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At least 505 records · Page 28Linked to original sources
USGS1996

Complete migration cycle of golden eagles breeding in northern Quebec

Radio tracking via satellite was initiated to study the year-round movements of Golden Eagles(Aquila chrysaetosc anadensis) breeding on the east coast of Hudson Bay, Quebec. In June and August 1992, six Golden Eagles(five adults and one juvenile) were marked, three of which completed their year-round movements. The eagles left their breeding area in mid- to late October and migrated to known wintering areas in the eastern United States. They used different routes but each followed the same general path during fall and spring migrations which lasted between 26 and 40 days,and 25 and 51 days, respectively. Eagles wintered from 93 to 135 days in areas located 1,650 to 3,000 km south of their breeding territory. In spring 1993, satellite telemetry located the eagles in their former breeding territory in late March, mid-April and early May. This study confirms previous suggestion that some breeding Golden Eagles wintering in eastern United States come from northern Quebec and describes the first successful tracking of the complete yearly migration cycle of a bird of prey.

The Condor↗
USGS1992

Reproductive ecology of Emperor Geese: Survival of adult females

Life history theory predicts a decrease in survival with increased reproductive effort of individuals. This relationship, however, is highly variable among and within species. I studied the nesting success and survival of adult female Emperor Geese during 1982-1986 and found no direct evidence that differential reproductive effort as measured by the number of eggs laid or hatching success had a significant negative effect on survival to the next breeding season. Incubated clutch size, hatched clutch size, number of parasitic eggs, nest initiation date, hatch date, and mass at hatch were not related to subsequent survival. Of the factors I examined, only an attempt to nest the previous season was related to survival of a female. I suggest that the higher probability of survival among non-nesting adult female Emperor Geese was primarily related to hunting pressure on the nesting area between spring and fall migration. The probability of survival was increased for females with larger clutches, suggesting a positive relationship between brood size and survival.

Alaska↗
USGS1992

Describing Willow Flycatcher habitats: scale perspectives and gender differences

We compared habitat characteristics of nest sites (female-selected sites) and song perch sites (male-selected sites) with those of sites unused by Willow Flycatchers ( Empidonax traillii ) at three different scales of vegetation measurement: (1) microplot (central willow [ Salix spp.] bush and four adjacent bushes); (2) mesoplot (0.07 ha); and, (3) macroplot (flycatcher territory size). Willow Flycatchers exhibited vegetation preferences at all three scales. Nest sites were distinguished by high willow density and low variability in willow patch size and bush height. Song perch sites were characterized by large central shrubs, low central shrub vigor, and high variability in shrub size. Unused sites were characterized by greater distances between willows and willow patches, less willow coverage, and a smaller riparian zone width than either nest or song perch sites. At all scales, nest sites were situated farther from unused sites in multivariate habitat space than were song perch sites, suggesting (1) a correspondence among scales in their ability to describe Willow Flycatcher habitat, and (2) females are more discriminating in habitat selection than males. Microhabitat differences between male-selected (song perch) and female-selected (nest) sites were evident at the two smaller scales; at the finest scale, the segregation in habitat space between male-selected and female-selected sites was greater than that between male-selected and unused sites. Differences between song perch and nest sites were not apparent at the scale of flycatcher territory size, possibly due to inclusion of (1) both nest and song perch sites, (2) defended, but unused habitat, and/or (3) habitat outside of the territory, in larger scale analyses. The differences between nest and song perch sites at the finer scales reflect their different functions (e.g., nest concealment and microclimatic requirements vs. advertising and territorial defense, respectively), and suggest that the exclusive use of either nest or song perch sites in vegetation analyses can result in misleading, or at least incomplete, descriptions of a species' habitat. Habitat interpretations for Willow Flycatchers (and perhaps for many passerines) are a function of the gender-specific behavior of the birds observed and the scale of vegetation measurement.

The Condor↗
USGS1992

The timing of wing molt in tundra swans: energetic and non-energetic constraints

Date of wing molt initiation, based on the regression of tenth primary length on capture date, was calculated for breeding and nonbreeding Tundra Swans (Cygnus columbianus columbianus) on the Colville River Delta, Alaska. Breeding females initiated wing molt significantly later than breeding males and nonbreeding males and females; the molt of breeding females was correlated with the date on which their eggs hatched. Breeding males did not differ significantly from nonbreeding males and females in the date of molt initiation. Timing of molt in breeding males and females was consistent with the views that females delay molt while replenishing energy spent on reproduction, but was also consistent with the breeding pair's need for primaries to defend territories and to defend and brood young. Other results, including an increase in an index of female body condition throughout most of the molt period, and a positive correlation between clutch size and female hatch-to-molt interval, were not predicted by the hypothesis that past energy expenditures constrain the timing of molt. Patterns of wing molt within and among other Northern Hemisphere geese and swans are also difficult to explain on the basis of energetics alone. For example, breeding females initiate molt before breeding males in many species. Also, there is extreme asynchrony between mates in two swan species; one of those species also exhibits variation in which sex initiates wing molt first. Both patterns suggest that asynchrony, per se, is important, probably to facilitate brood protection or territory defense. In Tundra Swans and other northern breeding geese and swans, the non-energetic demands of territory defense, brood defense, and brooding are probably important constraints on the timing of wing molt.

Condor↗
USGS1992

Time allocation by Greater White-fronted Geese: Influence of diet, energy reserves and predation

I determined the amount of time Greater White-fronted Geese ( Anser albifrons frontalis ) allocated to various activities from September to May, 1980-1982 at their primary wintering areas in the Pacific Flyway of North America. The length of time spent on roosts during the day was positively correlated to day length. Geese at roost sites spent the majority of their time sleeping (24-46%), alert (17-40%), walking or swimming (6-24%), and in comfort behaviors (3-25%). The amount of time geese fed each day varied little from early autumn to late spring (4.5-4.9 hr), except during mid-winter when minimum temperatures were below freezing (3.9 hr), and immediately before migration in spring (6.3 hr). The proportion of time devoted to feeding and alert behavior, the two most dominant activities at field sites, varied significantly among seasons and locations. The amount of time geese were actively engaged in foraging each season was more dependent on feeding intensity than the amount of time spent at foraging sites (fields), and varied almost three-fold, from 1.8 hr during late winter to 5.1 hr during late spring. Geese fed in closer proximity to conspecifics, were more frequently disturbed, and spent less time feeding during the hunting season. Exploitation of high energy foods and catabolism of substantial energy reserves probably enabled geese to minimize foraging time during periods of harsh weather and high predation pressure. Seasonal variation in the proportion of time spent feeding corresponded closely to changes in body mass. Greater White-fronted Geese wintering in the Pacific Flyway spent substantially less time feeding than they do in Europe, as geese in California fed primarily on high energy cereal grains, while in Europe they subsist on green vegetation which has relatively less digestible energy than cereal grains.

The Condor↗
USGS1994

The role of nutrient reserves for clutch formation by Northern Pintails in Alaska

We analyzed carcass composition of female Northern Pintails ( Anas acuta ) in Alaska to assess the importance of nutrient reserves for formation of first clutches (n = 85) and renests (n = 39). Habitat (tundra vs. boreal forest), hen age (yearling vs. adult), and year (1990 vs. 1991) did not affect nutrient reserve use. During formation of first clutches, Northern Pintail hens relied on lipid reserves more than any other duck species that has been studied. For much of the nesting season, lipid reserves were used to meet costs beyond those incurred by clutch formation. Date of initiation of rapid follicle growth was related to lipid reserve dynamics; lipid reserves at initiation and the rate of lipid use both declined through the season. Protein reserves declined slightly with commitment of protein to the clutch and with date of initiation of rapid follicle growth. Use of mineral reserves for first nests was negligible. Renesting females did not use nutrient reserves. Lipid reserve levels were positively related to the amount of lipid reserves needed to complete the clutch and clutch sizes predicted from a lipid dynamics model were consistent with known clutch sizes. Similar relationships did not exist for protein. We suggest that lipid reserve levels affect timing of nesting and proximately limit clutch size of Northern Pintails.

Alaska↗
USGS1994

Demography and movements of the omao (Myadestes obscurus)

Density, age-specific survival, timing of breeding and molting, and movements of the Omao or Hawaiian Thrush (Myadestes obscurus) were studied at four sites on the island of Hawaii. Mean monthly density (birds/ha) was 3.23 +- 0.57, 1.07 +- 0.33, 3.23 +- 0. 16, and 3.74 +- 0.36 at Kau Forest, Hamakua. Keauhou Ranch, and Kilauea Forest study areas, respectively. Annual survival of juvenile Omao (0.40 +- 0.09) was lower than that of adults (0.66 +- 0.08). Emigration and mortality was greatest during November through May. Breeding and molting occurred throughout the year, with peak breeding in May through July. Omao showed strong site fidelity and were highly sedentary. Mean home range size (n = 39) was 2.20 t 0.26 ha and did not differ between sexes or study sites.

Condor↗
USGS1993

Behavioral ecology of black-legged kittiwakes during chick rearing in a failing colony

Compared with their Atlantic counterparts, Black-legged Kittiwakes ( Rissa tridactyla ) in North Pacific colonies are notably unproductive. A large colony on Middleton Island, Alaska, has in most years since 1981 seen complete breeding failure and the population has declined by half. We compared parent-offspring behaviors in this colony during two years that differed in overall breeding success. Potential indicators of food stress included parental attendance at the nest, foraging trip lengths, chick feeding and begging rates, and sibling aggression. Whereas chick feeding and begging rates were strongly correlated with overall breeding performance, patterns of time allocation by adults (nest attendance and foraging trips) were not. Contrasts between years and comparisons with data from other colonies in and outside Alaska point to food shortage as the likely cause of recurrent breeding failure on Middleton.

Alaska↗
USGS1993

Body composition of wintering canvasbacks in Louisiana: Dominance and survival implications

I studied effects of sex, age, and month on body mass and composition of Canvasbacks ( Aythya valisineria ) at Catahoula Lake (CL) and the Mississippi River Delta (MRD), Louisiana, in winter 1987-1988. Size-adjusted body mass and fat varied by age, month, and site. Fat levels in immatures were greater at MRD than at CL, but changed similarly at both sites. Adults at MRD were also fatter than those at CL in early winter, especially in December, but fat levels of all birds increased from early to late winter and were equivalent by late winter. Body protein adjusted for structural size varied by age, month, and site, and sex, month, and site. Protein levels by site were higher in adults and males than in immatures and females, but sex- and age-related differences averaged <11 g (5%). Changes in size-adjusted leg muscle protein (index of feeding activity) and body fat were positively associated. This relation (my measure of feeding efficiency) was not affected by sex or age of Canvasbacks, implying that all birds at CL or MRD fed at similar efficiencies by month. At both sites, females were fatter than males; thus, although males were larger and potentially dominant to females, it appears that females were not disadvantaged in their acquisition of nutrients during the year of study. Body mass of CL and MRD birds in winter 1987-1988 was greater than that of Canvasbacks wintering elsewhere. If overwinter and annual survival of Canvasbacks are related to their relative body mass during winter, then survival probabilities of CL and MRD birds may be high compared to other wintering populations.

Louisiana↗
USGS1993

Survival and pre-fledging body mass in juvenile emperor geese

A positive relationship exists between fledgling body mass and juvenile survival for some altricial (Krementz et al. 1989, Magrath 1991, Linden et al. 1992) and precocial (Owen and Black 1989, Longcore et al. 1991, Francis et al. 1992) species. Because the energetic demands of migration are high, physiologic condition may be a proximate determinate of juvenile survival in geese. Owen and Black (1989) found that pre-fledging body mass of Barnacle Geese ( Branta leucopsis ) was positively related to juvenile survival to winter. First-year survival in Lesser Snow Geese ( Chen caerulescens caerulescens ) was also affected by pre-fledging body mass (Francis et al. 1992). It is not clear, however, when such mass-related mortality occurs. Both species migrate >3,000 km to wintering areas, but make use of fall staging areas while en route (Owen 1980, Francis and Cooke 1992). Survival fo geese between fledging and staging areas has not been addressed. Measurement of survival during this interval could provide insight to the timing of juvenile mortality in arctic geese.

Alaska↗
USGS1993

Estimation of lipids and lean mass of migrating sandpipers

Estimation of lean mass and lipid levels in birds involves the derivation of predictive equations that relate morphological measurements and, more recently, total body electrical conductivity (TOBEC) indices to known lean and lipid masses. Using cross-validation techniques, we evaluated the ability of several published and new predictive equations to estimate lean and lipid mass of Semipalmated Sandpipers (Calidris pusilla) and White-rumped Sandpipers ( C. fuscicollis ). We also tested ideas of Morton et al. (1991), who stated that current statistical approaches to TOBEC methodology misrepresent precision in estimating body fat. Three published interspecific equations using TOBEC indices predicted lean and lipid masses of our sample of birds with average errors of 8-28% and 53-155%, respectively. A new two-species equation relating lean mass and TOBEC indices revealed average errors of 4.6% and 23.2% in predicting lean and lipid mass, respectively. New intraspecific equations that estimate lipid mass directly from body mass, morphological measurements, and TOBEC indices yielded about a 13% error in lipid estimates. Body mass and morphological measurements explained a substantial portion of the variance (about 90%) in fat mass of both species. Addition of TOBEC indices improved the predictive model more for the smaller than for the larger sandpiper. TOBEC indices explained an additional 7.8% and 2.6% of the variance in fat mass and reduced the minimum breadth of prediction intervals by 0.95 g (32%) and 0.39 g (13%) for Semipalmated and White-rumped Sandpipers, respectively. The breadth of prediction intervals for models used to predict fat levels of individual birds must be considered when interpreting the resultant lipid estimates.

The Condor↗
USGS1996

Survival of northern pintail ducklings on the Yukon-Kuskokwim Delta, Alaska

We studied survival rates of Northern Pintail ( Anas acuta ; hereafter pintail) broods and ducklings along the lower Kashunuk River on the Yukon-Kuskokwim Delta, Alaska. Survival rates were determined for 770 ducklings in 111 broods. Brood sizes at hatch were smaller in 1993 versus 1991 and 1992. Duckling survival rates were lower than those reported in previous studies and differed among years. Survival rates of ducklings declined with hatching date at a rate of 0.6% per day. Most mortality occurred during the first 10 days after hatch. Duckling survival rates were correlated with reported annual and seasonal variation in nesting success. This covariation probably results in large geographic and annual fluctuations in pintail production on the Yukon-Kuskokwim Delta. Early nesting pintails had better nesting success and duckling survival, which may offset higher nutritional costs of early nesting through higher recruitment.

Alaska↗
USGS1996

Age-specific survival and philopatry in three species of European ducks: A long-term study

Capture-recapture and band recovery models were used to estimate age-specific survival probabilities for female Northern Shovelers (Anas clypeata), Common Pochards (Aythya ferina), and Tufted Ducks (Aythya.fuligula) at Engure Marsh, Latvia, in 1964-1993. We banded more than 65,100 day-old ducklings of both sexes and captured 10,211 incubating females (3,713 new bandings and 6,498 recaptures). We developed a set of 3-age capture-recapture models to estimate annual survival rates for female ducklings, yearlings (SY), and adults (ASY) using programs SURGE and SURVIV and selected parsimonious models using a method developed bv Akaike (1973). Survival rates of SY and ASY females were highest-for Tufted Ducks intermediate for Common Pochards, and lowest for Northern Shovelers. Survival rates of SY and ASY females varied in parallel for shovelers and pochards. We believe that much of the difference in survival estimates between SY and ASY birds was caused by mortality rather than permanent emigration. Estimates of day-old duckling survival, reflecting both mortality and permanent emigration, were 0.12 for shoveler, 0.06 for pochard, and 0.03 for Tufted Duck. For all species, duckling survival varied over years, but the pattern of variation was not similar to that of the other age classes. Estimates of survival using band recovery data for SY + ASY female pochards and Tufted Ducks were similar to the capture-recapturee stimates, suggestingt hat surviving females returned to the breeding marsh with probabilities approaching 1.

Condor↗
USGS1996

Variation in egg size of the northern pintail

Egg size is an important determinant of reproductive investment by birds. For many species, total investment in a clutch is limited by the size of stored reserves (Ankney and MacInnes 1978, Esler and Grand 1994a). Egg size determines the unit by which these stored reserves are partitioned. Individual females in most species of waterfowl show a high repeatability for egg size, implying that individual either cannot, or do not, alter their egg size in response to varying environmental conditions (batt and Prince 1979, Duncan 1987, Laurila and Hario 1988, Lessells et al 1989, Flint and Sedinger 1992). Thus differences in egg size appear to represent different reproductive strategies among individuals. Fitness can be measured by the number of offspring an individual contributes to a population. Egg size may be related to fitness in some species fo waterfowl as young from larger eggs are better able to survive extreme conditions (Ankney 1980, Thomas and Brown 1988). Birds laying larger clutches are almost always more fit as they fledge more young (Lessells 1986, Rockwell et al 1987, Flint 1993). These fitness patterns create the potential for a trade-off between clutch size and egg size where females laying large clutches of small eggs have the same fitness as females laying smaller clutches of large eggs. The fact that Northern Pintails ( Anas acuta ) utilize stored reserves (Mann and Sedinger 1993, esler and Grand 1994a) and have a high repeatability for egg size (i.e. egg size is fixed) (Duncan 1987), makes them candidates to engage in clutch size=egg size trade-offs (Rowher 1988, Rowher and Eisenhauer 1989). An inverse relationship between egg size and clutch size would be indicative of a phenotypic trade-off among these fitness components. Our goal in this study was to describe egg size variation in Northern Pintails (hereafter pintails) with regard to female age, body size, clutch size, year, initiation date, and nesting attempt. We compare our results to those from other populations of nesting pintails and discuss whether phenotypic clutch size-egg size tradeoffs exist for pintails.

Alaska↗
USGS1996

Black brant from Alaska staging and wintering in Japan

Black brant (Branta bernicla nigricans) nest in colonies in arctic Canada, Alaska, and Russia (Derksen and Ward 1993, Sedinger et al. 1993). Virtually the entire population stages in fall at Izembek Lagoon near the tip of the Alaska Peninsula (Bellrose 1976) before southward migration (Dau 1992) to winter habitats in British Columbia, Washington, Oregon, California, and Baja California (Subcommittee on Black Brant 1992). A small number of black brant winter in Japan, Korea, and China (Owen 1980). In Japan 3,000&ndash;5,000 brant of unknown origin stop over in fall, and a declining population (<1,000) of birds winter here, primarily in the northern islands (Brazil 1991, Miyabayashi et al. 1994). Here, we report sightings of brant in Japan that were marked in Alaska and propose a migration route based on historical and recent observations and weather patterns.

Alaska↗
USGS1993

Distribution and abundance of Marbled Murrelets in Alaska

Most seabirds breed in colonies on offshore islands, but throughout most of their range from California to Alaska Marbled Murrelets ( Brachyramphus marmoratus ) fly inland to nest on trees in old-growth coniferous forests. Some fraction of the murrelet population nests on the ground in Alaska. The relative distribution and abundance of murrelets in forested and treeless areas of Alaska is poorly known. We analyzed data on seabird abundance at sea and on colonies in Alaska that were obtained under the Outer Continental Shelf Environmental Assessment Program during the 1970s and 1980s. Whereas most seabirds may be censused at breeding colonies, murrelet populations must be estimated from surveys at sea. We compared colony and pelagic population estimates for 13 colonial seabird species in Alaska and found that they were strongly correlated (r 2 = 0.94). We therefore used at-sea censuses to estimate that at least 160,000 murrelets reside in Alaska. Most (97%) Marbled Murrelets are concentrated offshore of large tracts of coastal coniferous forests in southeast Alaska (Alexander Archipelago), Prince William Sound, and the Kodiak Archipelago.

Alaska↗
USGS1998

Status and trends of the ashy storm-petrel on Southeast Farallon Island, California, based upon capture-recapture analyses

We conducted a capture-recapture study on the population size and trends of the Ashy Storm-petrel ( Oceanodroma homochroa ) on Southeast Farallon Island (SEFI), California, based upon data collected in 1971, 1972, and 1992. From March through August, birds were lured to fixed-site sampling locations using taped vocalization playback. Using program JOLLY, we estimated population size and evaluated statistical models using goodness-of-fit and Likelihood Ratio tests. On the southwestern slope of Lighthouse Hill, amidst prime breeding habitat, numbers of breeding birds decreased from 1,271 ± 140 (x ± SE) in 1972 to 710 ± 117 in 1992, a decline of 44% (approximate 95% CI = 22-66% decline; λ = -2.8% per annum); for a variety of reasons, we consider this to be the most reliable indicator of population change. In 1971, on a portion of SEFI relatively disjunct from the sampling area in 1972, 2,131 ± 322 breeding birds were estimated. To produce an overall early 1970s estimate with which to compare to 1992, we summed population estimates from 1971 and 1972. An overall value of 6,461 birds, of which 3,402 (53%) were breeders, was obtained for the early period. In 1992, the overall population in roughly the same area was estimated at 4,284 ± 409 birds, of which 1,990 ± 408 (46%) were presumed breeders. These results, encompassing peripheral as well as more centrally located storm-petrel habitat, indicate an overall population decline of 34% and a comparable decline in breeding birds of 42% over the past two decades. However, oceanographic conditions varied between 1971-1972 and 1992, and reduced food availability in 1992 may have influenced colony attendance and breeding effort. Nonetheless, the apparent population decline over the past 20 years suggests that the species warrants management and/or additional protective status.

Condor↗
USGS1998

Demography of an introduced red-billed Leiothrix population in Hawaii

Relative abundance, timing of breeding and molting, annual survival, and philopatry of an introduced population of Red-billed Leiothrix ( Leiothrix lutea ) were studied at four sites on the island of Hawaii. Numbers of leiothrix on our study areas showed a regular cyclical pattern, with highest numbers during the breeding season. Peak breeding occurred May-August, followed by peak molting of flight and body feathers in August-October. Flocking behavior increased post-breeding, and many leiothrix left the study areas during the fall and winter months. Populations on two intensive study areas were stable, with high annual survival (x ± SE = 0.581 ± 0.115 for hatching-year birds and 0.786 ± 0.047 for adults). Leiothrix seem to be relatively unaffected by avian diseases that have decimated some Hawaiian bird populations, and yet reasons for their large historical population fluctuations remain unexplained.

Hawaii↗