Week 7

I recently had the privilege of visiting the smallest refuge in the National Wildlife Refuge System. Mille Lacs NWR consists of two islands (Spirit and Hennepin) located on Lake Mille Lacs in Minnesota. Both islands are important to the local Native American people.

Spirit Island

Hennepin Island

In addition, Hennepin Island hosts a breeding population of common terns, which are a state threatened species in Minnesota. We spent one morning on Hennepin Island surveying tern nests and helping to protect them from harm.

Terns are pretty minimalist when it comes to nesting. As the above picture shows, they basically plop their eggs down in sand or gravel and call it a day. The first thing we did was count nests and how many eggs were in each nest. 

Tern Chick

We also installed bird houses to help provide the chicks with some protection from the sun.

Tern nests are heavily predated by gulls, who will peck holes into tern eggs. In order to help combat this, a rope grid is established on the half of Hennepin island that hosts tern nests (the other half of the island only has gull and cormorant nests). While the grid still allows the smaller tern to navigate the land, it prevents the larger gulls from entering and destroying eggs. Unfortunately, if the ropes aren't taut, birds that fly into the grid can get caught. I cut this tern free (it was still alive!), and then we reestablished the grid and tightened all of the ropes. 

Gull Nest

Unfortunately, the grid isn't enough to discourage gulls from using the island. Gull eggs found inside of the grid are destroyed. On the other half of the island, gull eggs are oiled with 100% vegetable oil. Eggs are porous, allowing the chick developing inside to breathe. By applying oil, the pores are sealed and the chick will die, but the adult gulls will continue to care for their nests. This keeps the gulls from laying even more eggs.

Visiting Mille Lacs NWR was fun and informative! 

Back at Sherburne, we completed the forest plots for fire monitoring. We also established new plots for future study in the area where cattle are grazing. 

Dragonfly

Milkweed

Mullen

Black-Eyed Susan