Christian E. Grue

Lead concentrations and reproductive success in european starlings Sturnus vulgaris nesting within highway roadside verges

In 1981, we studied lead concentrations and reproductive success in freeliving European starlings Sturnus vulgaris nesting within the verges of two Maryland highways with different traffic volumes, Route 197 (average daily traffic volume [ADT] = 10 800 vehicles) and the Baltimore-Washington Parkway (ADT = 52 500 vehicles) and a nearby control area. Concentrations (mgkg−1 dry weight) of lead in the ingesta (84–94 mg kg−1), carcasses (4·0–9·6 mgkg−1) and feathers (6·8–52 mgkg−1) of Parkway nestlings and adults were 3 to 13 times those found in starlings from the control area, whereas lead concentrations in the ingesta and tissues of starlings from the verge of Route 197 were similar to those of controls. Activity of δ-aminolevulinic acid dehydratase (ALAD) in red blood cells (RBCs) of adult and nestling starling from the Parkway was depressed from 43 to 60% compared to controls. RBC ALAD activity in adults from nests along Route 197 was similar to that of adult starlings from the control area, but that of their young was depressed 17%. Haemoglobin concentrations (−16%) and haematocrits (−10%) in Parkway nestlings were depressed compared with those of nestlings from the other two study areas, whereas those of adults were not affected. Clutch size, number of young hatched and the number of young in nests 1 to 3 days before fledging were similar among sites, as were body weights of adults and prefledging weights of their young. However, brain weights of Parkway nestlings were lower (P<0·05) than those of nestlings from the other study areas. Results suggest that lead within verges of major highways probably does not pose a serious hazard to adult ground-foraging songbirds. However, the effects of lead-induced reductions in haemoglobin concentration, haemotocrit, RBC ALAD activity and brain weight on the postfledging survival of their young are not known.

CARE OF NESTLINGS BY WILD FEMALE STARLINGS EXPOSED TO AN ORGANOPHOSPHATE PESTICIDE

SUMMARY (1) Our objective was to determine the effect of exposure to an organophosphate pesticide (OP), dicrotophos (3-hydroxy-NN-dimethyl-cis-scrotonamide dimethyl phosphate), on care of nestlings by wild female starlings (Sturnus vulgaris). (2) We selected twelve pairs of active nests based on synchrony in the reproductive cycle. When nestlings were 10 days old (day 10), adult males were captured and killed and brood size was adjusted to four. The frequency and temporal distribution of sorties made by each pair of females to feed their young were recorded for 2 h at 18.00 hours on day 11 and 06.00 hours on day 12. One female from each pair was given a single oral dose of dicrotophos (2-5 mg/kg of body weight) dissolved in corn oil; the second female received an equivalent exposure of pure corn oil. Birds were released and their nestlings weighed. Parental care was again monitored between 18.00 and 20.00 hours on day 12 and 06.00 and 08.00 hours on day 13. Females were then captured and they with their young were weighed and killed. Changes in parental care in OP-dosed and control females were compared using paired t-tests. (3) The OP-dosed females made significantly (P < 0.05) fewer sorties to feed their young and remained away from their boxes for longer periods of time than controls. Nestlings of OP-treated females lost significantly more weight (X= 9-3%) than nestlings of controls (X= 3-2%). Brain ChE activity in OP-treated females was inhibited an average of 50.7% compared with controls. Weight changes in OP-dosed (X = -8.9%) and control females (X = -8.3%) were similar. (4) Results indicate that parental care may be significantly reduced in songbirds receiving severe but sublethal exposure to organophosphate pesticides. The potential for a reduction or modification in parental care to alter reproductive success in passerines is discussed. (5) Techniques utilized, or modifications thereof, may be useful in collecting the additional data needed to adequately assess the impact of OPs on songbird reproduction.

Lead concentrations in bullfrog Rana catesbeiana and green frog R. clamitans tadpoles inhabiting highway drainages

Abstract Lead concentrations were determined in sediment and tadpoles of bullfrogs Rana catesbeiana and green frogs R. clamitans from drainages along highways with different daily average traffic volumes (range, 4272 to 108 800 vehicles day−1) and from ponds ≥ 0·4 km from the nearest highway. Lead concentrations (mg kg−1 dry weight) in sediment (7·8 to 940) were usually greater (4–5 times) than those in the tadpoles (bullfrog, 0·07 to 270; green frog, 0·90 to 240 mg kg−1). Lead concentrations in sediment (r = 0·63) and in both species of tadpoles (bullfrog, r = 0·69; green frog, r = 0·57) were positively correlated with average daily traffic volume. Lead concentrations in both species of tadpoles (bullfrog, r = 0·76; green frog, r = 0·75) were also positively correlated with lead concentrations in sediment. At sites where both bullfrog and green frog tadpoles were collected, lead concentrations in the two species were closely related (r = 0·84). Lead concentrations in tadpoles living near highways may contribute to the elevated lead levels reported in wildlife that are potential tadpole predators. Dietary lead concentrations similar to those in our tadpoles have been associated with physiological and reproductive effects in some species of birds and mammals. However, additional data are needed to determine the hazards to predators of lead concentrations in tadpoles.

Sensitivity of nestling and adult starlings to dicrotophos, an organophosphate pesticide

The 24-hr median lethal dose (LD50) of dicrotophos (3-hydroxy-N,N-dimethyl-cis-crotonamide dimethyl phosphate) for free-living 5-day-old nestling European starlings (Sturnus vulgaris, LD50 = 4.92 mg/kg body wt) was about one-half that obtained for free-living 15-day-old nestlings (9.59 mg/kg) and captive adult males (8.37 mg/kg) and females (8.47 mg/kg). Nestlings and adults with low pretreatment body weights appeared to be more vulnerable to organophosphate (OP) exposure. Brain cholinesterase (ChE) activity was severely depressed in all birds that died (74-94%); the degree of inhibition did not vary with age or sex. Inhibition of brain ChE in 5-day-old nestlings alive 24 hr post dose (mean = 28-43%) was lower than that of 15-day-old (mean = 55-68%) and adult (mean = 55-77%) survivors. Body weights of OP-dosed birds that died were depressed an average of 20 to 46% in 5-day-olds, 7 to 20% in 15-day-olds, and 0 to 10% in adults; weight losses varied inversely with age and dosage, and directly with time to death. Average weight losses in 5- and 15-day-old survivors (mean less than or equal to 31 and 26%, respectively) varied directly with dose and exceeded comparable values for adults (mean = 3-15%). Results suggest that (1) young nestling songbirds may be nearly twice as sensitive as adults to OPs, (2) growth of nestlings may be severely depressed following OP exposure, and (3) recovery of brain ChE activity following exposure to ChE inhibitors may be more rapid in nestlings than adults.

Brain cholinesterase activity in fledgling starlings: Implications for monitoring exposure of songbirds to ChE inhibitors

Exposure of songbirds to organophosphate and carbamate pest ic ides is often determined by comparing the brain chol inesterase (ChE) a c t i v i t y of i nd i v i dua l s that have been exposed wi th that of unexposed bi rds of the same species (e .g . , see Busby et a l . 1981, 1982; Hamilton et a l . 1981). Knowledge of the normal pattern of ChE development in the brains of nes t l i ng and f l edg l i ng passerines is a necessary p re requ is i te for monitor ing exposure to ChE i n h i b i t o r s , and assessing the impacts of these i n h i b i t o r s on the reproduct ive success and surv iva l of songbirds. In a previous study, Grue et a l . (1981) reported tha t ChE a c t i v i t y in the brains of w i ld nes t l i ng European s t a r l i n g s (Sturnus v u l g a r i s ) , 3 to 18 days o ld , var ied s i g n i f i c a n t l y wi th age and appeared to increase toward adul t leve ls at a constant rate. Grue et a l . (1981) hypothesized that i f brain ChE a c t i v i t y continued to develop at a constant rate, leve ls in the brains of f l e d g l i n g s t a r l i n g s about 28 days old would be comparable to those in the brains of adu l ts . The present study was conducted to tes t t h i s hypothesis.

Correlation of Habitat Variables with Mourning Dove Call Counts in Texas

Habitat variables correlated with mourning dove (Zenaida macroura) call counts on 133 random transects differed between ecological areas. Whether or not a particular habitat variable was correlated with call counts appeared to depend upon the abundance and distribution of the other habitat types and structural features present. If 1 or more of the requisites for dove survival and reproduction (food, water, cover, nest sites) was limited, habitat types and structural features which provided them were usually positively correlated with call counts. Conversely, abundant habitat types which did not provide all of these requisites were usually negatively correlated with call counts. Results may be useful in improving habitat for breeding mourning doves within the Southeast, Great Plains, and Southwest. J. WILDL. MANAGE. 47(1):186-195 The mourning dove has the widest range of any game bird in the United States. It is the only one to nest in all contiguous 48 states and is the most important game bird species in North America in terms of numbers and hunter harvest (Keeler 1977). Management in the United States has been almost entirely restricted to control of harvest based on fluctuations in breeding populations monitored nationwide by call-count surveys (Dolton 1977). While some breeding populations have decreased (Dolton 1977), hunter harvest within the United States has increased to more than 49 million doves (Keeler 1977). If demand for use of the dove resource continues to increase, habitat management may become essential. Studies on the mourning dove that may be useful in establishing guidelines for management of its breeding habitat within a variety of vegetation types are lacking. Field studies have demonstrated the feasibility of using call counts to detect annual changes in mourning dove populations (Foote and Peters 1952). Each callcount transect consists of 20 listening points (3-min stops) at 1.6-km intervals along secondary roads (Dolton 1977). Population indices derived from these surveys are believed to be biologically and statistically sound for detecting annual changes in breeding dove densities (Dolton 1977). If the number of doves heard calling reflects the density of doves within the radius of audibility (50.8 km, Davey 1953), it may be possible to determine the habitat variables associated with different densities during the breeding season. The objective of our study was to identify those habitat variables correlated with dove densities obtained from call-count surveys. Texas was well suited for such a study because of its size and habitat diversity (Godfrey et al. 1967, Gould 1975). This research was funded by the U.S. Fish and Wildlife Service, the Caesar Kleberg Research Program in Wildlife Ecology, and the Agricultural Experiment Station, Texas A&M University, in cooperation with the Texas Parks and Wildlife Texas Agricultural Experiment Station Technical Article 14075. 2 Present address: Patuxent Wildlife Research Center, Laurel, MD 20708. 3 Present address: Espey-Huston and Associates, Austin, TX 78732. 186 J. Wildl. Manage. 47(1):1983 This content downloaded from 157.55.39.175 on Thu, 11 Aug 2016 06:14:16 UTC All use subject to http://about.jstor.org/terms HABITAT VARIABLES ON MOURNING DOVE CALL-COUNT ROUTES * Grue et al. 187 Department. We thank J. H. Dunks, J. T. Robertson, and other personnel of the Texas Parks and Wildlife Department for providing the call-count data, T. L. Blankenship, S. A. Cooper, and V. H. Silvy for help with the habitat surveys, C. M. Bunck for statistical assistance, and S. L. Beasom, C. E. Braun, F. E. Smeins, and W. G. Swank for review of the manuscript. This paper constitutes part of a dissertation by the senior author.