Walter M. Tzilkowski

Wildlife damage to corn in Pennsylvania: Farmer and on-the-ground estimates

Agricultural damage is a concern of farmers and agricultural and wildlife agencies at the state and federal levels. We compared questionnaire and independent on-the-ground sampling results to obtain estimates of wildlife-related damage to the 1995 corn crop in Pennsylvania, USA. We sampled 222 randomly selected cornfields (2.5 ± 0.65 ha; x ± SE) and the respective operators. Pennsylvania farmers reported an average of 33 ± 1.3 years of farming experience, 60% had >75% of their income from farming, and 49% were dairy farmers. They owned 125.4 ± 11.33 ha of which 55.8 ± 4.05 ha were planted in corn. Average corn yield was 7.31 m 3 /ha (84 bu/ac), which was negatively influenced by drought. Average wildlife-related loss was 0.48 m 3 /ha (5.5 bu/ac); white-tailed deer (Odocoileus virginianus) loss was 0.35 m 3 /ha (4.0 bu/ac). For 132 farms, we had the farmers (farm-wide) and the on-the-ground (field-specific) estimates of wildlife damage. The correlation between loss estimates (r = 0.263, P= 0.0013) was low. But no difference (t=1.30, P= 0.196) occurred between the mean estimates of corn loss (x ± SE) reported by farmers for the farm (9.68 ± 0.89%) and the on-the-ground estimate for a field (7.67 ± 1.27%).

Relative use of municipal street trees by birds during summer in state college, Pennsylvania

Relationships between street-tree characteristics, including habitat features, and use by urban birds were investigated from May to July 1980 in State College, Pennsylvania. Bird presence or absence was sampled in 1278 individual street trees of 24 species. Log-linear analysis of tree species, height class and bird occurence determined that pin oak (Quercus palustris), American elm (Ulmus americana) and honeylocust (Gleditsia triacanthos var. inermis) were used more frequently by birds (P<0.05), and there was a linear relationship between height class and bird occurrence. Relative use of tree species by a group of three exotic bird species was highly correlated with that of the remaining native bird species (P<0.01). Logistic-regression analyses of bird occurrence on 10 habitat variables and tree characteristics showed that tall street trees located in areas with little other deciduous tree cover were more attractive to both the native and exotic bird groups (P<0.05). In addition, native birds were observed more often in trees planted in residential areas with little vehicular traffic, whereas exotic birds were more frequent in business areas with greater traffic volume. Because of the interest in bird watching among urban residents, municipal arborists should be aware that street trees may differin their attractiveness to birds.

Site Fidelity and Lifetime Territorial Consistency of Ovenbirds (Seiurus aurocapilla) in a Contiguous Forest

ABSTRACT. We investigated territory-level habitat use patterns of 132 color-banded male Ovenbirds (Seiurus aurocapilla) over a 12-year period at Hawk Mountain Sanctuary in eastern Pennsylvania. Our primary goals were to test hypotheses concerning selection behavior as well as to describe territory fidelity of an area-sensitive Neotropical migrant by quantifying year-to-year movements of individuals over a period equivalent to several generations. Furthermore, we tested whether returns and territory shifts were associated with prior reproductive success and bird age. We measured occupancy as the number of birds that occupied 60-m grid cells that covered two 18-ha study sites over the 12-year period and similarly calculated rates of reproductive success within each grid cell. Rates of reproductive success were generally high (>60%) and were not correlated with occupancy rates. Return rates also were high, and birds rarely moved far from their first territory (mean = 68 m) during their lifetimes. There was no relationship between site fidelity and past reproductive success, but shift distances decreased with age. Our results differed from past studies that found a relationship between breeding dispersal and past reproductive success for species in a number of habitats. High territory fidelity regardless of past reproductive performance may represent a general case for songbirds breeding in homogeneous, high-quality habitats in which sources of failure are infrequent and unpredictable. In such cases, the potential benefit of moving may not outweigh the costs, and being able to obtain and maintain a territory may be of prime importance.

Relative Value of Vegetation Structure and Species Composition for Identifying American Woodcock Breeding Habitat

LUMSDEN, H. G., AND R. B. WEEDEN. 1963. Notes on the harvest of spruce grouse. J. Wildl. Manage. 27:589-591. MCCOURT, K. H. 1969. Dispersion and dispersal of female and juvenile Franklins grouse in southwestern Alberta. M.S. Thesis, Univ. Alberta, Edmonton. 137pp. McLACHLIN, R. A. 1970. The spring and summer dispersion of male Franklins grouse in lodgepole pine forest in southwestern Alberta. M.S. Thesis, Univ. Alberta, Edmonton. 153pp. RODGERS, R. D. 1979. Ratios of primary calamus diameters for determining age of ruffed grouse. Wildl. Soc. Bull. 7:125-127. ZWICKEL, F. C., AND C. F. MARTINSEN. 1967. Determining age and sex of Franklins spruce grouse by tails alone. J. Wildl. Manage. 31:706-763.

Effects of Liming on Forage Availability and Nutrient Content in a Forest Impacted by Acid Rain

Acidic deposition and subsequent forest soil acidification and nutrient depletion can affect negatively the growth, health and nutrient content of vegetation, potentially limiting the availability and nutrient content of forage for white-tailed deer (Odocoileus virginianus) and other forest herbivores. Liming is a mitigation technique that can be used to restore forest health in acidified areas, but little is known about how it affects the growth or nutrient content of deer forage. We examined the effects of dolomitic limestone application on the growth and chemical composition of understory plants in an acidified forest in central Pennsylvania, with a focus on vegetative groups included as white-tailed deer forage. We used a Before-After-Control-Impact study design with observations 1 year before liming and up to 5 years post-liming on 2 treated and 2 untreated 100-ha sites. Before liming, forage availability and several nutrients were below levels considered optimal for white-tailed deer, and many vegetative characteristics were related to soil chemistry. We observed a positive effect of liming on forb biomass, with a 2.7 fold increase on limed sites, but no biomass response in other vegetation groups. We observed positive effects of liming on calcium and magnesium content and negative effects on aluminum and manganese content of several plant groups. Responses to liming by forbs and plant nutrients show promise for improving vegetation health and forage quality and quantity for deer.

ALTERNATE DRUMMING SITE USE BY RUFFED GROUSE IN CENTRAL PENNSYLVANIA

Abstract We report on the use of alternate drumming sites by male Ruffed Grouse (Bonasa umbellus) during 1976–1997 within activity centers in a managed and an unmanaged forest in central Pennsylvania. Density of drumming males ranged from 1.6–12.5 males/km2 in the managed forest and from 1.7–7.6 males/km2 in the unmanaged forest. The proportion of males that used alternate drumming sites within activity centers ranged from 2% to 44% and was positively correlated with drumming male density. The number of alternate sites used within activity centers also increased with density; males used up to five alternate sites during a high-density year. Distances between alternate drumming sites and primary sites were not correlated with density but were greater on the unmanaged forest. The spatial orientation of multiple alternate sites relative to the primary site within each activity center suggested the use of alternate sites was a directional response. The actual direction of the response was not consistent among activity centers in the study area indicating it was not a result of prevailing abiotic factors such as wind, climate, or geomorphology. Similarly, the placement of alternate drumming sites was not directed toward nearest neighboring males. We discuss potential causes of the behavior, its adaptive significance, and implications to commonly used survey techniques for Ruffed Grouse populations.

Bimodality of the combined removal and signs-of-activities estimator for sampling closed animal populations

The possibility of a bimodal log-likelihood function arises with certain data when the combined removal and signs-of-activities estimator is used. Bimodal log-likelihoods may, in turn, yield disjoint confidence intervals for certain confidence levels. The hypothesis that bimodality is caused by the violation of the equal catchability assumption of the removal model, leading to the combination of contradictory data/models in the combined estimator is set forth. Simulations exploring the effect of the violation of removal model assumptions on estimation and inference showed that the assumption of unequal capture probability influenced the frequency of bimodal likelihoods; similarly, extreme parameter values for probability of capture influenced the number of excessively large confidence intervals produced. A sex-specific combined estimator is developed as a remedial model tailored to the problem. The simulations suggest that both the signs-of-activities estimator and the sex-specific estimator perform equally well over the range of simulations presented, though the signs-of-activities estimator is easier to implement.