DOI: 10.5061/dryad.2547d7x2h
title: Variation in wing and tail moult intensity in white-chinned Petrels

description: The cost of moult is substantial, and the timing and intensity of flight
 feather moult can influence survival and fitness, especially in large,
 long-winged species such as many seabirds. We explore variation in wing
 and tail moult in &gt; 2400 White-chinned Petrels Procellaria
 aequinoctialis killed in fisheries off southern Africa to assess how they
 integrate moult into their annual cycle and whether wing moult impacts
 their behaviour at sea. All petrels showed a simple descendent primary
 moult and one active moult centre, although moult of P2-3 sometimes
 started before P1. The Underhill‐Zucchini moult model estimated that adult
 primary moult started after breeding on 7 May (± 8 days SD) and lasted 103
 days (mean end date 20 August ± 10 days). Adult moult was particularly
 intense in the inner primaries, growing up to six feathers at once.
 Secondary moult started two weeks after primary moult, once 3–4 primaries
 had been dropped. Secondary moult typically started with the innermost
 secondaries, plus inward waves from S1 and S5 in 2.7 ± 1.3 active moult
 centres, replacing 4.6 ± 2.7 (1–13) secondaries at once. Adults had more
 intense secondary moult than immatures. However, photographs of
 non-moulting birds at sea show that 27% of birds do not replace all
 secondaries each year. Tail moult usually commenced with the start of
 secondary moult and was highly variable, with 1–12 rectrices growing at
 once. Although adult wing moult was intense, there was no marked reduction
 in flight activity among breeding adults fitted with leg-mounted activity
 loggers during the moult period. Our findings largely accord with previous
 studies of moult in petrels, but our large sample size reveals
 considerable variation among individuals, which is surprising given the
 high cost of moult. Future studies should attempt to investigate the
 factors determining this variation.
description: # Variation in wing and tail moult intensity in white-chinned Petrels
 [https://doi.org/10.5061/dryad.2547d7x2h](https://doi.org/10.5061/dryad.2547d7x2h) ## Description of the data and file structure The data were collected to investigate the moult patterns and their implications for White-chinned Petrels (*Procellaria aequinoctialis*) accidentally caught as bycatch in long-line fisheries off southern Africa. Observations of breeding adults on Marion Island supplemented data on the onset of moult, and photographs of birds in flight were used to examine incomplete secondary moult. Additionally, activity data from GLS loggers were analysed to assess the potential impacts of moult on daily flight time. ### Files and variables #### File: Activity\_Data\_for\_Bird\_1.xlsx **Description:**  ##### Variables * date: The observation date in the format DD-MM-YYYY. * length: The duration of time spent on water (seconds per day). * wd: The wet/dry activity state recorded * month: The month of the observation. * day: The day of the observation. * year: The year of the observation. #### File: Activity\_Data\_for\_Bird\_2.xlsx **Description:**  ##### Variables * date: The observation date in the format DD-MM-YYYY. * length: The duration of time spent on water (seconds per day). * wd: The wet/dry activity state recorded * month: The month of the observation. * day: The day of the observation. * year: The year of the observation. #### File: Activity\_Data\_for\_Bird\_3.xlsx **Description:**  ##### Variables * date: The observation date in the format DD-MM-YYYY. * length: The duration of time spent on water (seconds per day). * wd: The wet/dry activity state recorded * month: The month of the observation. * day: The day of the observation. * year: The year of the observation. #### File: Activity\_Data\_for\_Bird\_4.xlsx **Description:**  ##### Variables * date: The observation date in the format DD-MM-YYYY. * length: The duration of time spent on water (seconds per day). * wd: The wet/dry activity state recorded * month: The month of the observation. * day: The day of the observation. * year: The year of the observation. #### File: Activity\_Data\_for\_Bird\_5.xlsx **Description:**  ##### Variables * date: The observation date in the format DD-MM-YYYY. * length: The duration of time spent on water (seconds per day). * wd: The wet/dry activity state recorded * month: The month of the observation. * day: The day of the observation. * year: The year of the observation. #### File: Activity\_Data\_for\_Bird\_6.xlsx **Description:**  ##### Variables * date: The observation date in the format DD-MM-YYYY. * length: The duration of time spent on water (seconds per day). * wd: The wet/dry activity state recorded * month: The month of the observation. * day: The day of the observation. * year: The year of the observation. #### File: Primaries.csv **Description:**  ##### Variables * year:  The year of the observation. * month:  The month of the observation. * date: The observation date in the format YYYY-MM-DD. * sex: M - Male, F - Female * age: imm - Immature, ad - Adult and juv - Juvenile * P1: 1st primary (innermost) * P2: 2nd primary * P3: 3rd primary * P4: 4th primary * P5: 5th primary * P6: 6th primary * P7: 7th primary * P8: 8th primary * P9: 9th primary * P10: 10th primary * n/a = not available as it was impossible to sex or age some individuals #### File: Secondaries.csv **Description:**  ##### Variables * day: The day of the observation. * month: The month of the observation. * year: The year of the observation. * date: The observation date in the format DD/MM/YYYY. * sex: M - Male, F - Female * age: imm - Immature, ad - Adult and juv - Juvenile * S1: 1st secondary * S2: 2nd secondary * S3: 3rd secondary * S4: 4th secondary * S5: 5th secondary * S6: 6th secondary * S7: 7th secondary * S8: 8th secondary * S9: 9th secondary * S10: 10th secondary * S11: 11th secondary * S12: 12th secondary * S13: 13th secondary * S14: 14th secondary * S15: 15th secondary * S16: 16th secondary * S17: 17th secondary * S18: 18th secondary * S19: 19th secondary * S20: 20th secondary * S21: 21st secondary * S22: 22nd secondary * S23: 23rd secondary * S24: 24th secondary * S25: 25th secondary * n/a = not available as it was impossible to sex or age some individuals #### File: Tail.xlsx **Description:**  ##### Variables * day: The day of the observation. * month: The month of the observation. * year: The year of the observation. * date: The observation date in the format DD/MM/YYYY. * T1R: central tail feather on the right * T2R: 2nd tail feather from the centre away from the body (on the right) * T3R: 3rd tail feather from the centre away from the body (on the right) * T4R: 4th tail feather from the centre away from the body (on the right) * T5R: 5th tail feather from the centre away from the body (on the right) * T6R: 6th tail feather from the centre away from the body (on the right) - outermost on the right * T1: central tail feather on the left * T2: 2nd tail feather from the centre away from the body (on the left) * T3: 3rd tail feather from the centre away from the body (on the left) * T4: 4th tail feather from the centre away from the body (on the left) * T5: 5th tail feather from the centre away from the body (on the left) * T6: 6th tail feather from the centre away from the body (on the left) - outermost on the left * n/a = not available as it was impossible to sex or age some individuals ## Code/software * **R Programming Language** ([https://www.r-project.org/](https://www.r-project.org/)) * **Packages Used**: * tidyverse: For data manipulation and visualization. * moult: To analyse moult data. * ggplot2: For generating plots and visualizations. * dplyr: For filtering and summarizing data. ## Supplementary Materials * **Primary, Secondary and Tail moult** * **Sex differences** – Sex-based differences in moult strategies within primary, secondary, and tail feathers. * **Number of moult centres** – Overview of observed moult centres within primary, secondary, and tail feathers. * **Number of growing primaries** – Data on the number of growing primaries, secondaries and tail feathers. * **Wing covert moult** – Observations on moult in the secondary coverts. * **Supplemental Table 1: **The** **average** **(± SD)** **mass** **(mg)** **and length** **(mm)** **of fully grown White-chinned Petrel** **primaries,** **secondaries** **and** **rectrices** **(n = 4)** **killed by fishing operations. * **Supplemental Table 2: **Moult scores of White-chinned Petrels** **growing inner primaries (n = 25) where replacement may not have been sequential from P1 outwards. Scores follow Ginn and Melville (1983): 0 = old feathers, 1–4 = growing feathers at increasing stages of development, and 5 = fully-grown new feathers. * **Supplemental Table 3: **The number of adult and immature, and female and male White-chinned Petrels** **growing primaries, among 538 non-juvenile birds accidentally caught by fishing vessels off southern Africa from 2002-2020. * **Supplemental Table 4: **The number of adult and immature, and female and male White-chinned Petrels** **growing secondaries, among 323 non-juvenile birds accidentally caught by fishing vessels off southern Africa from 2002-2020. * **Supplemental Table 5: **The number of adult and immature, and female and male White-chinned Petrels** **growing rectrices, among 261 non-juvenile birds accidentally caught by fishing vessels off southern Africa from 2002-2020. * **Supplemental Figure 1:** Mixture of new and old secondaries and secondary coverts in a non-moulting, presumably adult White-chinned Petrel (photo Peter Ryan). * **Supplemental Figure 2:** Proportion of secondary moult scores in relation to primary moult scores of (A) adult and (B) immature White-chinned Petrels accidentally caught by fishing vessels off southern Africa. Sample sizes for the largest sample point in (A) is 168 and in (B) is 88. * **Supplemental Figure 3:** Proportion of moult scores of rectrices in relation to (A) primary moult scores; and (B) secondary moult score of White-chinned Petrels accidentally caught by fishing vessels off southern Africa. Sample sizes for the largest sample point in (A) is 148 and in (B) is 75.