Action: Replace nesting substrate following severe weather
Two before-and-after studies from Canada found that common tern Sterna hirundo populations increased at one colony where nesting substrates were replaced, but decreased at a second. Several other interventions were used at both sites, making it difficult to evaluate the effects of substrate replacement.
Many birds require specific substrates to nest on, and if flooding or heavy rains remove these then they may not nest. Replacing the substrate following removal may therefore help a colony to survive. Most studies describing the reconstruction of nesting habitats or the protection of nests from flooding are described in ‘Provide artificial nesting sites’.
Supporting evidence from individual studies
Two before-and-after studies at two common tern Sterna hirundo colonies between 1977-89 in Ontario, Canada (Morris et al. 1992), found the nesting population increased at one colony but decreased at another following a combination of interventions, including the replacement of nesting substrate following flooding. Other interventions included: erecting signs highlighting the presence of nesting birds, vegetation control, preventing gulls Larus spp. from nesting, destroying gull nests and shooting particular ring-billed gulls L. delawarensis that were heavily predating tern eggs. Gulls were only culled at the site with population increase, whilst the authors attribute declines to continued high levels of disturbance, vegetation growth and mammalian predators.