W. Gregory Shriver

Impact of Native Plants on Bird and Butterfly Biodiversity in Suburban Landscapes

Managed landscapes in which non-native ornamental plants are favored over native vegetation now dominate the United States, particularly east of the Mississippi River. We measured how landscaping with native plants affects the avian and lepidopteran communities on 6 pairs of suburban properties in southeastern Pennsylvania. One property in each pair was landscaped entirely with native plants and the other exhibited a more conventional suburban mixture of plants--a native canopy with non-native groundcover and shrubs. Vegetation sampling confirmed that total plant cover and plant diversity did not differ between treatments, but non-native plant cover was greater on the conventional sites and native plant cover was greater on the native sites. Several avian (abundance, species richness, biomass, and breeding-bird abundance) and larval lepidopteran (abundance and species richness) community parameters were measured from June 2006 to August 2006. Native properties supported significantly more caterpillars and caterpillar species and significantly greater bird abundance, diversity, species richness, biomass, and breeding pairs of native species. Of particular importance is that bird species of regional conservation concern were 8 times more abundant and significantly more diverse on native properties. In our study area, native landscaping positively influenced the avian and lepidopteran carrying capacity of suburbia and provided a mechanism for reducing biodiversity losses in human-dominated landscapes.

Monitoring and evaluating the ecological integrity of forest ecosystems

“Ecological integrity” provides a useful framework for ecologically based monitoring and can provide valuable information for assessing ecosystem condition and management effectiveness. Building on the related concepts of biological integrity and ecological health, ecological integrity is a measure of the composition, structure, and function of an ecosystem in relation to the system’s natural or historical range of variation, as well as perturbations caused by natural or anthropogenic agents of change. We have developed a protocol to evaluate the ecological integrity of temperate zone, forested ecosystems, based on long-term monitoring data. To do so, we identified metrics of status and trend in structure, composition, and function of forests impacted by multiple agents of change. We used data, models, and the scientific literature to interpret and report integrity using “stoplight” symbology, ie “Good” (green), “Caution” (yellow), or “Significant Concern” (red). Preliminary data indicate that forested ecosystems in Acadia National Park have retained ecological integrity across a variety of metrics, but that some aspects of soil chemistry and stand structure indicate potential problems. This protocol was developed for the National Park Service Vital Signs Monitoring Program and holds promise for application in the temperate zone, forested ecosystems of eastern North America.

Effects of Traffic Noise on Occupancy Patterns of Forest Birds

Noise may drive changes in the composition and abundance of animals that communicate vocally. Traffic produces low-frequency noise (<3 kHz) that can mask acoustic signals broadcast within the same frequency range. We evaluated whether birds that sing within the frequency range of traffic noise are affected by acoustic masking (i.e., increased background noise levels at the same frequency of vocalizations reduce detection of vocalization) and are less abundant in areas where traffic noise is loud (44-57 dB). We estimated occupancy, the expected probability that a given site is occupied by a species, and detection probabilities of eight forest-breeding birds in areas with and without traffic noise as a function of noise and three measures of habitat quality: percent forest cover, distance from plot center to the edge of forest, and the number of standing dead trees or snags. For the two species that vocalize at the lowest peak frequency (the frequency with the most energy) and the lowest overall frequency (Yellow-billed Cuckoo [Coccyzus americanus] and White-breasted Nuthatch [Sitta carolinensis]), the presence of traffic noise explained the greatest proportion of variance in occupancy, and these species were 10 times less likely to be found in noisy than in quiet plots. For species that had only portions of their vocalizations overlapped by traffic noise, either forest cover or distance to forest edge explained more variation in occupancy than noise or no single variable explained occupancy. Our results suggest that the effects of traffic noise may be especially pronounced for species that vocalize at low frequencies.

Prevalence of Campylobacter in wild birds of the mid-Atlantic region, USA.

We evaluated the occurrence of three Campylobacter species—C. jejuni, C. coli, and C. lari—from 333 wild bird fecal samples collected at Tri-State Bird Rescue and Research in Newark, Delaware, in 2008. Using multiplex polymerase chain reaction, we detected C. jejuni from six avian families with an overall prevalence rate of 7.2%. We did not detect any other Campylobacter species. Cam-pylobacter jejuni prevalence ranged widely between different avian families with crows (Corvidae) and gulls (Laridae) having the highest prevalence rates (23% and 25%, respectively).

A sampling design framework for monitoring secretive marshbirds

Abstract. A framework for a sampling plan for monitoring marshbird populations in the contiguous 48 states is proposed here. The sampling universe is the breeding habitat (i.e. wetlands) potentially used by marshbirds. Selection protocols would be implemented within each of large geographical strata, such as Bird Conservation Regions. Site selection will be done using a two-stage cluster sample. Primary sampling units (PSUs) would be land areas, such as legal townships, and would be selected by a procedure such as systematic sampling. Secondary sampling units (SSUs) will be wetlands or portions of wetlands in the PSUs. SSUs will be selected by a randomized spatially balanced procedure. For analysis, the use of a variety of methods as a means of increasing confidence in conclusions that may be reached is encouraged. Additional effort will be required to work out details and implement the plan.

Spatial Dynamics of Source-Sink Habitats: Effects on Rare Grassland Birds

Fragmentation and edge effects adversely affect passerines in North America, primarily by reducing territory density, reproductive success, and survival. As natural landscapes become increasingly altered and fragmented by human development, understanding the demographic parameters of remaining subpopulations is important. We wanted to determine whether remaining dry prairie fragments in central Florida, USA, were acting as population sources or sinks for 2 rare and declining sparrows: the federally endangered Florida grasshopper sparrow (Ammodramus savannarum floridanus) and the regionally threatened Bachurans sparrow (Aimophila aestivalis). We obtained sparrow survival estimates from 2 sites in central Florida and combined these with productivity estimates from 3 sites (1996-1998) to determine whether each site was acting as a sourer or sink. We also explored whether subunits within a site consistently functioned as sources. For Florida grasshopper sparrows, we found that core areas >400 m from edge were consistently sources. We think that the only was Florida grasshopper sparrows can persist at these sites is if the core source areas produce enough surplus young to compensate for the sink habitat along the wide borders of these prairie fragments. In contrast to grasshopper sparrows, we found no consistent source areas for Bachmans sparrows. Dry prairie seems to lie sink habitat for Bachmans sparrows, and this species is likely to persist in this habitat only through continued recruitment from adjacent long-leaf pine (Pinus palustris) stands. We think that large prairie fragments, possibly >4,000 ha, are necessary for maintaining source habitat for Florida grasshopper sparrows and possibly other grassland bird species.

Response of breeding Florida grasshopper and Bachman's sparrows to winter prescribed burning

Populations of Florida grasshopper (Ammodramus savannarum floridanus) and Bachmans sparrows (Aimophila aestivalis) are small and declining. Prescribed burning is the primary management tool used to maintain their grassland habitats, but the effects of this management practice on the breeding density and reproductive success of these populations are poorly understood. We conducted a 3-year spot-mapping study of 3 winter burn classes (0.5-yr, 1.5-yr, and 2.5-yr postfire) in native dry prairie on 2 sites in central Florida to determine the effects of fire management on breeding density and reproductive success of these 2 sparrows. Florida grasshopper sparrow densities were greater on recently burned plots (0.5 yr postburn: x = 4.0 ± 1 territories/10 ha (x ± SE); 1.5 yr postburn x = 3.4 ± 0.8 territories/10 ha) than on plots that had not been burned in 2.5 years (x = 1.8 ± 0.8 territories/10 ha). Grasshopper sparrow reproductive success was also higher in recently burned plots (0.5 yr postburn; x = 1.6 successful territories/plot) than in 2.5-year burn plots (x = 0.6 successful territories/plot). In contrast, Bachman sparrow breeding densities and reproductive success were not affected by fire management rotation. Our results indicate that a fire rotation of ≤3 years is necessary to maintain suitable breeding habitat for Florida grasshopper sparrows but does not appear to negatively affect breeding Bachmans sparrows.

Mercury in Sharp-Tailed Sparrows Breeding in Coastal Wetlands

Current levels of anthropogenic mercury (Hg) in the environment can cause harm to humans and wildlife. Well-documented negative effects on birds are described, but there is presently limited information for passerine exposure to mercury. Some investigations have used insect-eating birds as potential bioindicators of mercury exposure. However, our understanding of methlymercury (MeHg) availability to birds in coastal wetlands, tidal systems that may be especially conducive to Hg methylation, remains poor. Two species of sharp-tailed sparrow breed in coastal wetlands in eastern North America and are suitable candidate indicators for contaminants in these habitats. We measured blood Hg from breeding Saltmarsh (Ammodramus caudacutus) and Nelson’s (Ammodramus nelsoni) sharp-tailed sparrows in five Maine salt marshes to determine if these species could be used to assess the extent of MeHg availability in salt marshes. Blood Hg for both species differed among the five marshes with concordance between species and...

REDEFINING RANGE OVERLAP BETWEEN THE SHARP-TAILED SPARROWS OF COASTAL NEW ENGLAND

Abstract With the designation of Nelsons Sharp-tailed Sparrow (Ammodramus nelsoni) and Saltmarsh Sharp-tailed Sparrow (A. caudacutus) as species of high conservation priority in the northeastern United States, the need to document fully their abundance, distribution, and the extent of range overlap has become increasingly important. We surveyed saltmarshes in coastal New England for both species from 1997 to 2000. The current overlap zone extends from Parker River, Massachusetts, north to Weskeag River, Maine, which expands the previously reported range overlap of 48 km to 208 km. Among the 49 sites surveyed within the current overlap zone, both species were present at 25 sites. It is possible that the species have experienced range expansion over the last several decades, especially the Nelsons Sharp-tailed Sparrow. Our findings indicate that the nominate subspecies of the Saltmarsh Sharp-tailed Sparrow warrants the greatest conservation concern given its limited geographic range, a potentially expanding hybrid zone with A. n. subvirgatus, and the potential for habitat degradation from an oil spill associated with the urban/industrial centers of the Northeast.

CONCORDANCE BETWEEN MORPHOLOGICAL AND MOLECULAR MARKERS IN ASSESSING HYBRIDIZATION BETWEEN SHARP-TAILED SPARROWS IN NEW ENGLAND

Abstract Hybridization is pivotal in framing ideas about species concepts and has the potential to produce novel genotypes that may serve as starting points for new evolutionary trajectories. Presently, Nelson’s Sharp-tailed Sparrows (Ammodramus nelsoni subvirgatus) and Saltmarsh Sharp-tailed Sparrows (A. caudacutus caudacutus) are in contact in salt marshes of Maine, New Hampshire, and northern Massachusetts. These two species hybridize, but the extent and direction of introgression has not been determined. We assessed morphological and genetic variation of 123 sharp-tailed sparrows from 5 salt marshes in New England. We used six morphological variables, including a plumage-scoring index, and five mic-rosatellite primers to assess the extent of introgression and to determine whether there was concordance between phenotypic and genotypic variation. We identified apparent hybrids and each of the two sharp-tailed sparrow species using a plumagescoring index. In general, we found that hybrids were more similar morphologically and genetically to Saltmarsh Sharp-tailed Sparrows. The alleles of hybrids were 62% Saltmarsh and 38% Nelson’s Sharp-tailed Sparrows, supporting the asymmetrical hybridization hypothesis. Concordancia entre Marcadores Morfológicos y Moleculares al Evaluar la Hibridación entre Ammodramus nelsoni subvirgatus y A. caudacutus caudacutus en Nueva Inglaterra