Translator Disclaimer
1 July 2010 Nest Turnover Rates and List-Frame Decay in Bald Eagles: Implications for the National Monitoring Plan
Bryan D. Watts, Adam E. Duerr
Author Affiliations +

In accordance with federal regulations, the United States Fish and Wildlife Service developed a postdelisting monitoring plan for the bald eagle (Haliaeetus leucocephalus) designed to detect a change in the number of occupied nests on a national scale. The plan employs a dual-frame approach to the survey design where a list frame (list of known nests) and an area frame (set of survey plots) are used in concert to estimate the number of occupied nests in 5-year intervals over a 20-year period. The plan offers no provisions for changes in list-frame integrity, nor does it contemplate the impact of such changes on survey performance. We used a long-term data set to quantify occupancy patterns for nests in Virginia, USA, and evaluated their influence on integrity of the list frame and performance of the proposed dual-frame monitoring approach. The average annual turnover rate for nests was 0.261, resulting in a rapid decay of the list frame. Decay of the list frame leads to a functional collapse of the dual-frame approach, down to the area-frame survey alone, early within the monitoring time horizon. This early decay of the list frame implies that the area-frame coverage needed to maintain the same statistical power as stated in the monitoring plan would have to be increased by a factor of 3 to 5 beyond that recommended in the current plan. Remedies for this deficiency undermine the cost benefit associated with inclusion of the list frame. We examined response of the dual-frame survey to variation in nest turnover rates and population growth rates and defined a state space where time to collapse is beyond the proposed 20-year time horizon. Because, under realistic estimates of turnover rates, the dual-frame approach collapses to the area frame within the proposed monitoring window, we recommend that the costs of list-frame maintenance be included in the procedure to optimize allocation of survey effort.

Bryan D. Watts and Adam E. Duerr "Nest Turnover Rates and List-Frame Decay in Bald Eagles: Implications for the National Monitoring Plan," Journal of Wildlife Management 74(5), 940-944, (1 July 2010).
Published: 1 July 2010

This article is only available to subscribers.
It is not available for individual sale.

Bald Eagle
dual-frame survey
Haliaeetus leucocephalus
monitoring plan
nest turnover
population monitoring
Get copyright permission
Back to Top