Research Teams

Fire and Avian Ecology In North America

A Symposium for the Third International Partners in Flight Conference
23 March 2002, Asilomar, California

Organizer: Vicki Saab
 

Manuscripts in Preparation for Publication by Studies in Avian Biology
Abstracts:

HOW PROCESS INFLUENCES PATTERN: FIRE AND AVIAN COMMUNITIES IN NORTH AMERICA

V. A. Saab 1*, N.B. Kotliar 2, and W.M. Block3.

1USDA Forest Service, Rocky Mountain Research Station, Boise ID, 2U.S. Geological Survey, Fort Collins, CO, and 3 USDA Forest Service, Rocky Mountain Research Station, Flagstaff, AZ.

We summarize a symposium on fire and avian ecology, identifying patterns and differences in bird responses to various fire conditions in vegetative communities across North America, including boreal forests of Canada, grasslands and forests of northern Mexico, and within the United States - grasslands and shrublands in the Northeast; Eastern deciduous forests; pine-grasslands of the Southeast; tallgrass prairie of the Mid-west; shrubsteppe of the Interior West; deserts, grasslands, shrublands, and forests of the Southwest; coniferous forests of the Rocky Mountains, and California oak woodlands. Fire is an important ecological process in shaping vegetation structure, landscape patterns, and bird distributions throughout North America. The diversity of climate, topography, and vegetation across North America results in a wide range of natural fire regimes from small-scale, frequent, low-severity fires to large, infrequent, high-severity events. Historical fires differ from contemporary fire regimes in most cases, although historical fire regimes are not always well understood. Timing, frequency, intensity, and scale of fires have been altered by livestock grazing, timber harvest, the spread of invasive species, and fire suppression. Disruptions of natural fire regimes have not only led to alterations in landscape patterns and processes, but also to changes in population structure and the composition of bird communities.



TO BURN OR NOT TO BURN: EFFECTS OF FIRE AND MOWING ON GRASSLAND AND SHRUBLAND BIRDS IN NORTHEASTERN UNITED STATES

Peter D. Vickery*, Andrea L. Jones, and Benjamin Zuckerburg,

Dept. of Natural Resources Conservation, University of Massachusetts, Amherst, MA, USA.

Recently, grasslands and shrublands in northeastern North America have been maintained primarily with two types of habitat management: prescribed burning and mowing. The effects of these management practices differ in grasslands versus shrublands. In native grasslands, burning has a strong effect on the vegetation, which, in turn, affects a suite of grassland specialists. In Maine, densities of Savannah Sparrows (Passerculus sandwichensis), Grasshopper Sparrows (Ammodramus savannarum), Bobolinks (Dolichonyx oryzivorus), and Eastern Meadowlarks (Sturnella magna) declined for one year following fire but then maintained high densities for 5-7 years following fire. Horned Larks (Eremophila alpestris) and Vesper Sparrows (Pooecetes gramineus) preferred recently burned sites, and Upland Sandpipers (Bartramia longicauda) and Field Sparrows (Spizella pusiila) were unaffected by fire. On Nantucket Island, MA, Savannah Sparrow territory densities did not differ in grasslands that had been burned, mowed, or left unmanaged, but Song Sparrow (Melospiza melodia) densities were greater in unmanaged grasslands, and were lower in burned or mowed sites. Mowing of grasslands may be crucial for maintaining appropriate habitat, but early mowing has clear detrimental effects on grassland bird reproductive success because so many nests are destroyed in the process. On the shrublands of Nantucket Island, Eastern Towhees (Pipilo erythrophthalmus) were more abundant in areas that had been burned or were left unmanaged compared to shrublands that had been mowed. Conversely, Song Sparrow territory densities in shrublands were similar in mowed, burned, and unmanaged units. In general, these results indicate that burning has a strong affect in grassland systems but does not affect birds in shrublands. Not surprisingly, mowing has a more substantial affect on bird occupancy in shrubland habitats.



EFFECTS OF FIRE REGIME ON BIRDS IN VEGETATION COMMUNITIES OF THE SOUTHEAST

R. Todd Engstrom1*, Peter D. Vickery2, Dustin W. Perkins2, and W. Gregory Shriver3.

1Tall Timbers Research Station, 2University of Massachusetts-Amherst, and 3Syracuse University.

Fire, both natural and anthropogenic, has played a critical role in shaping vegetation structure and composition of virtually all of plant communities of the southeastern United States. Vegetation types of most southeastern physiographic regions have fire frequencies of 1 to 100 years, although particularly wet plant communities have lower frequencies. We provide a brief overview of disruptions to natural fire regimes, such as fire exclusion, vegetation fragmentation, alteration of season, hydrological disruption, and altered plant species composition (exotics and native), and how avian communities have been affected by those disruptions. We use case studies of selected bird species to discuss these issues. For example, prescribed fire is the primary management option to Florida dry prairies, which is habitat for the Florida Grasshopper Sparrow (Ammodramus savannarum floridanus). Until recently, most prescribed burns have been conducted in the dormant season (Oct-March) although historically wild fires occurred in May through July. For dormant season burns, densities and reproductive success of the Florida Grasshopper Sparrow were greater in areas that had been burned within the past 6 months compared to units that were 1.5 or 2.5 years post-burn. Grasshopper Sparrows on dormant burns generally stop singing by mid July. However, on plots where summer burns were conducted before mid June, sparrows continued to breed through August. To optimize dry prairie habitat for Florida Grasshopper Sparrows, summer burns should be conducted every 2-3 years.



FIRE ECOLOGY AND BIRD POPULATIONS IN EASTERN DECIDUOUS FORESTS

V. L. Artman*1, T. Hutchinson2, and J. D. Brawn3.

1 Kenyon College, Gambier, Ohio; 2 USDA Forest Service, Delaware, Ohio; 3 Illinois Natural History Survey, Champaign, Illinois.

Eastern deciduous forests are located across the central portion of eastern North America and provide habitat for approximately 126 bird species, including 59 Neotropical migratory species. The occurrence of fire in the region has been associated with the presence of humans for over 10,000 years. While pre-European fire regimes are poorly understood, fire is widely thought to have promoted and maintained the large expanses of oak forest and savanna documented in the original land surveys. Forest composition is gradually shifting from fire-adapted oaks to other species (e.g., maples) and suppression of fire has been implicated as a primary cause. Prescribed fire has been used successfully to restore and maintain oak savannas and it has been advocated to improve the sustainability of oak forests. Fire ecology research has addressed local scale or within-patch effects of prescribed burning on habitat structure, breeding bird populations, and nesting productivity. In the short–term, frequent burning creates less suitable conditions for mature forest birds that nest on the ground and in low shrubs but provides more favorable conditions for open-country birds associated with savanna habitats. The use of fire requires tradeoffs in terms of management and conservation because some bird species benefit from fire while others are negatively affected, depending on the degree to which fire changes habitat features. There is a critical need for long-term studies to better understand the effects of different fire regimes on bird populations in eastern deciduous forests.



BURNS, BIRDS AND THE BOREAL FOREST

S. J. Hannon1*, and P. Drapeau2.

1Dept of Biological Sciences, University of Alberta, Edmonton, AB; 2 Département de sciences biologiques, Université du Québec à Montréal, Montréal, QC.

Unlike many other ecosystems in North America, the boreal forest in Canada still retains a natural fire regime. However, the increasing importance of industrial forestry is changing this natural dynamic and its related bird communities. Because of these changes, discovering the difference between postfire and postharvest forests is becoming increasingly recognized as a key issue in the conservation of forest boreal birds. Even-aged management practices reinitiate forest succession as do stand-replacement fires, but they do not necessarily provide the same habitat conditions for birds. We present information on bird assemblages associated with burned stands in forests in the boreal plain and boreal shield regions of Canada. We compare these assemblages with those associated with harvested stands. Avian assemblages associated with recent burns are very different than those associated with recently logged stands, although the communities tend to converge as the stands age. Some species reach their highest abundances in recently burned stands; species we call “burn-dependent”. For example, black-backed woodpeckers exploit recent burns up to 8-10 years post-fire and then decline; they are rare in other age classes of forest. We evaluate how a natural-disturbance based management approach in the boreal forest can develop strategies to maintain burn-dependent species on harvested landscapes and highlight key research questions that remain to be answered.



FIRE REGIMES AND AVIAN RESPONSES IN THE CENTRAL TALLGRASS PRAIRIE

D.L. Reinking.

Sutton Avian Research Center, Bartlesville, OK.

Grasslands make up the largest vegetative province in North America, and one that has been significantly altered over the past two centuries. The tallgrass prairie of the eastern Great Plains and Midwest has declined to a greater extent than any other ecosystem, primarily due to plowing for cereal grain production. Grassland bird populations have declined at a greater rate and over a wider area than any other group of species. Historical fire regimes shaped and maintained the tallgrass prairie ecosystem. Both Indian-set and lighting-set fires were common, and probably differed in timing, frequency and scale from contemporary fire regimes, although historical regimes are not well understood. Fire affects both the composition and the structure of vegetation, and can affect birds in a variety of ways. Direct effects of fire on birds include destruction of nests, while indirect effects may involve changes to vegetation which favor some bird species over others. Management practices involving fire should operate on a scale consistent with area sensitivity requirements of various bird species, and with consideration of the direct and indirect effects of fire on the focal bird species. Availability of adequately-sized grasslands in a variety of seral stages is needed to ensure long-term population stability for the suite of bird species inhabiting tallgrass prairie.



Ecological restoration of pine forests and grasslands in northern Mexico: The role of prescribed burning

Jorge Nocedal1 and Patricia Manzano2.

1 Centro Regional Durango, INECOL; Durango, Dgo., 2 Agrupación Dodo; Toluca, Edo. Mex., México; and UNAM, Cd. Universitaria, México, DF,México.

An ecological restoration experiment on long-needled pine forests of NW Durango, in the Sierra Madre Occidental, will be performed to reestablish the original structure and function of these forested ecosystems. The region has an extraordinary biological diversity that has been severely damaged by the irrational exploitation and overuse of its resources and by the disruption of its natural disturbance regimes such as frequent and low intensity wild fires. Relatively few studies have been carried out to determine forest structure and disturbance regimes at the S.M.O. and most of the available data come from localities in the SW United States. Land use practices have altered the structure and function of these forests. Among the most evident modified features of these Madrean forests are the increase of sapling density and the accumulation of forest fuel, and, as a consequence, there has been an increase of high intensity and more destructive fires. One of the main objectives of this experimental approach is to measure the responses of bird communities to forest thinning and prescribed burning both during the breeding and wintering seasons. Mesquite scrub is expanding over former grasslands of northwestern Mexico and southwestern United States as a result of overgrazing. This homogenization of the landscape results in an impoverished biodiversity, but prairie dogs suppress the growth of mesquite and other woody plants maintaining the grassland as a defined habitat. The Janos area maintains a mosaic of prairie dog towns and mesquite scrub. As prairie dogs have been poisoned, mesquite has occupied the former grasslands. The Institute of Ecology of the National University of Mexico has been conducting research on the biodiversity of grasslands and scrubs of the area, and is starting a grassland restoration project. In order to recover grassland from mesquite and make habitat for grassland dependant species, the experimental use of prairie dogs and fire is being planned. Monitoring will assess the impact of these restoration techniques on the grassland bird community, depending on the results the use of fire could be extended to other areas.



FIRE ON THE MOUNTAIN: BIRDS AND BURNS IN THE ROCKIES

N.B. Kotliar1*, V. Saab2, and R.L. Hutto3.

1U.S. Geological Survey, 4512 McMurry Ave, Fort Collins, CO 80521, 2 U.S. Forest Service, Rocky Mountain Research Stn., 316 E. Myrtle St., Boise ID 83702, 3 Division of Biological Sciences, Univ. of Montana, Missoula, MT 59812.

The diversity of climate and topography across the Rocky Mountains results in a broad spectrum of fire regimes ranging from frequent, low-severity fires to infrequent stand-replacement events. There also is considerable variation within and among systems in this region in the degree of disruption of the natural fire regime by human activities (e.g., fire suppression, grazing, logging). Here we review the predominant fire regimes, highlighting the factors that contribute to variation within systems, and characterize avifaunal communities associated with various fire conditions. We emphasize ponderosa pine (Pinus ponderosa) systems because they have been targeted by recent fire initiatives to reduce fuel loads. These initiatives are based on the premise that millions of acres are susceptible to uncharacteristically large and severe wildland fires, due to decades of fire suppression. However, there are a number of untested assumptions about historic fire regimes and forest structure that affect the validity of the fire-management initiatives. Moreover, it is assumed that specific forest structures will ensure the integrity of natural communities (e.g., avian communities). Here, we evaluate the potential consequences of these assumptions for the ecological integrity of avian communities of the Rocky Mountains. Because the lack of information on the effects of fire on wildlife is a major stumbling block for developing ecologically sound fire management policies, we also identify critical information gaps to help direct further research.



FIRE AND BIRDS IN THE AMERICAN SOUTHWEST

Carl E. Bock*, University of Colorado, Boulder, Colorado, and William M Block, USDA Forest Service, Rocky Mountain Research Station, Flagstaff, Arizona.

Fire once was an important ecological force in most southwestern ecosystems, but historic frequencies and intensities have been altered by grazing, logging, exotic vegetation, and suppression. Prescribed burning should be applied widely, but under experimental conditions that facilitate studying its impacts on birds and other components of biodiversity. Exceptions are Sonoran and Mojave desertscrub and riparian woodlands that support high avian species richness, but where fire is destructive of most native vegetation. Fire plays a critical role in maintaining a balance between desert grassland and Chihuahuan desertscrub. A 3-5 yr. fire return interval likely will sustain most desert grassland birds, but large areas should remain unburned to serve birds dependent upon woody vegetation. Understory fire probably once played a critical role in maintaining relatively open oak savanna, pine-oak, and ponderosa pine forests and their bird assemblages, but current fuel conditions are more likely to result in stand-replacement fires outside the range of natural variation. Prescribed burning, thinning, and grazing management will be needed to return fire to its prehistoric role in these habitats. Fire also should be applied in mixed-conifer and spruce-fir forests to increase aspen stands that are important for many birds. Overall, surprisingly little is known about avian responses to southwestern fire, except as can be inferred from fire effects on vegetation. We call for a cooperative effort between managers and researchers to implement replicated burns in appropriate habitats that will permit rigorous study of community and population demographic responses of breeding, migrating, and wintering birds.



A birds-eye view of shrubsteppe fire ecology

Aaron L. Holmes*, Point Reyes Bird Observatory, Stinson Beach, CA. Richard Miller, Oregon State University, Corvallis, OR.

Natural fire regimes were spatially and temporally complex and dynamic within the sagebrush biome. Fire regimes varied from frequent (10-20 yrs) low intensity fires to infrequent (>70 yrs) higher intensity fires. Decadent, and often, degraded shrub communities dominate much of the Great Basin today as a result of livestock grazing and intensive fire suppression. Reduced fire frequency has also resulted in woodland encroachment, especially at mesic locations. Many species of birds, particularly those associated with the herbaceous understory have suffered long-term declines. Managing with fire is conceptually attractive because it is a natural disturbance in the sagebrush ecosystem with the potential to renew wildlife habitat. However, cheatgrass (Bromus tectorum), a widely distributed exotic annual poses a great challenge to re-introducing fire, especially in xeric locations. Cheatgrass can alter fire regimes and truncate community succession, sometimes precluding re-establishment of big sagebrush. In this paper we summarize the literature pertaining to natural fire regimes, their disruptions, and bird community response to fire within the sagebrush biome. We conclude that low-to-moderate intensity fires that create mosaic stands with multiple seral stages are desirable to maintain habitat for bird populations at a landscape scale. However, prescribed fire or unsuppressed wildfire is not appropriate on deteriorated sites susceptible to domination by exotics. Priority issues for management are to 1) identify thresholds related to woodland encroachment and fire regimes in shrubsteppe communities and 2) classify sites into low, medium, and high risk for cheatgrass invasion following fire.



Natural and anthropogenic fire regimes, vegetation effects, and potential impacts on the avifauna of California oak woodlands

K.L. Purcell*, USDA Forest Service, Pacific Southwest Research Station, Fresno, CA, and S.L. Stephens, University of California, Division of Forest Science, Environmental Science, Policy, and Management Department, Berkeley, CA.

We review existing information on past fire regimes in oak woodlands of California and predict avian response to habitat resulting from fire and fire suppression. Although little fire history work has been done in oak woodlands, ethnological and historical accounts provide information on past burning practices. Native Americans have used fire as a vegetation management tool for at least 3000 years, although there is not widespread agreement whether burning by California Indians were a significant factor in modifying vegetation. Fire frequency increased following Euro-American settlement in the mid-1850s until fire suppression became the rule in the 1940s. Fire reduces shrub cover, numbers of snags, and tree density, and increases habitat patchiness. Habitat used by Western Kingbirds, Western Bluebirds, Violet-green Swallows, and grassland species increases with shorter fire intervals while species preferring dense woodlands may be negatively impacted. If fire produces a mosaic of habitat patches, we expect most species’ habitat needs will be provided for. Grazing may mimic fire in some respects, particularly in reducing the woody understory, although other aspects remain unstudied.