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USGS1980

A necropsy procedure for sampling disease in wild birds

This paper presents a necropsy procedure for examining small wild birds, designed to be used by investigators without experience in avian pathology. It gives instructions on how to conduct a postmortem examination, lists the needed equipment, tells what parts of a bird to save when a disorder in encountered, and lists possible diseases which each may signify. This procedure would enable ornithologists to include parasites and diseases in their investigations of avian populations.

Condor↗

USGS1987

Latent population responses of summer birds to a catastrophic, climatological event

Catastrophic events can create ecological crunches for avian populations. Ornithologists generally assume that such events elicit immediate, dramatic declines in populations followed by rapid recolonization of a site with habitat recovery. Despite total inundation of habitats within the South Platte floodplain of eastern Colorado during the 1983 breeding season, populations of Brown Thrashers (Toxostoma rufum) and Rufoussided Towhees (Pipilo erythrophthalmus) did not decline significantly from 1982 densities. However, populations of both species declined significantly in 1984 and towhee populations remained low in 1985. These observations support speculations from recent studies of shrubsteppe bird populations that site tenacity may play a stronger role in determining annual densities of breeding birds than previously realized.

The Condor↗

USGS1989

Responses to human intruders by birds nesting in colonies: Experimental results and management guidelines

Colonies of nesting wading birds and seabirds were studied at coastal sites in Virginia and North Carolina to determine distances at which birds flushed in response to human intrusion. There were few statistically significant relationships between flushing distances and colony size. Similarly, there were few differences between responses during incubation compared to post-hatching periods.

Colonial Waterbirds↗

USGS1995

Pasteurella multocida isolated from wild birds of North America: a serotype and DNA fingerprint study of isolates from 1978 to 1993

Serotype and DNA fingerprint methods were used to study Pasteurella multocida isolated from 320 wild birds of North America. Isolates were collected during 1978-93. The HhaI profiles of 314 isolates matched the HhaI profile of somatic reference type 1, strain X-73; somatic type 1 antigen was expressed by 310 isolates, and the serotype of four isolates was undetected. Differentiation of the 314 isolates was observed by digestion of DNA with HpaII. None of the HpaII profiles matched the HpaII profile of X-73 (designated HhaI 001/HpaII 001). Three HpaII profiles were recognized among the somatic type 1 isolates: HpaII 002 (n = 18), HpaII 003 (n = 122), and HpaII 004 (n = 174). Profile HpaII 002 was found among isolates collected during 1979-83. Profile HpaII 003 was identified from isolates collected during 1979-89, with the exception of two isolates in 1992. The HpaII 004 profile was identified from isolates collected during 1983-93. Of the six remaining isolates, four expressed somatic type 4 and had HhaI profiles identical to the somatic type 4 reference strain P-1662 profile (designated HhaI 004); these isolates were differentiated by digestion of DNA with HpaII. One isolate was identified as serotype F:11, and another was serotype A:3,4. In the present study, 314 of 316 (99.4%) isolates from wild birds in the Central, Mississippi, and Pacific flyways during 1978-93, were P. multocida somatic type 1.

Avian Diseases↗

USGS1983

Nutritional value of the aril of Trichilia cuneata, a bird-dispersed fruit

Fruits of Trichilia cuneata (Meliaceae), a common tree in drier forests of Central America, are eaten by a number of birds. The fruits are 10 to 12 mm in diameter, covered by a yellowish-brown, capsular exocarp, and contain three to six seeds distributed among three locules. Each seed is covered by an orangish-red aril that averages 59.7 percent lipid and 15 1 percent protein, which makes this species one of the most nutritious known. The fleshy tissue of only 15 of 59 other species for which we found data contained at least 10 percent protein (dry wt.). Only nine species of 57 had fleshy tissue containing more than 40 percent lipid (dry wt.). Between 1971 and 1972, weights of whole fruits decreased by 36 percent, perhaps in response to a severe drought in the area. The decrease was not equally distributed among component tissues of the fruit. Exocarp decreased by 36 percent, aril by 4 percent, and seeds by 62 percent. However, the reduction in weight per seed was not so dramatic, for two reasons. First, the number of seeds per fruit decreased by 26 percent. Secondly, many seeds did not develop. Thus, the decrease in weight per normally developed seed was only 18 percent. The fruit of Trichilia cuneata was attractive to both specialized (4 species) and opportunistic (11 species) frugivorous birds and is intermediate ("a generalist") in several dispersal-related characteristics.

Biotropica↗

USGS1941

Blood parasites of birds of the District of Columbia and Patuxent Research Refuge vicinity

Recently a number of surveys of blood parasites of birds have been made in different parts of this country by different workers, the general purpose of which was to further the knowledge of the distribution and pathogenicity of these protozoa. This paper treats the distribution of parasites found in sampling miscellaneous birds of the District of Columbia and vicinity and contains a preliminary report on the more important phase of the problem of pathogenicity.

Maryland↗

USGS1983

Populations and habitat use of marine birds in the Semidi Islands, Alaska

About one-quarter of the resident seabirds in the Gulf of Alaska breed on the Semidi Islands. In terms of biomass, the proportion is closer to one-third. The most abundant birds are Common and Thick-billed Murres, with a combined population exceeding 1 million birds. Hundreds of thousands of Horned Puffins breed in burrows on two islands. Other species numbering more than 100,000 individuals include the Northern Fulmar, Fork-tailed and Leach's Storm-Petrels, and possibly also the Black-legged Kittiwake and Tufted Puffin. Both species of storm-petrels commonly nest in side chambers of puffin burrows. Parasitic Jaegers nest in a loose colony on Chowiet Island. This behavior has not been reported elsewhere in the Gulf of Alaska. Red-faced and Pelagic Cormorants commonly change breeding colony location from year to year. The Semidi Islands are the easternmost breeding site for Least Auklets.

Alaska↗

USGS1985

An evaluation of condition indices for birds

A Lipid Index, the ratio of fat to fat-free dry weight, is proposed as a measure of fat stores in birds. The estimation of the index from field measurements of live birds is illustrated with data on the sandhill crane ( Grus canadensis) and greater white-fronted goose ( Anser albifrons ). Of the various methods of assessing fat stores, lipid extraction is the most accurate but also the most involved. Water extraction is a simpler laboratory method that provides a good index to fat and can be calibrated to serve as an estimator. Body weight itself is often inadequate as a condition index, but scaling by morphological measurements can markedly improve its value.

Journal of Wildlife Management↗

USGS1943

A comparative study of the breeding bird population of Shenandoah Mountains, Virginia

WHILE working on habitat studies of the Ruffed Grouse ( Bonasa umbellus ) in the George Washington National Forest during the late spring and early summer of 1941, the author found it possible to carry out a supplemental study on the relative abundance of the breeding birds of the area. Since considerable time was spent in traversing certain sections of the forest in search of Ruffed Grouse broods, an unusual opportunity was afforded to make a general comparative census of the species of birds found therein.

The Auk↗

USGS1947

Recent observations on Maryland birds

In the course of working on a study of the 'Geographical and Ecological Distribution of the Birds of Maryland,' a considerable number of records of occurrence have been obtained, which have helped to clarify the status of many Maryland birds. Some of these records are new for the state and many serve to extend the known breeding or wintering ranges within Maryland. Others will serve as additional information on the seasonal and geographical distribution of certain species whose ranges are imperfectly known.

The Auk↗

USGS1996

First-time observer effects in the North American Breeding Bird Survey

Currently the operational analysis of Breeding Bird Survey (BBS) data by the National Biological Service accounts for observer differences in estimating the trend for each route, but within-observer differences are not modeled. We tested for the existence of a form of within-observer differences in skill level, namely a change in ability to count birds of a given species after an observer's first year on a given route. An increase in ability could positively bias the trend estimate. Removal of an observer's first year of observation on each route for the period 1966 to 1991 resulted in lower average unweighted trend estimates for 415 of 459 species (90%). These reductions were statistically significant for 213 species (46%). The average reduction in trend was 1.8% change per year (SD = 5.4%). In route-regression analysis, route data are weighted by a measure of precision. Removing first-year observer counts reduced the weighted trend estimate for 275 of 416 species (66%), but differences generally were small.

The Auk↗

USGS1985

Problems in estimating age-specific survival rates from recovery data of birds ringed as young

(1) The life table model is frequently employed in the analysis of ringer samples of young in bird populations. The basic model is biologically unrealistic and of little use in making inferences concerning age-specific survival probabilities. (2) This model rests on a number of restrictive assumptions, the failure of which causes serious biases. Several important assumptions are not met with real data and the estimators of age-specific survival are not robust enough to these failures. (3) Five major problems in the use of the life table method are reviewed. Examples are provided to illustrate several of the problems involved in using this method in making inferences about survival rates and its age-specific nature. (4) We conclude that this is an invalid procedure and it should not be used. Furthermore, ringing studies involving only young birds are pointless as regards survival estimation because no valid method exists for estimating age-specific or time-specific survival rates from such data. (5) In our view, inferences about age-specific survival rates are possible only if both young and adult (or young, subadult and adult) age classes are ringed each year for k years ( k ≥ 2).

Journal of Animal Ecology↗

USGS2024

Comments on the species limits of certain North American birds, part 1

Although species limits of North American birds are relatively well-delineated, discrepancies among global lists identify species complexes that are subject to differences of opinion. As part of our work with the North American Classification Committee (NACC) of the American Ornithological Society, we here assess species limits in 11 such species complexes of North American birds: Spruce Grouse (Canachites canadensis), Band-tailed Pigeon (Patagioenas fasciata), Antillean Mango (Anthracothorax dominicus), Greenish Puffleg (Haplophaedia aureliae), Black Oystercatcher (Haematopus bachmani), Hook-billed Kite (Chondrohierax uncinatus), Sharp-shinned Hawk (Accipiter striatus), Elegant Trogon (Trogon elegans), American Three-toed Woodpecker (Picoides dorsalis), Golden-olive Woodpecker (Colaptes rubiginosus), and Olive-throated Parakeet (Eupsittula nana). We provide updated information on the taxonomic history of these species, and recommend updated taxonomic treatments by using published works, analysis of museum specimens, and citizen/community science databases. We hope this work will provide a foundation for future taxonomic research in these species complexes.

Bulletin of the British Ornithologists' Club↗

USGS2012

Role of bird movements in the epidemiology of West Nile and avian influenza virus

Avian influenza virus (AIV) is influenced by site fidelity and movements of bird hosts. We examined the movement ecology of American crows ( Corvus brachyrhynchos ) as potential hosts for West Nile virus (WNV) and greater white-fronted geese ( Anser albifrons frontalis ) as potential hosts for AIVs. Research was based on radio-telemetry studies conducted in the Central Valley of California, USA. While crows were restricted to a small area of only a few square kilometers, the distribution of the geese encompassed the northern Central Valley. The crows used 1.5 to 3.5 different roosting areas monthly from February through October, revealing lower roost fidelity than the geese that used 1.1 to 1.5 roosting areas each month from November through March. The crows moved a mean distance of 0.11 to 0.49 km/month between their roosting sites and 2.5 to 3.9 km/month between roosting and feeding sites. In contrast, the geese moved 4.2 to 19.3 km/month between roosting areas, and their feeding range varied from 13.2 to 19.0 km/month. Our comparison of the ecological characteristics of bird movements suggests that the limited local movements of crows coupled with frequent turnover of roosts may result in persistence of focal areas for WNV infection. In contrast, widespread areas used by geese will provide regular opportunities for intermixing of AIVs over a much greater geographic area.

California↗

USGS2017

Methods for measuring bird-mediated seed rain: Insights from a Hawaiian mesic forest

Amount and diversity of bird-dispersed seed rain play important roles in determining forest composition, yet neither is easy to quantify. The complex ecological processes that influence seed movement make the best approach highly context specific. Although recent advances in seed rain theory emphasize quantifying source-specific seed shadows, many ecological questions can be addressed u sing a less mechanistic approach that requires fewer assumptions. Using seed rain rates from 0.38 m 2 hoop traps sampled twice monthly over the course of a year, we show that number of traps required to identify changes in seed rain varies across seed species and forest type. Detecting a 50% increase in amount of seed rain required from 65 to >300 traps, while detecting a 200% increase generally required ≤⃒50 traps. Trap size and ecological context dictate the number of seeds found in each trap, but the coefficient of variation (CV) across traps in a given ecological context can help inform future studies about number of traps needed to detect change. To better understand factors influencing variation around estimates of seed rain, we simulated both clustered and evenly distributed patterns of fecal deposition using three different levels of seed aggregation (number of seeds in each fecal deposit). When patterns of fecal deposition were clustered, rather than evenly dispersed across the study area, they required >1.5 times the number of traps to identify a 100% increase in seed rain. Similarly, we found that low seed aggregation required >1.5 times the number of traps to detect a 100% change than when aggregation was medium or high. At low aggregations, fewer seed rain traps contained seeds (low, 33 ± 5%; medium, 23 ± 4%; high, 24 ± 5%), resulting in more variation across traps than medium and high aggregations. We also illustrate the importance of training observers to discern between morphologically similar seeds from different species and provide resources to help identify bird-dispersed seeds commonly found within midelevation mesic Hawaiian forests.

Hawaii↗

USGS2002

Effects of shrubland changes on birds in the Intermountain West

We are integrating field surveys with information obtained from satellite imagery to determine how birds respond to the habitat changes in shrubland regions in the Intermountain West. Our objectives are to determine the primary causes that change shrubland habitats, the spatial and temporal scales at which shrubland landscapes change, and the mechanisms by which distribution and abundance of bird populations are influenced by habitat change.

Fact Sheet↗

USGS2005

Using radar to understand migratory birds and their habitats: Critical needs for the Gulf of Mexico

Nearly all Neotropical migratory landbird species of the eastern United States as well as many western species use Louisiana and the northern Gulf of Mexico coast during their transcontinental migrations each spring and fall. Radar has determined that hundreds of millions of birds make the nocturnal crossing of the Gulf of Mexico resulting in daily flights of as many as 2.5 million individuals stopping in Louisiana to feed and rest. These migration landings are so spectacular that the term “fallout” has been coined to describe the concentrations of birds arriving on the coast.

Fact Sheet↗

USGS2007

Avian influenza surveillance of wild birds

The President's National Strategy for Pandemic Influenza directs federal agencies to expand the surveillance of United States domestic livestock and wildlife to ensure early warning of hightly pathogenic avian influenza (HPAI) in the U.S. The immediate concern is a potential introduction of HPAI H5N1 virus into the U.S. The presidential directive resulted in the U.S. Interagency Strategic Plan for Early Detection of H5N1 Highly Pathogenic Avian Influenza in Wild Migratory Birds (referred to as the Wild Bird Surveillance Plan or the Plan).

Fact Sheet↗