R. Randy Wilson

Acadian flycatcher nest placement: Does placement influence reproductive success?

We located 511 Acadian Flycatcher (Empidonax virescens) nests in bottomland hardwood forest of eastern Arkansas. Microhabitat characteristics were measured and their relationship with nest success evaluated. Fifty-two percent of all nesting attempts resulted in predation. Attributes of nest placement were similar between successful and unsuccessful nests, although successful nests were placed higher. Similarly, nonparasitized nests were typically higher than parasitized nests. Nests initiated late in the breeding season were placed in larger trees with higher canopy bases resulting in increased vegetation around the nest. Fifteen different tree species were used for nesting. Acadian Flycatchers chose nest trees in a nonrandom fashion, selecting Nuttall oak (Quercus nuttallii) and possumhaw (Ilex decidua) in greater proportions than their availability. However, there was no relationship between tree species used for nesting and nest success. Nest height was positively correlated with concealment at the nest site, supporting the predator-avoidance theory. No other attribute of nest placement differentiated successful nest sites, suggesting that nest predation is likely a function of random events in space and time.

The Role of the Wetland Reserve Program in Conservation Efforts in the Mississippi River Alluvial Valley

Abstract The Mississippi River Alluvial Valley includes the floodplain of the Mississippi River from Cairo, Illinois, USA, to the Gulf of Mexico. Originally this region supported about 10 million ha of bottomland hardwood forests, but only about 2.8 million ha remain today. Furthermore, most of the remaining bottomland forest is highly fragmented with altered hydrologic processes. During the 1990s landscape-scale conservation planning efforts were initiated for migratory birds and the threatened Louisiana black bear (Ursus americanus luteolus). These plans call for large-scale reforestation and restoration efforts in the region, particularly on private lands. In 1990 the Food, Agriculture, Conservation and Trade Act authorized the Wetlands Reserve Program (WRP). The WRP is a voluntary program administered by the United States Department of Agriculture that provides eligible landowners with financial incentives to restore wetlands and retire marginal farmlands from agricultural production. As of 30 September 2005, over 275,700 ha have been enrolled in the program in the Mississippi River Alluvial Valley, with the greatest concentration in Louisiana, Arkansas, and Mississippi, USA. Hydrologic restoration is common on most sites, with open-water wetlands, such as moist-soil units and sloughs, constituting up to 30% of a given tract. Over 33,200 ha of open-water wetlands have been created, potentially providing over 115,000,000 duck-use days. Twenty-three of 87 forest-bird conservation areas have met or exceed core habitat goals for migratory songbirds and another 24 have met minimum area requirements. The WRP played an integral role in the fulfillment of these goals. Although some landscape goals have been attained, the young age of the program and forest stands, and the lack of monitoring, has limited evaluations of the programs impact on wildlife populations.

Nest survival of forest birds in the Mississippi alluvial valley

In the Mississippi Alluvial Valley, flood control has led to a drastic reduction in the area of forest habitat and altered the patchwork of forest cover types. Silvicultural management of the remaining fragmented forests has changed to reflect the altered hydrology of the forests, current economic conditions of the area, and demand for forest products. Because forest type and silvicultural management impact forest birds, differences in avian productivity within these forests directly impact bird conservation. To assist in conservation planning, we evaluated daily nest survival, nest predation rates, and brood parasitism rates of forest birds in relation to different forest cover types and silvicultural management strategies within this floodplain. Within bottomland hardwood forests, nest success of blue-gray gnatcatcher (Polioptila caerulea, 13%), eastern towhee (Pipilo erythrophthalmus, 28%), indigo bunting (Passerina cyanea, 18%), northern cardinal (Cardinalis cardinalis, 22%), and yellow-billed cuckoo (Coccyzus americanus, 18%) did not differ from that within intensively managed cottonwood plantations. However, average daily survival of 542 open-cup nests of 19 bird species in bottomland hardwoods (0.9516 ± 0.0028, ∼27% nest success) was greater than that of 543 nests of 18 species in cottonwood plantations (0.9298 ±0.0035, ∼15% nest success). Differences in daily nest survival rates likely resulted from a combination of differences in the predator community-particularly fire ants (Solenopsis invicta)-and a marked difference in species composition of birds breeding within these 2 forest types. At least 39% of nests in bottomland hardwood forests and 65% of nests in cottonwood plantations were depredated. Rates of parasitism by brown-headed cowbirds (Molothrus ater) were greater in managed cottonwoods (24%) than in bottomland hardwoods (9%). Nest success in planted cottonwood plantations for 18 species combined (∼14%), and for yellow-breasted chat (Icteria virens, 7%), eastern towhee (14%), indigo bunting (14%), and northern cardinal (17%) did not differ from nest success in cottonwood plantations that were coppiced from root sprouts following pulpwood harvest. Within bottomland hardwood forests, uneven-aged group-selection timber harvest reduced the combined daily nest survival of all species from 0.958 to 0.938, which reduced nest success by about 14%. Specifically, timber harvest reduced nest success of species that nest in the forest midstory and canopy, such as Acadian flycatcher (Empidonax virescens)-from 32% before harvest to 14% after harvest. Conversely, those species that nest primarily in the shrubby understory-such as northern cardinal-were not affected by timber harvest and maintained an overall nest success of about 33%. Thus, birds nesting in the understory of bottomland hardwood forests are not adversely impacted by selective timber harvest, but there is a short-term reduction in nest success for birds that nest in the canopy and midstory.

Spatial models of northern bobwhite populations for conservation planning

Abstract Since 1980, northern bobwhite (Colinus virginianus) range-wide populations declined 3.9% annually. Within the West Gulf Coastal Plain Bird Conservation Region in the south-central United States, populations of this quail species have declined 6.8% annually. These declines sparked calls for land use change and prompted implementation of various conservation practices. However, to effectively reverse these declines and restore northern bobwhite to their former population levels, habitat conservation and management efforts must target establishment and maintenance of sustainable populations. To provide guidance for conservation and restoration of habitat capable of supporting sustainable northern bobwhite populations in the West Gulf Coastal Plain, we modeled their spatial distribution using landscape characteristics derived from 1992 National Land Cover Data and bird detections, from 1990 to 1994, along 10-stop Breeding Bird Survey route segments. Four landscape metrics influenced detections of northern bobwhite: detections were greater in areas with more grassland and increased aggregation of agricultural lands, but detections were reduced in areas with increased density of land cover edge and grassland edge. Using these landscape metrics, we projected the abundance and spatial distribution of northern bobwhite populations across the entire West Gulf Coastal Plain. Predicted populations closely approximated abundance estimates from a different cadre of concurrently collected data but model predictions did not accurately reflect bobwhite detections along species-specific call-count routes in Arkansas and Louisiana. Using similar methods, we also projected northern bobwhite population distribution circa 1980 based on Land Use Land Cover data and bird survey data from 1976 to 1984. We compared our 1980 spatial projections with our spatial estimate of 1992 populations to identify areas of population change. Additionally, we used our projection of the spatial distribution and abundance of bobwhite to predict areas of population sustainability. Our projections of population change and sustainability provide guidance for targeting habitat conservation and rehabilitation efforts for restoration of northern bobwhite populations in the West Gulf Coastal Plain.

Does Nonrandom Nest Placement Imply Nonrandom Nest Predation?: a Reply

In response to the critique by Schmidt and Whelan (1999), we find that the relationship between nest success and tree selectivity is dependent upon inclusion or exclusion of particular tree species, whether or not years are pooled, and the selectivity index used. We question their use of point estimates of nest success with extremely high variances, defend our index, question the application of the Chesson (1983) index to our data, and explain the need to analyze years separately. Bottomland hardwood forest systems are extremely variable; hydroperiods alter the suitability of nesting substrates, availability of alternative food, and behavior of predators and their prey. Given these features, actively searching for Acadian Flycatcher (Empidonax virescens) nests is seldom an efficient predator foraging strategy. Therefore, these predation events are best described as random; nests are principally encountered opportunistically by generalist predators while searching for other prey.

Effects of Timber Harvest and Other Factors on a Floodplain Forest Indicator Species, the Prothonotary Warbler

Ecosystem approaches to management require monitoring of processes and species indicative of the integrity of the system in order to understand the effects of management and other perturbations. We examined the effects of three timber harvest options (single-tree selection, patch cuts, no harvest) on the reproductive biology of a possible indicator of bottomland forest ecosystem integrity, the prothonotary warbler (Protonotaria citrea). Timber harvests reduced the number of available nest cavities, reduced the density of breeding males on the plots, and increased the sizes of male territories. However, timber harvest had no obvious effect on nest predation or brood parasitism frequencies. Brood parasitism was instead related to distance from a nearby levee, a main source of brown-headed cowbirds (Molothrus ater) in the area. Productivity remained similar within suitable habitat regardless of treatment. Reproductive success was strongly influenced by annual variation, which we attribute to the timing and extent of annual flooding, a fundamental ecosystem process in floodplain forests. Continued anthropogenic alterations in flooding patterns may have a greater influence than current timber management on the future population levels of prothonotary warblers in the Mississippi Alluvial Valley. This species, with others, could play a valuable role in an ecosystem-oriented monitoring program.

Data on birds and habitat associated with forest management on public conservation areas in the Mississippi Alluvial Valley

This data article contains data collected from 2006–2012 in forests located on 31 State or Federal conservation lands in or adjacent to the Mississippi Alluvial Valley. We present the location, treatment type, and silvicultural age of data collection locations. Presented data on bird detections and forest habitat were collected during avian point counts and associated forest habitat plots and linked to the publication (D.J. Twedt and R.R. Wilson, 2017) [5].

Summer use of Rice Fields by Secretive Marsh Birds in the Mississippi Alluvial Valley of Northeast Louisiana

Abstract Many secretive marsh bird (SMB) species nest within rice fields, yet in most regions we do not understand the extent to which these birds use such habitats. In the summers of 2007 and 2008, we investigated summer use of rice fields by SMBs in northeast Louisiana and evaluated the local (within 100 m) and landscape (within 1 km) habitat characteristics influencing site selection. We did not encounter any SMB species in 2007, but we encountered low densities of Ixobrychus exilis (Least Bitterns), Rallus elegans (King Rails), and Fulica americana (American Coots) in mid-July of 2008. It is unclear whether or not the birds we detected were actually breeding in the rice fields, or merely using them as late summer foraging areas. When we combined detections of all species, we found that probability of occupancy was positively influenced by the proportion of the local habitat dominated by flooded ditches containing herbaceous emergent vegetation. Ditches likely provide refuge and resource alternatives that may be particularly important to these birds in the late summer when rice fields are drained and harvested. However, given that SMBs were detected at less than 10% of the 72 rice fields we surveyed, it appears as though Mississippi Alluvial Valley rice fields contribute very little toward supporting SMB populations.