DOES INVESTIGATOR DISTURBANCE NEGATIVELY IMPACT PRODUCTIVITY? AN EXPERIMENTAL STUDY IN BREEDING RING-BILLED GULLS (LARUS DELAWARENSIS)

Open Access
Author:
Kemfort, Tara Lynn
Area of Honors:
Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Dr Jennifer Arnold, Thesis Supervisor
  • Jennifer Marie Arnold, Thesis Supervisor
  • Sandy Feinstein, Honors Advisor
Keywords:
  • investigator disturbance
  • ring-billed gulls
  • mark-recapture
  • waterbirds
Abstract:
Understanding responses of waterbirds to investigator disturbance is essential for minimizing any adverse effects of research while maximizing data collection to inform management decisions. It has been suggested that while some behavioral effects may be observed, disturbance is only likely to be problematic if it alters survival or productivity, and habituation may minimize negative effects by increasing tolerance. In 2008, we undertook an experimental study of the effects of disturbance from monitoring activities on the survival of ring-billed gull (Larus delawarensis) chicks at a large, undisturbed colony in Lake Ontario. Throughout the chick-rearing period, we banded and recaptured chicks in six, approximately 40 m2 fenced plots, each containing 21-25 nests. To separate potential disturbance effects from differences in data quality, plots were grouped into three areas that differed in intensity of investigator disturbance (visits near-daily, every six days, and once every two weeks) but not all plots were monitored on every visit. Survival was analyzed in a live-dead, multistate mark-recapture model that allowed us to focus only on prefledging survival and include dead recoveries. As plots differed in their monitoring frequency, we repeated the analyses three times using data subsampled from plots. Data quality (recapture probability) was much higher for nests checked near-daily but we found no evidence that this level of monitoring negatively impacted chick survival and nest productivity. We also found no difference in data quality between plots monitored every six days and those checked every two weeks. Our results indicate that ring-billed gulls at this site readily habituate to near-daily monitoring protocols with no adverse impacts on chick survival and that these protocols offer the best trade-off between investigator disturbance and data quality.