Ring Ouzel Study Group

Glen Clunie Ring Ouzel Breeding Ecology Project

Summary of Results 1998-2004

Part 4

Estimating the extent of second breeding attempts

Our sample sizes of individually colour-ringed adults were insufficient to accurately measure the extent of second breeding attempts in a season on an annual basis. However, an annual estimate was made by calculating the ratio of territories occupied during the late season, to those occupied during the early season (Fig. 6). This suggests that about 70% of pairs make at least two breeding attempts in most years, which is reasonably close to the average 65% of colour-ringed females recorded making two breeding attempts during 1999-2004.

Number of young fledged per pair

To estimate overall breeding success in terms of the number of young fledged per pair, we used the following formula: mean nest survival rate x mean brood size at fledging x ratio of late:early occupied territories. Figures varied from 2.4 in 2000 to 4.5 in 2003 (Fig. 7).

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