Phenotypic plasticity in mass loss during chick-rearing in the European starling (Sturnus vulgaris)

It has long been recognized that mass loss during breeding could be adaptive (e.g., by ameliorating the costs of increased parental activity). However, many studies still commonly interpret mass loss as evidence of “stress” or a cost of reproduction (a negative effect of high workload during chick provisioning). Despite several studies reporting evidence in support of both hypotheses, the ecological and/or life-history contexts under which mass loss may be viewed as a “cost” or an adaptive strategy are still unclear. Here, we used a long-term dataset from a breeding population of European starlings to investigate the natural annual and individual variation in body mass and mass loss and to test whether mass loss during chick-rearing represents a phenotypically plastic trait that varies predictably in relation to ecological context and individual quality. While there was significant annual variation in incubation mass, chick-rearing mass, and mass change, there were no systematic relatio..., Fieldwork was conducted at the Davistead Farm in Langley, British Columbia, Canada (49°10’N, 122°50’W) between April and July 2012–2022 using a free-living population of European starlings (Sturnus vulgaris). The field site is comprised of approximately 150 nest boxes mounted on fence posts around open pastures and on farm structures. In each year, a constant basic field protocol was followed: nest boxes were checked daily from April 1 to determine the laying date, clutch size, hatch date (day 0), and brood size at hatching, day 6, and fledging (day 21). Morphometric measures including mass, wing chord, and tarsus length were collected from adult females at day 6 incubation (6.3 ± 1.3 d) and day 10 chick-rearing (9.6 ± 1.3 d). Here, “mass loss” is defined as the difference between day 6 incubation and day 10 chick-rearing mass measures (approx. 15 days apart). Using tripod-mounted video cameras (Canon VIXIA HF R800), 30–60 min behavioral observations of chick-rearing parents were conduc..., , # Phenotypic plasticity in mass loss during chick-rearing in the European starling (*Sturnus vulgaris*)

[https://doi.org/10.5061/dryad.4j0zpc8jj](https://doi.org/10.5061/dryad.4j0zpc8jj)

**Overview**
Included is a series of six datasets (.CSV files) from data collected from a breeding population of European Starlings in Langley, British Columbia from 2012 to 2022. Data herein were used specifically to test whether mass loss may represent a phenotypically plastic trait that varies predictably in relation to ecological context and/or individual quality.

## Description of the data and file structure

### Data files

The names of each data file and a brief description of what each contains are shown below, followed by all column abbreviations used.

1. eust.data_2022.csv -- All starling data from 2012–2022 and reflects the \"master file,\" meaning it contains all general field data including, but not limited to, body mass, tarsus and wing length, lay dates, clutch and brood sizes, etc.
2....