N. J. Silvy

From 1980-1981, we tested the hypothesis that removal of potential nest predators would increase the reproductive success of the endangered Attwater's prairie-chicken (Tympanuchus cupido attwateri). Striped skunks (Mephitis mephitis, N = 74), opossums (Didelphis virginiana, N = 83), and raccoons (Procyon lotor, N = 9) were removed from a 522-ha predator removal area (PR) during February- June 1980 and 1981. Predator indices were lower (P < 0.002) and prairie-chicken nest success was higher (82% vs. 33%, P < 0.019) in the PR than a 620-ha control area (CO). Breeding season hen...

Little information is available on the success of single-parent mourning dove (Zenaida macwura) nests after 1 September, the time period when hunting usually begins. To answer this question, data from single-parent nests were collected on the Texas A&M University Campus during September 1979. Data for 44 nests where 1 parent was removed were compared to 31 control nests. Success of single-parent nests with young 0-6 days of age was reduced. We did not observe significant reduction in success for nests containing young exceeding 6 days of age, or for single male versus single female...

Comparison of observed age at post-juvenal primary molt of wild mourning doves (Zenaida macroura) with predicted ages from 5 published aging studies revealed differences (P < 0.1) for all comparisons. Observed molt occurred at an older (P < 0.0001) age than predicted by the current standard for aging juvenile doves. A new model for aging mourning dove juveniles using molt data from primaries 1-9 is presented based on data collected from wild birds on the Texas A&M University Campus. The wide range in observed age at molt of primary 10 precluded its use in these analyses.

Two odor attractants, Carman's Distant Canine Call (CDCC) and W-U lure, were monitored simultaneously at scent-station transects in 5 units of the Big Thicket National Preserve, Texas. We examined transects for furbearer tracks for 3 consecutive days quarterly from January 1987 through March 1988. Significantly (X2 = 26.9, df = 1, P < 0.01) greater numbers of furbearers were attracted to scent stations with CDCC than to those with W-U lure. We recommend CDCC over W-U lure for attracting furbearers to scent stations in Southeastern pine habitats.

A known population density was established for northern bobwhites (Colinus virginianus) on a lOO-ha pasture. Line transects were walked twice/day for 5 days to obtain a density estimate. Twelve density estimators using the linetransect data were compared to the known bobwhite density. On our study area, 6 estimators overestimated bobwhite density and 6 of them underestimated density. Because few coveys were flushed, individual transect replicates had to be pooled to provide estimates. This pooling of replicates did not enable us to calculate a mean density and specific variances for each...

Scent-station and track-count transects were monitored simultaneously in 5 units of the Big Thicket National Preserve. We examined these transects for furbearer tracks for 3 consecutive days every 3 months from January 1987 through March 1988. Greater species diversity and species richness of furbearers were recorded on track-count surveys than on scent-station surveys on 4 of the 5 study units. The number of monitoring periods with no record of a species group was compared between the 2 techniques. Track-count surveys recorded "no presence" of a species group less often than scent-station...

A total of2,l89 pen-reared northern bobwhites (Colinus virginianus) was banded and released when 14 weeks old on a hunting club in north-central Texas from May 1984 through February 1985. Recovery of banded birds released during the 5 months preceding the hunting season was 7.5%, whereas 38.6% of birds released during the first 3 months of the hunting season were recovered compared to 55.4% of those released during the last 2 months. Release of birds just prior to the hunt decreased the cost per bird recovered to $6.5 as compared to $18.65 for birds released 14 days before the hunt.

White-tailed deer (Odocoileus virginianus) densities and sex ratios were determined during 2 seasons for a semiconfined population. Two drive counts were used to estimate deer densities when an entire area was traversed, once in early winter and once in summer. In addition to the 2 drive counts, 5 random transects, totaling 4.5 km, were walked 6 times (3 times in fall and 3 in summer). Eighteen different density estimators were calculated using the line transect data. Compared to the density estimates derived from drive counts, the Hayne Constant Radius estimator gave the most accurate...

Age ratios were determined for 361 gray squirrels (Sciurus carolinensis) and 130 fox squirrels (S. niger) taken on 50 ha in Northeast Texas during 5 weekend hunts. Data indicated that adults were more likely than young to be taken on the opening weekend. During weeks 2 and 3, young were more frequently taken while during weeks 4 and 5, adults were again taken more frequently. Results were inconsistent with the beliefs of most biologists and hunters who claim that young animals are more susceptible to the gun than are adults. Because of different vulnerability of adults and young squirrels...

Mourning dove (Zenaida macroura) nests were located on the Texas A&M University campus during the 1981-1982 nesting seasons. Daily survival rates, calculated using nests and individuals as units of analysis, were compared for eggs, nestlings, and eggs and nestlings combined. No difference (P > 0.05) was detected in any of the comparisons, indicating that equivalent data were obtained by knowing only the fate of the nest and not of individuals within the nest. Thus, disturbance at the nest can be minimized without loss of accuracy. Nest data tended to underestimate survival for eggs...