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Re: English Ivy and birds



On Sun, 23 Jan 2000, Reece Mitchell wrote:
> 
> I have several large trees partially covered with what I think is =
> English Ivy. I suppose this is an invasive exotic but it provides =
> nesting and roosting cover for a variety of birds and in winter the =
> berries are taken by at least 5 species including Bluebirds. Can anyone =
> tell me about the pluses and minuses of this vine. Should it be allowed =
> to spread?

*NO* exotic should be allowed to spread! I am studying exotic species for 
my Ph.D., and so have read extensively on the topic. Berries are a 
plant's method of fooling animals into dispersing its seeds. Birds tend 
to be suckers for good berries, regardless of what the plant supplying 
them is doing to the rest of the ecosystem. For instance, Brazilian 
Pepper, one of the greatest threats to the Everglades, is very popular 
among birds, even among occasional Caribbean vagrants. However, it still 
outcompetes wide swaths of native vegetation, and exterminates with it 
the birds, insects, reptiles, amphibians, and other organisms that depend 
on the native plants.

For another example, take the Knapweeds, family Centaurea, the topic of a 
recent discussion on a Lepidoptera listserv. They have beautiful flowers 
that produce abundant nectar and attract loads of adult butterflies. 
However, the very same Knapweeds grow densely and crowd out the native 
plants that the very same butterflies require as food plants for their 
caterpillars. So the butterflies pollinate their own demise!

So don't let a few berries fool you, just because they've fooled the 
birds. Native plants are *ALWAYS* better than exotics. And if you want 
berries in your yard to attract birds, there are many native species 
which will produce fruit and attract birds without the negative side 
effects that many exotics have. I still have an e-mail Will Cook posted a 
couple of years ago listing native plants that were beneficial to birds, 
I will happily repost that or forward it to any interested parties, to 
facilitate the wiping out of exotics and spreading of native species. At 
least two nurseries in the Triangle area specialize in native plants, and 
if you look hard enough in other areas you should find some there also. 
If all else fails, pestering conventional nurseries to stock native 
plants usually works if enough people help out... 

Also, remember that the birds are often landscapers in their own right. 
If you keep feeders going in your yard, especially if you do so 
year-round, the birds will poop out seeds of whatever plants they use as 
berry sources, and landscape your yard they way they want it. This may 
bring in some exotic species, and almost certainly some Poison Ivy (which 
is an important food source for many bird species), but will supply you 
with useful native plants as well.

Meanwhile, back in the yard: finally had a Purple Finch, a nice male, 
show up at my feeders today, in the midst of a flurry of activity. Also 
had the pleasure of three woodpeckers on the same tree, within about 6 
feet of each other: one Downy, one Red-bellied, and one Flicker. And the 
sparrow I mentioned a few days ago, or another much like it, came by 
today; as much as the face and crown suggest Swamp or Lincoln's Sparrow, 
the rest of the body is classic Song Sparrow. Which is probably what the 
entire bird is, just with unusually much gray on the face.

It's been interesting, speaking of sparrows, to watch the ground feeding 
birds after the snowfalls. The White-throated Sparrows have been hugging 
the bushes and brushpile all winter, but since the snow fell they have 
been venturing out into the middle of the yard, where the feeders are. 
And they seem to be doing all the work, digging through the snow to the 
fallen birdseed. Once the White-throats excavate a good feeding pit, then 
the others - Juncos, Cardinals, etc. - move in; but the other species 
show no inclination toward digging through the snow themselves. I guess 
the normal feeding behavior of White-throats, scratching through leaf 
litter, preadapts them for penetrating snow more easily than the other 
ground-feeding birds around here.

Good birding! (and bad exotics!)

Josh



Joshua S. Rose
Duke University
Department of Zoology

jsr6@acpub.duke.edu
http://www.duke.edu/~jsr6/