Snowy Plovers (Charadrius nivosus) may be one of the rarest shorebirds in North America yet a comprehensive assessment of their abundance and distribution has not been completed. During 2007 and 2008, 557 discrete wetlands were surveyed and nine additional large wetland complexes sampled in México and the USA. From these surveys, a population of 23,555 (95% CI = 17,299 – 29,859) breeding Snowy Plovers was estimated. Combining the estimate with information from areas not surveyed, the total North American population was assessed at 25,869 (95% CI = 18,917 – 32,173). Approximately 42% of all breeding Snowy Plovers in North America resided at two sites (Great Salt Lake, Utah, and Salt Plains National Wildlife Refuge, Oklahoma), and 33% of all these were on wetlands in the Great Basin (including Great Salt Lake). Also, coastal habitats in central and southern Texas supported large numbers of breeding plovers. New breeding sites were discovered in interior deserts and highlands and along the Pacific coast of México; approximately 9% of the North American breeding population occurred in México. Because of uncertainties about effects of climate change and current stresses to breeding habitats, the species should be a management and conservation priority. Periodic monitoring should be undertaken at important sites to ensure high quality habitat is available to support the Snowy Plover population.

Shorebirds are thought to be declining across North America but trend analyses for migrant shorebirds at interior sites in eastern North America have not been updated since the late 1990s. Data from a volunteer-based survey at stopover sites throughout Ontario were used to assess population trends of shorebirds over the period 1974–2009. Surveyors carried out 7,135 surveys of 258 sites and recorded 538,744 individuals of 43 shorebird species. Of 19 taxa for which trends were estimated, 17 appeared to be declining in abundance. Precision of the trend estimates was generally poor and only three declines were significant at α = 0.05. Total numbers of shorebirds recorded on surveys declined by four per cent per year, resulting in an estimated decrease in abundance of greater than 75% over the 35 years of observation. Rate of decline may be increasing for some species as declines for twelve species were larger for the period 1989–2009 vs. 1974–1989, and six species showed significant declines in the latter period whereas none did in the former period. Relating these declines in abundance at the surveyed sites to population declines is complicated by several potential sources of survey bias including changes in turnover rates and in migration timing and distributions of the species. However, given that these results are consistent with those of other migration surveys as well as those on the breeding and the wintering grounds, the most parsimonious explanation remains a widespread decline in shorebird populations.

Colony size, nesting ecology and diet of Caspian Terns (Hydroprogne caspia) were investigated in the San Francisco Bay area (SFBA) during 2003–2009 to assess the potential for conservation of the tern breeding population and possible negative effects of predation on survival of juvenile salmonids (Oncorhynchus spp.). Numbers of breeding Caspian Terns declined 36% from 2003 to 2009, mostly due to abandonment of the Knight Island colony and decline of the Brooks Island colony, the two largest colonies in the SFBA. Concurrently, nesting success declined 69% associated with colony site characteristics such as (a) quality and quantity of nesting substrate, (b) vulnerability to nest predators, (c) displacement by other colonial waterbirds and (d) human disturbance. Marine fishes were the predominant prey in tern diets from the SFBA; however, diet composition varied among colonies. Juvenile salmonids comprised 22.9% of the diet of terns nesting in the North Bay, 5.3% of diet of terns nesting in the Central Bay, and 0.1% in the South Bay. Construction or restoration of nesting islands in the South Bay may help maintain and restore breeding Caspian Terns without enhancing mortality of salmonid stocks of conservation concern.

Great Egret (Ardea alba) and Cocoi Heron (A. cocoi) have a wide distribution in the neotropics but few data on reproductive biology for these species are available. The reproductive parameters, growth rate and diet of chicks of egret and heron in a mixed-species colony nesting were studied during the 2007 breeding season in a pampas wetland of Argentina, with 50 and 17 nests studied, respectively. Mean egret clutch size was 3.6 ± 0.5 eggs and hatching success 76%. Mean heron clutch size was 3.5 ± 0.8 eggs and hatching success 81%. The mean number of fledged egrets/egg was 0.15 and productivity 0.54 chicks per nest; for herons reproductive success and productivity were 0.17 and 0.58, respectively. In both species, the most productive clutch size was three. The first two weeks post-hatching were critical for chick survival. In egrets, the last chick to hatch had lower growth rates than the first or second hatched chicks; however in herons the first chick to hatch had higher growth rates than the second or third hatched chicks. Fish and insects were the main prey of egret chicks, while mammals and fish were the most common prey of heron chicks. Starvation was the main factor causing the relatively low breeding performance observed in both species.

To evaluate water-level manipulations as a management tool in boreal wetlands, marsh bird and waterfowl habitat use were studied in the Saskatchewan River Delta, Manitoba, Canada, during 2008 and 2009. Call-response and aerial surveys were used to estimate densities of marsh birds and waterfowl, respectively, within six wetland basins undergoing two different water-level treatments. Generalized linear models were used to determine relationships between presence and densities of birds to water depth, vegetation characteristics, and relative forage fish and invertebrate abundances at two spatial scales. American Bittern (Botaurus lentiginosus) and Piedbilled Grebe (Podilymbus podiceps) densities were positively influenced by water depth and relative fish abundance. American Coots (Fulica americana) and diver waterfowl (Aythya, Bucephala) also responded positively to increased water depth, whereas dabbler waterfowl (Anas, Aix) were negatively influenced by increasing water depth. Densities of Sora (Porzana Carolina) and Virginia Rail (Rallus limicola) were positively correlated with the relative abundances of invertebrates, but negatively correlated with relative fish abundance. Due to the high avian biodiversity in the region, managers should focus on providing a variety of wetland habitats. Using a combination of partial water-level drawdowns and high water, habitat for numerous avian species can be created simultaneously within wetland complexes.

The establishment of large Cattle Egret (Bubulcus ibis) breeding colonies in upland residential areas of east central Texas has been observed since the early 1960s. To help understand why Cattle Egrets choose residential breeding sites and predict where these might occur in the future, the geographic extent and scale-dependent nature of the phenomenon was investigated. In east Texas and along the Texas Gulf Coast, Cattle Egret colonies were found in flooded forests or on islands. However, in east central Texas, colonies were often located in upland areas. A habitat suitability model was constructed at multiple scales, outlining land use classes thought to influence upland colony site selection: water, forest and development/residential. The model classified 79% of upland colony locations in high or very highly suitable habitat and 7% in low or very low suitable habitat. The distribution of classes was significantly different than expected considering the distribution of land cover suitability classes across the entire study area (p = 0.036). Cattle Egrets likely choose upland, residential sites to breed when suitable wetland habitats are limited. When flooded tree and shrub or island habitats are absent, egrets may choose the edges of development for breeding sites to limit potential disturbance from ground predators.

Two specimens of adult Crested Auklet (Aethia cristatella) have been taken at sea in the North Atlantic Ocean: (1) near Iceland in August 1912 and (2) near Nuuk (formerly Godthåb), southwest Greenland between 1986 and 1972. An adult Parakeet Auklet (A. psittacula) was taken at Lake Vättern, Sweden in December 1860. These rare inter-ocean vagrants probably traveled from the Chukchi Sea east through the Canadian Arctic Archipelago to the Atlantic Ocean and may have arrived long before they were collected. Breeding distributions, limited post-breeding movements, weather patterns, timing and plumage of Atlantic and Pacific vagrants, small number of Atlantic vagrant records and the lack of inland records of these species east of Alaska in North America, support this route. Information about rare occurrences of auklets in the Atlantic Ocean enhances our knowledge of overall patterns of rare long-distance vagrancy versus more frequent vagrancy in alcids and other seabirds.

Over 16 field seasons, between 1981 and 2006, nearly 20,000 migrant Semipalmated Sandpipers were captured, weighed, and their bills and wings measured during the fall stopover in the Bay of Fundy. Annual mean bill and wing lengths declined over the course of the study. As eastern Semipalmated Sandpipers have longer bills and wings than those from the west, we interpret the decline to be the result of a reduced proportion of eastern birds in our samples. Semipalmated Sandpiper populations are in decline in North America, and our data suggest that the decline may be more severe in the eastern part of their breeding range. Body mass and size-adjusted mass at the migratory stopover study site have not declined during the study, suggesting that feeding conditions have not deteriorated there. Possibly, differing conditions experienced on the breeding grounds or overwintering areas may explain why eastern populations of Semipalmated Sandpipers may be declining more severely than those from the west.

The Semipalmated Sandpiper (Calidris pusilla) is a small, abundant shorebird that breeds primarily in sub-Arctic to mid-Arctic habitats across the Nearctic and winters principally along the northern and central coasts of South America. No subspecies have been described and little is known concerning their genetics. However, birds show a cline in bill length across the Arctic, with longest bills in the east and shortest in the west. There appear to be several ‘steps’ in the cline, suggesting a division into eastern, central and western breeding populations. Since females average longer bills than males in a breeding population, there is considerable overlap of bill lengths at migration staging areas. Based on bill length patterns and sightings and recoveries of marked individuals, most western breeders migrate south through the prairies, along with some birds from central Arctic populations. The remaining central Arctic breeders, and all eastern Arctic birds, migrate south through the north Atlantic Coast of North America, particularly the Bay of Fundy. Western Arctic breeders appear to winter farther west in South America than eastern breeders, although there is considerable mixing among populations in French Guiana and Guyana. In spring, birds from the eastern Arctic migrate north through the U.S. Atlantic coast, including Delaware Bay. Central and western Arctic breeders primarily migrate north through the interior of North America. Therefore, central Arctic breeders in particular demonstrate an elliptical migration pattern.

Although Semipalmated Sandpipers are one of the most common shorebirds in North America, analyses of migration trends using data from the Maritimes, International and Ontario Shorebird Surveys, as well as the Quebec Checklist, collected between 1974–1998, consistently showed negative trends. An additional eleven years of data was assessed to determine if declines were ongoing. Analysis (Pearson correlation) of the Quebec Checklist data indicated a significant decline overall, from 1976 to 2008, and the percentage of checklists reporting flocks of >1,000 birds has decreased significantly since the 1970s. New analyses of population trends with migration monitoring data from eastern and central North America were conducted for the 35-year period from 1974 to 2009, using program ESTEQNINDEXE. Trends, although generally negative, were not statistically significant. In the North Atlantic region, where survey sites had the highest counts of Semipalmated Sandpipers, average abundance indices showed a pronounced decrease between 1985 and 1999 and an increase since then. Although the trend was not statistically significant, declines in Ontario amounted to an estimated 8% per year from 1974 to 2009. Counts were variable for Semipalmated Sandpipers in the Midcontinent region, although average abundance indices appeared lower in the second half of the analysis period (1989–2009). Thus, the population status of Semipalmated Sandpipers in North America may have improved since the 1990s, at least in the east.

Counts of Semipalmated Sandpiper (Calidris pusilla) at some migratory stopover sites have shown pronounced declines over the last 35 years. Counts from breeding grounds avoid sources of bias that have proven troublesome for trends estimated from migration surveys. Published and unpublished data were reviewed to examine trends in densities of Semipalmated Sandpipers at breeding sites across Alaska and arctic Canada. Information was sparse, and some comparisons are tenuous because methods varied over time. Valid time series were obtained for 13 sites across the species' range. In Alaska, Semipalmated Sandpipers either increased or were at least stable at six sites and decreased at one site. Surveys at both sites in the central portion of the range suggested no change in abundance. In the eastern portion of the range, trends were variable: decreases were observed at two sites, a possible increase at one site, and no change at another. Thus, the species was generally increasing or stable in the western and central portions of the range and had an uncertain status in the east. Also, trends in presence/absence data were analyzed from the Northwest Territories and Nunavut Checklist Survey. The species was observed at 345 sites, and results suggested that birds increased significantly in prevalence (assumed here to be correlated with abundance) across arctic Canada between 1987 and 2007. Overall, data from the breeding grounds do not support a range-wide decline in the abundance of Semipalmated Sandpipers, although data are insufficient for the long-billed population from the eastern Arctic for which specific conservation concerns exist.

In the 1980's, aerial surveys in South America established that the main wintering areas of Semipalmated Sandpipers (Calidris pusilla) were found on the north coast of the continent, especially in the Guianas (Suriname, French Guiana and Guyana). Although population trend analyses have consistently shown declines in numbers of Semipalmated Sandpipers, especially for birds on migration in eastern North America, until now surveys had not been undertaken to determine whether such declines were reflected in numbers on the main wintering areas. Between December 2008 and January 2011, aerial surveys of major wintering areas in Suriname (3), French Guiana (2) and Guyana (1) were carried out. Results showed dramatic declines, with an overall total of only 21% of the 1980s total—a decrease of 79%. A variety of reasons may have contributed to the declines and include habitat changes, range shifts, sustained hunting, or increases in predation, pollution or severe weather.

Semipalmated and Least Sandpipers (Calidrispusilla, C. minutilla) were captured in Delaware Bay, USA, from 1995–1997 and from 2000–2008 to investigate changes in energetic condition during northbound migration staging. For Semipalmated Sandpiper, a model containing the effects of Julian day, period (Early: 1995–1997, Middle: 2000–2004, Late: 2004–2008) and habitat type (marsh, beach), as well as all interaction terms for these variables (the “full” model) had the strongest support (i.e. lowest AIC score) compared to six reduced models. Results suggested that mean size-adjusted mass declined significantly across periods (Early > Middle > Late). Also, rate of increase in size-adjusted mass within staging periods was significantly greater during the Early compared to Middle and Late periods. For Least Sandpiper, a reduced model that included Julian day and Period had the strongest support. Size-adjusted mass was significantly lower in the Late compared to Early and Middle periods, which were not different from each other. While in Delaware Bay, Semipalmated Sandpipers feed primarily on horseshoe crab eggs during episodes of rapid mass accumulation, but harvest pressure from 1995–2005 dramatically reduced egg availability. Least Sandpipers appear less dependent on this resource, which may explain differences between the two species regarding changes in energetic condition during staging periods in Delaware Bay. Long-term population trend indices suggest that Semipalmated Sandpiper has declined significantly since the 1980s, especially populations migrating along the Atlantic Coast en route to eastern Canadian breeding areas, which could be related, in part, to changes in food availability in Delaware Bay.

The diet of the Neotropical Cormorant (Phalacrocorax brasilianus) was evaluated in the Limay River basin, a freshwater system invaded by exotic salmonids. Analyses of 106 pellets showed that fish were the most important prey (79.9% by numerical frequency and 86.2% by frequency of occurrence), followed by two crustacean species. Among fish, the most common species were exotic salmonids, representing 84% by numerical frequency. Morphometric comparisons enabled differentiation of sagitta otoliths from Oncorhynchus mykiss and Salmo trutta and permitted determination of similar contributions of these species to the diet. Although a wide prey-size range was found, 85% of fish were smaller than 150 mm in length. The results suggest that the Neotropical Cormorant has adapted to changes in the fish community after the introduction of salmonids. Flexible feeding strategies of the Neotropical Cormorant and/or its capacity to exploit different environments probably make it less vulnerable to environmental changes produced by introduction of exotic fish.

Wading bird (Ciconiiformes) nesting success is influenced by the availability of aquatic prey, but principle prey may differ among species. During an excellent nesting year (2009) 118 boluses were collected from nestlings of three species, White Ibis (Eudocimus albus), Tricolored Heron (Egretta tricolor) and Snowy Egret (Egretta thula) in a mixed colony in the northern Everglades. Although these species have similar foraging depths and foraging flight distances from nesting colonies, crayfish dominated the ibis boluses while small-bodied fishes dominated egret boluses. Fish prey species composition in Snowy Egret and Tricolored Heron boluses did not differ. Compared to available fish species from nearby wetlands, the Egretta spp. did not exhibit taxonomic selectivity but did feed selectively on larger (2–4 cm standard length) fish. Whether restoration activities in the Everglades, including hydroperiod lengthening, will simultaneously enhance prey for both invertivores like White Ibis and piscivores, such as the egrets, remains an open question.

Reports of hybridization among herons are not uncommon but usually document interbreeding within genera and in captivity. An inter-generic hybrid pairing between a male Little Egret (Egretta garzetta) and a female Chinese Pond Heron (Ardeola bacchus) was video-recorded in a mixed-species heronry in Japan. In June 2010, nest-building behavior and copulation by the interspecific pair were observed. In August 2010, a juvenile possessing intermediate characteristics of the two species was fed by the female Chinese Pond Heron. These observations indicated that a fertile intergeneric hybridization occurred between the two species. The Chinese Pond Heron is an irregular visitor to Japan, but has been recorded more often in recent years. A rare species such as the Chinese Pond Heron might choose heterospecific mates rather than abandoning all chances of reproduction.

Little is known about whether chewing lice (Insecta: Phthiraptera) suppress or activate immunity in birds. Here, relationships between lice (Quadraceps punctatus, Saemundsonnia lari and Austromenopon transversum) and immune parameters were evaluated in Ring-billed Gull (Larus delawarensis) chicks. Eosinophils made up greater proportions of leukocytes in chicks with more lice (partial r = 0.64, P < 0.001), suggesting louse-induced immunoactivation via either eosinophil production or redistribution to peripheral blood. However, there were no significant relationships between lice and other immune parameters (proportion heterophils, proportion lymphocytes, heterophil:lymphocyte ratio, response to injection with phytohaemagglutinin). Collectively, results suggest only minor immune responses to lice, but experimental manipulations of louse infestations are needed to better quantify these responses and evaluate their potential consequences for fitness.

Small off-the-shelf unmanned aircraft systems (UAS) could prove useful for surveying waterbirds. A low-end model was evaluated for surveying flocks of Canada Geese (Branta canadensis) and Snow Geese (Chen caerulescens) by comparing photographic counts from repeated flybys to repeated visual ground counts. Due to low contrast of Canada Geese with the ground, UAS counts based on confident detections only had a lower mean than ground counts for five out of six flocks (>30% lower for three flocks) and coefficients of variation (CV) ranging from 11–106%, compared to 1–6% for ground counts. Conversely, UAS counts of high-contrast Snow Geese were 60% higher on average and less variable (CV = 1–6%) than ground counts (CV = 11%). In some cases the aircraft likely detected birds that were not seen from the ground due to an obstructed view. Shortcomings of the UAS were mainly related to its unsophisticated imaging system compared to more expensive models. Otherwise, the UAS proved capable of being conveniently transported and deployed over flocks without causing them to flush. Further consideration should be given to off-the-shelf UAS for surveying waterbirds over small areas (<5-km radius) that are difficult to survey from the ground or as an option for performing low-disturbance surveys.