Little Terns
Sterna albifrons in Japan originally nested on river spits and gravels and along sandy coasts. In recent years, however, these natural breeding habitats have been eliminated or deteriorated, and the remaining terns nest on yet-to-be-utilized landfill in ports and coastal industrial zones. Even these sites, however, will eventually be built on, and thus cannot be counted on as permanent. Given the high coast of coastal land in Japan, setting aside of sufficient ground breeding reserves will be difficult or impossible. In this environment, rooftop breeding sites, which can be provided even in congested areas, may be the most feasible hope for future preservation of this species.
As a first step in design and implementation of rooftop nesting sites in Chiba City, research was conducted on existing rooftop sites in northern Florida, along the Gulf of Mexico coast (Fig. 1). As a result of field observations and analysis of data, the following recommendations were prepared:
1. The rooftop should be covered with light-colored gravel.
2. To prevent chicks falling off, and to provided some protection from the sun, the roof should be edged with a wall at least 20 cm high.
3. A colony at Mihama Ward, Chiba Prefecture, would require at least 500 nests to be large enough for the terns to defend their eggs and chicks against predators. This number of would require a rooftop area of at least 17,000m
2 (17ha).
4. Predator control, especially thinning of the local Jungle Crow
Corvus macrorhynchos, should be considered.
5. The site must be within easy distance of shoals and tidal flats that serve as feeding grounds.
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