SPAANS A (2000) High winter site-fidelity of Black-headed Gulls Larus ridibundus in The Hague. LIMOSA 73 (3): 87-96.

I investigated winter site-fidelity of 194 individually colour-ringed Black-headed Gulls at a pond in the city Centre of The Hague during two winters in the early 1960s. All birds were caught by hand in flight when taking bread from the hand except one first-year bird taken by hand when resting on a pillar. Numbers of gulls at the study site strongly increased during October, peaked during frost periods and strongly decreased during March (Fig. 1). During the winter, the population comprised 93-98% second year and 01der gulls. The gulls originated trom bath Dutch and foreign breeding populations (Tab. 1). A total of 57% were seen at the study site during the same winter, while 52% were observed here in later winters (Tab. 2). Colour-ringed birds were seen at the study site from October through March, with same odd birds in April (Figs. 2-4). In later winters return rates ot gulls caught during frost were lower than those of birds ringed before frost started. Gulls caught during frost returned also later in the season (Fig. 5), stayed shorter periods of time (Fig. 4) and were less frequently seen each winter (Fig. 6) than birds caught before frost started. In contrast to the birds that were caught during mild weather, the birds caught during frost were recovered from several sites outside The Hague, but mainly within the distribution area of the roost that the gulls from The Hague used (Tab. 3). Based on the relatively high proportion of adult birds in the winter population it is assume that the feeding conditions at the Hofvijver were better than on average in The Hague. It is therefore suggested that the birds which took refuge to the study site during frost periods might have been birds of a poorer quality. Return rates in later winters (59% on average, maximum 71 %, after correcting for an annual mortality of 16%) were high but comparable with return rates for several other urban areas in EuropeBlack-headed Gull Chroicocephalus ridibundus = Larus ridibundus

[free pdf] [dutch summary]