Crop-specific effectiveness of birds as agents of pest control

Ecosystem services provided by the natural enemies of agricultural pests can increase crop yield in low intensity agricultural systems. However, these services are highly variable, and trade-offs may exist between harmful and beneficial species. An increasing proportion of New England farms have adopted farming practices that retain extensive native vegetation, and prior research has shown these practices support native bird populations. To determine the pest control services provided by birds on low-intensity New England farms, we compared pest populations and leaf damage on crops where birds were excluded to those where they were not. We found that pest abundance was higher on brassica and cucurbit crops within exclosures than on control plants without exclosures, suggesting the presence of birds reduced pest numbers on these crops. In contrast, pest numbers were lower on solanaceous crops within exclosures, suggesting birds may be consuming other natural enemies of pests on these crops. Leaf damage was also lower where birds were present in all three crop types, though not significantly so in brassica crops. Our results show that growers in can improve natural biological control of brassica and cucurbit crop pests by enhancing bird communities near these crops, while effects may be less predictable in solanaceous crops.