Efficacy of decoys and familiar versus unfamiliar playback calls in attracting common terns to a rehabilitated wetland on Lake Ontario

Published source details Pynenburg B.P., Moore D.J. & Quinn J.S. (2017) Efficacy of decoys and familiar versus unfamiliar playback calls in attracting common terns to a rehabilitated wetland on Lake Ontario. Aquatic Ecosystem Health & Management , 20, 285-294.
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Summary

A before-and-after study in 2013–2014 of four artificial islands in Ontario, Canada (Pynenburg et al. 2017) reported that after removing ring-billed gull Larus delwarensi nests, the total number of common tern Sterna hirundo nests recovered – although one island was abandoned. On 10 May 2013, there were 151 tern nests across the four islands. On 13 May, gulls began nesting on three islands and the number of tern nests dropped (to 63 on 15 May). All gull nests were destroyed between 15 and 31 May. On 31 May, there were 273 tern nests across the four islands. One of the islands was abandoned completely after gulls arrived in 2013, and was not used for nesting in 2014 either. In 2013 and 2014, tern and gull nests were surveyed on four recently created/restored small islands (88–207 m²) in a freshwater wetland. The islands were intended as nesting habitat for terns. Gulls encroached on tern territory and killed tern eggs.

Reduce inter-specific competition for nest sites of ground nesting seabirds by removing competitor species

A before-and-after study in 2013–2014 of four artificial islands in Ontario, Canada (Pynenburg et al. 2017) reported that after removing ring-billed gull Larus delwarensi nests, the total number of common tern Sterna hirundo nests recovered – although one island was abandoned. On 10 May 2013, there were 151 tern nests across the four islands. On 13 May, gulls began nesting on three islands and the number of tern nests dropped to 63 on 15 May. All gull nests were destroyed between 15 and 31 May. On 31 May, there were 273 tern nests across the four islands. One of the islands was abandoned completely after gulls arrived in 2013, and was not used for nesting in 2014 either. In 2013 and 2014, tern and gull nests were surveyed on four recently created/restored small islands (88–207 m²) in a freshwater wetland. The islands were intended as nesting habitat for terns. Gulls encroached on tern territory and killed tern eggs.

Provide artificial nesting sites for ground and tree-nesting seabirds

A replicated study in 2010–2014 in Ontario, Canada (Pynenburg et al. 2017) reported that four artificial islands were colonized by common terns Sterna hirundo. Within a few days of completion (late April 2013), terns were observed landing and courting on all four islands. On 10 May, there were 151 tern nests. However, on 13 May, ring-billed gulls Larus delwarensi also began nesting on three islands. On 15 May, there were only 63 tern nests left. One island was abandoned completely. Terns bred on three of the four islands in 2014, producing a total of 604 nests. Between 2010 and 2013, three artificial islands (88–93 m²) were created and one artificial island (207 m²) was restored in Windermere Basin, to provide common tern nesting habitat. The islands were topped with a mix of sand and gravel. During construction (until late April 2013), captive birds of prey were perched or flown on the islands to discourage nesting. Afterwards, common tern decoys were installed and calls were played to encourage nesting on three islands. Decoys and calls were not used in 2014. Birds were initially observed from the mainland, but regular nest surveys were carried out once nesting began.