Bucephala Islandica Research Articles

Dispersal of juvenile Barrow’s goldeneyes (Bucephala islandica) mirrors that of breeding adults

Barrow’s goldeneyes across western North America have been shown to have a high degree of subpopulation independence using several data types. However, evidence for structured populations based on mitochondrial DNA, band recoveries, and tracking of adults is discordant with evidence from autosomal DNA. We used satellite tracking data from both juveniles and adults marked on natal and breeding grounds, respectively, in British Columbia, Canada to evaluate the hypothesis that male-biased juvenile dispersal maintains genetic panmixia of Pacific Barrow’s goldeneyes otherwise structured by migratory movements and high winter and breeding site fidelity of adults. We found that juvenile males traveled to overwintering sites located within the range of the overwintering sites of juvenile females, adult males, and adult females. Juvenile males migrated at the same time, travelled the same distance when moving between natal and overwintering sites, and had the same winter dispersion as juvenile females. Although juveniles did not travel with attendant females, all juveniles overwintered within the wintering range of adults. We tracked some juveniles into the following spring/summer and even second winter. Prospecting juveniles of both sexes travelled from their wintering grounds to potential breeding sites in the proximity of Riske Creek and within the bounds of the breeding locations used by adults. Juveniles tracked for more than a year also showed relatively high winter site fidelity. Because Barrow’s goldeneyes pair on wintering grounds, our tracking data are not consistent with the hypothesis that male-biased juvenile dispersal explains the genetic structure in the mitochondrial DNA and panmixia in the autosomal DNA of Barrow’s goldeneye. We suggest that uncommon or episodic dispersal of males might be enough to homogenize autosomal DNA but is unlikely to influence demographic population structure relevant to contemporary population management.

Pacific Barrow’s Goldeneye refine migratory phenology in response to overwintering temperatures and annual snowmelt

Abstract Timing of seasonal bird migrations is broadly determined by internal biological clocks, which are synchronized by photoperiod, but individuals often refine their migratory timing decisions in response to external factors. Using 11 years of satellite telemetry data, we show that Pacific Barrow’s Goldeneye (Bucephala islandica) at higher latitudes initiated spring and molt migrations later and fall migration earlier than individuals at lower latitudes. We further show that individuals refined migratory timing in response to interannual variation in environmental conditions. Individual Barrow’s Goldeneye initiated spring migration earlier in years with warmer springs at their overwintering locations and concluded spring migration earlier in years with earlier annual snowmelt on their breeding grounds. Because individuals respond to conditions both where they initiate and where they conclude spring migration, our results suggest that Barrow’s Goldeneye update their migratory decisions en route. For all 3 migrations in their annual cycle, birds delayed initiating migration if they had been captured and tagged prior to that migration. Birds that initiated migration late for their latitude were less likely to include a stopover and completed that migration faster, partially compensating for delayed departures. Our results are consistent with the hypothesis that Barrow’s Goldeneye uses a combination of endogenous cues and environmental cues in migratory decision making. Sensitivity to environmental cues suggests that Barrow’s Goldeneye may have behavioral plasticity that is adaptive when faced with ongoing climate change.

Migratory connectivity and variation in migration phenology within the Pacific population of Barrow's Goldeneye (Bucephala islandica)

Migratory connectivity and variation in migration phenology within the Pacific population of Barrow's Goldeneye (Bucephala islandica)

High site fidelity does not equate to population genetic structure for common goldeneye and Barrow's goldeneye in North America

Delineation of population structure provides valuable information for conservation and management of species, as levels of demographic and genetic connectivity not only affect population dynamics but also have important implications for adaptability and resiliency of populations and species. Here, we measure population genetic structure and connectivity across the ranges of two sister species of sea ducks: Barrow's goldeneye Bucephala islandica and common goldeneye B. clangula. We use two different marker types: 7–8 nuclear microsatellite loci assayed across 229 samples and 3678 double digest restriction‐site associated DNA sequencing (ddRAD‐seq) loci assayed across 61 samples. First, both datasets found no evidence of genetic structure within common or Barrow's goldeneye, including between North American and European samples of common goldeneye. These results are in contrast with previous mitochondrial DNA, band recovery and telemetry data which suggest that goldeneyes are structured across their range. We posit that the discordance between autosomal genetic markers and other data types suggests that males, possibly subadult males, may be maintaining genetic connectivity across each species' respective ranges. Next, although mate choice consequences resulting from inter‐specific brood parasitism was hypothesized to cause some level of gene flow between goldeneye species, we only identified a single F1 hybrid with no further evidence of contemporary or historical gene flow. Despite ddRAD‐seq demographic analyses which recovered an optimum evolutionary model of split‐with‐migration (i.e. secondary contact), estimates of gene flow were <<1 migrant per generation in both directions. Together, we conclude that either strong ecological barriers or assortative mating are likely playing a role in preventing further backcrossing. Finally, demographic analyses estimated a relatively deep divergence time between Barrow's goldeneye and common goldeneye of ~1.6 million years before present and suggests that the genomes of both species have been under similar evolutionary constraints.

Reliability of External Characteristics to Age Barrow's Goldeneye

ABSTRACTAccurate assignment of age class is critical for understanding most demographic processes. For waterfowl, most techniques for determining age class require birds in hand, reducing utility for quickly and efficiently sampling a large portion of the population. As an alternative, we sought to establish an observation‐based methodology, achievable in the field with standard optics, for determining age class of Barrow's goldeneyes (Bucephala islandica). We photographed heads, wings, and bellies of 232 Barrow's goldeneyes captured during late winter (February–April) of 2007–2015 along the north Pacific Coast. From these photographs, we focused on 5 external characteristics for both males and females, with binary states that putatively corresponded to 2 age classes—first‐year birds (<1 yr) and adults (>1 yr). For males, all 5 external traits (belly color, head color, eye color, facial crescent, median secondary coverts color) had binary states that were reliably distinguishable by observers. Moreover, all 5 external traits were highly predictive of age class (≥96% concordance between external vs. bursal‐derived ages), and novice observers, after receiving training, were able to accurately age 96% of first‐year and 99% of adult males. In contrast, patterns were weaker for females; putative external characteristics of female age class (belly color, bill radiance, bill blackness, eye color, median secondary coverts color) had 77–91% concordance with bursal‐derived age, compared with 96–100% for males, and observers misidentified age classes of 15% of females, compared with only 2% of males. Overall, age classes of male Barrow's goldeneyes were accurately and reliably distinguishable during winter based on several external characteristics, whereas those of females were not. Our technique may be used to estimate age composition of male Barrow's goldeneyes during winter, providing a useful metric for monitoring annual changes in adult‐to‐juvenile ratios and other important demographic parameters. © 2020 The Wildlife Society.

Annual Winter Site Fidelity of Barrow's Goldeneyes in the Pacific

ABSTRACTCoastal regions on the Pacific north coast of North America provide important wintering habitat for many species of sea ducks. Although winter range and habitat preferences are well described for most species, fidelity to coastal wintering sites is generally undocumented. Fidelity is an important factor necessary for understanding interactions with coastal developments and activities and corresponding management strategies. We used data from Barrow's goldeneyes (Bucephala islandica), a sea duck that winters predominantly in nearshore habitats along the Pacific north coast, to investigate inter‐annual fidelity to, and intra‐annual fidelity within, coastal wintering sites. Between 2006 and 2015, we marked goldeneyes on breeding, molting, and wintering sites with satellite transmitters. We retained 4,931 locations in coastal habitats from 221 goldeneyes across 4 coastal regions for our analyses. These birds demonstrated high inter‐annual fidelity to coastal wintering sites; 75% of selected wintering sites were within 29 km of sites used the previous winter. Inter‐annual fidelity to wintering sites was similar between sex and age classes but differed by coastal region. Goldeneyes from southcentral Alaska, USA, expressed greater inter‐annual fidelity relative to birds from northern or southern British Columbia, Canada, and southeast Alaska. Goldeneyes also expressed high intra‐annual fidelity within wintering sites, with 75% of individuals averaging within‐season movements of ≤9 km. Intra‐annual fidelity was lesser for female than male goldeneyes but did not differ between hatch‐year and after‐hatch‐year birds. We found regional variation in intra‐annual fidelity, with goldeneyes from southcentral Alaska expressing greater intra‐annual fidelity compared to birds from other regions. High inter‐ and intra‐annual winter site fidelity by Barrow's goldeneyes suggests that, at a population level, habitat use is predictable and can be used to inform risk assessment or to evaluate factors affecting habitat choice. Also, low dispersal among wintering sites suggests that recovery from population perturbations, whether caused by natural or anthropogenic events, will be protracted. © 2019 The Wildlife Society.

Sample size considerations for satellite telemetry and animal distributions

ABSTRACTSatellite telemetry is a powerful tool used to follow animals through their annual life cycle, informing the understanding of behavior and distribution of many species. Because boreal‐ and arctic‐nesting North American sea duck populations are challenging to survey, satellite telemetry is important for describing breeding distributions and identifying breeding population structure. Accurate knowledge of breeding distributions is needed for effective habitat and harvest management, but satellite telemetry is expensive so it is important to consider the effort necessary to accurately map breeding distributions. We construct 3 theoretical breeding distributions using existing telemetry data from 3 species of sea ducks, Barrow's goldeneye (Bucephala islandica), surf scoter (Melanitta perspicillata), and black scoter (M. americana), by fitting kernel densities to approximate breeding locations of individual birds. Then we determined the minimum sample size needed to approximate these theoretical breeding distributions by assessing the overlap between breeding densities simulated by sampling from the distributions and the theoretical breeding densities. Diminishing information gains with additional effort (i.e., <1–5% improvement in prediction) were reached with sample sizes ranging from 80 to 130. Sea duck mortality, transmitter failure, and exclusion of non‐breeding individuals resulted in an effective sample size smaller than the number of birds originally marked. For the cases we considered, obtaining breeding locations for 80–130 individuals would require marking 11–41% more birds than the sample size goal. Thus, although satellite telemetry provides valuable information on sea duck populations, our analysis suggests that accurately estimating the extent and relative use of breeding habitats requires substantial investment. © 2018 The Wildlife Society.

Spatial variation in polycyclic aromatic hydrocarbon exposure in Barrow's goldeneye (Bucephala islandica) in coastal British Columbia

Barrow's goldeneyes are sea ducks that winter throughout coastal British Columbia (BC). Their diet consists primarily of intertidal blue mussels, which can accumulate PAHs; accordingly, goldeneyes may be susceptible to exposure through contaminated prey. In 2014/15, we examined total PAH concentrations in mussels from undeveloped and developed coastal areas of BC. At those same sites, we used EROD to measure hepatic CYP1A induction in goldeneyes. We found higher mussel PAH concentrations at developed coastal sites. Regionally, goldeneyes from southern BC, which has relatively higher coastal development, had higher EROD activity compared to birds from northern BC. Our results suggest goldeneyes wintering in coastal BC were exposed to PAHs through diet, with higher exposure among birds wintering in coastal areas with greater anthropogenic influence. These results suggest the mussel-goldeneye system is suitable as a natural, multi-trophic-level indicator of contemporary hydrocarbon contamination occurrence and exposure useful for establishing oil spill recovery endpoints.

Ecology and Conservation of North American Sea DucksEcology and Conservation of North American Sea Ducksedited by Jean-Pierre L. Savard, Dirk V. Derksen, Dan Esler, and John M. Eadie.Studies in Avian BiologyNumber 46. 2015. Cooper Ornithological Society, and CRC Press, Boca Raton, Florida. xxii + 584 pp., 4 color plates, 98 text figures. $119.96 (hardcover). ISBN 13:978-1-4822-4897-5.

The editors of this volume have accomplished a remarkable assemblage of authors and topics on the sea duck tribe (Mergini) that has not been covered before in a single major treatise. While waterfowl (Anseriformes) are, arguably, the family of wild birds that have been most thoroughly studied by scientists, the sea ducks have been relatively poorly covered because of the remote habitats in which most of them are found at all times of the year. Only a few, such as the Common Goldeneye (Bucephala clangula), Barrow’s Goldeneye (B. islandica), Bufflehead (B. albeola), and Hooded Merganser (Lophodytes cucullatus) are accessible fairly easily to researchers. The other 11 extant species nest primarily in boreal, Arctic, or sub-Arctic habitats, and typically winter in even more remote oceanic locations. Nevertheless, waterfowl are one of the best inventoried of all North American birds, and sea ducks have been the subject of several additional surveys designed to monitor specific populations (Chapter 1). Most sea duck populations are uncommon, and many have been declining in number to the point that North American populations of two of the eiders, Spectacled (Somateria fischeri) and Steller’s (Polysticta stelleri), are listed under the U.S. Endangered Species Act. In Canada, eastern populations of Harlequin duck (Histrionicus histrionicus) and Barrow’s goldeneye (Bucephala islandica) are Species of Concern. The most significant upshot of this growing concern has been the formation of the Sea Duck Joint Venture of the North American Waterfowl Management Plan in 1998 (Sea Duck Joint Venture Management Board 2008, Sea Duck Joint Venture 2013). This has provided a superb forum for the sea duck specialists of the world to meet, plan, coordinate, and implement new science and to take other steps to stimulate progress in sea duck conservation. The 27 authors of this volume represent essentially all the individuals and government agencies and academic institutions that have driven the tremendous progress made since 1998. The fifteen chapters cover every major topic that one would expect. This is a departure from the more typical approach to taxonomic groups which usually cover each topic on a species-by-species basis. This was a thoughtful tactic as it encourages the broader community of scientists to integrate sea duck information into their analyses while, at the same time, provides important new perspectives for those more narrowly focused on waterfowl. Some new information is provided and the literature reviewed is thorough with all the common sources cited. In addition, a great deal of less common material is integrated by specialists in the general topics. These qualities contribute importantly to the editors’ central objective ‘‘to highlight

Comparative population structure of cavity-nesting sea ducks

A growing collection of mtDNA genetic information from waterfowl species across North America suggests that larger-bodied cavity-nesting species exhibit greater levels of population differentiation than smaller-bodied congeners. Although little is known about nest-cavity availability for these species, one hypothesis to explain differences in population structure is reduced dispersal tendency of larger-bodied cavity-nesting species due to limited abundance of large cavities. To investigate this hypothesis, we examined population structure of three cavity-nesting waterfowl species distributed across much of North America: Barrow's Goldeneye (Bucephala islandica), Common Goldeneye (B. clangula), and Bufflehead (B. albeola). We compared patterns of population structure using both variation in mtDNA control-region sequences and band-recovery data for the same species and geographic regions. Results were highly congruent between data types, showing structured population patterns for Barrow's and Common Goldeneye but not for Bufflehead. Consistent with our prediction, the smallest cavity-nesting species, the Bufflehead, exhibited the lowest level of population differentiation due to increased dispersal and gene flow. Results provide evidence for discrete Old and New World populations of Common Goldeneye and for differentiation of regional groups of both goldeneye species in Alaska, the Pacific Northwest, and the eastern coast of North America. Results presented here will aid management objectives that require an understanding of population delineation and migratory connectivity between breeding and wintering areas. Comparative studies such as this one highlight factors that may drive patterns of genetic diversity and population trends.

Duration and Phenology of Remigial Molt of Barrow's Goldeneye

Abstract. We quantified the duration and phenology of remigial molt of Barrow's Goldeneyes (Bucephala islandica) in northwestern Alberta, Canada. We estimated that the remiges' average (± SE) growth rate was 3.94 ± 0.13 mm day-1, slightly slower than that of most waterfowl. Barrow's Goldeneyes regained flight with the ninth primary 77% grown, a percentage similar to or greater than that of most waterfowl. By several metrics, remigial molt of Barrow's Goldeneye was longer than that of most waterfowl. We estimated that it took 6.5 ± 1.2 days for a new ninth primary to become visible once the old primary was dropped (pre-emergence interval). The periods in which males and females were flightless were 30 ± 0.4 and 28 ± 0.5 days, respectively, and 36.5 ± 0.5 and 34.5 ± 0.8 days, respectively, including the pre-emergence interval. Complete maturation of primaries after emergence took 39 ± 0.5 and 36 ± 0.7 days for males and females, respectively, and 45.5 ± 0.6 and 42.5 ± 0.9 days, respectively, including the p...

The Body Size-Dependent Diet Composition of North American Sea Ducks in Winter

Daily food requirements scale with body mass and activity in animals. While small species of birds have higher mass-specific field metabolic rates than larger species, larger species have higher absolute energy costs. Under energy balance, we thus expect the small species to have a higher energy value diet. Also the weight and time constraints for flighted and diurnal foragers should set a maximum to the amount of prey items taken in one meal and to the daily number of meals, respectively. Further, avoidance of competition causes the species to reduce the amount of shared prey in their diet. Some diet segregation is therefore to be expected between species. We tested these hypotheses and investigated the role of body mass in the diet composition of 12 sea duck species (Somateria mollissima, Somateria spectabilis, Somateria fischeri, Polysticta stelleri, Bucephala clangula, Bucephala islandica, Bucephala albeola, Melanitta nigra, Melanitta perspicillata, Melanitta deglandi, Histrionicus histrionicus and Clangula hyemalis) wintering in North America. This study was based on a literature survey with special emphasis given to the diet data from the former US Bureau of Biological Survey. The data supported our hypothesis that the energy value of winter diet of sea ducks scales negatively with body mass. Diet diversity also scaled negatively with body mass. Our results suggest the existence of a minimum for the energy value of avian diets.

Variation in body mass and foraging effort of Barrow’s Goldeneyes (Bucephala islandica) during remigial molt

ABSTRACT. Molt is a metabolically demanding process in the annual cycle of birds, particularly for species that undergo simultaneous remigial molt because nutritional and energetic costs occur during a short period. Birds that molt remiges simultaneously utilize many different body-mass and foraging strategies to meet the nutritional and energetic costs of remigial molt, and documentation of interspecific variation has contributed to understanding species-specific risks associated with molt. However, little is known about intraspecific variation in body-mass and foraging strategies among birds that molt remiges simultaneously. We documented body-mass dynamics and foraging effort of Barrow's Goldeneyes (Bucephala islandica) during simultaneous remigial molt at two important postbreeding sites, including a large, hypereuthrophic lake and a small, mesotrophic lake in Alberta, to determine whether strategies for meeting nutritional costs of remigial molt varied across sites, years, and cohorts. Average body m...

Relationships among Breeding, Molting and Wintering Areas of Adult Female Barrow's Goldeneyes (Bucephala islandica) in Eastern North America

While the breeding and wintering ranges of the eastern population of Barrow's Goldeneyes (Bucephala islandica) are generally described, molting locations and links among breeding, molting, and wintering areas are unclear, particularly for adult females. Incubating females from the same breeding location (n = 5) were equipped with satellite transmitters in June 2009. Four molting sites were identified over 2 years, spread broadly across Québec: an inlet in Ungava Bay 1,100 km from the breeding area, a lake 100 km south of Ungava Bay (880 km from breeding area), a lake near Hudson Bay (910 km from breeding area) and the mouth of the Rivière aux Outardes River in the St. Lawrence Estuary (165 km from breeding area). The distance between molting females averaged 755 km and two females molted in regions where males were known to molt. Of four birds with consecutive years of molt locations, three showed inter-annual fidelity to within 5 km of the previous molt sites and the fourth molted in sites that were 968 km apart. Females wintered in different locations within the St. Lawrence Estuary and moved widely throughout the area during winter. The south coast of the St. Lawrence Estuary was used during spring and fall staging, and the north coast during winter. There was not strong migratory connectivity among annual cycle stages in eastern adult female Barrow's Goldeneyes, indicating that they should be considered a single management unit that occurs over a broad range throughout the year.

Survival of Barrow's goldeneyes during remigial molt and fall staging

AbstractPostbreeding survival of waterfowl is rarely quantified, despite potential for constraints during this stage of the annual cycle that may subsequently affect population dynamics. We estimated survival of radio‐marked adult male Barrow's goldeneyes (Bucephala islandica) during remigial molt and fall staging at Cardinal and Leddy Lakes in the Boreal Transition Zone of northwestern Alberta, Canada. Daily survival rate (DSR) was high during remigial molt (DSR = 0.9987, 95% CI: 0.9967–1.0000), corresponding to a 39‐day period survival rate (PSR) of 0.95 (95% CI: 0.88–1.00). During fall staging, DSR was markedly lower (DSR = 0.9938, 95% CI: 0.9898–0.9978), corresponding to a PSR of 0.68 (95% CI: 0.53–0.87) over the 62‐day period between the end of remigial molt and fall migration. Half of fall staging mortalities observed on Cardinal Lake were directly attributed to hunting. We conclude that remigial molt is a period with high survival in the annual cycle of Barrow's goldeneyes at our study sites. However, in light of low fall staging survival, Barrow's goldeneye harvest management strategies should be carefully evaluated with intent to reduce risk of localized high mortality at significant staging sites in western Canada. © 2013 The Wildlife Society.

Facultative Sex Allocation and Sex‐Specific Offspring Survival in Barrow's Goldeneyes

AbstractSex allocation theory predicts that females should bias their reproductive investment towards the sex generating the greatest fitness returns. The fitness of male offspring is often more dependent upon maternal investment, and therefore, high‐quality mothers should invest in sons. However, the local resource competition hypothesis postulates that when offspring quality is determined by maternal quality or when nest site and maternal quality are related, high‐quality females should invest in the philopatric sex. Waterfowl – showing male‐biased size dimorphism but female‐biased philopatry – are ideal for differentiating between these alternatives. We utilized molecular sexing methods and high‐resolution maternity tests to study the occurrence and fitness consequences of facultative sex allocation in Barrow's goldeneyes (Bucephala islandica). We determined how female structural size, body condition, nest‐site safety and timing of reproduction affected sex allocation and offspring survival. We found that the overall sex ratio was unbiased, but in line with the local resource competition hypothesis, larger females produced female‐biased broods and their broods survived better than those of smaller females. This bias occurred despite male offspring being larger and tending to have lower post‐hatching survival. The species shows strong female breeding territoriality, so the benefit of inheriting maternal quality by philopatric daughters may exceed the potential mating benefit for sons of high‐quality females.

Metals, Trace Elements, Polychlorinated Biphenyls, Organochlorine Pesticides, and Brominated Flame Retardants in Tissues of Barrow’s Goldeneyes (Bucephala islandica) Wintering in the St. Lawrence Marine Ecosystem, Eastern Canada

The eastern North American population of Barrow's goldeneyes winters in the St. Lawrence Estuary and Gulf of St. Lawrence where the sediments and food web are known to be contaminated with inorganic and organic compounds. Therefore, there is a potential for contamination of this population, which is designated of Special Concern by the Committee on the Status of Endangered Wildlife in Canada. Specimens were collected during three consecutive winters (2005-2007) in three regions (Manicouagan, Charlevoix, and Chaleur Bay) and analysed for metals, trace elements, polychlorinated biphenyls (PCBs), organochlorine pesticides, and brominated flame retardants (BFRs). Liver mercury levels were greater in the St. Lawrence Estuary (4.4 mg/kg in Manicouagan, 3.8 mg/kg in Charlevoix) than in Chaleur (2.4 mg/kg), whereas selenium showed the opposite pattern (7.3 mg/kg in Manicouagan, 7.0 mg/kg in Charlevoix, and 36.9 mg/kg in Chaleur). Liver PCB levels were greater in specimens from Manicouagan (236 ng/g) than in those from the two other regions (72 ng/g in Charlevoix, 35 ng/g in Chaleur). DDT was greater in Chaleur (66 ng/g) versus 10 ng/g in Manicouagan and 16 ng/g in Charlevoix. BFRs were not compared among regions because of smaller sample sizes, but mean total concentration was low (4.02 ng/g). Overall, although significant differences were found across regions, levels of all contaminants measured are generally low and not of toxicological concern for this population.

Differential responses to related hosts by nesting and non‐nesting parasites in a brood‐parasitic duck

Host-parasite relatedness may facilitate the evolution of conspecific brood parasitism, but empirical support for this contention remains inconclusive. One reason for this disparity may relate to the diversity of parasitic tactics, a key distinguishing feature being whether the parasite has a nest of her own. Previous work suggests that parasites without nests of their own may be of inferior phenotypic quality, but because of difficulties in identifying these parasitic individuals, little is known about their host selection criteria. We used high-resolution molecular maternity tests to assign parasitic offspring to known parasites with and without their own nests in a population of Barrow's goldeneyes (Bucephala islandica). We determined whether parasite nesting status, host-parasite relatedness and distance between host and parasite nests affected the probability of parasitizing a host and the number of eggs laid per host. We also investigated whether nesting parasites, conventionally nesting females and non-nesting parasites differed regarding their age, structural size, body condition, nesting phenology or total brood size. The probability of engaging in parasitism increased with host-parasite relatedness and spatial proximity to host nests for nesting and non-nesting females alike. However, nesting parasites increased the number of eggs donated with relatedness to the host, while non-nesting parasites did not do so. Non-nesting parasites laid fewer eggs in total, but did not differ by any of the other quality measures from conventional nesters or nesting parasites. Our study provides the first demonstration that nesting and non-nesting parasites from the same population may use different host selection criteria.

Discovery of Important Postbreeding Sites for Barrow's Goldeneye in the Boreal Transition Zone of Alberta

Sites where Barrow's Goldeneye (Bucephala islandica) undergo remigial molt and fall staging are poorly known, with only two major sites documented in Alaska and the Yukon Territory. Satellite telemetry, aerial surveys and ground surveys were used to identify previously unknown molting and fall staging areas in the Boreal Transition Zone (BTZ) of northern Alberta. Of 816 wetlands surveyed between 2004 and 2006 in the BTZ, 40–45% (105–127 lakes annually) had molting goldeneyes. Of these, 1.3–3.3% were used by large aggregations of goldeneyes (>100 birds). Two wetlands, Cardinal and Leddy Lakes, were particularly important, with an estimated 5,000–7,000 Barrow's Goldeneyes, primarily adult males, using these sites during remigial molt and fall staging. Birds used these sites up to five months or over one-third of their annual cycle. Half of adult males marked with satellite transmitters at a breeding area in interior British Columbia used Cardinal Lake for postbreeding activities. Discovery of these sites represents some of the largest concentrations of molting Barrow's Goldeneyes in North America, and the only major molting sites currently known for the intermountain breeding portion of the western population. Protection of Cardinal and Leddy Lakes, and other significant molting and staging sites within the BTZ, should be a priority conservation effort for this species.

Characteristics of nest cavities of Barrow's Goldeneyes in eastern Canada

ABSTRACT Barrow's Goldeneyes (Bucephala islandica) are secondary cavity nesters found in western North America and, to a lesser extent, in eastern North America. The eastern North American population is concentrated in the province of Québec and totals about 2000 pairs. Characteristics of nest cavities used by Barrow's Goldeneyes have been described in western North America, but no nest cavities have been found in eastern North America. From 2004 to 2008, we searched for nest cavities in the species’ core breeding area in the boreal forests north of the St. Lawrence River. We captured 12 adult females on their breeding grounds and fitted them with transmitters, but none apparently nested so we conducted ground searches in areas near lakes where paired birds were observed. We found 11 cavities, with 10 in dead, decaying trees and one in the dead part of a dying tree. Nine cavities were in white birch (Betula papyrifera) trees. Mean cavity height was 3.5 ± 1.6 (SD) m (range = 1.2–6.6 m) and mean diameter at breast height (DBH) of cavity trees was 37.8 ± 4.7 cm (range = 32.2–47.5 cm). In contrast to the population in western North America, Barrow's Goldeneyes in eastern North America appear to rely on the availability of natural cavities formed in large, decaying trees for nesting. Current forestry regulations in Québec do not promote the retention of either large trees or older forests, reducing the availability of potential nest cavities for Barrow's Goldeneyes and likely threatening their long-term conservation. Therefore, we recommend that guidelines be developed to promote silvicultural practices aimed at preserving the long-term availability of large (DBH ≥ 30 cm) decaying trees across the breeding range of Barrow's Goldeneyes. El Pato de Barrow's (Bucephala islandica) se encuentra en la parte oeste de Norte América, y en menor grado, en la parte este del continente. Este anida en cavidades secundarias. La población del este de Norte América, está concentrada en la provincia de Quebec y se estima en unas 2000 parejas. Las característica de las cavidades utilizadas para anidar por este pato en la parte oeste de Norte América han sido descritas, pero las de la parte este del continente americano, no han sido encontradas y descritas. De 2004–2008, buscamos cavidades utilizadas por esta especie, en el bosque boreal al norte del Rio St. Lawrence. Capturamos 12 hembras adultas y les colocamos radiotransmisores pero estas aparentemente no se reprodujeron. Por tal razón buscamos en los alrededores de áreas cerca del lago en donde observamos parejas. Encontramos 11 cavidades, 10 en árboles muertos, y que se estaban descomponiendo, y uno en una parte muerta de un árbol que se estaba muriendo. Nueve cavidades fueron encontradas en Betula papyrifera. La altura promedio de las cavidades resultó ser de 3.5 ± 1.6 (SD) m (alcance = 1.2–6.6 m), y el DBH fue de 37.8 ± 4.7 cm (alcance = 32.2–47.5 cm). En contraste a la población del oeste de Norte América, la del este parece depender, para anidar, de la disponibilidad de cavidades naturales que se forman en árboles viejos que se están descomponiendo. Las regulaciones de silvicultura en Quebec no promueven la retención ya sea de árboles grandes o bosques viejos, reduciendo la disponibilidad potencial de cavidades para el anidamiento del pato, y de esta manera amenazando su conservación a largo alcance. Por lo tanto recomendamos que se desarrollen guías de silvicultura dirigidas a preservar árboles grandes (DBH > 30 cm) que se estén descomponiendo a lo largo del área utilizada para la reproducción por parte del Pato de Barrow's.