Count data suggest that Black Oystercatcher (Haematopus bachmani) has locally variable but globally stable populations. A simple, stage-based matrix population model for Black Oystercatcher was built and Monte Carlo simulations of the model were conducted using vital rates from peer-reviewed and gray literature. Simulations yielded a distribution of potential population growth rates that extended from 0.87 to 1.14 and was centered at 1.00, supporting the hypothesis of a globally stable Black Oystercatcher population. Sensitivity and elasticity analyses of the population model showed that potential population growth is particularly sensitive to changes in hatching success (i.e., proportion of eggs hatched), fledging success (i.e., proportion of chicks fledged), and breeding adult annual survival. These rates could be possible targets for population management should it become necessary given future changes in sea temperature, sea level, and coastal development. Pair productivity, which integrates hatching and fledging success, is suggested as a simple and valuable metric for monitoring population growth potential of Black Oystercatcher.

The Red-billed Tropicbird (Phaethon aetehreus) is a seabird that breeds on islands in tropical seas. The Mexican government has listed it as threatened; however, the International Union for Conservation of Nature considers it of least concern, although it recognizes that its global population is decreasing. Its breeding ecology was studied at Peña Blanca island, Colima, México, through monthly visits from 15 January 2008 to 10 December 2009. By extrapolating density in a 4,227-m² survey area, 1,390 (2008) and 1,225 (2009) nests were estimated for the entire colony. In both years, the earliest eggs were laid in September, and the last active nests were recorded during 14 May–19 June, with peak activity on 7 March 2008 and 25 February 2009. Egg volume was not different between years (57.4 cm³ ± 5.1 vs. 56.8 ± 3.3), but nest success was higher in 2008 (77% vs. 57% in 2009). Highest nest densities occurred between January and May, coincident with regional upwelling processes (colder water and high concentration of nitrites, nitrates and chlorophyll-a). The Red-billed Tropicbird colony on Peña Blanca is the largest Mexican colony and one of the two largest colonies of the world.

The breeding distribution and population size of the Red-billed Tropicbird (Phaethon aethereus) in Mexico were reviewed. This species has been confirmed to breed on 14 and potentially breed on six Mexican Pacific islands: two in the North Pacific, 12 in the Gulf of California, and six in the Tropical Pacific. The breeding population has been estimated to be approximately 1,901–2,725 breeding pairs. This estimate includes between 507–713 pairs in the Gulf of California, 1,391–2,004 pairs in the Tropical Pacific, and the rest in the North Pacific. The largest colonies are Peña Blanca in Colima (1,250–1,650 pairs), Farallón de San Ignacio in Sinaloa (150–228 pairs), San Pedro Mártir in Sonora (150–190 pairs), San Benedicto in the Revillagigedo archipelago (50–200 pairs), Isabel in Nayarit (87–155 pairs), and Morros El Potosí in Guerrero (100 pairs). The portion of the population that breeds in Mexico is numerically important at both regional (Pacific Ocean) and global scales, representing approximately 50% of eastern Pacific breeding pairs and 25% of the global population, respectively. Therefore, protection of these colonies can play an important role in the global conservation of this species.

Consideration of annual population count data, stream flows, water levels, and nesting habitat availability over a 29-year period suggest that Least Terns (Sternula antillarum athalossos) nesting along the Cheyenne River and Oahe Reservoir in South Dakota, USA, select areas primarily in response to reservoir water levels early in the breeding season. Generalized linear models were selected in an information-theoretic framework and showed important relationships between adult Least Tern numbers and reservoir levels, as well as a negative long-term temporal trend in both survey areas. Reservoir levels alone could not account for the temporal trend. The number of adult Least Terns on the Cheyenne River was positively correlated (R = 0.668) with mean May reservoir water levels—a more important relationship than that between adult numbers and river levels. The number of adults on the Oahe Reservoir was negatively correlated (R = -0.573) with mean May reservoir water levels. Numbers of adults on the Cheyenne River and on Oahe Reservoir were negatively correlated (R = -0.684), suggesting that birds may interact as one population across the two areas. This information should help managers to consider ecological relationships among segments of the Least Tern population on the Missouri River and its tributaries and options for managing Least Terns on the Cheyenne River, Oahe Reservoir, and elsewhere on the Missouri River system.

For migratory waterbirds, the availability and quality of suitable stopover habitat can affect body condition and demographic parameters throughout the annual cycle. This study investigates the importance of the Salton Sea, a large saline lake located in the southwestern United States near the USA-Mexico border, for migrating Caspian Terns (Hydroprogne caspia) fitted with long-duration satellite telemetry tags in the northwest contiguous USA. During fall migration, 100% (n = 25) in 2014 and 98% (n = 63) in 2015 of all tagged individuals were tracked to the Salton Sea, with median durations of stay lasting 36 and 25 days, respectively. Use of the Salton Sea during subsequent spring migrations was less consistent than in fall, but still substantial, with 91% (n = 23) and 68% (n = 53) of all birds conducting brief stops there during 2015 and 2016, respectively. The future of the Salton Sea as suitable habitat for fish and piscivorous birds is uncertain due to rising salinity levels caused by reduced input flows. It is also uncertain if other wetlands in the region can serve as replacement habitat for Caspian Terns and other migratory piscivorous species should the Salton Sea cease to provide fish prey.

Identifying sexes in birds from visual observations could be a useful and inexpensive method. While sexual dichromatism and ornaments are readily used by observers, sexual size dimorphism can also be used to identify sexes in some bird species. This study assessed the applicability of visual observation of size differences to identify sexes in adult Black Skimmers (Rynchops niger). Black Skimmers do not have sexual dichromatism; however, Black Skimmer males are skeletally larger (6.7–31.7% depending on trait) and 33.3–37.5% heavier than females. The study focused on two subspecies: Amazonian (R. n. cinerascens) and South American (R. n. intercedens) Black Skimmers. Sex identified by visually observing size differences was consistent with the sex identified at specimen preparation from examining gonads (R_GLMM = 0.996 ± 0.004). The identification of sexes from photographs using visual observation of size had a very high within- (R_GLMM = 0.995 ± 0.001) and between- (R_GLMM = 0.984 ± 0.002) observer repeatability. Non-invasive methods for identifying sex by visual observation may allow enhanced use of data from photographic datasets, citizen science projects, and surveys using direct observation or images.

Four cases of interspecific mixed broods between Little Egrets (Egretta garzetta; n = 175), Cattle Egrets (Bubulcus ibis; n = 125), Squacco Herons (Ardeola ralloides; n = 25) and Black-crowned Night-Herons (Nycticorax nycticorax; n = 199) were recorded from 7 April to 16 August 2016 at two colonies in Iran. The rare occurrence of mixed broods and the low survival of the parasite chicks suggest that brood parasitism is not adaptive in the Ardeidae.

Dalmatian Pelicans (Pelecanus crispus, n = 3 breeding pairs) at the Shanghai Zoo, China, were used to study breeding behavior and nest conditions using automated telemetry from 21 February to 25 March 2011. Both sexes were found to participate in egg incubation, but females spent 341.7 ± 180.0 min incubating while males spent 378.3 ± 180.8 min incubating during daylight hours. Females turned the eggs at 51.5 ± 22.8-min intervals, whereas males turned the eggs at 70.0 ± 64.3-min intervals. However, the differences between the sexes were not significant. The time budget of the Dalmatian Pelicans indicated that the breeding birds saved energy by reducing locomotion and increasing the time spent resting during the breeding season. The average nest temperature during the study was 35.5 ± 0.8 °C (Range = 33.1–37.1 °C), and diurnal fluctuations in egg temperature were small (F = 0.570, P = 0.942). The average relative nest humidity was 55.7 ± 4.8% (Range = 39.8–66.9%), and changes during the day were not significant (F = 1.347, P = 0.148). Therefore, ambient conditions had little effect on nest conditions in this study, but the sample size was limited.

The availability of shelter to avoid predation and ameliorate physiologically stressful conditions is often important to the survival of avian hatchlings. However, as changes in habitat availability force birds to nest in nontraditional locations, young must quickly adapt to using novel sources of shelter. Two Common Tern (Sterna hirundo) colonies (one vegetated and one barren) were observed during the 2017 breeding season on a remote island habitat restoration project during data collection for a larger associated study. While chicks within the vegetated colony sought shade under vegetation, those in the barren colony were frequently found under anthropogenically constructed chick shelters. The first reported instance of Common Tern chicks using Bank Swallow (Riparia riparia) burrows for shelter was also observed in the barren colony. This behavior, when paired with other similar reports, suggests that this species is able to recognize beneficial shelters, both natural and anthropogenic, and use them at a young age, an important ability if they are to successfully reproduce in atypical habitats. The Erratum for this article is available in Waterbirds 42(2).

Grebes typically build floating nests that are attached to vegetation and very rarely construct nests on non-floating structures. On 29 August 2017, a pair of Least Grebes (Tachybaptus dominicus) was photographed nesting on top of a non-floating concrete structure on a sewage pond at Roatán, Honduras. This observation demonstrates that Least Grebes may nest on artificial ponds lacking sufficient vegetation for constructing and anchoring a floating nest provided that a suitable flat and hard surface is available just above the water's surface.

This paper introduces the special section prepared for Waterbirds from selected papers originally presented at a symposium titled “Recent Advances in Biology and Management of Double-crested Cormorants (Phalocrocorax auritus)”, held in Bar Harbor, Maine, USA, at the 39th Annual Meeting of the Waterbird Society, 11–15 August 2015. The principal objective of this symposium was to explore and communicate about ways to address conflicts with this species that would result in fewer birds being killed under legal management programs. Fifteen papers were presented in three subject categories: population status and new research; knowledge-based challenges for Double-crested Cormorant management; and ethical, bird conservation and other perspectives on cormorant management. Three papers from the second two categories provided unique and important perspectives on ways to manage conflicts in which fewer birds would be destroyed and are presented here. The well-developed approaches in these papers are important steps toward a knowledge-based path to resolving conflicts and, most importantly, living with Double-crested Cormorants.

In 2000, studies began on the Double-crested Cormorant (Phalacrocorax auritus) in the Beaver Archipelago, Lake Michigan, Michigan, USA, and have continued through the present. Research was conducted to determine whether Double-crested Cormorants were preying on smallmouth bass (Micropterus dolomieu) and causing a decline in this fishery. Breeding Double-crested Cormorant population estimates were recorded to document population dynamics before management and throughout the intensive control program, initiated in 2007. Research included studies using telemetry, raft surveys, banding, game cameras, and development of several bioenergetics models. In addition, co-nesting species were monitored to investigate impacts of Double-crested Cormorant control on non-target species. Results indicated that Double-crested Cormorants do not negatively impact smallmouth bass populations, co-nesters or other components of the system. However, control measures were initiated and continued through 2015; litigation ended control activities in 2016. Research suggested that control led to abandonment by Double-crested Cormorants of traditional colony sites, a switch from ground to tree nesting, and impacts on co-nesting species. This review demonstrates a significant disconnect between science-based knowledge and chosen management practices. Although court rulings ceased Double-crested Cormorant control, this disconnect should be addressed and remedied; science-based knowledge should be emphasized in any future management.

Lethal management of Double-crested Cormorants (Phalocrocorax auritus) has been implemented in many areas of the United States. In this paper, the philosophical method of argument analysis is used to assess ethical premises underlying the proposition that Double-crested Cormorant populations should be culled to reduce pressures on wild fisheries in the Great Lakes region of the eastern USA. This influential argument has been used to justify the destruction of more than half a million Double-crested Cormorants and hundreds of thousands of their nests and eggs. Three versions of the argument are formulated and assessed. It is shown that each of the arguments presupposes some form of anthropocentrism, an ethical stance considered by many in the scholarly community to be philosophically untenable and ethically inappropriate. It is suggested, consequently, that the arguments analyzed do not constitute an ethically sound basis for lethal management of Double-crested Cormorants in the Great Lakes region of the eastern USA.

Tree mortality incurred through the nesting habits of Double-crested Cormorants (Phalacrocorax auritus) can cause human-wildlife conflicts, often resulting in the lethal control of cormorants to reduce local population numbers in North America. In a protected area in Toronto, Ontario, Canada, that supports the largest colony of Double-crested Cormorants in North America, a non-lethal management approach to mitigate cormorant-induced tree mortality was adopted by the site managers in 2008. Double-crested Cormorants were managed for space occupancy rather than population size, with the main objective of minimizing tree mortality while supporting the cormorant population. Targeted non-lethal deterrence of tree-nesting Double-crested Cormorants was labor intensive, but effective in protecting trees. Between 2008 and 2016, the tree-nesting colony was prevented from expanding. Accessing ground-nesting Double-crested Cormorants only at night to avoid Larus sp. predation of Double-crested Cormorant nests appeared to be highly effective in minimizing disturbance; the ground-nesting colony expanded 899% over an 8-year period, with a 44% decrease in tree nesting. Ground-nesting Double-crested Cormorants had less impact on trees than tree-nesting individuals, and this spatially focused approach allowed for the sustained existence of a thriving colony.