The study of urban birds has increased exponentially in the last century. A prior review of the scientific literature up to the year 2000 found 100 research articles on urban birds, but in the past decade alone over 1000 have been published. Here I review the studies from 2006-2015 to characterize their approach, location, general findings and recent obsessions, with an eye toward suggesting important future directions. Urban ornithology remains centered in the northern hemisphere, although there is a rapid increase in studies from southern, tropical and biodiverse settings. Studies in the north have changed from documentation of the composition of urban avifaunas to include many studies of the demographic response to aspects of urban environments. Studies of pattern remain most common in Latin America, Asia, Africa, New Zealand and the Middle East. Across the world, ornithologists are revealing the rapid evolution of behavioural and morphological adaptations by birds to the urban environment, much of which is due to phenotypic plasticity. The relationship of humans to nature generally and birds specifically has been increasingly studied as a driver of avifaunal change as well as a factor affecting human ethics. Urban ornithology remains rarely experimental, but it has matured to the point of supporting synthetic reviews and meta-analyses that quantify the loss of avian diversity from city centres, characterize successful urban birds, discuss the role of amount and arrangement of vegetation on bird life, and explore the complex relationships between the subsidies and hazards of urban life and the survival and reproduction of birds. Yet much remains to be learned, including how some species thrive in cities with abundant predators; how city form and location affect the peak in avian richness that occurs typically at intermediate levels of urbanisation; the significance of functional biotic homogenization; and the ways in which engaging citizens in urban bird life informs their broader environmental land ethic.

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https://onlinelibrary.wiley.com/doi/pdf/10.1111/ibi.12430

A decadal review of urban ornithology and a prospectus for the future

The rapid urbanization of the world has profound effects on global biodiversity, and urbanization has been counted among the processes contributing to the homogenization of the world’s biota. However, there are few generalities of the patterns and drivers of urban birds and even fewer global comparative studies. Comparable methodologies and datasets are needed to understand, preserve, and monitor biodiversity in cities. We explore the current state of the science in terms of basic patterns of urban birds in the world’s cities and lay out a research agenda to improve basic understanding of patterns and processes and to better inform conservation efforts. Urban avifaunas are often portrayed as being species poor and dominated by omnivorous and granivorous species that tend to be nonnative. Common families in cities include Accipitridae, Anatidae, and Scolopacidae, all of which have more species than expected in cities compared to the global distribution of species in these families. Recent research shows that cities support an avifauna dominated by native species and that cities are not homogenized at the global level. However, cities have lost substantial biodiversity compared to predicted peri-urban diversity, and 31 of the world’s most invasive bird species are found in cities. Future research is needed to better characterize the anthropogenic, environmental, and ecological drivers of birds in cities. Such mechanistic understanding is the underpinning of effective conservation strategies in a human dominated world.

Global patterns and drivers of urban bird diversity

The role of ‘nativeness’ in urban greening to support animal biodiversity

Escape behaviour of birds in urban parks and cemeteries across Europe: Evidence of behavioural adaptation to human activity.

Research in urban ecology is growing rapidly in response to the exponential growth of the urban environment. However, few studies have focused on tropical megacities, and on the interplay between predators’ habitat selection and human socio-economic aspects, which may mediate their resilience and coexistence with humans. We examined mechanisms of breeding habitat selection by a synanthropic raptor, the Black Kite Milvus migrans, in Delhi (India) where kites mainly subsist on: (1) human refuse and its associated prey-fauna, and (2) ritualised feeding of kites, particularly practised by Muslims. We used mixed effects models to test the effect of urban habitat configuration and human practices on habitat selection, site occupancy and breeding success. Kite habitat decisions, territory occupancy and breeding success were tightly enmeshed with human activities: kites preferred areas with high human density, poor waste management and a road configuration that facilitated better access to resources provided by humans, in particular to Muslim colonies that provided ritual subsidies. Furthermore, kites bred at ‘clean’ sites with less human refuse only when close to Muslim colonies, suggesting that the proximity to ritual-feeding sites modulated the suitability of other habitats. Rather than a nuisance to avoid, as previously portrayed, humans were a keenly-targeted foraging resource, which tied a predator’s distribution to human activities, politics, history, socio-economics and urban planning at multiple spatio-temporal scales. Many synurbic species may exploit humans in more subtle and direct ways than was previously assumed, but uncovering them will require greater integration of human socio-cultural estimates in urban ecological research.

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Habitat selection by an avian top predator in the tropical megacity of Delhi: human activities and socio-religious practices as prey-facilitating tools

Various species of raptors, or birds of prey, have been found living and hunting in all parts of the urban environment, including complexes of business and light industrial facilities, commonly known as business parks. Conservation in business parks is a growing concern due to the amount of land they occupy and their pattern of development of formerly vacant land on the fringes of urban areas. We conducted call-broadcast surveys for raptors at a set of 155 survey points within the business park landscape of the St. Louis area to answer the question of what landscape characteristics of business parks are predictors of presence of raptors. The detection data from these surveys was used to model the occupancy probability of the target species of raptor at each survey site and to determine the effect of landscape variables at each site on occupancy probabilities. We detected nine species of raptors at business parks. The red-tailed hawk (Buteo jamaicensis), the American kestrel (Falco sparverius), and the Cooper’s hawk (Accipiter cooperii) were the most commonly detected species. The probability of raptor occupation was negatively associated with lawn cover. Occupancy probabilities of red-tailed hawks and Cooper’s hawks were positively associated with woodland cover, and American kestrel occupancy probability was positively associated with grassland cover. Based on this study, we would recommend that businesses concerned with the conservation of raptors in and around their properties plan to develop less lawn area, preserve or plant more native grassland, and preserve woodlots.

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Jonathan R. Hogg

Papers

Habitat associations of birds of prey in urban business parks