Table 2. Top models chosen using AICc and estimated population sizes and standard errors for four experienced observers. Singing rates of the first four species were homogeneous (all birds had the same probability of calling in each interval). The next four species were heterogeneous. ACFL and SCTA are presented first when groups are modeled with unidentifiable heterogeneity (h) and second when modeled with identifiable heterogeneity (g). All species except the BAWW had a high homogeneous singing rate per interval. Observer 1 Observer 2 Observer 3 Observer 4 Species N Model Est SE Model Est SE Model Est SE Model Est SE HOWA 100 Mh 99 0.41 Mh 102 1.69 Mh 99 1.37 Mh 101 1.62 BTNW 125 M0 95 4.91 M0 97 5.29 M0 87 4.61 M0 98 5.56 YTWA 167 Mb 162 63.94 M0 123 12.13 Mb 224 163.59 Mb 161 76.54 BAWW 125 M0 106 14.79 M0 118 14.74 M0 103 14.4 M0 95 11.04 BTBW 133 Mh 93 5.3 Mh 89 2.49 Mh 95 4.58 Mth 100 5.54 OVEN 127 Mbh 89 1.36 Mh 84 1.26 Mh 99 5.29 Mbh 87 0.46 ACFL 133 Mh 96 4.62 Mh 87 4.60 Mh 91 6.12 Mh 89 4.75 SCTA 133 Mh 108 5.33 Mh 105 5.54 Mh 106 5.81 Mh 108 5.84 ACFL 133 Mg 103 8.04 Mgb 126 29.03 Mgb 98 10.77 Mg 93 5.47 SCTA 133 Mg 116 9.13 Mgb 104 10.57 Mg 114 10.18 Mg 121 12.04