The functional roles of nesting heron species (Ardeidae) as top predators in regional wetland landscapes may be sensitive to variation in nesting abundances at subregional scales corresponding to available habitat for nesting and foraging within individual wetland subsystems. This study investigates the dynamics of annual nesting abundances of four ardeid species within 10 major wetland subsystems of the San Francisco Bay Area, California, USA, during 1991–2010. Interrupted time series analysis was used to measure impact and recovery rates related to sudden major declines in nesting abundance below selected thresholds of annual change. Year-to-year persistence of initial impacts was above 78% for Great Blue Herons (Ardea herodias) and Great Egrets (A. alba). Snowy Egrets (Egretta thula) recovered more quickly, with 63–66% annual carryover of initial impacts. The time required for 95% recovery averaged 18.8 years for Great Blue Heron, 13.0 years for Great Egret, 7.2 years for Snowy Egret, and 14.5 years for Black-crowned Night-Heron (Nycticorax nycticorax). Most of the major subregional declines in nest abundance were associated with impacts at a single colony site. The results highlight the significant effects of sudden major declines in nesting abundance on the status of ardeids within individual wetland systems across a larger regional wetland landscape.

The Brazilian Merganser (Mergus octosetaceus) is globally classified as a Critically Endangered species and is one of the world's rarest waterbirds. The breeding ecology of this species was studied between 2005 and 2016 in the region of the Serra da Canastra National Park, Minas Gerais, Brazil. Between two and six nests were followed each year, with mean of 4.1 (n = 18 nests). Mean clutch size was 6.7 ± 0.9 (n = 31 clutches) with a range of five to eight eggs per nest. Average incubation constancy was 88.3% (n = 3 nests) and ranged from 86.7% to 90.7%. Mean incubation temperature and humidity were obtained from three nests and ranged from 33.6 °C to 33.8 °C and 65.9% to 70.2% respectively. The nest success was 77.1%, and the duckling survival (up to 8 weeks) was 53.8%. Nest predation was relatively low at 7.9%, and the annual reproductive output was 4.7 ducklings/female. Data on breeding ecology is fundamental in guiding conservation strategies, both in the field and in captivity.

Stable isotope analysis is often used to identify the geographic origins of migratory bird populations. While this method can accurately predict the provenance of migratory species, stable hydrogen isotope values measured in feathers (δ²H_f) can be variable within a site and may be influenced by differences among age class (second year vs. after second year), type of feather (primary vs. rectrix), year of sampling, species, and local hydrology. In this study, sources of variation in δ²H_f values were assessed in a wetland-associated Neotropical migratory bird, the Prothonotary Warbler (Protonotaria citrea), by comparing δ²H_f values among age classes, sexes, years and feather types in individuals breeding in eastern Virginia, USA. Age and year were found to influence δ²H_f values, with individuals in their second year having more depleted δ²H_f values (-62.43 ± 9.56‰) than individuals older than 2 years (-53.73 ± 9.04‰). Differences between primaries and rectrices were within the range of sampling error (-2.98‰), and there was no effect of sex. For wetland-associated songbirds, age-related differences in the dietary proportion of aquatic vs. terrestrial prey may provide an additional mechanism for differences observed in δ²H_f values between age classes. In studies that use stable isotopes to assign geographic feather origin, researchers should attempt to account for and propagate known variation in δ²H_f values in assignment models whenever possible.

Devil's Slide Rock, a rock sea stack on the central California coast near San Francisco, USA, hosts a Common Murre (Uria aalge) colony that was recently restored after it was extirpated in the mid-1980s. Since the late 1990s, low-flying aircraft have threatened the colony at Devil's Slide Rock. To assess variables contributing to Common Murre disturbance, multinomial log-linear models were constructed and evaluated using reproductive timing and aircraft characteristics for 7 years (2008–2014). The top model included seven variables (year, reproductive timing, time of day, aircraft type, aircraft category, aircraft altitude and aircraft lateral distance from Devil's Slide Rock) and the interaction effects between aircraft type and aircraft category, and between altitude and distance. The odds of disturbance varied temporally, with 2010, 2011, 2013 and 2014 exhibiting greater odds of disturbance than 2008. Disturbance response was more likely during the pre-egg lay period and post-chick hatch period than during incubation; 47%, 51%, and 40% of over-flights, respectively, resulted in agitation or flushing. Helicopters were more likely to cause disturbance than fixed-wing aircraft; 72% of helicopter over-flights and 39% of fixed-wing aircraft resulted in agitation or flushing. Flushing was more likely to occur at lower aircraft altitudes and closer lateral distances; all flushing from over-flights occurred below 305 m, and 91% of agitation events occurred below 305 m. These results support the need for measures to reduce over-flight disturbance of the Devil's Slide Rock colony.

Nestling diet and parental provisioning rate are important determinants of reproductive success and future offspring performance in birds. The diet of Black Stork (Ciconia nigra) nestlings was characterized and tested for intra-seasonal and brood-size dependent variation in the type and mass of prey provisioned to the brood. Data were collected on 576 prey items from 45 Black Stork broods in central Poland during 2005–2016. Black Stork nestlings were provisioned almost exclusively with fish and amphibians; the proportion of invertebrates in their diet was marginal. Fish were a dominant component of nestling diet, comprising up to 65% of prey items and over 85% of total prey mass. Common spadefoot tadpoles (Pelobates fuscus), weatherfish (Misgurnus fossilis) and Prussian carp (Carassius gibelio) were among the most abundant prey. Black Storks foraged on relatively small prey, with an average length of 101.4 ± 1.5 mm (n = 576) and an average mass of 13.8 ± 1.0 g (n = 550). Larger broods were significantly more often fed with amphibians and with lighter prey. As the season progressed, the probability of preying on amphibians increased. This study provides evidence for Black Stork provisioning effort optimization mediated by selection of smaller, but easier to catch and handle prey, such as common spadefoot tadpoles.

A quantitative investigation examining the effect of changes in wetland habitat on reproductive output of Western and Clark's grebes (Aechmophorus occidentalis and A. clarkii, respectively) was conducted. Earlier studies examined local factors influencing nest success. This study supplements earlier work by seeking to determine which landscape-level habitat elements best predict annual landscape-level reproductive output of grebes. Western and Clark's grebes were monitored during the breeding season from 14 September 1998 to 20 September 2010 at Eagle Lake, California, USA. Remotely-sensed images were used to develop habitat indices and quantify changes in wetland availability and quality. The effect of these indices, and lake level, on annual reproductive output was analyzed using an information theoretic approach. Indices of habitat availability (β_i = 0.20, 95% CI = 0.099–0.31) and habitat quality (β_i = 0.28, 95% CI = 0.012–0.45) best predicted and had a positive effect on annual reproductive output. Lake level had little direct predictive power but was highly correlated with the other habitat covariates (Pearson's r > 0.80), indicating its importance as an indirect predictor of reproductive output. Thresholds of habitat availability and habitat quality were found, below which steep declines in reproductive output were observed.

Kelp Gull (Larus dominicanus) foraging patterns were studied by deploying GPS loggers on 20 incubating individuals at their colony in the Bahía San Blas protected area, Argentina. Mean number of trips per day was 1.5 ± 0.5, and mean trip duration was 272.6 ± 165.2 min. Mean maximum distance from the colony was 19.6 ± 24.4 km. Incubating Kelp Gulls visited natural and anthropogenic environments. Individuals switched between two or three different habitat types 47% of the time during a given foraging trip. Kelp Gulls showed a differential use of feeding areas, with a significantly higher use of refuse dumps (75%; n = 151 trips) than coastal (47%), terrestrial (10%) and offshore (10%) habitats. In 72% of the recorded trips, Kelp Gulls targeted the dump located in the small town of Bahía San Blas, where waste generated by recreational fishing is regularly disposed. Moreover, most visited shoreline locations were those regularly used by recreational fishers. Despite showing plasticity in foraging habitat use, the local refuse dump and nearby shoreline sites where fish waste is regularly disposed were the main feeding habitats for incubating Kelp Gulls.

A frequently used method to estimate diet composition is based on the identification of fish otoliths present in pellets and feces. However, whether pellets and feces provide similar unbiased estimates of the diet remains poorly understood. The diet of African Royal Terns (Thalasseus maximus albididorsalis) breeding in the Parc National du Delta du Saloum, Senegal, was studied. Prey species composition based on otoliths in freshly regurgitated pellets and a mixture of pellets and feces (excrement) accumulated near nests during the incubation period were compared. Altogether, 59 fish species were identified. Pellets contained far less prey species than excrement. Maximum diet overlap between excrement and pellets varied between 0.34 and 0.43 (mean = 0.36). Differences between minimum and maximum overlap between both sample types were small in all years. Pellets contained almost exclusively large otoliths (widths 3.0–8.5 mm), whereas excrement contained two fractions: large sized ones, identical to those present in the pellets and smaller-sized ones (0.5–3.0 mm) originating from feces. It is hypothesized that large otoliths cannot pass the intestinal tracts of the birds and are therefore regurgitated. Differences in prey species composition in pellets and excrement could potentially be explained by a combination of seasonal changes in availability of prey species and size of otoliths. Neither pellets nor feces alone give an unbiased picture of the diet of African Royal Terns.

A rapid and reliable method to age California Brown Pelican (Pelecanus occidentalis californicus) pre-fledged young based on exposed culmen measurements is presented. In 1997, 1998, and 1999, a total of 52 unknown-age young were marked and recaptured one to three times throughout the nesting season on Isla Piojo, Bahía de Los Angeles, Mexico. From culmen growth increments of these young, we developed an age scale. The linear equation that described the age/culmen relationship was: estimated age (week) = exposed culmen length (cm) x 0.378 – 0.565. The accuracy of the model, as calculated by the k-Fold cross validation method, was 0.149. California Brown Pelican chicks can thus be aged by culmen length measurements. The application of this aging technique allows the mass of chicks to be plotted against their ages to obtain an average body mass growth curve for any sampled cohort of young California Brown Pelicans based on less frequent visits to the colony to minimize the potential effects of disturbance.

Physiological parameters provide relevant information on the general physical condition of freeliving birds. Blood parameters related to immune function, nutrition, and oxidative stress of Kelp Gulls (Larus dominicanus) that use fishery waste sites as feeding sites are reported. The presence of zoonotic bacteria in cloacal swabs was also assessed. Ranges of hematocrit, total proteins, glucose, and leukocyte counts were similar to those reported for other gull species and healthy birds in general. Heterophil and lymphocyte percentages were the only parameters affected by handling time of the birds. Reports of bacterial agglutination as an index of humoral innate immunity and oxidative stress makers are the first for the species. Kelp Gulls showed infection prevalence of 60% with Corynebacterium sp. and 30.5% with enteropathogenic Escherichia coli. Data presented here constitute a valuable contribution for future comparative studies and as baseline for clinical work.

Scant attention has been given to the molting patterns of known-age Double-crested Cormorants (Phalacrocorax auritus). In general, subadult individuals are identified with a tan, buffy or mottled chest, and adults are identified with a black chest. While studying Double-crested Cormorant population dynamics in Ontario, Canada, with known-age birds, it was noted that the plumage of many (> 75%) breeding adults changed from black to heavily mottled during the course of the breeding season. No pattern with age was observed; plumage changed in equal proportions for all ages from 2-year-olds to 7-year-olds. A similar but reverse pattern has been observed with Double-crested Cormorants roosting at sites in the southeastern USA during fall migration. Whereas the majority of the roost had juvenile/subadult plumage in September, by mid-January the roost had shifted to 75% adult black plumage. The mechanism behind the plumage change is unknown, but extreme caution is advised when using plumage to age cormorants, especially during the winter months. By describing our observations with Double-crested Cormorants, we hope to encourage future formal research on within-season plumage changes.

Nest usurpation is a strategy in which an individual or pair of one species takes over the nest of another species. This is the first documented occurrence of a Piping Plover (Charadrius melodus) pair usurping an Interior Least Tern (Sternula antillarum athalassos) nest. The Piping Plovers incubated the three Interior Least Tern eggs in the nest, and all three eggs hatched. The adult Piping Plovers accompanied and brooded the Interior Least Tern chicks for 1 day post-hatching, but we did not see the adult Piping Plovers nor the Interior Least Tern chicks after that day. The Piping Plovers likely usurped the Interior Least Tern nest because they developed hormonemediated broodiness after they lost the eggs from their two previous nesting attempts. When the Piping Plovers encountered an unattended Interior Least Tern nest with eggs, they instinctively took the nest and its contents as their own.

Small unmanned aircraft systems present an emerging technology with the potential to survey colonial waterbird populations while reducing disturbance in comparison to traditional ground counts. Recent research with these systems has been performed on some colonially nesting avian species; however, none have focused on wading bird species. During 2015–2016, this study tested the behavioral response of a mixed-species rookery (Cattle Egret (Bubulcus ibis), Snowy Egret (Egretta thula), Glossy Ibis (Plegadis falcinellus) and a groundnesting colony of Common Terns (Sterna hirundo)) in shrub habitat to small unmanned aircraft system flights at 12 m, 15 m, 30 m, and 50 m. Even at the lowest altitudes, the birds either showed no reaction or acclimated within 60 sec of the fly-over. Conversely, physically entering the colony to conduct ground surveys resulted in all Common Terns flushing from their nests beginning when the observer was 50 m away and required significantly more time in the colony overall: ~30–60 min vs. ~3–7 min with the small unmanned aircraft system. While this study focuses only on the behavioral response of nesting birds and not comparison of count estimates, these results provide preliminary evidence that small unmanned aircraft systems provide the potential to monitor colonial nesting bird populations while minimizing disturbance to the colony.

Between 25–30 November 2013, 2014 and 2015, miniaturized video cameras were attached to Magellanic Penguins (Spheniscus magellanicus; n = 14) in Punta Norte/San Lorenzo, Península Valdés, Chubut, Argentina. The objective was to examine prey selection, consumption of untraceable prey, and inter- and intraspecific interactions. During 56.3 hr of video footage, 1,621 dives from 14 individuals were recorded. Magellanic Penguins swam through shoals of lobster krill (Munida gregaria morph subrugosa), selectively consuming the fish, primarily anchovies (Engraulis anchoita), that were dispersed along the shoal, but did not consume the lobster krill. Magellanic Penguins captured fish on dives of less than 2 m in depth. The tagged individuals foraged with conspecifics in 2% (n = 33) of the total recorded dives. In addition, a multispecies feeding association was also documented (n = 1). Results were constrained to the upper 40 m of the water column; below this depth light level was too low for detections by video. The development of cameras with a light source and wider-angle lens are crucial to improve our understanding of Magellanic Penguin foraging behavior.