Black Guillemot (Cepphus grylle) Science Article 5
Colony attendance of Black Guillemots Cepphus grylle was studied at a colony on Skarveo in WestGreenland. Observations were conducted in the post hatching period by scan sampling birds in and near the colonyevery 30 minutes throughout five days. The rhythm of colony attendance varied diurnally, peaking in the earlymorning and again in late evening. The latter was the time of day with least variation between observation days. Wefound large variations in attendance levels and temporal patterns within and between three sections of the colony.For monitoring purposes the optimal census time during the post-hatching period appears to be during the eveningpeak, between 20:00 and 23:30 West Greenland summer time, i.e. between 18:30 and 22:00 local time.
Anne-Mette H. Andersen, Katrine Rahe, Signe Sveegaard andMads C. Forchhammer, Dansk Orn. Foren. Tidsskr. 103 (2009): 22-27