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

Abstract

Nests are a critically important factor in determining the breeding success of many species of birds. Nevertheless, we have surprisingly little understanding of how the local environment helps determine the materials used in nest construction, how this differs among related species using similar nest sites, or if materials used directly or indirectly influence the numbers of offspring successfully reared. We also have little understanding of any potential links between nest construction and the assemblage of invertebrates which inhabit nests, in particular, ectoparasites. We addressed these questions by monitoring the success rates of Blue Tits Cyanistes caeruleus and Great Tits Parus major, using nest boxes in rural, urban greenspace and urban garden settings. We collected used nests, identified the arthropods present, and measured the proportions of highly processed anthropogenic materials used in nest construction. Twenty-five percent of Great Tit nest materials were of anthropogenic origin and this was consistent across habitats, while Blue Tits used little (1-2%) anthropogenic material except in gardens (*16%), suggesting that Great Tits preferentially sought out these materials. In fledged nests, an increasing use of anthropogenic material was associated with a lower general arthropod diversity and ectoparasite predator abundance (Blue Tits only), but higher levels of Siphonaptera (fleas).Higher arthropod diversity was associated with lower flea numbers, suggesting that increased diversity played a role in limiting flea numbers. No direct link was found between breeding success and either anthropogenic material usage or arthropod diversity and abundance. However, breeding success declined with increasing urbanisation in both species and increased with nest weight in Blue Tits. The interplay between urbanisation and bird ecology is complex; our work shows that subtle anthropogenic influences may have indirect and unexpected consequences for urban birds.

Microclimate, CO2and CH4concentration on Blue tits (Cyanistes caeruleus) nests: effects of brood size, nestling age and on ectoparasites

“…The positive associations in this case could be related with the use of the same food source, nestlings, but the negative relationship with blackflies is difficult to explain. However, some studies have shown that arthropod abundance inside nests can affect negatively flea abundance (Heeb et al 2000, Hanmer et al 2017. We also find a negative relationship between final abundance of blowflies and the final abundance of mites in nests.…”

Urbanisation and nest building in birds: a review of threats and opportunities

“…On the one hand, several authors found no variation in nest mass or size along an urbanisation gradient for Blue or Great Tits in different European cities (Glądalski et al 2016;Reynolds et al 2016;Lambrechts et al 2017). On the other hand, Hanmer et al (2017) found that Blue Tits, but not Great Tits, in the same English town had lighter nests in more urbanised areas. This could be explained in a thermal context, as several studies have found geographical variation in nest size/mass that has been attributed to variations in ambient temperature (Deeming et al 2012;Mainwaring et al 2012Mainwaring et al , 2014aBiddle et al 2016).…”

“…The use of cigarette butts is not just restricted to House Finches in Mexico (Suárez-Rodríguez and Macías Garcia 2017), and has been found in other species such as House Sparrows in North America (Suárez-Rodríguez et al 2013 and Asia (Radhamany et al 2016), suggesting that it might be a general behavioural innovation for urban-adapted species. In contrast, Blue Tits (Cyanistes caeruleus), a species that does not use cigarette butts as nest constituents, in the town of Reading, UK using more anthropogenic nesting material had larger numbers of fleas (Siphonaptera) within their nest contents (Hanmer et al 2017). The authors argue that this is caused by a reduction in the diversity of nest-dwelling arthropods (including potential competitors and predators of flea larvae).…”

“…In this context, nest composition has received increasing attention recently (Table 2). Several studies have highlighted a change in nesting materials along an urbanisation gradient (e.g., Wang et al 2009;Radhamany et al 2016;Reynolds et al 2016), while others did not find such effects (e.g., Townsend and Barker 2014;Hanmer et al 2017), suggesting that nest design may exhibit species-specific or even city-specific differences. It is also possible that the latter studies failed to find changes in nest composition because they considered too small a variation in human activities along their urbanisation gradient by including urban and intensively agricultural areas but not natural areas for comparisons.…”

“…Similarly, they could offer much needed information to understand the positive and negative effects of urban-associated changes in nest composition. While clearly anthropogenic materials such as cigarette butts assist ectoparasite control in nests, we still lack a deep understanding of how they reduce ectoparasite loads of nests, promote changes in the arthropod community of nests and improve nestling health (Suárez-Rodríguez et al 2013;Hanmer et al 2017).…”