- May 13, 2011
The earliest, and arguably the most widespread, impact that humans have had on birds is the conversion of habitat into agricultural use. Despite the far-reaching changes that modern intensive agriculture has wrought, many birds are still able to utilize farmlands to meet some of their needs. Waste grain is consumed by wintering waterfowl, orchard fruits are relished by summer songbirds, and cereal crops attract blackbirds, crows, and sparrows. Raptors, like Barn Owl and American Kestrel, can nest successfully on farms when prey abundance is high.
According to the 2007 National Resources Inventory, there are 357 million acres of cropland and 119 million acres of pastureland in the United States. As of April 2013, about 27 million acres were enrolled in the Conservation Reserve Program (CRP), a national program that provides farmers with economic incentives for the restoration of grassland habitat on environmentally sensitive lands with a cropping history. Waterfowl, grassland birds, and game birds continue to rebound in the reestablished habitat of these CRP lands.
The Birds and the Bees
Agricultural lands can support a wide variety of bird species, often forming the matrix for smaller suitable habitat patches 1. However, the fragmentation of habitats disrupts key ecological processes, such as gene flow and natural disturbances 2, and oversimplified systems always affect biodiversity. One of the drivers of habitat simplification is the use of pesticides to reduce insect abundance. The U.S. Fish and Wildlife Service estimates that about 50 pesticides currently in use are known to cause bird die-offs. David Pimentel of Cornell University estimates that about 72 million birds die every year as a direct result of pesticides applied to agricultural lands 3. Let’s not forget that birds were the original pest-management experts, and new research from Costa Rican coffee farms indicate that birds provide ecosystem services valued at US $120-310 ha/year in the form of pest control 4. Birds can help reduce pests, if farms take steps to conserve birds on their property.
Bees are an important provider of ecosystem services, yet they may be even more at risk than birds. A recent study of honey bee pollen detected 35 different pesticides and high fungicide loads in pollen samples from around the U.S. (the average pollen sample had 9 kinds of pesticides in it). No samples were without pesticides, even though most bees collected more pollen from nearby weeds and wildflowers than from crops 5. Exposure to combinations of pesticides can have synergistic effects that are more toxic than exposure to any single pesticide, which puts pollinators at an even greater risk. That is sure to leave a bad taste in your mouth!
Studies have shown that, in intensively farmed lands, generalist species can persist and even become pests, but most specialist bird species decline sharply, even becoming entirely extirpated. Simple agricultural practices can often help reduce the threats faced by birds living on our agricultural lands.
Techniques like conservation buffers, delayed harvest, or nontoxic pest management (among others) can attract high bird densities and provide substantial benefits to birds in intensive agricultural landscapes. From the University of Nebraska Rural Initiative 6, here are ten simple steps farmers can take:
- Managing Farming’s Footprint on Biodiversity ↩
- A mountain in a city- the need to plan the human usage of the Table Mountain National Monument, South Africa ↩
- The Audubon Society Guide to Attracting Birds: creating natural habitats for properties large and small ↩
- Forest bolsters bird abundance, pest control and coffee yield ↩
- Crop pollination exposes honey bees to pesticides which alters their susceptibility to the gut pathogen Nosema ceranae ↩
- Opportunities for rural development through bird friendly farms and agricultural/nature tourism ↩