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Methiocarb [4-(methylthio)-3,-5-xylyl N-methylcarbamate] was tested as a seed treatment for repelling blackbirds and crows ( Corvus sp.) from sprouting corn in South Carolina. The test was conducted on eight fields within a 0.25-square-mile area. Marked repellency occurred; sprout damage averaged 44 percent in the control fields and 0.3 percent in the fields treated with methiocarb.
North American ospreys ( Pandion haliaetus carolinensis ), banded primarily in the Middle Atlantic States and in New England, apparently migrate to their winter grounds in the West Indies and South America on a broad front. Ospreys do not return to the United States as 1-year-olds, but an estimated 28 to 55 percent return to their natal vicinity (state where hatched or an adjacent state) as 2-year-olds. The 2-year-olds (presumably nonbreeders) are estimated to represent 5 to 10 percent of the population on the northern breeding grounds. Nest studies suggest that about 6 percent of the population on the breeding grounds consists of nonbreeders (presumably the 2-year-olds). These birds are associated with nests but do not lay eggs or exhibit brooding behavior. The point to be made to individuals conducting nest studies on ospreys is that nests should not be classified as active if eggs are not laid, even though a pair is present. If nests with no eggs are excluded from studies, we believe the observed recruitment rates can be validly compared with the recruitment standard (production rate required to maintain a stable population) of Henny and Wight (1969).
Of 3,789 recoveries of blue-winged teal ( Anas discors ) banded prior to the hunting season in the prairie pothole region, 183 (4.8 percent) were recovered, due east in New England, Ontario, Quebec, and the Maritime Provinces during the subsequent hunting season. Of 19 recoveries looked at in detail, all were banded as either hatching-year (flying young) or local (flightless young) birds. A blue-winged teal banded in Minnesota in September was retrapped in October in South Carolina, before being shot later that month in Colombia, South America.
Waterfowl use of bottomland hardwood timber stands which were flooded and killed was studied at the Montezuma National Wildlife Refuge, Seneca Falls, New York, from 1962 to 1964. Comparisons of use were made among six habitat types containing dead timber, stumps, and no timber, and with and without emergent vegetation. An index to waterfowl use was derived by direct counts and by counts made with automatic cameras which photographed randomly selected plots in each habitat type. Movement between types was studied by observation of both marked and unmarked birds. The camera index of use showed that cut timber with emergent vegetation received the greatest overall use. Use was positively correlated with the proximity of the plot to emergent vegetation and nearest vegetative type boundary. A stand flooded for 7 years was used primarily by black ducks ( Anas rubripes ) and mallards ( A. platyrhynchos ). Use of stands flooded for 20 years was dominated by American widgeon ( Mareca americana ). Waterfowl spent more time resting than feeding in timbered areas, and more time feeding than resting in marsh areas. Young-of-the-year did not move between pools after they had reached an age of IIc (Gollop and Marshall 1954). Use by broods was greatest in areas near emergent vegetation. Flying birds used timbered areas during the daytime and non-timbered areas at night during fall. Flooded dead timber appeared to be attractive to waterfowl because it furnished abundant loafing sites.
As a major part of establishing hunting regulations each year in the United States, data for the mallard ( Anas platyrhynchos ) are examined extensively to estimate the effect of various harvest strategies on the breeding population the following spring. This requires estimates of the breeding-population level and of the production, harvest, and mortality rates. Predictions made at the time hunting regulations are established have been in general agreement with more reliable estimates made after the hunting season when data from banding, kill, and wing surveys are available.
Because of low population levels, there were especially restrictive hunting regulations between 1958-1965, including complete closures during the 1960-1963 seasons, for canvasback ( Aythya valimeria ) and redhead ( A. americana ) ducks. Banding data from 1952 through 1965 indicated that restrictive regulations reduced both harvest and annual mortality rates. During the period with very restrictive regulations, annual mortality-rate estimates ranged from 14 to 21 percent, much lower than before this period when estimates were 50 percent or higher.
The validity of group counts, cannon-net catches, and hunter-bag checks for estimating productivity of lesser snow geese ( Anser caerulescens caerulescens ) and small Canada geese ( Branta canadensis hutchinsii-parvipes complex) was studied at Sand Lake National Wildlife Refuge during the falls of 1965 and 1966. Age ratios of snow geese obtained from net-trapped samples were significantly higher (P < 0.01) than from group counts at the same site. Immature snow geese were shot in a significantly greater (P < 0.01) proportion than they existed in the population as determined by group counts. Cannon-net catches and hunter-bag checks of snow and Canada geese yielded age ratios which were biased because of behavioral characteristics of the geese. Immatures of both species were less wary of trap equipment and immature snow geese were more vulnerable to the gun than adults. It was believed that age ratios from group counts of snow geese were more representative of the population than those from net catches and hunter-bag checks. Sex ratios of net-trapped geese showed a preponderance of males for adult Canada and adult and immature snow geese, whereas females were predominant in the immature segment of Canada geese. Hunter selectivity of blue- or white-phase snow geese was not observed at Sand Lake Refuge. Differential vulnerability to hunting between snow and Canada geese resulted from differences m feeding-flight behavior.
Bursa of Fabricius depths of 88 lesser snow geese ( Anser c. caerulescens ) and 69 small Canada geese ( Branta canadensis hutchinsii/parvipes complex) were measured. Bursal depths were unreliable indicators of age-classes of lesser snow geese and small Canada geese; previously, the same had been found to be true for large Canada geese ( B. c. interior ). Regression in size or closure of the bursa first occurred at 17-20 months of age (yearlings) in lesser snow geese and small Canada geese, but at 29-32 months of age (2-year-olds) in large Canada geese.
A cable-chain device towed between two vehicles was developed for locating occupied duck nests in brushy, herbaceous, and grassy cover types. Twenty-three of 29 previously located gadwall ( Anas strepera ) and blue-winged teal ( A. discors ) hens were flushed from their nests with the drag for an efficiency of 79 percent. Eighty acres of nesting cover can be searched in 4-6 hours by the method described.
Wildlife casualties from aldrin-dieldrin poisoning are associated with the planting of aldrin-treated rice seed along the Texas Gulf Coast. The fulvous tree duck ( Dendrocygna bicolor ), which depends on the rice field habitats and is highly susceptible to aldrin-dieldrin poisoning, is suffering a serious population decline in that area. Dead waterfowl, shorebirds, and passerines were collected on study areas in Wharton, Brazoria, and Chambers counties, Texas, from 1967 through 1971. Residues of aldrin or dieldrin were found in all samples of bird casualties and in all eggs, scavengers, predators, fish, frogs, invertebrates, and soils. Fulvous tree ducks appeared to be less resistant to aldrin than other ducks. Dieldrin residues in brains of dead fulvous tree ducks were low, but whole-body residues were as high as 16 ppm. Brains of other dead ducks and geese averaged 10 ppm dieldrin. Some dead birds were exposed by eating treated rice seed, but many dead birds with high dieldrin residues were species that feed largely on invertebrates. Although soil residues were low, snails and crayfish contained enough aldrin and dieldrin (average 9.5 ppm) to account for deaths in birds that fed heavily on these invertebrates over a period of time. When fulvous tree ducks were penned for 3 days in fields aerially planted with treated seed, 3 of 10 birds died with brain residues of 2.5, 2.9, and 6.8 ppm dieldrin, and others were intoxicated. None of eight died, and some gained weight, when penned in fields planted with untreated seed. This study adds further evidence for the suspected lethal effects of aldrin-treated rice seed on wild birds and other wildlife in rice field habitats.
This study is an experimental demonstration of lethal mobilization of DDT by brown-headed cowbirds ( Molothrus ater ) and the effects of food deprivation on the distribution and loss of DDT, DDD, and DDE. The principal experimental group consisted of 20 birds fed a dietary dosage of 100 ppm of DDT for 13 days. After 2 days of full rations of untreated food, they were subjected to food restriction. Food was reduced to 43 percent of normal. Seven of the 20 birds died within 4 days. No birds died in the three control groups, treated as follows: ( 1 ) 20 birds fed 100 ppm DDT for 13 days and full rations of untreated food thereafter, (2) 20 birds fed only untreated food but subjected to food restriction, and (3) 20 birds fed full rations of untreated food throughout. In a pilot study, birds were fed 100, 200, or 300 ppm of DDT and subjected to two periods of food restriction, the first of these immediately after dosage ceased and the second 4 months later. DDT-dosed birds from all dosage levels died in each period of food restriction. Before the weight loss that accompanied food restriction, the brains of DDT-dosed birds had concentrations of DDT and DDD that were far below the lethal range. Concentrations increased rapidly to lethal levels. In these birds, DDT in carcasses decreased while DDD increased. DDT-dosed birds that died during food restriction lost 16 percent of their total body burden of DDT + DDD + DDE, 21 percent of their weight, and 81 percent of their fat. The DDT-dosed birds that were subjected to food restriction but survived lost a significantly greater proportion of their body burden of residues than similarly dosed birds not subjected to weight loss. Brain levels of DDT and DDD in birds that died during food restriction soon after dosage did not differ significantly from brain levels of birds that died in a period of food restriction 4 months after dosage. Concentrations of DDE were significantly higher in the latter group, although they were lower than concentrations considered to be lethal. In contrast, carcass levels of DDT and DDD were significantly lower, and DDE was only slightly higher, in the birds that died in the second period of food restriction. It is concluded that stored DDT residues present a hazard to birds, which utilize stored fat during periods of stress due to reproduction, cold weather, disease, injury, limited food supply, or migration.
A night vision scope was used during 1969-71 to study the nighttime feeding behavior of ducks on prairie wetlands of south-central North Dakota. Adult and immature ducks were observed feeding between 9:00 PM and 4:00 AM, predominantly on midges (Chironomidae) and mayflies (Ephemeroptera). The emergence pattern of these insects appeared to be a major factor influencing duck activity and feeding behavior at night.
Waterfowl populations and habitat characteristics were examined on 33 potholes in each of two 16-square-mile study areas of agricultural and nonagricultural land in southwestern Manitoba. The agricultural land potholes, lacking in or incompletely surrounded by trees, received greater use by lesser scaup ( Aythya affinis ), canvasback ( A. valisineria ), redhead ( A. americana ), coot ( Fulica americana ), and three species of grebes ( Podicipedidae ). The nonagricultural land potholes, completely surrounded by trees, were more attractive to blue-winged teal ( Anas discors ), and mallard ( A. platyrhynchos ), and over twice as many dabbler broods were censused there. Abundant, undisturbed nesting cover may have been the reason for greater dabbler use on the nonagricultural land potholes since chemical and biological properties suggest more fertile conditions in the agricultural land.
Unless a correction is made, population estimates derived from a sample of belt transects will be biased if a fraction of, the individuals on the sample transects are not counted. An approach, useful for correcting this bias when sampling immotile populations using transects of a fixed width, is presented. The method assumes that a searcher's ability to find objects near the center of the transect is nearly perfect. The method utilizes a mathematical equation, estimated from the data, to represent the searcher's inability to find all objects at increasing distances from the center of the transect. An example of the analysis of data, formation of the equation, and application is presented using waterfowl nesting data collected in Colorado.
Soil-food-chain-pesticide wildlife relationships were investigated to learn the concentration of pesticide residues present in soils, macro-invertebrates, vertebrates, and seeds as a result of annual applications of aldrin at recommended rates for pest control. Two central Missouri cornfields treated with aldrin at 1 lb/acre, for 16 and 15 of the past 17 years, were selected for study during 1965-67. Primary samples collected for residue analyses included soils, earthworms (Lumbricidae), crickets (Gryllidae), and two kinds of ground beetles (Carabidae) obtained during early April, June, August, and October. Vertebrates and plant seeds collected during 1967 included white-footed mice ( Peromyscus maniculatus ), toads ( Bufo americanus ), snakes ( Thamnophis sirtalis and Pituophis sayi ), corn ( Zea Mays ), foxtail ( Setaria Faberii ), and annual sunflower ( Helianthus annuus ). Pesticide residues consisted primarily of dieldrin, the degradation product of aldrin. Combined aldrin and dieldrin residues, as two field all-season averages, wet weight basis, were: soils, 0.31 ppm; earthworms, 1.49 ppm; crickets, 0.23 ppm; Harpalus ground beetles, 1.10 ppm; Poecilus ground beetles, 9.67 ppm; white-footed mice, 0.98 ppm; toads, 3.53 ppm; garter snakes, 12.35 ppm; and corn, foxtail, and sunflower seeds less than 0.02 ppm each. Unusually high average residues (37.48 ppm) in Poecilus beetles during June, 1967, were attributed to abnormally high soil moisture and predacious feeding habits of these insects.
The lethal effects of heptachlor on bobwhites ( Colinus virginianus ) were studied at the Patuxent Wildlife Research Center during 1962 and 1963. A pair of adult birds was placed in each of 32 wire-covered field pens (20 x 50 x 61/2 ft) in May, 1962, and in 36 additional pens in May, 1963. Heptachlor (technical grade on clay granules) was spread in the pens at rates of1/8, 1/4, 1 1/4 and 2 lb/acre. In 1963 the treated pens were thoroughly soaked with a hose before birds were introduced to avoid the possibility of birds pecking granules. Heptachlor at 1 1/4 and 2 lb/acre caused severe mortality among birds introduced successively during the first 15 days after application. Mortality declined rapidly among birds placed in these same pens thereafter and was undetectable after 45 days. Mortality at 1/4 lb/acre was significant only during the first 15 days of the 1962 test. There was no detectable difference in mortality of the sexes. Water applied to the pens followed by fairly heavy rain did not significantly affect mortality.
The mourning dove ( Zenaidura macroura ) call-count survey is a nationwide audio-census of breeding mourning doves. Recent analyses of the call-count routes have utilized a stratification based upon physiographic regions of the United States. An analysis of 5 years of call-count data, based upon stratification using potential natural vegetation, has demonstrated that this uew stratification results in strata with greater homogeneity than the physiographic strata, provides lower error variance, and hence generates greatet precision in the analysis without an increase in call-count routes. Error variance was reduced approximately 30 percent for the contiguous United States. This indicates that future analysis based upon the new stratification will result in an increased ability to detect significant year-to-year changes.
Mortality of wood ducklings ( Aix sponsa ) from hatching to 6 weeks of age averaged 47 percent during a 4-year study at the Patuxent Wildlife Research Center. Over 90 percent of the total mortality occurred during the first 2 weeks of life. Brood bonds began to dissolve after the fifth week. hlortality after 2 weeks was so low that Class I1 broods were believed to provide reliable estimates of production to flying age. Once-a-week brood censuses proved unreliable in estimating survival, but twice-a-xveek counts were accurate enough to estimate total broods and survival to Class II age.