DOI: 10.5061/dryad.9sk18
title: Data from: Double brooding and offspring desertion in the barn owl (Tyto alba)

description: Many bird species produce two annual broods during a single breeding
 season. However, not all individuals reproduce twice in the same year
 suggesting that double brooding is condition-dependent. In contrast to
 most raptors and owls, the barn owl Tyto alba produces two annual clutches
 in most worldwide distributed populations. Nevertheless, the determinants
 of double brooding are still poorly studied. We performed such a study in
 a Swiss barn owl population monitored between 1990 and 2014. The annual
 frequency of double brooding varied from 0 to 14% for males and 0 to 59%
 for females. The likelihood of double brooding was higher when individuals
 initiated their first clutch early rather than late in the season and when
 males had few rather than many offspring at the first nest. Despite the
 reproductive benefits of double brooding (single- and double-brooded
 individuals produced 3.97 ± 0.11 and 7.07 ± 0.24 fledglings,
 respectively), double brooding appears to be traded off against offspring
 quality because at the first nest double-brooded males produced poorer
 quality offspring than single-brooded males. This might explain why
 females desert their first mate to produce a second brood with another
 male without jeopardizing reproductive success at the first nest.
 Furthermore, the reproductive cycle being very long in the barn owl (120 d
 from start of laying to offspring independence), selection may have
 favoured behaviours that accelerate the initiation of a second annual
 brood. Accordingly, half of the double-brooded females abandoned their
 young offspring to look for a new partner in order to initiate the second
 breeding attempt, 9.48 d earlier than when producing the second brood with
 the same partner. We conclude that male and female barn owls adopt
 different reproductive strategies. Females have more opportunities to
 reproduce twice in a single season than males because mothers are not
 strictly required during the entire rearing period in contrast to fathers.
 A high proportion of male floaters may also encourage females to desert
 their first brood to re-nest with a new male who is free of parental care
 duties.
description: 2ndClutch_Male_2014This table contains data on the number of annual clutch (1 or 2 annual) produced by males during 1990-2014 in a population of barn owls in western Switzerland. For each clutch you will find the different breeding parameters (laying date, clutch size, number of fledglings, breeding site) and information on the individuals and their partner (age, ringing status,…).2ndClutch_Female_2014This table contains data on the number of annual clutch (1 or 2 annual) produced by females during 1990-2014 in a population of barn owls in western Switzerland. For each clutch you will find the different breeding parameters (laying date, clutch size, number of fledglings, breeding site) and information on the individuals and their partner (age, ringing status,…).Nestling_Condition_2ndClutch_FemalesThis table contains information on the condition of nestlings (mass, wing, age) in relation to annual breeding parameters (1 or 2 annual clutch, laying date, clutch size, number of fledglings, …) of females. These data were collected between 1990 and 2014 in western Switzerland.Nestling_Condition_2ndClutch_MalesThis table contains information on the condition of nestlings (mass, wing, age, etc…) in relation to annual breeding parameters (1 or 2 annual clutch, laying date, clutch size, number of fledglings, …) of males. These data were collected between 1990 and 2014 in western Switzerland.Nestling_Condition_2ndClutch_Male.txt