Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fragmented forests result in more snakes, fewer birds

05.05.2010
About half of all bird nests don't survive due to predators, particularly in fragmented forest areas, but why? University of Illinois researchers monitored both the prey and predator to find an answer.

"Rat snakes accounted for a high percentage of cases of nest predation," said U of I researcher Patrick Weatherhead. "Our hypothesis was that because snakes spend so much more time on the edges of the forest, that's where bird nests should be most vulnerable. And in fact, we never found that."

He explained that rat snakes, which in eastern North America are the number one predator to nesting birds, go into the forest to feed, then return to the edges to regulate their body temperature, breed, and shed their skin. "Clearly, a lot of the time they are on the edges they're not actively hunting, because nests on the edges were not at greater risk from the snakes than the nests on the interior of the forest."

Weatherhead said this knowledge of habitat preferences of rat snakes is starting to explain why forest fragmentation usually results in increased nest predation for forest birds.

Fragmented forested areas provide more perimeters, which are beneficial to the snakes. "Snakes really like that interface between the open and closed habitat, whether it's an edge where the forest opens onto a wetland or a rock outcrop or a manmade habitat such as a hay field. So, if your priority is to conserve the birds, you'll want to preserve unfragmented forest habitat," Weatherhead said.

Weatherhead said ornithologists have been interested in fragmentation for a long time. "It's not just that you've lost habitat, but the smaller chunks you're left with aren't as good for a variety of wildlife. The smaller fragmented areas attract birds but they don't do very well there. They've been called ecological traps.

Weatherhead says the message is, if you're going to clear land for agriculture or other development, try to avoid breaking the forest into bits and pieces. He concedes that in southern Illinois the land doesn't lend itself to this kind of clearance. "Most of the good agricultural land occurs in the valley bottoms, whereas on the slopes it's too rocky and too steep to make it practical to use for agriculture."

The study, conducted in southern Illinois, used data from radio transmitters implanted in rat snakes combined with information from over 300 bird nests that were located and their fate tracked. Independently, a number of nests that weren't actually a part of the study were monitored with video cameras to document the nest predators. Rat snakes are common in eastern North America from Texas in the west to the Florida Keys in the east and all the way up to southern Ontario.

"Everywhere there have been camera studies, as long as it's in wooded or semi-wooded habitat, rat snakes emerge as the single most important predator. They're common throughout the range, and they're really good at finding bird nests," Weatherhead said.

The miniature video cameras make identification of nest predators possible because they can record activity at the nests around the clock. How do snakes on the ground see nests up in trees?

Weatherhead says the evidence is circumstantial. "Snake predation is much higher on nests where the young are being fed than when the eggs are being incubated. There's a lot more parental activity when the young are being fed than when the eggs are being incubated. The limited evidence available all seems to point to the snakes observing the parents flying back and forth to the same place, an indicator to the snake that there's a nest there. There are anecdotes of people watching a nest and noticing a rat snake watching that same nest, and from the snake's head movements it was obviously tracking the movement of the adult pairs back and forth." In one case, the snake was then observed going to the nest and eating the young.

Rat snakes get their name because they are primarily predators of small mammals. "But rat snakes are very opportunistic," Weatherhead said. "I have a picture of a rat snake eating a full-grown squirrel. So that's a mouthful. They're generalists both in terms of the mammals they eat and in terms of the birds that they prey on. They'll take whatever birds they encounter, and because they're such good climbers, they can get to both low nests and high nests. They can climb just about any kind of tree. They eat bird eggs, fledglings and sometimes they'll even get the mom if she's sitting on the eggs," Weatherhead said.

Animals such as hawks, raccoons, badgers, foxes and coyotes prey on rat snakes.

Linking snake behavior to nest predation in a Midwestern bird community was published in a 2010 issue of Ecological Applications. Gerardo Carfagno, Jinelle Sperry, Jeffrey Brawn, and Scott Robinson contributed to the research.

News writer: Debra Levey Larson
phone: 217-244-2880; email: dlarson@uiuc.edu

Debra Levey Larson | EurekAlert!
Further information:
http://www.illinois.edu

More articles from Ecology, The Environment and Conservation:

nachricht Joint research project on wastewater for reuse examines pond system in Namibia
19.12.2016 | Technische Universität Darmstadt

nachricht Scientists produce a new roadmap for guiding development & conservation in the Amazon
09.12.2016 | Wildlife Conservation Society

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

Im Focus: Newly proposed reference datasets improve weather satellite data quality

UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration

"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Water - as the underlying driver of the Earth’s carbon cycle

17.01.2017 | Earth Sciences

Satellite-based Laser Measurement Technology against Climate Change

17.01.2017 | Machine Engineering

Studying fundamental particles in materials

17.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>