Table 5: Comparison of avian monitoring projects focused on measuring occurrence and abundance (adapted from [10]).

Results from these programs have been used in over 1000 publications Project Method Placement Efforta Extent Interval Participants Audubon Christmas Bird Count Count circle (24 km diameter) Opportunistic V (party hours) International Annual 59,918 (2008-09) North American Breeding Bird Survey Roadside survey (39.4 km; 50 stops) Stratified random S (3 min count) International Annual 2,749 (2009) Project FeederWatch Feeder counts Opportunistic V (2 days, hours, days) International Annual 9,750 (2009) eBird Online checklists Opportunistic V (hours, distance, and area) International Continuous 18,053 Bird Atlas Systematic grid (100 km2 blocks; 4 km2 tetrads) and roving reports Regular grid and opportunistic S/V (roving, timed visits) Britain and Ireland Two visits (Winter: Nov./Dec. & Jan./Feb.; Breeding: April/May & June/July) 10,000–20,000 Common Birds Census (now replaced by Breeding Bird Survey) Census plots (Farmland: 70 ha; Woodland: 20 ha) Stratified random S (territory mapping) Britain Annual (8–10) visits; late March–early July) 250–300

a Effort is considered standardised (S) or variable (V). When standardised, the protocol specifications are presented; when variable, the effort variables that were reported during sampling are presented.