Common Burdock - a Kinglet Killer
On October 9, 2001 while birding
in Brookbanks Ravine near my house in Toronto, another walker told me about the
little birds that were "trapped in thistles." Intrigued, I went to the
spot and saw two dead kinglets hanging in the burs of Common Burdock (Arctium
minus), one a Golden-crowned Kinglet and the other a Ruby-crowned Kinglet.
On October 17, I again checked
the Common Burdock plants in Brookbanks Ravine for trapped birds. Along a 200
meter stretch I found 8 dead kinglets in the burdock burs, most were
Golden-crowned. The birds were spread-winged, spread-tailed, and caught by many
parts of their bodies, including the bill. The more they struggled, the more
they became stuck. I estimated they had died over a period of a few days to
several weeks earlier.
While doing the Hamilton
Naturalists' Club Fall Bird Count in Centennial Park near Van Wagners Beach on
November 2, I found a dead Golden-crowned Kinglet trapped in a patch of burdock.
Again in Brookbanks Ravine on
November 19, I found a freshly dead Golden-crowned Kinglet trapped by the burs
Common Burdock is a plant with
large flat leaves that look like rhubarb. The flowers resemble thistles and when
they die the seeds forma round ball that attaches by its barbed velcro-like
hooks to clothing, dogs, anything it touches. Common Burdock grows 1 - 1.5
meters tall or more. Each stalk is loaded with round balls of seeds surrounded
by hooks. After a walk through a waste or brushy place, the odds are that you
have had these burs clinging to your clothing. Burdock is not a native North
American plant, but was introduced from Europe.
I wondered why there were so
many dead kinglets in this stretch of Brookbanks Ravine. The burdock plants were
close to the creek and the edge of the woods. They were growing close to
goldenrod, asters, wild grape and other fruit and seed-bearing plants.
When the kinglets migrated
through in September and October, they probably gleaned insects from the flowers
and seed heads of goldenrod and other plants and inadvertently became trapped in
the burdock. Because of their small size, many kinglets were unable to escape
and became more stuck as they struggled. On October 19, I noticed House Sparrows
going in and out of the burdock, but did not find any of this species entangled.
Mark Kubitz (1989) reported
finding a Golden-crowned Kinglet trapped in burdock in May 1989. A spring
occurrence is unusual as most birds are trapped in the fall. He located
literature reports that involved the following birds killed by burdock:
Blue-headed Vireo, American Goldfinch, Ruby-throated Hummingbird, Yellow-rumped
Warbler, Common Yellowthroat, Pine Siskin and Black-capped Chickadee.
Brewer (1994) reported finding a
dead Blue-gray Gnatcatcher caught in burdock. Martin McNicoll (1994) updated the
literature review and reported the following being hooked: Magnolia Warbler,
Red-breasted Nuthatch, and a warbler. Even small bats have been killed in this
In Bent (1949), James G. Needham
in 1909 describes finding "scores" of Golden-crowned Kinglets
entangled in the hooks of the ripening heads of burdocks one autumn in a partly
wooded pasture near Lake Forest, Illinois (USA).
Needham wrote, "They were
visible in all directions, scores of them sticking to the tops of the clumps on
the most exposed clusters of heads. The struggle had ended fatally for all that
i saw, and its severity was evidenced by the attitudes of their bodies and the
disheveled condition of their plumage. I examined a number of the burdock heads
to determine that attraction had brought the kinglets within range of the hooks,
and found insect larvae of two species present in considerable abundance. Most
abundant were the seed-eating larvae of an obscure little moth (Metzgeria
tapella), but the larvae of the well-known burdock weevil were also present in
some numbers. Doubtless, it was in attempting to get these larvae that the
kinglets (mostly young birds) were captured."
Small birds like kinglets stand
no chance against burdock, whose seed heads are a mass of barbed hooks. I got a
barbed seed stem in my eye and had to go to an eye specialist to have it
This summer I will be cutting
the large basal leaves of burdock plants before they flower and set burs. I urge
others to remove this deadly [and invasive alien] plant in your area to save the
lives of many small birds.
thank Ron Pittaway for valuable comments and discussions on burdock and birds,
and Ron Tozer for checking references.
Brewer, D. 1994.
Ontario Birds 12(3):115-116.
Kubitz, M. 1989.
Ontario Birds 7(3):112-114.
McNicoll, M. 1994.
Ontario Birds 12(3):117-119.
Reprinted from OFO
NEWS: Newsletter of the Ontario Field Ornithologists, Volume 20, No. 2, June
2002 (and subsequently the Wood Duck (Hamilton Naturalists Club
newsletter, September 2002).