The return of robins is a definite indication that spring has arrived. Another indicator can be found in the return of great blue herons. About this time of year they can be seen flying off to a stream or an open pond where they will search for food until ice-out on our area lakes provides them with a diet of fish, frogs, crayfish, and an occasional young turtle or duckling.
Herons nest in colonies, called rookeries or heronries. The good thing about that is that there are always plenty of eyes watching for potential enemies, which include egg-eating predators such as crows and raccoons.
The long pointed beak of a heron is used for catching prey, but it can also cause some serious damage to an intruder. The bad thing about nesting in colonies is that large numbers of birds produce large amounts of waste material. Over time, the acidity will begin killing the trees containing the nests.
Many of you see the evidence left behind on your docks, swimming rafts, and boat canopies. In banking terms, herons might be considered a valued customer because every time they show up, they leave a deposit. I know that attempt at humor simply stinks, which might be a fair descriptive word, considering the subject.
If you haven't cleaned out your wood duck nesting boxes yet, it might be a good idea to add that to your list of things to do over the next week or so. I realize that hollow trees don't get a yearly cleaning and wood ducks still nest in them. Your nesting boxes may still attract wood ducks, even if you don't clean them out, but if you want to increase the chances of your boxes being used, take a look in them just to make sure squirrels hadn't filled them with leaves for their winter's home, or that a wasp nest didn't find its way in there sometime last summer, or that the moisture in the wood shavings that are used for nesting material hasn't attracted ants or mold.
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If you are putting up new boxes, consider using the Wood Duck Society's Best Practices design. That includes attaching them to wooden or metal poles about six feet above the ground and including a predator guard right below the nesting box. The design can be seen in Carrol Henderson's "Woodworking for Wildlife" book or by going to the Minnesota Wood Duck Society's Web site at www.woodducksociety.com . Their annual meeting will be held on Saturday, April 3 at the Wargo Nature Center in Centerville. If you want to attend, but need directions or additional information, the Web site gives details.
Let's see how many wood duck nesting reports we can compile this spring. Monitor your nesting boxes throughout the months of April and May and then let me know what's in them. Our survey will include the number of nests surveyed, number of eggs laid, number of eggs hatched, and number of surviving ducklings.
Steve Maanum can be reached at sdmaanum@unitelc.com .
