Factors influencing the admission of urban nesting Herring Gull Larus argentatus into a rehabilitation centre and post release survival in comparison with wild counterparts
Orphaned and traumatised Herring Gull admissions to Mallydams Wood wildlife rehabilitation centre were reviewed to determine factors affecting likelihood of release and post release survival. Admission categories; orphan, inexperienced juvenile, fishing litter and caught & entangled showed the most likelihood of release, whereas, disease, weakness, collision and shot birds showed the least probability of release. Between 1999 and 2010, 2,796 (84.1%, this excludes birds euthanased within 48 hours) birds were ringed and released. Subsequently, 44 rehabilitated Herring Gulls have been found dead, 46 sick and 2,179 colour ring sightings of birds alive reported from over 200 observers in the British Isles and Continental Europe. Mean survival days for adult birds (848.77 days ± 66) were not significantly different than non-adult birds (722.49 days ± 26). Similarly, distance travelled by adult group (58.69Km ± 13.10) and non-adult group (68.46Km ± 3.89) were comparable. Post release survival within admission groups showed better than expected recovery rates for shot adult birds (47%) and inexperienced juveniles (40%). Data sourced from urban nesting wild chicks in the South West and South East was compared to rescued juvenile birds. No significant differences between the two groups were found for dead birds, but sick birds and re-sighting data showed significant differences. In-house rehabilitation protocols currently in place were tested and indicated that procedures to mitigate animal suffering and yet improve the likelihood of release were appropriate, with only minor improvements required in release criteria. The anthropogenic pressures on urban gull populations and national decline in the sub-species; Larus argentatus argenteus could be supplemented through rehabilitated birds. The data suggest that the rehabilitation of Herring Gulls was important from both an animal welfare and population perspective and therefore cost effective
