Egrets, herons monitored at Cook County forest preserve

After a short boat ride from the shores of Northwest Cook County's Baker's Lake, wildlife biologists and veterinarians visit a small island with a towering wooden rookery to conduct medical work ups and band birds.

The rookery is home to about 300 nests for great egrets, great blue herons and cormorants, which flood the man-made structure in spring and early summer.

Each year, the Forest Preserves of Cook County's wildlife division leads the short expedition as part of its heron rookery banding program. During the visit, the biologists and veterinarians draw blood, which allows them to understand the health of the birds as well as the health of the environment.

"Because the birds expose themselves to other animals and the environment in general, they serve as biomonitors. This information enables us to make better decisions regarding conservation and restoration efforts," said Chris Anchor, Forest Preserves of Cook County senior wildlife biologist.

Additionally, the research can inform biologists about any potential human health concerns.

The bands allow researchers to track movements of the birds, which will migrate to other states during colder months. Birds banded in the forest preserves have been recorded in Minnesota, Georgia and Alabama, and as far away as Cape Canaveral, Florida.

"By tracking the birds' movements and conducting continued health assessments, we can find out what diseases the bird has been exposed to and what kind of titer it's throwing. (Titer is the concentration of antibodies in the blood.) It can tell us whether the animal has active disease, what it's been exposed to and sometimes when it was exposed," explains Anchor.

In addition to the Baker's Lake rookery, the Forest Preserves has rookeries at Busse Woods, McGinnis Slough, Powderhorn Lake and other preserves.

For information on the Forest Preserves of Cook County visit fpdcc.com.