Socotra Cormorants (Phalacrocorax nigrogularis) are a regionally endemic, locally abundant species restricted primarily to the Arabian Gulf and coastal Oman. The species has declined since the 1980s and is currently categorized as Vulnerable by the International Union for Conservation of Nature. Breeding phenology, breeding performance and variation in breeding population size were studied on Siniya Island, the largest colony in the United Arab Emirates. Laying dates were between 13 September and 6 October during the 2011– 2015 breeding seasons. Incubation was estimated to be 24–27 days, and clutch size ranged from 2.21–2.79 eggs/ nest. Hatching success ranged from 58.71 ± 5.85 in 2011 to 81.76 ± 4.86% in 2012. The total population varied over the 5 years of study from 28,152 ± 3,780 pairs in 2011 to 41,568 ± 3,761 pairs in 2014. Population estimates using density-area calculations were closely aligned with ground counts. The use of a drone with a mounted camera greatly improved the counts in 2015. The Socotra Cormorant breeding population on Siniya Island appears to be stable over the short term with annual fluctuations comparable to other cormorant species. Thus, our data suggest the breeding population on Siniya Island could have surpassed that of other colonies in the Arabian Gulf, underscoring its global significance.

A small colony of nesting Lesser Snow Geese (Chen caerulescens caerulescens) was discovered on the Ikpikpuk River delta in 1992. The number of nesting pairs averaged 35 (Range = 0–60) from 1992 to 1998, then increased dramatically from 176 in 1999 to 12,373 in 2015, for a λ of 1.40 (SE = 0.138). Concomitant with this dramatic population increase, the geographic extent of the colony expanded annually from three small islands in the northwestern portion of the delta during 1992–1999 to all vegetated deltaic islands in 2001 and farther inland on the mainland from 2006 onward. When colony growth was most rapid (2001–2008), nesting success averaged 79% (Range = 48–97%). Low nesting success during 2009–2014 (< 50% in all years except one), primarily caused by brown bears (Ursus arctos), was followed in 2015 by 96.6% success. In 2015, ∼22,000 adults (in both brood-rearing and adult-only flocks) were accompanied by more than 25,000 goslings in July and August. These numbers represent a remarkable increase in the abundance of Snow Geese west of the Colville River, where only 15 years previously fewer than 500 birds nested. Both immigration and high productivity probably have contributed to colony growth, although the relative importance of effects of the two factors in this growth has not been determined. Further analyses may provide insights into population relationships and the management implications of rapid local and regional growth of Snow Goose populations in northern Alaska.

Discriminant functions based on external body size measurements are widely used to sex different gull species with great accuracy. However, all of them have been derived for adult birds, which puts into question their usefulness for sexing immatures due to possible changes in size as birds mature. To address this issue, discriminant functions that allow sexing of Herring Gulls in immature age classes with an accuracy of 88–100% were developed. In total, 247 males and 111 females of wintering Herring Gulls, including birds in the first, second and third winter plumages and individuals in adult plumage, were measured and sexed in the region of the Gulf of Gdańsk (southeastern Baltic coast). In all age classes, total head length and bill depth were the best traits for sexing Herring Gulls. However, bill depth, but not total head length, increased with age. Hence, in the first and second winter plumages, total head length made a much higher contribution to the discriminant function than bill depth. In the third winter plumage, bill depth became more important. For individuals in adult plumage, however, the contribution of total head length and bill depth were nearly the same. Hence, using discriminant equations derived for adults resulted in erroneous sexing of 4.5–8.9% of immature males, which were identified as females, and illustrates the importance of deriving age-specific discriminant functions.

Recovery (i.e., shot, retrieved, and reported) rates and daily mortality risk of 52,330 adult Mallards (Anas platyrhynchos) leg-banded during pre-molt, in-molt, or post-molt during 1985–2011 were evaluated to better understand mortality during wing molt in dynamics of the Mallard population in California, USA. Recovery rates and non-hunting mortality risk varied by molt status at time of banding and California region where banded. Mallards banded during post-molt were 1.22 (95% credible interval = 1.10–1.32) times more likely to be recovered than Mallards banded pre-molt; recovery probability was similar for pre-molt and in-molt Mallards. Mallards banded post-molt had 0.43 (0.17–0.98) and in-molt 0.87 (0.51–1.49) times the daily risk of non-hunting mortality as Mallards banded pre-molt. Mallards were 0.92 (0.86–0.98) times as likely to be recovered, and daily risk of non-hunting mortality was 2.93 (1.79–4.94) times greater, if banded in Northeastern California than in California's Central Valley. Results indicate that high mortality during the molt period, especially in Northeastern California where most Mallards that breed in California molt, might be negatively affecting recovery (and potentially annual survival) of Mallards in California. Thus, conservation programs that reduce mortality during molt could help attain the desired population size for Mallards nesting in California.

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.

Methylmercury biomagnifies in food chains and can lower reproductive success in many organisms, particularly in top predators such as Brown Pelicans (Pelecanus occidentalis). To determine and compare variability in mercury exposure in this species, chick feathers and egg membranes were collected from seven breeding sites located in the remote Pamlico Sound and the more human-impacted Cape Fear River in North Carolina, USA. The average concentration of total mercury in egg membrane was 0.20 ± 0.14 ppm dry weight, a level associated with slightly reduced reproductive success in some birds, while chick feather total mercury concentrations (1.13 ± 0.02 ppm fresh weight) were well below the lowest observable adverse effects level. Mercury exposure did not vary between the Cape Fear River and Pamlico Sound, but did vary significantly among three Cape Fear River colonies. Diet analysis using δ¹³C and δ¹⁵N revealed minimal differences in the trophic level and foraging location of prey between islands in close proximity, indicating that differences in mercury availability are not due to differences in diet composition. The source of mercury variation in Brown Pelicans remains unknown and in need of further study.

Migratory connectivity of Caspian Terns (Hydroprogne caspia) was investigated using individuals marked in North America between 1922 and 2015. The results support recent genetic work describing three breeding regions (Pacific, Great Lakes, and Central Canada). Further, our results show strong migratory connectivity of Pacific breeders to wintering regions in central and western Mexico, and connectivity of Great Lakes breeders to wintering regions in the Gulf of Mexico and Caribbean. This integrated picture of demographic connectivity throughout North America should help in planning more effective management of the species.

Paired throat and cloacal swabs, along with feather samples, from nesting Double-crested Cormorants (Phalacrocorax auritus) at two sites in Illinois, USA, were tested for presence of invasive bigheaded carp (Hypophthalmichthys spp.) DNA. We also used DNA from the feather calamus to determine cormorant sex. Throat and cloacal swabs from cormorants at both locations tested positive for DNA from silver carp (H. molitrix), but none tested positive for bighead carp (H. nobilis). Hypophthalmichthys DNA was not detected on feathers. There were no significant differences among positive Hypophthalmichthys DNA detection frequencies between cormorant sexes. To our knowledge, this is the first demonstration of silver carp as part of the Double-crested Cormorant diet in North America. Hypophthalmichthys are major invasive species of concern in this region, the detection of water-borne environmental DNA of Hypophthalmichthys is an important monitoring tool, and the potential movement of DNA via piscivorous birds may have significant implications for interpreting environmental DNA monitoring data.

King Rails (Rallus elegans) in the more northerly, migratory population that breeds in the Upper Midwest (i.e., Wisconsin, Minnesota, Michigan, Iowa, Indiana, Illinois, and Ohio), USA, are poorly studied due to their low abundance and secretive nature. A pilot project was conducted in 2014 and 2015 to evaluate trapping efficiency and detection techniques of King Rails in northwest Ohio. The project site has held strong numbers of King Rails historically, but they are now rarely recorded during formal marshbird surveys. The objectives of this project included evaluating the trapping efficiency of walk-in traps in comparison to whoosh nets for King Rails and comparing secretive marshbird surveys with call-broadcast trap sites monitored by trail cameras for obtaining King Rail detection data. Six King Rails were captured using walk-in traps, and two were captured using whoosh nets. Whoosh nets proved to be more effective with a capture rate of 0.28 individual King Rails per trap night compared to 0.02 individuals captured per trap night using walk-in traps. Based on an estimated minimum count, 13 King Rails were detected in 2 years at established trapping locations (n = 147 trap nights) as compared to zero King Rail detections during that same time period while conducting secretive marshbird surveys (n = 84 points). The current secretive marshbird survey protocol may be handicapped for rare species with low rates of detectability because the surveys are limited on a temporal scale (i.e., only 10 min of monitoring per survey point in many instances). A camera trap array could be a viable option for developing occupancy models or even estimates of abundance for these rare species and further informing secretive marshbird survey data.

A unique prey handling behavior of the Eurasian Spoonbill (Platalea leucorodia) was observed at Büdös-szék, a soda pan near Pusztaszer, Hungary, on 13 May 2007. The observed individual caught a large marsh frog (Pelophylax ridibundus), but was unable to swallow it immediately because the marsh frog kept spreading its limbs as a defensive behavior. Using its lower and upper mandibles, the Eurasian Spoonbill exerted a series of pressing movements to the head and body of the marsh frog, and then grabbed each limb with its bill and shook the marsh frog under the water to break the limbs one by one. Finally, when all the limbs had been broken, the bird was able to swallow the large marsh frog. This prey handling took approximately 10 min.

Hybridization within the genus Platalea has only been reported in captivity. A case of natural hybridization between two female Black-faced Spoonbills (Platalea minor) and a male Eurasian Spoonbill (P. leucorodia) was studied on a small breeding islet in Incheon, South Korea. The male Eurasian Spoonbill formed a pair with each Black-faced Spoonbill female during the 2012–2013 and 2014–2015 breeding seasons, respectively, and laid 11 eggs in total, producing nine successful hybrid offspring. Two fledglings were color-banded in 2013, and one of them returned to its natal site in 2015 and 2016. The hybrids had intermediate morphology between Black-faced and Eurasian spoonbills: larger body size and longer bill and legs than those of Black-faced Spoonbills, narrow band of black bare skin on the lore to the eyes, a small yellow naked chin and no bared throat.

Monteiro's Storm-petrel (Hydrobates monteiroi) is a small seabird endemic to the Azores archipelago, where it is known to breed only on two mammal-free islets. Total breeding numbers are between 250 and 300 pairs. During the 2015 breeding season on Praia Islet, six Madeiran wall lizards (Lacerta dugesii) were observed depredating a Monteiro's Storm-petrel chick about to fledge. In August 2015, a freshly killed chick without its head and four larger dead chicks were found. Eight other chicks had disappeared from their nests since our previous visit in early July. In 2016, there was further evidence of suspected lizard depredation. Three chicks were found predated and dragged out of their nests, and an additional 22 chicks disappeared from their nests before fledging. In 2016, Monteiro's Storm-petrel breeding success was only 26.8%, the lowest ever recorded. We suspect that some of the chick deaths and nest failures may be attributed to these introduced lizards. All chicks were found dragged out of their nests, a behavior that is not consistent with kills from aerial predators. Lizards were suspected because they are the only possible predator on land. Therefore, we recommend evaluating the impact of Madeiran wall lizards on the two Monteiro's Storm-petrel main colonies: Praia and Baixo Islets.

Waterbirds, the journal of the Waterbird Society, welcomes the submission of articles, notes, critical commentary manuscripts, and reviews that deal with the biology, status, techniques of study, and conservation of aquatic birds. Our goal is to encourage communication among those interested in this group of birds. Detailed instructions for contributors may be found elsewhere in this issue. Waterbirds is listed or abstracted in Biological Abstracts, Wildlife Reviews, Current Contents, and the Zoological Record. Waterbirds is printed by E. O. Painter Printing Co., P.O. Box 877, DeLeon Springs, Florida, 32130, USA. Please return defective copies to the printer for replacement.

The quality of any scientific journal greatly depends on the evaluations provided by referees. The editorial staff not only relies on their expertise and assessment in deciding which manuscripts to publish, but their efforts substantially improve the quality of the manuscripts that are published. We thank the following individuals who served as reviewers for manuscripts submitted to Waterbirds from 1 January 2016 to 31 December 2016 (names in bold indicate those who contributed two or more reviews).