Urbanisation lowers great titParus majorbreeding success at multiple spatial scales

Abstract

While numerous studies have reported negative effects of urbanisation on birds, few have examined the role of urban scale in influencing breeding success. Furthermore, many studies have relied on qualitative rather than quantitative assessments of urbanisation. This study sought to address these issues by testing the effects of urbanisation, measured at two spatial scales, on the breeding success of great tits Parus major. A nested study design, incorporating over 400 nestboxes, was used in study sites across northern Belgium with a priori quantified degrees of urbanisation at both local and regional scales. All measured breeding parameters were found to vary at one or both spatial scales of urbanisation; in more urbanised areas great tits displayed advanced laying dates but lower breeding success compared to rural areas, with smaller clutch sizes, lower nestling masses and fewer fledglings per egg. Importantly, urbanisation effects were not limited to big cities as birds breeding in gardens or parks in small towns also had comparatively low success. We found that both regional‐ and local‐scale urbanisation had consistent significant effects on laying date, clutch size and nestling mass, while the number of fledglings per egg was negatively influenced by local‐scale urbanisation only. Results of this study therefore highlight the importance of utilising multiple spatial scales in analysing urbanisation effects, as well as the potential negative impact of local urbanisation on breeding success. This calls for further investigation into mechanisms driving urbanisation effects and how these may vary at different scales.

Food availability limits avian reproduction in the city: An experimental study on great tits Parus major

“…As predicted by the food limitation hypothesis, control broods that did not receive supplementary food were smaller and had lower survival rates in the urban site than the forest site—matching previous studies of reproductive success in unmanipulated great tit populations (Bailly et al, 2016; de Satgé et al, 2019) including our focal study populations (Seress et al, 2018). Crucially, urban supplemented broods had considerably higher fledging success and produced larger nestlings than urban control pairs, whereas supplementary feeding of forest broods had only small and statistically non‐significant effects on these traits.…”

An avian urban morphotype: how the city environment shapes great tit morphology at different life stages

“…One limitation of previous investigations on morphotypes in urban habitats is that they have mainly compared habitats in a binary way, such as forests versus urban parks (e.g. Björklund et al 2010;Hedblom and Söderström 2012;Markowski et al 2013; but see Marini et al 2017;de Satgé et al 2019). The urban landscape is however very heterogeneous and outside the heavily studied parks it also offers a wide range of more or less urbanized habitats (Amrhein 2013).…”

Breeding in the Pandemic: Short-Term Lockdown Restrictions Do Not Alter Reproductive Decisions and Avian Life-History Traits in a European Capital City

“…Earlier studies reported pronounced differences in terms of life-history traits and reproductive success between urban and rural populations 12 , often identifying chemical 13,14 , light 15,16 and sound pollution 17,18 as main drivers of these differences. Other studies emphasized the negative and pervasive effect of built up areas, infrastructural networks and, more generally, impervious surfaces on avian tness [19][20][21] . Yet, only a handful of studies tested whether human presence per se was linked to evolutionary traits in urbanised contexts 21,22 .…”