Explore the vast range of titles available.

Polymorphism has been described in many avian taxa including Ardeidae. This study investigated the spatio-temporal distribution of color polymorphic forms (with regard to the color of the unfeathered parts (legs/lores)) of the Great White Egret Ardea alba alba in internet images from Europe. In total, 140 images of presumed polymorphs from 16 countries (from 2006 to 2021) have been collected and examined. Eight coloration schemes of visible unfeathered parts were distinguished. Since some polymorphs may represent the subspecies Eastern Great Egret Ardea alba modesta, the ratio of beak length to total head length was compared among individuals representing the nominal and Eastern Great Egret subspecies. The ratio distributions were similar in all compared groups; thus, polymorph egrets may represent both of these subspecies. Most polymorph images originate from the Netherlands and the southwestern Norwegian coast. This may have resulted from specific local diets and contact with hormone-disrupting compounds. Nevertheless, some observation biases, such as the presence of local breeding population or high numbers of nature photographers, could have affected our observation pattern. Some analyzed features also followed temporal patterns. Most polymorphs were observed during the breeding season, suggesting disruptions of sex hormones as a possible cause. Studies of spatio-temporal patterns of polymorph occurrence may allow us to obtain insights into the causes of large variation in coloration schemes in polymorphic species.

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.

Rice fields are important wildlife habitats; however, intensive agricultural practices have reduced the population of farmland birds. As a high-level consumer, the great egret ( Ardea alba ) serves as an indicator of the overall biodiversity of rice fields. However, little is known about the effects of farming methods on the feeding habitat selection of the great egret. Therefore, we examined the influence of eco-friendly and conventional farming methods on prey characteristics and great egret feeding behavior in rice field ecosystems. We employed focal observations and trap-based sampling to quantify prey characteristics and great egret feeding behaviors in eco-friendly and conventional rice fields. Great egrets showed more hunting attempts per minute and a higher intake rate in conventional fields, but feeding efficiency did not differ. Moreover, they consumed larger loaches in eco-friendly fields than in conventional fields. Great egrets exhibited slower feeding behaviors in eco-friendly fields due to the increased handling time of larger prey, such as loaches. Eco-friendly fields supported a higher abundance of larger-sized loaches than conventional fields, indicating their potential for supporting a higher abundance of great egrets. Our findings highlight the importance of sustainable farming practices for the conservation of the great egret.

Movement by animals to obtain resources and avoid predation often depends on natural cycles, and human alteration of the landscape may disrupt or enhance the utility of different habitats or resources to animals through the phases of these cycles. We studied habitat selection by GPS/accelerometer-tagged great egrets ( Ardea alba ) foraging in areas with shellfish aquaculture infrastructure and adjacent natural wetlands, while accounting for tide-based changes in water depth. We used integrated step selection analysis to test the prediction that egrets would express stronger selection for natural wetlands (eelgrass, tidal marsh, and other tidal wetlands) than for shellfish aquaculture areas. We also evaluated differences in foraging behavior among shellfish aquaculture areas and natural wetlands by comparing speed travelled (estimated from distance between GPS locations) and energy expended (Overall Dynamic Body Acceleration) while foraging. We found evidence for stronger overall habitat selection for eelgrass than for shellfish aquaculture areas, with results conditional on water depth: egrets used shellfish aquaculture areas, but only within a much narrower range of water depths than they used eelgrass and other natural wetlands. We found only slight differences in our metrics of foraging behavior among shellfish aquaculture areas and natural wetlands. Our results suggest that although great egrets appear to perceive or experience shellfish aquaculture areas as suitable foraging habitat during some conditions, those areas provide less foraging opportunity throughout tidal cycles than natural wetlands. Thus, expanding the footprint of shellfish aquaculture into additional intertidal areas may reduce foraging opportunities for great egrets across the range of tidal cycles. Over longer time scales, the ways in which natural wetlands and shellfish aquaculture areas adapt to rising sea levels (either through passive processes or active management) may change the ratios of these wetland types and consequently change the overall value of Tomales Bay to foraging great egrets.

Living shorelines (LSs) increasingly are implemented as a defense against coastal erosion and rising seas; however, their ecological function for wading birds has not been evaluated. Here, we compared heron and shorebird use of LSs (created fringe salt marshes with a wave break fronting the planted marshes) to natural‐fringe marshes (NFMs) in the Chesapeake Bay. We assessed the use between May and August in 2018 and 2019 at 13 tidal marsh pairs, each consisting of one LS and NFM site, with sites within pairs having similar surrounding land use and wave exposure. In each year, we assessed diurnal use with video cameras recording at least four 30‐min segments/day for a total of 677 h of video, and nocturnal/diurnal use with acoustic recording equipment recording 10‐min sound files every 2 h/day for a total of 160 h of recording. We quantified diurnal use by measuring the total time a species spent at a site, and nocturnal/diurnal use by estimating the probability of detection (i.e., presence/absence). We detected four heron and five shorebird species when data were aggregated across pairs and sampling methods. Using Bayesian mixed models, time of use did not differ between LS and NFM sites for great blue herons (Ardea herodias) and yellow‐crowned night‐herons (Nyctanassa violacea). In contrast, time of use was higher for green herons (Butorides virescens) and spotted sandpipers (Actitis macularis) at LS sites but tended to be higher for great egrets (Ardea alba) at NFM sites. The probability of detection did not differ between LS and NFM sites for great blue herons and great egrets (combined as “Ardea spp.” due to difficulty in differentiating calls under noisy conditions), yellow‐crowned night‐herons, and spotted sandpipers. Green herons and killdeer (Charadrius vociferous), however, tended to be detected more frequently at LS sites. Collectively, our research indicates that LSs are functionally equivalent to NFMs for herons and shorebirds. We hypothesize that the low‐profile rock sills of LS provide platforms for resting and preening and offer prey even when vegetated marshes are unavailable to short‐legged species during flooding tides. In addition to their established reduction of coastal erosion, LSs provide habitat for herons and shorebird species.

Abstract The composition of assemblages, diet and behavior of waterbird species with similar ecological features are important aspects in the functioning of aquatic ecosystems. Closely related animal species often share resources such as space and food in ways that reduce competition, but if the diets of different species strongly overlap, interspecific competition may intensify. This analysis examined behavioral data relating to Great Egret, Little Egret, and Squacco Heron to explore their foraging efficiencies in rich aquatic habitats in an arid zone during post-breeding movements. The fieldwork was carried out in small estuaries of a Wadi on the southern coast of Oman. The frequency of interactions was the highest in Squacco Heron and the lowest in Great Egret. However, the differences in the numbers of inter- and intra-specific interactions between the 3 species were significant. Activity indices calculated for a 5-min period, i.e., the number of interactions (interaction index) and times of flying and walking (movement index) differed among the 3 species. The number of successful attacks was the highest in Squacco Heron, while the foraging effectiveness of Great Egret and Little Egret was similar. GLM analysis showed that only the movement index was significant, as it had a positive impact on individual foraging success. Great Egret caught more fish than the other 2 heron species which, in turn, caught a greater number of smaller prey items, mostly invertebrates. This study shows that heron species in the same rich habitat employ different foraging tactics. In comparison to the other two heron species, the foraging tactics of Squacco Heron seem to be the most susceptible to competition. However, its greater mobility and using different foraging tactics, enhance its foraging success.

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.

Background Previous studies on the tick infestation of birds in the Carpathian Basin focused on songbirds (Passeriformes). Thus, the primary aim of the present work was to extend the scope of previous studies, i.e. to include aquatic (water-associated) bird species in a similar context, especially considering that these birds are usually long-distance migrants. Methods Between March 2021 and August 2023, 11,919 birds representing 126 species were checked for the presence of ticks. From 352 birds belonging to 40 species, 905 ixodid ticks were collected. Tick species were identified morphologically and/or molecularly. Results Ticks from avian hosts belonged to seven species: Ixodes ricinus ( n  = 448), I. frontalis ( n  = 31), I. festai ( n  = 2), I. arboricola ( n  = 36), I. lividus ( n  = 4), Haemaphysalis concinna ( n  = 382) and Dermacentor reticulatus ( n  = 2). Nymphs of I. ricinus occurred with a single activity peak around March–May, whereas its larvae typically infested birds in May, June or July. By contrast, H. concinna usually had its activity maximum during the summer (nymphs in June–July, larvae later in July–August). Interestingly, two ornithophilic species, I. frontalis and I. arboricola , were most active around winter months (between October and April). A significantly lower ratio of aquatic birds was found tick-infested than songbirds. Several new tick–host associations were revealed, including I. ricinus from Greylag Goose ( Anser anser ) and D. reticulatus from Great Egret ( Ardea alba ) and Sedge Warbler ( Acrocephalus schoenobaenus ). Ticks were collected for the first time in Europe from two species of predatory birds as well as from Little Bittern ( Ixobrychus minutus ). Bird species typically inhabiting reedbeds were most frequently infested with H. concinna , and most ticks localized at their throat, as opposed to forest-dwelling avian hosts, on which I. ricinus predominated and ticks were more evenly distributed. Conclusions In the evaluated region, aquatic birds appear to be less important in tick dispersal than songbirds. However, newly revealed tick-host associations in this category attest to their hitherto neglected contribution. The results suggest that the habitat type will have significant impact not only on the species composition but also on the feeding location of ticks on birds. Graphical Abstract

Double-crested cormorants (Phalacrocorax auritus) and great egrets (Ardea alba) have an extensive history of human-wildlife conflict with the aquaculture industry of western Mississippi, USA, due to their depredation of cultured catfish (Ictalurus spp.). Although aquaculture is abundant, western Mississippi also contains naturally occurring water bodies that offer alternative forage opportunities to these species. How cormorants or egrets distribute themselves among these 2 foraging options is unknown, but it has been generally assumed each species uses aquaculture disproportionately more because of the high density of available prey. To test this assumption, we surveyed these species on aquaculture and naturally occurring water bodies using aerial surveys from October through April of 2015–2016, 2016–2017, and 2017–2018. We modeled the proportion of each species on aquaculture as a function of year, date, and weather-related variables using quasi-binomial generalized linear models. Egrets used aquaculture consistently more than what was proportionally available to them and use was not influenced by any of the variables we measured. Proportional use of aquaculture by cormorants was lowest during October through January but steadily increased through April, indicating a distribution shift toward aquaculture in the months immediately prior to their migration. The highest proportional use of aquaculture by cormorants occurred in 2016, a year when lethal control measures were not allowed against cormorants. Conversely, the least proportion of cormorants on aquaculture was in 2015 when cormorants could be lethally controlled under authority of an Aquaculture Depredation Order. This trend highlights the potential influence of changes in mortality risk, caused by changes in policy regarding lethal take of cormorants, on cormorant distribution between foraging options.

Productivity of avian populations provides important demographic information helpful in understanding population dynamics and processes involved during species expansions. We tested the hypothesis that the productivity of the two species of ecologically similar herons that breed together in mixed heronries is related to their expansion status. We expected the expansive species, colonizing the new area and increasing in numbers, to outperform the native species, whose abundance is stable. We studied the breeding success of two herons in mixed colonies in eastern Poland in 2018: Great Egret (Ardea alba) (an expansive species, increasing breeding range and population size), and the Grey Heron (Ardea cinerea) (a native species, stable breeding population). Mean productivity (number of young per nest) was similar for Great Egret and Grey Heron and appeared correlated to each other in mixed heronries. Productivity of both species was unrelated to the colony size, but Grey Heron tended to have higher productivity as the proportion of Great Egret nests in the colony increased. Similar productivity of both species can be explained by the sufficient food resources coupled with the low level of competition. The two species differed significantly in their response of young to the approaching drone: the mean probability of a young Great Egret adopting an upright display was 0.47 compared to only 0.18 in a young Grey Heron (p=0.025). This was unlikely an age-related difference as the fledglings of both species were at a similar stage of development, but may represent some kind of a species-specific trait. Our research once again shows that UAVs allow a quick and non-invasive study of the size of the breeding populations and reproductive performance of herons, egrets and other wading birds.