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Understanding the trophic interactions and coexistence processes among waterbirds in floodplain ecosystems is of fundamental ecological importance. In the upper Paraná River floodplain, we assessed the diet of five sympatric waterbird species (Ardea alba, Ardea cocoi, Egretta thula, Nannopterum brasilianum, and Nycticorax nycticorax) and tested their differences in the diet, in addition to food overlap, differences in trophic niche breadths and stratum in the water column where they forage. The waterbirds’ stomachs were collected quarterly on the upper Paraná River floodplain, analyzed under a stereomicroscope, and the food items were identified. Only Egretta thula was classified as omnivorous, consuming various food resources, including insects, decapods, and fish. The other species were piscivorous, but differed in the types of prey. Food overlap was higher in the piscivorous species, but they exhibited high trophic niche breadth. The piscivorous waterbirds employ different strategies for exploiting food resources that allow species coexistence in the floodplain, avoiding direct competition. Our results highlight the importance of waterbirds as connectors across diverse environments, especially aquatic-terrestrial ecosystems. Since these waterbirds’ diet relies on fish, effective conservation and management strategies targeting fish communities are fundamental to maintaining biodiversity and functionality within the upper Paraná River floodplain.

Twelve models addressing the current and delayed effects of seasonal rainfall and rainfall volatility (a measure of storm intensity) were used to evaluate changes in nest abundances of herons and egrets in the San Francisco Bay area, from 1991 to 2010. Wetter- or drier-than-average conditions, two winters before nesting, were associated with reduced growth rates of Great Egret (Ardea alba) nest abundance. Similarly, growth rates of Great Blue Heron (Ardea herodias) nest abundance were maximized near average levels of rainfall volatility two winters prior nesting. Annual growth rates of Snowy Egret (Egretta thula) and Black-crowned Night-Heron (Nycticorax nycticorax) abundances declined with heavier-than-usual winter rainfall volatility immediately prior to nesting and with increases in spring rainfall volatility 2 years prior to nesting. The dynamics of heron and egret nest abundances were not associated with annual production of fledglings within the region, The results suggest the possibility of regional declines in the growth or resilience of heron and egret abundances with increasingly rainy or stormy seasonal conditions in northwestern California.

Herons typically reproduce colonially, either monospecific or mixed, over waterbodies, high in trees or shrubs, mangroves, and islands. Information from neotropical mangroves is lacking concerning heron breeding areas, reproductive biology, and functional relationships with mangroves. Here we compared the reproductive biology of Cattle Egret ( Bubulcus ibis ), Little Blue Heron ( Egretta caerulea ), and Snowy Egret ( E. thula ), with emphasis on breeding season, nesting materials, nest height, clutch size, breeding success, and nest failure in a mangrove ecosystem in ​​Sepetiba Bay, southeastern Brazil. The breeding season lasted from November to mid-February (195 nests). Nests were built mostly with twigs, but also with grasses (17 nests, 9%) and nylon lines and ropes (Cattle Egrets: 16 nests, 28%; Snowy Egrets: 4 nests, 14%). Little Blue Herons nested higher (2.25 ± 0.1 m) than Cattle Egrets (1.97 ± 0.06 m) and Snowy Egrets (1.80 ± 0.1 m). The modal clutch size differed among species, with two eggs in Cattle Egrets (1–7 range) and Little Blue Herons (1–4 range) and three eggs in Snowy Egrets (2–4 range). Breeding success was high both in Cattle Egrets (90%) and Snowy Egrets (89%) but was low in Little Blue Herons (41%). Higher nest failure in Little Blue Herons occurred due to localized predation events in all clumped nests built isolated at the colony edge. Therefore, these predation events suggest that interspecific nest aggregation was important to diminish nest failure. The remaining nests were quite successful, even though brood reduction (common in herons) occurred in most nests.

Wetland conservation often involves creating hydrological regimes that maximize habitat and resources for wildlife. In the greater Everglades ecosystem in Florida, USA, where wading birds are food-limited in some years, models predicting the influence of hydropatterns on foraging habitat availability are used to guide the management of water levels for wading bird nesting populations. These models are useful but do not consider that nesting wading birds are central place foragers, and thus resource availability is a colony-level measure. We examined long-term nest abundance patterns of the great egret (Ardea alba), snowy egret (Egretta thula), and white ibis (Eudocimus albus) to determine effects of hydropatterns on wading bird nest abundance in a 400-km² littoral marsh in Lake Okeechobee, Florida. We developed 2 sets of statistical models for each species: 1 examining variation in nest abundance (1977–1992, 2006–2019) and 1 predicting colony-level nest abundance (2006–2019). Models of nest abundance predicted that great egret nesting will peak when March–April lake stage is 4.3–4.5m, coinciding with the peak in area of available foraging habitat. Neither recession rate nor stage explained total snowy egret or white ibis nest abundance, though snowy egret nest abundance has increased since the 1990s, when the water management schedule favored higher lake stages for longer duration. For all species, colony-level models predicted that nesting increased with increased habitat availability, faster water-level recession rates, and greater number of days dry in the previous 2 years at nest sites. When applied to simulated hydrological data representing changes to water-level regulations in Lake Okeechobee, our models predicted that management regimes allowing extreme flooding (stage > 5.18m) in <220 days per 5.0 years and Carolina willow (Salix caroliniana) recruitment (stage < 3.9m) >3.0 years per 5.0 years resulted in the highest nest abundance for snowy egret and white ibis. Snowy egret and white ibis nesting decreased by 575 nests/year and 465 nests/year, respectively, when regulation schedules increased the management envelope by 0.46 m, whereas great egret nest abundance increased modestly (149 nests/year). Operational rules that allow intermediate drought disturbance in dry years and prioritize increased habitat availability at short-hydroperiod colonies in wet years should result in overall benefits to the wading bird community at Lake Okeechobee.

ABSTRACT Establishing a link between food availability and productivity is often central to the recovery of declining populations; however, differences in prey selection may influence how populations are affected by changes in prey availability. We determined prey selection and prey availability for 3 wading bird species, and investigated the effects of prey availability on the number of nests initiated by 6 wading bird species in the Florida Everglades, USA. To determine prey selection, we compared food items recovered from tricolored heron (Egretta tricolor), snowy egret (Egretta thula), and little blue heron (Egretta caerulea) nestlings to aquatic prey availability from throw‐traps across the Everglades landscape from 2012 to 2014. Tricolored heron and snowy egret prey composition was statistically similar across years, with the majority of prey biomass coming from relatively large (>1.9 cm) marsh fish. Little blue heron prey composition differed from the other wading bird species, and contained a higher percentage of grass shrimp (Palaemonetes paludosus) and exotic fish species. Numbers of small heron nests were positively influenced by the availability of large marsh fish across the landscape, whereas numbers of nests for other wading bird species (wood stork [Mycteria americana], great egret [Ardea alba], white ibis [Eudocimus albus]) were not. Our results suggest differences among wading bird species in their prey selection and availability. Although small heron foraging may seem restricted by their specialization on marsh fishes, their short nesting cycles allow for the phenological flexibility to delay nesting until foraging conditions are optimal. Conversely, wood storks with longer nesting cycles are more temporally constrained but have greater flexibility in prey items and foraging range. The annual number of small heron nests may be more robust to hydrological variability as a result of management action or global change than the number of wood stork nests. The temporal constraints of nesting by wood storks indicate that management of supporting wetland systems should provide continuous habitat availability during the nesting season. © 2016 The Wildlife Society.

Ecological facilitation (mutualism and commensalism) appears to be a strong force shaping biotic communities, and may be more likely in stressful and dynamic environments like wetlands. We examined a specific type of mutualism, ‘protective nesting associations,’ between herons and egrets ( Ardeidae ) and American alligators ( Alligator mississippiensis ). We predicted that wading birds would be attracted to sites with alligators. A survey of potential nesting sites in the Everglades showed strong nonrandom association, with wading birds never nesting without alligators. At previously unoccupied nesting colony sites, we experimentally manipulated apparent densities of alligators and birds using alligator and bird decoys. Small day-herons (little blue herons ( Egretta caerulea ), tricolored herons ( Egretta tricolor ), and snowy egrets ( Egretta thula )) were significantly more numerous at sites with both alligator and bird decoys than other treatments. These findings together support the hypothesis that wading birds actively choose predator-protected nesting locations based in part on information from both conspecifics and alligators, and suggest that the mechanism supporting this habitat choice is primarily due to nest protection benefits the alligators inadvertently provide. We propose that this interaction is strong and could be geographically widespread, and suggest that it may be critical to shaping management and conservation of wetland function.

At 460 hectares, the Paul Sarbanes Environmental Restoration Project at Poplar Island, Talbot County, Maryland, represents the largest \"beneficial use\" dredged material project of the U.S. Army Corps of Engineers (a cooperative project with Maryland Port Administration). Begun in 1998, the 15-year restoration project will ultimately consist of roughly 220 ha of uplands and 220 ha of tidal wetland habitats, with limited areas of dike roads, perimeter riprap, and unvegetated mudflats. Wetland restoration began in one small section (or \"cell\") in 2002, but not all cells will be filled with dredged material until at least 2013. As a major objective of the restoration, six species of waterbirds were identified as \"priority species\" for Chesapeake Bay: American black duck ( Anas rubripes ), snowy egret ( Egretta thula ), cattle egret ( Bubulcus ibis ), osprey ( Pandion haliaetus ), common tern ( Sterna hirundo ), and least tern ( S. antillarum ). Monitoring of nesting activities of these species from 2002 to 2005 indicated that all species except black ducks colonized the site rapidly. More than 800 pairs of common terns nested in 2003 to 2004. Because of predation by red fox ( Vulpes vulpes ) and great horned owl ( Bubo virginianus ), reproductive success was very low for the terns. Trapping was effective in removing the foxes, and other controls have been applied to opportunistic nesting species including herring gulls ( Larus argentatus ) and Canada geese ( Branta canadensis ). An effective public education program on the island has helped address concerns about animal control. Keywords: American black duck ( Anas rubripes ), common tern ( Sterna hirundo ), dredged material, island restoration, least tern ( S. antillarum ), osprey ( Pandion haliaetus ), snowy egret ( Egretta thula ), waterbirds

Few studies on pelecaniform breeding have been conducted in tropical regions. Most species in the Order Pelecaniformes (Family Ardeidae and Threskiornithidae) are facultative brood reduction strategists, laying extra-eggs that might not fledge. In obligate brood reduction in birds, extra-eggs are insurance-eggs, but in facultative brood reduction birds, extra-eggs have historically been interpreted as additional offspring in unpredictable environments. However, this study on six species in Brazil suggests that the insurance-value might be a major factor selecting for extra-egg laying, even in facultative strategists. While Egretta thula, E. caerulea, E. tricolor, Nycticorax nycticorax, and Nyctanassa violacea showed facultative brood reduction strategies, Eudocimus ruber showed a brood survival strategy and was used to compare brood reduction parameters between strategies. Mean brood size in different species ranged from 1.94-2.52 eggs, 1.88-2.25 hatchlings, and 1.65-2.05 fledglings. Clutch sizes were between two and three in brood reduction species, and almost always two in E. ruber, which either raised the entire brood or totally failed. Individual mortality events in non-failed nests were lower in E. ruber. This difference occurred only during the egg stage, when starvation does not occur, so differences between strategies resulted from an insurance-value of extra-eggs. Nest failures were higher in E. ruber. Insurance could be the main force driving evolution of extra-egg laying in facultative species, with survival of additional offspring a collateral benefit.

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.

Wetlands provide numerous ecosystem functions such as water purification, nutrient cycling, and wildlife habitat. Avian populations are indicators of wetland health, and understanding their responses to extreme events can aid in targeting restoration efforts following disturbance. Here, we assessed the habitat selection of six coastal wetland bird species (American Bittern, Black-crowned Night Heron, Great Egret, Glossy Ibis, Snowy Egret, Yellow-crowned Night Heron) related to an extreme weather event, Hurricane Sandy. We used Discrete Choice Resource Selection Functions to estimate habitat selection. Results showed species probability of use increased with lower elevation and slope, and closer proximity to marsh, salt marsh, Phragmites , and protected areas. Estimates of marsh dieback from Hurricane Sandy occurred disproportionately in areas with higher probability of species use. Species were observed farther from the coast and at higher elevations in the four breeding seasons after (2013–2016) compared to before (2000–2012) Hurricane Sandy. Our results indicate that although high suitability areas were affected by the storm, these six wetland bird species may have responded by moving inland and to higher elevation. Understanding how coastal wetland birds respond to storm events is important for conservation planning, particularly as storm frequency is projected to increase in the future.