Stephen DeStefano

Exploring the ecology of suburban wildlife

The fringes of cities, and rural properties within commuting distance of cities, experience some of the highest rates of development in the world. This can cause dramatic changes to the landscape, the alteration of ecological functions, and a reduction in biodiversity. With the spread of suburbia, however, come opportunities for some species to exploit new resources. While many wild creatures can enrich the lives of suburban dwellers, large increases in the populations of species such as deer, beaver, and coyotes can lead to a change in status from resource to pest. For several decades, wildlife managers have alternately embraced and ignored issues related to urban and suburban wildlife. Today, management of suburban areas challenges wildlife agencies on two fronts: the threat to habitat and biodiversity and the problem of “overabundant” wildlife. This is not only a tremendous management challenge, but also an educational opportunity to help people understand the natural world and their place in it.

Scrub-shrub bird habitat associations at multiple spatial scales in beaver meadows in Massachusetts.

Abstract.— Most scrub-shrub bird species are declining in the northeastern United States, and these declines are largely attributed to regional declines in habitat availability. American Beaver (Castor canadensis; hereafter “beaver”) populations have been increasing in the Northeast in recent decades, and beavers create scrub-shrub habitat through their dam-building and foraging activities. Few systematic studies have been conducted on the value of beaver-modified habitats for scrub-shrub birds, and these data are important for understanding habitat selection of scrub-shrub birds as well as for assessing regional habitat availability for these species. We conducted surveys in 37 beaver meadows in a 2,800-km2 study area in western Massachusetts during 2005 and 2006 to determine the extent to which these beaver-modified habitats are used by scrub-shrub birds, as well as the characteristics of beaver meadows most closely related to bird use. We modeled bird abundance in relation to microhabitat-, patch-, and landscape-context variables while adjusting for survey-specific covariates affecting detectability using N-mixture models. We found that scrub-shrub birds of regional conservation concern occupied these sites and that birds responded differently to microhabitat, patch, and landscape characteristics of beaver meadows. Generally, scrub-shrub birds increased in abundance along a gradient of increasing vegetation complexity, and three species were positively related to patch size. We conclude that these habitats can potentially play an important role in regional conservation of scrub-shrub birds and recommend that conservation priority be given to larger beaver meadows with diverse vegetation structure and composition.

Prevalence of Microsporidia, Cryptosporidium spp., and Giardia spp. in beavers (Castor canadensis) in Massachusetts

Abstract Feces from 62 beavers (Castor canadensis) in Massachusetts were examined by fluorescence microscopy (IFA) and polymerase chain reaction (PCR) for Microsporidia species, Cryptosporidium spp., and Giardia spp. between January 2002 and December 2004. PCR-positive specimens were further examined by gene sequencing. Protist parasites were detected in 6.4% of the beavers. All were subadults and kits. Microsporidia species were not detected. Giardia spp. was detected by IFA from four beavers; Cryptosporidium spp. was also detected by IFA from two of these beavers. However, gene sequence data for the ssrRNA gene from these two Cryptosporidium spp.–positive beavers were inconclusive in identifying the species. Nucleotide sequences of the TPI, ssrRNA, and β-giardin genes for Giardia spp. (deposited in GenBank) indicated that the four beavers were excreting Giardia duodenalis Assemblage B, the zoonotic genotype representing a potential source of waterborne Giardia spp. cysts.

Lead fishing weights and other fishing tackle in selected waterbirds

Abstract From 1995 through 1999, 2,240 individuals of 28 species of waterbirds were examined in the United States for ingested lead fishing weights. A combination of radiography and visual examination of stomachs was used to search for lead weights and blood and liver samples from live birds and carcasses, respectively, were collected for lead analysis. Ingested lead weights were found most frequently in the Common Loon (Gavia immer) (11 of 313 = 3.5%) and Brown Pelican (Pelecanus occidentalis) (10 of 365 = 2.7%), but also in one of 81 (1.2%) Double-crested Cormorants (Phalacrocorax auritus) and one of 11 (9.1%) Black-crowned Night Herons (Nycticorax nycticorax). Birds with ingested lead fishing weights (including split shot, jig heads, and egg, bell, and pyramid sinkers) were found in California, Florida, Maine, New Hampshire, North Carolina, and Wisconsin. The size and mass of ingested lead weights ranged from split shot of 7 mm in the longest dimension, weighing less than 2 g, to a 22 × 39 mm pyramid sinker that weighed 78.2 g. Six ingested lead weights were more than 25.4 mm in the longest dimension. Lead concentrations in the blood and liver of birds with lead fishing weights in their stomachs ranged up to 13.9 ppm and 26.0 ppm (wet weight basis), respectively. During the study, we also noted the presence of ingested or entangled fishing tackle, with no associated lead weights, in eight species.

Relative importance of early-successional forests and shrubland habitats to mammals in the northeastern United States

The majority of the 60 native terrestrial mammal species that reside in the northeastern United States (US) utilize resources from several habitats on a seasonal basis. However, as many as 20 species demonstrate some preference for early-successional forests, shrublands, or old-field habitats. A few of these (e.g. lagomorphs) can be considered obligate users of these habitats, and the specialist carnivores (e.g. felids) that prey on them may consequently also prefer such habitats. Other mammal species that prefer these habitats certainly depend on them to lesser and varying degrees; thus, the consequences of reducing or eliminating early-successional forests, shrublands, or old-field habitats across the landscape will likely have varying demographic consequences, and thus importance, to those species.

Wildlife as valuable natural resources vs. intolerable pests: A suburban wildlife management model

Management of wildlife in suburban environments involves a complex set of interactions between both human and wildlife populations. Managers need additional tools, such as models, that can help them assess the status of wildlife populations, devise and apply management programs, and convey this information to other professionals and the public. We present a model that conceptualizes how some wildlife populations can fluctuate between extremely low (rare, threatened, or endangered status) and extremely high (overabundant) numbers over time. Changes in wildlife abundance can induce changes in human perceptions, which continually redefine species as a valuable resource to be protected versus a pest to be controlled. Management programs thatincorporate a number of approaches and promote more stable populations of wildlife avoid the problems of the resource versus pest transformation, are less costly to society, and encourage more positive and less negative interactions between humans and wildlife. We presenta case example of the beaver Castor canadensis in Massachusetts to illustrate how this model functions and can be applied.

Forest characteristics of Northern Goshawk nest stands and post-fledging areas in Oregon

The role of old-growth forest as a component of nesting habitat for northern goshawks (Accipiter gentilis) and the effect of timber harvest has come under increased scrutiny in the western United States. We examined the importance of selected elements of old-growth forest as nesting habitat for goshawks by comparing forest structure around 22 nests with 2 sets of random points. Comparisons were made at 6 spatial scales, from the nest stand up to a 170-ha post-fledging area (PFA). Goshawks nested more frequently in stands with dense canopy, late forest structure (i.e., trees >53 cm dbh, canopy closure >50%), and rarely in stands with mid-aged forest structure. Despite the occasional occurrence of goshawk nests in younger, more open-canopied stands, these conditions were less preferred than dense canopy, late forest structure. Late forest structure was more abundant within circles of 12 ha and 24 ha around nests than around random points. At the PFA scale, forest structure around nests was dominated by dense-canopied forest, always contained wet openings, and nests were positively associated with dry openings. Our findings support recent management recommendations for northern goshawks in the western United States, which call for maintaining the PFA in forest conditions intermediate between the high foliage volume and canopy cover of nest stands and more open foraging habitats. These conditions would provide nest sites for goshawks and habitat for a variety of prey species that inhabit late or early seral stage forest.

Equipment and Techniques for Nocturnal Wildlife Studies

Abstract Many biologists speculate on the nocturnal behavior of wildlife. Night-vision technologies may provide ways to move beyond speculation to observation of nocturnal activity. Nocturnal activity data collection is often secondary to broader study objectives; consequently, techniques for such studies are poorly understood and infrequently used. We reviewed 53 papers to examine image enhancement (i.e., night vision) and assess trends in nocturnal research techniques. We also conducted a field study on nocturnal behavior of roosting cranes (Grus spp.) to evaluate equipment function and efficacy for wildlife studies. A third-generation night-vision scope greatly outperformed a pair of first-generation night-vision binoculars, and we were able to identify cranes by species and observe and record their behaviors while they were on their nocturnal roost sites. Techniques reported in the literature included use of moonlight or natural ambient light, spotlight or simulated luminosity, remote photography, surveillance radar, infrared thermal imaging, and image enhancement. With the many techniques available, scientists can select the procedure or a combination of strategies explicit to their purpose. We believe night-viewing technologies are an exceptional, nonintrusive, functional tool for wildlife ecology studies. However, even the best equipment will have problems or issues with contrast, inclement weather, and large group size and density. Regardless of the specific method used and the inherent challenges, we believe third-generation, American-manufactured night-vision equipment can provide valuable insight into the complete life history of animals and can promote a more comprehensive approach to wildlife studies.

Effects of sampling blood on survival of small mammals

We assessed mortality due to handling and survival of small mammals that had been anesthetized and then bled through the orbital sinus during a 1-year study in southeastern Arizona. Rates of return and mortality due to handling were not significantly different between treatment and control for any species. Estimates of survival based on Cormack-Jolly-Seber capture-recapture models indicated no significant difference ( P < 0.05) in survival for white-throated woodrats ( Neotoma albigula ) and combined species of mice in the genus Peromyscus . However, for pocket mice ( Chaetodipus ) mean rates of survival were significantly lower for animals that had been bled. Removing samples of blood from wild rodents appears to have little effect on survival for most species. Lower survival in pocket mice may be due to the effects of anesthesia or the combined effects of bleeding and anesthesia on this desert-adapted animal.

Suburban wildlife: Lessons, challenges, and opportunities

The United States, as well as most developed and many developing nations worldwide, is becoming increasingly urban and suburban.Although urban, suburban, and commercial development account for less than one percent to just over 20% of land use among states, 50–90% of the residents of those states can be classified as urban or suburban dwellers. The population of the U.S. as a whole has risen from being > 95% rural in the 1790s to about 80% urban-suburban today. With these changes in land use and demographic patterns come changes in values and attitudes; many urbanites and suburbanites view wildlife and nature differently than rural residents. These are among the challenges faced by wildlife biologists and natural resource managers in a rapidly urbanizing world. In 2003, we convened a symposium to discuss issues related to suburban wildlife. The papers presented in this special issue of Urban Ecosystems address the lessons learned from the early and recently rapidly expanding literature, the challenges we face today, and the opportunities that can help deal with what is one of the biggest challenges to conservation in a modernizing world.