NIENHUIS J (2003) Black-headed Gulls Larus ridibundus foraging at night in the city of Groningen. LIMOSA 76 (2): 75-78.

During winter nights, Black-headed Gulls often forage on discarded human food remains in the city of Groningen. This phenomenon was studied during the winters of 1999/2000 and 2000/01 on two squares in this city. At the end of the afternoon most of the gulls in the city seemed to depart to night roosts outside the city, but some remained present at Sontplein square (McDrive parking lot) and others returned to Grote Markt square late in the evening. Among these, the percentage of first winter birds, probably having more difficulties in finding food during daylight hours, was considerably higher than during the day. After rainy periods however, this percentage was lower as a result of increased numbers of adults, probably compensating for poor food availability under such conditions.

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