Eric G. Bolen

A 12-Year Study of Nest Box Utilization by Black-Bellied Whistling Ducks

Nest box utilization by black-bellied whistling ducks (Dendrocygna autumnalis) over a 12year (1964-75) period was 81%. Proximity of water was not critical for this species; the ducks also utilized natural cavities more than 1,000 m from water. Of 778 nests of 1 or more eggs, 279 were incubated and 75% of these hatched. At least 70% of all clutches were dump nests with only 15% of the clutches falling within the range (9-18, mean of 13) presumed to be the eggs of a single hen. The remaining 15% of the nests contained less than 9 eggs. About 48% of the eggs in incubated nests produced ducklings but only 20% of 21,982 eggs laid in nest boxes hatched, largely because of desertion from dump nesting. J. WILDL. MANAGE. 43(4):936-943 The black-bellied whistling duck is a Neotropical species usually reaching the northern limit of its breeding distribution in southern Texas. This species, perhaps singularly among the whistling ducks, utilizes natural cavities as nesting sites. They seemed adaptable to a nest box management program that was initiated by Bolen (1967a) in southern Texas. This paper describes a 12-year history of utilization of nest boxes and presents additional information on the breeding biology of black-bellied whistling ducks. The data reported here were collected principally by Bolen and his associates for the 1st 11 years of the study and by McCamant for 1975. Our field efforts were assisted by B. W. Cain, D. E. Delnicki, R. K. Metzger, S. E. Labuda, S. C. Shults, and B. W. Bolen. Our manuscript benefited from the reviews of D. E. Delnicki, B. R. Chapman, and J. W. Tunnell, Jr. This research was supported by grants from the Rob and Bessie Welder Wildlife Foundation and was supervised, in part, by the Biology Faculty at Corpus Christi State University.

Winter condition of mallards on the Southern High Plains of Texas

Body composition and condition of mallards (Anas platyrhynchos) wintering on the Southern High Plains (SHP) of Texas were studied from October to March 1979-82. Lipid reserves, and usually body weights, of all sex and age classes were lowest in autumn. By mid-winter, however, lipid reserves increased 49-62% for adults and 21-30% for juveniles and averaged 13-18% of body weight. The majority of these reserves (56-100%) were acquired from autumn to early winter. Adults and juvenile females then lost lipids from mid-winter to late winter (9-15%), but juvenile males increased reserves by 20%. Adult females mobilized more lipids than adult males during late winter (15 vs. 9%) and previously had acquired a larger reserve (20 vs. 7%). Body weight and lipids increased before spring migration. Overall, mallards on the SHP maintained better condition than those wintering farther north. J. WILDL. MANAGE. 50(1):52-57 Body weight and carcass composition of waterfowl are not stable during winter (Peterson and Ellarson 1979, Raveling 1979, Reinecke et al. 1982). These changes may be influenced by body condition, which has been defined as an individuals ability to meet present and future needs (Owen and Cook 1977). In this paper we refer to condition as the relationship between an individuals endogenous energy reserves and energy demands for maintenance, productivity, and activity. The SHP of Texas is an agricultural region where wintering mallards have adopted a fieldfeeding strategy; they join northern pintails (A. acuta), American wigeons (A. americana), and green-winged teal (A. crecca) in morning and evening field-feeding flights for waste corn (Baldassarre and Bolen 1984). More than 90% of the diet, by volume, consisted of corn during a 2-year study sampling 324 mallard crops and gizzards (Moore 1980). Corn is higher in energy than seeds of native plants occurring in the numerous playa lakes that serve as wetland habitat for waterfowl on the SHP (Baldassarre et al. 1983). This high energy content influences body condition as available carbohydrates are converted into endogenous lipids (Hazelwood 1976). Lipids, in turn, become important reserves used by birds during periods of winter stress (Blem 1976). However, although mallards wintering on the SHP have access to high energy foods, they also encounter temperature stress during certain periods (Whyte and Bolen 1984). The objective of this study was to determine the relationship between winter stress and carcass composition, especially lipid reserves, of mallards wintering on the SHP. Financial support was provided by the Caesar Kleberg Found. Wildl. Conserv. and the U.S. For. Serv. (F. A. Stormer, Proj. Leader, Great Plains Wildl. Habitat Res. Lab.). J. D. Myrick, J. R. Davis, C. L. Lee, H. A. McLain, D. W. Brown, W. J. Hill, and T. J. Hill granted access to private property. R. J. Baker, K. T. Scribner, J. J. Juen, E. E. Quinlan, G. E. Huber, R. H. Lunn, and R. D. Godfrey aided collection of mallards during hunting seasons. R. D. Godfrey, J. A. Templer, and J. J. Peterson assisted with laboratory work. L. J. Celentano and D. B. Webster provided advice during statistical and computer analysis of the data. We are grateful to all. This is contribution T-9-370 of the Coll. Agric. Sci., Texas Tech Univ., Lubbock.

EAGLE-LIVESTOCK RELATIONSHIPS: LIVESTOCK CARCASS CENSUS AND WOUND CHARACTERISTICS'

This paper reviews the physical damage eagles inflict when attacking their prey and, with these and other descriptions of wounds as guides, reports a field appraisal of livestock succumbing to predation on western rangelands. Massive subcutaneous hemorrhages and talon punctures on the dorsal surface of lambs characterize a victim of an eagle attack. Head and facial wounds are seldom present on eagle kills. More livestock carcasses were located per manhour of search in the Edwards Plateau Region (represented by the Eldorado, Texas, area) than elsewhere. How- ever, using criteria we developed from the literature and from our own observations, we believe that no more than 10 percent of these carcasses were actually victims of predation (all types). Still births and other circumstances seemed to account for many of the other losses. Our studies in the Edwards Plateau Region did not fully coincide with the beginning of the regions lambing season. About 38 percent (3) of the dead lambs and kids found in the Val Verde Region of Texas were attributed to predatory losses. Only two dead lambs were discovered in the Guadalupe Mountain Region in 148 manhours of search; of these, one appeared the victim of predation, the other was a birth fatality. Overall, 25 percent of the deaths we could analyze among lambs and kids were attributable to predators. Ranchers we interviewed indicated that little or no eagle damage occurred during the course of our field work, a contention we fully support. Claims of livestock losses from predation have fostered both exten- sive and intensive predator control measures on many western range- lands. Stockmen and conservationists nonetheless often differ in their views of these controls and their ecological impact. Hence Leopold et al. (1964) prepared a comprehensive review of the philosophies and practices associated with predator control as a guideline for agencies charged with the stewardship and management of wildlife popula- tions. This policy statement, in particular, urged that specific predators be identified and that any susbequent control measures be both selec- tive and locally applied.

Fall Diet of Lesser Prairie Chickens in West Texas

Published accounts of feeding habits of the Roadrunner (Geococcyx californianus) (Zimmerman, Condor 72:475476. 1970: Binford. Calif. Birds 2:139. 1971) include the fact that the species is known to capture small birds on the ground. A. C. Bent (U.S. Natl. Mus. Bull. 176:45, 1940) briefly mentioned observations of the capture of a swift and a House Sparrow (Passer domesticus) in flight by Roadrunners, which leaped into the air from the ground. However, I find no detailed description in the literature of the aerial capture of a bird. On 28 April 1974, my husband and I were watching and photographing hummingbirds of several species at our window feeders in Portal, Arizona. We became aware that one of our resident pair of Roadrunners was crouched on the roof of a small porch nine feet above ground, just above the hummingbird feeders which hang from wires from the eaves (fig. 1). We had seen it on the ground below the feeders, occasionally leaping into the air in an unsuccessful attempt to catch a bird. Several times the Roadrunner changed position and made tentative passes at the birds. Suddenly it leaped off the roof and snapped up a Black-chinned Hummingbird (Archilochus alexan&) in flight, landing on the ground with the bird in its beak. I quickly took one picture and then we followed the bird as it ran off, but shortly lost it in brush. Forty minutes later I noted either this same Roadrunner or another running across the yard with another bird in its beak, this one sparrow-sized. The unusual aspect of this incident is that the Roadrunner attacked its flying prey from an elevated perch rather than the ground. On 20 June 1974, we saw a Roadrunner pounding something on the ground by our brush pile, where we have several sugar-water feeders for orioles and hummingbirds, hanging from low branches. We approached the Roadrunner, which ran a short distance and dropped its prey-a Black-chinned Hummingbird that died in less than a minute. We speculate that the Roadrunner caught this hummingbird by jumping into the air from the ground.

Blood parasitemia in a south Texas wintering waterfowl population.

Eleven species of wintering waterfowl were trapped on the Welder Wildlife Foundation, San Patricio County, Texas, between October, 1976 and May, 1977. Blood films were made from 580 ducks. Leucocytozoon simondi, Haemoproteus nettionis, Plasmodium circumflexum, and a microfilaria were found in three species. These blood parasites occurred in 70 lesser scaups (Aythya affinis), 12 blue-winged teals (Anas discors), and 3 ring-necked ducks (Aythya collaris). There was no difference in the rates of infection between the sexes of the three host species. Adult blue-winged teal and lesser scaup were more heavily infected than juveniles. Juvenile ring-necked ducks had more parasites than adults. Blood parasites were found in 85 of 580 ducks (14.6%) throughout the wintering period.

NATURAL NEST SITE AVAILABILITY FOR BLACK-BELLIED WHISTLING DUCKS IN SOUTH TEXAS'

The availability of suitable cavities for the nests of black-bellied whistling ducks was determined at two sites in southern Texas. Using criteria from cavities where ducks actually nested, it was determined that one suitable cavity was available for every 19 acres of ebony or live oak savannah. The species of tree per se, however, is not especially important as nests have been found in willow, elm, and others; factors which are important to cavity formation are longevity, wood density, and growth form. Black-bellied whistling ducks may nest in trees at con- siderable distances from water; over 30 percent of the nests were 500 meters or more from water. Trees with suitable cavities were 64 cm DBH and 52 cm in diameter at

A Holding Sleeve for Waterfowl

We developed a simple method to confine ducks so that a person working alone would be able to take blood samples from the brachial vein of a birds extended wing. A piece of polychlorinated vinyl (PCV) pipe about 30 cm long was slotted about half way from the end to accommodate the birds extended wing; the slot was about 12 mm wide. Sleeves of 2 sizes were made, one of 7.5-cm diameter pipe to accommodate blue-winged teals (Anas discors) and another of 11.5-cm diameter for lesser scaups (Aythya affinis) and similar-sized ducks. A larger sleeve, 12.6 cm in diameter, would be useful for larger ducks such as mallards (Anas platyrhynchos), although we did utilize the 11.5-cm sleeve for 10 canvasbacks (Aythya valisineria) without much difficulty. Each duck was inserted head first into

Differential Responses of Male and Female Pintail Ducks to Decoys

Field tests employing 3 variations in sex ratios (50:50; 100:0; 0:100) of pintail decoys revealed a higher proportion of male pintails (Anas acuta) responded to the decoys than existed in the local population. These results contrast with those of the canvasback (Aythya valisineria) where Olson (1965) found that females were especially vulnerable, perhaps contributing to the imbalance in the continental population of this species. The sex ratio and other characteristics of decoy arrangements may be a useful tool in managing the annual waterfowl harvest, and a vulnerability pattern for pintails is suggested for this form of management. J. WILDL. MANAGE. 41(4):657-661 In 1918 bird banders and field naturalists realized that the sex ratios of certain ducks, especially diving ducks (Aythya), were disproportionate (Erickson 1943). The imbalance, favoring males, is in contrast to the more or less balanced sex ratios among puddle ducks (Anas) (Beer 1945, Smith 1946, Johnsgard and Buss 1956, Hochbaum 1959: 15, Anderson et al. 1969). However, the sex ratios for both diving and puddle ducks do not differ from the expected 50:50 distribution at fertilization, hatching, or among juveniles yet the imbalance is clear among adults as noted by Hochbaum (1959:51), Sowls (1955:164) and especially Bellrose et al. (1961:405). One must therefore assume that some phenomenon affects the sex ratios of diving ducks after the time each cohort attains flight. Olson (1965) proposed that hunting, as measured by the differential response of each sex to decoys, resulted in higher mortality of females. Earlier, Trippensee (1953:194) and Hochbaum (1959:150) also suggested that hunting may be the responsible factor for imbalanced sex ratios but Mendall (1958:225), in his study of the ring-necked duck (A. collaris), felt that the effects of hunting might in fact bring sex ratios into balance. We designed experiments to test Olsons (1965) conclusions on a common puddle duck, the pintail. If the hypothesis is correct there should be no difference in the response between males and females to decoys as the sex ratio of the continental pintail population is nearly in balance and thus presumably unaffected by hunting. Our objectives were to determine if sex classes of pintails respond to pintail decoys differentially and to compare Olsons data for a species exhibiting an imbalanced sex ratio (the canvasback) with data for a species showing far less imbalance in its continental population (the pintail). Our study is confined to pintail ducks wintering in the Texas Panhandle. We are indebted to the Max McGraw Wildlife Foundation of Dundee, Illinois, for financial assistance and to M. K. Rylander for his critical review of the manuscript.

Wildlife Ecology and Management

1. What is Wildlife Management? 2. Neglect and Exploitation. 3. Some Successes in Managing Wildlife. 4. Ecosystems and Natural Communities. 5. Population Ecology 6. Animal Behavior and Wildlife Management. 7. Food and Cover. 8. Wildlife Diseases. 9. Predators and Predation. 10. Hunting and Trapping. 11. Wildlife and Water. 12. Wildlife and Soils. 13. Wildlife and Farmlands. 14. Wildlife and Rangelands. 15. Forest Management and Wildlife. 16. Wildlife in Parks and Refuges. 17. Urban Wildlife. 18. Exotic Wildlife. 19. Nongame and Endangered Wildlife. 20. Economics of Wildlife. 21. Conservation Biology and Wildlife Management. 22. Wildlife as a Public Trust. 23. Conclusion. Glossary. Literature Cited. Index.