Rates of single-copy DNA evolution in herons

DNA-DNA hybridization was used to discover the extent of single-copy DNAsimilarity among 13 species of herons and one ibis. Genetic distances amongtaxa were summarized as Tm values in a folded matrix. From this matrix,trees with the same branching pattern were constructed by least squaresunder one of two assumptions: (1) that sister branches are equal in lengthand (2) that sister branches are not necessarily equal in length. Theresidual sums of squares of these trees were compared by F-test to seewhether the branches of the tree built under assumption (2) fit the matrixdata significantly better than those of the tree built under assumption(1). By this method the existence of different rates of DNA evolution indifferent heron lineages was established. Bittern single-copy DNA hasevolved at a rate approximately 25% faster, and boat-billed heron(Cochearius) and rufescent tiger heron (Tigrisoma lineatum) DNA has evolvedapproximately 19% slower, than that of day and night herons. It appearsthat the differences in rates of DNA evolution may increase proportionallywith genealogical distance.     

Steatitis in egrets and herons from Japan

More than 70 egrets and herons were found sick or dead at an agricultural water reservoir in Kanagawa Prefecture, Japan between September and October 2008. The birds showed weakness, lethargy, and inability to fly before death. Postmortem findings included large amounts of firm subcutaneous and cavitary fat comprised of necrotic adipose tissues with infiltrates of heterophils and macrophages. The birds were diagnosed with steatitis on the basis of the gross lesions and histopathology. Egrets with steatitis had low blood levels of vitamin E. High counts of cyanobacteria (Microcystis aeruginosa) were found in the reservoir concurrent with the outbreak of steatitis. No microcystin was detected in the reservoir water or the livers from the egrets. This is the first report of steatitis in wild birds in Japan.     

Isolation and characterization of a hepatitis B virus endemic in herons.

A new hepadnavirus (designated heron hepatitis B virus [HHBV]) has been isolated; this virus is endemic in grey herons (Ardea cinerea) in Germany and closely related to duck hepatitis B virus (DHBV) by morphology of viral particles and size of the genome and of the major viral envelope and core proteins. Despite its striking similarities to DHBV, HHBV cannot be transmitted to ducks by infection or by transfection with cloned viral DNA. After the viral genome was cloned and sequenced, a comparative sequence analysis revealed an identical genome organization of HHBV and DHBV (pre-C/C-, pre-S/S-, and pol-ORFs). An open reading frame, designated X in mammalian hepadnaviruses, is not present in DHBV. DHBV and HHBV differ by 21.6% base exchanges, and thus they are less closely related than the two known rodent hepatitis B viruses (16.4%). The nucleocapsid protein and the 17-kilodalton envelope protein sequences of DHBV and HHBV are well conserved. In contrast, the pre-S part of the 34-kilodalton envelope protein which is believed to mediate virus attachment to the cell is highly divergent (less than 50% homology). The availability of two closely related avian hepadnaviruses will now allow us to test recombinant viruses in vivo and in vitro for host specificity-determining sequences.     

A novel primary bile acid in the Shoebill stork and herons and its phylogenetic significance

The Shoebill stork, an enigma phylogenetically, was found to contain as its dominant biliary bile acid 16alpha-hydroxychenodeoxycholic acid, a heretofore undescribed bile acid. The bile acid occurred as its taurine N-acyl amidate; structure was established by nuclear magnetic resonance (NMR) and mass spectrometry (MS). A search for this novel bile acid in other Ciconiiformes showed that it constituted >92% of biliary bile acids in five of nine herons in the Ardidae, but was absent in all other families (Ciconiidae, Threskiornithidae, Scopidae, Phoenicopteridae). The presence of this biochemical trait in the Shoebill stork and certain herons suggests that these birds are closely related.     

Postnatal growth patterns in eight species of herons and egrets (Ciconiiformes: Ardeidae)

Avian postnatal growth has received considerable attention and its ecological implications have been deeply analyzed. In this current paper, I describe the patterns of culmen and tarsus growth, as well as of weight gain patterns in eight species of herons and egrets (Aves: Ardeidae) found in the Birama Swamp in Eastern Cuba. Between 1998 and 2006,714 nestlings of the following species were measured every two days: Butorides virescens, Bubulcus ibis, Egretta thula, E. tricolor, E. caerulea, E. rufescens, Ardea alba and Nycticorax nycticorax. Logistic and Gompertz equations were adjusted to data using non-lineal regression models with adult values as the asymptote. For each species, the following were determined and recorded: growth rate, age at inflexion, instantaneous growth rates at each age interval, and time taken to reach 90% of adult size. Reported hatchling sizes were similar in other localities, with a variation coefficient ranging between 10-19%. At hatch, each species exhibited differing sizes relative to adult values. In all cases, Gompertz equations were best fitted to explain more variance and lesser residuals. Rates of weight change and tarsus growth were alometrically related to the log of adult weight. Two main growth processes were identified: a physical extension in dimensions of each measurement reflecting inter-specific morphometric differences, and a lineal increase of the growth period from Green Heron to Great Egret. The Black-crowned Night Heron, Cattle Egret and Reddish Egret exhibited some unique measurement characteristics in comparison to the remaining members of the family. All results support the hypothesis that hypermorphosis, as the main evolutionary process in the microevolution of Ardeidae, is caused by a delayed final moment of growth.     

Kinematic parameters of the walking of herons, ground-feeders, and waterfowl

The kinematic gait characteristics of six species of birds in three groups were compared. The groups studied were herons (Gray Herons and Little Egrets), ground-feeders (Domestic Pigeons and Gray Starlings), and waterfowl (Pintails and Black-headed Gulls). The results showed that the relative stride frequency was greater in the waterfowl than in the other species. Complementary to this, the amplitude of the movements was smaller in the waterfowl than in the others. These differences between the waterfowl and the other species might be caused by their morphological and/or physiological adaptation to swimming. Another possible cause for these differences was the magnitude of head bobbing, as the ground-feeders and herons, which walk with head bobbing, showed a large relative stride length and excursion angle, while the waterfowl, which do not head-bob, walk with a relatively short stride length and small excursion angle. Moreover, the relative magnitude of head movement during walking was especially large in Little Egrets, which showed an especially large relative stride length and excursion angle. These parameters may have some mechanical relationships with each other.     

Cattle egrets are less able to cope with light refraction than are other herons

The majority of heron species (Aves, Ardeidae) forage on aquatic prey in shallow water. Prey detection, aiming and the beginning of the capture strikes are performed while the heron's eyes are above water. For most angles, as a result of air/water light refraction, the apparent image available to a heron is vertically displaced from the prey's real position. Herons must therefore correct for refraction. We tested the hypothesis that species that forage in aquatic habitats should be more able to correct for image disparity than those of terrestrial habitats. The ability of hand-reared herons of four species to capture stationary prey (fish) underwater (submerged) or in air (aerial) was tested. Three species (little egret Egretta garzetta, squacco heron Ardeola ralloides, and night heron Nycticorax nycticorax) normally forage in aquatic habitats while the fourth (cattle egret Bubulcus ibis) forages in terrestrial habitats. No individuals missed aerial prey. Success rates of little egrets and of squacco herons with submerged prey were high, while night herons became less successful with increased prey depth and/or distance. In cattle egrets, success rate was low and negatively correlated with prey depth. The observed interspecific differences may thus be related to (1) differential ability to correct for air/water light refraction and (2) the species' foraging behaviour. We suggest that cattle egrets are in the process of losing their ability to cope with submerged prey. Copyright 1999 The Association for the Study of Animal Behaviour.     

Application of random forest algorithm for studying habitat selection of colonial herons and egrets in human-influenced landscapes

Understanding the mechanisms of habitat selection is fundamental to the construction of proper conservation and management plans for many avian species. Habitat changes caused by human beings increase the landscape complexity and thus the complexity of data available for explaining species distribution. New techniques that assume no linearity and capable to extrapolate the response variables across landscapes are needed for dealing with difficult relationships between habitat variables and distribution data. We used a random forest algorithm to study breeding-site selection of herons and egrets in a human-influenced landscape by analyzing land use around their colonies. We analyzed the importance of each land-use variable for different scales and its relationship to the probability of colony presence. We found that there exist two main spatial scales on which herons and egrets select their colony sites: medium scale (4 km) and large scale (10–15 km). Colonies were attracted to areas with large amounts of evergreen forests at the medium scale, whereas avoidance of high-density urban areas was important at the large scale. Previous studies used attractive factors, mainly foraging areas, to explain bird-colony distributions, but our study is the first to show the major importance of repellent factors at large scales. We believe that the newest non-linear methods, such as random forests, are needed when modelling complex variable interactions when organisms are distributed in complex landscapes. These methods could help to improve the conservation plans of those species threatened by the advance of highly human-influenced landscapes.     

Seasonal trend in movement directions at dawn and dusk: a study on crow and white herons

Crows (Corvus splendens) and white herons (Ardea alba) inhabit the agricultural landscapes nearby human habitats which represent dynamic ecosystem and show seasonal crop patterns. We studied the movement pattern in these birds at dawn and dusk, during solstices (December and June) and equinoxes (March and September). The movement directions were changed from uniform at dawn to a concentrated distribution at dusk all along the season suggesting that morning movements are more exploratory than evening with seasonal differences. Differential use of directions in December than June could be the effect of temperature, food availability or wind direction and speed. During breeding, less number of directions used suggests that birds might be moving towards the directions having high probability of food availability. It is likely that avian dispersal in space and time is dependent on the food availability however, further studies are required to be carried out.     

Head Injuries in Children

Two-hundred children with head injury admitted consecutively to paediatric wards in the two main hospitals in Newcastle upon Tyne have been studied. Eight children required neurosurgical operation. There were two deaths. Details of the cause and consequences of the accidents have been analysed and an attempt has been made to identify psychological or physical factors that may predispose to injury. There was a slightly higher proportion of children with what are regarded as adverse personality factors among the head injuries than in a control group and there were more left-handed children than would be expected in the general population. The results suggest that the modern “high-rise” bicycle may carry a special risk of head injury.