Using beached bird monitoring data for seabird damage assessment: the importance of search interval

SUMMARY FORD, R.G. 2006. Using beached bird monitoring data for seabird damage assessment: the importance of search interval. Marine Ornithology 34: 91–98. An important rationale for beached bird monitoring programs is that they provide data that are useful in assessing oil spill injuries to seabirds. A common application of these data has been to help measure the extent to which background carcass deposition rates are elevated by an oil spill incident. Ideally, monitoring data can be used to establish a baseline of carcass deposition which, when subtracted from the deposition rate observed during a spill response, provides an estimate of the number of bird recoveries attributable to the oil spill. However, beach monitoring surveys are generally much less frequent than oil spill response surveys, resulting in much higher estimates of the deposition rate per survey. The usefulness of beach monitoring data in oil spill damage assessment could be increased by making the search protocols of monitoring programs and oil spill response agencies more directly comparable. Such standardization would entail conducting some searches at closely spaced intervals. More frequent visits to the same beach would also make possible the estimation of carcass persistence rates and searcher efficiency rates, which would be useful for both oil spill damage assessment and interpretation of beached bird monitoring data.