Hummingbird 'Tag' Suggests Fragmentation May Be Part Of Pollination Crisis

In the tropical forests of Costa Rica, this green hermit hummingbird, which is an important pollinator of some forest plants, in essence refused to visit isolated sites and traveled only in narrow corridors of the remaining forest – even if that meant taking the roundabout way back home.

This supports the theory that fragmentation and disturbance of landscapes may indeed be a significant contributor to pollination problems that are plaguing plants around the world, researchers say.

The findings will be published soon in Biology Letters, a professional journal.

“It’s been widely observed in many studies that we’re seeing a global decline in both pollinators and plant diversity, to the point that many ecologists are calling it a crisis,” said Matthew Betts, an OSU assistant professor of forest ecosystems and society. “It’s less clear exactly what is causing this. But it’s a serious concern, since 70-80 percent of all plants are pollinated by animals.”

Most of those pollinators, the researchers said, are insects – but it’s not practical to put electronic trackers on the back of a bee. So the OSU scientists moved up to a slightly larger pollinator that was just barely big enough to handle a transmitter – a hummingbird. With recent advances in the miniaturization of tracking devices and a little non-toxic eyelash glue on the bird’s lower back, they were able to attach an electronic tracker for about two weeks to green hermit hummingbirds that live in tropical forests.

“These birds fly very quickly and in theory they could move easily through open spaces,” said Adam Hadley, a doctoral student at OSU. “But we found that they chose to stick closely to areas with forest cover and take the long route back home, possibly to stay close to food or in fear of predation.”

The birds would move along corridors that connected larger patches of forest, the research found, but would not go through open areas to visit isolated fragments. With no pollination of their plants, the researchers said, it’s likely that plant diversity in these separated fragments will ultimately decline. The study supports the importance of remnant forest strips and riparian buffers that connect separated forest fragments in heavily managed landscapes.

What was observed in this case with a bird in a tropical setting, the scientists said, cannot immediately be extrapolated to what insects or other pollinators would do in a temperate zone.

“This does not prove what other animal pollinators would do in similar circumstances,” Betts said. “However, most animals need or prefer a connectivity of the resources they depend on. This does support the concept that landscape fragmentation is restricting the movement of pollinators, and that may be a part of our pollination problem.

“If we get to the point where almost all patches of forests are fragmented, it’s possible that could completely disrupt forest plant ecosystems,” he said.