ABSTRACT Capsule: A data-thinning approach was used to assess the effects of reducing the frequency of nest-checks on estimates of breeding success of Common Guillemots Uria aalge. Inter-year and inter-colony differences in fledging age and their implications for setting a minimum age after which a chick could be assumed to have fledged were evaluated. Aims: To assess the consequences of reducing sampling frequency on the estimation of breeding success, and on the robustness of the assumption that breeding has been successful if a chick survives to 15 days old. Methods: Breeding success, ages at fledging and loss of chicks were estimated from daily checks at two Scottish colonies over a six-year period. Data-thinning was used to assess the consequences of reducing checks from daily to every two or three days. Breeding success was recalculated assuming that all chicks surviving to 15 days fledged. Results: Reducing the frequency of checks from daily to every second or third day resulted in a small but statistically significant increase in the estimate of success. Between 20% and 25% of chick losses occurred when chicks were ≥15 days old. Assuming that these chicks had fledged resulted in significant increases in breeding success. Conclusion: Assumptions about whether or not a chick fledged had a greater impact on the estimate of breeding success than reducing the frequency of nest-checks from daily to every second or third day. There was no threshold age after which a chick could be assumed to have fledged. These findings are relevant to other monitoring schemes where there is pressure to reduce input. Sampling methods used in monitoring schemes need to be clearly stated and changes in protocols documented so that sampling effects can be incorporated into future analyses.

中文翻译：

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观察者努力对 Common Guillemot Uria aalge 育种成功估计准确性的重要性

摘要胶囊：使用数据细化方法来评估减少巢检查频率对普通海鸠育种成功估计的影响。评估了羽化年龄的年际和群落间差异及其对设定最低年龄的影响，在此之后可以假设小鸡已经羽化。目的：评估降低采样频率对估计繁殖成功率的影响，以及如果雏鸡存活至 15 天大时繁殖成功的假设的稳健性。方法：育种成功率、雏鸟年龄和雏鸡损失是通过六年期间在两个苏格兰殖民地的日常检查来估计的。数据精简用于评估将检查从每天减少到每两三天的后果。假设所有存活至 15 天的雏鸡均已发育成熟，则重新计算繁殖成功率。结果：将检查频率从每天减少到每两天或三天会导致成功估计值出现小幅但具有统计显着性的增加。20% 到 25% 的雏鸡损失发生在雏鸡 ≥ 15 日龄时。假设这些小鸡已经长大，繁殖成功率会显着增加。结论：与将鸟巢检查频率从每天减少到每两天或每三天相比，关于雏鸡是否已成熟的假设对繁殖成功的估计具有更大的影响。没有可以假设小鸡已经长大的阈值年龄。这些发现与其他存在减少投入压力的监测计划相关。