Fig. 1
From: Nest site tenacity and mate fidelity in the Black-headed Gull (Chroicocephalus ridibundus)
Number of breeding pairs of Black-headed Gull (C. ridibundus) on Böhmke Island (triangles) and Riether Werder (circles) estimated by the annual monitoring. Data from monitoring programs provided by Wilfried Starke (Böhmke Island) and Frank Joisten (Riether Werder)