Finding a mate of high quality is of key importance for reproducing birds, and thus positive assortative mating is commonly observed in avian populations. Although assortative mating by age, body size, condition or ornamental traits was reported for many bird taxa, there is a scarcity of empirical evidence for such mating patterns in wildfowl. We studied mating patterns in the Mute Swan Cygnus olor from the Central-European population. We analysed four body measurements (total wing length, forearm length, head length, foot web width) in 91 different breeding pairs. Contrary to our expectations, we found no evidence for assortative mating by any of the collected biometrical measurements and by overall structural size (PC1 from all measured skeletal traits). Further, Mute Swans mated randomly by the size of bill knob, which is considered a sexually selected ornament in this species. We suggest that in the species with long-term pair bonds and monogamous breeding system, such as the Mute Swan, the benefits from large size of mates may be less important for positive reproductive output than other individual traits, e.g., age or previous breeding experience.
Mute Swan Cygnus olor numbers have recently increased in a dramatic fashion in Western Europe and in North America, suggesting there could be potential consequences for the rest of the waterbird community. Breeding Mute Swan pairs may behave territorially towards other waterbirds, taking advantage of their larger size, and hence cause concern regarding their potential effects on waterbird communities. We studied how the within-site distributions of breeding Mute Swans and other waterbirds were related to each other, in order to assess if there is support to the assertion that breeding Mute Swans may affect the distribution of the other waterfowl within waterbodies. We mapped waterbird and swan distribution within fishponds during the Mute Swan breeding period. Relying on spatial point pattern analysis, our first finding is that breeding Mute Swans were located in the vicinity of the other waterbirds, using the same area within fishpond. Waterbirds do not completely desert the area used by breeding swan pairs within a waterbody, hence not supporting the claim that Mute Swans dislodge the other species. If an exclusion process by Mute Swan breeding pairs towards waterbirds exists, it is not strong enough to generate deserted areas by waterbirds around breeding Mute Swans. Our second finding is that breeding Mute Swans were not located where the density probability function for waterbird presence was the greatest within a fishpond, i.e. breeding Mute Swans were not located in the centre of groups formed by other waterbirds within each fishponds. This may indicate slightly different micro-habitat preferences or use within fishponds, or could indicate the potential occurrence of interactions. In conclusion, these results question whether the increasing Mute Swan populations actually directly threaten the other waterbird communities in such habitats, and require population control as is often claimed.
Time activity patterns of wintering Mute Swans were studied over three seasons in and near Cracov using the focal bird sampling method. In the city the swans were fed by people, while outside the city the birds were not fed by people. Rural Mute Swans spent 48.1% of the daytime eating, while urban swans fed only 4.6% and begged 8.7% of the time. Urban birds spent more time swimming and loafing (28.3 and 36.1%, respectively) than rural birds (10.2 and 18.4%). The daily activity pattern for rural swans was generally bimodal with early morning and late afternoon peaks in feeding, and a mid-day resting period. In contrast, the swans in Cracov did not show any cycle in diurnal feeding activity. There were differences in the frequencies of aggressive behaviour between urban and rural swans. In the city aggression occurred much more often. The behaviour of urban swans during the night was very similar to nocturnal activities of rural swans. The activity pattern of swans wintering in Cracov is probably mainly due to adaptations to the feeding by people.
Following the spread from its origins in China, Asian lineage highly pathogenic avian influenza H5N1 was first recorded in Europe in Turkish poultry and in poultry and wild birds in Romania in early October 2005. On 19 October 2005 Croatia became the second European country to record an outbreak in wild birds, involving Mute Swans Cygnus olor. Subsequent surveillance in Croatia revealed further instances of H5N1 in dead and sick Mute Swans in 2005, and in 2006 in more dead Mute Swans and in living, apparently healthy, Black-headed Gulls Larus ridibundus, but not in poultry. The observations presented here suggest that Croatia experienced two independent incursions of Asian lineage HPAI H5N1, but genetic confirmation is not available. Potential routes of introduction by wild birds, the poultry industry and fish-farming practices are discussed, but the evidence for all of these remains circumstantial