Ring Ouzel Study Group

Glen Clunie Ring Ouzel Breeding Ecology Project

Summary of Results 1998-2004

Part 3

Brood size

As for clutch size, brood size at fledging was consistent over the seven-year period. Mean brood size was 3.67 for early nests and 3.63 for late nests, with broods of four the most common (Fig. 4). Again, there was some evidence that late broods were more variable in size, but no evidence that brood size decreased later in the season.

Nest survival rates

Using Mayfield estimates (Bart & Robson 1982), nest survival rates were higher at the chick stage than the egg stage in all years except 2003 (Fig. 5). The seven-year mean survival rates were 66% for the egg stage, 83% for the chick stage, and 54% overall. The low nest survival rates at the chick stage in 2000 and 2003 were probably mainly due to Stoats, which we believe regularly kill chicks and sometimes adults at nests. Other likely nest predators, such as Carrion Crow and Fox, are very rare in the glen due to the activities of the two full-time gamekeepers.

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