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At least 235 records · Page 13Linked to original sources
USGS1994

Migrating shorebirds and habitat dynamics at a prairie wetland complex

We examined the responses of migrating shorebirds to habitat dynamics in a wetland complex on the Great Plains during 1989-1992. Availability of habitat was variable within and between seasons, but fluctuations in habitat were dampened when wetlands were considered as a complex rather than individually. Shorebirds exhibited an ability to colonize available habitat opportunistically, to occupy wet mud/shallow water habitat that became available during their residency period regardless of wetland history, and to use wet mud/shallow water habitat almost immediately upon its appearance. We found a significant relation between number of shorebirds and the area of wet mud/shallow water habitat, regardless of dramatic changes in habitat. Management for continental stopover sites for shorebirds requires the maintenance of complexes of potential habitat to assure resource alternatives for birds as local conditions vacillate.

The Wilson Bulletin↗
USGS1993

Status and population trends of Hawaii's native waterbirds, 1977-1987

Status and population trends of Hawaiis ’ native waterbirds were examined from 1977 through 1987. Waterbird population fluctuations were analyzed in relation to rainfall and land use dynamics. Numbers of Hawaiian Duck (Koloa) ( Anus wyvilliana ) and Hawaiian Common Moorhen ( Gallinula chloropus sandvicensis ) appeared stable over time; however, surveys were limited. Increase in Black-crowned Night-Heron ( Nycticorux nycticorux ) abundance appeared linked to expansion of aquaculture, particularly on Oahu, and not to climatic events. Annual rainfall patterns help explain and predict population fluctuations and anomalous distribution patterns involving Hawaiian American Coots ( Fulica americana alai ), moorhens, and Hawaiian Black-necked Stilts ( Himantopus mexicanus knudseni ). Coot, stilt, and moorhen populations fluctuated with climatic events, and intraisland dispersal to ephemeral wetlands occurred. Stilts exhibited regular inter-island migratory behavior, but coots dispersed in relation to major rainfall events. Seasonal fluctuation recorded for coots by past observers is the result of survey techniques not accounting for seasonal dispersal patterns.

Hawai'i↗
USGS1979

Nesting ecology of Arctic loons

Arctic Loons were studied on the Yukon-Kuskokwim Delta, Alaska, from the time of their arrival in May to their departure in September, in 1974 and 1975. Pairs arrived on breeding ponds as soon as sufficient meltwater was available to allow their take-off and landing. Loons apparently do not initiate nests immediately after their arrival, even when nest-sites are available. Delayed egg-laying may be dependent on a period of yolk formation. Delaying yolk formation until after arrival on nest ponds is an adaptation by loons to the variable time suitable habitat becomes available for nesting. Predation of eggs by Glaucous Gulls, Long-tailed and Parasitic jaegers and foxes varied in relation to the location of the nest-site, and the availability of alternate prey. Hatching success was the lowest recorded for Arctic Loons (5%) in 1974, when eggs of both loons and Cackling Geese were taken in large numbers by predators. Hatching success increased to 32% in 1975 when an abundance of tundra voles was observed. No loon eggs hatched after the hatching of the Cackling Goose eggs when this alternate prey was no longer available. Nests destroyed by foxes were predominantly along shorelines, and those by gulls and jaegers were predominantly on islands. Nest-site selection by Arctic Loons may reflect an adaptive response to varying selective pressures by their predators.

Alaska↗
USGS1979

Pomarine jaeger preys on adult black-legged kittiwake

On 5 June 1977, while on a cruise in the decomposing pack ice in the Bering Sea, we observed a light phase Pomarine Jaeger ( Stercorarius pomarinus ) attack, kill and feed on an adult Black-legged Kittiwake ( Rissa tridactyla ), 1 of approximately 10 individuals within 20 m of the ship's stern. We did not observe the birds until 1 min after the initial attack and do not know if the kittiwake was sitting or flying. No food was visible in the kittiwake's bill at the start of our observations nor was it observed regurgitating its stomach contents after the attack. During the first 5 min the kittiwake managed to become airborne a number of times but the jaeger maintained its hold and forced it back to the water. After 5 min the jaeger began to submerge the kittiwake's head, still holding it by the neck. Because of the kittiwake's struggling, the jaeger was unable to hold it under for more than 5 sec at a time. For the next 15 min it continued to submerge the victim's head, lift it out of the water, and then submerge it again. When it held the kittiwake under water, it kept both feet on its lower neck; this may have helped keep the head submerged. In the last 5 min of this activity, when the kittiwake offered little resistance, the jaeger occasionally used only its feet to push it under water. Other kittiwakes remained in the area, a few swimming within 2 m of the 2 birds. No attempt was made to mob the jaeger.

The Wilson Bulletin↗
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↗
USGS1987

Did the 1982-1983 El Niño-Southern Oscillation Affect Seabirds in Alaska?

The causes and effects of the oceanographic and atmospheric phenomena known as El Nino and the Southern Oscillation (ENSO) have been studied intensively in recent years (Cane 1983, Rasmusson and Wallace 1983, Barber and Chave 1983, Cane and Zebiak 1985). ENSOs occur at semiregular intervals of 3-4 years, and the stronger events have important biological consequences, including reduced breeding success and survival of seabirds in the central and eastern tropical Pacific Boersma 1978, Barber and Chavez 983, Schreiber and Schreiber 1984, Duffy 1986). The ENSO event of 1982-1983 was perhaps the strongest of this century Cane 1983), and there is evidence that seabird populations as far north as the Oregon coast (42-46'N) were adversely affected (Hodder and Graybill 1985, Bayer 1986). Here I examine evidence for similar effects on seabirds along the Alaskan coast.

Alaska↗
USGS1990

Nest-site selection by Emperor Geese and Cackling Canada Geese

Differences were found in habitat structure between nest sites of Emperor Geese ( Chen canagicus ) and Cackling Canada Geese ( Branta canadensis minim a) during a 5-year study (1982-1986) at Kokechik Bay, Alaska. Emperor Geese tended to select sites that afforded concealment from avian predators before incubation began. Cackling Canada Geese tended to select sites that enhanced avoidance of mammalian predators. Emperor Geese selected sites in areas away from open water, with tall dead vegetation adjacent to the nest site. Cackling Canada Geese selected sites close to shores of smaller ponds having more islands, and sometimes nested on islands, evidently enhancing avoidance of mammalian predators. During springs with heavy snow cover (>50% of surface covered on 25 May ), both species selected sites appreciably different from sites selected during springs with light snow cover (<25% on 18 May). During heavy snow years, both species selected sites with more short, dead vegetation. Emperor Geese differed from Cackling Canada Geese by selecting sites with more shrubs and were farther from ponds. Cackling Canada Geese tended to nest closer together than Emperor Geese. Differences in structural habitat characteristics at nest sites of Cackling Canada Geese were not related to nesting success, but successful Emperor Geese selected nest sites with more and taller dead vegetation than unsuccessful pairs. Although it was possible to identify "typical" nest sites of Emperor Geese and Cackling Canada Geese, many sites were used by both species. Factors such as the amount and duration of snow cover, drainage patterns, presence or absence of islands, and type and abundance of egg predators play important roles in influencing nest-site selection and ultimately the distribution and abundance of Emperor Geese and Cackling Canada Geese.

Alaska↗
USGS1992

Breeding distribution of the Black Turnstone

Eighty-five percent of the world population of Black Turnstones ( Arenaria melanocephala ) nest on the central Yukon-Kuskokwim Delta, Alaska, 65% concentrated in a narrow band of salt grass, graminoid, and dwarf shrub meadows within two km of the coast. An estimated 61,000 to 99,000 birds (95% CI), with a point estimate of 80,000 birds, breed on the central delta. About 15,000 others nest elsewhere in Alaska. Abundance varies among habitats and with distance from the coast. On the central delta, highest breeding densities occur in coastal salt grass meadows (1.11 ± 0.16 birds · ha-1) and lowest densities occur on dwarf shrub mat tundra (0.04 ± 0.04 birds · ha-1). Breeding densities in mixed graminoid and dwarf shrub meadows decline significantly with distance from the coast, decreasing abruptly from 0.75 ± 0.11 birds · ha-1 within the first two km to 0.09 ± 0.03 birds · ha-1 farther inland. Although salt grass meadows constitute only 5% of the coastal lowlands, they support 25% of the population.

The Wilson Bulletin↗
USGS1994

Chick movements and adoption in a colony of Black-Legged Kittiwakes

We studied Black-legged Kittiwakes ( Rissa tridactyla ) in an Alaskan colony where movement of young among nests was possible because of moderate terrain and close nest spacing. Thirty-three percent of chicks in a focal group departed their nests prior to fledging, and seven of the vagrant chicks (58%) were adopted by foster parents. The overall frequency of adoption in three years was 8% of 88 chicks from 57 focal nests. Premature nest-departure occurred at different stages among first- and second-hatched chicks. Departing second-hatched chicks were usually expelled by their nest mates within a few days after hatching. First-hatched chicks left at all stages and usually were the sole nest occupant when they departed. The evidence for parent-offspring recognition was equivocal. Adults accepted alien chicks that appeared in the nest and also occasionally attacked their own young outside the nest. However, asymmetry in the response of parents and nonparents to vagrant chicks seeking access to a nest suggested that adults were often able to discriminate appropriately. Vagrant chicks appeared to have little control over their fate-most entered nests where they were smaller than the resident young and suffered nest-mate aggression. Reproductive error seems the likely explanation for the acceptance and foster caregiving observed in adult kittiwakes.

Alaska↗
USGS1994

Dynamics of ovarian follicles in breeding ducks

I quantified ovarian rapid follicle growth (RFG) and regression of postovulatory follicles of Northern Pintails ( Anas acuta ), American Wigeon ( A. americana ), and Lesser Scaup ( Aythya affinis ) by a method that accounted for within-day variation in follicle size. Objective methods for identifying onset of RFG also are presented; this is crucial for accurate classification of breeding status. Duration of RFG was estimated as 4.2, 5.1, and 5.0 days for pintails, wigeon, and scaup, respectively; these are shorter than previously reported. Diameters of follicles at the beginning of RFG were estimated to be 8.2, 6.9, and 7.9 mm for pintails, wigeon, and scaup, respectively. For all species, RFG was linear, using follicle diameters, and exponential, using dry masses. Models of RFG and postovulatory follicle regression have practical value for calculating nest initiation dates, number of developing follicles, clutch size, renesting intervals, and daily energy and nutrient commitment to reproduction of collected breeding females.

Alaska↗
USGS1994

Morphological and genetic divergence among Alaskan populations of Brachyramphus murrelets

We studied morphological and mitochondrial DNA (mtDNA) divergence among three populations of Brachyramphus Murrelets: Kittlitz's Murrelets ( B. brevirostris ), and tree-nesting and ground-nesting Marbled Murrelets ( B. marmoratus ). We found little morphological divergence in external and skeletal measurements among Marbled Murrelets, but both populations were easily distinguished from Kittlitz's Murrelets. Principal components analysis (PCA) of external measurements showed that Kittlitz's Murrelets occupied a distinct cloud in multivariate space separate from Marbled Murrelets. However, tree-nesting and ground-nesting Marbled Murrelets were indistinguishable. We obtained the same pattern from PCA of skeletal dimensions. Analysis of mtDNA revealed an estimate of sequence divergence of 4.4%-5.0% between Marbled Murrelets and Kittlitz's Murrelets, suggesting a divergence of about 2.2 MYBP. The difference between ground- and tree-nesting murrelets was 0.03%. This analysis suggests little divergence has occurred between tree- and ground-nesting populations of Marbled Murrelets.

Alaska↗
USGS1999

Juvenile Marbled Murrelet nurseries and the productivity index

Late summer counts of juveniles at sea are used as an index of Marbled Murrelet ( Brachyramphus marmoratus ) reproductive success, but little is known about juvenile dispersal or habitat use. Further, it is not known whether these counts accurately reflect absolute breeding success. To address these questions we conducted five boat surveys for Marbled Murrelets and Pigeon Guillemots ( Cepphus columba ) in Kachemak Bay, Alaska between 7-24 August 1996. Juvenile murrelet distribution in the bay was patchy, and we identified a juvenile Marbled Murrelet 'nursery' area in the outer bay. Fifty-three of 61 juvenile murrelets were in this area, whereas after-hatch-year (AHY) murrelets were dispersed throughout the bay, as were juvenile and AHY Pigeon Guillemots. The murrelet nursery was characterized by water inside of or at the edge of a 20 m deep contour, semi-protected seas, productive waters, and a large bed of Nereocystis kelp. Juveniles comprised 16.1% of all murrelets and 24.8% of all guillemots observed at sea. These data suggest a maximum reproductive success of 0.32 chicks/pair if all AHY murrelets were breeding and 0.46 chicks/pair if only 70% of AHY murrelets were breeding. For guillemots, maximum productivity estimated from at-sea counts was 0.50 chicks/pair if all AHY were breeding and 0.71 chicks/pair if only 70% were breeding. The guillemot estimate was similar to that obtained by concurrent studies at nine guillemot colonies in the bay (0.56 chicks/pair). These results suggest that at sea surveys in late summer provide a reasonable index of local productivity for nearshore alcids. Further, if murrelet nursery areas can be found, at sea counts may provide a valid measure of absolute productivity.

Alaska↗
USGS1991

Variable first prebasic molt in Rio Grande and Merriam's wild turkeys

Gallinaceous birds typically retain the juvenal ninth (JIX) and tenth (JX) primary wing feathers during the first prebasic molt (Petrides 1945, terminology follows Humphrey and Parkes 1959). However, not all Wild Turkeys ( Meleagris gallopavo ) retain JIX and JX during this molt. Some retain only JX (reviewed by Lewis 1967), and in 21% of 125 Florida Wild Turkeys ( M. g. osceola ), all 10 juvenal primaries were molted (Williams and Austin 1970, 1988). Leopold (1943) suggested that Wild Turkeys were genetically predisposed to retain both JIX and JX, whereas domestic turkeys retained only JX. He further suggested that the frequency of this extended primary molt indicated the degree of cross-breeding between wild and domestic turkeys. Stable frequencies could be maintained if this molting characteristic had neutral selective value. Alternatively, Williams and Austin (1988) hypothesized that the first prebasic molt among wild birds varied in a genetically controlled manner along a north-south gradient related to climate. They predicted that more northerly populations would exhibit progressively higher frequencies of retention of both JIX and JX.

The Wilson Bulletin↗
USGS1989

Nest habitat use of Rio Grande wild turkeys

Nest habitat use of Rio Grande Wild Turkeys ( Meleagris gallopavo intermedia ) was studied along the South Platte River in northeast Colorado in 1986-87. Thirty-three of 35 nests were in riparian habitats. Nests were either in western snowberry ( Symphoricarpos occidentalis ) (67%) or mixed forbs and grasses (33%). Early season nests were more likely to be in snowberry than late season nests. Nest sites were characterized by greater overstory canopy cover, more shrubs, fewer grasses, and greater understory cover and height than surrounding areas. These areas had more shrubs, fewer large trees, and greater understory cover and height than riparian habitats throughout the study area. Phenology of understory vegetation and the effect of such vegetation on nest predation may influence temporal patterns of nest habitat use.

The Wilson Bulletin↗
USGS1996

Food availability and feeding preferences of breeding fulvous whistling-ducks in Louisiana ricefields

Expansion of the breeding distribution of the Fulvous whistling-duck ( Dendrocygna bicolor ) into the southeastern United States after the mid-1800s coincided with the establishment of rice ( Oryza sativa) cultures in Texas, Louisiana, and Florida. In southern Louisiana, where approximately 80% of rice is aerially seeded in water, Fulvous whistling-ducks are suspected of feeding extensively on planted rice and are considered a nuisance. To determine the extent of rice utilization by ducks nesting in southwestern Louisiana, we estimated food availability in ricefields and assessed feeding preferences. We also examined effects of sex and stage of reproduction on food selection. Feeding sites in Louisiana ricefields that were tilled and flooded in preparation for spring planting, contained abundant foods (mean ± SE = 109.0 ± 18.0 g/m2, especially seeds of moist soil plants such as signalgrass ( Brachiaria extensa ), beakrush ( Rhynchospora sp.), and flatsedge ( Cyperus iria ). Diets of males and females were similar (P = 0.080), but varied through the reproductive cycle (P = 0.008). Consumption of plant material was slightly reduced during the period of rapid ovarian follicle growth in females; however, ingestion of animal foods never exceeded 4%. Fulvous whistling-ducks exhibited feeding preferences (P < 0.001) with aquatic earthworms (Oligochaeta) and wild millet seeds ( Echinochloa sp.) being preferred over other food taxa. Rice made up <4% of the diet and was selected in proportion to its availability before and during period of rapid follicle development. Almost 25% of the diet of incubating females consisted of rice; however, we concluded that crop depredation by Fulvous whistling-ducks (≤0.1%) was of minor importance relative to other potential sources of crop loss. Indeed, use of ricefields by whistling-ducks may actually benefit farmers if ingestion of seeds of undesirable plants reduces the need for costly herbicide treatments.

Louisiana↗
USGS1990

Diurnal time-activity budgets of wintering canvasbacks in Louisiana

We determined diurnal time-activity budgets of Canvasbacks ( Aythya valisineria ) at Catahoula Lake and at the Mississippi River Delta, Louisiana, from December 1987 to March 1988. Canvasback feeding, resting, locomotory, and comfort activities varied by month and location with a month-location interaction. Moreover, the percentage of time spent feeding varied by sex with a month-sex interaction. Study site differences in the time- activity budgets of wintering Canvasbacks may be related to characteristics of their foods, foraging mode, disturbance level, and physical features of habitats at the two study sites. Canvasbacks wintering in Louisiana generally spent less time feeding and more time resting during the day than they did in Mississippi or coastal South Carolina. Levels of agonistic behavior were lower than those observed in South Carolina. We found no evidence of male dominance of female Canvasbacks in Louisiana.

Louisiana↗