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Cape Jourimain Nature Centre, Bayfield, NB (CWS) 2001 INVESTIGATION
OF PREBASIC MOULT IN HERRING GULLS (Larus argentatus)
AND GREAT BLACK-BACKED GULLS (Larus marinus): AN
ACWERN INITIATIVE Moult, reproduction and accumulation of winter or migratory fat reserves tend to be temporally segregated for birds, and high energetic costs may lead to temporal separation of these processes for some species. Gulls typically undergo one prealternate partial moult of head and body feathers prior to breeding, followed by one prebasic complete moult, per year. Prebasic moult initiation varies in relation to date and breeding phenology both within and between populations for European Herring Gulls and Great Black-backed Gulls. Although studies of moult for North American gulls are limited, evidence suggests Herring Gulls breeding in the Canadian Arctic may initiate prebasic moult earlier during incubation than their southern conspecifics. We suggest timing of initiation and rate of moult, are adaptive and vary in relation to sex, age and ecological factors related to latitude. We intend to test these hypotheses by examining timing and rate of moult, in relation to breeding phenology, for populations of herring gull and great black-backed gull in the Great Lakes, Gulf of Maine, Bay of Fundy, Newfoundland, Labrador and Hudson Bay regions. COMPARATIVE FEEDING ECOLOGY OF
HERRING AND GREAT BLACK-BACKED GULLS IN THE BAY OF FUNDY Numbers of the two species of large gull that breed commonly along the Bay of Fundy coast of New Brunswick - Herring Gull (Larus argentatus) and Great Black- backed Gull (L. marinus) - have both increased greatly since World War II, due mainly to greatly increased amounts and availability of garbage which these species have exploited. Various forms of human garbage are used by gulls to supplement natural food sources in their diet. Recently in New Brunswick, methods of waste management have been changing and the volume of waste exposed and available to gulls has been reduced. However there is still no local quantitative information on the extent to which gulls rely on the human-generated food sources. I am currently investigating which food sources gulls in the Bay of Fundy are using, how much of their diet consists of human-generated food, and how far they will fly from their breeding colony to obtain it. Preliminary success with a method using colour- and shape-coded craft foam pieces to assess the distance gulls will travel to these food sources from breeding colonies has led to speculation as to whether this method could be made more quantifiable. The difficulties in accomplishing this will be discussed. My research focus is on coastal islands with breeding colonies in the Bay of Fundy, from Saint John, New Brunswick to the Deer Island, Campobello, and Wolves Archipelagoes. The extent to which gulls feed on human created food sources is of interest because it may affect not only their population trends, but also those of other species of conservation interest. If non-natural food sources are removed through improved waste management methods, and gull reliance on those food sources proves to be significant, gulls may shift to depredating other bird species such as eiders or terns. FLOATERS OR NOT? INVESTIGATING THE
USE OF REPRODUCTIVE INDICES AND MOBBING CENSUS Our respective research on the habitat selection of forest birds include censusing study species using chickadee mobbing and/or barred owl playbacks. Points were visited multiple times throughout the breeding season, and at each point, species were assigned a productivity rank from zero to four (0=not present, 1=floater, 2=hold a territory, 3=evidence of a pair or nest, 4=fledgling or family group). Floaters are unpaired individuals that do not defend a territory. We originally defined individuals as floaters if they were seen or heard only once during multiple visits, assuming they were just moving through and did not hold a territory. We have made preliminary steps to investigate whether this definition is valid, and how alternate definitions may affect our habitat selection models.
SELECTION AND USE OF COMMON EIDER
BROOD-REARING HABITAT ON GRAND MANAN ISLAND, NEW BRUNSWICK The survival rate of eider ducklings in the Bay of Fundy has decreased from >14% of the adult breeding population prior to 1991 to 4-8% between 1995 and 1998. Broods may travel several kilometers from nesting islands to coastal duckling rearing areas within 24 hrs post-hatch. Eider ducklings and attending females feed on invertebrates commonly associated with rockweed. Commercial boating (rockweed harvesting, fishing activity), recreational boating, industrial development (aquaculture cages) and public use of coasts could increase risk of duckling predation by great black-backed gulls and bald eagles. We quantified the relative influence of various factors on habitat selection and use of eider broods. We examined food availability, extent of predation and human disturbance, proximity to nesting islands and degree of exposure to wind and waves. We looked at spatial and temporal patterns of distribution and abundance of eider broods. Rockweed harvested and unharvested sites were visited from the period of 29 May to 3 August, 2001. The following data was recorded at 20 minute intervals for a period of 15 hours daily: number and behaviour of ducklings and females, age-class of ducklings, number, species and age of predators, predation attempts or successes, type of human disturbance and reaction of broods following a disturbance event.
ESTIMATING AGE-SPECIFIC SURVIVAL AND
DISTRIBUTION OF EMIGRANTS BETWEEN COLONIES OF ATLANTIC PUFFIN (Fratercula
arctica) IN THE GULF OF MAINE The regional breeding population of Atlantic puffin in the Gulf of Maine is spatially distributed between 7 colonies. We focus on the 5 western most colonies, which include 98% of the regional population in 2001. Data for our analyses come from a long-term banding and resighting project started in 1973. However, initiation of data collection varies temporally between colonies. Due to this temporal variation, 1982-2001 is the longest running data set we consider. Most of our analyses require known age birds. From 1980-2001, all colonies provide 3,942 local birds (i.e. chicks) banded and 13,977 subsequent resightings. As part of our banding protocol, birds receive individually engraved colour-bands, which are easily read from a distance. Our main objective is to document and quantify emigrant distribution between colonies and age-specific survival for a seabird metapopulation. We use Maximum Likelihood Estimates (MLE) as estimates of survival and movement. MLEs will be determined through reduction of two initial model designs: (1) the open population model Cormack-Jolly-Seber and (2) a multi-strata model used specifically to estimate emigration probabilities. Model parsimony is determined using a Goodness-of-fit test through program RELEASE and evaluation of AIC (Akaikes Information Criterion) values. AIC values and hypothesis testing using Likelihood Ratio Tests provide a means to compare models and investigate several a priori hypotheses. These hypotheses consider geographic and temporal variation in survival and movement probabilities.
EFFECTS OF DRINKING WATER SALINITY
CONCENTRATIONS ON GROWTH AND SURVIVAL OF COMMON EIDER DUCKLINGS (SOMATERIA
MOLLISSIMA) IN EAST BAY, NUNAVUT In July of 2001, I tested the growth and survival of common eider ducklings in relation to salt concentrations of available water. To do so, I collected Fifty ducklings from nests on Mitivik Island in East bay, Nunavut, and partitioned them into five groups of ten. I then exposed each group to a different water regime for a period of six days. The regimens I used were: 1) salt water only; 2) fresh water only; 3) 1/3 salt water + 2/3 fresh water; 4) 2/3 salt water + 1/3 fresh water; 5) fresh water for 12 hours followed by salt water for the remaining duration of the experiment. I evaluated ducklings through measuring their weight and culmen twice daily, and also measuring the relative activity of the ducklings every six hours. All ducklings of the regimes four and five died. Five ducklings on regime three died, and one duckling from each of the regimes one and two, died. From the third day of the experiment on, average weights of groups one and two were significantly higher than the other three, and the group three had a significantly higher average weight than groups four and five. This study suggests that freshwater resources in the first few days post-hatch may not only be crucial to the growth and physical fitness of common eider ducklings, but may ultimately directly affect their survival. Further studies may show that sources of fresh water are key components of quality brood rearing habitat for common eider ducklings, which may play an important role in management of the species.
EFFECTS OF TRAPPING ARCTIC TERNS AT
THE NEST Disturbance of nesting birds can come in many forms. When trapping and handling birds we try to minimize the impacts that we may have on the birds, however, the potential impacts are often not measured. In the past, the effects of trapping Common and Roseate terns have been examined, but one cannot assume that all terns respond in similar ways. For the past 3 years we have been trapping Arctic Terns on Machias Seal Island as part of a study of population dynamics. We have tried to measure the impact of trapping by estimating the productivity of birds that have been trapped and those that have not. Additionally we have measured how long it takes to trap a predetermined number of birds each year. We also have kept track of where each bird was trapped each year and where it has been seen in subsequent years. Arctic Terns appear to be more wary of traps than other species of terns and often take longer to catch. However, there appears to be no difference between the productivity of terns that have been trapped compared to those that have not been trapped.
PREDATION BY DIVING DUCKS AT MUSSEL
CULTURE SITES IN P.E.I. : QUANTIFICATION OF EFFECTS AND DEVELOPMENT OF
MITIGATIVE TECHNIQUES Blue Mussel cultivation in PEI is a 35 to 40 million dollar industry and generates approximately 80% of cultivated mussels in Canada. Sea Duck (mostly Greater Scaup & Long-tailed Duck) predation and related shake off costs the industry $1 to 2 million annually. Using a series of manipulative experiments and behavioural observations, combined with stage-based matrix modeling of results, we will attempt to describe and quantify the impact that ducks have on cultivated mussels, and the effects of the industry on ducks feeding in the area. We will also work to develop non-disruptive methods that will mitigate effects of ducks on cultivated mussel farms. To determine the interactions between mussels and ducks, we will establish two experimental culture sites in bays where growers experience duck predation. We will grow mussels using a variety of seeding sizes, seeding densities, socking materials, and with and without cages around the socks to exclude ducks. Mussel growth and survival will be monitored regularly. Feeding behaviour of ducks and preferred prey sizes will be quantified using focal animal and scan sampling, underwater filming, duck gullet content analysis and monitoring of marked mussels. Questions of interest include whether or not these ducks feed at night, what are the losses of cultivated mussels due to shake off compared with actual consumption by ducks, and the response of mussels to the different rearing conditions. Results will provide mussel farmers with strategies for dealing with the duck problem that will maximize mussel yield and increase the likelihood that ducks and mussel farms can peacefully coexist in PEI.
ACWERN-Acadia: HOW ARE WE DOING? We re-visit some of the original objectives of ACWERN and ask the question: How are we doing? In particular, we will explore the broad question of why ecological management so often fails or falls short, and the role that we as scientists have in these failures. To do this we will touch first on the theoretical elements that underpin ACWERN's research program at Acadia and discuss in detail the success and failure of studies that have been undertaken to further develop this theory. After a short breakout group addressing the same questions more widely, we will outline the methodological approaches we are using that have proven to be most useful in tackling ecological questions at scales relevant to management. We will conclude with a general presentation of critical future research directions, and a discussion of how we can improve on our track record.
EFFECTS OF AIRCRAFT DISTURBANCE ON
HARLEQUIN DUCKS BREEDING IN CENTRAL LABRADOR We developed behavioural repertoires and quantified time-activity budgets of Harlequin Ducks breeding on Fig River in the Military Training Area of central Labrador. Paired female Harlequins spent significantly more time feeding than their mates who budgeted significantly more time to vigilance. Standardized 30-minute watches that occurred during aircraft over-flights (disturbed) could be discriminated from "undisturbed" watches, and there was a positive relationship between the resulting canonical variables and noise levels registered by sound level meters. The dose-response curves support that behavioural responses increase in magnitude with increasing noise levels and are nonlinear although our sample sizes are small. Analyses of apparent survival and recruitment rates, and body condition will be presented.
INTERACTIONS BETWEEN SHOREBIRDS AND
INTERTIDAL INVERTEBRATES IN THE UPPER BAY OF FUNDY Semipalmated sandpipers (Calidris pusilla) migrate annually through the upper Bay of Fundy, feeding heavily on the amphipod Corophium volutator in intertidal mudflats. During an experiment conducted in summer 1999 to examine trophic interactions on a mudflat at Avonport, N.S., we found that shorebird predation reduced Corophium abundance by more than 80%, and that fertilizer application significantly enhanced algal abundance. However, effects did not cross trophic levels and our manipulations generated few indirect effects in the community. Transmission of effects through the system was probably blocked by the compensatory activities of mud whelks (Ilyanassa obsoleta), which responded rapidly to both fertilizer application and bird predation. We also found that Corophium abundance in the experimental sites correlated with whelk abundance, raising the possibility that it may be able to predict Corophium density, and perhaps even bird abundance in a given area, simply by counting whelks. We tested this possibility at four mudflats during summer 2000. Using monthly surveys of Corophium and whelk abundance, chlorophyll a concentration, and bird footprints (as an index of their presence), we determined that the relationship between Corophium and whelks observed at Avonport in 1999 was consistent across several mudflats in the Bay of Fundy. Furthermore, we found that it was possible to predict bird abundance based on abundance of adult (but not juvenile) Corophium, and on whelk densities several weeks before birds arrive. These findings highlight a previously unrecognized role of mud whelks in this system, and further our understanding of the movements and activities of migratory shorebirds relative to mudflat-dwelling species in the upper Bay of Fundy.
EVIDENCE THAT OCEANOGRAPHIC
"OSCILLATION" RULES SEABIRD SPECIES' MOST CRUCIAL DEMOGRAPHIC
PARAMETER, ANNUAL ADULT SURVIVAL It has been suggested that seabird populations are buffered from normal variation in oceanographic conditions because survival rates are low only when their prey is extremely scarce, rise quickly with slightly improved feeding conditions, and are constant in moderate to good feeding conditions. To test this idea, we evaluated whether annual adult survival of Least Auklets (Aethia pusilla), a small planktivorous seabird, covaried with large scale oceanographic conditions in the North Pacific ocean during 1990-2000. Survival estimates and relationships between survival and three large scale indices of climatic conditions that correlate with oceanography: the Pacific Decadal Oscillation Index, Aleutian Low Pressure Index, and North Pacific Index (NPI) were evaluated using program MARK. For Least Auklet survival, the best fitting model was a two-age model incorporating the covariate NPI (average value for the period auklets were at sea, August-April), F(age1, age2*NPI), p(g). Least Auklet annual survival covaried with continuous variation in large-scale climatic conditions. Notwithstanding conservation measures taken to control introduced predators, oil spills, human disturbance and other anthropogenic sources of mortality, our results suggest that the status of seabird populations may ultimately be determined by oceanographic conditions that relate to climate change. Long-term demographic studies of Atlantic Puffins (Fratercula arctica) are underway in Atlantic Canada to examine the effect of 'Atlantic Oscillation'.
HABITAT SELECTION BY BREEDING
GRASSLAND BIRDS AFTER HAY HARVEST IN A MANAGED AGRO-ECOSYSTEM IN NOVA
SCOTIA Primary nesting habitats for Bobolinks, in eastern Canada, are active hayfields and grasslands that have remained idle for several years. For birds nesting in active hayfields, nest destruction from hay harvest is a major limiting factor for successful reproduction. Adults that have lost nests to hay harvest, and do not renest, are forced to occupy alternate habitats prior to migration. To determine whether displaced grassland birds, such as Bobolinks, select adjacent unharvested habitats that most resemble original nesting habitat, I assessed Bobolink breeding and subsequent post hay-harvest habitat selection in a managed Nova Scotia agro-ecosystem. I employed line-transect census methods through active hayfields and adjacent ericaceous uplands (consisting of woody vegetation and immature trees). In the first year, all active hayfields were harvested, after which Bobolink adults and fledglings emigrated to the ericaceous uplands and remained in large flocks until mid-August. In the subsequent year, only ~60% of active hayfields were harvested. Hence, Bobolinks that were displaced from hay harvest could select between ericaceous uplands and hayfields with no resident breeding birds. Using multiple univariate ANOVA to determine habitat selection after harvest, displaced birds did not utilize the available hayfields, but a significant proportion of them emigrated to the ericaceous upland (F = 48.81, p = <0.0001). These results suggest that management for this species in the region needs to supply diverse habitats to fulfill the requirements of displaced and fledged Bobolinks and yet maintain an adequate contiguous nesting habitat. I will also discuss how this study will serve as a pilot project to a larger long-term investigation of the demographic and behavioral responses of grassland birds to agro-ecosystem management in Atlantic Canada.
TIMING AND PATTERNS OF GROWTH OF
BILATERAL TAIL STREAMER ORNAMENTS OF THE RED-TAILED TROPICBIRD We investigated timing and patterns of growth of the bilateral tail streamer of the Red-tailed Tropicbird Phaethon rubricada, a monogamous seabird, based on 639 individuals, including 406 of known age and 452 of known sex, measured in the year 2000 and 2001 at Tern Island, French Frigate Shoals in the Northwestern Hawaiian Islands. One prominent ornament was displayed: an elongated red tail streamer, composed of two filamentous central rectrices with a black rachis and narrow red vane averaging 397.9 ± 1.77 SE mm in length (range = 190-524 mm) with 42 missing cases (broken tail streamers). The central rectrices are constantly being replaced, over 60% of individuals measured had one full grown rectrix and the other growing (moulting) indicating that the two tail streamers grow alternately. Based on 1051 tail streamer measurements, including recaptures within and between years, taken throughout the breeding season, 42% of the cases of had 2 full grown tail streamers in February in comparison to 12% in April during peak egg laying. By the end of the season, during chick rearing, less than 1% of the cases had 2 full grown tail streamers. These results suggest that it is important for individuals to have both tail streamers as long as possible at the beginning of the breeding season for aerial displays and mate attraction. Male and female Red-tailed Tropicbirds are morphologically indistinguishable externally so we used a genetic sexing technique and a combination of cloacal appearance near laying to identify males and females. There was evidence for slight sexual dimorphism for the tail streamer (males were slightly larger than females). Based on adults of known age, three to twenty-two years, the length of individualsí tail streamers does not appear to increase with age.
FORAGING ECOLOGY AND OFFSPRING
GROWTH RATES OF GREAT BLACK-BACKED GULLS AT GULL ISLAND, NEWFOUNDLAND
AND THE GANNET ISLANDS, LABRADOR Competition can be based on temporal and/or spatial food source limitations to individuals. Great Black-backed Gulls (Larus marinus) are generalist predators, feeding on intertidal invertebrates; smaller birds and mammals; the food of, and the young of other breeding seabirds and waterfowl; carrion; and human refuse. Both Gull Island and the Gannet Clusters are rich in prey items but Gull Island has nearby sources of human refuse. In addition to nearby dumps Gull Island has a substantial population of breeding Herring Gulls (Larus argentatus). All Great Black-backed Gulls fed their chicks seabirds (mostly auk eggs) in the Gannet Islands, while on Gull Islands, adults fed chicks seabirds (mostly adult puffins, kittiwakes and petrels), and/or garbage. Among adults that fed their chicks seabirds, chick growth rates were faster on the Gannet Islands than on Gull Island. Further, on Gull Island, Black-Back chicks living amongst Herring Gulls had the highest growth rates and chicks fed seabirds tended to grow faster than chicks fed garbage. We suggest that Black-Backs that nest amongst Herring Gulls take advantage of the aggressive behaviour toward predators displayed by Herring Gulls as an early warning and an extra defence.
EVALUATING BLACKBURNIAN WARBLER (Dendroica
fusca) HABITAT AND RESOURCE USE ON MULTIPLE SCALES Blackburnian Warblers are traditionally considered a mature conifer species but as current forest practices and urbanization change the structure of available habitat for territory placement, it is forced to either decline or adapt. There is a rudimentary understanding of essential microhabitat requirements, foraging ecology and mechanisms driving choices for Blackburnian Warblers. They nest in higher strata of conifers, and forage on small branches of mature coniferous and deciduous trees. However their dependency on conifer trees may change between populations because of variation in the availability of coniferous trees. Territory size and foraging substrate may be a response to conifer growth, distribution and density. The objectives of this study are to (1) compare productivity and density of Blackburnian Warblers in mature hardwood, softwood and mixed-wood stands, (2) compare territory size between stands, (3) compare territory placement to distribution of spruce within a stand, and (4) compare chosen foraging substrate to availability within territories. Data on density and productivity, behavioral ecology and territory placement and size was collected in the Fundy Model Forest and Fundy National Park from May to August 2001. Methods of data collection included territory mapping, behavioral observations, and vegetation surveys. Based on preliminary data, mechanisms that drive choices will be investigated in the following year. |