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Effects of Management Practices on Wetland Birds

Bibliography on Survey Methods for American Avocets

Note:  Few sources were found that explained detailed methods for conducting population surveys specific to American Avocets (but see Grover 1979, Skagen and Knopf 1994, Robinson and Oring 1997). Most methods involved finding nests, recording vegetation measurements or avocet behavior, or banding individuals. Some sources for methods were not reviewed. They are listed at the end of the annotated bibliography.

Annotated articles

Colwell, M. A., and L. W. Oring.  1988.  Habitat use by breeding and migrating 
     shorebirds in southcentral Saskatchewan.  Wilson Bulletin 100:554-566.

Shorebird use of habitats was studied in southcentral Saskatchewan during drought conditions in 1984. Censuses were conducted from late April to late August at a permanent wetland and in surrounding pasture from late May to Autumn. Shorebird censuses at wetlands and mudflats were conducted using 1-3 observers in 3-m towers using 20-25x spotting scopes and 7x binoculars. At a beach site, an observer walked the beach and recorded data at points that maximized observations of shorebirds. A stratified random sampling scheme was used to schedule censuses at two sites. During successive weeks, observations were made during random sampling periods that included all daylight hours (0500 to 2100 hr). At a site, observers scanned the site and recorded each bird's behavior and habitat. Habitats were based upon a scale relating water level to an individual's upper tarso-metatarsal joint (Baker, M. C. 1979. Morphological correlates of habitat selection in a community of shorebirds [Charadriiformes]. Oikos 33:121-126).

Colwell, M. A., and L. W. Oring.  1988.  Return rates of prairie shorebirds:  
     sex and species differences.  Wader Study Group Bulletin 55:21-24.

Return rates were determined for five species of juvenile and adult shorebirds at Last Mountain Lake National Wildlife Area, Saskatchewan, during 1982 through 1987. Adult and young Killdeer, American Avocet, Willet, Marbled Godwit, and Wilson's Phalaropes were color-banded. Birds were captured using mist nets, nest traps, decoy traps, and walk-in funnel traps. Each adult was banded with three colored plastic leg bands and a metal band. Some birds were marked with colored nylon patagial tags. Some females were fitted with radio transmitters. Blood was taken from the brachial vein of Wilson's Phalaropes. Chicks were banded after hatching with brood-specific combinations of one color and one metal band.

Colwell, M. A., and L. W. Oring.  1990.  Nest-site characteristics of prairie 
     shorebirds.  Canadian Journal of Zoology 68:297-302.

Nest sites were characterized for Piping Plover, Killdeer, American Avocet, Willet, Upland Sandpiper, Marbled Godwit, Common Snipe, and Wilson's Phalarope at Last Mountain Lake National Wildlife Refuge, southcentral Saskatchewan. Nests were located and site characteristics measured from 1982-1984. Nests were located by watching birds from observation posts. These posts were either towers 3 m high or field vehicles. One to four observers conducted observations in the mornings or evenings using 7x binoculars and 22-25x spotting scopes. Nests usually were located by watching pairs of birds as they chose nest sites, or by observing laying or incubating birds returning to nests. A few nests were found by observers when they flushed birds off nests. Birds were marked with colored bands and a metal band.

Nest-site characteristics measured on the day a clutch was completed were distance to nearest patch of unvegetated soil >1 m², distance to standing water of the wetland, distance to wetland edge (major aquatic/vegetative or aquatic/terrestrial interface), distance to active conspecific nest, and distance to active shorebird nest. Several vegetative measurements also were taken. These included percent cover of grass, forb, bare ground, and cow pies; vertical and horizontal structure (e.g., maximum vegetation height, total number of vegetation hits, average litter depth, and average number of contacts by vegetation in the 1-dm height interval nearest the ground on a 5 mm diameter rod); and heterogeneity of vegetation as measured by coefficients of variation for total number of vegetation hits and maximum vegetation height.

Dole, D. A.  1986.  Nesting and foraging behavior of American Avocets.  M. A. 
     thesis.  University of Montana, Missoula, Montana.  85 pages.

Breeding biology and foraging behavior of American Avocets were studied at Benton National Wildlife Refuge in northern Montana during 1983 and 1984. Birds were observed from mid-April through mid-July. Nests were located by daily nest searches on foot during the first few weeks of the breeding season. Nests on shorelines were marked by placing a numbered stake 15 paces inland. Nests on islands were marked by placing a 5 cm high wooden marker 15 cm from the nest. After incubation started, nests were checked every other day until near hatching, at which time nests were checked daily. Eggs were marked with identifying symbols with a marking pen. Eggs were labeled in order of the sequence by which eggs were laid, if known. Date each egg was laid (if known), number of eggs in each clutch, and date at which incubation commenced were recorded. Length and breadth of eggs was measured and egg volume estimated.

Binoculars and spotting scopes were used to observe behavior, and a tape recorder was used to record observations. Most observations were taken from inside a vehicle, but some were taken when the observer was in view of the birds. Male and females avocets were distinguished by bill morphology.

Nest measurements were taken.

Gibson, F.  1971.  The breeding biology of the American Avocet (Recurvirostra 
     americana) in central Oregon.  Condor 73:444-454.

Spring arrival period, chronology of breeding activities, courtship, territory, nesting, incubation, hatching, care of young, and preparation for fall migration of the American Avocet were studied on the Summer Lake Management Area, Lake County, in southcentral Oregon during spring and summer from 1967 to 1969. A 3.75-km census route, in which number of avocets was recorded, was conducted in the mornings, daily from 1 April to 17 May and on alternate days through 10 July, to obtain an index of the seasonal flux of breeding activities. Time budget data and behavioral observations were made throughout the breeding cycle. Behavioral observations were made from an automobile or from 3-m tall observation towers. Time budget data of a pair of avocets were recorded at 10-sec intervals for 30-min observation periods, with time measured by a metronome. Nests were located, eggs were marked with fingernail polish, and fate monitored during twice-daily visits during egg-laying and hatching and daily or alternate-day checks during incubation. Territory position, boundaries, and patterns were observed by recording positions of a pair every 10 sec within a grid system.

Giroux, J. F.  1985.  Nest sites and superclutches of American Avocets on 
     artificial islands.  Canadian Journal of Zoology 63:1302-1305.

Use by breeding American Avocets of 80 artificially created islands was examined in southeastern Alberta from 1976 to 1978 and in 1980. Monthly nest searches were conducted on artificial islands between late April and early July by walking parallel transects 2-3 m apart. For each nest, the number of eggs was recorded and the nest location was indicated on a scaled map using a coordinate system. Distances from each nest to the nearest conspecific nest and to the shoreline were recorded. Five variables were used in a stepwise multiple regression analysis that examined variation in nest density among islands: the size of the island, the distance between the island and the nearest shoreline, the maximum water depth between the island and the nearest shoreline, the percentage of the island surface covered with sparse colonizing vegetation, and the percentage of the island surface covered with emergent plants.

Grover, P. B.  1979.  Habitat requirements of charadriiform birds nesting on 
     salt flats at Salt Plains National Wildlife Refuge.  M.S. thesis.  
     Northeastern Oklahoma State University, Tahlequah, Oklahoma.  38 pages.

Density, distribution, nest site selection, and reproductive success were studied for the American Avocet, Snowy Plover, and Least Tern on the Salt Plains National Wildlife Refuge in northern Oklahoma during the breeding seasons of 1977 and 1978. Direct censuses were conducted using a 20x field telescope or 7x binoculars in order to determine absolute minimum numbers of breeding birds. Counts were performed bi-weekly. Salt flats were scanned systematically. Grover assumed that all adult birds were paired; population size was based on direct counts of adult birds. Field studies were conducted from 29 April through 20 July the first year, and from 1 May through 7 August the second year.

Nests of the species were located and plotted on a map. The distances of nests to the nearest body of water, nearest nest of any species, and to the nearest nest of a conspecific were recorded after nesting activities were completed. The authors tested whether nests were preferentially placed near debris (driftwood, fenceposts, or discarded refuse) or near the water. Samples of aquatic and terrestrial invertebrates were taken and direct observations of feeding birds were used to estimate food habits. Nests were checked every 1-3 days and six time-lapsed cameras monitored six selected nests each year.

Hill, L. A.  1985.  Breeding ecology of Interior Least Terns, Snowy Plovers, 
     and American Avocets at Salt Plains National Wildlife Refuge, Oklahoma.  
     M.S. thesis.  Oklahoma State University, Stillwater, Oklahoma.  106 pages.

Trapping techniques were described and effects of capture, handling, and radio transmitters on Interior Least Terns and Snowy Plovers were examined in 1983 and 1984. Nests were found and monitored every 1 to 3 days. Least Terns and Snowy Plovers were captured using T-traps and divided into two groups. Birds in group one were marked with a USFWS band and, in addition, plovers were marked with three plastic bands. Group one individuals were marked in all stages of incubation. Birds in group two were marked with a USFWS band and equipped with a back-mounted radio transmitter during late incubation. Before release, birds were placed inside a release box. Traps were set and left overnight at 15 tern and 20 plover nests to determine if trap presence affected nest depredation. Effects of trapping and radiomarking were examined by comparing depredation and desertion rates, daily nest survival, and daily egg survival of experimental groups and control groups that were not trapped, handled, or marked.

A method for determining incubation stage for Least Tern, Snowy Plover, and American Avocet clutches was described. For each species, eggs from 20 known-age nests were measured at 3-5 day intervals throughout incubation. Egg length, breadth, and weight were measured. Eggs were placed in a beaker of distilled water and the angle of flotation measured. Diameter of the shell protruding above the water also was measured. Linear regression models were then developed to predict hatching dates.

Effects of weather, nest substrate, nest cover, nearest neighbors, and inter-nest distances on reproductive success were examined for Least Terns, Snowy Plovers, and American Avocets. Distance and direction to nearest reference point, substrate type, and relative distance to objects or vegetation was recorded at each nest. Nests within 30 cm of an object were categorized as beside the object, nests covered from above were categorized as under the object, and nests within a cowpie or other object were considered inside the object. Nearest inter- and intraspecific-neighbor distances were measured. Nests were checked every 3-5 days, and nests were considered successful if at least one chick hatched. Failed nests were those for which a clutch disappeared or egg remains or predator signs were found.

Plissner, J. H., S. M. Haig, and L. W. Oring.  2000.  Postbreeding movements of 
     American Avocets and implications for wetland connectivity in the western 
     Great Basin.  Auk 117:290-298.

The postbreeding movements of radio-marked American Avocets were examined in the major alkali lake systems of the western Great Basin (Oregon, Nevada, and California) in 1996 and 1997. A total of 185 breeding adult avocets were banded and color-marked from five wetlands. Adults were captured while incubating clutches that were ≥10 days old, using walk-in nest traps or custom-designed, spring-loaded traps. All birds were given a unique combination of colored leg bands that identified the year, site, and individual bird. Radio transmitters were put on aluminum bands. Air and ground surveys were conducted on a weekly basis, in most cases, and radio-tagged birds were located. Ground surveys were conducted beginning 1 June. From mid-June through September, aerial surveys were conducted.

Robinson, J. A., and L. W. Oring.  1996.  Long-distance movements by American 
     Avocets and Black-necked Stilts.  Journal of Field Ornithology 67:307-320.

Returns of banded American Avocets and Black-necked Stilts to locations in California and Utah were used to determine migration and winter locations. Avocet and stilt young and adults were color-banded with unique combinations of UV-resistant colored bands. Avocets were sexed by bill curvature and stilts by plumage. Adults were trapped on the nest after 14 days of incubation and banded. Set traps were visually monitored from a portable blind or a vehicle and birds removed from traps immediately. Trapping occurred during the hottest part of the day when adults would be most likely to incubate. Adults were not kept off the nest for more than 20 min. Eggs were replaced with painted wooden imitations during trapping to prevent overheating. The real eggs were kept in the shade or stored in an egg carton in the blind, and were replaced after trapping. Members of a breeding pair were not trapped on consecutive days; the second bird was trapped after eggs had pipped. Chicks were banded within 6 h of hatching or after leaving the nest.

The banding effort was publicized in magazines and by verbal contact to increase reports of sightings. Sightings from the time of departure of breeding areas through October were classified as migratory, whereas sightings from November through February were classified as winter observations.

Robinson, J. A., and L. W. Oring.  1997.  Natal and breeding dispersal in 
     American Avocets.  Auk 114:416-430.

Natal philopatry of male and female American Avocets, social and temporal aspects of reproduction, and dispersal and mate retention were examined from 1992 through 1994 in Honey Lake Valley, northeastern California. Banding was conducted in 1991 at Lahontan Valley in Nevada. American Avocets were trapped on nests after 14 days of incubation and at the heat of the day, when they were apt to be incubating. Birds were not kept off nests for more than 20 min. Eggs were replaced with wooden imitations and were placed back in the nest immediately after trapping. Members of a pair were not trapped on consecutive days; the second bird was usually trapped when eggs were hatching. Chicks were banded at the nest within 6 h of hatching or were caught by hand after leaving the nest. Adults were banded with unique combinations of three to five colored bands and a numbered federal, metal band. Chicks were banded with brood-specific combinations of one to two colored bands and a federal band. Colored plastic tape placed over the band distinguished individuals within broods.

Resightings were taken daily and weekly. Daily resightings were done by 1-2 person field crews that surveyed 3-4, 0.6 - 1.1 km² ponds from vehicles or portable blinds using 15-60x spotting scopes. Each crew spent about 8 hr/day, 6 days/wk, in their assigned area. Each site also was systematically surveyed every seven days and the identity and location of each marked bird sighted.

Numbers of nesting birds were estimated using weekly counts and estimating clutch initiation dates from all known nests. Median dates by wetland complex differed by 1-2 weeks, so the number of nesting birds was estimated by counting the number of birds present 2 weeks prior to the median clutch initiation date for a particular site, on the median initiation date, and 2 weeks after the median initiation date.

Proportion of chicks banded, probability of detecting fledged young, and dispersal and survivorship measurements also were estimated.

Sidle, J. G., and P. M. Arnold.  1982.  Nesting of the American Avocet in North 
     Dakota.  Prairie Naturalist 14:73-80.

Breeding biology of the American Avocet was studied on two natural saline lakes in Stutsman County, North Dakota during the breeding season of 1981. Data were collected at Chase Lake National Wildlife Refuge and Mud Lake Waterfowl Production Area, which were located on the Missouri Coteau of the Prairie Pothole Region. Searches for nests were conducted by foot on lakeshores and islands. Plant communities were examined using color, low-level aerial photographs and ground surveys. Plant species within 0.3 m of the nest were recorded. A Lietz level was used to determine elevation above nest and of various vegetation zones above water level on the islands. Nests were marked with flags placed 4 m from the nests. Nearest nest distance, distance to water, height above ground, construction material, various egg measurements, and nest fate were recorded for each nest. A successful nest was identified by tiny egg shell fragments at the bottom of the nest cup.

Skagen, S. K., and F. L. Knopf.  1994.  Migrating shorebirds and habitat 
     dynamics at a prairie wetland complex.  Wilson Bulletin 106:91-105.

Opportunistic use of wetlands by migrating shorebirds was examined at Quivira National Wildlife Refuge in Stafford County, Kansas, from 1989 to 1992. Shorebird censuses were conducted from a vehicle or on foot 1-2 times a week during fall migration (from August through mid-October) and spring migration (April to early June). Complete counts of shorebirds were possible because of the openness of the vegetation. Where possible, all individuals were identified. When large numbers of shorebirds were present, or when birds were too distant to identify individually, total numbers of birds based on relative body size were estimated. Subsamples of birds were extrapolated to estimate the number of birds in large groups.

Percentage of a wetland that consisted of dry mud, wet mud, mud-water film (1-2 cm of water mixed with mud), shallow water (2-8 cm) and deep water (>8 cm) was estimated. Availability of suitable foraging habitat (i.e., wet mud-shallow water) during six migration periods (3 spring and 3 fall) was examined, and was based on unit-seasons (each wetland was one water unit for one migration season). Availability ranged from 36 unit-seasons having no wetlands with suitable foraging habitat (either due to flooding or to drying) to 4 unit-seasons having available habitat throughout the breeding season. Within the wetland complex, however, there was usually at least one wetland with wet mud/shallow water at any given time.

Winton, B. R., and D. M. Leslie, Jr.  1997.  Breeding ecology of American 
     Avocet (Recurvirostra americana) in north-central Oklahoma.  
     Bulletin of the Oklahoma Ornithological Society 30:25-32.

Habitat use and nest success of American Avocets were examined at Salt Plains National Wildlife Refuge in northern Oklahoma in 1995 and 1996. Nests were located during systematic searches and monitored with the aid of an all-terrain vehicle, binoculars, nest markers (dowels), and a tape recorder. Nests were visited every 1-6 days until nest fate was determined.

The following sources may provide more information.

Altmann, J.  1974.  Observational study of behavior: sampling methods.  
     Behaviour 49:227-265.

Hands, H. M., M. R. Ryan, and J. W. Smith.  1991.  Migrant shorebird use of 
     marsh, moist-soil, and flooded agricultural habitats.  Wildlife Society 
     Bulletin 19:457-464.

Harrington, B. A.  1992.  A coastal aerial winter shorebird survey on the 
     Sonora and Sinaloa coasts of Mexico.  Wader Study Group Bulletin 67:44-49.

Shuford, W. D., V. L. Roy, G. W. Page, and D. S. Paul.  1994.  A comprehensive 
     survey of shorebirds in wetlands at Great Salt Lake, Utah, 10-11 August 
     1994.  Contribution no. 655.  Point Reyes Bird Observatory, Stinson Beach, 

Warnock, N., S. M. Haig, and L. W. Oring.  1998.  Monitoring species richness 
     and abundance of shorebirds in the western Great Basin.  Condor 100:589-

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