Feeding behavior and modeled energetic intake of common loon (Gavia immer) adults and chicks on small lakes with and without fish

We examined the behavior of common loons, Gavia immer (Brünnich), breeding on small, shallow lakes in central Alberta, Canada that were naturally fishless or contained only small-bodied fishes (minnow lake). For both lake types, adults spent >90% of their time on the nesting lake and >50% of their time foraging. Adult loons on fishless lakes dove more frequently, but dives were of shorter duration than loons on lakes with fish. On two intensively studied fishless lakes, adults fed chicks macroinvertebrates, particularly leeches, whereas on a focal minnow lake, fish made up >70% of prey items delivered by adults. Chicks >36 days of age on a minnow lake spent >50% of their time foraging, whereas older chicks on fishless lakes were highly dependent on food provisioning by adults. Models based on observed foraging patterns indicated that prey size was a better predictor of success in meeting energetic requirements than was feeding behavior (e.g., dive rate, dive success). For most models, estimated energetic intake was higher for loons on minnow lakes than on fishless lakes. Our behavioral observations and model results are consistent with surveys in central Alberta that indicate that breeding Common Loons frequently establish territories on small lakes, but that chicks hatched on lakes completely lacking fish rarely fledge and only if sufficient large invertebrates such as leeches are available.     

The oral bioavailability and toxicokinetics of methylmercury in common loon (Gavia immer) chicks

We compared the toxicokinetics of methylmercury in captive common loon chicks during two time intervals to assess the impact of feather growth on the kinetics of mercury. We also determined the oral bioavailability of methylmercury during these trials to test for age-related changes. The blood concentration-time curves for individuals dosed during feather development (initiated 35 days post hatch) were best described by a one-compartment toxicokinetic model with an elimination half-life of 3 days. The data for birds dosed following completion of feather growth (84 days post hatch) were best fitted by a two-compartment elimination model that includes an initial rapid distribution phase with a half-life of 0.9 days, followed by a slow elimination phase with a half-life of 116 days. We determined the oral bioavailability of methylmercury during the first dosing interval by comparing the ratios of the area under the blood concentration-time curves (AUC(0--> infinity )) for orally and intravenously dosed chicks. The oral bioavailability of methylmercury during the first dosing period was 0.83. We also determined bioavailability during both dosing periods using a second measure because of irregularities with intravenous results in the second period. This second bioavailability measure estimated the percentage of the dose that was deposited in the blood volume (f), and the results show that there was no difference in bioavailability among dosing periods. The results of this study highlight the importance of feather growth on the toxicokinetics of methylmercury.     

Factors influencing productivity of common loons (Gavia immer) breeding on circumneutral lakes in Nova Scotia, Canada

Common loons (Gavia immer) are top predators that are sensitive to biotic and abiotic conditions associated with their breeding lakes, so factors such as lake chemistry and human activity or disturbance are thought to influence their seasonal and long-term reproductive success. We used two indices of loon productivity to evaluate (1) temporal patterns and (2) relationships with physical and chemical lake characteristics and human activities. Data collected from 1991 to 2000 by volunteers of the Canadian Lakes Loon Survey (CLLS) in Nova Scotia showed that loon productivity, as indexed by both the proportion of resident pairs that produced at least one large young (P_s1) and the proportion of successful pairs that produced two large young (P_s2), did not vary substantially from year to year and showed no linear trend from 1991 to 2000. Average estimates (1991–2000) for P_s1 and P_s2 were 0.49 ± 0.02 and 0.43 ± 0.03, respectively, and the mean number of chicks per residential pair over that time was 0.75 ± 0.04. We found that human disturbance and shoreline development did not influence loon productivity during the prefledging stage on lakes surveyed by CLLS volunteers. Proportion of resident pairs rearing at least one large young was independent of dissolved organic carbon (DOC) concentrations of breeding lakes, but there was a positive relationship between the proportion of successful pairs rearing two large young and DOC. Both indices of loon productivity tended to be negatively correlated with lake pH. These results were not consistent with other findings that loon productivity generally declines with lake acidity, but likely reflect the preponderance of circumneutral (pH 6.5–7.0) lakes surveyed by the CLLS volunteers in Nova Scotia.     

Bioaccumulation of mercury in yellow perch (Perca flavescens) and common loons (Gavia immer) in relation to lake chemistry in Atlantic Canada

Mercury biomagnifies in aquatic foodwebs in freshwater lakes, and common loons (Gavia immer) breeding in eastern Canada can be exposed to reproductively toxic concentrations of mercury in their fish prey. We assessed the bioaccumulation and biomagnification of mercury in juvenile and adult common loons, and their preferred prey: yellow perch (Perca flavescens) in Kejimkujik National Park (KNP), Nova Scotia by measuring mercury levels and stable isotope ratios in tissues. Total mercury levels and stable-carbon (δ¹³C) and nitrogen isotope ratios (δ¹⁵N) were determined in composite whole-fish samples from lakes in KNP and blood samples from juvenile and adult loons captured on lakes in KNP and southern New Brunswick. Geometric mean mercury concentrations were 0.15 and 0.38 μg/g (wet wt.) in small (9-cm fork length) and large (17-cm fork length) yellow perch, and were 0.43 and 2.7 μg/g (wet wt.) in blood of juvenile and adult common loons, respectively. Mercury concentrations in perch and loons were positively associated with body mass and δ¹⁵N values. Juvenile loons and large yellow perch had similar mercury levels and δ¹⁵N values, indicating similar trophic status despite their 22-fold difference in body mass. Mercury concentrations were higher in yellow perch and common loons in acidic lakes. Our findings highlight the importance of both chemical and ecological factors in understanding mercury biomagnification in lakes and associated risks to fish-eating wildlife. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Testing hypotheses of social gatherings of common loons (<Emphasis Type="Italic">Gavia immer</Emphasis>)

Three hypotheses are tested to explain the function of common loon social gatherings: Cooperative Foraging, Familiarity, and Reconnaissance. From 1993 to 1999, I studied social gatherings through behavioral observations in Michigan, Wisconsin and Maine. There was no or little evidence for the Cooperative Foraging Hypothesis. Partial or indirect evidence for the Familiarity Hypothesis included the following: (1) Social gatherings lasted both longer and occurred more frequently later in the breeding season (2) Approximately 25% of all the social gatherings observed occurred on neutral territories, and (3) Social gatherings consisted of the same individuals on consecutive days. Predictions from the Reconnaissance Hypothesis were also supported in that a large proportion of individuals participating in social gatherings were non-breeders and that the number of social gatherings observed were not equally distributed across loon territories, but instead increased on territories that had recently undergone a divorce. No one hypothesis was adequate to explain social gatherings and more observations on uniquely marked individuals are needed to further substantiate these initial findings.     

Activity budgets and use of enclosed space by wild boars (Sus scrofa) in captivity

This research was conducted on a captive group of eight wild boars: Four wildborn adults (one male and three females) and four piglets (one male and three females), born in captivity two months before the beginning of the study. They were housed in the Rome Zoo in a 1,000 sq m enclosure furnished with trees, mud pools, a water basin, and two small barns. Data on eight behavioral states (sleeping, resting, rooting, eating, walking, standing, scratching, and nursing) were collected by instantaneous sampling at 10-minute intervals. The spatial location of each subject was also noted, as well as closeness to conspecifics. Results showed that adults and piglets differed in their activity budgets. Activity patterns showed a significant correlation with the mean temperatures. Furthermore, there was a significant difference in the use of the exhibit areas between adults and piglets. This study suggests a social structure in which the core is constituted by females and their yearlings. The nonbreeding female has a more marginal position than the breeding ones. Finally, the male tends to be even more peripheral and solitary. Our results are partly consistent with the data obtained in studies on free-ranging wild boars (Mauget, 1980; Dardaillon, 1984).     

Potential risk to common loons (Gavia immer) from methylmercury exposure in acidified lakes

Piscivorous birds and mammals in areas remote from point sources of Hg contamination may be exposed to dietary methylmercury concentrations that are sufficiently high to cause reproductive impairment. Common loons (Gavia immer) were observed to show aberrant nesting behavior and low overall reproductive success when Hg concentrations in prey (small fish and crayfish) averaged > 0.3 µg g^–1 wet weight (Barr, 1986), levels known to occur in fish from many lakes in central Ontario. We used data on Hg in Ontario fish to estimate the proportion of lakes where fish small enough for loons to eat (< 250 g) had Hg concentrations that exceeded estimated thresholds for reproductive impairment. Up to 30 % of lakes exceeded thresholds for reproductive impairment, depending on the species of fish and the threshold Hg concentrations chosen. There was a significant negative correlation between fish-Hg concentration and lake pH in most fish species examined. For these species, reductions in sulfate deposition rates are predicted to result in a corresponding reduction of lakes in Ontario having fish with potentially toxic concentrations of Hg.     

Activity budgets and use of exhibit space by South American tapir (Tapirus terrestris) in a Zoological Park setting

Six individuals of Tapirus terrestris (two adult males, one juvenile male, and three adult females) were observed the first three months of 1982 at Audubon Park and Zoological Garden. Data for fourteen behavioral states were collected by scan sampling at ten-minute intervals throughout the day and twice throughout the night in an open air, mixed-species exhibit. The data were analyzed to calculate activity budgets and space use. Sleeping, eating, foraging, walking, and standing made up the major portions of the activity budgets. “Natural” activity patterns, as in the wild for browsing ungulates, were displayed under captivity in variously modified form. The characteristics of an individual, especially the reproductive state, affected both activity budget and space use. Zoo regimen significantly modified activity budgets and space use by the animals.     

An outbreak of type E botulism among common loons (Gavia immer) in Michigan's upper peninsula

An epizootic of type E botulism (Clostridium botulinum) occurred among common loons (Gavia immer) along the Lake Michigan shore of Michigan's Upper Peninsula (USA) during October and November 1983. An estimated 592 dead loons washed ashore along the Garden Peninsula. Type E botulinal toxin was demonstrated in blood samples and stomach contents of dead loons, and in samples of three species of dead fish found on the Lake Michigan shore. We suspect that loons acquired botulism by ingesting sick or dead fish containing type E toxin.     

Aspects of Common Loon (Gavia immer) feeding biology on its breeding ground

Field studies and experiments with hand-reared loons found loons to be facultative predators, foraging on a variety of fishes, crustateans and other aquatic animals. Loons selected certain species and size of prey when present, favoured fusiform shapes and atypical, erratic swimming behavior, but took the most readily available and susceptible to capture, often yellow perch. Chick feeding behaviour developed during the first 8 wks after which physical maturity permitted independent feeding. Juveniles resembled adults in size and shape by wk-11, and were capable of catching all of their own food. Evidence suggests that loons are not harmful to sport fisheries and may ba beneficial by supressing species competing with game fish.Territories averaged 72 ha, and food may be a determinant for maximum size. Based on the average amount of food required by a chick for its first 15 wks (53 kg), plus the daily consumption of older birds (960) g, a pair of loons rearing 2 chicks could remove about 423 kg of food during 5.5 months on territory.     

Antimicrobial resistant Salmonella spp. isolated from double-crested cormorants (Phalacrocorax auritus) and common loons (Gavia immer) in Florida.

Antimicrobial resistant Salmonella spp. were found in double-crested cormorants and common loons in Florida. Single or multiple resistance occurred in all Salmonella agona isolates from cormorants, primarily to ampicillin, sulfonamids, streptomycin, neomycin, and kanamycin. Similar patterns of resistance were found in S. agona isolates from common loons. In addition, isolates of S. Saint paul from loons were found resistant to tetracycline and streptomycin, while 2 of 7 isolates of S. infantis were resistant to tetracycline only.     

Susceptibility to freshwater acidification by two species of loon: Red-throated Loon (Gavia stellata) and Arctic Loon (Gavia arctica) in southwest Sweden

In southwest Sweden, the two species of loon, Gavia stellata and G. arctica, have shown different trends in population size and production of young during the last decades. Both species fish in oligotrophic freshwaters, susceptible to acidification. The number of breeding sites occupied by G. stellata has been reduced by almost 50% during the last 40–50 years. For G. arctica, there are no indications of significant declines in population size or reproductive success during the last 20 years. The different trends in numbers and production of young might reflect different susceptibility to the ecological changes in acidified lakes. G. stellata prefer fishing lakes with high abundance of Acerina cernua and salmonid and cyprinid fish, such as Coregonus albula and Rutilus rutilus. They also feed their prefledged chicks almost entirely on cyprinid and salmonid fish. G. arctica prefer fishing lakes with high transparency and, when feeding in groups, high abundance of Perca fluviatilis. Their young can be fed on aquatic insects as a supplement to the fish diet. Thus, G. stellata to a higher degree than G. arctica relies on fish which are susceptible to low pH, and G. arctica may also benefit from the increased abundance of aquatic insects in lakes with reduced predation from fish. Furthermore, high water transparency is important for the selection of lakes by G. arctica but not by G. stellata. In G. stellata, high contents of mercury in eggs can be related to the intake of fish in lakes affected by acidification.     

Prospecting in a solitary breeder: chick production elicits territorial intrusions in common loons

In many species, young animals learn about various breedingpatches in one year and use what they have learned to settlein a promising patch the next. Common loons (Gavia immer) seemgood candidates for such prospecting as prebreeders and displacedbreeders intrude frequently into breeding territories defendedby monogamous pairs yet engage in no extrapair copulations.We tested 3 hypotheses for prospecting in loons. The permanentattributes hypothesis gained little support as we found no consistentdifferences in quality between territories and no physical orbiotic trait that predicted reproductive success in a territory.We found some support for the conspecific attraction hypothesisas intruders were attracted to conspecifics in a lake in theshort term; however, intrusions were not more frequent in territoriesthat had experienced regular use by a pair the previous yearthan in territories that had previously been vacant. Instead,the increase in intrusion rate after a year of chick productionsupported the habitat-copying hypothesis, which states thatfloaters use the presence of chicks as a cue to target territoriesfor future attempts at territorial takeover. Despite this systemof prospecting, founding of new territories was common. Onestriking finding was the tendency of territorial breeders toconceal chicks from flying intruders, perhaps to avoid futureterritorial takeover.     

Inter-population differences in the time budgets of bonnet monkeys (Macaca radiata)

Time budgets for five major activities viz., Passive Sitting, Locomotion, Foraging, Social Behaviour, and Self-directed Behaviours were recorded for bonnet monkeys inhabiting forest, urban, and rural habitats. The time budgets were further classified into those of various age-sex classes. Significant inter-population differences were found in group size, social behaviour, foraging, and locomotion, which are discussed in relation to the habitat features.     

Detection and phylogenetic characterization of a novel herpesvirus from the trachea of two stranded Common Loons (Gavia immer)

Two wild adult Common Loons (Gavia immer) were evaluated after being found stranded in mainland north-central Florida on separate occasions. On the basis of upper airway endoscopic and cytologic findings, we diagnosed severe ulcerative tracheitis antemortem in one of the birds while more subtle lesions were observed in the other. A novel herpesvirus was detected in antemortem tracheal samples using nested consensus PCR amplification of the polymerase gene and sequencing. Despite prolonged intensive medical care, the bird with severe lesions failed to improve and was euthanized 9 days after endoscopy. No viral inclusions were evident histologically in the lesions. However, an undulating tracheal mucosa in a "mountain ridge" pattern, resulting from epithelial regeneration and hyperplasia, was present, as is seen in the late stages of infectious laryngotracheitis in chickens. The second bird recovered and was released. The genetic distance between this and other characterized herpesviruses supports placement of this virus as a novel species, referred to as Gaviid herpesvirus 1 (GavHV1). Phylogenetically, GavHV1 clusters within the genus Iltovirus. The relationship between the observed lesions and the virus remains to be demonstrated.     

Use of boreal forested wetlands by Pacific loons (Gavia pacifica Lawrence) and horned grebes (Podiceps auritus L.): relations with limnological characteristics

Our objective was to determine if the occurrence and abundance of Pacific loons (Gavia pacifica Lawrence) and horned grebes (Podiceps auritus L.) on 123 wetlands of Yukon Flats National Wildlife Refuge in east central Alaska were related to the limnological characteristics of those wetlands. Aquatic bird-wetland use surveys were conducted in conjunction with limnological sampling from May through September 1985–87 and May through August 1989. Results from logistic regression analysis demonstrated a significant association between the probability of wetland use by Pacific loons and shoreline length, water color, calcium and total phosphorus. Wetland use by horned grebes was related to shoreline length, pH, and chlorophyll. Aquatic bird abundance was then used as a Poisson response variable and modeled as a function of wetland limnological characteristics. Our results indicate that Pacific loon abundance was adequately modeled by linear and quadratic functions of shoreline length, color, pH, calcium and total phosphorus. Horned grebe abundance could not be modeled with this approach. The statistical techniques known collectively as generalized linear models provided a framework for the development of models for aquatic bird use of wetlands. Our results, however, indicate that while this approach shows promise, a better understanding of how to model aquatic bird abundance is needed. We then identify problems in model development and suggest avenues for future research.Contribution of the Missouri Agricultural Experiment Station Journal Series No. 11604.     

Diurnal time-activity budgets of redheads (Aythya americana) wintering in seagrass beds and coastal ponds in Louisiana and Texas

Diurnal time-activity budgets were determined for wintering redheads (Aythya americana) from estuarine seagrass beds in Louisiana (Chandeleur Sound) and Texas (Laguna Madre) and from ponds adjacent to the Laguna Madre. Activities differed (p<0.0001) by location, month, and diurnal time period. Resting and feeding were the most frequent activities of redheads at the two estuarine sites, whereas drinking was almost nonexistent. Birds on ponds in Texas engaged most frequently in resting and drinking, but feeding was very infrequent. Redheads from the Louisiana estuarine site rested less than birds in Texas at either the Laguna Madre or freshwater ponds. Redheads in Louisiana fed more than birds in Texas; this was partially because of weather differences (colder temperatures in Louisiana), but the location effect was still significant even when we adjusted the model for weather effects. Redheads in Louisiana showed increased resting and decreased feeding as winter progressed, but redheads in Texas did not exhibit a seasonal pattern in either resting or feeding. In Louisiana, birds maintained a high level of feeding activity during the early morning throughout the winter, whereas afternoon feeding tapered off in mid- to late-winter. Texas birds showed a shift from morning feeding in early winter to afternoon feeding in late winter. Males and females at both Chandeleur Sound and Laguna Madre showed differences in their activities, but because the absolute difference seldom exceeded 2%, biological significance is questionable. Diurnal time-activity budgets of redheads on the wintering grounds are influenced by water salinities and the use of dietary fresh water, as well as by weather conditions, tides, and perhaps vegetation differences between sites. The opportunity to osmoregulate via dietary freshwater, vs. via nasal salt glands, may have a significant effect on behavioral allocations.     

Activity budgets in a group of Sichuan snub-nosed monkeys in Shennongjia Nature Reserve, China

We examined time allocation by Sichuan snub-nosed monkeys Rhinopithecus roxellana in the montane,temperate and highly seasonal forests of the Shennongjia Nature Reserve in China,in order to improve our understanding of the ecological and social influences on monkey behavior.We collected data on activity budgets in relation to food availability in a group of monkeys from July 2003 to September 2004(except February 2004),using instantaneous scan samples.The monkeys spent 36.21% of daytime moving(n=21,269 reco...     

Enclosure utilization,activity budgets,and social behavior of captive chamois (Rupicapra rupicapra) during the rut

An observational study of chamois behavior during the rut was conducted at the Los Angeles Zoo. The herd consisted of an adult male, two adult females, two subadult females, and two kids (1.1). During the 13-week study, observers collected scan data on all animals and recorded all occurrences of selected social behaviors during interactions which involved the adult male. Scan observations showed that open areas of the enclosure close to the public were the least preferred, and areas with good rest places were used most. Overall the herd spent 73% of their time stationary, 13% foraging/feeding, 6% moving, and less than 5% each in object investigation, maintenance, play, and social behavior. The adult male rested and fed less, and stood vigilant and engaged in social behavior more frequently than the others. Nearest neighbor data showed clear patterns of kin association beyond the mother-last kid bond. The adult male interacted most often with the regular keepers, the subordinate female and the oldest subadult female. Interactions with the females consisted mostly of herding and sexual behaviors, while those with keepers were almost exclusively competitive/aggressive. While most findings paralleled those from studies of wild chamois, no study has previously reported long-lasting associations among kin.