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At least 325 records · Page 18Linked to original sources
USGS1999

Nest-site selection in the acorn woodpecker

Acorn Woodpeckers ( Melanerpes formicivorus ) at Hastings Reservation in central California prefer to nest in dead limbs in large, dead valley oaks ( Quercus lobata ) and California sycamores ( Platanus racemosa ) that are also frequently used as acorn storage trees. Based on 232 nest cavities used over an 18-year period, we tested whether preferred or modal nest-site characters were associated with increased reproductive success (the "nest-site quality" hypothesis). We also examined whether more successful nests were likely to experience more favorable microclimatic conditions or to be less accessible to terrestrial predators. We found only equivocal support for the nest-site quality hypothesis: only 1 of 5 preferred characters and 2 of 10 characters exhibiting a clear modality were correlated with higher reproductive success. All three characteristics of nests known or likely to be associated with a more favorable microclimate, and two of five characteristics likely to render nests less accessible to predators, were correlated with higher reproductive success. These results suggest that nest cavities in this population are built in part to take advantage of favorable microclimatic conditions and, to a lesser extent, to reduce access to predators. However, despite benefits of particular nest characteristics, birds frequently nested in apparently suboptimal cavities. We also found a significant relationship between mean group size and the history of occupancy of particular territories and the probability of nest cavities being built in microclimatically favorable live limbs, suggesting that larger groups residing on more stable territories were better able to construct nests with optimal characteristics. This indicates that there may be demographic, as well as ecological, constraints on nest-site selection in this primary cavity nester.

The Auk↗
USGS1998

Modeling colony site dynamics: A case study of gull-billed terns ( Sterna nilotica ) in coastal Virginia

We developed a Markov process model for colony-site dynamics of Gull-billed Terns ( Sterna nilotica ). From 1993 through 1996, we monitored breeding numbers of Gull-billed Terns and their frequent colony associates, Common Terns ( Sterna hirundo ) and Black Skimmers ( Rynchops niger ), at colony sites along 80 km of the barrier island region of coastal Virginia. We also monitored flooding events and renesting. We developed the model for colony survival, extinction, and recolonization at potential colony sites over the four-year period. We then used data on annual site occupation by Gull-billed Terns to estimate model parameters and tested for differences between nesting substrates (barrier island vs. shellpile). Results revealed a dynamic system but provided no evidence that the dynamics were Markovian, i.e. the probability that a site was occupied in one year was not influenced by whether it had been occupied in the previous year. Nor did colony-level reproductive success the previous season seem to affect the probability of site occupancy. Site survival and recolonization rates were similar, and the estimated overall annual probability of a site being occupied was 0.59. Of the 25 sites that were used during the four-year period, 16 were used in one or two years only, and only three were used in all four years. Flooding and renesting were frequent in both habitat types in all years. The frequent flooding of nests on shellpiles argues for more effective management; augmentation with shell and sand to increase elevations as little as 20 cm could have reduced flooding at a number of sites. The low colonysite fidelity that we observed suggests that an effective management approach would be to provide a large number of sand and/or shellpile sites for use by nesting terns. Sites not used in one year may still be used in subsequent years.

The Auk↗
USGS1998

Genetic differentiation between wintering populations of lesser snow geese nesting on Wrangel Island, Russia

Arctic breeding populations of Lesser Snow Geese ( Chen c. caerulescens ) range from Baffin Island in eastern Canada to Wrangel Island, Russia, which is located 650 km west of Alaska (Bellrose 1980). Although hundreds of thousands of Lesser Snow Geese may have occupied the Russian arctic in the mid1800s (see Takekawa et al., 1994), the Wrangel Island birds constitute the only remnant colony on the Asian continent (Syroechkovsky and Litvin 1986) and may represent a matriarchal population for the species (Quinn 1992). In the past 30 years, the Wrangel Island colony has declined from more than 200,000 to less than 75,000 breeding adults (Pacific Flyway Technical Subcommittee 1992, V. Baranyuk unpubl. data), which has resulted in increasing concern about its conservation and management. The Wrangel Island colony consists of two wintering populations that migrate to different regions and are faithful to their wintering areas (McKelvey et al. 1989). The larger northern population (about 60% of the total from Wrangel) migrates to the Fraser River delta of British Columbia and the Skagit River delta of northern Washington, whereas the southern population flies 600 km farther south to the Central Valley of California (Rienecker 1965, Teplov and Shev. aryova 1965, Jeffrey and Kaiser 1979, Priklonsky and Sapetin 1979). The northern population is isolated from other Lesser Snow Geese during the winter, but the southern population mixes with geese from Banks Island, Canada and from the smaller Anderson and Sagaviriniktok River deltas (Dzubin 1974, Johnson 1995, Syroechkovsky et al. 1994).

The Auk↗
USGS1999

A model to predict breeding-season productivity for multibrooded songbirds

Breeding-season productivity (the per capita number of offspring surviving to the end of the breeding season) is seldom estimated for multibrooded songbirds because of cost and logistical constraints. However, this parameter is critical for predictions of population growth rates and comparisons of seasonal productivity across geographic or temporal scales. We constructed a dynamic, stochastic, individual-based model of breeding-season productivity using demographic data from Wood Thrushes ( Hylocichla mustelina ) in central Georgia from 1993 to 1996. The model predicts breeding-season productivity as a function of adult survival, juvenile survival, nesting success, season length, renesting interval, and juvenile-care intervals. The model predicted that seasonal fecundity (number of fledglings produced) was 3.04, but only 2.04 juveniles per female survived to the end of the breeding season. Sensitivity analyses showed that differences in renesting interval, nesting success, fledglings per successful nest, and adult and juvenile survival caused variation in breeding-season productivity. Contrary to commonly held notions, season length and fledgling-care interval length did not cause variation in breeding-season productivity. This modeling exercise emphasizes the need for demographic data for songbird species, and we encourage biologists to use similar models to evaluate productivity in songbird populations.

The Auk↗
USGS1999

At-sea distribution of Spectacled Eiders: A 120-year-old mystery resolved

The at-sea distribution of the threatened Spectacled Eider ( Somateria fischeri ) has remained largely undocumented. We identified migration corridors, staging and molting areas, and wintering areas of adult Spectacled Eiders using implanted satellite-transmitters in birds from each of the three extant breeding grounds (North Slope and Yukon-Kuskokwim Delta in Alaska and arctic Russia). Based on transmitter locations, we conducted aerial surveys to provide visual confirmation of eider flocks and to estimate numbers of birds. We identified two principal molting and staging areas off coastal Alaska (Ledyard Bay and eastern Norton Sound) and two off coastal Russia (Mechigmenskiy Bay on the eastern Chukotka Peninsula, and the area between the Indigirka and Kolyma deltas in the Republic of Sakha). We estimated that >10,000 birds molt and stage in monospecific flocks at Mechigmenskiy and Ledyard bays, and several thousand molt and stage in eastern Norton Sound. We further identified eastern Norton Sound as the principal molting and staging area for females nesting on the Yukon-Kuskokwim Delta, and Ledyard Bay and Mechigmenskiy Bay as the principal molting and staging areas for females nesting on the North Slope. Males marked at all three breeding grounds molt and stage in Mechigmenskiy Bay, Ledyard Bay, and the Indigirka-Kolyma delta region. Males from the Yukon-Kuskokwim Delta molt and stage mainly at Mechigmenskiy Bay. Equal numbers of males from the North Slope molt and stage at all three areas, and most males from arctic Russia molt and stage at the Indigirka-Kolyma delta region. Postbreeding migration corridors were offshore in the Bering, Chukchi, and Beaufort seas. In winter, eiders were in the Bering Sea south of St. Lawrence Island. Our estimates from surveys in late winter and early spring suggest that at least 333,000 birds winter in single-species flocks in the pack ice in the Bering Sea.

Alaska↗
USGS1999

Precocious breeding by yearling Giant Canada Geese

Many species of waterfowl are capable of breeding as yearlings. In the subfamily Anserinae, however, reproduction normally does not commence until individuals reach two to four years of age (Rohwer 1992). Most published accounts indicate that Canada Geese ( Branta canadensis ) conform to the pattern typically found in other geese, deferring reproduction as yearlings and initiating breeding when birds are two years of age or older (Hanson 1962, Brakhage 1965, Bellrose 1980, Moser and Rusch 1989). The few documented exceptions (Brakhage 1965, Cooper 1978, MacInnes and Dunn 1988) suggest that the likelihood of a successful breeding attempt is higher for yearling males than females and that when early breeding occurs, one member of the pair is often at least two years old. Only two records of nesting attempts by yearling female Canada Geese have been published (Hall and McGilvrey 1971, Mickelson, 1975). In each case, the female produced some fertile eggs but deserted the nest before the eggs hatched. The observations noted above demonstrate that reproduction by yearling Canada Geese is physiolog ically possible for both sexes, but they also raise a number of interesting questions regarding why most individuals defer breeding during their first year. Energetic or nutritional constraints, and the inability of yearlings to secure and successfully defend a territory, are likely physiological (Elder 1946) and social (Brakhage 1965) impediments to early breeding From an evolutionary perspective, reduced reproductive success of yearlings relative to adults, and increased mortality associated with early breeding. also may contribute to deferred sexual maturity in waterfowl (Rohwer 1992).

The Auk↗
USGS1999

Evaluation of mist-net sampling as an index to productivity in Kirtland's Warblers

Many applied and theoretical investigations require information on how productivity varies in time and space (Temple and Wiens 1989. DeSante 1995). Examples include studies of habitat quality, population trends, life-history tactics, and metapopulation dynamics. From a demographic perspective, productivity is the number of young counted at a given time of year, produced per adult (e.g. Caswell 1989). Various measures have been used to estimate productivity. One of the most attractive is mist netting during the summer after young have left the nest, but ideally before they have left the study area. Several programs use this approach, including the Constant Effort Sites Scheme of the British Trust for Ornithology (Baillie et al. 1986, Bibby et al. 1992) and the Monitoring Avian Productivity and Survivorship (MAPS) program (DeSante et al. 1993) in North America. Hatching-year (HY) and after-hatching-year (AHY) birds are widely believed to have different susceptibilities to netting (DeSante et al. 1995, Peach et al. 1996), so the ratio of HY's to AHY's obtained from netting is not used as an estimate of productivity. Instead, investigators hope that the relative susceptibility to capture is about the same among the samples being compared so that the age ratios in mistnet samples provide a reliable index to productivity (DeSante 1995, DeSante et al. 1995).

The Auk↗
USGS1979

Estimating nest success: The Mayfield method and an alternative

Mayfield's method for calculating the success of a group of nests is examined in detail. The standard error of his estimator is developed. Mayfield's assumption that destroyed nests are at risk until the midpoint of the interval between visits leads to bias if nests are visited infrequently. A remedy is suggested, the Mayfield-40% method. I also present a competing model, which recognizes that the actual destruction date of a failed nest is unknown. Estimated daily mortality rates and standard errors are developed under this model. A comparison of the original Mayfield method, the Mayfield-40% method, and the new method, which incorporates an unknown date of destruction, shows that the original or modified Mayfield method performs nearly as well as the more appropriate method and requires far easier calculations. A technique for statistically comparing daily mortality rates is offered; the one proposed by Dow (1978) is claimed to be misleading. Finally, I give a method for detecting heterogeneity among nests and an improved estimator, if it is found.

The Auk↗
USGS1974

Social behavior of breeding gadwalls in North Dakota

Responses of duck pairs encountering other ducks were categorized by McKinney (1965a) as displays, attack, escape and avoidance, sexual pursuit, and sociability. Gadwalls ( Anas strepera ) show all these responses on the breeding grounds, and characteristic behavior patterns occur depending on the reproductive state of the birds involved. The responses of paired ducks to unpaired males on the breeding grounds have not been described for the Gadwall or any other species. The function of aerial flights (McKinney 1965a) is also confused in the literature. The objectives of this paper are to describe the responses of paired breeding Gadwalls to other Gadwall pairs and unmated drakes and to dis- cuss the possible reasons for the type of spacing behavior Gadwall pairs exhibit.

The Auk↗
USGS1981

The role of nutrient reserves in mallard reproduction

Mallard ( Anas platyrhynchos ) populations breeding in temperate North America obtain a significant part of the energy and lipid requirements of reproduction at sites occupied prior to arrival on the breeding grounds. Protein for egg formation, however, is obtained principally from the diet during the nesting period. Both sexes arrive heavy and fat in North Dakota but experience substantial weight loss and lipid depletion during the nesting cycle. Weight loss is most pronounced among females and averages 25% from prelaying to late incubation. Body weights of both sexes are positively correlated with carcass lipid content. The paired male draws upon lipids early in the nesting season when an activity center is being established and defended and when females are preparing to nest. The female's lipid reserves are utilized primarily during laying and early incubation. The significance of lipid reserves diminishes as the nesting season progresses, and females do not acquire substantial lipid stores prior to renesting when the initial clutch is destroyed. The magnitude of lipid reserves carried in female carcasses is positively correlated with clutch size from mid-April to early June. Protein transfer for egg formation from flight and leg muscle and body organs can account for only a small part of the protein requirement for the clutch. By utilizing lipid reserves to meet energy requirements, the female can acquire sufficient protein from the diet to produce a large initial clutch even when foods are relatively scarce, whereas the renesting female must rely entirely upon food resources available at the breeding site for its nutrient and energy requirements.

The Auk↗
USGS1978

Feeding habitat use by colonially-breeding herons, egrets, and ibises in North Carolina

Nine species of herons, egrets, and ibises were followed by airplane from a nesting colony near Beaufort, North Carolina to their feeding sites. Except for Cattle Egrets, which flew exclusively to fields and dumps, the birds flew mainly to saltmarsh habitat. The selection of feeding habitats by Great Egrets and Louisiana Herons was directly related to tidal depth. The Great Egret was the only species that effectively used eelgrass beds, and its use of this habitat was restricted to between 1.5 h before and after low tide. We suspect that shorter-legged herons did not use eelgrass regularly because the water was too deep. Most Great Egrets, White Ibises, Louisiana Herons, and Snowy Egrets used areas near the colony (<4 km). Great Egrets, Black-crowned Night Herons, and White Ibises flew farther from the colony at high than at low tide. Great Egrets traveled farther from the colony when they used thermals; rate of travel to feeding sites was the same, however, whether or not they used thermals. Aggressive encounters were observed at the landing sites of Great Egrets, Louisiana Herons, Snowy Egrets, and Black-crowned Night Herons. In contrast to the other species studied, Cattle Egrets and White Ibises often flew in groups to feeding sites. Indirect evidence supports the hypothesis that colonies can act as "information centres," wherein unsuccessful birds follow successful ones to better feeding locations.

North Carolina↗
USGS1973

Snowy owl predation on lapland longspur nestlings recorded on film

During the summer of 1971 I investigated the breeding biology of the Lapland Longspur, Calcarius lapponicus , near Barrow, Alaska. To obtain data on incubation and feeding patterns of nesting longspurs, time-lapse cameras (Minolta Autopak-8 D6 super-8 movie cameras equipped with an Intervalometer-P time-lapse device) were positioned at several nests throughout the nesting season with an exposure interval of either 8 or 30 seconds. At 07:00 on 14 July a Snowy Owl, Nyctea scandiaca , took the three largest of four young at a nest being monitored at 30-second intervals (Figure 1). The nestlings were 4, 6, 7, and 8 days posthatching and weighed approximately 12, 15, 20, and 20 g respectively on 13 July.

The Auk↗
USGS1977

The display flight of The North American Ruddy Duck

Sexual behavior of the North American Ruddy Duck ( Oxyura jamaicensis ), as summarized by Johnsgard (1965: 323-327), includes a display variously referred to as the ringing rush (Johnsgard 1965: 325; 1967), ring rush (Johnsgard 1966), and/or display flight (Johnsgard 1966, 1967), which males perform as a short rush across the water surface, generally toward females. Differences of opinion exist concerning the description of the sound emitted during the display and the exact mechanics of sound production. Bailey (1919) described "a noise suggesting castanets" accompanying what probably was the display flight. Johnsgard described the noise as ringing (1965: 325) and rattling (1967). Buzzing has been used to characterize the sound produced during the display flight of the Australian Blue-billed Duck ( O. australis ), a display "which appears to correspond exactly" to the ring rush of O. jamaicensis (Johnsgard 1966). We prefer to describe the sound as popping. Wetmore (1920: 247), without naming the display, described "a great boiling in the water with wings and feet." Johnsgard attributed the noise to the wings alone (1965: 325) and, later "wings and/or feet striking the water" (1967), while Palmer (1975: 513) assigned the sound to the feet.

The Auk↗
USGS1995

[Book review] Skua and penguin: Predator and prey

The skua and penguin with title billing in this book are specifically the South Polar Skua ( Catharacta maccormicki ) and the Adélie Penguin ( Pygoscelis adeliae ), More specifically, they are the populations of those two species that breed at Cape Bird on Ross Island, Antarctica (77°14'S, 16628'E), where the author and his students and colleagues conducted research during 1965-1970, Young presents the results of that research (with apologies for the long delay), using later research conducted by others on these species to help evaluate and interpret the findings from his program,

The Auk↗
USGS1984

[Book review] The wildfowl of Britain and Europe

Of about 140 extant species of waterfowl in the world, 54 occur in the western Pale- arctic. In this, his most recent book, Ogilvie introduces the reader to the waterfowl of Europe including occasional visitors and introduced species. Although written primarily for laymen, ornithologists will find the book informative but should not expect a major treatise on European waterfowl. The text is drawn primarily from Volume I of "The hand-book of the birds of Europe, North Africa, and the Middle East: the birds of the Western Palearctic," of which the author was an editor.

The Auk↗
USGS1978

Observations and reinterpretation of kingfisher-raptor interactions

Reported observations of Belted Kingfisher ( Megaceryle alcyon )-raptor interactions have ranged from brief encounters where the kingfisher escaped the raptor and the hawk subsequently flew away to repeated chases (Johnson 1925, McCabe and McCabe 1928, Skinner 1928, Smith 1963). In some repetitive chases, kingfishers appeared to initiate the interaction (McCabe and McCabe 1928, Skinner 1928).

The Auk↗
USGS1973

The California condor in the Pacific Northwest

The California Condor ( Gymnogyps californianus ), once found along the Pacific Coast from Baja California to British Columbia, had become very rare north of California by 1850. Koford (1953), summarizing information available on the species in the Pacific Northwest, tentatively concluded that birds seen in that area were wanderers from California, perhaps forced north in some years by food shortages. As support for his theory he noted that there were no records of fossil condors in this northern region, known occurrences there were all in winter, and only a few individuals seemed to be present at any one time. Recently information has come to light that suggests the Pacific Northwest condors were permanent residents with a long history there. An Indian midden on the Columbia River near The Dalles, Oregon, has yielded a considerable number of California Condor bones, dating back thousands of years (Miller, 1957). A more recent, but still precaucasian condor bone was found in another midden in southwestern Oregon (Miller, 1942). These finds indicate the condors are not recent invaders from California.

The Auk↗