String can cause Problems

BY GARY SCHNEIDER .

In the July—August issue of the Island Naturalist I asked if anyone had any information on birds getting trapped in the string used by silvi— culture contractors, forestry technicians and treeplanting assessors to measure areas. A contractor that I work with had told me that he had found several dead birds trapped in the string in 1986, and I wanted to see if it was a common occurence. One response that I received was totally unthought of — a woman riding next to a clearcut area said that her horse got its legs caught up in the string and started to balk. Luckily the horse was easy to calm down.

Another response came from Martin K. McNicholl of the Long Point Bird Observatory on Lake Erie. He sent the following article by J. Derek John- son, Editor of the Alberta Naturalist, entitled "An Unintentional Bird Snare":

The research project I am currently involved in with the Canadian Forestry Service is a study of the potential of drainage to improve tree growth on certain peatlands in Alberta. One of our three study sites is a treed fen located along a tributary of Wolf Creek, 16 km south of Highway 16, along the Wolf Lake Road, southeast of Edson.

In our work we have occasion to make considerable use of a thread land measurer, known as a "Topofil chaix." The apparatus uses a lightweight but strong white polyester thread. We have used it to measure distances between points as well as to mark the boundaries of our sample plots. After use the thread is usually severed from the measurer and left on the ground.

Unbeknown to us our work was creating a death trap for some of the local avifauna. During the field season of 1985 we encountered birds en- tangled in the thread on three separate occasions. One was a Black—capped Chickadee; another was a Gray Jay. Both were mature birds and both were found dead. The third appeared to be an immature Northern Flicker and it was found alive. This bird was successfully untangled and released, how- ever, we do not know if it survived. All the birds had caught the thread with either a leg or a wing and in their struggles to free themselves had only succeeded in entangling themselves more.

We were surprised that our work would be a hazard to the local wildlife in this way, but once we realized there was a problem we were much more careful when using the thread, wither rolling as much of it up as we could after use and disposing of it, or if it had to remain in place, making sure it was as close to the ground as possible. During the 1986 field season no casualties were encountered, despite an even greater use of the thread to mark plot boundaries.

At our other two study sites, Goose River southeast of Valleyview, and Kimiwan Lake north of McLennan, we have not encountered any entrapped birds. Whether or not this is due to habitat differences and hence differences in the local avifauna, or just blind luck, we do not know.

As a final comment, personal observation has V - shown the thread to be totally ineffective in restraining moose." (Spring 87)

On Prince Edward Island, as in Alberta, awareness of a potential pro— blem can go a long ways towards solving it. Using the thread as little as possible, leaving less on site and perhaps using a cotton thread that woul break down more rapidly would all be a help. Thanks again to Martin for the information. The Alberta Naturalist is available through the Northern Forest- ry Centre, 5320-122 St., Edmonton, Alberta T6H 355. '

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