Duck harvest and crippling in Illinois in 2018-19

Crippling loss (waterfowl downed, but not retrieved) is a recognized component of waterfowl harvest, but there are few contemporary estimates. We used a zero-inflated negative binomial model to account for false reporting of zeros and estimated true waterfowl crippling losses from harvest data reported in a 2018–19 survey of waterfowl hunters in Illinois, USA. We found that crippling rates declined rapidly with increasing harvest and moderately with increasing days afield. For the most active hunters (days afield), the probability of falsely reporting zero crippling loss increased with the number of ducks they reported harvesting, whereas for the least active hunters we found the reverse. We suggest that modest improvements in hunter skill could produce significant reductions in crippling loss.Funding provided by: Federal Aid in Wildlife Restoration*Crossref Funder Registry ID: Award Number: W-112-R-28We collected waterfowl harvest data for the 2018 – 2019 Illinois waterfowl season via a repeat-mail survey. We drew a sample of 5,000 randomly selected Illinois waterfowl hunters from purchasers of the Illinois State Waterfowl Permit during the 2017–2018 waterfowl season (including both resident and non-resident hunters). In 2019, each participant was mailed an 8-page questionnaire with a prepaid return envelope and cover letter explaining the purpose of the survey (henceforth referred to as survey packet). Participants were mailed a reminder/thank you postcard 14 days after the initial survey packet with a second survey packet sent to non-respondents 14 days later. Participants were sent a second reminder postcard after 14 days, followed by a final survey packet to remaining non-respondents 14 days later. We extracted questions of relevance for our study from the full survey including data on the number of ducks harvested per hunter (excluding teal [e.g., Spatula discors] harvested during the September special teal season), how many ducks they downed but were unable to retrieve (crippled), days hunted, age, age first hunted waterfowl, and whether they used decoys. The percent crippled was calculated based on the total number of ducks hit (total duck harvested + total ducks downed but not retrieved). We treated age minus age respondents first hunted waterfowl as a measure of experience and assumed that hunters hunted most years from the age that they first started but recognize that there are limitations to this approach. We excluded respondents who reported not hunting waterfowl from analysis