varieties of song type, which follow each other in a regular order without pause. The bout starts with a series of pure-tone whistles and these are followed by the main part of the song, a number of variable sequences that often incorporate snatches of song mimicked from other species of bird and various naturally occurring or man-made noises. The structure and simplicity of the sound mimicked is of greater importance than the frequency with which it occurs. In some instances, a wild starling has been observed to mimic a sound it has heard only once. Each sound clip is repeated several times before the bird moves on to the next. After this variable section comes a number of types of repeated clicks followed by a final burst of high-frequency song, again formed of several types. Each bird has its own repertoire with more proficient birds having a range of up to 35 variable song types and as many as 14 types of clicks. Males sing constantly as the breeding period approaches and perform less often once pairs have bonded. In the presence of a female, a male sometimes flies to his nest and sings from the entrance, apparently attempting to entice the female in. Older birds tend to have a wider repertoire than younger ones. Those males that engage in longer bouts of singing and that have wider repertoires attract mates earlier and have greater reproductive success than others. Females appear to prefer mates with more complex songs, perhaps because this indicates greater experience or longevity. Having a complex song is also useful in defending a territory and deterring less experienced males from encroaching. Along with having adaptions of the skull and muscles for singing, male starlings also have a much larger syrinx than females. This is due to increased muscle mass and enlarged elements of the syringeal skeleton. The male starling's syrinx is around 35% larger than its female counterpart. However, this sexual dimorphism is less pronounced than it is in songbird species like the zebra finch, where the male's syrinx is 100% larger than the female's syrinx. Singing also occurs outside the breeding season, taking place throughout the year apart from the moulting period. The songsters are more commonly male although females also sing on occasion. The function of such out-of-season song is poorly understood. Eleven other types of call have been described including a flock call, threat