Ship rats are the biggest barrier to bringing tui back into the city, this week’s Environment Waikato Environment Committee meeting heard.
While city residents, rural landowners, lobby groups and Hamilton City Council had actively planted tui food trees, with 70 percent of chicks or eggs eaten by predators, the tui population was likely to be limited by predators, not food supply.
Landcare Research scientist John Innes, who is overseeing a study to learn more about the abundance, movement and diet of tui in the central Waikato, told the Committee that he hoped the project would result in planting and pest management strategies that would increase the birds’ presence in the city and countryside.
Landcare Research had been researching distribution and dispersal of tui, kereru and bellbird in the Hamilton basin since 2001, with help from an Environment Waikato grant and staff support.
While tui occurred in all large native forests around the Waikato, nesting there over the summer, they were rare summer visitors to Waikato towns and more distant areas. In winter-spring they habitually took journeys to alternative food sources on farms and residential properties, he said.
They fed on the nectar of banksias, kowhai, flowering cherries, camellia, eucalypts, flax, bottlebrush, kahikatea, tree lucerne and red hot poker.
In October last year small radio transmitters were put on 25 tui in urban areas to see where they went to breed and most flew 7 – 16 km back to nearest native forests. One pair attempted nesting in the Taitua Arboretum near Hamilton.
Nests were hard to find and only three of 11 monitored attempts successfully fledged any young. Predators, including ship rats, possum and harrier hawks ended most attempts, some of which were caught on video. Predators preyed on nesting females and there was nowhere that was immune to predators.
Controlling ship rats and possums during September to February each year in nearest native forest nesting areas would quickly increase the number of tui visiting urban areas, he said. Environment Waikato had the primary role to increase numbers this way, perhaps co-operatively with landowners or other parties.
Tui numbers could be increased conspicuously in the next three to five years, he said.
Cr Lois Livingston said there needed to be a huge education campaign about the threat from ship rats, which people did not realise were such as large a problem as possums.