A longitudinal analysis of the growth rate and mass of tail feathers in a great tit population: ontogeny, genetic effects and relationship between both traits

Abstract

Feathers have a diversity of functions in birds and are costly to produce, so their growth rate and mass can be reliable indicators of nutritional condition at the time of production. Despite the potential for feather metrics to advance our understanding of foraging, they are underused in avian ecology. One reason for this is the difficulty of interpreting whether individual variation is driven by ontogenetic, genetic or environmental effects, which is exacerbated by the fact that most analyses have been done on cross‐sectional data. We addressed this deficit using a longitudinal dataset of tail feathers collected from great tits Parus major to test for ontogenetic and genetic effects on growth rate, mass and length, while controlling for body/feather size differences and other confounding factors. First, we found that the type of moult episode and experimentally‐induced replacement differentially affected the length, mass and growth of feathers, providing evidence of an ontogenetic effect that should be considered when comparing these feather traits across individuals as a measure of condition. Second, we detected moderate to high repeatability and heritability values from parent–offspring regression for these three feather traits, which are suggestive of an underlying genetic component of variation. Third, we used a mean centring within‐individual approach to test whether feather growth rate and feather mass (length‐corrected) are indeed positively correlated with each other as overlapping indicators of body condition in birds, and found that this association, although positive, is weak and only significant between individuals. This suggests that both metrics are not so intimately linked as originally thought, and probably have different sensitivities to variation in foraging performance and ecological conditions. Together with the higher plasticity of feather growth rate compared to feather mass, our results support the idea that feather growth rate is better suited for examining short‐term responses to environmental variation.

The Impact of Avian Haemosporidian Infection on Feather Quality and Feather Growth Rate of Migratory Passerines

“…Our results align with this perspective, showing a positive correlation between feather quality and feather growth rate in house martins. Similar patterns have been observed in other species, such as great tits, where a positive relationship between feather growth rate and feather mass has been documented [ 106 ]. Nonetheless, this association was not as straightforward in sand martins.…”

Highland and lowland forest birds differ in their feather growth rates: a multispecies test in the southwestern Palaearctic

“…2021), it can be conjectured that this variation could be related to some idiosyncratic traits of these isolated, southern populations, which would make sense since a genetic component to bird feather mass has been demonstrated (De la Hera et al . 2013, 2022). It seems that the structural complexity or massiveness of feathers (mass per length) is directly related to follicle size (Jenni et al .…”

“…2012, but see De la Hera et al . 2022), one can postulate that lighter feathers would be produced in highland birds relative to lowland birds. Evidence for this hypothesis is mixed, as rapid moult is not always linked with lower feather mass (Jenni & Winkler 2020b).…”

Delayed post-juvenile moult in malaria-infected European blackcaps

“…However, the few studies attempting to address the influence of haemosporidian parasites on bird moult progress have not achieved clear conclusions [24,33] and often were based on mismatched parasite loads estimated outside the moulting period. Furthermore, infected birds seem to replace feathers more slowly [34,35], but these results have been based on experiments inducing feather replacement, which can produce confusing results because the cost of growing feathers outside the moulting season can be low or differ seasonally [36,37]. Therefore, it is especially important to study the influence of infection status on moult when the process is naturally occurring.…”