Heron Species Research Articles

Effects of Nesting Bald Eagles (<i>Haliaeetus leucocephalus</i>) on Behaviour and Reproductive Rates in a Great Blue Heron (<i>Ardea herodias</i>) Colony in Ontario

Bald Eagles (Haliaeetus leucocephalus) and Great Blue Herons (Ardea herodias) are known to occasionally nest in mixed colonies, even though the former is one of the primary predators of the latter. I observed the two species in four heron colonies near Lake Simcoe, Ontario during two field seasons to assess whether rates of heron chick mortality or nest abandonment were greater in a colony that supported a nesting pair of Bald Eagles than in three nearby single-species colonies. I assessed the effects of eagle presence on heron behaviour using heron movement rates, the number of heron sentries left in colonies during the nesting period, heron nest mortality rates, and the average number of successfully fledged herons per nest. There was no statistically significant difference in movement rate among the four colonies, proportion of birds remaining as sentries, nor nest mortality rates. However, nests in the mixed colony successfully fledged significantly more heron young per nest than did nests in the single-species colonies. The mixed colony was located in a wetland and open lake system that provided extensive foraging habitat and an abundance of the preferred fish prey species of both Great Blue Herons and Bald Eagles, thus reducing predation pressure on the herons.

Hidden carotenoids in the powder down of herons

Vivid plumage colors are some of the best examples of elaborate trait evolution resulting from sexual selection. Bird feathers often contain high concentrations of pigment or intricate microstructures for reflecting light at distal feather tips, in order to maximize color presentation to intended viewers (e.g., prospective mates, rivals). However, here we describe a rare form of “hidden” plumage coloration, whereby several species of heron (Pelecaniformes: Ardeidae) have powder down tracts liberally coated in yellow pigments that are hidden from view underneath contour feathers. We show using Raman spectroscopy and high-performance liquid chromatography that the yellow coloration is due to carotenoid pigmentation. We also show that fatty acids and carotenoids co-occur in samples and discuss the possible evidence and implications for the presence of esterified carotenoids in powder down. Our study of hidden feather coloration is in apparent contrast with the traditional view of carotenoid pigmentation in plumage, which holds that carotenoids are costly pigments that are displayed to advertise individual quality. We hypothesize that carotenoid pigments are transferred onto powder down as a consequence of the chemical affinity that these pigments have to lipoid secretions associated with subcutaneous fat. Further investigation may identify functions for carotenoid pigmentation in powder down (e.g., signaling, microbiological protection), but we cannot rule out the possibility that the powder down of herons may provide the first evidence for carotenoid coloration in feathers being a non-adaptive by-product of other processes.

Detection and characterisation of coronaviruses in migratory and non-migratory Australian wild birds

We evaluated the presence of coronaviruses by PCR in 918 Australian wild bird samples collected during 2016–17. Coronaviruses were detected in 141 samples (15.3%) from species of ducks, shorebirds and herons and from multiple sampling locations. Sequencing of selected positive samples found mainly gammacoronaviruses, but also some deltacoronaviruses. The detection rate of coronaviruses was improved by using multiple PCR assays, as no single assay could detect all coronavirus positive samples. Sequencing of the relatively conserved Orf1 PCR amplicons found that Australian duck gammacoronaviruses were similar to duck gammacoronaviruses around the world. Some sequenced shorebird gammacoronaviruses belonged to Charadriiformes lineages, but others were more closely related to duck gammacoronaviruses. Australian duck and heron deltacoronaviruses belonged to lineages with other duck and heron deltacoronaviruses, but were almost 20% different in nucleotide sequence to other deltacoronavirus sequences available. Deltacoronavirus sequences from shorebirds formed a lineage with a deltacoronavirus from a ruddy turnstone detected in the United States. Given that Australian duck gammacoronaviruses are highly similar to those found in other regions, and Australian ducks rarely come into contact with migratory Palearctic duck species, we hypothesise that migratory shorebirds are the important vector for moving wild bird coronaviruses into and out of Australia.

A fossil heron from the early Oligocene of Belgium: the earliest temporally well‐constrained record of the Ardeidae

We describe the earliest temporally well‐constrained fossil that can be assigned to the Ardeidae (herons), from the lowermost Oligocene (32.0–33.0 million years ago) of Belgium. The specimen, a partial tarsometatarsus, belongs to a small species and is described as Proardea? deschutteri n. sp. It exhibits the characteristic tarsometatarsus morphology found in extant heron species, but a confident assignment to one of the ardeid subclades is not possible and even the assignment of the new fossil species to the crown group (the clade including the extant species) cannot be established. The fossil indicates a divergence of herons from their sister taxon by at least the earliest Oligocene, and current paleontological data suggest that herons arrived in Europe shortly after a major faunal turnover at the Eocene/Oligocene boundary. We consider that dispersal is the likely reason for the sudden appearance of herons in the earliest Oligocene of Europe but it is uncertain from where exactly this took place, with Asia and Africa being among the candidate areas.

Differences in diversity and habitat use of avifauna in distinct mangrove areas in São Sebastião, São Paulo, Brazil

Mangroves are an important ecosystem for many bird species for breeding, roosting and feeding, but habitat use depends on the area and vegetation structure. Avifaunal diversity studies are essential to establish baseline knowledge, identify impacts on communities, and for the effective management of ecosystems, especially in coastal areas under intense anthropogenic pressure. In this study, we: 1) characterized the mangrove vegetation structure on a former landfill (Ferry's site) from the expansion of São Sebastião Port, on the southeast coast of Brazil, 2) compared bird richness, abundance, and seasonal diversity of waterbirds and terrestrial birds at Ferry's site, with four sites located on natural land at Araçá Bay, a small semi-enclosed coastal bay, and 3) analyzed birds' habitat use. Ferry's site and Araçá Bay both border the port in the São Sebastião municipality. Overall, 52 bird species were detected in Ferry's site and 78 species in Araçá Bay. The waterbird community showed a higher average richness, abundance, and diversity in Ferry's site (A1) than in the Araçá sites (A2-A5). There were significant differences in these variables among sites, but not among seasons. For terrestrial birds, average richness and diversity were higher at Ferry's site, but average abundance was higher at Araçá Bay. These differences may be explained by habitat heterogeneity in the areas, however no pattern in these variables was found among A2-A5, because A5 has less human traffic and has more edge vegetation, which attracts birds. Ferry's site was used mainly for roosting throughout the year and as a breeding site for four heron species in summer, whereas Araçá Bay was used mainly as a foraging ground for waterbirds. Differences in habitat use were probably due to the higher density and maximum height of mangrove vegetation at Ferry's site, even though mangroves of Araçá Bay had a greater structural development. Furthermore, Araçá Bay has a large tidal plain, with high invertebrate diversity, which could explain why waterbirds used it mainly for foraging. This study highlights the importance of mangrove in the life cycle of several bird species and their aggregation. Therefore, protection of these coastal habitats should be prioritized in conservation measures.

Dietary Segregation of Four Ardeid Species Breeding in Anzali International Wetland, Northern Iran

Abstract. The nestling diets of four heron species breeding on a small forestry islet in Anzali, Iran, were investigated to determine the dietary segregation among sympatric breeders. Regurgitated samples from Black-crowned Night-Herons (Nycticorax nycticorax), Little Egrets (Egretta garzetta), Cattle Egrets (Bubulcus ibis) and Squacco Herons (Ardeola ralloides) were collected during the breeding season from 23 May to 16 August 2016. A total of 1,606 prey items were identified representing 39 prey categories from nine different classes. Differences were detected among these four ardeid species for the percentage of each prey category. Fish dominated the regurgitates of the Blackcrowned Night-Heron (67%; n = 43 samples), Little Egret (45%; n = 33 samples) and Squacco Heron (53%; n = 10 samples), whereas arachnids and insects combined (53% and 40%, respectively, based on total number of individuals) and insects (61.9% based on weight) were the most common prey items for the Cattle Egret. Although fish items...

Evaluation of methods for molecular sex-typing of three heron species from different DNA sources

Genetic markers are a useful tool for bird population monitoring, especially when combined with ringing data, and particularly so in vulnerable species. This study compared the effectiveness of two DNA extraction methods: a standard protocol and a commercially available kit. The molecular sex-typing was performed using PCR-based methods with a 2550F/2718R set of primers in three species of herons: Great Egret, Purple Heron, and Grey Heron. Genomic DNA was isolated from feathers, eggshells, and eggshell swabs from 26 individuals. Overall, better DNA yields and purity were obtained by using the standard protocol isolation method. The highest DNA yield was obtained from the pin feathers compared to the contour feathers and eggshells, both of which had lower yields. Eggshell swabs indicated possible contamination with parental/sibling DNA. Our evaluation demonstrates that the optimization of laboratory procedures is beneficial, particularly when different types of noninvasive tissue samples are available.

Studies on the Wetland Biodiversity and Conservation with reference to Habitat, Prey Abundance and Foraging by Two species of Herons

Kerala is the one of the green states of India and is well known for its wetlands. The present study is based on abundance of food and foraging by two species of herons (median egret and large egret) in different type of wetland habitats of Malappuram, Palakkad and Kozhikode districts, Kerala, India. Both the large egret and median egret are piscivorous. During non-breeding season the most preferred habitat of large egret (Egretta alba-37.44%) and median egret (Egretta intermedia-62.56%) are the coastal area and riverine habitats. During breeding season they prefer human habitation with close proximity of riverine habitats and lakes where they build their nests. Utilisation of different habitats, various foraging strategies employed by the species, threats to the wetland in the study area and need for their conservation are also highlighted.

A Puzzling Case of Successful Double-Brooding in the Little BitternIxobrychus m. minutus

The Little Bittern is one of the least studied heron species in its breeding range. The nominate, Palaearctic race Ixobrychus m. minutus has been generally assumed to be single-brooded only, yet detailed studies of its breeding biology and mating system are lacking. The present paper provides the first observational evidence of successful double-brooding in the nominate race of the Little Bittern and gives the first record of time-overlapping double-brooding in the species. Potential determinants of this breeding strategy as well as the frequency of its occurrence are discussed.

Helminth communities of herons (Aves: Ardeidae) in southern Italy

The helminth communities of nine species of herons from southern Italy were studied and compared. Of 24 taxa found including seven digeneans, seven nematodes, six cestodes and four acanthocephalans, only five taxa were found in more than one heron species, and five of the 21 taxa that could be identified to species level were classified as ‘heron specialists’. The total number of helminth species per heron species ranged from 1 in Botaurus stellaris to 9 in Ixobrychus minutus with infection levels generally low. A statistical comparison was carried out for herons with a sample size >5. At the infracommunity level, only I. minutus clearly differed from other heron species. Diversity parameters of heminth infracommunities did not significantly differ among heron species. Species richness ranged from just 0.3 to 2.3 helminth taxa per individual host, and the Brillouin index, from 0 to 0.3. Total helminth abundance did not exceed 40 worms per host except in a single case of Ardeola ralloides. Infracommunities clearly were dominated by single helminth species. The present study confirms a depauperate helminth community in herons from southern Italy. Comparison with data from Spain and the Czech Republic showed strong quantitative similarities with values obtained in the present study. Results also suggest that the composition of local helminth communities are strongly variable depending on geographical location as is demonstrated by comparison with data from other European areas. However, whether herons in Europe naturally host depauperate helminth communities or these communities are depauperate because of other factors is unknown.

Influence of diet in the accumulation of organochlorine compounds in herons breeding in remote riverine environments

The composition of organochlorine compounds (OCs), pentachlorobenzene (PeCB), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), DDTs and polychlorobiphenyls (PCBs), has been analyzed in eggs from cattle egret (Bubulcus ibis) and little egret (Egretta garzetta), two species of herons (family Ardeidae), nesting at the same remote riverine environment (Aiguabarreig, Ebro River). These two species were selected to evaluate the importance of diet in the accumulation of OCs. Cattle egret essentially feeds on dry grassy habitats and follow cattle or other large animals whereas little egret feeds on fish, amphibians and crustaceans captured in shallow waters. The δ(15)N and δ(13)C isotopic composition of the sampled eggs was studied and the results were consistent with these species feeding habits. In both species, the compounds accumulated the most were the less volatile and more lipophilic, e.g. PCB congeners of higher chlorination, DDT and metabolites. The distinct foraging species preferences were reflected in significant higher concentrations in little egret than cattle egret of all pollutant groups analysed. These differences were statistically significant for DDTs and PCBs (p < 0.015 and p < 0.047, respectively), e.g. the p,p'-DDE and PCB concentrations were 6 and 4.5 times higher, respectively, in the former than the latter. This strong contrast indicates that in remote environments aquatic riverine ecosystems are more efficient OC reservoirs than the terrestrial ecosystem.

Avian Malaria is Absent in Juvenile Colonial Herons (Ardeidae) but notCulex pipiensMosquitoes in the Camargue, Southern France

Apicomplexan blood parasites Plasmodium and Haemoproteus (together termed “Avian malaria”) and Leucocytozoon are widespread, diverse vector-transmitted blood parasites of birds, and conditions associated with colonial nesting in herons (Ardeidae) and other waterbirds appear perfect for their transmission. Despite studies in other locations reporting high prevalence of parasites in juvenile herons, juvenile Little Egrets (Egretta garzetta) previously tested in the Camargue, Southern France, had a total absence of malaria parasites. This study tested the hypotheses that this absence was due to insufficient sensitivity of the tests of infection; an absence of infective vectors; or testing birds too early in their lives. Blood was sampled from juveniles of four species shortly before fledging: Little Egret (n = 40), Cattle Egret (Bubulcus ibis; n = 40), Black-crowned Night-Heron (Nycticorax nycticorax, n = 40), and Squacco Heron (Ardeola ralloides; n = 40). Sensitive nested-Polymerase Chain Reaction was used to test for the presence of parasites in both birds and host-seeking female mosquitoes captured around the colonies. No malaria infection was found of in any of the heron species. Four different lineages of Plasmodium were detected in pooled samples of female Culex pipiens mosquitoes, including two in potentially infective mosquitoes. These results confirm that the absence of malaria parasites previously demonstrated in Little Egret is not due to methodological limitations. Although the prevalence of infection in mosquitoes was low, conditions within the colonies were suitable for transmission of Plasmodium. These colonial heron species may have evolved strategies for resisting malaria infection through physiological or behavioral mechanisms.

Variación en el tamaño de los huevos en garzas (Aves: Ardeidae) que anidan en la ciénaga de Birama, Cuba

Intraclutch egg size variation in birds depends on many ecological factors and on the evolutive history of each species. In wading birds, a trend to smaller eggs with laying order has been described, but comparative reports are scarce. In this study, egg size variation patterns were described for nine Egrets and Heron species nesting in Birama' Swamp, Cuba. The patterns were described using external dimensions of 3142 eggs from 1875 nests of Butorides virescens, Bubulcus ibis, Ardea alba, Nycticorax nycticorax, Nyctanassa violacea and four Egretta species, taken in the field between 1998 and 2006. Results showed that eggs were 4.9-10% of adult weight and had volume variation coefficients between 6-9%. There were no general and consistent interspecies relationship between clutch size and egg sizes. Average volumes tend to get smaller with laying order, but it is not statistically detectable in Butorides and Bubulcus. Last egg was between 0.2% and 15% smaller than the first, showing an inverse relationship with it. Intraclutch asymmetry is light in E. thula and fluctuating around null in Bubulcus. Size only predicted laying or hatching order for the last egg, in nests with more than two eggs, with 72.4% of confidence.

Anatomical investigation on the appendicular skeleton of the cattle egret (Bubulcus ibis)

Introduction: The Cattle Egret (Bubulcus ibis) is a cosmopolitan species of heron (family Ardeidae) found in the tropics, subtropics and warm temperate zones. It is the only member of the monotypic genus Bubulcus. Cattle egret is popular for its role in the bio-control of cattle parasites and land pests. Materials and Methods: The present study was conducted on five adult, apparently healthy, cattle egrets. The birds were euthanized and the skeletons were prepared by the cold maceration method. Results: The appendicular skeleton of the cattle egret consists of the pectoral (shoulder) girdle and appendage, and pelvic girdle and appendages. The pectoral girdle comprises the long flat scapula, coracoid bone, and the united paired clavicles. Canalis triosseum is a canal formed by the attachment of the three bones of the pectoral girdle. The furcula formed fi brous connection with the sternum. The radius and ulna have the same length. The wrist comprises two carpal bones, carpometacarpus and three digits. The pubic bones are not fused ventrally. The pes consists of tibiotarsus, tarsometatarsus and four pedal digits. The tibiotarsus is longer than the femur. The spur is not found in the male bird. Conclusion: The skeleton of the cattle egret has a unique conformation that accommodates its ability to flight as well as being an insectivorous animal.

Grey Heron (Ardea cinerea) Expansion Promotes the Persistence of Mixed-Species Heron Colonies

Range expansion of native as well as exotic species often causes effects on the original species; however, not all range expansions are negative for breeding colonies consisting of mixed species. The Grey Heron (Ardea cinerea) has increased and expanded its distribution in Japan in the last 20 years. Its solitary and early nesting habits may facilitate establishment and persistence of colonies of mixed heron species. To examine whether the addition of Grey Herons has affected colony persistence and the number of established and abandoned colonies, 16 years of monitoring data from before and after the expansion of Grey Herons around Ibaraki Prefecture in Japan were analyzed. Most newly established colonies were without Grey Herons before their expansion, but more than half of the established colonies contained Grey Herons after the expansion. The number of colony abandonments decreased after the Grey Heron expansion and most of these occurred in colonies that were without Grey Herons both before and after the expansion. Persistence periods were longer in colonies with Grey Herons than in colonies without Grey Herons. The expansion of Grey Herons into mixed heron colonies has promoted the persistence of mixed heron colonies, and local populations of colonial herons seemed to gain the benefit of colony sustainability.

Comparison of trace element concentrations in grey heron and black-crowned night heron chicks.

Cadmium (Cd), lead (Pb), manganese (Mn), zinc (Zn), and iron (Fe) concentrations were measured in the prey and liver of grey heron (Ardea cinerea) and black-crowned night heron (Nycticorax nycticorax) chicks (24-26 days after hatching) at the Pyeongtaek colony, Korea in 2001 (n = 10, respectively) and 2008 (n = 11 and n = 10). Cadmium and Pb concentrations in livers of grey heron (Cd geomean 0.06, Pb 3.90 μg/g dw) and black-crowned night heron (Cd 0.20, Pb 4.24 μg/g dw) chicks were increased with diet concentrations of grey heron (Cd 0.18, Pb 1.76 μg/g dw) and black-crowned night heron (Cd 0.20, Pb 3.96 μg/g dw) chicks. Cadmium and Pb concentrations in prey items of grey heron and black-crowned night heron chicks were a good predictor of chick liver concentrations. Cadmium concentrations in livers of both heron species collected at the Pyeongtaek heronry were relatively low and within the background level (<3 μg/g dw) for birds. Five of 20 (25.0%) grey heron and 4 of 18 (22.2%) black-crowned night heron chicks were higher than the background level for lead (>6 μg/g dw). Prey Cd and Pb concentrations were within the range of other heron and egret studies. Manganese, Zn, and Fe concentrations in grey heron and black-crowned night heron chicks were within the background or normal physiological levels reported earlier in other birds including herons and egrets.

Concentrations of Cd, Pb, Mn and Zn in feathers and diet in heron chicks in Korea.

The feathers and diet items of grey heron (Ardea cinerea) and black-crowned night-heron (Nycticorax nycticorax) chicks were collected at the Pyeongtaek colony, Korea in 2002 and 2008, and Cd, Pb, Mn and Zn concentrations were measured. Cd and Zn concentrations were higher in both species in 2008 than 2002 and were higher in grey herons than black-crowned night-herons in 2002. In 2008, Cd concentrations were higher in black-crowned night-herons than grey herons; Zn concentrations did not differ between species. Pb and Mn concentrations did not differ between species; however, there were yearly differences. Cd, Pb and Zn concentrations of feathers and diet were significantly correlated when species and years were combined. However, the predictive power of these relationships was limited because of species and yearly differences. All heron chicks had concentrations of Cd (<2 μg/g dw) and Pb (<4 μg/g dw) consistent with background concentrations for wild birds. Mn and Zn concentrations were within the range reported for other heron and egret species.

Long-term changes in the food resources of a guild of breeding Ardeinae (Aves) in Italy

The breeding herons and egrets in northwestern Italy derive a large portion of their food resources from rice fields. In order to investigate the possible effects of changes in rice cultivation techniques on the trends of the breeding population of these birds, we studied their diet and the prey availability in rice fields, and we compared the results for 2013 with the situation in past decades, by taking advantage of similar investigations conducted by our research team since 1978. The diet of five species of herons and egrets changed sharply after 1995, with the bulk of the diet now made up of completely new prey species, in particular the allochthonous Louisiana crayfish and Oriental weatherfish, that only recently colonized our study area, and with a lower frequency of the amphibians that were a staple prey before 2000, but whose abundance in rice fields has declined. Since 2000, the decrease in the populations of some breeders, particularly the most abundant Grey Heron and Little Egret, has coincided with their sharp change in diet, with the reduced availability of amphibians and with the diminished availability of flooded rice fields. However, the proportion of food resources obtained from rice fields versus the natural habitats remained high, or was only slightly lower for some predator species. Several issues remain open about the value of rice fields in supporting the foraging herons and egrets, and about the effect of changing agricultural techniques on the bird population. We need to assess more accurately the proportion of food obtained from rice fields, and to check whether the foraging herons and egrets can satisfy their energy requirements while foraging in agroecosystems.

Factors Influencing Behavior and Success of Foraging Reddish Egrets (Egretta rufescens)

The Reddish Egret (Egretta rufescens) is the rarest and least studied species of heron in North America and is a species of conservation concern throughout its range. Foraging behavior and foraging success of the Reddish Egret were studied by focusing on whether their foraging behavior or success varied with age, color morph, group size, and habitat measures. Foraging individuals (n = 372) were video-recorded in the Laguna Madre of Texas, USA, from March 2008-April 2010. Adult Reddish Egrets were 30–250% more successful foragers than juveniles, and groups were 32–44% more successful foragers than solitary foragers. Foraging success was similar between color morphs. The more specialized foraging behaviors of canopy feeding, wing flicking, and foot-stirring had the highest success, but were employed infrequently. Four environmental variables (wind speed, light intensity, water depth, and percent seagrass coverage) were found to influence foraging success, but accounted for only 3% of the variation in foraging behavior. Our results suggest that environmental variables have little influence on foraging behavior of Reddish Egrets in the Laguna Madre, and we suggest that characteristics of the prey have a stronger influence. An understanding of how environmental variables influence foraging behavior and success may allow us to better assess habitat quality or possibly aid in identification of highly productive foraging sites and allow for more targeted conservation actions to those habitats that promote high foraging success.

Lead and cadmium contaminations in feathers of heron and egret chicks

In birds, concentrations of heavy metal contaminants were associated with their diet and environmental quality. This study presents concentrations of lead and cadmium in feathers and the relationship between concentrations in the feather and stomach content of three species of heron and egret chicks. Cadmium concentrations were higher in the Little Egret (geomean 0.75 μg/g dry weight) and Black-crowned Night Heron (geomean 0.88 μg/g dry weight) chicks than in Grey Heron chicks (geomean 0.48 μg/g dry weight). Lead and cadmium concentrations had significant correlations between feathers and stomach contents of heron and egret chicks. The mean lead and cadmium concentrations in feathers were within the background levels for wild birds. Heron and egret species forage around breeding colony (4-7 km). Lead and cadmium concentrations in heron and egret chicks were moderately associated with those of prey concentrations. These results suggest that contaminant concentrations such as lead and cadmium in feathers of heron and egret chicks can reflect local heavy metal contaminations and serve as a great biological indicator for monitoring heavy metal contamination. In addition, the feathers can be a routine monitoring tool over time and space without harming the wild birds.