Some observations on egg production and autoreinfection of Reighardia sternae (Diesing, 1864), a pentastomid parasite of the herring gull.

Egg production by Reighardia sternae, implanted at various stages of maturity into the interclavicular air sacs of captive gulls, is described. Females produce only 2900 eggs per lifetime over a short patent period of 1-3 days. The problem of a direct life-cycle in relation to this unusually low fecundity is discussed, and speculation is advanced concerning a possible parasitic behavioural trait which could facilitate direct transmission. The hazards of the latter are also offset by auto-reinfection.     

Breeding adaptations of Franklin's gull (larus pipixcan) to a marsh habitat

The behaviour and ecology of Franklin's gull were studied at Agassiz National Wildlife Refuge in northwestern Minnesota to determine the adaptations of the species for nesting in marshes. Two factors seemed to be important in colony site selection: cattail dispersion pattern and cattail density. Franklin's gulls prefer to nest in cattail areas closest to open water. The number of nests per unit area decreased as cattail density increased. Nest site selection is dependent on aggression and visibility. Visibility from nest level is the result of cattail placement and height. The distance between nests was directly correlated with visibility. Aggression by gulls on nests was lowered experimentally by decreasing visibility and raised by increasing visibility. Nest platforms were constructed of cattail material, and were attached to cattail stems. Nest material was added to the nests throughout the incubation and brooding period. Material was usually added following nest relief. The egg laying period was from 6 to 28 May. There was more synchrony of egg laying in sub-areas of the colony than in the colony as a whole. Successive eggs in clutches were laid at 24- to 48-hr intervals. The distance between nests decreased during the season as pairs filled in areas that were not defended. Territorial pairs defended an area up to 10 m from their stations prior to egg laying, but defended only the area within 3 m of their nests during incubation. Both members of pairs incubated the eggs and cared for the young. The incubation period was 24 days. The primary predators on adults and young were marsh hawk, great horned owl and mink. Franklin's gulls do not eat eggs or young of gulls. Adults fed on earthworms, insects and grain. Most marked adults fed within 16 km of the colony. Chicks were fed primarily on earthworms. The hatching period was from 30 May to 21 June. Chicks of all ages tested on a visual cliff apparatus were able to perceive the drop. Chicks tested on a 30-degree incline apparatus walked up it when 6 days old and younger, and walked down at 12 days of age and older. Brood mobility was less than in ground nesting species of gulls. In an undisturbed colony the chicks remained on the nest platforms until they were 25 to 30 days old although they were capable of swimming shortly after hatching. Individual recognition between parents and chicks appeared later in this species than in ground-nesting gulls. Adults accepted alien chicks (experimentally exchanged) that were younger than about 14 days old until their own chicks were over that age. Adults accepted larger and older broods than their own, as well as broods of mixed ages. Chicks began to react differently to strange adults at about 16 days of age. The breeding chronology of Franklin's gull is compressed when compared to that of other gulls. Possible selection pressures affecting this synchrony are discussed. The behaviour of the marsh-nesting Franklin's gull is compared with that of typical ground-and cliffnesting gulls; the possibility that the ancestral gull may have been a marsh nester is discussed.     

Spatial contraction in a large gull colony in relation to the position of arctic fox dens

Many species of colonial ground-nesting birds are known to be sensitive to predation by terrestrial predators. The response of prey under the pressure of predation can either be direct (depletion of prey) or indirect due to prey avoiding the predator. We studied the recolonization of arctic foxes into a large and growing breeding colony of lesser black-backed gulls. The gull colony reached the size of 20,000 pairs during the period of no foxes. The number of breeding gulls continued to increase after the colonization of foxes and reached a maximum of 40,000 pairs about 15 years later. During the same time period, the spatial coverage of the gull colony shrunk from 31.4 down to 18.6 km², and the change in distribution was closely linked with position of fox dens, which ranged in number from one to three annually. In 2005, the number of breeding gulls decreased slightly with an ongoing shrinkage in spatial coverage. Food analyses from fox scats and stomachs showed that birds of the order Charadriiformes, particularly gulls, were the key prey item. Survival rates of gull nests were higher in the middle of the colony than at the colony edge close to a fox den. The colony area lost could be explained solely by the number of eggs removed by foxes but is unlikely, e.g., due to reclutching. We suggest that intraspecific predation contributes additionally to the effects of direct fox predation although to an unknown degree.     

Can rats prey on gull eggs? An experimental approach

Black rat Rattus rattus populations can reach high densities on the Mediterranean islands, as has been the case on the Chafarinas Islands (Western Mediterranean coast) in the last decade. This archipelago holds the second largest breeding population of Audouin's gull Larus audouinii and an important population of yellow-legged gull Larus cachinnans. Circumstantial evidences of rat predation upon Audouin's gull eggs led to conservation concerns about the impact of rat predation on gull productivity. We studied the impact of rats on gull nests experimentally by building artificial nests into the breeding area of yellow-legged gulls. Two kinds of eggs were placed in the artificial nests: manipulated eggs, in which the shell had been previously opened, and intact (unmanipulated) eggs. Rats preyed extensively on opened eggs but only once on intact eggs, apparently due to lack of skills to prey on intact eggs, suggesting that rats do not normally have access to fresh gull eggs. Rats inhabiting breeding areas of gulls can scavenge on broken eggs rolled out of the nest or on eggs with softened shells after nest desertion, but it is unlikely that they prey on natural gull nests guarded by parents. We suggest that introduced black rats on Mediterranean islands can only marginally affect the productivity of gulls owing to egg predation.     

Elimination of some enteroviruses in the excrements of experimentally infected rats (Rattus norvegicus) and gulls (Larus ridibundus)

Young rats of both sexes, weight 150-170 g, the first laboratory progeny of captured wild parent pairs, were used throughout this experiment. Rats in two experimental groups comprising a total of 34 animals were infected orally with type 2 poliovirus vaccine strain given in each group at doses of 500, 5000 or 50,000 TCD50. In the first experiment, the presence of poliovirus in rat excrements was detectable irregularly till day 13, in the second experiment till day 2 after infection. Small quantities of virus were also detectable from the colon and cecum wall, exceptionally from the mesenteric lymph node. The third experiment included 8 rats orally infected with 5,000 TCD50 of echovirus 30; at the lower dose of virus all excrement samples were culture-negative, at the higher dose the positive virus recovery was recorded in 3 animals one day after infection. Analogous experiments in the fifth group of rats orally infected with 5,000 TCD50 or 50,000 TCD50 of enterovirus 71 yielded much the same results; organs of further 6 animals infected intranasally with 5,000 TCD50 of this virus were culture-negative and no virus-related changes could be histologically demonstrated in these animals. The second part of this study included the experiments conducted on 17 young Larus gulls bred in the laboratory from eggs collected in a colony of free living birds. Groups of these gulls were orally infected with 500 or 5,000 TCD50 of one of the following viruses: type 1 poliovirus vaccine strain, type 3 poliovirus vaccine strain, echovirus 30, enterovirus 71 and coxsackievirus B4. All samples of gull excrements collected till day 7 or 20 postinfection were culture-negative. These results suggest that wild rats may play some role in the spread of human enteroviruses in the environment, but no such role could be demonstrated in the Larus gull.     

Colonial breeding reduces nest predation in the common gull (Larus canus)

It is often suggested that colonial breeding reduces nest predation for birds with a high defence capacity, but experimental comparison of predation at solitary and colonial nests is seldom feasible within a single species. We here report on such a test in the common gull (Larus canus). The rate of predation on experimental eggs was significantly lower near colonies than near solitary gull nests, and the eggs survived longer at the edge of a colony than farther away. Communal mobbing of nest predators is the likely reason. In both of two years, almost all nests of solitary gulls were destroyed by predators, while most clutches survived in colonies. Nest predation hence selects strongly for colonial breeding in the present population of common gulls.     

Egg oiling to reduce hatch-year ring-billed gull numbers on Chicago's beaches during swim season and water quality test results

A burgeoning ring-billed gull population along Chicago's Lake Michigan beaches contributes to degraded water quality through fecal contamination. Egg oiling was conducted at Chicago's gull colonies to reduce production and the influx of hatch-year (HY) gulls using Chicago's beaches, with a second, long-term objective of eventually reducing adult gull numbers through attrition. We also investigated swim season water quality trends through the course of this work. From 2007 to 2009, 52, 80, and 81%, of nests at the two primary nest colonies had their eggs rendered inviable by corn oil application. Counts of HY and after hatch-year (AHY) gulls were analyzed during treatment years for 10 beaches. Water quality data were available from the Chicago Park District during our three treatment years and the prior year (baseline) for 19 beaches. HY counts declined at all 10 surveyed beaches from the initial year (52% nests with oiled eggs) to subsequent years with ~80% of nests oiled. Overall, HY gulls numbers on beaches decreased 86% from 2007 to 2009. Decreases in beach usage by AHY gulls were not detected. Compared to pretreatment, the number of beaches with improved water quality test rates increased each year through the course of the study. The frequency of water quality tests showing bacterial exceedances compared to 2006 declined at 18 of 19 beaches by 2009. Egg oiling resulted in fewer HY gulls using Chicago's beaches and was likely a beneficial factor for reduced frequencies of swim advisories and swim bans.     

Experimental life cycle of Lagochilascaris major leiper, 1910 (Nematoda: Ascarididae) in cats (Felis domesticus)

The life cycle of Lagochilascaris major was studied using eggs collected from a natural clinical case in a domestic cat. Twenty-seven white mice (Mus musculaus), 5 hamsters (Mesocricetus auratus), and 1 vesper mouse (Calomys callosus) were orally inoculated with 800-1,300 embryonated eggs. When examined from 73 to 246 days postinoculation (PI), encysted third-stage larvae were seen in skeletal muscles and less frequently in connective tissue, liver, and lungs. Twenty-two of the 23 cats orally inoculated with 40-430 encysted larvae from these rodents, and necropsied from 1 hr to 185 days PI, became infected. Third-stage larvae were located in the stomach, esophagus, and oropharynx from 1 to 24 hr PI. At 48 hr, larvae, from mainly the fourth stage, were only found, unilaterally or bilaterally, inside a "sac" in the region of the semilunar fold of the palatine tonsil at the base of the tongue. Adult worms were found in this location from 10 to 175 days PI. No fistulated abscess to the outside medium was found. Adult worms were also found in the middle ears of 2 cats showing purulent otitis. Eggs in the ear secretion were under different stages of development. Eggs in feces were first observed on days 14 and 15 PI, and 1 cat shed them until 178 days PI. Six infected cats were treated with fenbendazole at 50 mg/kg of body weight for 3 consecutive days, eliminating all the parasites present in the tonsils. The drug was not effective against the parasites present in the middle ear. No stage of the parasite was found in the tissues of 5 cats given 4,000-5,200 eggs orally and examined after 19 and 50 days PI. This indicates that the life cycle of L. major requires an obligate paratenic host and is characterized by heteroxenic cycle.     

The role of wild birds in the spread of influenza viruses

Eggs deposited by different migrating wild bird species in pond farm areas in Hungary were examined for yolk antibodies to different variants of human A/H3N2 influenza virus. Antibodies to Victoria/75 and Texas/77 occurred in 17.9 and 32.0% of gull eggs, and 5.6 and 16.4% of common tern eggs, respectively, while antibodies to A/H1N1/77 occurred in roughly similar proportions (10.2 and 13.4%) in the eggs of both species. Infection of the gull and tern populations of given areas by human and avian influenza A viruses differed greatly in two consecutive hatching periods. While in 1978 7.6 and 1.1% of the gull and tern eggs, respectively, contained antibodies to the avian subtype Havl, no such antibodies were found in 1977. Subtype A/H3N2/Texas/77 virus was isolated from adult gulls and 1-3 weeks old gull chicks, and subtype H1N1 virus from mallard ducks. Three months before the onset of the Texas/77 epidemic, 95% of SPF chickens, and 71-81% of chickens hatched 3 months after termination of the A/H1N1/77 epidemic, had had HI, VN and SRH antibodies to the Texas/77 strain and A/H1N1/77 strains, respectively.     

Raillietiella trachea n. sp., a pentastomid from the trachea of an oriental white-backed vulture Gyps bengalensis taken in Pakistan,with speculation about its life-cycle

A cephalobaenid pentastomid, Raillietiella trachea n. sp., from the trachea of a fledgling oriental white-backed vulture Gyps bengalensis taken in Punjab Province, Pakistan, is described. This is the first record of a pentastomid from a fully terrestrial bird. Overall, gross morphology was typical of Raillietiella Sambon, 1910 in most respects. However, the hooks of R. trachea were of equal size, whereas in other members of the genus anterior hooks are smaller than the posterior hooks. The diagnosis of R. trachea was made on the basis of four near-patent females, all of which contained relatively few eggs (c.570), all at the same stage of maturity. Comparison with the only other genus known to infect birds (two species of Reighardia Ward, 1899 from the air-sacs of marine birds) revealed striking parallels in this aspect of the functional anatomy of the female reproductive tract. As far as we know, this mode of egg-production is not found in other raillietiellids. Extrapolating primarily from the experimental life-cycle studies of Reighardia sternae (Diesing, 1864) Ward, 1899, we surmise that the life-cycle of R. trachea has to be direct and that parasite behaviour is an integral part of parasite transmission. The evidence suggests that transmission is from vulture-to-vulture, per os.     

Impact of a novel species of Nosema on the southwestern corn borer (Lepidoptera: Crambidae)

A study was undertaken to elucidate the impact of an undescribed Nosema sp. on the southwestern corn borer (SWCB; Diatraea grandiosella Dyar). The Nosema sp. (isolate 506) included in the study was isolated from an overwintering SWCB larva in Mississippi. It was highly infectious per os, with a median infective dose of 2.0 x 10(3) spores per larva. Even at the highest dosage tested (10(7) spores per larva), minimal mortality (< or = 3%) was observed in infected larvae, pupae, and adults reared in the laboratory on an artificial diet. However, infected pupae (0- and 7-d-old) were smaller, and the time to adult eclosion from pupation was slightly increased. Furthermore, the number of eggs produced by infected SWCB female moths substantially decreased (32%), and this effect was most pronounced on day 2, when the greatest number of eggs were oviposited by infected and noninfected moths. For eggs produced by infected females mated with infected males, hatch was slightly decreased by 16 and 15% for eggs laid on days 2 and 3, respectively. In addition, egg hatch was reduced in eggs oviposited by noninfected females mated with infected males on day 3. A low prevalence of infection (< 6%) was observed in the F1 generation originating from infected females mating with noninfected males, from noninfected females mating with infected males, and from infected females mating with infected males. Nosema 506 spores were observed in the proximity of reproductive tissues of infected female and male moths. Spores also were detected on the chorion surface and within eggs laid by infected females. Furthermore, 1-11% of larvae hatching from surface-sterilized eggs were infected by Nosema 506 indicating a transovarial mechanism of transmission.     

Egg production in a coastal seabird, the glaucous-winged gull (Larus glaucescens), declines during the last century

Seabirds integrate information about oceanic ecosystems across time and space, and are considered sensitive indicators of marine conditions. To assess whether hypothesized long-term foodweb changes such as forage fish declines may be reflected in a consumer's life history traits over time, I used meta-regression to evaluate multi-decadal changes in aspects of egg production in the glaucous-winged gull (Larus glaucescens), a common coastal bird. Study data were derived from literature searches of published papers and unpublished historical accounts, museum egg collections, and modern field studies, with inclusion criteria based on data quality and geographic area of the original study. Combined historical and modern data showed that gull egg size declined at an average of 0.04 cc y(-1) from 1902 (108 y), equivalent to a decline of 5% of mean egg volume, while clutch size decreased over 48 y from a mean of 2.82 eggs per clutch in 1962 to 2.25 in 2009. There was a negative relationship between lay date and mean clutch size in a given year, with smaller clutches occurring in years where egg laying commenced later. Lay date itself advanced over time, with commencement of laying presently (2008-2010) 7 d later than in previous studies (1959-1986). This study demonstrates that glaucous-winged gull investment in egg production has declined significantly over the past ～50-100 y, with such changes potentially contributing to recent population declines. Though gulls are generalist feeders that should readily be able to buffer themselves against food web changes, they are likely nutritionally constrained during the early breeding period, when egg production requirements are ideally met by consumption of high-quality prey such as forage fish. This study's results suggest a possible decline in the availability of such prey, and the incremental long-term impoverishment of a coastal marine ecosystem bordering one of North America's rapidly growing urban areas.     

Slow rate of evolution in the mitochondrial control region of gulls (Aves: Laridae)

We sequenced part of the mitochondrial control region and the cytochrome b gene in 72 specimens from 32 gull species (Laridae, Larini) and 2 outgroup representatives (terns: Laridae, Sternini). Our control region segment spanned the conserved central domain II and the usually hypervariable 3' domain III. Apart from some heteroplasmy at the 3' end of the control region, domain III was not more variable than domain II or the cytochrome b gene. Furthermore, variation in the tempo of evolution of domain III was apparent between phyletic species groups. The lack of variation of the gull control region could not be explained by an increase in the proportion of conserved sequences in these birds, and the gull control region showed an organization similar to those of other avian control regions studied to date. A novel invariant direct repeat was identified in domain II of gulls, and in domain III, two to three inverted, sometimes imperfect, repeats are able to form a significantly stable stem-and-loop structure. These putative secondary structures have not been reported before, and a comparison between species groups showed that they are more stable in the group with the more conserved control region. The unusually slow rate of evolution of control region part III of the gulls could thus be partly explained by the existence of secondary structures in domain III of these species.     

Effects of Bacillus thuringiensis on Adults of Cotesia plutellae (Hymenoptera: Braconidae), a Parasitoid of the Diamondback Moth, Plutella xylostella (Lepidoptera: Plutellidae)

To complement existing information on the mortality of larvae of the wasp Cotesia plutellae attacking moth caterpillars infected with Bacillus thuringiensis (Bt) we tested the direct and indirect effects of the bacterium on adult wasp longevity and oviposition behaviour. In one experiment with female parasitoids, mean longevity (SEM) was not significantly different between females exposed to Bt (1.98 +/- 0.08 days) and those not exposed (2.18 +/- 0.13 days). In a second experiment with both males and females, Bt treatment did not significantly effect either male or female parasitoids exposed to Bt. To observe the possible effects of Bt on oviposition behaviour of C. plutellae each of 10 females were given five larvae that had been treated with Bt and five untreated larvae at the same time. All parasitoids were observed to make oviposition attempts in both untreated and treated larvae. Upon dissection of the host larvae, one or more C. plutellae eggs were found in each of the larvae in which a parasitoid attempted oviposition. There was no effect of Bt treatment on parasitoid oviposition. The mean number of ovipositions in treated larvae (4.3 +/- 0.3) was not significantly different from untreated larvae (4.7 +/- 0.2).     

Ecology of Slaty-Backed Gull (<Emphasis Type="Italic">Larus schistisagus</Emphasis>) Breeding on Kronotskoe Lake,Kamchatka Peninsula

The slaty-backed gull population of Kronotskoe Lake has not been subjected to anthropogenic impact for many decades. The number and distribution of the breeding colonies of the slaty-backed gulls on the islands of this largest freshwater reservoir of the Kamchatka Peninsula are presented. Data on the breeding phenology, the seasonal dynamics of the food composition of breeding gulls, the foraging distance, and breeding success are considered. These data are compared to the results obtained earlier for Kuril’skoe Lake. Both gull populations are unique in that they are the only freshwater colonies within the distribution range of this marine species. The breeding success of the slaty-backed gulls on Kronotskoe Lake suffers from predation, both intra- and interspecific, in the latter case from brown bears and sea eagles. The hatching period and the fledging time of chicks in this population are both shifted to the end of summer, when gulls have the most abundant food available within the lake area, which increases successful survival of the fledglings. Despite considerable differences between the ecosystems of Kronotskoe Lake and Kuril’skoe Lake, there are several common features in the diets of the gull populations living on the lakes: (1) Despite the fact that gulls perform foraging flights to the sea coast, they only take fish and almost never collect marine invertebrates there. (2) Nearly half of all food items are taken within a 40-km distance from the colony. (3) During the growth period of chicks, gulls from both lakes rely on salmonids (anadromous in Kuril’skoe Lake, resident in Kronotskoe Lake) that they hunt in the lakes near their colonies.     

An invasive gull displaces native waterbirds to breeding habitats more exposed to native predators

The effect of invasive opportunistic predators may include population changes in both native prey and native predators as well as alteration of predator–prey interactions. We analyzed the activity of native magpie Pica pica and changes in population, nest sites and nesting success probability of native waterbirds (namely: grebes, ducks, rails and native gulls) in response to the population growth of the invasive Caspian gull Larus cachinnans. The study was carried out at a reservoir in southern Poland and at a similar control reservoir where the Caspian gull was absent. Both the invasive gulls and the native magpie are opportunistic predators of nests of native waterbirds. The population increase of the invasive gull led to a decline in the population of native black-headed gulls Larus ridibundus only. However, the invasive gull displaced all the native species from the breeding islets located in the central part of the reservoir to islets located close to the shoreline. The latter were frequently visited by magpies, which depredated on nests along the shores, leading to an up to threefold decrease in nesting success as compared with nests located in the central area of the invaded reservoir. Predation by Caspian gulls was rarely observed. Thus, the invasion of Caspian gull caused complex direct and indirect effects on the waterbird community that included competition for breeding sites, changes in the spatial distribution of nests and alteration of predation rate by native predators. Moreover, the effects of invasion may not be reflected by changes in population size of native species.     

The possible role of the frontal and sub-parietal gland systems of the pentastomid Reighardia sternae (Diesing, 1864) in the evasion of the host immune response.

The frontal and sub-parietal glands of the pentastomid Reighardia sternae elaborate lamellate secretion which is poured on to the cuticle. The entire surface of the cuticle, including the mouth, hook pits and reproductive apertures, is coated with secretion. Electron microscope studies indicate that the glands are continuously active, which implies a turnover of surface membranes. The postulated function of these membranes is to protect certain vital areas of the host--parasite interface, notably the pores of ion-transporting cells, from the host immune response. The available evidence suggests that pentastomids do evoke a strong immune response but since most are long-lived they must circumvent it. We believe the surface membrane system to be instrumental in this. Studies on another pentastomid, Porocephalus crotali in rats have shown that an immune response stimulated by a primary infection will kill subsequent infections and that the surface membranes are strongly immunogenic. Obvious parallels between this situation and that of schistosome infections in mammals are discussed. An alternative explantation of concomitant immunity is proposed.     

Stealing bivalves from common eiders: kleptoparasitism by glaucous gulls in spring

Here I report on glaucous gulls (Larus hyperboreus), an opportunistic, generalist predator, stealing bivalves from a diving duck, the common eider (Somateria mollissima). The study took place in spring, the pre-breeding period of the common eider, in an Arctic fjord (Adventfjorden) at western Spitsbergen, Svalbard. Eiders were abundant, their presence predictable, and they fed on large prey requiring surface handling—all factors facilitating food theft. Only adult glaucous gulls attended the eider flocks. The glaucous gulls brought stolen prey ashore. Amongst these the bivalve Mya neoovata (Myidae) was common. The probability that an eider flock was attended by glaucous gulls declined as the season progressed and increased with the foraging activity of the eiders. Eider flock size and the degree of aggregation within flocks were poor predictors of gull presence. However, eider flocks attended by a single gull were smaller than flocks attended by more than one gull. Common eiders are capital breeders which build up large energy reserves prior to breeding. Kleptoparasitism, therefore, may have a negative impact on eider energy acquisition in early spring. For the glaucous gull, kleptoparasitism may be important as few other food sources are available this time of the season.     

Foraging distances of a resident yellow-legged gull (Larus michahellis) population in relation to refuse management on a local scale

Seasonal fluctuations in marine prey availability around breeding colonies are one of the major factors affecting resident behaviour in seabirds. This is particularly applicable to large gulls (Larus spp.). The effect of refuse management on large gulls has been studied chiefly in relation to breeding dynamics, but it is less understood with regard to movement patterns. Our aim was to test whether the closure of one large dump and the use of falconry to deter gull access to two others, within the southeastern Bay of Biscay area, affected the foraging distance of local yellow-legged gulls (Larus michahellis). During a period of seven consecutive winters between 2005 and 2011, the proportion of gulls that moved less than 50 km from their natal site was 70 %. However, during the winter of 2010, when they were deterred from accessing refuse tips within the region, gulls were found to travel longer distances. This result was explained neither by a decreasing survey effort near colonies nor by a decrease in apparent availability of marine prey, thus supporting the hypothesis that refuse management within the region influenced the movement patterns of local gulls.