Egret Egretta Research Articles

An investigation of the insect component in the diet of the Grey Heron Ardea cinerea and Little Egret Egretta garzetta

ABSTRACT Capsule Aquatic insects made up a relatively small part of the Grey Heron’s diet, while Little Egrets consumed numerous beetles, both aquatic and terrestrial. Aims To explore the extent of insect predation by Grey Herons and Little Egrets. Regurgitated pellets were collected from beneath trees in which herons and egrets were nesting. Methods Seventy Grey Heron and 48 Little Egret pellets were collected from the RSPB reserve at Northward Hill, Kent. These pellets were disaggregated and prey items were collected and sorted under a binocular microscope. Results Grey Herons fed on a relatively small number of aquatic beetles (Coleoptera: seven species, 32 individuals) and bugs (Hemiptera: two species, six individuals). Little Egrets, in contrast, fed on a diverse array of beetle species, both aquatic (three families, 11 species, 48 individuals) and terrestrial (10 families, 35 species, 111 individuals), and also a few aquatic bugs (one family, one species, three individuals). The extent of terrestrial beetles in the diet constitutes new information for Little Egrets. Conclusion Insects, both terrestrial and aquatic, represent an important component of the diet of Little Egrets. For Grey Herons, insects are a very minor component of the diet, involving aquatic species only.

Population Trend of Colonially Nesting Heron Species in Greece

Heron colonies are dynamic components of wetlands. Therefore, their systematic monitoring is important for the management of both birds and wetlands. During the period 1988–2018, we counted breeding pairs of seven colonial breeding heron species at 65 colonies across 37 wetlands in Greece. We considered as annual variables of a population: (a) years since 1988, (b) Natura 2000 network inclusion, (c) protected area management authority overseeing, (d) wetland type (new or restored), and (e) new colonies (established after 2003). The Cattle Egret Bubulcus ibis and the Squacco Heron Ardeola ralloides had a positive breeding population trend. The Black-crowned Night Heron Nycticorax nycticorax, Little Egret Egretta garzetta, and Grey Heron Ardea cinerea had a negative trend, while the Purple Heron Ardea purpurea population was stable. The Great White Egret Ardea alba bred sporadically at only a few sites which precluded the evaluation of its population trend. The informative population variables differed among species, even of those at the same colony, which suggests trends are also affected by conditions at wintering grounds. The study highlights the need for the systematic monitoring of heron colonies and the protection of foraging/breeding areas in order to reverse the observed negative population trends.

Waterbird community changes in the Wilderness Lakes, South Africa (Part 2 of 3): Shorebirds

Globally, many shorebirds, particularly the smaller migratory waders are declining, which can be attributed to multiple factors throughout their ranges. The Wilderness Lakes Complex in South Africa comprises two estuarine systems, that support diverse waterbird communities, including 17 abundant shorebirds. The study aimed to document long-term spatial and temporal patterns of abundance of shorebirds in the Wilderness Lakes Complex, and where possible identify potential causes for observed trends. The abundance of waterbirds on these wetlands was determined biannually from 1992 to 2019, with counts conducted from a boat following a standardised route. Historical abundance data from the 1980s were also used to describe long-term abundance changes. Ten shorebirds showed seasonal differences in abundances. Significant long-term decreases in abundance have occurred in seven shorebirds (Wood Sandpiper Tringa glareola, Marsh Sandpiper Tringa stagnatilis, Curlew Sandpiper Calidris ferruginea, Ruff Philomachus pugnax, Grey Heron Ardea cinerea, Greater Flamingo Phoenicopterus ruber, Black-winged Stilt Himantopus himantopus) and increases in three species (African Spoonbill Platalea alba, Little Egret Egretta garzetta, Glossy Ibis Plegadis falcinellus). Similar types of population changes occurred across multiple waterbodies and in different seasons. The similarity of shorebird abundance trends in spatially separated wetlands suggests either high interconnectivity of populations between wetlands systems and/or prominent drivers of change being broad scaled rather than system specific. Local reasons for changes potentially include the increasing spread of emergent macrophytes and resultant loss of open sandbanks, changing hydrodynamics, and alien fish proliferation, all likely changing food accessibility, as well as periodic high disturbance by waterbody users.Conservation implications: Changes in the abundances of several shorebirds, particularly small migratory waders, are substantial, with multiple likely local, regional and international drivers acting accumulatively. Recommended corrective actions include continuing involvement in the development and implementation of policies for waterbird conservation, and local management of emergent macrophytes, disturbance, and water level variability.

Spatial, temporal and trophic resource partitioning among the four egret species (Aves: Pelecaniformes: Ardeidae) in a tropical wetland ecosystem, India

The diversity of micro-habitats in tropical wetlands allows the coexistence of several species. These sympatric species interact with each other, either directly or indirectly, to optimally use the available resources. They achieve this through niche separation or minimal overlap to avoid competition. India’s wetland ecosystems are home to various sympatric species, such as the Great Egret Ardea alba (GE), Median Egret Ardea intermedia (IE), Little Egret Egretta garzetta (LE) and Cattle Egret Bubulcus ibis (CE). These egret species are closely related, and as a result, have similar niche requirements, which could lead to high intra-specific competition. However, there have been few studies on how these species utilize resources. This study aims to understand the possible mechanisms that enable the coexistence of these species in a tropical wetland. We have examined habitat characteristics, feeding behaviour, timings of seasonal and daily activities, and spacing patterns to evaluate possible models of species coexistence. We discovered that these four sympatric egret species have differences in microhabitat selection, activity patterns, both daily and seasonally, and feeding preferences. The study further indicates that there is a relationship between the niche dimensions, but it is only partially dependent on each other.

Drivers of partial migration in the reddish egret Egretta rufescens

The reddish egret Egretta rufescens is North America's rarest Ardeidae and is listed as ‘Near Threatened' by the IUCN, as endangered in Mexico, and as a species of conservation concern throughout much of its range in the United States. Little is known about the migratory behavior of the reddish egret. Individuals that were banded during the breeding season in Texas, USA, have been resighted away from breeding areas; however, records are limited and the extent of migration is unknown. Using GPS transmitters, we found reddish egrets breeding in southern Texas exhibited a partial migration strategy, with 39% of the marked population migrating from breeding sites. We assessed the dominance, body size, and arrival time hypotheses to better understand the drivers of partial migration. We did not find support for the body size hypothesis and found mixed support for the dominance hypothesis; both males and females migrated, and migratory status of individuals did not change across the years of study. Long‐distance migrants were also larger than resident individuals. We found some support for the arrival time hypothesis; residents began breeding earlier than long‐distance migrants and had moderately greater nest success. However, within long‐distance migrants, an earlier arrival to breeding areas did not necessarily equate to earlier nesting or greater nest success. This study is the first to examine the migratory behavior of adult reddish egrets and assesses the dominance, body size, and arrival time hypotheses as explanations for partial migration in this species. Further, the results of this study emphasize the need for international conservation efforts.

Full Migration Routes of Two Little Egrets (Egretta garzetta) Display Breeding and Wintering Site Fidelity

Our study provides the first GPS tracking data of Little Egret Egretta garzetta from an East Asian population. Our two main objectives were to reveal the migratory route and migratory strategy of Little Egret, and to study inter-annual breeding and wintering site fidelity. Our data, from an adult and a juvenile, suggest that this species is a short-distance high-speed migrant using few or no stopover sites. Both individuals displayed high breeding and wintering site fidelity. They also used very small winter home ranges, probably associated with high prey availability in aquaculture ponds.

Call rate as an index of nest count in wading bird colonies

Traditional monitoring methods for colonial waterbirds, such as nest counts, can be expensive, time‐intensive, disruptive to nesting birds and limited by colony accessibility. Our study tested the use of acoustic sampling as a colony monitoring technique for three species of colonially nesting herons (Ardeidae) by quantifying the relationship between chick call rate and nest count in colonies. Because acoustic detection can be influenced by soundscape variables, we measured day since colony initiation, body condition index of small heron chicks, nest height, vegetation density and wind speed and evaluated their effects on call rate detection. Generalized linear mixed‐effects models showed that call rate detection increased with daily nest count for all species. Snowy Egret Egretta thula and Tricoloured Heron Egretta tricolour detected call rate was also dependent on environmental, temporal and physiological variables, whereas Great Egret Ardea alba call detection was affected by vegetation density around nests and wind speed. Our study showed that wading bird nest counts can be estimated using acoustic sampling, reducing the need for manual colony surveys, and facilitating long‐term monitoring of wading bird nesting trends, which are important measures of wetland restoration worldwide.

First successful nesting of the Little Egret Egretta garzetta in Ghardaïa (Algerian Sahara)

We report on the first successful breeding of the Little Egret, Egretta garzetta, in the Sahara, Algeria. We conducted a study on the nesting of this species at Kef Doukhane, an artificial wetland in Northern Sahara that has become an increasingly important nesting site for waterbirds. The number of individuals was monitored between April and October 2021 and the greatest abundance with 470 individuals was recorded in October. However, during breeding, the colony decreased to about 50 birds that built seven nests. Egg-laying started at the beginning of July and at least 34 eggs were laid. Clutches varied between 5 and 6 eggs, and 28 nestlings fledged, yielding a breeding success of 82.4%.

Effects of Rice Field Phenology on Breeding Parameters of Heron Colonies in the East of the Iberian Peninsula

Rice fields have traditionally been considered key feeding grounds for many waterbird species, including herons. Studies show that field management and flooding cycles influence the reproductive parameters of these birds. L'Albufera de València, on the east coast of the Iberian Peninsula, has large areas of rice fields and is home to the third largest breeding colony of herons in Spain. Changes in water and rice field management that have occurred since the colony was last assessed (1990) may have affected the colony's reproductive performance. Clutch and brood size, and hatching, nesting and breeding success were estimated for Grey Heron Ardea cinerea, Purple Heron Ardea purpurea, Cattle Egret Bubulcus ibis, Little Egret Egretta garzetta, Squacco Heron Ardeola ralloides (Ardeidae) and Glossy Ibis Plegadis falcinellus (Threskiornithidae) in 2015–2017. The extent of flooding and cultivation of rice fields was assessed from February 2016 to June 2017. Reproductive parameters were related to the state of the rice fields. All reproductive output parameters were lower than those reported in the literature. In 2016, laying started earlier (at the end of April), when the fields were still dry and hatching started from May, after flooding. In 2017, peak hatching occurred in June, when the fields were sown. A significant relationship was found between breeding success and the area of sown fields, except for the Squacco Heron. We found that birds that initiated egg laying closer to the date of flooding had a relatively higher breeding success for the Little Egret, Glossy Ibis, Cattle Egret and Purple Heron. The success of nesting populations in this type of artificial wetland requires water management plans that synchronize flooding regimes and maintenance of flooded areas with the biological requirements of these species.

Autumn migration routes and wintering areas of juvenile Chinese Egrets (Egretta eulophotes) revealed by GPS tracking

BackgroundThe vulnerable Chinese Egret (Egretta eulophotes) is a long-distance migratory waterbird whose migration and wintering information is poorly understood. This study aims to identify the autumn migration routes and wintering areas of juvenile Chinese Egrets and determine the migration movement traits of this species.MethodsThirty-nine juvenile Chinese Egrets from the Fantuozi Island, an uninhabited offshore island with a large breeding colony of Chinese Egrets in Dalian, China, were tracked using GPS/GSM transmitters. Some feathers from each tracked juvenile were collected for molecular identification of sex in the laboratory. The GPS locations, recorded at 2-h intervals from August 2018 to May 2020, were used for the analyses.ResultsOf the 39 tracked juveniles, 30 individuals began their migration between September and November, and 13 successfully completed their autumn migration between October and November. The juveniles migrated southward via three migration routes, coastal, oceanic and inland, mainly during the night. The migration duration, migration distance, flight speed, and stopover duration of the 13 juvenile egrets that completed migration averaged 5.08 ± 1.04 days, 3928.18 ± 414.27 km, 57.27 ± 5.73 km/h, and 23.08 ± 19.28 h, respectively. These juveniles wintered in the coastal wetlands of Southeast Asia including those in the Philippines, Vietnam, and Malaysia, and only one successfully began its spring migration in June 2020.ConclusionsThis study newly finds that the oceanic route taken by juvenile Chinese Egrets, suggesting that the juveniles are able to fly over the Pacific Ocean without a stopover. Moreover, our novel data indicate that coastal wetlands along the East Asian–Australasian Flyway are important areas for both autumn migration stopover and the wintering of these juveniles, suggesting that international cooperation is important to conserve the vulnerable Chinese Egret and the wetland habitats on which it depends.

ĐA DẠNG THÀNH PHẦN LOÀI CHIM Ở VƯỜN CHIM ĐÀO MỸ, HUYỆN LẠNG GIANG, TỈNH BẮC GIANG

The study on Dao My Stork Garden with an area of 3 hectares located in Tan Phuc village, Dao My commune, Lang Giang district, Bac Giang province during 2017 - 2018 has identified 32 bird species belonging to 29 genera, 18 families, 7 orders, including 21 resident species, 11 winter migratory species. There is one species listed in the Vietnam Red Data Book (2007) which is Anastomus oscitans. There are 6 species of water birds living and colony nesting in the stork garden: Little Egret (Egretta garzetta), Chineses pond Heron (Ardeola bacchus), Egret Cattle (Bubulcus coromandus), Black-crowned Night Heron (Nycticorax nycticorax), Intermediate Egret (Egretta intermedia) and Asian Openbill (Anastomus oscitans). The water bird species with the highest number of population in breeding season is the Little Egret. There is a stratification of the habitat and nesting areas of water birds according to the vegetation in the stork garden. Birds mainly nest and live on eucalyptus and bamboo trees. Since this stork garden formed on the land is owned by the household, in order to preserve the stork garden for sustainablity, it is necessary to support from the local government and organizations to invest in the restoration of trees in the garden and protecting the stork garden from illegal bird hunting.

Impacts of Great Cormorant and Cattle Egret Nesting on Other Waterbirds in a Shared Breeding Site in Piedmont (NW Italy)

Some waterbird species are believed to have an impact on other waterbird species as they are able to usurp a limited habitat and destroy vegetation. In this study, we have analysed the nesting dynamics of five waterbird species: Grey Heron Ardea cinerea, Great Cormorant Phalacrocorax carbo, Little Egret Egretta garzetta, Black-crowned Night Heron Nycticorax nycticorax and Cattle Egret Bubulcus ibis, that had settled in a colony in the Royal Castle Park of Racconigi (Cuneo, NW Italy) over a 17-year period (2000 to 2017). The Great Cormorant and the Cattle Egret settled in the colony in 2008 and 2012, respectively. We analysed the relationships between the number of breeding pairs of the five species. In addition, we used the time series forecasting method to study the nesting dynamics and the impact of the new settlements on the pre-existing colony. The number of nests of the Great Cormorant and the Cattle Egret increased annually, and these species significantly affected the nesting trends of the other pre-existing species: Grey Heron, Black-crowned Night Heron and Little Egret. The Grey Heron mainly suffered from the occupation of its old nests by the Great Cormorant from 2008 to 2013. However, since 2014, the Grey Heron has been able to react, by displacing its breeding site to the tops of trees adjacent to the old heronry, and this has resulted in an even greater number of nests than before 2008. The Black-crowned Night Heron and the Little Egret suffered more from the settlement of the new species than the Grey Heron did, and started to suddenly or gradually abandon the breeding site. The colony has been modified profoundly by the settlement of the Great Cormorant and the Cattle Egret, and it is still subject to dynamics that could transform it in the coming years.

The Okavango Delta’s waterbirds – Trends and threatening processes

The Okavango Delta is renowned as an extraordinary ecosystem of high biodiversity, listed as both a Ramsar and World Heritage Site, with part protected in the Moremi Game Reserve. This extensive floodplain ecosystem has 444 recorded bird species, with just under a quarter of these waterbirds, including at least 16 breeding and 4 threatened (1 endangered, 3 vulnerable) species. Despite the global importance of this ecosystem, and its transboundary nature, there are surprisingly few long-term assessments of status of the ecosystem or waterbird communities, a key indicator of ecosystem health, with threats such as upstream water extraction, and climate change threatening its outstanding biodiversity. We compiled a comprehensive 53-year dataset comprised of citizen science and other datasets (1970–2019), on 36 waterbird species (Anhingidae, Ardeidae, Ciconiidae, Gruidae, Pelecanidae, Phalacrocoracidae, and Phoenicopteridae), including eight waterbird breeding colonies in the Okavango Delta. We investigated trends in waterbird biodiversity as well as responses to temperature, flow, flooding, and local rainfall. Waterbird breeding colonies were associated with relatively high areas of riparian woodland, and experienced moderate flooding frequencies (> 1 in 5 years). Total abundance of all 36 waterbird species was positively related to river flows. Despite increased citizen science effort over time, total abundance within the Okavango Delta significantly declined with declining average inundation. Four species led these declines (African darter Anhinga rufa, green-backed heron Butorides striata, slaty egret Egretta vinaceigula, squacco heron Ardeola ralloides) and one marabou stork Leptoptilos crumenifer, increasing (only sufficient data to analyse 15 species individually). Decreased inundation within the Delta and other internal factors (urbanisation, tourism, vegetation change) as well as external factors (habitat loss elsewhere) are likely driving these declines. Rigorous monitoring of waterbirds, including the eight breeding colonies across the Delta, is needed to explore these changes closely, providing baselines in the case of water resource developments on the rivers supplying the Okavango Delta. Long-term conservation of the magnificent Okavango Delta and its dependent biodiversity, including its waterbirds, is highly reliant on protection of river flows in three countries to ensure natural flooding regimes, alongside the conservation of neighbouring wetlands.

Comparative Analysis of Heavy Metal Accumulation Pattern and Genotoxicity in Water Fowl

Waterfowl spend their lives mostly on water bodies include ducks, geese, and swans, also include birds such as coots, grebes, moorhens, shorebirds and seabirds etc. Wetlands in Pakistan offer habitat to a variety of migratory birds. Bird’s diversity facing problems due to loss of natural habitat and hunting causing serious issues to bird’s territories. Objective: To investigate bioaccumulation of heavy metals and genotoxicity in waterfowl. Methods: This study investigated bioaccumulation of heavy metals and genotoxic effects that could result from exposure of waterfowl to heavy metals in the Chenab River, Punjab, Pakistan. The three different species, common teal (Anas crecca), little egret (Egretta garzetta) and mallard (Anas platyrhynchos) were obtained from head Marala, River Chenab. The liver, kidneys, heart, muscle, blood, and feathers of birds were collected for the purpose of determining the presence of heavy metals. The study investigated the most common heavy metals Pb, Cd, Ni, and Cr indicating higher concentrations of heavy metals in blood and feathers from the study site. At study sites Pb Cr, Ni concentrations were high (P ≤ 0.05). Results: The results in the current study revealed metals concentration in different species trend as Anas crecca > Egretta garzetta > Anas platyrhynchos. The deposition of heavy metals in organ trends as Pb>Cr>Ni>Cd. The level of metals in blood trends as Pb>Cr>Ni>Cd. Metal concentrations in feathers trend as Pb>Cr>Ni>Cd. Conclusions: Expression analysis of anti-apoptosis Bcl-2 made for Egretta garzetta and genotoxicity results showed that the effect of metals in study groups found negative for the expression of the Bcl2 gene.

Three-dimensional niche partitioning between two colonially nesting ardeid species in central China

BackgroundInterspecific competition is known to be strongest between those species that are both closely related and sympatric. Egrets are colonially nesting wetland birds that often overlap and can therefore be expected to compete in roosting and nesting habitat as well as in diet. According to the niche partitioning hypothesis, it is to be expected that these similar species would show differentiation in at least one of the main niche dimensions to reduce competition. We tested niche partitioning between the colonially nesting Little Egret (Egretta garzetta) and Cattle Egret (Bubulcus ibis) in temporal, spatial and trophic dimensions.MethodsField study was conducted in three mixed egret colonies in Yangxian County, southwest Shaanxi Province, central China. For each nest colony we recorded its spatial location, the height of nesting trees and of nests, the height of roosting trees and of roosting individuals within the trees. We determined the first egg-laying and first hatching dates of the two species. Craw dissection of storm-killed egret nestlings was used to measure the diet. Six transects were surveyed to study foraging habitat selection.ResultsWe found that hatching time of Little Egrets peaked earlier (by about 1 month) than that of Cattle Egrets. Cattle Egrets nested and roosted higher than Little Egrets. The foraging habitats used by Little Egrets were dominated by river banks (73.49%), followed by paddy fields (13.25%) and reservoirs (10.84%), whereas Cattle Egret foraging sites were characterized by grasslands (44.44%), paddy fields (33.33%) and river banks (22.22%). Little Egrets consumed more fishes (65.66%) and Odonata larvae (13.69%) than Cattle Egrets, while Cattle Egrets were found feeding mainly on Coleoptera (29.69%) and Orthoptera (23.29%). Little Egrets preyed on larger mean biomasses of food items than Cattle Egrets.ConclusionsOur results confirm the niche partitioning hypothesis as a mechanism for coexistence among ecologically similar species. In two coexisting egret species, niche partitioning is multidimensional, such that the two coexistent species occupy differing ecological space based on all three temporal, spatial and trophic niche dimensions.

KEANEKARAGAMAN JENIS BURUNG DI CAGAR ALAM PULAU DUA, BANTEN

Pulau Dua Nature Reserve (CA) is a conservation area and one of the Important Bird Areas (IBA), which is a habitat for various bird species. The condition of the habitat ecosystem in Pulau Dua CA is currently experiencing disturbances and damage so that biodiversity, including bird species, is disturbed. This research was conducted to determine the diversity of bird species in various habitats in Pulau Dua CA. The method used is a survey with Point Transect on the type of habitat for ponds, mangrove forests, and coastal areas. Based on the results obtained, 31 bird species from 18 families were observed that can be found in Pulau Dua CA. A total of 27 bird species are permanent residents and 4 birds are migrant species. The highest species diversity index (H ') value of the three habitat types was found in 2.62 ponds including the very good category (2.59 <H' <2.62) which means that the condition of the community structure is still very stable, the highest evenness index (E) in ponds 0.95 (high), and the highest dominance index (D) on the coast 0.13 (low). The highest species abundance is in coastal and pond habitats, namely large egrets (Egretta alba), while in the mangrove forest habitats are sea remetuk birds (Gerygone sulphurea) and striped kipasan (Rhipidura javanica).

Unravelling diet composition and niche segregation of colonial waterbirds in a Mediterranean wetland using stable isotopes

Rice fields and waterbirds are an example of a synergy that can occur between agriculture and conservation. This connection is especially relevant during the farming period, when nesting waterbirds need to obtain resources to cover their energy requirements and those of their chicks in rice fields. However, new farming techniques may potentially put fulfilling this role at risk. Studies on how species use rice fields to feed during this critical period are essential to understand waterbird population dynamics and to optimize conservation measures. At present, several species of colonial birds in l’Albufera de València (Spain) that depend on trophic resources available in rice fields have decling populations and decreases in productivity. We therefore assessed trophic niche segregation in the diet of chicks of a waterbird community composed of seven species through stable isotope analyses of carbon (δ13C) and nitrogen (δ15N) obtained from chick blood and tissue samples of potential prey. According to trophic niche widths, chicks of Black‐headed GullChroicocephalus ridibundusand Gull‐billed TernGelochelidon niloticashowed a similar diet, although Gull‐billed Tern had a major trophic specialization. The Western Cattle EgretBubulcus ibisfed its chicks in a wider range of different habitats, with organisms located at the base of the food chain and with a greater importance of terrestrial prey than other species. Conversely, the Glossy IbisPlegadis falcinellushad a more differentiated diet, mostly in freshwater habitats and mainly consuming odonates. Grey HeronArdea cinerea, Little EgretEgretta garzettaand Squacco HeronArdeola ralloidesshowed overlap between their niches, largely explained by the presence and abundance of cyprinid fish and odonates in their diets. Our results suggest a less important role than expected of Red‐swamp CrayfishProcambarus clarkii, and a more important role of odonates despite being a less energy‐rich prey. In conclusion, the diet of generalistic species of waterbirds in this study suggests that their trophic niches can overlap when relative prey abundance is high.

Primer development of toll-like receptor genes in the vulnerable Chinese egret (Egretta eulophotes) and its applicability in Ardeidae

Toll-like receptor (TLR) genes have recently been used to assess the adaptive genetic diversity under natural selection. Here, we newly developed a set of primer pairs for amplifying TLR genes (TLR1LB, TLR2A, TLR3, TLR4, TLR5, TLR7 and TLR15) in the vulnerable Chinese egret (Egretta eulophotes). The PCR products, ranged between 407 and 988 bp (an average of 762 bp), were successfully amplified by using this primer set. Sequence analyses of all these TLR genes indicated that there were 22–75 variable sites and 20–77 single nucleotide polymorphisms. This primer set was also confirmed useful for nine other ardeid species, including four members in ardeinae and five in botaurinae. The versatility of this primer set will provide a useful groundwork for the further studies on the TLR conservation genetics of this vulnerable egret and other ardeid birds.

Evidence of Low-Habitat Contamination Using Feathers of Three Heron Species as a Biomonitor of Inorganic Elemental Pollution.

The concentration of 12 elements (As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn) has been investigated in the feathers of three species of Ardeidae, namely the Grey Heron Ardea cinerea, the Little Egret Egretta garzetta, and the Cattle Egret Bubulcus ibis, all breeding at a colony located in the southern Padana Plain (NW Italy). This study is a first step for an evaluation of possible direct effects of these elements on chicks’ survival and growth rate. Fe, Zn, Cu, and Mn were in the range 7–69 mg Kg−1, while lower levels of Pb, Ni, As, and Se (0.27–1.45 mg Kg−1) were measured. Co, Cd, and Cr were close to the method detection limits (MDLs) in all the species. The measured concentrations of the most abundant trace elements, such as Zn and Cu, seem to reflect the geochemical pattern of the background (running water and soil), while Hg concentration is lower and it appears to be biomagnified, particularly in Grey Heron feathers. Its concentration is higher in adults than in chicks, and it differs among the three species, as it is closely related to the fish-based dietary pattern. The measured trace elements’ concentrations are below the threshold levels in all the heron species, and consequently, harmful and acute effects on the local population are unlikely; the conservation status of herons populations in northern Italy is probably more affected by other factors, such as climate changes, altered aquatic environment, and, consequently, food quality.

Sibling competition in the broods of Little Egrets Egretta garzetta in a southern Tunisian breeding colony

Asynchronous hatching is a common hatching pattern in the Little Egret Egretta garzetta, however, its role in maintaining dominance relationships and feeding hierarchy among siblings remains poorly studied. In this study, we investigated this issue using data on feeding and aggressive behaviours of Little Egrets nestlings in a southern Tunisian breeding colony. We found that senior nestlings were the first to access the food brought by their parents, and they ingested more food than their younger siblings did. Intermediate nestlings engaged the most frequently in aggression. The youngest nestlings showed a more resigned and less aggressive behaviour, therefore receiving a little less food, but much fewer pecks and injuries than their elders do. These findings stress the importance of hatching order in establishing a feeding hierarchy among Little Egret siblings. Moreover, they suggest that access to food may not be the unique factor that shapes nestlings’ feeding behaviour and competitiveness, as the avoidance of injuries caused by siblings’ attacks may be important. Finally, adult birds appeared to adopt a ‘laissez faire’ strategy, showing no feeding favouritism to counteract or reinforce the effects of hatching asynchrony on their offspring.