Table 2: Truncation distance (w), number of detections (n), detection probability beyond 300 m, fitted detection model, goodness of fit assessment (see Methods), detection probability (P, with its % CV), and difference in density estimates and coefficient of variation between 300 m and 1000 m wide line-transects, by survey type, species and behavior group for data collected during five seabirds at-sea surveys in the Gulf of St. Lawrence in 2009 and 2010. Goodness of fit statistics were classified as poor (α < 0.05) and good otherwise.

Survey type Species Behavior w n Detection Probability (300 - 1000 m) Model1 Goodness of fit P %CV (P) Diff. in estimated density (birds/km2) with untruncated data Diff. in coefficient of variation with untruncated data
Line- transect Aerialists Fly 1000 2497 0.082 HN Cos (2) Poor 0.23 21
Swim 1000 553 0.058 HR SP Good 0.19 12
Alcids Fly 1000 830 0.093 HR SP Good 0.17 14
Swim 1000 414 0.023 HR SP Good 0.17 14
Point- transect Aerialists Fly 1000 2497 0.084 HN Cos Poor 0.13 11
Swim 1000 429 0.061 UNI SP Marginal (p=0.072) 0.15 14
Alcids Fly 1000 830 0.264 HN Cos + Observer Good 0.19 17
Swim 1000 326 0.024 UNI SP Poor 0.10 9
Line- transect Aerialists Fly 300 1841 - HN Cos (2) obs + wind Good 0.52 2 0.190 -0.006
Swim 300 427 - HN Cos (2) obs + wind Good 0.49 46 0.005 -0.140
Alcids Fly 300 594 - HN Cos (2) obs + wind Good 0.43 40 -0.041 -0.087
Swim 300 364 - HN Cos (2) obs + wind Good 0.55 51 -0.002 -0.009
Point- transect Aerialists Fly 300 949 - HN Cos (2) obs Poor 0.47 2 0.373 -0.211
Swim 300 248 - Uniform Poor 1.00 0 0.019 -0.015
Alcids Fly 300 306 - UNI Cos Poor 0.76 12 -0.051 0.066
Swim 300 225 - HN Cos (2) obs + wind Marginal 0.59 44 0.137 0.089

1 Abbreviations describe key functions uniform (UNI), half-normal (HN), and hazard-rate (HR) and expansion terms cosine (Cos), simple polynomial (SP), and hermite polynomial (HP). Covariates that were selected in MCDS models included: observer (obs), seastate (following Beaufort scale), and wind speed in knots (wind).