Nav: Home

How does agriculture affect vulnerable insect-eating birds?

August 29, 2018

Aerial insectivores--birds that hunt for insect prey on the wing--are declining across North America as agricultural intensification leads to diminishing insect abundance and diversity in many areas. A new study from The Condor: Ornithological Applications looks at how Tree Swallows' diets are affected by agriculture and finds that while birds living in cropland can still find their preferred prey, they may be working harder to get it.

The University of Saskatchewan's Chantel Michelson, Robert Clark, and Christy Morrissey monitored Tree Swallow nest boxes at agricultural and grassland sites in 2012 and 2013, collecting blood samples from the birds to determine what they were eating via isotope ratios in their tissues. Tree Swallows usually prefer aquatic insects, which they capture in the air after they emerge from wetlands to complete their life cycles. The researchers suspected that birds living in crop-dominated areas would be forced to shift to eating more terrestrial insects, due to the effects of insecticide use and other agricultural practices on wetland habitat.

Instead, they found that swallows were eating more aquatic than terrestrial insects at all sites, and in 2012 it was actually the grassland birds whose diet contained a higher proportion of terrestrial insects. The results suggest that wetland habitat may provide a buffer against the negative effects of agriculture. However, birds living in cropland weighed less on average than their grassland-dwelling counterparts--a sign that they may be struggling.

"We set up this study to see if insectivorous swallows would be disadvantaged in agricultural croplands by shifting their normally aquatic diet to terrestrial insects to compensate for lower food availability. We were surprised that the birds did not generally do this," says Morrissey. "Adult swallows in particular were heavily reliant on aquatic prey regardless of land use type. At the grassland dominated site, in fact, they fed their nestlings a wider variety of prey from both aquatic and terrestrial origin. Diet did not seem to influence body condition, but birds in cropland sites were lighter on average which may signal they are working harder in croplands to obtain their preferred aquatic prey. This work shows how important wetlands are for maintaining birds in agricultural landscapes and these are important reservoirs for conserving biodiversity in an otherwise heavily altered landscape."

"Grasslands are one of the most imperiled ecosystems on the planet because their rich soils are ideal for agriculture. Pesticides and fertilizers are applied in ever-increasing quantities, which has serious implications for organisms that live there," adds Acadia University's Dave Shutler, an expert on Tree Swallow ecology who was not involved with the study. "This study compared the diets of Tree Swallows in natural grasslands and croplands, each of which had roughly similar wetland densities. Although diet composition was similar in both areas, it appears that diet quality was better in the natural grasslands, because birds there were heavier and in better condition than those in the cropland."
-end-
"Agricultural land cover does not affect diet of Tree Swallows in wetland dominated habitats" will be available August 29, 2018, at http://www.bioone.org/doi/full/10.1650/CONDOR-18-16.1 (issue URL http://www.bioone.org/toc/cond/120/4).

About the journal:The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology, published by the American Ornithological Society. For the past two years, The Condor has had the number one impact factor among 27 ornithology journals.

American Ornithological Society Publications Office

Related Diet Articles:

Poor diet can lead to blindness
An extreme case of 'fussy' or 'picky' eating caused a young patient's blindness, according to a new case report published today [2 Sep 2019] in Annals of Internal Medicine.
New research on diet and supplements during pregnancy and beyond
The foods and nutrients a woman consumes while pregnant have important health implications for her and her baby.
Special issue: Diet and Health
Diet has major effects on human health. In this special issue of Science, 'Diet and Health,' four Reviews explore the connections between what we eat and our well-being, as well as the continuing controversies in this space.
Should you eat a low-gluten diet?
When healthy people eat a low-gluten and fiber-rich diet compared with a high-gluten diet they experience less intestinal discomfort including less bloating which researchers at University of Copenhagen show are due to changes of the composition and function of gut bacteria.
If your diet fails, try again; your heart will thank you
Risk factors for cardiovascular disease closely track with changes in eating patterns, even only after a month or so.
The brain diet
Scientists at the Medical University of South Carolina (MUSC) find that high levels of a hormone called FGF23 are linked to changes in brain structure.
You are never too old for the Mediterranean diet
The Mediterranean diet as a secret of long life for elderly.
Getting to the roots of our ancient cousin's diet
Since the discovery of the fossil remains of Australopithecus africanus from Taung nearly a century ago, and subsequent discoveries of Paranthropus robustus, there have been disagreements about the diets of these two South African hominin species.
A diverse diet may not be the healthiest one
Scientific evidence to date does not support the notion that eating a diverse diet is healthy or promotes a healthy weight.
How was Mediterranean diet associated with severity of psoriasis?
Adherence to a Mediterranean diet, an eating plan filled with fruits and vegetables, legumes, cereals, bread, fish, fruit, nuts and extra-virgin olive oil, may be associated with the severity of the skin condition psoriasis.
More Diet News and Diet Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#541 Wayfinding
These days when we want to know where we are or how to get where we want to go, most of us will pull out a smart phone with a built-in GPS and map app. Some of us old timers might still use an old school paper map from time to time. But we didn't always used to lean so heavily on maps and technology, and in some remote places of the world some people still navigate and wayfind their way without the aid of these tools... and in some cases do better without them. This week, host Rachelle Saunders...
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.