Breeding success of the colonist species Bubulcus ibis (Linnaeus, 1758) and four native species

This work evaluated the breeding success of Bubulcus ibis (Ardeidae), Egretta thula, Nycticorax nycticorax, Phimosus infuscatus and Plegadis chihi in Rio Grande do Sul during two consecutive nesting seasons. Mean clutch size for B. ibis was 2.59 in 1998/1999 and 2.49 in 1999/2000. The species with both the smallest and largest clutch was P. infuscatus, with 2.04 in 1999/2000, and 3.16 in 1998/1999. The highest mean number of nestlings per nest was 2.86 for P. chihi in 1998/1999 and the lowest was 1.85 for B. ibis in 1998/1999 and P. infuscatus in 1999/2000. In both nesting seasons all the species had major success, laying three eggs and raising two nestlings, exept for B. ibis. The breeding success for P. chihi varied from 1.54 young/nest in 1998/1999 to 0.4 in 1999/2000, whereas B. ibis ranged from 1.16 in the first period to 0.99 in the second.     

Vertical nest stratification of four heron species in southern Brazil

Herons generally breed in mixed flocks and their nests are made in shrub wetlands and on islands. Waterbirds can select different tree species in the heronries which can influence the vertical stratification of the heron nests. The aim of the present study was to determine the vertical nest stratification among four Ardeidae species in heronries in southern Brazil. The study was carried out during four breeding seasons between 2004 and 2009. No significant species-specific difference in mean nest height was observed between the three heronries. However, there was some variation in nest heights per species in the four years of the study and among the heron species. Nest height was correlated with the body size of the heron species. The smaller species, Bubulcus ibis, Egretta thula, and Nycticorax nycticorax, occupied mainly the lower stratum and the largest, Ardea alba, the higher stratum. The colonist species B. ibis did not show a clear preference, occupying both Mimosa bimucronata and Cephalanthus glabratus for nest building, while the other three herons selected mainly M. bimucronata if the two tree species were available.     

Feeding ecology of the waterbirds in a tropical mangrove in the southeast Gulf of Mexico

ABSTRACT

Species that exploit the same type of environmental resources are defined as a guild, which have similar needs in the use of food or habitat. It was analyzed the diet of five waterbirds’ offsprings species (Neotropic Cormorant (Nannopterum brasilianus), Reddish Egret (Egretta rufescens), Boat-billed Heron (Cochlearius cochlearius), Snowy Egret (Egretta thula) and Great Egret (Ardea alba)), by prey identification and calculated the relative importance, overlap and breadth diet. The general diet of the piscivorous guild consisted of 17 fish species from 13 genera and eight families. The highest overlap was between the Reddish Egret and Boat-billed Heron. Fish species dominated the diets of all studied waterbirds, Poecilia velifera was the most abundant prey species in each of the birds, suggesting that they are abundant in the wetlands system of northern Yucatan. Diet overlap in waterbirds species depends on the use of resources and feeding habitat. Since reproductive success largely depends on the availability of food resources, mainly of resident or estuarine fishes. The information about diet is important for the conservation of waterbirds.     

Compared distribution within a disturbed fishpond ecosystem of breeding ducks and bird species indicators of habitat quality

The distribution of breeding ducks versus three other bird species (Mute Swan Cygnus olor, Black-headed Gull Larus ridibundus and Purple Heron Ardea purpurea) among waterbodies was investigated in the Dombes area, Eastern France, where breeding duck populations have undergone a severe decline following a large-scale transformation of meadow habitat into cropland. Higher Pochard Aythya ferina, Tufted Duck Aythya fuligula, Red-crested Pochard Netta rufina and Gadwall Anas strepera pair densities were recorded in fishponds where Black-headed Gulls were nesting. In these ponds however, nesting success (assessed by the number of broods divided by the number of pairs) was not significantly higher. Similarly, Pochard pair density was higher in ponds with a Purple Heron colony, but brood densities were not. We hypothesise that, in the study region, clutch concentration in the most attractive areas could compensate for the anti-predation effect of gull colonies or overwater nesting in shore vegetation. We could not confirm the expected negative impact of Mute Swan aggressive behaviour on duck distribution. Even though Mallard Anas platyrhynchos pair density was lower in ponds with breeding swans, we did not observe difference for Mallard broods. Moreover, Red-crested Pochard pair density and nesting success were higher in ponds where swans were breeding, probably as a consequence of shared habitat preferences.     

The helminth infracommunities in three species of herons (Aves: Ardeidae) from Ukraine

This survey analysed the helminth communities associated with three Ukrainian heron species (Ardea cinerea, Ardea purpurea, Nycticorax nycticorax) collected throughout 1947–2019. The sample analysed included 128 specimens, and 55 helminth species were identified. Of these, the most diverse taxonomic group was trematodes with 29 species, followed by cestodes with 14 species, nematodes with nine, and acanthocephalans with three species. The helminth infracommunities were found to be similar across all three host species. Furthermore, the distance to the coastal regions impacts both diversity and species richness in infracommunities.     

Size specific predation by herons and its effect on the sex-ratio of natural populations of the mosquito fish Gambusia affinis baird and girard

Summary Sex-ratios of Gambusia affinis populations in freshwater marshes in the Camargue (Rhône Delta), are highly biased in favour of males, whereas the sex-ratios in ditches are close to unity. Studies of the diet of free living birds and experimental studies on prey size selection in captivity show that the abnormal sex-ratios in marshes can be attributed to differential heron predation. Ditches are relatively free from predation. Mature female Gambusia are larger, and have an energy content 5–25 times greater than that of mature males. Handling times of Grey Heron (Ardea cinerea) and Little Egret (Egretta garzetta) are only slightly longer for female Gambusia than males. Hence, females represent a much more profitable prey.Analysis of nestling regurgitates show that Gambusia makes up a considerable proportion of the diet of four species of Camargue herons, and that the majority of Gambusia taken are females. Under experimental conditions, captive herons consume almost exclusively female fish, even when offered in ratios where they are heavily outnumbered by males.The relevance of these results to optimal diet theory is discussed.     

Waterbirds (other than Laridae) nesting in the middle section of Laguna Cuyutlán, Colima, México

Laguna de Cuyutlán, in the state of Colima, Mexico, is the only large coastal wetland in a span of roughly 1150 km. Despite this, the study of its birds has been largely neglected. Between 2003 and 2006 we assessed the waterbirds nesting in the middle portion of Laguna Cuyutlán, a large tropical coastal lagoon, through field visits. We documented the nesting of 15 species of non-Laridae waterbirds: Neotropic Cormorant (Phalacrocorax brasilianus), Tricolored Egret (Egretta tricolor), Snowy Egret (Egretta thula), Little Blue Heron (Egretta caerulea), Great Egret (Ardea alba), Cattle Egret (Bubulcus ibis), Black-crowned Night-heron (Nycticorax nycticorax), Yellow-crowned Night-heron (Nyctanassa violacea), Green Heron (Butorides virescens), Roseate Spoonbill (Platalea ajaja), White Ibis (Eudocimus albus), Black-bellied Whistling-duck (Dendrocygna autumnalis), Clapper Rail (Rallus longirostris), Snowy Plover (Charadrius alexandrinus), and Black-necked Stilt (Himantopus mexicanus). These add to six species of Laridae known to nest in that area: Laughing Gulls (Larus atricilla), Royal Terns (Thalasseus maximus), Gull-billed Terns (Gelochelidon nilotica), Forster's Terns (S. forsteri), Least Terns (Sternula antillarum), and Black Skimmer (Rynchops niger), and to at least 57 species using it during the non-breeding season. With such bird assemblages, Laguna Cuyutlán is an important site for waterbirds, which should be given conservation status.     

Co-breeding involving herons and a potential egg predator,the Indian House Crow (Corvus splendens), in Peninsular India

Association between species may strengthen the fitness of the species involved It is not rare that avian species associate on the breeding and feeding grounds. However, a species associated with a potential egg predator is less common. In this study, a synchronized breeding of Indian House Crow (Corvus splendens) and breeding Indian Pond Herons (Ardeola grayii) in urban conditions is reported. Both the crow abundance and the crow nest abundance increased with the number of heronry nests on sites. Crows were mostly observed when flying over or when resting nearby, but they also attempted egg predation from heronry nests. Crows also used the heronry sites for collecting nesting resources, such as twigs, scavenging dead chicks and for stealing the food brought to feed the heronry chicks. A dearth of suitable nesting places and provisions in an urban environment may be the reason why these birds share nesting trees. Vigilant breeding crows, despite their ability to depredate heron nests, may be more beneficial to herons as they are known to mob and distract heron predators, but a full cost-benefit analysis needs to be undertaken.     

RANGE EXPANSION AND MIGRATION OF THE CATTLE EGRET

Maddock, M. & Geering, D. 1994. Range expansion and migration of the Cattle Egret. Ostrich 65: 191–203.

The expansion of the range of the Cattle Egret Bulbulcus ibis from its origins in tropical Africa and Asia to Europe, the Americas and Australasia are summarised, and implications of research in Australasia based on birds marked with patagial tags on the spread of the species discussed.     

PRESIDENTIAL ADDRESS, 1955

Tomlinson, D. N. S. 1974. Studies of the Purple Heron, Part 1: Heronry structure, nesting habits and reproductive success. Ostrich 45: 175–181.

At Lake McIlwaine, Rhodesia, Ardea purpurea nests in bulrush Typha latifolia stands or on island termite mounds covered with reeds Phragmites mauritianus, which are connected to the mainland by Polygonum senegalense weed. Nest construction was different in thickness, diameter, height and materials used between the two types of nesting habitat. Clumping of nests in pairs and trios was apparent andMayhave some social significance. The Marsh Harrier Circus ranivorus preyed on the eggs and small chicks of the heron, whilst the Clawless Otter Aonyx capensis probably preyed on large chicks destroying the nest completely in the process. Low lake levels appear to be a major limiting factor to nesting success.     

Patterns of resource partitioning by nesting herons and ibis: How are odonata exploited?

Herons and ibis are colonially nesting waders which, owing to their number, mobility and trophic role as top predators, play a key role in aquatic ecosystems. They are also good biological models to investigate interspecific competition between sympatric species and predation; two processes which structure ecological communities. Odonata are also numerous, diverse, mobile and can play an important role in aquatic ecosystems by serving as prey for herons and ibis. A relationship between prey size and bird predator has been observed in Numidia wetlands (NE Algeria) after analyzing food boluses regurgitated by six species of birds (Purple Heron, Black-crowned Night Heron, Glossy Ibis, Little Egret, Squacco Heron and Cattle Egret) during the breeding period, which also shows a temporal gradient for the six species. Both the Levins index and preliminary multivariate analysis of the Odonata as prey fed to nestling herons and ibis, indicated a high degree of resource overlap. However, a distinction of prey based on taxonomy (suborder and family) and developmental stage (larvae or adults) reveals a clear size dichotomy with large-sized predators (Purple Heron, Black-crowned Night Heron and Glossy Ibis) preying on large preys like Aeshnids and Libellulids and small-sized predators feeding mainly on small prey like Zygoptera. Overall, the resource utilization suggests a pattern of resource segregation by coexisting nesting herons and ibis based on the timing of reproduction, prey types, prey size and foraging microhabitats.     

PREY OF GIANT EAGLE OWLS IN THE DE HOOP NATURE RESERVE,CAPE PROVINCE,AND SOME OBSERVATIONS ON HUNTING STRATEGY

Avery, G., Robertson, A. S., Palmer, N.G. & Prins, A. J. 1985. Prey of Giant Eagle Owls in the De Hoop Nature Reserve, Cape Province, and some observations on hunting strategy. Ostrich 56: 117–122.

Prey remains of Giant Eagle Owls Bubo lacteus in the De Hoop Nature Reserve were analysed in terms of numerical composition and mass. Thirteen species of bird contributed 57,8 % of the mass, six species of mammal 41,4 %, four species of invertebrate less than 0,4 % and one species of amphibian 0;4% Black-headed Heron Ardea melanocephala was the most common bird representing 14,8 % of the mass. Accipitridae (buzzards and harriers) and Tytonidae (owls represented 10,1 % of the mass. Leporidae (hares) were the most common mammals represented 10,7% of the mass. A single bone of an adult Grysbok Raphicerus melanoris represented 20,1% of the mass and was almost certanly taken as carrion. Similarities with diet data from other areas are apparent. The Giant Eagle Owl is omnivorous, its diet being determined bayrhabitat and local abundance. Comparison with the diet of Cape Eagle Owl Bubo capensis confirms that separation of habitats, with associated differences in the accessibility and availability of prey, explains the differences in prey taken by these species.     

Sea and colonial-nesting birds of islands in the southern part of Amurskii Liman

The quantity of the nesting couples of sea birds on the islands of the southern part of Amurskii Liman was determined: common heron Ardea cinerea, slaty-backed gull Larus schistisagus, black-tailed gull L. crassirostris, and sooty guillemot Cepphus carbo.     

Changes in habitat suitability influence non‐breeding distribution of waterbirds in central Europe

Waterbird species have different requirements with respect to their non‐breeding areas, aiming to survive and gain condition during the non‐breeding period. Selection of non‐breeding areas could change over time and space driven by climate change and species habitat requirements. To help explain the mechanism shaping non‐breeding area selection, we provide site‐specific analyses of distributional changes in wintering waterbirds in central Europe, located at the centre of their flyways. We use wintering waterbirds as a highly dynamic model group monitored over a long‐time scale of 50 years (1966–2015). We identified species habitat requirements and changes in habitat use at the level of 733 individual non‐breeding (specifically wintering) sites for 12 waterbird species using citizen‐science monitoring data. We calculated site‐specific mean numbers and estimated site‐specific trends in numbers. The site‐specific approach revealed a general effect of mean winter temperature of site (seven of 12 species), wetland type (all species) and land cover (all species) on site‐specific numbers. We found increasing site‐specific trends in numbers in the northern and/or eastern part of the study area (Mute Swan Cygnus olor, Eurasian Teal Anas crecca, Common Pochard Aythya ferina, Great Cormorant Phalacrocorax carbo and Eurasian Coot Fulica atra). Common Merganser Mergus merganser, Great Cormorant, Grey Heron Ardea cinerea, Common Pochard, Eurasian Coot and Common Moorhen Galinulla chloropus increased their site‐specific numbers on standing industrial waters with traditionally low fish stock. The site‐specific dynamics of bird numbers helped us to identify general preference for sites reducing winter harshness (warmer areas, running waters and more wetlands in the site vicinity), as well as indicating climate‐driven changes in spatial use of wintering sites (northern/north‐eastern range changes and changes in preference for industrial waters). This fine‐scale (site‐specific) approach can reveal large‐scale range and distribution shifts driven by climate and environmental changes regardless of the availability of large‐scale datasets.     

Long-term trends of heron and egret populations in Italy, and the effects of climate, human-induced mortality, and habitat on population dynamics

Factors affecting bird population dynamics include climate, harvesting by humans, and habitat changes. Here, we describe the long-term (1972–2006) population trends of seven heron species in NW Italy, an area holding important European breeding populations of these species. Grey (Ardea cinerea), purple (Ardea purpurea), and squacco (Ardeola ralloides) herons, and little egrets (Egretta garzetta) exhibited a strong logistic increase, leveling off around year 2000 at 3–23 times their initial level. Black-crowned night herons (Nycticorax nycticorax) began by increasing like the former species but then dropped to initial levels. Such trends were found to be influenced by several candidate ecological factors, as assessed by ARIMA models. Specifically, grey herons increased following a decrease in human-induced mortality, as quantified by an index of hunting pressure, and an increase in winter temperatures. Little egrets increased mainly with the increase of the extent of ricefields, whereas squacco herons increased with increasing rainfall in the African wintering range. Black-crowned night herons were also positively affected by increasing African rainfall, but only during 1972–1988, whereas in later years competition with other herons could have affected the species’ decline. The improved protection of colony sites by special reserves was unlikely to be the primary trigger of the observed increase, although obviously important for the long-term population persistence. In conclusion, our study shows that heron populations of southern Europe are sensitive to environmental and climatic changes, as well as to temporal variation in human disturbance and changes in foraging habitats, though the importance of the different factors differs among species.     

Can redistribution of breeding colonies on a landscape mitigate changing predation danger?

The reproductive success of colonially breeding species depends in part upon a trade‐off between the benefit of a dilution effect against nestling predation within larger colonies and colony conspicuousness. However, there may be no net survivorship benefit of dilution if smaller colonies are sufficiently inconspicuous. This raises the question about how the size distribution of breeding colonies on a landscape might change as the predation danger for nestlings changes. In southwest British Columbia, Canada, bald eagle Haliaeetus leucocephalus populations have increased exponentially at ～5% per year in recent decades and prey upon nestlings of colonial breeding great blue herons Ardea herodias faninni. Motivated by field data on reproductive success in relation to colony size, modeling is used to ask under which circumstances trading off a dilution benefit against colony conspicuousness can improve population reproductive success. That is, which colonial nesting distribution, dispersed and cryptic versus clumped and conspicuous, best mitigates predation danger on nestlings? When predators are territorial, the modeling predicts a dispersed nesting strategy as attack rate increases, but not as predator numbers increase. When predators are non‐territorial, the modeling predicts a dispersed nesting strategy as predator numbers and/or attack rates increase. When predators are both territorial and non‐territorial, colonial nesting within a predator's territory improves reproductive success when attack rates are low. This suggests nesting in association with territorial predators may offer decreased levels of predation when compared with nesting amongst non‐territorial predators. Thus a change in the colony size distribution of colonially breeding species might be anticipated on a landscape experiencing a change in predation danger.     

NOTES ON THE CAPRIMULGIDAE OF THE KAFUE BASIN

During 2002–2007, we assessed the status of the Purple Heron Ardea purpurea in Numidia, Algeria by surveying all the major wetlands in the region. We located six distinct breeding sites; four of these were not previously known. We also investigated nest site selection and determined the species’ reproductive success at Dakhla, a dunary pond during two successive years (2006 and 2007). The egg laying period was comparable to that reported for southern Europe (March-May) and a seasonal change of breeding success was recorded. A growth curve was derived for developing nestlings and the impact of an ectoparasite (mite) infestation upon nestling's growth was considered. We also examined 73 food boluses regurgitated by nestlings and identified 329 prey items. Fish, mainly Gambusia holbrookii and Cyprinus carpio, dominated by mass, whereas insects, mainly aquatic Coleopteran larvae and aeshnids (Odonata), were the most frequent prey (67.1%). Loss of habitat is identified as a major threat to the future of colonial herons in Algeria.     

Nest survival is influenced by parental behaviour and heterospecifics in a mixed‐species colony

Studies of avian nest success often focus on examining influences of variation in environmental and seasonal factors. However, in‐depth evaluations can also incorporate variation in individual incubation behaviour to further advance our understanding of avian reproductive ecology. We examined these relationships in colonially nesting Black‐crowned Night‐Herons Nycticorax nycticorax using intensive video‐monitoring methods to quantify incubation behaviours. We modelled nest survival as a function of both extrinsic factors and incubation behaviours over a 3‐year period (2010–12) on Alcatraz Island, USA. Model‐averaged parameter estimates indicated that nest survival increased as a function of greater incubation constancy (% of time spent incubating eggs within a 24‐h period), and average daily precipitation throughout the nesting stage. Common Ravens Corvus corax are the only known nest predator of Night‐Herons on Alcatraz Island, as on many other coastal Pacific islands. We also investigated the effects of heterospecific nesting of California Gulls Larus californicus and Western Gulls Larus occidentalis in a mixed‐species colony with Night‐Herons, based on nesting proximity data collected over a 2‐year period (2011–12). This second analysis indicated that, in addition to incubation behaviours, nesting heterospecifics are an important factor for explaining variation in Night‐Heron nest survival. However, contrary to our original expectation, we found that Night‐Herons experienced increased nest survival with increasing distance from gull colony boundaries. These results may apply to other areas with multiple colonial nesting species and similar predator communities and climatic patterns.     

Reedbed selection and colony size of breeding Purple Herons Ardea purpurea in southern France

Reedbeds of Phragmites australis have declined in Europe in recent decades. Moreover, in some European countries the remaining reedbeds are intensively managed for industrial reed cutting, hunting or grazing. Several species of conservation concern, such as herons and pelicans, use reedbeds as their principal breeding habitat. At the same time, data on habitat use and colony size of these species in relation to reedbed management practices are scarce. We investigated habitat characteristics of 71 reedbeds occupied or unoccupied by breeding Purple Herons Ardea purpurea in the Rhône delta (Camargue) and in other Mediterranean coastal marshes in southern France. In addition, data on colony size in occupied reedbeds were collected from aerial surveys. Reedbeds occupied by breeding Purple Herons were unharvested, or only partially harvested, in winter and had higher water levels in spring compared with unoccupied reedbeds. A logistic regression model with reed harvesting intensity and water levels in mid‐April as independent variables correctly classified reedbed use for 94.7% of the reedbeds in the study. A model with water levels in mid‐April alone was only 90.9% accurate, suggesting that low water level in spring is the most important factor limiting reedbed occupation by breeding Purple Herons. A general linear model indicated significant effects of harvesting intensity and reedbed surface area on colony size. Within occupied reedbeds there was a strong tendency for colony size to increase with increasing reedbed surface area. Given the recent developments in reed harvesting and wetland management in southern France and elsewhere in Europe, these results provide the first information on potential effects of these practices on reed nesting herons, and suggest that Purple Heron conservation is likely to be favoured by maintaining large uncut reedbeds with relatively high water levels in spring. The possible effect of changes in habitat on the Purple Heron population in southern France is discussed.     

STUDIES OF THE PURPLE HERON,PART 2: BEHAVIOUR PATTERNS

Tomlinson, D. N. S. 1974. Studies of the Purple Heron, Part 2: Behaviour patterns. Ostrich 45: 209–223.

Some aspects of Purple Heron Ardea purpurea behaviour have been covered although the study is not complete. Further observations are needed, especially on pair formation, nest building and copulation. Many of the displays described for the Ardeidae are clearly homologous and only slight differences exist. The throat puffing component in the Aggressive Upright Display appears unique to A. purpurea as does the clappering and sudden retraction of the neck in the Stretch Display. Birds raised in captivity provided valuable information on agonistic behaviour patterns and the behaviour of young.