Adapting Strategies to Maintain Efficiency During a Cull of Yellow-Legged Gulls
Increasing populations of yellow-legged gulls (Larus michahellis) in the Mediterranean have created conflicts with seabird conservation, migrating raptors, and humans. As a mitigation measure, gulls are routinely culled in the region. Previous studies of extended culls show that catch per unit effor...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Utah State University
2017-02-01
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| Series: | Human-Wildlife Interactions |
| Subjects: | |
| Online Access: | https://digitalcommons.usu.edu/hwi/vol10/iss1/11 |
| _version_ | 1811259796300496896 |
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| author | Sugoto Roy Ray Ridley Jeff Sandon John R. Allan Peter S. Robertson Andrew Baxter |
| author_facet | Sugoto Roy Ray Ridley Jeff Sandon John R. Allan Peter S. Robertson Andrew Baxter |
| author_sort | Sugoto Roy |
| collection | DOAJ |
| description | Increasing populations of yellow-legged gulls (Larus michahellis) in the Mediterranean have created conflicts with seabird conservation, migrating raptors, and humans. As a mitigation measure, gulls are routinely culled in the region. Previous studies of extended culls show that catch per unit effort declines over time through a combination of population reductions and avoidance behaviors developing within the remaining population. We countered these problems during a 4-year cull of yellow-legged gulls in Gibraltar by matching the type and mode of deployment of firearms in response to changes in gull distribution and behavior. We found that shotguns were effective when gulls mobbed operators near nesting areas, while rifles were more effective as gulls became wary and retreated farther from the operators. Changing the type of firearm enabled us to counter the expected rate of decline in culling efficiency throughout the project. We were most efficient in the first year of the project, killing gulls at a mean rate of 8.35 birds per man-hour. Although this declined to 4.83 by the third year, the adjustments that we made to the way firearms were deployed raised it to 6.4 in the fourth year despite a 79% decline in the observed total gull population over this period. We modelled the population data collected using a Leslie Matrix to evaluate the impact of management at the end of the culling period. The population declined at a greater rate than explained by the numbers actually culled, suggesting that the cull resulted in an additional disturbance, which triggered emigration at a rate of 35%, over and above the numbers culled. |
| first_indexed | 2024-04-12T18:36:56Z |
| format | Article |
| id | doaj.art-ad2a3e5075704b6ca6d49c91de1cd65d |
| institution | Directory Open Access Journal |
| issn | 2155-3874 2155-3874 |
| language | English |
| last_indexed | 2024-04-12T18:36:56Z |
| publishDate | 2017-02-01 |
| publisher | Utah State University |
| record_format | Article |
| series | Human-Wildlife Interactions |
| spelling | doaj.art-ad2a3e5075704b6ca6d49c91de1cd65d2022-12-22T03:20:54ZengUtah State UniversityHuman-Wildlife Interactions2155-38742155-38742017-02-0110110.26077/kj98-xm17Adapting Strategies to Maintain Efficiency During a Cull of Yellow-Legged GullsSugoto Roy0Ray Ridley1Jeff Sandon2John R. Allan3Peter S. Robertson4Andrew Baxter5National Wildlife Management CentreNational Wildlife Management CentreNational Wildlife Management CentreNational Wildlife Management CentreNational Wildlife Management CentreBirdstrike Management Ltd.Increasing populations of yellow-legged gulls (Larus michahellis) in the Mediterranean have created conflicts with seabird conservation, migrating raptors, and humans. As a mitigation measure, gulls are routinely culled in the region. Previous studies of extended culls show that catch per unit effort declines over time through a combination of population reductions and avoidance behaviors developing within the remaining population. We countered these problems during a 4-year cull of yellow-legged gulls in Gibraltar by matching the type and mode of deployment of firearms in response to changes in gull distribution and behavior. We found that shotguns were effective when gulls mobbed operators near nesting areas, while rifles were more effective as gulls became wary and retreated farther from the operators. Changing the type of firearm enabled us to counter the expected rate of decline in culling efficiency throughout the project. We were most efficient in the first year of the project, killing gulls at a mean rate of 8.35 birds per man-hour. Although this declined to 4.83 by the third year, the adjustments that we made to the way firearms were deployed raised it to 6.4 in the fourth year despite a 79% decline in the observed total gull population over this period. We modelled the population data collected using a Leslie Matrix to evaluate the impact of management at the end of the culling period. The population declined at a greater rate than explained by the numbers actually culled, suggesting that the cull resulted in an additional disturbance, which triggered emigration at a rate of 35%, over and above the numbers culled.https://digitalcommons.usu.edu/hwi/vol10/iss1/11control methodsculldisturbance effectemigrationfirearmsgibraltargullslarus michahellispopulation declineyellow-legged gull |
| spellingShingle | Sugoto Roy Ray Ridley Jeff Sandon John R. Allan Peter S. Robertson Andrew Baxter Adapting Strategies to Maintain Efficiency During a Cull of Yellow-Legged Gulls Human-Wildlife Interactions control methods cull disturbance effect emigration firearms gibraltar gulls larus michahellis population decline yellow-legged gull |
| title | Adapting Strategies to Maintain Efficiency During a Cull of Yellow-Legged Gulls |
| title_full | Adapting Strategies to Maintain Efficiency During a Cull of Yellow-Legged Gulls |
| title_fullStr | Adapting Strategies to Maintain Efficiency During a Cull of Yellow-Legged Gulls |
| title_full_unstemmed | Adapting Strategies to Maintain Efficiency During a Cull of Yellow-Legged Gulls |
| title_short | Adapting Strategies to Maintain Efficiency During a Cull of Yellow-Legged Gulls |
| title_sort | adapting strategies to maintain efficiency during a cull of yellow legged gulls |
| topic | control methods cull disturbance effect emigration firearms gibraltar gulls larus michahellis population decline yellow-legged gull |
| url | https://digitalcommons.usu.edu/hwi/vol10/iss1/11 |
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