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Effects of Management Practices on Wetland Birds

Bibliography on Survey Methods for Eared Grebes

Note:  Few sources were found that explained detailed methods for conducting population surveys specific to Eared Grebes (but see Daub 1993, and Koonz and Rakowski 1985). Most methods involved finding nests or colonies, or recording vegetation measurements. Some articles dealt with capturing grebes. Some sources for methods were not reviewed. They are listed at the end of the annotated bibliography.

Annotated articles

Boe, J. S.  1991.  Breeding habitat selection by Eared Grebes in Minnesota.  
     Ph.D. dissertation.  North Dakota State University, Fargo, North Dakota.  
     242 pages.

Habitat selection of the Eared Grebe at the three levels of wetland, colony, and nest site were examined in Minnesota. Individual chapters of the dissertation were devoted to each level and written in manuscript form. Preceding these chapters was a literature review that contained information on avian coloniality, habitat selection, and ecology of Eared Grebes. The study occurred in western and southern Minnesota from 1986 to 1989.

Paper 1: Wetland selection
The characteristics of 24 wetlands used by nesting Eared Grebes were compared to 26 wetlands not used by nesting grebes. Unused wetlands were chosen by means of a stratified random sample of unused wetlands in the same or adjacent counties. Wetlands were stratified by size within wetland classes Types 3-5 (Shaw and Fredine 1971). Type 3 wetlands are shallow, fresh marshes. Type 4 wetlands are deep, fresh marshes. Type 5 wetlands are open, freshwater wetlands that may be fringed with a border of emergent vegetation.

Paper 2: Colony site selection
Twelve colonies within nine wetlands were surveyed. Conditions on wetlands were documented as close as possible to the time the colony was established by using aerial photography. Colonies were photographed in June and July at a mean height of 1475 m using 35 mm photography. Height at which the plane flew was determined by the size of the wetland. On resulting photographs, vegetation types and water depths were marked using marking pens. After nest abandonment, nests were photographed from the air. Characteristics of random sites on wetlands were compared to colony sites. The colony was represented by a single point that was placed at the site of the earliest nest.

Measured wetland characteristics were maximum depth, public access, wetland recreational use, percent open water, submergent vegetation, wetland type, percent emergent fringe, percent treed perimeter, number of buildings within 0.2 km of the wetland, shoreline irregularity (shoreline length / 2 multiplied by the square root of lake area in km² times pi), and percent of perimeter with road or highway within 0.2 km. A coefficient of community (2w/a+b; a = # bird spp. present on used wetlands, b = # spp. on unused wetlands, and w = # species present on both) measured degree of similarity of avian species using the two groups of wetlands. Measured variables were distance from shore, distance to open water, and vegetation composition. Water depth and number of dead cattail stems were measured at 10 randomly selected unused points and at the colony site at one Lake (West Toqua Lake) during the drought year of 1988. Effects of mats of submergent vegetation on wave mediation was measured. A calibrated stick was used to measure wave height in the mat and at points windward and leeward of the mat at Swan Lake. Measurements were taken on 8 June 1988 when wind speed was 34 km/h.

Paper 3: Nest site selection
Eleven colonies on nine wetlands were observed for information on nesting synchrony, nearest-neighbor distances, vegetation, exposure, and nest success. Eggs were floated to determine stage of incubation and color was recorded. Length and breadth of eggs were measured with calipers. Egg volume was estimated. Clutch size was determined. A successful nest was defined as one in which shells without membranes were present or if at least one egg was in a late stage of incubation during the last nest check. Nests were defined as early, peak, or late nests and perimeter nests were located. Perimeter nests were those in which no other nest was located within a 120 degree arc around the nest. Colonies were defined as large if there were ≥50 nests; large colonies were then divided into edge, intermediate, and center nests. In small colonies (<50 nests) and the one large, linear colony, only edge and center nests were defined. Emergent stem densities were measured at some sites by counting stems within a 0.25 m × 0.75 m quadrat placed regularly at 0.75 m intervals along N-S and E-W transects. At one wetland with two colonies, nest placement in relation to dead cattails was examined by comparing percent cover of dead cattail debris in a 5-m diameter around the nests in a similar circle at random points within the colony boundary.

Nesting synchrony was measured by two estimates of span. Span was the number of days between initiation of the first nest and initiation of the last nest in the colony. The second estimate, 50% span, was the minimum number of days during the peak nesting period in which 50% + 1 nests were established.

Breault, A. M.  1990.  Breeding distribution, habitat selection and factors 
     affecting coloniality in Eared Grebes in British Columbia.  M.S. thesis.  
     University of British Columbia, Vancouver, British Columbia.  143 pages.

Past and current breeding distribution and abundance of Eared Grebes in British Columbia were reviewed using historical records. Surveys of 421 lakes (36 lakes for which there were historical records and 385 new lakes) were conducted in 1985 and 1986. Counts of adults and chicks were conducted using binoculars and spotting scopes from shore. Counts were conducted twice on lakes <26 ha; the maximum count was recorded. On larger lakes, adults were counted once. Age and number of chicks were documented on audio tapes. Aging was determined using Gollop and Marshall's (Gollop, J. B. and W. H. Marshall. 1954. A guide for aging duck broods in the field. Mississippi Flyway Council Technical Section. 14 pages.) system of plumage development in waterfowl. Birds were not flushed from emergent vegetation, so counts represented minimum estimates. In cases where chicks were feeding, several consecutive counts were conducted and the highest count recorded. Nests were tallied while walking through emergent vegetation. Active nests, defined as nests containing eggs or indicating signs of hatching such as membranes and shells, were recorded separately from empty platforms. Number of eggs within each nest was recorded.

Up to three estimates of the number of breeding pairs per lake were determined. For adult birds, the estimate was derived from the maximum number of adults seen during April-August divided by two. For nest counts, the minimum number of breeding pairs per lake was obtained from taking the highest number of active nests during each season. For chick counts, the observed number of chicks of a given age were divided by the mean number of chicks per pair surviving to that age. Three periods of chick development were determined: hatching to 2 wks, 2 wks to 1 mo, and 1 mo. to fledging.

Maximum nest counts were used as an overall estimate of abundance of breeding pairs. However, when nest counts were not available or when estimates based on incomplete nest counts were lower than estimates based on chick counts, breeding pair abundance was based on chick counts. Regional estimates of breeding abundance were determined by adding minimum (from nests) and maximum (from adult surveys) estimates from each lake.

Burger, J., and M. Gochfeld.  1995.  Nest site selection by Eared Grebes in a 
     Franklin's Gull colony:  structural stability parasites.  Condor 97:577-

The adaptive significance of Eared Grebes nesting in a Franklin's Gull colony was examined at Agassiz National Wildlife Refuge in northwestern Minnesota in 1994. Nest site selection was examined at one of two Eared Grebe colonies in which the grebes were nesting with Franklin's Gulls. Nest site characteristics were gathered at 32 grebe nests, 32 gull nests, and 32 matched points in the center of the grebe colony. Matched points were selected by using random numbers from which to get a compass direction from a grebe nest. Characteristics of the matched point were taken 1 m from the edge of the grebe nest in the random direction. Measured characteristics at nests were number of eggs, nest width at widest diameter, and percent of eggs covered by vegetation. At nests and random points, distance to edge of nearest gull nest and to nearest gull clutch (to indicate distance between sitting birds), distance to nearest vegetation, percent emergent cover within 1 m of the nest, distance to nearest emergent vegetation that extended above the water, percent surface covered with floating vegetation within 1 m of the nest, total number of live Scirpus stems around the nest, and whether the nest was anchored to a gull nest.

Daub, B. C.  1993.  Effects of marsh area and characteristics on avian 
     diversity and nesting success.  M.S. thesis.  University of Michigan, 
     Ann Arbor, Michigan.  37 pages.

Daub examined the relationship between marsh area, species richness, and nesting success in 20 marshes located near Minnedosa, Manitoba, from 1991-1992. Avian censuses were conducted along the perimeter of marshes by placing a randomly chosen, 100 m × 15 m transect, along which nest-searching also occurred. The 15 m portion of the transect included 5 m of emergent vegetation and 10 m of open water. Each transect was walked for 45 min. Each marsh was surveyed three times during the breeding season, about every two weeks. Playback calls were used to elicit responses from American Bittern, Virginia Rail, Yellow Rail, and Sora at the beginning, middle, and end of each transect during every survey. Nesting success was determined using the Mayfield method. Measured marsh characteristics were water depth, vegetative composition (line-intercept technique), and width of vegetation growing in standing water.

Faaborg, J.  1976.  Habitat selection and territorial behavior of the small 
     grebes of North Dakota.  Wilson Bulletin 88:390-399.

Habitat selection, territorial behavior, and nest dispersion of Horned, Eared, and Pied-billed grebes were studied in Ward County, North Dakota, in the 1970's. The author surveyed over 500 wetlands. Wetlands were classified according to permanence (e.g., seasonal, temporary, semipermanent, permanent), as determined by aquatic plant composition (following Stewart, R. E., and H. A. Kantrud. 1971. Classification of natural ponds and lakes in the glaciated prairie region. Resource Publication 92. U.S. Fish and Wildlife Service, Bureau of Sport Fisheries and Wildlife. 57 pages.). Wetland cover was categorized between a rating of 1-4, with 1 indicating 95% or more of wetland area covered emergent vegetation and 4 indicating 95% or more open water.

On each wetland, number of pairs of grebes were recorded. Nests were found if possible. Size of wetland was determined through cover-mapping or use of aerial photographs. Area of defended territories was noted.

Hill, W. L., K. J. Jones, C. L. Hardenbergh, and M. Browne.  1997.  Nest 
     distance mediates the costs of coloniality in Eared Grebes.  Colonial 
     Waterbirds 20:470-477.

The effect of nest density on behavior and reproduction of Eared Grebes was examined at Malheur National Wildlife Refuge in Oregon in 1993 and 1994. In 1993, two colonies from different lakes that had different nearest-neighbor distances were used. In 1994, two colonies from the same lake that had different nearest-neighbor distances were used.

Distances between nests were measured from the center of a focal nest to the center of the nearest nest. In 1994, distance to the second nearest nest also was measured. Nests were checked daily or every two days. Eggs were marked to identify laying sequence. Length and width of eggs were measured. Egg loss was categorized as conspecific competing (single, floating eggs or with peck marks), predation (all eggs missing or partially eaten remains found), or infanticide (dead chicks). Intraspecific brood parasitism occurred if more than one egg was laid in a nest per day or a new egg appeared in a nest after a delay in egg-laying of 3 days. Nest success was defined by the number of eggs that hatched.

Colonies were observed from a floating blind, from a canoe, or from a truck. Focal observations followed the focal animal continuous sampling method. Instantaneous sampling also was used.

Jehl, J. R., Jr., and P. K. Yochem.  1986.  Movements of Eared Grebes indicated 
     by banding recoveries.  Journal of Field Ornithology 57:208-212.

Banding data from North America were analyzed to elucidate route of fall migration, winter range, and site tenacity for Eared Grebe. Banding data for 1955-1984 came from the Bird-banding Lab of the U.S. Fish and Wildlife Service. Additional data for previous years came from Clapp et al. 1982 (Longevity records of North American birds: gaviidae through alcidae. Journal of Field Ornithology 5381-124.).

Jehl, J. R., Jr., and P. K. Yochem.  1987.  A technique for capturing Eared 
     Grebes (Podiceps nigricollis).  Journal of Field Ornithology 

Use of dip nets aided in the capture of 469 Eared Grebes during their flightless period at the fall molting and staging area of Mono Lake, California in 1985 and 1986. A small (4.5 m) boat with a 20 or 25 horsepower motor trailed grebes that were swimming underwater. A 0.5 m diameter fishing net attached to a 2.8 m pole was used to capture grebes when they surfaced for air. The authors report on grebe's underwater behavior when pursued. Capture rates varied from 4-6 to 10-12 grebes per hour. The dip-net method also worked on Horned Grebe, Western Grebe, Pied-billed Grebe, Gadwall, Mallard, Northern Shoveler, Ruddy Duck, and American Coot. Yellow collars were placed on grebes, but caused mortality, so their usage was discontinued.

Koonz, W. H., and P. W. Rakowski.  1985.  Status of colonial waterbirds nesting 
     in southern Manitoba.  Canadian Field-Naturalist 99:19-29.

Estimates of colonial waterbird numbers were compared between historic data and data measured in 1979. Aerial waterbird censuses were conducted on all major Manitoba lakes south of 54E10'N during June 1979. Islands known to have contained colonial nesting waterbirds were checked at a height of 200-300 m. Active colonies were censused at an altitude of 150 m. Where time permitted, ground counts were made at the active colonies to ground-truth aerial information. Information was presented as number of colonies observed, number of total nests counted, and number of nests found within individual colonies.

Breeding distribution, not only in Manitoba but also the northern Great Plains, and number of recorded colonies in southern Manitoba were given for Eared Grebe, Western Grebe, American White Pelican, Double-crested Cormorant, Great Blue Heron, Black-crowned Night-Heron, Franklin's Gull, Ring-billed Gull, Herring Gull, Caspian Tern, Common Tern, and Forster's Tern.

Lyon, B. E., and S. Everding.  1996.  High frequency of conspecific brood 
     parasitism in a colonial waterbird, the Eared Grebe, Podiceps nigricollis.  
     Journal of Avian Biology 27:238-244.

The occurrence of conspecific brood parasitism in Eared Grebes was examined in two nesting colonies in 1988 in British Columbia. Nests were checked daily at both colonies. Parasitism was determined in three ways: 1) appearance of two or more eggs on the same day, 2) appearance of new eggs after completion of a clutch, and/or 3) disappearance of a marked egg with the simultaneous replacement of an unmarked egg.

The following sources may provide more information.

Boyd, W. S., and J. R. Jehl, Jr.  1998.  Air-photo censuses of Eared Grebes on 
     Mono Lake, California.  Colonial Waterbirds 21:236-241.

Boyd, W. S., S. D. Schneider, and S. A. Cullen.  2000.  Using radio telemetry 
     to describe the fall migration of Eared Grebes.  Journal of Field 
     Ornithology 71:702-707.

Breault, A. M., and K. M. Cheng.  1990.  Use of submerged mist nests to capture
     diving birds.  Journal of Field Ornithology 61:328-330.

Jehl, J. R., Jr.  1988.  Biology of the Eared Grebe and Wilson's Phalarope in 
     the nonbreeding season:  a study of adaptations to saline lakes.  Studies 
     in Avian Biology  12.  74 pages.

Jehl, J. R., .Jr.  1990.  Rapid band wear in Eared Grebes and other saline lake
     birds.  Journal of Field Ornithology 61:108-110.

Jehl, J. R., Jr., A. E. Henry, and S. I. Bond.  1998.  Sexing Eared Grebes by 
     bill measurements.  Colonial Waterbirds 21:98-100.

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