But he's never been able to see what the nocturnal birds do at night until now.
An infrared camera and microphone on top of a pole in willow thickets on Montana rangeland is aimed at a long-eared owl nest. Holt, founder and director of the Owl Research Institute in Charlo, Mont., believes there are four or five eggs in the nest.
He can't wait to see how the birds share child-rearing, how they interact with other species and how many naps they take during the night.
"There are only so many animals in the world admired by masses of people. There are penguins, some bears, whales and owls," Holt said.
The 24/7 long-eared owl cam goes live Thursday and is believed to be the first ever set up in the wild, Holt said. It is part of an explore.org Internet initiative, underwritten by the Santa Monica-based Annenberg Foundation.
The birds can be found throughout North America and Europe, "but because they are nocturnal and studies are so few, we don't have a good handle on what is going on in the populations."
He knows in some areas, including his, the birds and rangeland are disappearing together, but there isn't enough research data to make blanket statements, he said.
He does know that long-eared owls don't have long ears -- and great horned owls don't have horns.
"They are all feathers and wings," Holt said. An average female long-ear weighs between 11 and 12 ounces, while an average male weighs between 9 and 10 ounces.
They settle into deserted magpie nests, come in colors that match their environment and have feather tufts in the middle of their heads that Holt believes evolved for camouflage.
They are friend to farmers and home owners because they eat voles or field mice. For many years, researchers collected "puke balls" -- the thumb-sized pellets the owls regurgitate after a full meal. They've identified 35,000 prey and over 95 percent were voles, Holt said.
Some people collect the balls, dry them out and sell them to schools, Holt said, but the institute provides them to area schools for free.
Students tease the pellets apart to examine the small skulls of the voles and identify other species that have been eaten (the occasional mouse, pocket gopher and bird). Such lessons have become very popular in high school science classes, he said.
"Long-eared owls are seasonally monogamous, but they have multiple mates over a lifetime," the researcher said.
If one of the birds returns to the nest the next year, it will be the male. Owlets are the same. If a chick returns to the area to mate, it will probably be the male.
So what do cam watchers have to look forward to?
The female laid her eggs a few days apart, so the births will be staggered too. The chicks will start getting big in two weeks and in three, the mother will start sitting outside the nest. A few days more and the chicks will screech for their food.
Soon the babies will start branching or climbing clumsily onto branches above the nest. They will fall, but also keep moving further from the nest. Their screaming demands for food will grow louder, Holt said. It is likely the birds will move out of camera range as they venture further away. When the mother owl is finished nesting, when the chicks are around 11 weeks old, she will take off and "most of the time, we never see the female again." The father owl will continue to feed the chicks until they leave, again in a staggered sequence.
"Predation influences leaving the next as early as possible," Holt said, describing the hazards of a raccoon invasion.
Long-eared owls will live five to 10 years,
The institute will keep the cam trained on the nest until there is nothing left to see, Holt said.
The Pearls of the Planet series has put cameras on osprey, puffins, brown bears and polar bears, generating millions of streaming hours from all over the world, said Charlie Annenberg, the founder of explore.org and vice president and director of the foundation his grandfather Walter Annenberg founded.
Click here to see the cam.
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