Geology topics

Jill A. Shaffer

Publications and source records attributed to Jill A. Shaffer.

60 records · Page 4Linked to original sources

USGS2005

Variability in vegetation effects on density and nesting success of grassland birds

The structure of vegetation in grassland systems, unlike that in forest systems, varies dramatically among years on the same sites, and among regions with similar vegetation. The role of this variation in vegetation structure on bird density and nesting success of grassland birds is poorly understood, primarily because few studies have included sufficiently large temporal and spatial scales to capture the variation in vegetation structure, bird density, or nesting success. To date, no large-scale study on grassland birds has been conducted to investigate whether grassland bird density and nesting success respond similarly to changes in vegetation structure. However, reliable management recommendations require investigations into the distribution and nesting success of grassland birds over larger temporal and spatial scales. In addition, studies need to examine whether bird density and nesting success respond similarly to changing environmental conditions. We investigated the effect of vegetation structure on the density and nesting success of 3 grassland-nesting birds: clay-colored sparrow (Spizella pallida), Savannah sparrow (Passerculus sandwichensis), and bobolink (Dolichonyx oryzivorus) in 3 regions of the northern tallgrass prairie in 1998-2001. Few vegetation features influenced the densities of our study species, and each species responded differently to those vegetation variables. We could identify only 1 variable that clearly influenced nesting success of 1 species: clay-colored sparrow nesting success increased with increasing percentage of nest cover from the surrounding vegetation. Because responses of avian density and nesting success to vegetation measures varied among regions, years, and species, land managers at all times need to provide grasslands with different types of vegetation structure. Management guidelines developed from small-scale, short-term studies may lead to misrepresentations of the needs of grassland-nesting birds.

Journal of Wildlife Management↗

USGS2005

A fresh look at the taxonomy of midcontinental sandhill cranes

The midcontinental population of sandhill crane ( Grus canadensis ) includes about 500,000 birds and provides valuable recreational crane-watching and hunting opportunities in Canada and the United States. It comprises three subspecies, one of which ( G. c. rowani ) was of uncertain taxonomic status and another of which ( G. c. tabida ) merited protection from excessive harvest due to its small population size. We obtained measurements of cranes used by Johnson and Stewart (1973) and additional crane specimens to 1) evaluate the subspecies designation of midcontinental sandhill cranes and 2) to seek improved methods for classifying cranes from selected measurements. We found that the three named subspecies are in fact morphologically distinct, although there is a general gradient of smaller birds breeding in the far north to larger birds breeding at more southerly latitudes. We were not able to find better ways of identifying subspecies; in particular we could not find a reliable method that did not require knowledge of the sex of an individual crane.

Conference Paper↗

USGS2003

Brown-headed cowbirds in grasslands: Their habitats, hosts, and response to management

The brown-headed cowbird ( Molothrus ater ) is an obligate brood parasite whose numbers have increased in recent decades to the potential detriment of the species that they parasitize. Thus, most management efforts focus on discouraging brown-headed cowbird parasitism or controlling brown-headed cowbird populations. Keys to discouraging cowbird parasitism or controlling populations of brown-headed cowbirds in the Great Plains are maintaining large expanses of grassland, eliminating foraging areas (e.g., feedlots) and perch sites, and reducing the extent of overgrazed pastures.

Prairie Naturalist↗

USGS2003

Status assessment and conservation plan for the Western Burrowing Owl in the United States

The Western Burrowing Owl ( Athene cunicularia hypugaea ) is a grassland specialist distributed throughout w. North America, primarily in open areas with short vegetation and bare ground in desert, grassland, and shrub-steppe environments. Burrowing Owls are dependent on the presence of fossorial mammals (primarily prairie dogs and ground squirrels), whose burrows are used for nesting and roosting. Burrowing Owls are protected by the Migratory Bird Treaty Act in the United States and Mexico. They are listed as Endangered in Canada and Threatened in Mexico. They are considered by the U.S. Fish and Wildlife Service (USFWS) to be a Bird of Conservation Concern at the national level, in three USFWS regions, and in nine Bird Conservation Regions . At the state level, Burrowing Owls are listed as Endangered in Minnesota, Threatened in Colorado, and as a Species of Concern in California, Montana, Oklahoma, Oregon, Utah, Washington, and Wyoming.

Biological Technical Publication↗

USGS2003

Historical and recent records and first nest records of Henslow's sparrow in North Dakota

The northwestern limit of the Henslow's sparrow ( Ammodramus henslowii ) breeding distribution occurs in southern Minnesota and central Wisconsin. In North Dakota, observations of Henslow's sparrows are reported infrequently, and there are no published nest records in the state. Herein, we summarize and review previous reports of Henslow's sparrows in North Dakota and document the first two nest records of Henslow's sparrow in the state.

North Dakota↗

USGS2003

Guidelines for finding nests of passerine birds in tallgrass prairie

The productivity of birds is one of the most critical components of their natural history affected by habitat quality. Birds might occur at high densities in a given habitat patch but have low nesting success. Such "population sinks" would not be detected if observers relied solely on estimates of bird density. Therefore, it is essential to monitor nests and determine their outcomes. Although interest in grassland-nesting passerines has increased greatly during the last decade, we still know little about factors affecting their nesting success. To stimulate more research in this area, we summarize several methods for nest-searching and provide suggestions for optimizing its success in tall grass prairie. As a case study, we provide some data from a study on grassland-nesting birds in the northern tallgrass prairie.

Prairie Naturalist↗