Search

The relationships between feather mites and their avian hosts have great potential as subjects for studies of evolution and ecology. However, we must first achieve a better understanding of the ecological roles of feather mites (mutualistic versus parasitic) as well as their degree of host specificity before we can search for broad generalities at work in bird/feather-mite systems. I investigated host switching and feeding ecology in Zachvatkinia caspica, an analgoid feather mite that lives among the feathers of Caspian Terns (Sterna caspia). My approach involved imping (i.e., transplanting) mite-free feathers from California Gulls (Larus californicus) and Caspian Terns onto mite-infested Caspian Tern wings and quantifying the extent to which mites colonized the newly introduced feathers. This approach allowed me to expose the mites to both host and non-host feathers as well as to the presence or absence of preen oils collected from the two bird species. Mites "incubated" on tern wings showed no obvious avoidance of gull feathers or preen oil. This colonization of gull feathers suggests that some mite species have the potential to occupy a number of host species and that host switching in nature may be limited by infrequent opportunities to colonize nontraditional hosts.

The alternative-prey hypothesis predicts that predation on goose eggs will be most severe the year following a lemming peak. We tested this by investigating how predators of goose eggs responded to lemming abundance on the Kent Peninsula, Nunavut, Canada, where nest success of white-fronted geese (Anser albifrons frontalis) and Canada geese (Branta canadensis hutchinsii) fluctuates widely. The main predators of both goose eggs and lemmings are arctic foxes (Alopex lagopus), glaucous gulls (Larus hyperboreus), and parasitic jaegers (Stercorarius parasiticus). Foxes responded functionally to lemming density: in prime goose-nesting areas they spent less time foraging during the peak lemming year than during the increase, and were seen foraging in prime nesting areas less often during the peak than during the decline. However, numbers of fox sightings in the study area during the nesting period did not differ significantly among years. The total response (functional × numerical) of gulls was lowest at the lemming peak and highest during the increase. The total response of parasitic jaegers did not vary significantly among years. Hence, we predicted that the number of nests lost to all predators combined should be lowest at the peak and possibly highest during the increase. During the 3 years of this study, loss of Canada goose nests was lowest at the peak but highest during the decline, and annual losses of white-fronted goose nests varied little. In cycles prior to this study, nest loss was high in declines but not particularly low during peaks. Several factors may alter the functional and numerical responses of predators, obscuring the simple pattern of nest loss predicted by the alternative-prey hypothesis.

Abundances of eye flukes (Diplostomum spp.) were compared between walleye (Stizostedion vitreum) and white suckers (Catostomus commersoni ) collected in late summer 1997 from Lake St. Louis and Lake St. Pierre, two expansions of the St. Lawrence River in Quebec, Canada. The white sucker, a benthic consumer, was more heavily in- fected than the walleye, a pelagic piscivore, in both lakes. Infection levels increased significantly with host age and size. For both species, abundance of Diplostomum spp. within each age group and length class was higher in fish from Lake St. Louis than in those from Lake St. Pierre. Walleye of all ages and white suckers ♢7 years old from Lake St. Louis were also larger at age than those of corresponding age from Lake St. Pierre. Therefore, walleye and white suck- ers from Lake St. Louis are probably different populations from those in Lake St. Pierre. The higher infection levels in Lake St. Louis are most likely due to the larger number of ring-billed gulls (Larus delawarensis), an important defini- tive host of Diplostomum spp., in colonies in close proximity to that lake; there are >75 000 pairs within 40 km of Lake St. Louis and 16 000 pairs within 40 km of Lake St. Pierre. No detrimental effects of infection with Diplostomum spp. could be detected on fish fork length, body mass, condition index, or gonadosomatic index. Walleye from shallow lentic waters in Lake St. Louis were larger and possessed heavier infections of Diplostomum spp. than those from deeper lotic waters. Walleye collected from a fixed trap near Quebec City in July 1997 were smaller but more heavily infected with Diplostomum spp. than those collected in October, which implies that different populations of fish may be present seasonally at this location. A visual index developed to measure the degree of opacity of the lens of fishes does not appear to be a reliable indicator of levels of infection with eye flukes. Experimental infection of laboratory- raised juvenile ring-billed gulls with metacercariae from the lenses of various fish species collected in the St. Lawrence River demonstrated that metacercariae were primarily Diplostomum indistinctum(84-92%), the remainder being Diplostomum huronense , and this pattern is consistent across host species and localities. 369 Resume : Nous avons compare l'abondance des douves de l'œil (Diplostomum spp.) chez le Dore jaune (Stizostedion vitreum) et le Meunier noir (Catostomus commersoni ), recoltes a la fin de l'ete 1997 dans le lac Saint-Louis et le lac Saint-Pierre, deux elargissements du fleuve Saint-Laurent au Quebec, Canada. Dans chacun des lacs, le Meunier noir, un poisson benthivore, etait plus fortement infecte que le Dore jaune, un predateur pelagique. La gravite des infections augmentait significativement avec la taille et l'âge du poisson hote. Chez les deaux especes, l'abondance de Diplo- stomum spp. dans chaque groupe d'âge et de taille etait plus elevee au lac Saint-Louis qu'au lac Saint-Pierre. Au lac Saint-Louis, chez les dores de tous âges et les meuniers de plus de 7 ans, la taille a un âge donne etait plus elevee que celles des poissons captures au lac Saint-Pierre. Ces resultats suggerent que les Dores jaunes et les Meuniers noirs du Lac Saint-Louis constituent des populations distinctes de celles du lac Saint-Pierre. Il est probable que la variation spa - tiale de la gravite des infections soit attribuable a la repartition des colonies du Goeland a bec cercle ( Larus delawa- rensis), un hote terminal important de Diplostomum spp., alors que plus de 75 000 paires ont ete denombrees dans un rayon de 40 km autour du lac Saint-Louis contre seulement 16 000 paires dans le cas du lac Saint-Pierre. Aucun im- pact negatif de l'infection par la douve de l'œil sur la sante des poissons n'a pu etre mis en evidence par l'examen de

During 1998 and 1999, the impact of predation by herring gulls (Larus argentatus) and great black-backed gulls (Larus marinus) on breeding success of black-legged kittiwakes (Rissa tridactyla) at Gull Island, Witless Bay, southeastern Newfoundland, was quantified in relation to the timing of the annual arrival of capelin (Mallotus villosus) to spawn. The frequency of predation attempts by large gulls on kittiwakes was compared among three periods: before the mean hatching date for herring gulls, between the mean hatching date for herring gulls and the arrival of the capelin, and following capelin arrival. The frequency varied significantly among the three periods, being highest after gull chicks hatched but before the capelin arrived. The frequency of gull predation was significantly correlated with the percentage of kittiwake eggs and chicks that disappeared each week. We estimated that 43 and 30% of kittiwake eggs and chicks at Gull Island were taken by gulls in 1998 and 1999, respectively. Kittiwakes have been indirectly (through increased predation by gulls) affected by the delayed arrival and lower abundance of capelin in recent years, which underlines the need to understand multispecies interactions when interpreting the effects of human alteration of the marine environment.

We performed a clutch-transfer experiment with herring gulls (Larus argentatus) to quantify how parental attributes and egg size affect chick growth and survival. The quality of parents was assessed by their average egg mass. There was no association between hatching success and egg mass in either unmanipulated or experimental nests. Among experimental treatments, the high-quality parents had a significantly higher chick survival rate than low-quality parents in 1991 and when data from 1990 and 1991 were pooled. A positive effect of egg size on chick survival was apparent only when data from both years were pooled. Chicks raised by high-quality parents had higher structural growth rates (tarsus) than chicks raised by low-quality parents. We discount the likelihood for selection of larger eggs because egg size has trade-offs with other life-history traits that have a strong influence on fitness. Despite the correlation between parental quality and chick survival, we doubt that there is character displacement for greater parental quality. Parental quality is probably affected by nutrition and is expected to have low heritability.

We examined the diet and growth of glaucous gull (Larus hyperboreus) chicks at Karrak Lake goose colony in 1994 and were especially interested in how these factors were affected by geese leaving the colony after goose hatch. Insects and bird prey each occurred in about 80% of regurgitated pellets during the first week after hatch of gulls. Thereafter, the frequency of insects in pellets diminished to

Glaucous gulls, Larus hyperboreus, are the primary predator of thick-billed murre, Uria lomvia, eggs at arctic breeding colonies. This study used eggs placed experimentally on murre nesting ledges to test the effects on glaucous gull foraging success of (i) murre nesting density; (ii) murre group defence; (iii) nesting ledge width; (iv) timing of murre laying; and (v) wind speed. Defensive responses by murres increased egg survival times, and gull foraging success was reduced by high murre nesting density. The timing of murre egg laying and ledge width also influenced the effectiveness of murre defence within the colony. Eggs placed following the peak of murre egg laying survived longer than eggs placed on the same nest sites prior to the peak. Murres without eggs early in the season often abandoned the group when attacked, leaving experimental eggs and brooding murres vulnerable to gulls. Gulls had difficulty reaching exposed eggs on narrow ledges when foraging on foot. At wind speeds greater than 15 km/h, however, egg survival was independent of ledge width because wind increased the maneuverability of gulls in flight and enabled them to reach narrow ledges. Murre defence at high nesting densities was also less effective on narrow ledges. Apparently, murres had difficulty rotating on their nest sites to face attacking gulls without dislodging their eggs. We conclude that moderate wind speeds enhanced the ability of gulls to reach narrow ledges and avoid contact with defending murres while stealing eggs. Consequently, the vulnerability of murre nest sites depended on wind conditions at the colony.

Endothermic thermoregulation is absent in birds until after hatching, and usually requires several hours or days to become fully functional in the young. Cold-induced vocalizations that elicit brooding by a cooperative parent or surrogate constitute an additional thermoregulatory mechanism potentially available to neonates of some avian and probably some mammalian species. We show that newly hatched ring-billed gulls (Larus delawarensis) and herring gulls (Larus argentatus) exposed in the laboratory to moderate chilling (20 °C) had a significantly improved ability to regulate body temperature when rewarmed (34 °C) for brief, 4-min periods in response to cold-induced vocalizations. Spontaneous calling by unchilled yoked controls was ineffective in maintaining body temperature. When chicks reached 3 days of age, vocally regulated temperaturee did not differ from that attained by thermogenesis, but vocally induced periods of rewarming reduced the duration of temperature challenge. The ability to regulate body temperature through vocalizations precedes the development of endothermy in gulls and other species so far examined, and in some species extends functional thermoregulation back to the late embryonic (pipped egg) stage of development.

Declines in Common Loon (Gavia immer) populations associated with increasing human use of lakes have been reported from many areas of North America. In the present report we describe a lake in northern Saskatchewan, Besnard Lake, where there has been a substantial increase in the number of loons, from about 85 in 1976–1979 to about 165 in 1990. A comparison was made with numbers of other birds associated with water. Increases were also seen in American White Pelicans (Pelecanus erythrorhynchos), Osprey (Pandion haliaetus), Great Blue Herons (Ardea herodias), Herring Gulls (Larus argentatus), Ring-billed Gulls (L. delawarensis), and Bonaparte's Gulls (L. Philadelphia). No change was seen in mergansers (Mergus merganser and M. serrator), Bald Eagles (Haliaeetus leucocephalus), or Common Terns (Sterna hirundo). The period 1976–1990 has also seen increased human use on Besnard Lake. The reason for increased loon numbers is uncertain, but could possibly be related to an increase in the numbers of small fish in Besnard Lake as a result of increased fishing pressure disproportionately removing the larger, predatory fish.

Although populations of Common Terns and Arctic Terns (Sterna hirundo, S. paradisaea) have been decreasing and gull (Larus spp.) populations have been increasing in eastern North America for more than 50 years, little is known about the population trends of these species in Newfoundland. Here we present data, spanning two decades, on the population trends and interactions of terns and gulls on five islands in Gros Morne National Park in western Newfoundland. Tern populations in this region are increasing despite interactions with gulls and low productivity. Immigration from disturbed colonies elsewhere is suggested as a possible source of the increase. Gull populations have also increased substantially since the early 1970s and closely follow local production of fisheries offal, as indicated by landing trends in the area. Implications for gull management strategies are discussed.

Young herring gulls (Larus argentatus) are known to emit vocalizations and approach their mew-calling parents when the latter return lo the colony with food for their chicks. In contrast, laboratory-reared young deprived of experience with adults approach and vocalize only rarely lo parental mew calls, although they will respond more strongly to the mew calls of two other species. These results suggest that posthatch experience, such as receipt of food from a calling parent, may be important for the normal development of responses to species typical calls. I tested the effects of food training by exposing young herring gulls, in the laboratory, lo mew calls during feedings. By 7 days of age, responses to herring gull calls increased significantly for young trained with these calls, and the initial tendency for the young to respond selectively to mew calls of the ring-billed gull (L. delawarensis) was reversed. Food training also influenced approach and vocal responses to a visual stimulus (my hand) used to deliver food. Results suggest that approach and vocal responses of young herring gulls may be strongly and adaptively influenced by food conditioning during the first few days after hatching.

Based on the morphology of adults recovered from experimental infection of gulls, the metacercariae from the eyes of lake whitefish were identified as Diplostomum spathaceum indistinctum and Diplostomum baeri bucculentum. The two species inhabit different sites in both fish and bird hosts:D. s. indistinctum in the lens and D. b. bucculentum in the vitreous humour and retina of lake whitefish and D. s. indistinctum in the anterior 20% and D. b. bucculentum in the anterior 60% of the intestine of gulls. Both species can be distinguished by differences in body size, ratios of forebody to hindbody, and position of ovary, and can be separated in mixed infections in gulls.

Biological characteristics and phenotypic variations of Trichinella spiralis var. pseudospiralis were determined from Crl: COBS CFW (Swiss Webster) mice, Coturnix coturnix japonica, Larus argentatus, L. delawarensis, and L. pipixcan. Trichinella spiralis var. pseudospiralis was located in the anterior part of the intestine of all hosts, but when surgically transplanted in mice the parasite did equally well in all sections of the small intestine. Differences in biological characteristics of T. s. var. pseudospiralis were noted between mouse and bird hosts and appear to be related to the more variable genome of the bird hosts, the nature of the digestive tract, and the intensity and timing of the host immune response. Larvae of T. s. var. pseudospiralis were concentrated in the muscles of legs, breasts, and thoracic and abdominal cavities. It was concluded that T. s. var. pseudospiralis may be a relatively recent parasite of birds that has limited chance for success.

Colonies of Common Puffins (Fratercula arctica), differing in numbers of breeding Herring Gulls (Larus argentatus) present, also differed in puffin numbers, burrow placement, and burrow activity rate. All differences indicated that puffins avoided gulls. Sites differing in gull numbers did not differ, however, in puffin fledging success or weights of fledged chicks. Chick weights and fledging success were low. The pattern of weight gain by chicks was irregular over the season, although consistent among sites for individual periods. These results imply that food usually was hard to find, although occasionally locally abundant. Pressures on puffin reproductive efforts due to variation in food supply and levels of kleptoparasitism do not appear to be additive; rather, low food availability decreases the effect of gull kleptoparasitism as well.

The substrate at a herring gull (Larus argentatus) colony on Lake Erie near Port Colborne, Ontario (Lighthouse), was completely covered by a thick layer of ice throughout April and early May 1982. Egg laying normally begins at this location in mid-April. An adjacent herring gull colony (Canada Furnace) was ice free. Herring gull pairs at the Lighthouse colony defended territories on top of the ice but only 3 of about 90 pairs built nests on the ice. Birds neither deserted the colony nor moved within it to ice-free areas as these became available. The mean date of egg laying at the Lighthouse colony in 1982 was about 2 weeks later than in the previous year. At the adjacent Canada Furnace colony, there was no difference in the mean date of egg laying between the 2 years. There were no differences in the distribution of clutch sizes, mean clutch sizes, or hatching success of three-egg clutches laid within ± 1 SD of the mean date of egg laying at either colony in the 2 years. By these measures, the ice-induced delay in breeding chronology of birds at the Lighthouse colony in 1982 did not adversely effect reproductive performance in that year.

Stable-carbon isotope analyses of bone collagen of gulls (Larus spp.) were used to estimate the relative proportion of marine and terrestrial protein in the diets of gulls that are known to use both types of food sources. Mean δ13C values for Glaucous-winged Gulls (n = 23) collected at a Vancouver dump and for Western Gulls (n = 18) from Southeast Farallon Island were −15.0 ± 1.3 and −15.1 ± 0.5‰, respectively. No significant difference in δ13C values was found between adult male and female Western Gulls. Archaeological gull bones (n = 3) show a mean δ13C value of −13.6 ± 1.0‰ and support the assumed marine end point of −13.0‰. The range of terrestrial protein in the diets of coastal gulls was 0–61%. The narrow distribution of δ13C values for Western Gulls from the Southeast Farallon Island colony suggests that gull colonies may be calibrated so that changes in dependence on terrestrial protein can be monitored.

Eulimdana juventarum n.sp. from Willets (Catoptrophorus semipalmatus (Gmelin)), Eulimdana asperum n.sp. from Wilson's Phalaropes (Phalaropus tricolor (Vieillot)), and Eulimdana pseudolari n.sp. from Red-necked Phalaropes (Phalaropus lobatus (L.)) in Canada are described. The name "Eulimdana lari (Yamaguti, 1935)" is restricted to filarioids described by Yamaguti from the Eastern Common Gull (Larus kamtschatschensis (Bonaparte)). Numerous reports of "E. lari" in other charadriiforms are probably incorrect, and new taxonomic studies of lemdanine filarioids in palaearctic charadriiforms are required. Eulimdana bibulbosa (Annett, Dutton, and Elliott, 1901) n.comb. is proposed for Filaria bibulbosa Annett, Dutton, and Elliott, 1901. The 11 species in Eulimdana and their host groups are listed. Adult worms of the three new species occurred in subcutaneous tissues of the neck and connective tissues around the trachea and oesophagus. Microfilariae of E. juventarum and E. asperum occurred in skin, and skin-inhabiting microfilariae may be common in charadriiform birds. Microfilariae of E. asperum were also found in blood, but less frequently than in skin. Microfilariae of E. pseudolari were found in blood but probably occur in both blood and skin; skin was not examined. Prevalence of infection will be underestimated if hosts are examined only for microfilariae as sterile infections (those with only male or only female worms) are common. Adult worms in patent infections (those with mocrifilariae) apparently are short-lived and then completely resorbed by the host. In late patency infections, therefore, skin-inhabiting microfilariae occur in the absence of adult worms. Patent infections probably produce a protective immunity. Amblyceran lice probably transmit species of Eulimdana in the Charadriiformes.

Cosmocephalus obvelatus (Creplin, 1825), found in the oesophagus of ring-billed gulls (Larus delawarensis Ord), from Lake Ontario developed to the infective stage in the haemocoel of the amphipods Crangonyx laurentianus, Hyalella azteca, and Gammarus fasciatus. At 20 °C the first moult occurred 10 days and the second 18 days postinfection. Infective larvae given to laboratory-reared herring (Larus argentatus) and ring-billed gulls entered the proventriculus of the birds and moulted 3.5 days postinfection. Five days postinfection, fourth-stage larvae were found attached to the posterior third of the oesophagus. The fourth moult occurred 11 days postinfection and worms were found throughout the oesophagus. Females were gravid 27 days postinfection. Various developmental stages are described. Infective larvae became encapsulated on the mesentery of experimentally infected goldfish (Carassius auratus) and a shiner (Notropis sp.). Infective larvae were found in various fish collected in waters adjacent to the gull colony. Regular examination of adult gulls indicated birds acquired infections soon after arriving from the wintering grounds. There was little evidence transmission occurred in the latter regions. Young-of-the-year birds acquired infections by (1) regurgitation of fourth-stage larvae and adult worms along with food during feeding by parents and (2) from infective larvae contained in the fish given to them by the parents. Prevalence in 28-day-old birds had reached 100%. Intensity (including all stages) in fledglings 35–42 days old on July 3 was 15.7 (6–38).

The costs and benefits to Red-breasted Mergansers (Mergus serrator) nesting in a Common Tern (Sterna hirundo) colony and a Herring Gull (Larus argentatus) and Great Black-backed Gull (L. marinus) colony were studied from 5 June to 17 August 1984 on islands off the east coast of New Brunswick. Merganser nests outside larid colonies were preyed upon significantly more than nests in the tern colony while no difference was found with nests in the gull colony. Nests in the tern colony were more densely concentrated and more likely to be abandoned. Clumped nests in the tern colony were not initiated in greater synchrony than dispersed nests. The merganser–gull nesting association is discussed. We postulate that the protective benefit for merganser nests in tern colonies accounts for the evolution of the nesting association.

Liver vitamin A was analysed by reverse phase high pressure liquid chromatography in a limited number of herring gull samples collected from New Brunswick coastal and Great Lakes colonies. Both retinol and retinyl palmitate concentrations were significantly different between the New Brunswick and Great Lakes colonies as well as among the Great Lakes colonies. The highest mean values were 864 and 1737 μg/g retinol and retinyl palmitate, respectively, occurring in the New Brunswick gulls. The lowest mean values were 131 and 231 μg/g retinol and retinyl palmitate, respectively, which were detected in Lake Ontario gulls. Retinoid levels were inversely related to the extent of dioxin contamination reported previously. Ring doves received single low-level doses of the dioxin analogue 3,4,3′,4′-tetrachlorobiphenyl and were sacrificed at various times postinjection. Liver retinol decreased significantly as aryl hydrocarbon hydroxylase activity increased. The decrease in retinol concentration was not related to UDP-glucuronyltransferase activity. Retinyl palmitate was unaffected by the analogue under the conditions of this study. These results support the hypothesis that, in wildlife species, hepatic retinoid metabolism is affected by chlorinated dibenzodioxins or other contaminants capable of inducing aryl hydrocarbon hydroxylase.

The adaptive significance of asynchronous hatching in the Herring Gull, Larus argentatus, was examined during the summer of 1984 at Kent Island, New Brunswick. Chick growth and behaviour in 28 experimental three-egg clutches in which the eggs hatched synchronously (i.e., hatch interval ≤ 24 h between the first (A chick) and last (C chick) hatched) were compared with that of 15 control three-egg nests with normal hatching asynchrony (A–C hatch interval > 24 h). All chicks had similar hatch weights, except for control C chicks, which on average were significantly lighter than their nest mates and experimental chicks. Growth rates were also similar for all chicks within and between groups, except for control C chicks, which grew at a significantly slower rate compared with nest mates and experimental chicks. In control broods, C chicks disappeared first significantly more often than A or B chicks. In experimental broods, a similar proportion of A, B, and C chicks disappeared first. Survivorship, through to day 5 posthatch, was significantly lower for control C chicks than for control A and B chicks as well as experimental chicks. These results suggest that the benefit Herring Gulls achieve hatching their eggs asynchronously results from the competitive advantage accrued to the A chick (and the B chick to some degree), which allows them to obtain more food, especially during periods of food stress. Subsequently the probability of survival of the older, more fit chick(s) is enhanced.

During a fish parasite survey in 1980 and 1981, 395 yellow perch (Perca flavescens) were removed from the Heming Lake study area (54°53′ N, 101°07′ W). Encysted Apophallus brevis metacercariae were found in the body musculature of perch from six lakes as well as the eye and body musculature of perch in Heming Lake. Species identity was confirmed with experimental infections in ring-billed (Larus delawarensis) and herring (Larus argentatus) gulls. No significant differences were found in prevalences or mean intensities of A. brevis metacercariae between male and female perch in Heming Lake. Prevalence levels remained high in most age-classes of Heming Lake perch and mean intensity differences were not significant for all ages beyond 1 year old. Slight variations from these Heming Lake results were found in other lakes. Prevalence levels of A. brevis in Heming Lake perch remained more or less constant during the open water seasons. Mean intensities dropped significantly from June to July and increased in August and October. Monthly fluctuations are probably the result of recruitment of the parasite and a loss of heavily infected hosts. The variance to mean ratios of A. brevis in perch from Heming, Home, and Demarch lakes showed that these parasite populations were overdispersed, and the distribution of each was found to fit the negative binomial. The authors question the use of variance to mean ratios or other statistics dealing with overdispersion in predicting loss or recruitment for all parasite systems.

Metacercariae of the genus Diplostomum, recovered from the eyes of the least cisco, Coregonus sardinella, were used to experimentally infect chicks of ring-billed gulls, Larus delawarensis, and herring gulls, Larus argentatus. Adults recovered from the intestine of these gulls were identified as Diplostomum baeri bucculentum based on size characteristics and the position of the anterior margin of the vitellaria to at least the level of the ventral sucker. An analysis of morphological characters from 258 gravid specimens showed a greater range in measurements than previously reported for this species. Moreover, characters such as egg numbers and size and shape components were strongly influenced by host effects. There does not appear to be the extensive geographic variability in morphology that is known for other helminth groups.

Herring Gulls (Larus argentatus) varied their rates of kleptoparasitic attack depending on Common Puffin (Fratercula arctica) foraging success. Attacks were more frequent on days when many puffins brought back food. However, puffins also varied their behaviour when approaching nest sites with food, so the rate of food loss to gulls per puffin remained constant as the number of puffins with food increased. Site differences in puffin activities after landing reflected only direct consequences of puffin and gull abundances and slope topography. After chick provisioning commenced, puffins at all sites showed increased vigilance after landing and more rapid burrow entries. Behaviour of puffins when approaching the slopes showed adaptations to the presence of gulls. On days when many puffins had food, puffins in areas of high gull density swamped the kleptoparasite. On days when few had food, puffins approached the slopes much as they did before chick provisioning commenced. Hosts as well as kleptoparasites may show closely tuned adaptations to potential food supply and likelihood of attacks.

Sable Island, Nova Scotia, is the southernmost significant nesting area of the Least Sandpiper. Many birds nest around a single pond complex, which supports a lush vegetation that is heavily grazed by horses. Nests occur there and in nearby dry, sparsely vegetated habitat. Birds start arriving by mid-May (males first), and clutches (including replacement clutches) are completed in a period of 4–5 weeks, from late May to late June. Most eggs are laid in the morning, at intervals averaging 1.2 days. Incubation increases gradually through laying and is ~100% beginning with the last egg. Incubation lasts 20–21 days. Nest and chick mortality is high, mostly due to predation by Herring Gulls (Larus argentatus). Mortality of siblings is contagious. Females which nest successfully begin to migrate south by late June, followed by successful males in early July; individuals of both sexes are seen for about 3 days after the completion of parental behavior. Unsuccessful breeders leave earlier, and fledglings later. On average, males are seen for about 10 days and females for about 7 days following final breeding failure. Adults and fledglings tend to flock assortatively in late summer. General features of the breeding cycle seem to be highly conservative throughout the species' range.

The variability of adult Leucochloridium sp. from Norway (63°35′ N,9°45′ E) recovered from natural infections in Larus canus L. and experimental infections in L. canus and Taeniopygia guttata (Vieillot) was studied by light microscopy. The results are compared with five species (Nearctic and Palaearctic) having an experimentally known sporocyst stage (brown-banded brood sacs), and with eight other species with unknown intermediate stage, but placed in the genus Leacochloridium s.str. The five adult species (Leucochloridium variae McIntosh, 1932; Leucochloridium fuscostriatum Robinson, 1947; Leucochloridium perturbatum Pojmanska, 1969; Leucochloridium subtilis Pojmanska, 1969; Leucochloridium fuscum Rietschel, 1970) together with the Norwegian material are regarded as belonging to one species, the Nearctic Leucochloridium variae. The variability and validity of the characters used are discussed.

Four hundred and ten herring gulls (128 chicks and 282 "adults"), obtained in Newfoundland, Canada, were examined for their helminth burden during 1966 and 1967. A total of 35 species of helminths were recovered during the survey (11 species of trematodes. 10 of cestodes, 11 of nematodes, and 3 of acanthocephala). Many of the records are new for Canada."Adult" birds were found to be far more heavily parasitized than the chicks, both with regard to number of birds infected and number of species per infected bird. Seasonal and annual variations were noted in the intensity of infection with certain species, while differences in the intensity of infection in male and female birds were noted in eight species. The helminths found were shown to have definite site preferences in the host animal.

Cosmocephalus firlottei n. sp. (Family Acuariidae, subfamily Acuariinae) is described from the sea gull, Larus argentatus.

Paracuaria macdonaldi n.g., n.sp. (family Acuariidae, subfamily Acuariinae) is described from the sea gull, Larus argentatus.

Six species of cestodes are recorded from 21 herring gulls in New Brunswick, Canada. Five of these are redescribed while the other, representing a new species, is described for the first time. Three of these species are recorded from Canada for the first time and one species represents a new host record.

Echinochasmus cohensi n.sp. (family Echinostomidae, subfamily Echinochasminae) is described from the sea gull, Larus argentatus Brünn.

The helminth fauna of California and ring-billed gulls at Beaverhill and Miquelon lakes, Alberta, was studied. The extensity of the occurrence of Plagiorchis elegans, Diplostomum spathaceum, Hymenolepis californicus, and Aprocta turgida and the intensity of Plagiorchis elegans and Paricterotaenia porosa were significantly greater in the ring-billed gull than in the California gull. The greater occurrence of Diphyllobothrium dendriticum, Schistocephalus solidus, Diplostomum spathaceum, and Cotylurus erraticus in the ring-billed gull indicates that this bird eats more infected fish, in the vicinity of Beaverhill and Miquelon Lakes, than does the California gull.

New molluscan, crustacean, and avian hosts were found for four species of digenetic trematodes in Vancouver, British Columbia, from 1973 to 1977. The rediae and cercariae of Parorchis acanthus (Nicoll) were discovered in Nucella lamellosa (Gmelin). Adults were recovered after 19 days from experimental feedings of the metacercariae to a newly hatched domestic chick. The cercariae of Cryptocotyle lingua (Creplin) from the snail Littorina scutulata Gould were used to infect young fish, Leptocottus armatus Girard, Oligocottus maculosus Girard, and Platichthys stellatus (Pallas). These fish, infected with the metacercariae, were fed to newly hatched gulls, Larus glaucescens Naumann, and mature worms were found in the anterior half of the intestine after 14 and 21 days. The metacercariae of Maritrema megametrios Deblock and Rausch, found in Orchestia traskiana Stimpson and Gnorimosphaeroma oregonense (Dana), became ovigerous in Locke's solution at 40 °C at 48 h. Natural infections were found in Larus Philadelphia (Ord). The metacercariae of Maritrema gratiosum Nicoll, found in Balanus glandula Darwin, also became ovigerous in vitro. Adults were found with two other microphallid species in the intestine of one Bucephala islandica (Gmelin).

Two groups of ectoparasites, namely Mallophaga and Acarina, were recovered from 47 Larus argentatus, 29 Rissa tridactyla, and 18 Oceanodroma leucorhoa taken on Gull Island, Witless Bay, Newfoundland, during the period June–August 1974. Mallophaga of the genera Saemundssonia and Quadraceps (Ischnocera) were found to be common ectoparasites of both L. argentatus and R. tridactyla and the genera Halipeurus (Ischnocera) and Austromenopon (Amblycera) were recovered from O. leucorhoa. A single ixodid tick, Ixodes (Ceratixodes) uriae, was recovered from an R. tridactyla chick. Only O. leucorhoa were found to harbour feather mites, these belonging to the genera Zachvatkinia, Brephosceles, Connivelobus, and Ingrassia.Details on the degree of infestation of the birds are given as well as the distribution of each ectoparasite species on the hosts.

Maritrema pacifica n. sp. has an incomplete posterior ring of vitellaria, a spiny cirrus, a trilobed ovary, and a well-differentiated metraterm. It differs from M. patulus Coil, 1955 in the larger body, longer esophagus, round rather than slit-like genital pore, and larger eggs. It differs from M. interrupta Oshmarin, 1970, M. eroliae Yamaguti, 1939, and M. kitanensis Shibue, 1953 in the smaller cirrus sac containing sparse prostate cells. M. pacifica has the following definitive hosts: Larus californicus Lawrence, L. occidentalis Audubon, Turdus migratorius L. from Oregon, and Crocethia alba (Pallas) from British Columbia. The metacercariae, from Orchestoidea corniculata from California, became ovigerous in Locke's solution at 39 °C.Maritrema paracadiae n. sp. (synonym M. acadiae of Deblock and Rausch (1972)) differed from the type specimens of M. acadiae (Swales, 1933) in the proportionately larger oral and ventral suckers; the larger, inverted J-shaped cirrus sac containing prominent prostate cells; and the distribution of the uterus within, instead of overlapping, the posterior vitellarian ring. M. paracadiae was found in the intestine of Bucephala islandica (Gmelin) from Washington.

Forty-two perch eyes (Perca flavescens) infected with metacercariae of Diplostomum adamsi were fed to a herring gull (Larus argentatus). Eighty adults were recovered from the intestine 10 days later. They were characterized by their small size (1.5 to 2.1 mm), asymmetrical anterior testis, and the absence of vitellaria in forebody anterior to the middle of the ventral sucker.Eggs of D. adamsi passed by the gull embryonated in 22 days at 22 °C and hatched when exposed to light. Miracidia penetrated snails of the species Lymnaea elodes and L. stagnalis. Forty days later straight-tailed cercariae with six pairs of caudal bodies were released from both lymnaeids. They penetrated and developed in P. flavescens but not in Salvelinus namaycush, Catostomus commersoni, Semotilus atromaculatus, or Carassius auratus. In P. flavescens, metacercariae were found in clusters in the peripheral retina, in a cavity between the photoreceptor cells and the pigment epithelium. The photoreceptor cells were disorganized but not destroyed, unlike those in the eyes of Gasterosteus aculeatus parasitized by D. scudderi.

Thirty-two great black-backed gulls (Larus marinus), 72 kittiwakes (Rissa tridactyla), and 1 glaucous gull (Larus hyperboreus) were examined for their helminth parasite burden during 1966 and 1967, in Newfoundland, Canada. A total of 16 species of helminths were recovered (four species of trematodes, nine of cestodes, and three of nematodes). The great black-backed gull was found to be infected with 14 species of helminth, the kittiwake with five, and the glaucous gull with four. The records in this paper are new for Canada, and two are new North American records. No annual or seasonal differences were noted in the parasite burden, nor was there any significant difference between the burden of chicks and adults, or males or females.