Table 1. Description of data sources on gender patterns in bird-related recreation projects divided into four groups based on the degree of competition (Supportive, Participatory, Competitive, and Authoritative).

Sources of Data Description
Supportive – Membership in the following organizations
CLO The Cornell Lab of Ornithology was founded in 1915 and its mission is to interpret and conserve the Earth's biological diversity through research, education, and citizen science focused on birds.
Audubon Society Audubon's mission is to conserve and restore natural ecosystems, focusing on birds, other wildlife, and their habitats for the benefit of humanity and the Earth's biological diversity.
RSPB The Royal Society for the Protection of Birds, which was founded in 1889, is a British charitable organization that promotes conservation and protection of birds, wildlife, and the environment through public awareness campaigns, petitions, and the operation of nature reserves in the UK.
BTO The British Trust for Ornithology was established in 1933 as an independent, scientific research trust, investigating the populations, movements, and ecology of wild birds in the UK, with specialty in the design and implementation of volunteer wild bird surveys.
   
Participatory – Participation in the following citizen science projects
CUBs Celebrate Urban Birds is a year-round project to promote conservation in cities through gardening, the arts, and checklists of focal species based in the USA.
HFDS The House Finch Disease Survey works in conjunction with Project FeederWatch and relies on participants watching bird feeders to report the presence and absence of signs of avian conjunctivitis, which is visible as red swollen eyes.
NestWatch A nest-monitoring project that collects breeding data on all North American breeding birds.
Project FeederWatch A winter-long survey of birds that visits feeders anywhere in North America, and in which participants submit records every other week and pay a fee to join.
CamClickr An online photo-tagging project to identify breeding behaviors in archived photos of nesting birds based in the USA.
BFL Birds in Forested Landscapes is a breeding bird survey project focused on North American forest songbirds that uses audio playback to determine the presence or absence of breeding songbirds.
CBC Christmas Bird Count is an annual winter count of birds across North America that began in 1900.
EBird A year-round bird checklist project based in the USA.
Garden Birdwatch A year-round survey of birds in UK gardens in which participants submit records weekly and pay a fee to join.
BBS (UK) Breeding Bird Survey is grid-based survey of breeding birds in the UK.
Nest Record Scheme A nest-monitoring project that gathers breeding data on birds in the UK.
   
Competitive – Membership and participation in the following listing organizations
American Birding Association A nonprofit organization that provides leadership to birders by increasing their knowledge, skills, and enjoyment of birding. Compile all record Birding Achievements, such as Year Lists, Day Lists, County Lists, etc.
UK400Club A club within the British Birding Association to cater to the more discerning birder, and strives to maintain the Life Lists of the Top 900UK, top 500 Western Palearctic, and Top 1,000 World listing birders. Compile all record birding achievements, such as Year Lists, Day Lists, County Lists, etc,
   
Authoritative – Acknowledged authorities on birding
eBird state reviewers eBird flags records based on the values, or filter limits, set for each species in each regional filter. State reviewers assess these flagged records to make a determination on whether the record is valid.
CBC Regional Editors Regional editors for the North American CBC compile data from CBC participants for their assigned regions.
Birding Advice Book Recent book edited by White and Dunne (2007) providing advice from “North America’s Top Birders.”
Bird Ringing BTO bird ringing scheme trains and licenses participants to place identification rings on wild birds.