Bald eagles on duty
Proud national bird soars over Iowa
BALD EAGLE NESTS were relatively easy to see prior to trees getting full leaf growth. Now many nests are more concealed even if the viewer knows where to look. Where eagles build nests, or reuse nests they built years ago, may make viewing easier or downright hard. Privacy for eagles is still an over-riding need for them. Prudence on the part of humans to observe from a distance is always a good thing.
For the eagles at Decorah, a nest in close proximity to people was the eagle’s choice, not mans. If observations with binoculars, spotting scopes or 24/7 remote cameras can safely add to the sciences about the knowledge of these huge raptors, so much the better. Decorah eaglets, once fledged (out of the nest) may be subject to a live trapping technique somewhere near the trout fish hatchery. A minimal time is needed to put leg bands on the eaglets and perhaps a GPS tracking device attached to the body. Following a young eaglet as it explores new territories during the rest of the summer and fall reveals a lot about dispersal of these majestic birds.
An eagle nest map for Marshall County locates about 17 nests, of which at least one dozen are active. If there are a dozen nests and an average of two eaglets successfully raised per nest, we will have at least 24 new eagles being hatched and raised locally. Available habitat is being exploited by bald eagles in a widely dispersed arrangement. Water and being close to water of a lake, pond or stream seems to prevail. The Iowa River corridor becomes and obvious locations as large tall trees within the floodplain offer nest sites.
Across all of Iowa, 2018 data shows 377 active bald eagle territories. Observers tried to document fledgling success in 2018 and came up with 1.38 young per nest which equates to 412 new eagles. Adult eagles calling Iowa home are well over 750. And that number is four times the goal Department of Natural Resources staffers set back in the year 1983 for the eagle recovery plan. Current eagle numbers suggest that eagle numbers have leveled out as they reach a carrying capacity for territories.
BIRD LEG BANDS are a way of helping to identify any bird, large or small, from a distance without capturing the critter. One trick of the trade involves additional colored leg bands in addition to the light weight aluminum USFWS bands with the official numbering system.
According to Anna Buckardt Thomas, DNR avian ecologist, bird migration is mind boggling happening of nature. “How can a small bird of only a few ounces fly thousands of miles one way and find the exact same tree it nested in last year?” When she was studying Golden-winged Warblers, she placed a series of colored leg bands on the legs to make positive identification possible from a distance. Three summers of observation in Wisconsin proved that this warbler made round trips from Costa Rica every year to return to the same tree for a new nesting season.
Migration is an adaption for many species of birds to take advantage of emerging food sources as spring and summer weather warms and new crops of buds, bugs and seeds are everywhere. Programmed into a tiny bird brain are the necessary navigational mechanisms of their genetic code. They may use a combination of longer day lengths, the sun’s position in the sky, earth’s magnetic field and physical landmarks of rivers, fields and forests patterns. Mother Nature is amazing in her intricate ways for all wild critters. Scientists can try hard to decipher all the factors of migration, find some answers and as always have new questions arise. So in the end, just be glad that the birds themselves do not have to think about migration, they just do it. Good for them.
TERNS, a graceful waterbird, were seen over Sand Lake recently. They are migrating toward northern climes and stopping by water sources to look for food. At Lake Red Rock, particularly below the spillway of the dam, terns can be seen easily plying the airwaves as they hunt for fish. As a tern passed overhead at Sand Lake, its long narrow and pointed white wings and forked tail feathers were primary identification factors. Terns also have a black top to their head and hold their orange colored beak straight down as they fly. Any small fish close to the water’s surface is likely to become tern food.
DEER FAWNS will be born at the end of May and into early June. Time is arriving soon for doe deer to give birth to a fawn or fawns. Single births are common for first time doe deer. Twins are common thereafter until the doe reaches full maturity in about 5 years of more. About 10 to 15 percent of very old doe deer will have triplets. And even for twins or triplets, they may or may not have different fathers.
After a seven month long gestation, doe deer giving birth will happen. The deer herd size will expand and replace animals taken out since last year due to disease, car accidents and hunting quota off takes. Iowa’s habitat carrying capacity for deer is never really tested. Iowa could grow lots more deer if managers wanted to so so, But they have a balance to maintain between potential and practical, science based goals and political realities. Iowa deer hunt regulations strive to maintain a balance that tends to work for most people.
As for fawns, if people come across a fawn, make the mistake of thinking the baby deer is “abandoned” when it is not and then think they need to be a hero by attempting to feed the baby deer, lots of bad things are likely to happen. For the fawn, it is away from its mother. The doe deer is close by and knows when to feed her baby. Doe deer are the primary and best solution for raising fawns. For people, observe from a distance only and leave the raising of baby deer to the professional, its mother. Do not be stupid and take in a fawn deer.
Garry Brandenburg is the retired director of the Marshall County Conservation Board. He is a gradute of Iowa State University with a BS degree in Fish & Wildlife Biology.
Contact him at:
P.O. Box 96
Albion, IA 50005