The Economic Value of Viewing Migratory Shorebirds on the Delaware Bay: An Application of the Single Site Travel Cost Model Using On-Site Data

Abstract

We estimated a count data model of recreation demand using data from an on-site survey of recreational birders who had visited southern Delaware during the month-long annual horseshoe crab/shorebird spring migration in 2008. We analyzed daytrips only. Our estimates from the models ranged from $32 to $142/trip/household or about $131 to $582/season/household (2008$). The variation was due to differences in the value of time. The average household size was 1.66. We found that the valuation results were sensitive to the inclusion of covariates in the model. Our results are useful for damage assessments and benefit–cost analyses where birdwatching is affected.

Keywords:

• recreational birding
• economic value
• shorebird migration
• onsite sampling
• endogenous stratification

Acknowledgments

We thank Delaware State Wildlife Biologist Kevin Kalasz, Dawn Webb, and other Delaware Division of Fish and Wildlife staff as well as the Delaware Ornithological Society for their assistance with survey development and implementation. Andy Krueger, Meredith Blaydes-Lilley, Jon Lilley, Ami Kang, and Kate Semmens provided invaluable assistance with survey administration in the field, and Michael Hidrue helped with some last minutes glitches in model estimation. This study was made possible with funding from NOAA Sea Grant and Dupont Clear into the Future.

Notes

1. See http://www.ceoe.udel.edu/horseshoecrab/Shorebird/index.html for more on the horseshoe crab/shorebird migration.

2. We chose to focus on daytrips to avoid the complications of multiple-purpose trips, calculation of overnight expenses, and endogenous on-site time (different number of days by different respondents).

3. The numbers reported here vary somewhat from those reported in Table 3 because they pertain to the entire day and overnight trip sample. Table 3 pertains to the observations used in estimation.

4. This is the NB2 version of the Negative Binomial (see Cameron and Trivedi, 1998, p. 70). We used STATA code from Hilbe and Martínez-Espiñeira (2005) to estimate our model.

5. Our estimate of travel cost includes gas plus half of the AAA depreciation costs. These are incremental costs associated with the trip. Our use of half of the depreciation costs is arbitrary but using the full depreciation would be in error since some is due simply to aging. Our data are from http://www.aaaexchange.com/Assets/Files/20084141552360.DrivingCosts2008.pdf

6. See Englin and Shonkwiler (1995, p. 109) for compensating and equivalent variation measures.

7. We also estimated our model in Poisson form and considered versions of both Poisson and Negative Binomial that ignored truncation and on-site sampling and that accounted for truncation but ignored on-site sampling. Since our reported model clearly dominates all of these, they were not included here.

8. Average household size was 1.66 in our sample.