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At least 37 records · Page 2Linked to original sources
USGS1974

Retraction of a longevity record for a 36-year-old herring gull

The longevity record for a 36-year-old Herring Gull, Larus argentatus (Pettingill 1967, Auk 84: 123), is erroneous. Herring Gull with band number A-676871, the basis of the record, was found dead on 20 June 1966 on the shore of Little Traverse Bay near Petoskey, Michigan, and reported to the Bird Banding Laboratory. The laboratory then mistakenly advised Pettingill that this gull was banded by him on 29 June 1930 on coastal Maine. He actually banded Herring Gull number A-676871 as a young bird on one of the Beaver Islands in Lake Michigan on 8 July 1948. The gull was thus 18 instead of 36 years old.

The Auk↗
USGS1976

Bird collections in the United States and Canada: Addenda and corrigenda

Since publication of our report on the avian collections in the United States and Canada (Banks, Clench, and Barlow 1973, Auk 90: 136- 170) several changes and additions have come to our attention. In some cases, recent curatorial work has resulted in more accurate counts to replace previous estimates. Other collections have grown markedly in the last few years. Some important private or institutional collections have been transferred to other jurisdictions. Finally, we have received a few completely new reports from collections that were unknown to us or that were unresponsive to our original requests for information.

The Auk↗
USGS2001

Avian furcula morphology may indicate relationships of flight requirements among birds

This study examined furcula (wishbone) shape relative to flight requirements. The furculae from 53 museum specimens in eight orders were measured: 1) three-dimensional shape (SR) as indicated by the ratio of the direct distance between the synostosis interclavicularis and the ligamentous attachment of one of its clavicles to the actual length of the clavicle between those same two points, and 2) curvature within the primary plane (LR) as indicated by the ratio of the length of the clavicle to the sum of the orthogonal distances between the same points using a projected image. Canonical discriminant analysis of these ratios placed the individuals into a) one of four general flight categories and b) one of eight taxonomic orders. The four flight categories were defined as: i) soaring with no flapping, ii) flapping with no soaring, iii) subaqueous (i.e., all wingbeats taking place under water), and iv) partial subaqueous (i.e., wingbeats used for both aerial and submerged flapping). The error rate for placement of the specimens in flight categories was only 26.4%, about half of the error rate for placement in taxonomic orders (51.3%). Subaqueous fliers (penguins, great auks) have furculae that are the most V-shaped. Partial subaqueous fliers (alcids, storm petrels) have furculae that are more U-shaped than the subaqueous fliers but more V-shaped than the aerial flapping fliers. The partial subaqueous fliers have furculae that are also the most anteriorly curved, possibly increasing protraction capability by changing the angle of applied force and increasing attachment area for the origin of the sternobrachialis pectoralis. The increased protraction capability can counteract profile drag, which is greater in water than in air due to the greater density of water. Soaring birds have furculae that are more U-shaped or circular than those of flapping birds and have the smallest range of variation. These results indicate that the shape of the furcula is functionally related to general differences in flight requirements and may be used to infer relationships of these requirements among birds.

Journal of Morphology↗
USGS2009

Impacts of experimentally increased foraging effort on the family: offspring sex matters

We examined how short-term impacts of experimentally increased foraging effort by one parent reverberate around the family in a monomorphic seabird (little auk, Alle alle), and whether these effects depend on offspring sex. In many species, more effort is required to rear sons successfully than daughters. However, undernourishment may have stronger adverse consequences for male offspring, which could result in a lower fitness benefit of additional parental effort when rearing a son. We tested two alternative hypotheses concerning the responses of partners to handicapping parents via feather clipping: partners rearing a son are (1) more willing or able to compensate for the reduced contribution of their mate, or (2) less willing or able to compensate, compared to those rearing a daughter. Hypothesis 1 predicts that sons will be no more adversely affected than daughters, and the impact on parents will be greater when rearing a son. Hypothesis 2 predicts that sons will be more adversely affected than daughters, and parents raising a son less affected. Although experimental chicks of both sexes fledged in poorer condition than controls, sons attained higher mass and more rapid growth than daughters in both groups. Clipped parents lost a similar proportion of their initial mass regardless of chick sex, whereas partners of clipped birds lost more mass when rearing a son. These results support hypothesis 1: impacts of increased foraging effort by one parent were felt by offspring, regardless of their sex, and by the partners of manipulated birds, particularly when the offspring was male. ?? 2009 The Association for the Study of Animal Behaviour.

Animal Behaviour↗
USGS1999

Outbreeding depression in hybrids between odd-and even-broodyear pink salmon

Fewer F 2 hybrids between even- and odd-broodline pink salmon ( Oncorhynchus gorbuscha ), which are lines that are genetically isolated by their strict two-year life cycle, survived than did F 2 controls, indicating outbreeding depression. Cryopreserved sperm of 40 broodyear 1990 males and of 40 broodyear 1991 males fertilized equal subsamples of eggs from 40 broodyear 1992 females. Return rates of F 1 hybrids (1.73%) and controls (1.63%) in 1994 did not differ significantly ( P =0.30). F 2 hybrid and control crosses were made from 40 males and 40 females selected at random from each return group. Offspring were differentially marked and released. In 1996, returns differed significantly ( P =0.011) between hybrids ( n =34, 0.34%) and controls ( n =44, 0.42%). The low rate of return of the control fish was similar to the measured return of a much larger group of tagged Auke Creek pink salmon, and probably not an artifact of the experiment. Although no increase in fluctuating asymmetry of paired meristic counts was observed in either F 1 or F 2 hybrids, size and some meristic counts of hybrids exceed measurements of controls, suggesting heterosis for those traits. The observations of decreased survival in F 2 hybrids confirm previous work [Gharrett, A.J., Smoker, W.W., 1991. Two generations of hybrids between even- and odd-year pink salmon ( O. gorbuscha ). Canadian Journal of Fisheries and Aquatic Science 48(9) 1744–1749]. Although genetic divergence between pink salmon broodlines is large and outbreeding depression might be expected in such unlikely hybrids, the results document the occurrence of outbreeding depression in salmon and signal caution in making management and aquacultural decisions that may create the possibility of outbreeding depression in self-sustaining or cultured populations.

Aquaculture↗
USGS2003

Deciphering the social structure of Marbled Murrelets from behavioral observations at sea

We surveyed Marbled Murrelets ( Brachyramphus marmoratus ) daily from small boats in Auke Bay and Fritz Cove, Alaska, from May through August 1992 and 1993. Differences in numbers of juveniles and in the timing of their presence in the study area between the two years indicated that breeding phenology was late and productivity was low in 1992 compared to 1993. This difference was consistent with variability in the physical environment. Of 99 fish identified in the bills of fish-holding adult murrelets, 81 (82%) were Pacific Sand Lance ( Ammodytes hexapterus ). Counts of fish-holding adult murrelets were significantly higher in the evening than at any other time of day. Time of day had no significant effects on counts of fledglings, indicating that juveniles were moving into and out of the study area during the day. Murrelets were predominantly found in groups of two or more, even during incubation, suggesting that murrelets incur an appreciable benefit, such as increased foraging efficiency, from foraging in groups. For both summers, there was no correlation between counts of murrelets on the water and numbers of murrelet detections in the adjacent forest. We suggest that many behavior patterns of the Marbled Murrelet (displaying, choosing of mates, and pair-bonding, finding of nest sites and successful foraging of juveniles) may be socially facilitated.

Waterbirds↗
USGS2000

Temporal variability in abundance of Marbled Murrelets at sea in southeast Alaska

We examined effects of season, time of day, tide stage, tidal oscillation, and sea surface temperature on Marbled Murrelet ( Brachyramphus marmoratus ) abundance and distribution at sea. We also evaluated whether constraining surveys to specific time periods or tide stages would reduce temporal variability in counts. Murrelets were surveyed daily from small boats and from shore in Auke Bay and Fritz Cove, Alaska, from May through August in 1992 and 1993. Murrelet numbers were high before egg-laying, declined by more than half during egg-laying and incubation and were highly variable during chick-rearing and fledging. Murrelet numbers were highest in early and late morning and declined throughout the day, sometimes increasing slightly in the evening. Peak murrelet numbers occurred on high or falling morning tides, especially in shallow areas where Pacific sand lance ( Ammodytes hexapterus ) were abundant. Differences between years in murrelet abundance and breeding phenology probably resulted from interannual differences in the pattern of seasonal warming and subsequent effects on production at lower trophic levels. We recommend that surveys for trends in abundance in Southeast Alaska be conducted in early morning, in June, at high or falling tides. Power analyses indicated that surveys conducted in this manner would minimize the number of years required to detect a significant change in abundance.

Alaska↗
USGS2004

Baseline Characteristics of Jordan Creek, Juneau, Alaska

Anadromous fish populations historically have found healthy habitat in Jordan Creek, Juneau, Alaska. Concern regarding potential degradation to the habitat by urban development within the Mendenhall Valley led to a cooperative study among the City and Borough of Juneau, Alaska Department of Environmental Conservation, and the U.S. Geological Survey, that assessed current hydrologic, water-quality, and physical-habitat conditions of the stream corridor. Periods of no streamflow were not uncommon at the Jordan Creek below Egan Drive near Auke Bay stream gaging station. Additional flow measurements indicate that periods of no flow are more frequent downstream of the gaging station. Although periods of no flow typically were in March and April, streamflow measurements collected prior to 1999 indicate similar periods in January, suggesting that no flow conditions may occur at any time during the winter months. This dewatering in the lower reaches likely limits fish rearing and spawning habitat as well as limiting the migration of juvenile salmon out to the ocean during some years. Dissolved-oxygen concentrations may not be suitable for fish survival during some winter periods in the Jordan Creek watershed. Dissolved-oxygen concentrations were measured as low as 2.8 mg/L at the gaging station and were measured as low as 0.85 mg/L in a tributary to Jordan Creek. Intermittent measurements of pH and dissolved-oxygen concentrations in the mid-reaches of Jordan Creek were all within acceptable limits for fish survival, however, few measurements of these parameters were made during winter-low-flow conditions. One set of water quality samples was collected at six different sites in the Jordan Creek watershed and analyzed for major ions and dissolved nutrients. Major-ion chemistry showed Jordan Creek is calcium bicarbonate type water with little variation between sampling sites.

Open-File Report↗
USGS1994

Association of viral hemorrhagic septicemia virus with epizootic hemorrhages of the skin in Pacific herring Clupea harengus pallasi from Prince William Sound and Kodiak Island, Alaska, USA

Only one-third of the Pacific hernng Clupea harengus pallasi expected to spawn in Prince William Sound (PWS), Alaska, USA, in sprlng 1993 were observed. Of these herring, 15 to 43 '% had external ulcers or subdermal hemorrhages of the skln and fins. A rhabdovirus identified as the North American strain of viral hemorrhagic septicemia virus (VHSV) was isolated from affected herring and 1 Pacific cod Gadus macrocephalus with skin lesions from PWS, and from herring with similar lesions collected near Kodiak Island. No other pathogens were detected in the herring examined. Although VHSV may have been responsible for the skin lesions, there was no confirmed mass herring mortality observed in PWS; hence the actual cause of the reduced herring numbers is still unknown. The same strain of VHSV was subsequently isolated from captive juvenile herring collected from Auke Bay, Alaska, near Juneau, from herring in British Columbia, Canada, and from Puget Sound, Washington, USA. These findings suggest the virus is an opportunistic pathogen that is widely indigenous to Pacific herring populations in the Pacific Northwest and that herring are a significant marine reservoir for North American VHSV.

Alaska↗
USGS1975

A.B.A. Checklist: Birds of Continental United States and Canada

The purpose of this Checklist is to provide a complete up-to-date list of the bird species that have been recorded in the 49 continental United States and Canada. This list includes the native North American breeding species, the regular visitors, the accidentals from other countries that are believed to have strayed here without the direct aid of man, and those introduced species that have become well established and are now a true part of our avifauna. The A.B.A. Checklist will be revised at frequent intervals to keep up with changes in classification and additions to the avifauna. This edition includes a total of 794 species. For details of geographic range and for a complete list of re<;ognized subspecies the reader is referred to the latest (5th) edition of the A. O. U. Check-List of North American Birds, prepared by a committee of the American Ornithologists' Union, 1957, and to the 32nd Supplement published in April 1973 (Auk 90:411-419).

Book↗
USGS2002

Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1

The North American Waterbird Conservation Plan (the Plan) is the product of an independent partnership of individuals and institutions having interest and responsibility for conservation of waterbirds and their habitats in the Americas. This partnership - Waterbird Conservation for the Americas - was created to support a vision in which the distribution, diversity, and abundance of populations and habitats of breeding, migratory, and nonbreeding waterbirds are sustained or restored throughout the lands and waters of North America, Central America, and the Caribbean. The Plan provides a continental-scale framework for the conservation and management of 210 species of waterbirds, including seabirds, coastal waterbirds, wading birds, and marshbirds utilizing aquatic habitats in 29 nations throughout North America, Central America, the islands and pelagic waters of the Caribbean Sea and western Atlantic, the U.S.-associated Pacific Islands and pelagic inland and pelagic waters of the Pacific. Birds as familiar as herons, loons, pelicans, and gulls, as well as the lesser known albatrosses, petrels, auks, and rails are among the species considered in the Plan. These birds' dependence on aquatic habitats such as wooded swamps, stream corridors, salt marshes, barrier islands, continental shelf waters and open pelagic waters make them especially vulnerable to the myriad threats facing water and wetland resources globally. In addition, the congregatory behavior of many waterbirds increases population risks by concentrating populations in limited areas.

Book↗
USGS1986

Changing landscapes and the cosmopolitism of the eastern Colorado avifauna

The avifauna of continental North America has changed dramatically since colonial times. Excessive hunting contributed, at least in part, to the extinction of birds such as the great auk ( Pinguinus impennis ) and passenger pigeon ( Ectopistes migratorius ), while more recently organochlorine insecticide residues have resulted in drastic reductions in numbers of brown pelicans ( Pelecanus occidentalis ) (Anderson et al. 1975) and other species. Generally, however, vertebrate populations change in direct response to changes in their habitats. For example, herring gulls ( Larus argentatus ) have increased in numners (Kadlec and Drury 1968) with urbanization of the New England coastline, in the same locations formerly occupied by the extinct heath hen ( Tympanuchus cupido cupido ). Also, passerine birds of forest interiors have declined in numbers with fragmentation of the eastern deciduous forest into small stands; this fragmentation has led to increases in numbers of edge species (Robbins 1979, Ambuel and Temple 1983). Even subtle community shifts can introduce new competitive processes that can augment population changes among species (Brittingham and Temple 1983). Such studies of broad-scale changes in vegetative communities and their influence on native wildlife species have fostered the recent topical emphasis on "conservation biology" (Soule and Wilcox 1980, Soule 1985) and "landscape ecology" (Burgess and Sharpe 1981, Harris 1984:25-43). As changes in landscapes are causing subtle (but potentially dramatic) changes in the distribution of native species, conservation biologists are finding that mere presence-absence data on populations, or even accurate information on reproductive success, is inadequate to evaluate management activities or environmental perturbations. The principles of "conservation genetics" are attracting interest in the management of natural preserves especially (Schonewald-Cox et al. 1983). Changing patterns in landscape complexion or genetic makeup of a population are difficult to detect locally. Contemporary issues in the conservation of native species demand regional and continental perspectives (Samson and Knopf 1982). Thus, management activities at specific sites are often viewed as short-sighted by planners and conservation critics. This paper illustrates how these contemporary theories can influence a local conservation perspective. That perspective is developed around historical processes that have led to cosmopolitism of the local avifauna on the Colorado Division of Wildlife's South Platte Wildlife Management Area (SPWMA) near Crook, Colorado.

Colorado↗
USGS2015

Changes in thyroid parameters of hatchling American kestrels ( Falco sparverius ) following embryonic exposure to technical short chain chlorinated paraffins (SCCPs; C 10-13 , 55.5% CL)

Chlorinated paraffins (CPs) are complex mixtures of polychlorinated n-alkanes categorized according to their carbon chain length: short chain (SCCPs, C10 – C13), medium (C14 - C17), and long chain (C>17), chlorinated paraffins. SCCPs are primarily used in metalworking applications, as flame retardants, and in paints, adhesives, sealants, textiles, plastics and rubber (UNEP 2012). In 2012, the United Nations Environment Program (UNEP 2012) reported in the Revised Draft Risk Profile for SCCPs, that CPs were produced in the United States, the European Union (EU), Slovakia, Brazil, India, Japan and China. While annual global consumption of SCCPs is large (>25 tonnes/year), it has sharply declined over the past 20 years. SCCPs are released through wastewater, landfills, and air emissions (UNEP 2012). Concentrations of SCCPs have been reported in fish and marine mammals in North and South America, Europe, Japan, Greenland and the Arctic (UNEP 2012 and references therein). Characterization of SCCP concentrations and exposure in terrestrial wildlife is limited. In 2010, SCCP concentrations were reported in the eggs of yellow-legged gulls (Larus michahellis) (4536 ± 40 pg/g wet weight (ww)) and Audouin’s gulls (Larus audouinii) (6364 ± 20 pg/g ww) in Spain (Morales et al. 2012), and little auks (Alle alle) (5 - 88 ng/g ww) and kittiwakes (Rissa tridactyla) (5 - 44 ng/g ww) in the European Arctic (Reth et al. 2006). In Sweden, muscle of ospreys contained CPs of unspecified chain length (Jansson et al. 1993). Although the toxicity of SCCPs has been demonstrated in aquatic invertebrates, fish, frogs, and laboratory rats, there are limited avian studies and these reported no effects of SCCPs on egg parameters of domestic hens (Gallus gallus domesticus) and ducks (Anas platyrhynchos) (UNEP 2012). Despite reported accumulation of SCCPs in wild birds, to our knowledge, exposure-related toxicities and effects with respect to avian wildlife remain unknown.

Organohalogen Compounds↗
USGS1983

Nestling growth relationships of brown-headed cowbirds and dickcissels

Data on nestling growth of brood parasites and their hosts are surprisingly few in the literature, Even the Brown-headed Cowbird ( Molothrus ater ), whose host relations have been studied in some other respects, has not been studied in any detail from this standpoint. This is particularly regrettable because the lack of host specialization and high incidence of multiple parasitism in this species recommend it for intensive studies of parasite-host growth relationships. Isolated or fragmentary records of growth in cowbirds are available in Friedman (The Cowbirds, C. C. Thomas, Springfield, Illinois, 1929), Pickwell (Trans, Acad. Sci. St. Louis 27:1-160, 1931), Herrick Wild Birds at Home, Appleton-Century, New York, New York, 1935), Nice (Trans. Linn. Soc. N.Y. 4, 1937; Wilson Bull. 51:233-239, 1939), Mayfield (The Kirtland's Warbler, Cranbrook Inst, Sci., Illinois, 1960), and Nolan (Ornithol, Monor, No. 26. 1978). Hann (Wilson Bull. 49:145-237. 1937) illustrated the growth of five cowbirds raised in three nests of the Ovenbird ( Seiurus aurocapillus ), Norris Wilson Bull, 59-83-103, 1947) provided data for five individuals raised by different host species, and Scott (Wilson Bull, 91:464-466, 1979) presented pooled growth data for nine individuals raised by three different host species. King (Auk 90:19-34, 1973) measured the growth of Shiny Cowbirds ( Molothrus bonariensis ) in nests of Rufous-collared Sparrows ( Zonotrichia capensis ) and found that broods of two cowbirds grew at a substantially slower rate than broods of one, He suggested that Z. capensis could rear a maximum of two cowbirds or four sparrows, or an equivalent combination. In 1974 collected data on the growth relationships of Brown-headed Cowbirds and Dickcissels ( Spiza americana ) in prairie habitat in eastern Kansas (Konza Prairie Research Natural Area). The intensity of cowbird parasitism in this study was extremely high - I found nests containing as many as nine cowbird eggs and three host eggs, More than one cowbird was evidently laying in many of the nests, behavior that may present some intricate evolutionary problems with respect to clutch-size manipulation by cowbirds. Fifty-nine of 65 nests were parasitized 91%, and the mean number of cowbird eggs per parasitized nest was 3.1 (SD 1.74). Dickcissels raised up to five young in mixed broods of various composition. Brood composition at fledging in 27 successful nests (42% of the total) averaged 1.6 Dickcissels and 1.3 cowbirds.

Kansas↗
USGS2023

High voltage: The molecular properties of redox-active dissolved organic matter in northern high-latitude lakes

Redox-active functional groups in dissolved organic matter (DOM) are crucial for microbial electron transfer and methane emissions. However, the extent of aquatic DOM redox properties across northern high-latitude lakes and their relationships with DOM composition have not been thoroughly described. We quantified electron donating capacity (EDC) and electron accepting capacity (EAC) in lake DOM from Canada to Alaska and assessed their relationships with parameters from absorbance, fluorescence, and ultrahigh resolution mass spectrometry (FT-ICR MS) analyses. EDC and EAC are strongly tied to aromaticity and negatively related to aliphaticity and protein-like content. Redox-active formulae spanned a range of aromaticity, including highly unsaturated phenolic formulae, and correlated negatively with many aliphatic N and S-containing formulae. This distribution illustrates the compositional diversity of redox-sensitive functional groups and their sensitivity to ecosystem properties such as local hydrology and residence time. Finally, we developed a reducing index ( RI ) to predict EDC in aquatic DOM from FT-ICR MS spectra and assessed its robustness using riverine DOM. As the hydrology of the northern high-latitudes continues to change, we expect differences in the quantity and partitioning of EDC and EAC within these lakes, which have implications for local water quality and methane emissions.

Environmental Science & Technology↗
USGS2022

Hydrologic and landscape controls on dissolved organic matter composition across western North American Arctic lakes

Northern high-latitude lakes are hotspots for cycling dissolved organic carbon (DOC) inputs from allochthonous sources to the atmosphere. However, the spatial distribution of lake dissolved organic matter (DOM) is largely unknown across Arctic-boreal regions with respect to the surrounding landscape. We expand on regional studies of northern high-latitude DOM composition by integrating DOC concentrations, optical properties, and molecular-level characterization from lakes spanning the Canadian Taiga to the Alaskan Tundra. Lakes were sampled during the summer from July to early September to capture the growing season. DOM became more optically processed and molecular-level aromaticity increased northward across the Canadian Shield to the southern Arctic and from interior Alaska to the Tundra, suggesting relatively greater DOM incorporation from allochthonous sources. Using water isotopes (δ 18 O-H 2 O), we report a weak overall trend of increasing DOC and decreasing aromaticity in lakes that were hydrologically isolated from the landscape and enriched in δ 18 O-H 2 O, while within-region trends were stronger and varied depending on the landscape. Finally, DOC correlated weakly with chromophoric dissolved organic matter (CDOM) across the study sites, suggesting that autochthonous and photobleached DOM were a major component of the DOC in these regions; however, some of the northernmost and wetland-dominated lakes followed pan-Arctic riverine DOC-CDOM relationships, indicating strong contributions from allochthonous inputs. As many lakes across the North American Arctic are experiencing changes in temperature and precipitation, we expect the proportions of allochthonous and autochthonous DOM to respond with aquatic optical browning with greater landscape connectivity and more internally produced DOM in hydrologically isolated lakes.

Global Biogeochemical Cycles↗
USGS1983

Pacific Coast Caspian Terns: Dynamics of an expanding population

Nesting distribution, age-related seasonal movements, survivorship, and mechanisms of population expansion in Pacific Coast Caspian Terns (Sterna caspia) were examined primarily through analysis of 412 recoveries of birds banded as juveniles between 1935 and 1980. Since the beginning of this century, the population has shifted from nesting in numerous small colonies associated with freshwater marshes in interior California and southern Oregon to nesting primarily in large colonies on human-created habitats along the coast. Colonies at Grays Harbor, Washington and San Francisco and San Diego bays, California account for 77% of the current Pacific Coast population (6,000 pairs), which has breeding and wintering areas separate from those of populations east of the continental divide. There also appears to be some segregation on the wintering grounds by birds from the three major colonies within the Pacific population. Age-related seasonal movements in the Pacific population are characterized by (1) a brief period of northward dispersal by newly fledged birds before migrating to the wintering grounds, (2) a residency on the wintering grounds through their second winter, (3) a return to the breeding grounds the third summer, when most birds are thought to prospect breeding sites and some may breed, and (4) attainment of adulthood the fourth summer, with subsequent annual movements between wintering and breeding grounds. The Pacific population has increased 70% since 1960, apparently all by intrinsic growth. Over half (57%) of the fledglings reach their fourth year, and they have a subsequent annual survival rate of 89% and a mean breeding life expectancy of 8.6 yr. An average annual fledging rate of 0.64 young per pair was calculated as necessary to have provided the observed growth of the population during its recent expansion. Growth of some of the individual colonies, however, particularly those in Washington, could only have resulted from extensive recruitment of birds from other Pacific Coast colonies. Philopatry is low in this population, and the growth of the northern colonies involved recruitment primarily of first-time breeders but also of some older adults. Factors promoting both first-time breeders and older adults to join new and often distant colonies are discussed.

California, Washington↗
USGS1983

Aspects of food finding by wintering Bald Eagles

We examined three aspects of food location by Bald Eagles ( Haliaeetus leucocephalus ) wintering along the Nooksack River, Washington. First, eagles used intra- and interspecific local enhancement to locate food. Second, the time that eagles spent aerially searching for food, as indicated by the percentage of eagles flying or soaring, was negatively correlated with relative food availability. Third, eagles often followed others when departing from or arriving at communal night roosts. Following was most frequent when all food was eliminated by flood waters, suggesting a possible food-location function of this behavior. During the flood period, adult eagles were followed more often than immatures.

Washington↗