A primary aim of urban ecology is to enhance our understanding of the structure and function of urban systems (McDonnell and Pickett 1990). Urban systems offer a unique ecological situation in which biophysical and socioeconomic factors interact hierarchically across spatial and temporal scales. These complex interactions produce dynamic feedbacks resulting in “emergent properties,” such as exacerbated disturbances (e.g., frequent flooding, pollution, climate change, etc.; Pickett et al. 2001), species turnover, and societal impacts (e.g., health problems, gentrification, etc.; Redman and Jones 2005). Insights into these systems allow ecologists to inform policymakers, land use planners, and homeowners regarding land use practices...

Urban development modifies natural habitats by replacing their fundamental components with new ones (Vitousek et al. 1997). Specifically, natural habitat structure is replaced by urban elements such as buildings and streets, a process that results in a reduction of plant cover and the loss of native species (Main et al. 1999, Czech et al. 2000, Melles 2005). Hence, urbanization replaces the native plant community structure with human constructions, resulting in fewer species that are often found in high abundances (Emlen 1974, Chace and Walsh 2006). This reduction in local biodiversity allows for the arrival and establishment of exotic species that...

The ways in which bird communities change in response to urbanization have been well documented (Marzluff et al. 2001, Shochat 2004, MacGregor-Fors et al., chapter 3, this volume). Four general patterns have emerged: (1) a reduction in species richness, (2) a decrease in evenness (urban bird communities have fewer but more abundant species), (3) an increase in abundance of large species, and (4) an increase in abundance of introduced species. While these patterns have been documented in various urban areas, few studies have investigated the underlying mechanisms causing such patterns. Results to date emphasize two competing, but not mutually exclusive...

Research in urban systems has consistently demonstrated that the distribution and abundance of birds can be strongly affected by urban development at multiple spatial scales (Beissinger and Osborne 1982, Mills et al. 1989, Blair 1996, Germaine et al. 1998, Marzluff et al. 2001, Pickett et al. 2001). Still, there remain several conspicuously large gaps in our understanding of avian ecology in urban areas, particularly with respect to empirical evidence of the ecological mechanisms responsible for relationships between urbanization and avian communities (Faeth et al. 2005, Shochat et al. 2006). Urban development can profoundly affect bird communities in remnant forest systems...

Urbanization is a large-scale process that fragments the landscape and significantly alters the distribution and abundance of many native species and assemblages of bird communities (Vale and Vale 1976, Beissinger and Osborne 1982, Bezzel 1985, Blair 1996, Fernández-Juricic and Jokimäki 2001, Marzluff 2001, McKinney 2002, Chace and Walsh 2004). In general, urbanization decreases bird species diversity and richness, but increases the total density of birds (Batten 1972, Bezzel 1985, Jokimäki and Suhonen 1993, Marzluff 2001, McKinney 2002). Urbanization favors omnivores (Beissinger and Osborne 1982, Bezzel 1985, Diamond 1986, Clergeau et al. 1998, Jokimäki and Suhonen 1998), and partly for this...

Though citizen science has been increasingly formalized over recent decades, the concepts on which the discipline is based are as old as science itself. Much of the earliest astronomical research, for instance, was conducted by clergy in the Catholic Church. While contemporary explanations of citizen science vary slightly, they converge on a definition ofthe involvement of citizens from the nonscientific community in academic research(Trumbull et al. 2000, Lee et al. 2006). By this definition, some of the most renowned scientists and ornithologists could be considered citizen scientists (e.g., Darwin, Mendel, Mayfield, Skutch, etc.); however, there has been a...

The citizen science approach, where volunteer observers aid scientists in data collection, has become a useful means of investigating large-scale questions related to a variety of aspects of avian ecology. Programs such as the National Audubon Society’s Christmas Bird Count (CBC) and the North American Breeding Bird Survey (BBS) administered by the U.S. Geological Survey and Canadian Wildlife Service, have engaged citizen science volunteers in avian research for years. More recently, programs initiated by the Smithsonian Institution/National Zoo (i.e., the Neighborhood Nestwatch Program) and by the Cornell Laboratory of Ornithology (i.e., Great Backyard Bird Count and Project Feeder-Watch) have been...

Urbanization stands as one of the world’s dramatic trends in the 20th century, with the proportion of the global population living in urban areas increasing from 13% in 1900 to 49% in 2005 (United Nations 2006). By 2030 it is predicted that 4.9 billion people will reside in urban areas. This human population increase has resulted in both an expansion of the spatial extent of urbanized areas and a corresponding decline in agricultural lands and natural ecosystems surrounding cities (Houghton 1994). Thus, urban sprawl has been cited as a prime threat to biodiversity, with urbanization leading to high local extinction...

Increasing urbanization is characterized by displacement of native vegetation with non-native vegetation and man-made structures, higher prevalence of exotic species, and increased disturbance and hazards to wildlife because of higher densities of people, roads, and domestic predators such as cats and dogs (DeStefano and DeGraaf 2003). Construction of houses, commercial buildings, parking lots, and roads alters and fragments habitat, and patches of native vegetation become isolated islands within city limits (Shaw et al. 1991, Germaine et al. 1998). As urbanization increases, these islands become farther away from native vegetation surrounding the city. This separation can mean loss of genetic diversity...

The area covered by urban habitats has increased rapidly over the past century, and over half of the United States population now resides in cities (Marzluff et al. 2001a). Despite the expansion of urban landscapes, we remain largely ignorant of the degree to which birds and other organisms can maintain viable populations in these heavily disturbed environments. Urban habitats may present unique ecological challenges for native biota, and understanding specifically how urban fragmentation affects the ability of birds to reproduce successfully is a question of much concern (Marzluff et al. 2001a).

Urban breeding birds ultimately face the same challenges as...

Dispersal is a critical population process that maintains gene flow within and between populations, allows metapopulation persistence, and supplements population growth (Levins 1970, Merriam 1991, Hanski and Gilpin 1997). Dispersal is also a key parameter in source–sink population models as it contributes to the net gain or loss of individuals through immigration and emigration, respectively, and maintains the existence of sink populations (Pulliam 1988, Pulliam and Danielson 1991). If a species in a given local population is extirpated, the habitat patch may become recolonized by members of the species able to immigrate to the patch (Brown and Kodric-Brown 1977)....

Ecological research on birds in urban environments dates at least to Pitelka’s (1942) comparison of the avifauna in a Southern California resort town with the bird community in the surrounding hills. There was subsequently little interest in this area of research until the 1970s, when a sharp rise in published studies of urban impacts on birds was followed by another strong surge in the following decade (Marzluff et al. 2001a). In the 1980s, coincident with the ascendance of conservation biology (Soulé and Wilcox 1980, Soulé 1985), some authors departed from the template established by Pitelka of simply describing avian response...

Conserving avian habitat in urban environments is directly related to the myriad decisions made by people. The decisions made by homeowners, policymakers, and design-build professionals (a term that encompasses firms and professionals that engage in both planning and construction, e.g., developers and landscape architects) interact in dynamic ways to either enhance or inhibit biodiversity (Grimm et al. 2000, Pickett et al. 2001, Hostetler and Knowles-Yanez 2003). For example, developers would have to preserve habitat of good quality and residents that live around these areas would have to appropriately manage their own properties so as not to have a negative impact...

As human populations grow, the urbanized area of earth also increases (Meyer and Turner 1992, Houghton 1994). Depending on economics, social preferences, and land use policies, the growth of urban populations causes cities, and even more profoundly their suburbs, to spread across large expanses of former agricultural and natural lands (Ewing 1994). The worldwide extent of sprawling settlement is visible in the nighttime images of earth from space (Elvidge et al. 1997). These images reveal that substantial portions of the north temperate zone are heavily settled, most ice-free coastlines are settled, our most fertile lands are quickly being developed, and...

The provision of feeding and nesting resources for birds is a popular activity across much of the world, particularly in industrialized nations. Between one-fifth and one-third of households in Europe, North America, and Australia provide supplementary food for wild birds (Clergeau et al. 1997, Rollinson et al. 2003, Lepczyk et al. 2004), and in the United States alone, 52 million people frequently feed garden birds (U.S. Fish and Wildlife Service 2001). Surprisingly few studies have considered the role of gardens in supporting biodiversity (but see Savard et al. 2000; Beebee 2001; Thompson et al. 2003; Gaston et al. 2005a, 2005b;...

Research on human-environment interactions often focuses on human activities with negative consequences for wildlife, such as habitat destruction (Forester and Machlis 1996, Vitousek et al. 1997, Marzluff 2001). But humans also engage in activities that either create new environments or subsidize existing ones in ways that may ameliorate some of the impacts of habitat loss. Examples range from gardening to attract birds and butterflies to building bird or bat houses for nesting and roosting, installing ponds or bird baths, and perhaps most commonly, hanging bird feeders and filling them with food. People engage in these activities with the explicit intention...

Our understanding of the ecology of birds in an urbanizing world is blossoming. Correlational connections between land cover change and bird community diversity or population density are serving as strong platforms from which to study the mechanisms causing bird responses to urbanization (Shochat et al. 2006). We are learning the subtle details of how birds respond to urban sources of food (Shochat et al. 2004) and that decoupling from variation in natural prey may allow some species to attain spectacular population growth rates (Withey and Marzluff 2005), while others face extirpation (Schoech and Bowman 2003). We know more about the...