DOI: 10.5061/dryad.fm36k
title: Data from: Energetic constraint of non-monotonic mass change during offspring growth: a general hypothesis and application of a new tool

description: 1. Postnatal growth is an important life-history trait and can be a
 sensitive indicator of ecological stress. For over 50 years, monotonic
 (never-decreasing) growth has been viewed as the predominant trajectory of
 postnatal mass change in most animal species, notably among birds.
 However, prevailing analytical approaches and energetic constraints may
 limit detection of non-monotonic (or multi-phasic), determinate growth
 patterns, such as mass recession in birds (weight-loss prior to fledging,
 preceded by overshooting adult mass), which is currently believed to be
 restricted to few taxa. 2. Energetic surplus and shortfall are widespread
 conditions that can directly influence the degree of mass overshooting and
 recession. Thus, we hypothesize that in many species prevailing energetic
 constraints force mass change away from a fundamental non-monotonic
 trajectory to instead follow a monotonic curve. 3. We observed highly
 non-monotonic, mass change trajectories (overshooting adult mass by up to
 almost 20%) among common tern Sterna hirundo chicks, a well-studied
 species long-established as growing monotonically. We quantified the
 prevalence and magnitude of non-monotonic mass change prior to fledging
 for 313 common tern chicks that successfully fledged from two discrete
 populations in multiple years. We used a new approach for analysing
 non-monotonic curves to examine differences in mass change trajectories
 between populations under contrasting abiotic (freshwater versus
 saltwater) and biotic stresses (low rates of food provisioning). 4. Some
 degree of mass recession occurred in 73% of all study chicks. Overshooting
 adult mass followed by extensive mass recession was most prevalent at our
 freshwater colony, being detected among 34 - 38% of chicks annually.
 Non-monotonic trajectories were less marked in populations experiencing
 ecological stress and among lower quality individuals. Chicks that were
 provisioned at higher rates were more likely to both overshoot adult mass
 and experience subsequent mass recession. 5. Our results provide strong
 support in common terns for the hypothesis that non-monotonic trajectories
 are the fundamental pattern of mass change but are constrained to be
 monotonic under energetic shortfall. This justifies future tests of the
 generality of this hypothesis across a broad range of taxa. We also
 demonstrate a recent analytical tool that prevents routine fitting of
 monotonic curves without prior investigation of non-monotonic trends.
description: Chick growth data from
 NLME analysisThis file contains data
 used in the NLME analysis, including 4999 mass measurements across the 313
 common tern chicks studied at two sitesin four years.Arnoldetal 2015 JAE
 NLMEdata.xlsxBrood Provisioning
 DataThis file contains data
 used in the LME analysis of brood provisioning rates, including 87
 provisioning rate observations across the 36 common tern broods studied at
 two sites in three years.Arnoldetal 2015 JAE
 BroodProvisioningdata.xlsxIndividual Provisioning
 DataThis file contains data
 used in the analysis of individual provisioning rates vs. mass
 overshooting and recession, including 15 provisioning rate observations
 “prior to peak” and across the 36 common tern broods studied at two sites
 in three years.Arnoldetal 2015 JAE
 IndividualProvisioningdata.xlsxBird Island 1971
 three-period comparisonsThis file contains
 provisioning data from Bird Island in 1971 used in in ESM 3 to demonstrate
 similarity in provisioning rate between three different time
 periods.Arnoldetal 2015 JAE Bird Island
 1971 three-period comparisons.xlsx