques to patterns of habitat selection may allow researchers to predict the degree to which animals can adjust to changing environments. [ABSTRACT FROM AUTHOR]

As a result of monthly sampling surveys for a year in Querétaro reservoirs and adjacent areas of neighboring states, as well as visits to the Sierra de Lobos in Guanajuato, we present new records of waterfowl for the states of Queretaro (Bucephala albeola, Fregata magnificens, Numenius americanus), Hidalgo (Charadrius semipalmatus, Leucophaeus atricilla, Hydroprogne caspia), and Guanajuato (Pelecanus occidentalis). Additionally, we document species with few published records for areas far from the coast in Mexico. These records show that reservoirs of high semiarid areas of Mexico are used by rare species more often than previously considered, and increase to 70 the species that have been observed in the semiarid zone of Querétaro. This confirms the importance of artificial dams and ponds for waterfowl conservation in this region. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigates the mate retention, dispersal, renesting, and apparent survival of the Semipalmated Plover in Akimiski Island, Nanavut, Canada. It reveals that encounters and return rates of adult male plovers were higher compared to those of female plovers, but their apparent survival were the same and renesting was common. It notes that weather differences affect the breeding season duration and seem to have impacts on the intense of social monogamy.

The article presents a study on foraging habitat quality and behavior of Semipalmated Plovers or Charadrius semipalmatus. Non-breeding plovers followed the foraging sites in southeastern Georgia. Invertebrate density and biomass predicted the foraging rates in pecks/minute and densities in birds/hectare of plovers. Birds did not experience intra-specific competition as shown by the absence of effect of density of foraging birds in their foraging rates at mudflats.

The focus of digital photography has moved from documentation to quantitative analysis. To illustrate the potential application of this diagnostic tool to quantify color and shape, we photographed both artificial and natural semipalmated plover (Charadrius semipalmatus) nests to determine what benefits, if any, were derived from egg crypsis (i.e., eggshell color and egg marking shape). This simple and cost-effective method provides precise and repeatable quantification of color and shape that discriminated subtle differences in egg crypsis of artificial and natural nests that were not visible to us. The advantages of digital photography and image-editing software outweigh any shortcomings, as long as standard protocols are followed for capturing and analyzing images. Used with due care, digital photography is useful in studies that need to quickly assign biological traits, such as age and sex, to individuals, and to document temporal change that may occur as a response to management or disturbance. [ABSTRACT FROM AUTHOR]

The Semipalmated Plover (Charadrius semipalmatus), an arctic-nesting migratory shorebird, regularly encounters low temperatures during the breeding season. We measured the basal metabolism of adults during incubation at Churchill, Manitoba, Canada to determine basal metabolic rate (BMR), lower critical temperature (Tlc), total evaporative water loss (TEWL), and dry thermal conductance (Cm). BMR and Tlo were 47.4 kJ day-1 and 23.3°C, respectively, TEWL was 2.5 mL H2O-d, and Cm was 1.13 mW g-1 °C-1. Measured BMR and Tlc were consistent with high values found for other shorebird species breeding in the Arctic, while Cm was 18% higher than predicted from allometric equations. These metabolic data suggest that Semipalmated Plovers are adapted to balance the requirements of incubation against energetic and thermoregulatory demands in the Arctic, especially in harsh early breeding season conditions. [ABSTRACT FROM AUTHOR]