Plumage colouration differs between offspring raised in natural cavities and nestboxes

Abstract

Most of our knowledge on hole-nesting birds, including plumage colouration (an important component of visual signalling), comes from studies on populations breeding in human-provided nestboxes. However, as demonstrated in comparative studies, multiple parameters, such as cavity dimensions and microclimatic conditions, differ between natural and artificial cavities. Despite this, no study so far examined the impact of cavity type on plumage colouration to verify whether extrapolation of results from birds growing in nestboxes is justified. Here, we examined the impact of cavity type - natural cavities vs. nestboxes - on the carotenoid-based colouration of blue tit (Cyanistes caeruleus) and great tit (Parus major) nestlings. We found clear differences in plumage colouration depending on the type of cavity in which the birds developed. Our study adds to the growing body of evidence confirming that varying properties of natural cavities and nestboxes might influence nestling physiology, leading to phenotypic differences in the long-term.

Extra‐pair paternity, breeding density, and synchrony in natural cavities versus nestboxes in two passerine birds

“…For instance, females in poor condition are predicted to produce more often female than male offspring (Cockburn et al, 2002 ; Dietrich‐Bischoff et al, 2006 ). However, we assessed food availability in the same study years as frass fall collection and feather coloration of breeding adults as an indicator of parental condition, and we found no difference between the two cavity types (Janas et al, 2022 preprint; Sudyka, Di Lecce, Wojas, et al, 2022 ). Alternatively, since blue tits produced fewer fledgings in nestboxes than in natural cavities in the same forest (Sudyka, Di Lecce, Wojas, et al, 2022 ), this result might stem from early selective mortality of male offspring in nestboxes, as males require a bigger investment than females.…”

Microclimate shifts in nest‐boxes and natural cavities throughout reproduction

“…It has to be noted that the apparent temperature perceived by nesting birds was higher than the one measured within the cavity space (as loggers never came to contact with bird bodies) because of the additional heat produced and transferred by thermoregulating siblings (Webb and King 1983). Such a raise in both temperature and humidity, while still below critical thresholds (McKechnie and Wolf 2010), can possibly increase costs of thermoregulation and thus entail biological consequences for nestling development and fitness (Janas et al 2022). Additional energetic resources might be necessary to facilitate the increased evaporative cooling in nest‐box‐reared young that could otherwise be devoted to growth (Boyles et al 2011, Nord and Nilsson 2019, van de Ven et al 2020), and survival (Cunningham et al 2013, Bourne et al 2020).…”