This paper presents the circumstances surrounding the findings and identification of the first Green Warbler Phylloscopus (trochiloides) nitidus for Sweden. The bird was caught and ringed at Ottenby Bird Observatory on May 29, 2003, but was not formally identified to subspecific level until after a DNA analysis of the collected blood-sample was conducted. This constitutes the sixth European record outside the restricted breeding area.

Data are presented on interspecific kleptoparasitism by Black-headed Gull Larus ridibundus, Common Gull L. canus, Herring Gull L. argentatus and Great Black-backed Gull L. marinus, collected in South Sweden from the late 1950s to the present day. The basis for the presentation is the various host species exploited by the four gull species. For each host species, information is given on species of gull kleptoparasitising it, seasonal occurrence of kleptoparasitism, details of behaviour and, when available, data on gulls’ success rates. The paper is intended as a sort of catalogue. For this reason, relevant literature is reviewed under each of the host-species headings. Gulls’ success rates varied between 55% for Black-headed Gulls and Common Gulls parasitising Northern Lapwings Vanellus vanellus, the most often observed kleptoparasitic association, and 15% on the few occasions that Black-headed Gulls parasitised Curlews Numenius arquata in grassland. When the same two gull species parasitised Common Starlings Sturnus vulgaris, their success rate varied with robbing tactic used (16% vs 45%). Beside the association of the two small gull species with Lapwings and Golden Plovers Pluvialis apricaria, the most frequently observed associations were those of Herring Gulls with Common Eiders Somateria mollissima and Great Black-backed Gulls and Herring Gulls with diving fish-eaters (Great Cormorant Phalacrocorax carbo, mergansers Mergus spp.). Kleptoparasitism often occurred during periods of food scarcity, being most common in harsh winter conditions (the two large gull species) and during cold spells in early spring (some associations of the two small gull species). As in other studies, gulls’ success rate was strongly dependent on the size of hosts’ prey, and thus, normally on handling time. It is suggested that success rate can often be used as a substitute for profitability in studies of kleptoparasitism.

Birds must store fuel prior to the crossing of the Sahara desert, at least 1,500 km with few refuelling possibilities. A major question is how inexperienced birds know where to prepare for the oncoming barrier. Experiments with caged birds showed that information from the Earth’s magnetic field close to the desert might trigger extensive fuel deposition. Blackcaps Sylvia atricapilla trapped on Cyprus in September and October were much heavier than in Sweden during the early phase of autumn migration, typical for birds preparing for crossing the Sahara desert. There is a potential cost of being fat. Fat Sedge Warblers Acrocephalus schoenobaenus on Lesvos had much poorer take off abilities than lean birds, making them more vulnerable to predators. Swallows Hirundo rustica trapped at a roost site on Rhodes showed a synchronized body mass increase and this is in agreement with their wavelike pattern of passage on Crete. In recent years, studies of fuelling behaviour and stopover duration of first-year Garden Warblers Sylvia borin have been started on Crete with the aid of radio-transmitters.

Autumn ringing totals from Falsterbo, SW Sweden, and Ottenby, SE Sweden, and data from the Breeding Bird Census were compared in 37 species during 1980—1999. We compared both 20-year trends (continuity of changes) and mean totals for the 1980s and 1990s, respectively. The three programmes showed similar patterns in many species. More species showed decreasing than increasing trends. There were no significant differences in the number of significant trends between the three programmes or between the numbers of significantly decreasing trends among long-distance and other categories of migrants. The two-decade comparison showed more negative changes among long-distance than among other migrants at Falsterbo, and long-distance migrants decreased most at Falsterbo and least in Point Counts. Possible reasons for the differences are (a) different populations, especially between Falsterbo and Ottenby, (b) trends in partial migrants may not be detected in ringing totals, (c) non-random route selection in Point Counts, (d) difficult to count very common species in Point Counts, and (e) decreases of more species in Western than in Eastern Europe, affecting Falsterbo.

We investigated concentration of mercury in eggs of Red-throated Diver Gavia stellata and Black-throated Diver Gavia arctica collected in South and Central Sweden, 1981—1997. In South Sweden (Sydsvenska Höglandet), mean concentration in Red-throated Diver eggs was remarkably high (6.84 ppm dry weight, 5 pairs), or more than three times as high as in Black-throated Diver eggs (2.11 ppm dry weight, 16 pairs). In Central Sweden (Svealand), the concentration in Red-throated Diver eggs (3.04 ppm dry weight, 8 pairs) was significantly lower than in South Sweden, but still higher than in Black-throated Diver eggs (1.21 ppm dry weight, 5 pairs). In Black-throated, but not in Red-throated Diver, there was higher mercury concentrations in eggs from pairs fishing in lakes affected by acidification. We found no relationship between mercury and breeding success, although concentrations in single Red-throated Diver eggs exceeded the level associated with high risk of impaired reproduction. We recommend that mercury concentration of diver eggs should be further monitored, with reference to the risks of increased exposure, related to leakage from terrestrial deposits of air-borne transmissions to freshwater habitats.