Avian productivity in urban landscapes: a review and meta‐analysis

Abstract

There is an urgent need to thoroughly review and comprehend the effects of urbanization on wildlife in order to understand both the ecological implications of increasing urbanization and how to mitigate its threat to biodiversity globally. We examined patterns in comparative productivity of urban and non-urban passerine birds, using published estimates from paired comparisons, and by reviewing and developing explanations in terms of resources, competitors, predators and other specifically urban environmental factors. The most consistent patterns were for earlier lay dates, lower clutch size, lower nestling weight and lower productivity per nesting attempt in urban landscapes; these were supported by a formal meta-analysis. Nest failure rates did not show consistent patterns across the species considered. We suggest that food availability is a key driver of differences in passerine demography between landscapes. In urban habitats, human-provided food may improve adult condition over winter, leading to earlier lay dates and, in some species, to higher survival and higher breeding densities, but paucity of natural food may lead to lower productivity per nesting attempt. We demonstrate that additional comparative research is needed on a wider range of species, on the effects of natural and human-provided food availability, and on the differences in survival and dispersal between urban and non-urban populations. Importantly, better-targeted research and monitoring is needed in areas that are at greatest threat from urbanization, especially in the developing world.

Spatial variation in haemoglobin concentration of nestling Blue Tits (Cyanistes caeruleus): a long-term perspective

“…Additionally, long-term year-to-year changes in haemoglobin concentration were correlated with frassfall peaks in the forest site. Bańbura et al (2007) found a strong association between haemoglobin concentration in Blue Tit nestlings and the amount of caterpillars during the time of extremely high abundance of caterpillars in seasons 2003-2005. Chamberlain et al (2009 showed in their meta-analysis that urban bird populations are characterized by lower productivity (lower clutch sizes, lower fledging success) and worse body condition (lower nestling weights) than nonurban populations.…”

“…The rapid growth of urban areas resulting in sudden changes in landscape spatial patterns has become one of the most important environmental issues in recent decades (Chamberlain et al 2009). Therefore, an understanding of the influences of variation in habitat quality on organism condition and breeding success in association with physiological knowledge may provide instruments to support evidencebased management decisions (Cooke and O'Connor 2010;Bonier 2012;Ellis et al 2012;Cook et al 2013).…”

“…This process involves clearing much of the original vegetation to make way for urban infrastructure, habitat fragmentation, expansion of nonnative plant species, increasing amounts of easily accessible, but low quality urban food leftovers, light, noise, and chemical pollution (Shanahan et al 2014). All those factors affect the condition of animals and may have significant impact on their breeding traits (Chamberlain et al 2009). It was shown that a patchy environment makes foraging much more difficult for birds (Riddington and Gosler 1995;Hinsley et al 2006).…”

“…Therefore, further long-term comparative studies between urban and non-urban populations of birds are needed (Chamberlain et al 2009;Minias 2015).…”

Use of anthropogenic material affects bird nest arthropod community structure: influence of urbanisation, and consequences for ectoparasites and fledging success

“…The changes in habitat and resource availability associated with urbanisation have a marked effect on the life histories of urban birds (Chace and Walsh 2006). Urban-dwelling birds tend to lay eggs earlier, produce smaller clutches and lighter nestlings, and have lower average productivity per nesting attempt than their nonurban conspecifics (Chamberlain et al 2009). The lower availability of natural foods in urbanised areas results in lower food provisioning to nestlings, and while supplementary feeding can be ubiquitous in urban areas (Davies et al 2009;Orros and Fellowes 2015a;Hanmer et al, in review), the benefits for bird productivity are not clear (Robb et al 2008;Harrison et al 2010;Plummer et al 2013).…”