DOI: 10.5061/dryad.gtht76hrg
title: Position in the laying order has sex-specific consequences for reproductive success in adult black-headed gulls

description: Mothers who produce multiple offspring within one reproductive attempt
 often allocate resources differentially; some maternally-derived
 substances are preferentially allocated to last-produced offspring and
 others to first-produced offspring. The combined effect of these different
 allocation regimes on the overall fitness of offspring produced early or
 late in the sequence is not well understood, partly because production
 order is often coupled with birth order, making it difficult to separate
 effects of pre-natal maternal allocation from those of post-natal social
 environments. In addition, very little is known about the influence of
 laying order on fitness in later-life. In this study, we used a
 semi-natural captive colony of black-headed gulls to test whether an
 offspring’s position in the laying order affected its early life survival
 and later life reproductive success, independent of its hatching order.
 Later-laid eggs were less likely to hatch, but among those that did,
 survival to adulthood was greater than that of first-laid eggs. In
 adulthood, the laying order of females did not affect their likelihood of
 breeding in the colony, but male offspring hatched from last-laid eggs
 were significantly less likely to gain a breeding position than
 earlier-laid males. In contrast, later-laid female parents hatched lower
 proportions of their clutches than first-laid females, but hatching
 success was unrelated to the laying order of male parents. Our results
 indicate that gull mothers induce complex and sex-specific effects on both
 the early survival of their offspring and on long-term reproductive
 success through laying order effects among eggs of the same breeding
 attempt.
description: Data were collected from a captive population of wild-type
 black-headed gulls between 2012 and 2021. Each year, breeding attempts in
 the colony were monitored to collect data on egg laying order, hatching
 success, survival of offspring, and among adults, various reproductive
 parameters such as breeding status and nesting success. Data pertaining to
 each individual were collated in excel.
description: Microsoft excel, R.
description: # Title of Dataset: Position in the laying order has sex-specific
 consequences for reproductive success in adult black-headed gulls Dataset
 contains 3 excel files: 1. Early survival BreedPair: unique identifier for
 breeding pair ID: unique identifier for individual egg Year: calendar year
 of laying EggLumped: order in the laying sequence of the individual egg.
 Factor with 4 levels (A-CD) Hatched: binary coding for whether the egg
 hatched (1) or not (0) Survived: binary coding for whether the nestling
 inside the egg survived (1) or not (0) to independence at one year old
 IncludeSurvivalAnalysis: binary coding for whether this egg was included
 (1) or not (0) in the analysis of survival to 1 year (see article for
 description of inclusion criteria). 2. Breeding position Colour rings:
 unique identifying code for individual Sex: molecular sex binary (0 =
 female, 1 = male) BirthYear: calendar year of hatching NatalNest: unique
 identifier for breeding pair that produced the focal individual Age2021:
 age of individual in calendar year 2021 EggOrderLumped: order in the
 laying sequence of the individual egg. Factor with 4 levels (A-CD)
 HatchOrder: order of emergence from the egg in the laying sequence
 BecameBreeder? Binary coding whether individual did (1) or did not (0)
 gain a breeding position AFR: age in years at which individual first
 reproduced 3. Reproductive success Bird: unique identifying code for
 individual Sex: molecular sex binary (0 = female, 1=male) NatalNest:
 unique identifier for breeding pair that produced the focal individual
 EggOrderLumped: order in the laying sequence of the individual egg. Factor
 with 4 levels (A-CD) EggOrderNumeric: same data as EggOrderLumped but
 coded as numeric between 1 and 4 HatchOrder: order of emergence from the
 egg in the laying sequence BreedingYear: calendar year in which
 information on reproductive success was recorded Experiment: Binary coding
 for whether eggs were experimentally removed (1) or not (0) from the pair
 CS: clutch size, number of eggs Nhatch: number of eggs that hatched
 Nfledge: number of nestlings that survived to independence Also included
 are two R scripts: 1. main analyses 2. power anayses for non-siginificant
 results ## Description of the data and file structure Each row in the
 excel files is an individual data point (either an egg or an individual
 bird, depending on the analysis). Please see the above description of the
 files for information about the contents of each file and what each column
 refers to. All datafiles are related and derive from the same population
 of animals.