Can't believe anyone would use a metal chain on the tundra to flush nesting birds! Light rope (1/4 " poly, hemp, or similar)works best in that habitat or in grasslands. I've used a "Surveyors Chain" which in the past was made up of metal links but is now often just a rope marked off in chain lengths. Perhaps this is what was referred to in the original post.
Usually two observers drag a 1 - 200' length of rope between them with one or two more, depending on rope length, about 50 feet behind. Slow is best as it gives everyone a chance to pinpoint nest locations, plus ID and count the birds being flushed.
The practice doesn't seem to upset the birds much during nesting. On the tundra it works on nesting shorebirds humans can walk up too & lift off the nest by hand. Birds react as though the rope is a snake or other small predator. It also works outside the breeding season on various sparrows, rails, other skulkers, plus Short-eared Owls.
It can be very confusing when the birds are being driven ahead as you don't know which you've counted & which are new. In any event it is best to end up at a road or other open area to get a final, accurate count as the birds cross it.
I don't remember reading anything about how to do this. I just learned it over several years working with different biologists. Must be something somewhere though. I'll ask a few contacts & see if anything turns up. If so I'll post it here.
Hope young bustards don't freeze on moms distress call as the Killdeer young do here. They will often remain completely still even when the rope drags right over them.
In closing, the above practices are ONLY used during government authorized research surveys and not for everyday birding! Deliberate harrasment or disturbing of birds is illegal here, with substantial fines levied, and in a few extreme cases perpetrators have gotten a free vacation in their local jail.
