DOI: 10.5061/dryad.7jd76kq
title: Data from: Scrutinizing assortative mating in birds

description: It is often claimed that pair bonds preferentially form between
 individuals that resemble one another. Such assortative mating appears to
 be widespread throughout the animal kingdom. Yet it is unclear whether the
 apparent ubiquity of assortative mating arises primarily from mate choice
 (‘like attracts like’) which can be constrained by same-sex competition
 for mates, from spatial or temporal separation, or from observer,
 reporting, publication or search bias. Here, based on a conventional
 literature search, we find compelling meta-analytical evidence for
 size-assortative mating in birds (r = 0.178, 95% CI: 0.142 – 0.215, 83
 species, 35,591 pairs). However, our analyses reveal that this effect
 vanishes gradually with increased control of confounding factors.
 Specifically, the effect size decreased by 42% when we used unpublished
 data from nine long-term field studies, i.e. data free of reporting and
 publication bias (r = 0.103, 95% CI: 0.074 – 0.132, eight species, 16,611
 pairs). Moreover, in those data assortative mating effectively disappeared
 when both partners were measured by independent observers or separately in
 space and time (mean r = 0.018, 95% CI: -0.016 – 0.057). Likewise, we also
 found no evidence for assortative mating in a direct experimental test for
 mutual mate choice in captive populations of zebra finches (r = -0.020,
 95% CI: -0.148 – 0.107, 1,414 pairs). These results highlight the
 importance of unpublished data in generating unbiased meta-analytical
 conclusions, and suggest that the apparent ubiquity of assortative mating
 reported in the literature is overestimated and may not be driven by mate
 choice or mating competition for preferred mates.
description: S1_Data.xlsxUnpublished data (nine long-term field studies): All the pairs that have been identified across the nine studies where both pair members have at least one morphological record, including repeated records from different years. This dataset also includes latitude and longitude of the nest site (Lambert azimuthal equal-area projection, units = meters) and year and, if available, the putative date of the first egg.Supplementary_file_1_unpublished_data1.xlsxS2_Data.xlsxUnpublished data (nine long-term field studies): All available records of morphological traits which covered more than 95% of individuals included in S1_Data.This dataset also includes the location where the individual was caught, the date of catching, and the observer who measured the individualSupplementary_file_2_unpublished_data2.xlsxS3_Data.xlsxUnpublished data (nine long-term field studies): Data where we combined the information from data S1_Data and S2_DataSupplementary_file_3_unpublished-data3.xlsxS4_Data_xlsxPublished data (Fig 1A): Excel spreadsheet containing two separate sheets with data from literature: 1) data extracted from the publications and 2) the original references.Literature_data.xlsxS5_Data_xlsxData for Fig 1B: Strength of assortative mating for size as a function of data source.Pearons_r_different_data_sources_integrated_mixed_model.xlsxS6_Data_xlsxModels for the unpublished data (Fig 1C): Excel spreadsheet contains 6 separate sheets; each sheet corresponds to a model to estimate the strength of assortative mating.Models_of_unpublished_data.xlsxS7_Data,xlsxData for Fig 2: Strength of assortative mating for body size in relation to sample size.Funnel_plot_asymmetry_test.xlsxS8_Data.xlsxExperimental data on zebra finches. The zebra finches data include five experiments.Experimental data_zebra_finch.xlsxPRISMA_literature summaryThe process of literature investigation.PRISMA_summary of literature.docx