The Wild Side: Surveying wildlife populations
We have some wildlife population survey work going on now, and even more to begin in the coming weeks. Right now, we are conducting our annual roadside bear survey. We place 50 baits a half-mile apart, wait a week and return to see how many were taken by bears. We are also conducting our 10-week brood observation survey. DNR employees are asked to record how many broods, or family groups, of ruffed grouse, pheasant and turkeys they see while travelling about. We are supposed to count how many young birds (poults) we see and estimate how many weeks old they are. While setting up our bear survey last week, we saw one grouse that was still sitting on a nest of eggs. Hopefully, when we return next week, we will see that she has successfully hatched her young. This is a roadside observation survey, and is used as an indicator to help us determine whether we have more or fewer birds than the year or years before.
Mourning doves are also the subject of a population survey in Wisconsin. It’s a migratory bird with a Wisconsin hunting season, and we participate in a leg banding study each year to help monitor their populations across the country. The birds are captured alive and unharmed; they walk into a trap to get at some sunflower seeds and millet, and can’t figure out how to walk back out. We record information on age and sex of the birds, put a leg band on them and let them go. We will start banding doves as the first broods get old enough to fly here in the next couple of weeks. We also band woodcock, but we do not use walk-in traps for them. We use trained pointing dogs to find woodcock broods. When woodcock sense danger, they sit extremely still, hoping their coloring will camouflage them. The banders can then capture, band and release them.
We band ducks and geese as well. Wildlife technician Eric Kroening is our head bird bander up here. He tells me that our best method for capturing duck broods is by going out at night with a boat and motoring up on broods spotted with a search light. In other parts of the state, they use walk-in traps or rocket nets. If you have never seen a rocket net, it is pretty much exactly what it sounds like. The ducks walk or fly into a nice big pile of bait, like corn, placed on shore. Workers are hiding nearby in a blind, waiting for the right number of ducks to visit the bait. On the dry land side of the bait, there is a big net folded up on the ground in a long line. One edge of the net is secured to a few rockets stuck in pipes sticking out of the ground. The opposite edge of the net is staked to the ground. When the ducks are in place, BLAST OFF! The net is launched over the ducks. The ducks flap around a bit; then they walk, trying to get out of the net. Workers and volunteers scramble to secure the ducks under the net. They check the birds’ age and sex, determine the breed of the ducks, put leg bands on them and let them go.
Canada geese are banded during their flightless stage, when their young are fuzzy or just getting their feathers. We round them up with boats and herd them on shore between two nets and into a cage. We determine age and sex, put on a leg band and release them. If you have a site where there are 30 geese or so once the eggs hatch, let me know-we are looking for goose banding sites.
Jeremy Holtz is a wildlife biologist with the Wisconsin DNR and writes a weekly column in the Star Journal. To contact him, call (715) 365-8999.