Invasive plants, good for native birds?

From Discovery News:

Birds Loving Honeysuckle Invaders

Analysis by Tim Wall

Mon Feb 14, 2011 03:15 PM ET

The reputation of one invasive species is getting a public image overhaul this Valentine’s Day. From backyard gardens to city rooftops now is the time to embrace your non-native honeysuckle.

Scientists at Penn State University found evidence that bird populations are both more numerous and more diverse if honeysuckle invaders have sweetened the air. The findings champion the need to embrace this invasive species rather than weed it out of sight.

“Among conservation biologists, ecologists, and managers, the default approach is to try to eliminate and root out non-native, invasive shrubs — anything that seems to change an ecosystem,” said biologist Tomás Carlo of Penn State University and co-author of the study, in a press release.

“The problem is that most native communities already have been changed beyond recognition by humans, and many native species are now rare,” Carlo said.

No Away Team Advantage for Invasives

Because of the long history some invasive species have in their new homes, the ecosystems may have adapted to the presence of the newcomers. Some species may have even become dependent on the invasive plants.

Carlo and co-author Jason Gleditsch, a biology graduate student at Penn State wanted to know: “Are we sometimes doing more harm than good when we eradicate plants that, despite being introduced recently, have formed positive relationships with native animals?”

Invasive honeysuckle is very common in a region of Pennsylvania known as Happy Valley. Carlo and Gleditsch studied the number and diversity of birds in Happy Valley and compared those numbers to areas with lower amounts of honeysuckle.

The researchers found that the amount of honeysuckle present predicted the number and diversity of birds.

“The abundance of fruit-eating birds in the Happy Valley region is linked to the abundance of honeysuckle,” said Carlo. “Honeysuckle comprises more than half of all the fruits available in the landscape, and it benefits birds by providing them with a source of food in the fall.”

The birds and the honeysuckle had a, “you scratch my back, I’ll scratch yours” deal. The birds got more food, while the honeysuckle’s seeds were distributed by the birds. In nature, that’s called mutualism.

Pennsylvania now has three to four times more birds, such as robins [see also here] and catbirds, than it did 30 years ago, especially in areas with a strong human presence, Carlo said. Some of this increase may well be explained by the introduction of fruit-producing non-native plants, like honeysuckle.

Biofuel Grasslands For the Birds

“Invasive species could fill niches in degraded ecosystems and help restore native biodiversity in an inexpensive and self-organized way that requires little or no human intervention,” Carlo said.

The benefits weren’t just for the birds. The fruit-bearing American nightshade showed signs of benefiting from honeysuckle neighbors, too.

To measure the effects of growing near honeysuckle, the researchers first grew American nightshade in pots in a greenhouse. They let the nightshade’s fruit’s ripen, then placed then in areas with honeysuckle and in other areas with no honeysuckle but with other fruiting plants, both native and introduced.

The nightshade growing near the honeysuckle had 30 percent more of it’s fruit eaten and seeds dispersed.

“The newly introduced plants piggybacked on the success of the honeysuckle, which is a common phenomenon because fruit-eating birds usually feed on a variety of fruit, whatever happens to be available to them,” Carlo said.

“The same birds that ate the honeysuckle also ate the American nightshade, dispersing the seeds of both plants. It’s a win-win-win for all three: the birds, the honeysuckle, and the nightshades,” Carlo said.

After observing the benefits that non-native species can have on an ecosystem, eradicating them without considering the consequences could be a serious mistake.

“Nature is in a constant state of flux, always shifting and readjusting as new relationships form between species, and not all of these relationships are bad just because they are novel or created by humans,” Carlo said.

“We need to be more careful about shooting first and asking questions later, assuming that introduced species are inherently harmful. We should be asking: Are we responding to real threats to nature or to our cultural perception and scientific bias?” Carlo said.

The research will be published in the journal Diversity and Distributions.

See also here.

MORE than half of the world’s most invasive plant species spread into new habitats from botanic gardens, an analysis of historic “alien” escapes has concluded. Although most cases analysed happened between the 1800s and the mid-1900s, there are reports of more recent releases which merit a tightening up of biosecurity, researchers warn: here.

Sick cows in Europe may help grassland birds in North America, a paper published today in the Proceedings of the National Academy of Sciences suggests. Read more: What kills cows, saves birds – The Scientist – Magazine of the Life Sciences: here.

Much like an anti-hate campaign, a group of 19 ecologists is calling for its colleagues to be less biased. Less biased toward invasive species: here.

March 2011: Cats have been found to be the main predator of birds in a new study that tracked the early lives of gray catbirds in three suburbs of Washington DC: here.

The Pawpaw turns out to be an interesting plant that’s found in most of the Eastern US: here.

Anthropogenic Activities Influence Invasion By Exotic Plant Species: here.

A weed that has invaded over 1.5 million hectares of agricultural land in Cuba can be converted into activated carbon, the University of Strathclyde reported on Tuesday. It said that research led by engineering faculty Professor Peter Hall has found that marabu – a type of hard wood shrub – can be used to produce highly valuable activated carbon: here.

2 thoughts on “Invasive plants, good for native birds?

  1. Pingback: Scottish city wildlife | Dear Kitty. Some blog

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