USA: Protecting wild birds on tomato farms

Wild birds & biodiversity

Next time you open a bottle of Ragu tomato sauce, think of the Swainson's Hawk. This threatened species is benefiting from the biodiversity plans of tomato farms in California.

Tomato plants – low and bushy – provide ideal cover for rodents, the hawks' prey. When tomatoes are mechanically harvested the rodents are flushed out, making them easy pickings for the hawks.

Because tomatoes are harvested from July to early October, the long availability of prey helps the Swainson's Hawk build up energy before its winter migration to South America.

Wild bird populations are a useful biodiversity indicator because they are often at the top of the food chain and are relatively easy to monitor. But bird populations are in decline in California because of intensive agriculture and urban development.

To help measure their impact on biodiversity, tomato growers in Yolo County, near Sacramento, California, are monitoring bird numbers with the aid of the Audubon Society, a conservationorganisation.

First year results

Biodiversity is one of Unilever's eleven sustainable agriculture indicators. Guidelines recommend farmers leave green, uncultivated areas in and around fields to encourage wildlife – a practice supported by Yolo County farmers.

Between 2005 and 2006, team members from Unilever's sustainable tomato programme and ecologists from Audubon set up observation posts in 31 test fields, and monitored bird species for a year.

Results show that field edges had the greatest diversity, with 42 different bird species recorded. The Yellow-billed Magpie – on a watch list of at-risk birds – was one of the most abundant. They thrive in field edges, benefiting from the number of different habitats, such as trees, shrubs and hedges.

Unilever and Audubon are using the initial results to develop biodiversity management practices at other tomato farms in California. More studies will be carried out.