Raptor usurpers in neighboring habitats reshape the conventional wisdom

Aug 03, 2011
This is Guilad Friedemann of Tel Aviv University with a short-toed eagle in the Judean Foothills. Credit: AFTAU

When we make plans that will change a natural environment — whether it's building a new shopping mall or planting a new forest — surveyors dutifully assess the environmental risks to plant and animal life in the region. But what's environmentally good for one area may be an environmental disaster for an adjacent one, a Tel Aviv University researcher cautions.

When displaced by these projects, indigenous species migrate to neighboring habitats, says Guilad Friedemann, a PhD student at TAU's Department of Zoology in the George S. Wise Faculty of Life Sciences. This has a significant impact on the species and resources that were already there. With a new species moving in and demanding its share of existing space and food, competition becomes fierce.

Based on a study of two raptor species in the Judean Foothills, the long-legged buzzard and the short-toed eagle, Friedemann has determined that human interference in natural habitats has a reach beyond the specific region under assessment. Pursued under the supervision of TAU's Prof. Yossi Leshem and Prof. Ido Izhaki from the University of Haifa, and in collaboration with the KKL-JNF, Smolar – Vinnikov Foundation, NPA and Kfar Etzion Field School, this ongoing research has been published in the journal Biological Conservation.

A turf war revealed by GPS

When a species is forced from its habitat, it has to go somewhere — and that has an effect on neighboring environments. The long-legged buzzard had always made its home in the open spaces of the Judean Mountains, explains Friedemann, using the mountain cliffs for nesting and hunting. But because environmentalists have been planting a new forest in the area in a process known as "afforestation," the buzzard needed to migrate elsewhere. They now make their nests in the trees of the Judean Foothills, threatening the nesting ground and food source of the short-toed eagle, its established inhabitants.

Through extensive field research, including the placement of advanced GPS systems on the adult nesting birds, Friedemann and his fellow researchers tracked the movements of both species throughout breeding season by tagging four buzzards and three eagles. They found 31 buzzard nests and 60 eagle nests in the Judean Foothills. The researchers continue to examine each nest twice a season, tracking the growth of new chicks and analyzing food remains to determine the extent of competition for food sources between the two species.

The results, say Friedemann, will indicate that the buzzards have started to muscle in on the eagles' habitat — taking over their nests and diminishing the common food supply of snakes, lizards and rodents. "Every time you have strong competition between two species, one is more successful," he explains. "There is a negative impact on the weaker species."

The next step, says Friedemann, is to extend research done with the GPS transmitters, and to assess the rising levels of aggression in both buzzards and eagles, which arise from the heightened competition for food and space. By playing recorded bird calls near nesting sites of the opposite species, the researchers can measure how aggressive the response becomes.

Living side-by-side

In this case, afforestation, usually considered a positive contribution to the sustainability of our environment, was the cause of habitat destruction. This should serve as a cautionary lesson for any project that serves to alter the natural environment, the researchers conclude.

"There needs to be a broader consideration not just of the directly affected area, but of neighboring areas as well — especially if there is a species that will be forced to abandon the original area and seek out a new place to live," Friedemann says. In this instance, harm might have been avoided by setting aside a track of open space where the buzzards could continue to nest and hunt, a conclusion that would have broad implications for landscape planning and policy.

We must take more responsibility for the assessment of neighboring habitats, Friedemann cautions, because what helps one environment might harm the next.

Explore further: A European bear's point of view, finally on film

add to favorites email to friend print save as pdf

Related Stories

Indiana bald eagle recovery huge success

Jun 20, 2006

Indiana environmental experts say the Hoosier State is now home to 200 of the nation's bald eagles, just 21 years after they were considered nearly extinct.

New eagle crowding nesting eagle pair

Feb 18, 2008

A pair of bald eagles nesting in Virginia's Norfolk Botanical Garden are used to being visited by people, but now must deal with an interloping female eagle.

How seabirds share their habitat

Jan 05, 2011

When different species of seabirds share a habitat with limited sources of food, they must differ in their feeding habits. This specialization is known by biologists as an "ecological niche". Researchers at ...

Why solitary reptiles lay eggs in communal nests

Sep 03, 2009

Reptiles are not known to be the most social of creatures. But when it comes to laying eggs, female reptiles can be remarkably communal, often laying their eggs in the nests of other females. New research in the September ...

Recommended for you

Sharks contain more pollutants than polar bears

20 hours ago

The polar bear is known for having alarmingly high concentrations of PCB and other pollutants. But researchers have discovered that Greenland sharks store even more of these contaminants in their bodies.

Moth study suggests hidden climate change impacts

Apr 15, 2014

A 32-year study of subarctic forest moths in Finnish Lapland suggests that scientists may be underestimating the impacts of climate change on animals and plants because much of the harm is hidden from view.

User comments : 0

More news stories

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Wireless industry makes anti-theft commitment

A trade group for wireless providers said Tuesday that the biggest mobile device manufacturers and carriers will soon put anti-theft tools on the gadgets to try to deter rampant smartphone theft.