Environmental Influences on the Evolution of Growth and Developmental Rates in Passerines

Young birds often face poor food supply, which reduces their growth and development. However, if the shortage of resources is only temporary, there is a possibility to adjust the growth trajectory of morphological traits after the end of the short‐term limitation period. The two main ways of compensatory growth are delayed development (parallel growth) and growth acceleration (catch‐up growth). Parallel growth has been widely demonstrated in birds, but the presence of catch‐up growth in altricial species has been questioned. However, most experiments have been conducted in laboratory conditions. We manipulated the food supply of nestling collared flycatchers Ficedula albicollis in the wild by removing the male parent for three days at 4–7 days of chick age. We performed early partial swapping to control for origin effects on growth, and total swapping after the period of food limitation to ensure similar late growth environment for deprived and control chicks. Both body mass and tarsus length of deprived chicks was negatively affected by the food scarcity. Body mass showed efficient catch‐up growth, but this compensation was absent in skeletal size. Body mass is an important determinant of postfledging survival in this long‐distance migrant. Further studies are needed in a variety of species to examine developmental plasticity in relation to age at food scarcity and the allocation hierarchy of various morphological traits.

Section: Discussionmentioning

confidence: 87%

Developmental plasticity in a passerine bird: an experiment with collared flycatchersFicedula albicollis

Hegyi¹,

Török²

2007

“…Among Parulid warblers, juveniles invest less in juvenile plumage if they fledge rapidly. Additionally, in the eleven‐species sample we used to test our assumptions about age differences in feather structure, cavity nesters, which tend to experience high nestling survival and therefore have long nestling periods (Ricklefs 1968, Remes and Martin 2002), had higher juvenile barb count than other species (expressed as % of adult barb count; cavity nesters, mean±SD=84±7, n=4; other species, 70±10, n=7; U =3.0, P=0.038). Therefore, our hypothesis that juvenile warblers trade investment in body feathers for rapid fledging may apply generally.…”

Section: Discussionmentioning

confidence: 99%

“…Duration of the nestling period was our index of selection for rapid fledging. Short nestling periods are thought to be a response to survival selection to develop and fledge rapidly to reduce nestling mortality (Ricklefs 1968, Bosque and Bosque 1995, Remes and Martin 2002). If juveniles sacrifice investment in juvenile feathers to promote rapid fledging, then barb count should be low in species with short nestling periods.…”

Section: Methodsmentioning

confidence: 99%

Quantifying structural variation in contour feathers to address functional variation and life history trade‐offs

Butler¹,

Rohwer²,

Speidel³

2008

Body feathers are important to many interactions birds have with their physical and social environments, such as streamlining the body for flight, thermoregulation, and social signaling. Birds differ dramatically in the texture of their body plumage depending on species and age class, likely reflecting different functional demands and age‐related trade‐offs in feather production. Despite the important insights potentially offered by studying variation in the structure of body feathers, there is no clear system for quantifying this variation. We present methods for quantifying age and species differences in the structure of body feathers. Most variation in our measures is due to species and age‐class differences, with little variance attributable to individual birds or to differences among feathers sampled from the same bird. We use our measures to test the hypothesis that the loosely‐textured plumage characteristic of many juvenile passerines reflects a trade‐off between investment in feather quality and rapid body growth that promotes early fledging. The structure of juvenile feathers was negatively correlated with duration of the nestling period among ten species of New World warblers (Parulidae), suggesting a trade‐off between investment in feathers and investment in rapid somatic development promoting fledging. Systematic studies of variation in the structure of body feathers will likely offer numerous other insights into avian biology.

“…A too low fitted A ‐value is typically caused by truncation with respect to the largest young or chick sizes, whereas prefledgings with higher than adult sizes (typically mass) may return fitted A ‐values that are too high, resulting in a curve that overshoots (Ricklefs , Tjørve et al , Austin et al ). A number of species have pre‐fledglings that are heavier than the adult birds, for example many seabirds and even passerines (Ricklefs , Remeš and Martin ).…”

Section: Methodsmentioning

confidence: 99%

Modelling avian growth with the Unified‐Richards: as exemplified by wader‐chick growth

Tjørve

2017

Postnatal growth in birds is traditionally modelled by fitting three‐parameter models, namely the logistic, the Gompertz, or the von Bertalanffy models. The purpose of this paper is to address the utility of the Unified‐Richards (U‐Richards) model. We draw attention to two forms of the U‐Richards and lay down a set of recommendations for the analysis of bird growth, in order to make this model and the methods more accessible. We examine the behaviour of the four parameters in each model form and the four derived measurements, and we show that all are easy to interpret, and that each parameter controls a single curve characteristic. The two parameters that control the inflection point, enable us to compare its placement in two dimensions, 1) inflection value (mass or length at inflection) and 2) inflection time (time since hatching), between data sets (e.g. between biometrics or between species). We also show how the parameter controlling growth rate directly presents us with the relative growth rate at inflection, and we demonstrate how one can compare growth rates across data sets. The three traditional models, where the inflection value is fixed (to a specific percentage of the upper asymptote), provide incompatible growth‐rate coefficients. One of the two forms of the U‐Richards model makes it possible to fix not only the upper asymptote (adult value), but also the intersection with the y‐axis (hatching value). Fitting the new model forms to data validates the usefulness of interpreting the inflection placement in addition to the growth rate. It also illustrated the advantages and limitations of constraining the upper asymptote (adult value) and the y‐axis intersection (hatching value) to fixed values. We show that the U‐Richards model can successfully replace some of the commonly used growth models, and we advocate replacing these with the U‐Richards when modelling bird growth.