Are bluebirds good for farms, and are farms good for bluebirds?

View the project final report

• 2007 annual report

Commodities

• Agronomic: oats, rye, grass (misc. perennial), hay
• Fruits: berries (strawberries), melons
• Vegetables: beans, broccoli, cabbages, carrots, cucurbits, eggplant, greens (leafy), onions, peas (culinary), peppers
• Additional Plants: trees

Practices

• Animal Production: feed/forage
• Crop Production: windbreaks
• Education and Training: display, extension, on-farm/ranch research
• Farm Business Management: whole farm planning
• Natural Resources/Environment: biodiversity, hedgerows, hedges - woody, indicators, wildlife
• Pest Management: biological control
• Production Systems: agroecosystems, holistic management
• Sustainable Communities: public participation

The work I propose addresses information needs of growers practicing ecological agriculture who wish to support diverse natural predator-prey interactions. I propose a detailed study of the potential predation impact that native birds can have on leaf-chewing pests of organic vegetables. While I will not test the hypothesis that birds can help control insect pests, I propose to obtain information that can be used to estimate quantitative impacts of resident insect-feeding birds on pest numbers in organic vegetables in NC Florida. I also propose to help elucidate how insecticides affect the behavior and reproductive success of farmland songbirds. I will, 1) quantify foraging rates, prey types/numbers taken by individually marked birds of species known to feed on pests in organic vegetable fields (using mist nets to capture the birds and colored leg bands to mark them and intensive foraging observations in fields), and map the activities of foraging birds with respect to field configuration; 2) estimate leaf-chewing pest occurrences in bird-foraging areas utilizing standardized insect-vacuuming and spotting methods applied to 3m diameter sampling plots centered on locations where birds feed on pests and nearby randomly-selected locations; 3) Conduct nest-monitoring and habitat use studies of Eastern Bluebirds on vegetable farms with different levels of insecticide application (up to 150 different pairs, and 450 nests per season). Nest-boxes will be placed in farm fields, near forest edges, in a standardized and replicated fashion. This third objective will help determine: A) how much field area does an adult bird use to forage B) prey-delivery rates to nestlings (by monitoring focal birds at nest boxes), and C) reproductive success in relation to farm management. I will conduct studies in both spring and fall growing seasons and on multiple farms and fields to avoid biases based on grower management practices. This work will allow quantitative estimates of: 1) number of pests taken per bird per unit area / time vs. number of pests present in fields per unit area / time; 2) spatial variation in pest consumption by birds (e.g., foraging time spent at field edge vs. interior and in fields vs. in field borders); 3) temporal variation in the number of prey utilized per unit time per bird, including the rate of consumption of pests by adults vs. dependent nestlings, accounting for seasonal variation associated with breeding and non-breeding activities; 4) reproductive success of birds in farms that use insecticide vs. farms that do not. With seasonal and spatial variation in pest availability, consumption by insectivorous birds, and bird density, I can provide rough parameters to be used in calculating bird impacts on pest prey in organic vegetable fields. My approach will allow detection of any crop damaging activities by birds in fields, as well as seasonal changes in bird composition and density. My work is significant in that it will provide detailed information that growers can use to weigh the relative benefits of practices that foster native insect-eating birds on their farms versus other forms of biodiversity. Growers recognize that birds interact positively with vegetable fields, but my study will make these impressions concrete by providing numerical estimates for assessing management options to enhance bird-predation relative to other biocontrol options. Moreover, it will help illustrate how well birds can reproduce on farms that do not use insecticides (e.g. - organic farms) in comparison to those that do. I will convey my results in clearly written articles and web postings that are accessible to (and frequently used by) sustainable growers.

1) Quantify foraging rates of avian insectivores commonly observed in fields in spring and fall, including a summary of prey types and numbers taken per unit time of foraging, and distribution of foraging time by insectivorous birds with respect to field lay-out.

2) Estimate leaf-chewing pest availability in areas where birds forage in vegetable fields.

3) Conduct nest-monitoring and habitat use studies of Eastern Bluebirds on vegetable farms with different levels of insecticide application.