Development of nestling blue tits (Cyanistes caeruleus) is affected by experimental addition of aromatic plants

Abstract

Some passerines incorporate aromatic plants in their nest cups, and several hypotheses have been formulated to explain this behaviour. One of those, the Drug Hypothesis, states that aromatic plants present in nests have positive effects on nestlings’ development through increased immune function. In this study, we aimed to examine if experimental addition of aromatic plants had positive effects on reproductive performance (the number of fledglings produced and nestling survival rate) and nestling development (weight and tarsus length). In addition, we study whether those potential effects were more noticeable in different brood sizes–small and large–through an observational approach. We expect that large broods, due to increased resource competition between nestlings, will benefit more from aromatic plant incorporation, as compared to small broods. Nestlings were significantly heavier in 2015 as compared to 2016 and 2017 and in small broods. No effect of treatment was observed in nestling weight. Although there was no overall effect of treatment on nestling tarsus length, nestlings from aromatic nests had significantly longer tarsi as compared to nestlings from control nests, in large broods.

Differences in use of bryophyte species in tit nests between two contrasting habitats: an urban park and a forest

“…There is an increasing number of experimental evidence that morphological and physiological condition of tit nestlings gains when this aromatic plant material is present in the nest (Mennerat et al 2009a(Mennerat et al , 2009bGlądalski et al 2020a;Pires et al 2020). It was also shown that Blue Tits are very choosy when collecting those aromatic plants (Petit et al 2002).…”

“…Some authors also distinguish an outer, decorative/functional layer in tit nests (e.g. large bird feathers brought by a male; delicate, movable lining-like cover for eggs or fresh, aromatic plants; Sanz & García-Navas 2011;Reynolds et al 2019;Pires et al 2020;Glądalski et al 2020a). Different studies show that nest composition in Great Tits Parus major and Blue Tits Cyanistes caeruleus is affected by a set of factors, including amounts of rainfall, spring temperatures, latitude, parents and territory quality, availability of construction materials or risk of predation (Mainwaring et al 2012(Mainwaring et al , 2014Heenan 2013;Kaliński et al 2014;Reynolds et al 2016;Biddle et al 2018;Deeming et al 2019;Alambiaga et al 2020).…”

Nest Design and Breeding Success: Replicability of Methodologies and Research Findings in Avian Model Species

“…The conclusions from the older studies [reviewed in 114,171] did not differ much from the conclusions of the more recent studies [119,172]. For instance, in blue tits from the Mediterranean region, it has been repeatedly shown that higher greenery loads or experimental treatments with fresh greenery were not translated into more hatchlings or more fledglings [119,130,137,138,172]. Some blue tit studies reported that an experimental change in the amounts of aromatic plant fragments significantly changed the morphometry, growth patterns, or blood profiles of nestlings compared to control treatments (e.g., [131,141]), whereas other field experiments found little or no effects on nestlings (e.g., [119,137,172]).…”

“…Studies of associations between fresh greenery loads and different measures of breeding performance have been replicated most in nest-box breeding blue tits and starlings. The conclusions from the older studies [reviewed in 114,171] did not differ much from the conclusions of the more recent studies [119,172]. For instance, in blue tits from the Mediterranean region, it has been repeatedly shown that higher greenery loads or experimental treatments with fresh greenery were not translated into more hatchlings or more fledglings [119,130,137,138,172].…”

“…For instance, in blue tits from the Mediterranean region, it has been repeatedly shown that higher greenery loads or experimental treatments with fresh greenery were not translated into more hatchlings or more fledglings [119,130,137,138,172]. Some blue tit studies reported that an experimental change in the amounts of aromatic plant fragments significantly changed the morphometry, growth patterns, or blood profiles of nestlings compared to control treatments (e.g., [131,141]), whereas other field experiments found little or no effects on nestlings (e.g., [119,137,172]). For instance, Gladalski et al [141] reported an effect of greenery on nestling hemoglobin levels in Polish blue tit broods treated with a cocktail of lavender Lavandula angustifolia (ca.…”