A double-observer approach was used during colony surveys of large gulls to estimate nest detection probabilities and unbiased estimates of abundance. Several models were developed that incorporate different assumptions about the sources of variation in detection probabilities (observer, colony, vegetation height). Nine colonies were surveyed in which a total of 137 transects were conducted. Although the most likely model was a one with a constant nest detection probability, a constrained model with observer dependent nest detection probability had substantial support. Overall detection probability (probability that a nest was detected by at least one of the two observers) was 0.943 (SE ± 0.008). Detection probability for a single observer was lower (0.761, SE ± 0.016). These estimates indicate a relatively high underestimation of the population sizes of large gull species when not taking into account nest detectability.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 28 • No. 1