A look at wood ducks
By JOHN K. FLORES
Quiet can only be explained by measuring the decibels of the things that interrupt silence. And, only the mesmerizing muffled sound of a tugboat’s engines straining to push barges against the Mississippi River’s current could be heard.
On the other side of the levee overlooking a barrow pit sat Louisiana Department of Wildlife and Fisheries Biologist Paul Link and his crew of volunteers, waiting in the dark for that crucial moment at twilight when he’d fire the rockets.
Tiny beads of sweat started to form on Link’s face and forehead, a hazard from sitting in the stifling heat and humidity inside the blind where he held the detonator.
Raising a pair of binoculars to his eyes, studying the bait-site at water’s edge where skittish wood ducks nervously started to commit, Link whispered, “This is when I get anxious. I start thinking, ‘Did I connect the wires to the rockets? Is the net set at the right height?’ There are 50 things that must all correctly come together for a successful rocket net shot. And, if only 49 of those things come together, the outcome can range from nothing happening when you try to detonate the charges to killing a bunch of birds or injuring or killing yourself and volunteers.”
Link has an intense personality and works hard. When I got the call from the biologist that he would be making the morning shot, it was 9 p.m., and if I wanted to join them, we were to meet at 5 a.m. It was pretty clear he didn’t work a typical workweek like most people. He had already put in nearly 40-hours and it wasn’t even Thursday yet. I’d have to get up at 3 a.m. to make the drive in time to meet him.
Picking up the detonator, he whispered again, only this time with trepidation in his voice. “Crap, there’s a blue heron in the target area.”
With woodies gorging themselves on the bait, it wouldn’t take long for them to fill their crops and swim off. A shot at that instance would quite likely result in capturing the heron. But, it could also injure, or worse — kill it. So, Link decided to wait.
Banding wood ducks is something the Louisiana Department of Wildlife and Fisheries does annually when it receives notification from the U.S. Fish and Wildlife Service. Unlike traditional breeding population surveys conducted on the northern breeding grounds for other species of ducks, there isn’t one for wood ducks.
LDWF Waterfowl Study Leader, Larry Reynolds said, “The thing about wood ducks is that we do not have a population survey for them — it’s not possible. Wood ducks hang around in the trees, and so we don’t have a good reliable population survey like we do on the prairie breeding survey. We fly every single year hundreds of thousands of miles of transects. We’ve got ground crews to create visibility correction factors. We’ve got one of the finest wildlife surveys on the face of the earth to estimate the population size of the ducks that we harvest, but we can’t do that for wood ducks because of the habitat they use and the broad distribution of the species.”
In the absence of a reliable population survey, Reynolds says wildlife managers rely heavily on banding wood ducks to estimate survival rate and subsequently harvest rate, allowing them to look at population dynamics in response to management actions.
From complete closure in the early part of the 20th century, to a limit of one, then two starting in 1962, wood ducks have gone from the brink to an important bird in a hunters bag limit. As habitat conditions improved in the framework of harvest regulations set by biologists throughout various wood duck population ranges north and south in the Atlantic, Central and Mississippi flyways, biologists — during flyway meetings — felt the species could handle more harvest pressure.
“We’ve reforested a lot of tracks at our WMAs like Ouachita and Sherburne,” Reynolds said. “The Mississippi alluvial valley used to be one big bottom land forest. But, it got cleared. I can’t remember how much of it’s cleared, but it’s over half that are now soybean, rice fields, and that kind of stuff. Our forests were also cut to support the war effort in the 40s. Now a lot of those forests are coming back. So, habitat for wood ducks has actually been increasing in the latter part of the 20th Century.”
In 2008-2009, the wood duck bag limit was increased from two to three. Significant, when considering biologists expected at least a 13 percent increase in harvest as a result of the third bird.
The decision to increase the bag limit didn’t come without angst and considerable gut wrenching from those who argued that the previous limit of two was too restrictive. But, the decision wasn’t an arbitrary one and took in a wealth of data.
Reynolds, in pointing to the studies and data in the development of decision metrics, sighted the work of Pam Garrettson and Paul Padding of the U.S. Fish and Wildlife Service and Greg Malcom a waterfowl biologist from Georgia.
Reynolds said, “Garrettson looked at survival rates. She looked at harvest rates. She looked at all of the banding and harvest data for wood ducks. She looked at Christmas bird counts and she looked at bird breeding surveys in creating a model. Through modeling exercises, it appeared that the wood duck population could easily tolerate an increase in harvest.”
After numerous discussions, it was determined that all populations of wood ducks would be used in monitoring the three-bird limit with some conservative decisions built in to account for error; one using the upper bounds of the statistical confidence limits of the established harvest rate.
The LDWF doesn’t band ducks just so hunters can have a third-bird bag limit. On the contrary, banding is how the department and biologists determine survival rates to monitor and manage the health of wood duck populations with its partners around the country. But, with wood duck harvest rates derived from banding data and statistical confidence limits being what they are, the more birds the department bands, the higher the accuracy or “confidence” there is in the limits that have been set.
Reynolds explained, “We set this maximum harvest rate at 15 percent – that’s what the USF&WS came out with. So, we band birds, we shoot birds, and we get an estimate of the harvest rate. But, the estimate has a confidence limit around it. And, they said as long as the 95 percent confidence limit of the harvest rate estimate does not exceed 15 percent, then we can have a 3-bird wood duck bag limit. But, if the 95 percent confidence limit exceeds 15 percent, then we’ve got to go back to a 2-bird bag limit.”
Reynolds is determined that the LDWF does its part by setting higher department quotas than the USF&WS sets for the state to compensate for possible banding shortfalls elsewhere.
Reynolds said, “Because wood ducks are an important bird in the bag here we want to make sure we maintain that harvest opportunity. In 2010, the six states in our region banded 9,068 wood ducks. Going back to 2001 to 2010 the lowest number the six states collectively banded was around 7,000 and the highest 10,000. Since we’re a big wood duck kill state, just from a biological standpoint that’s significant. In my opinion, that banding share is 1,500. And, that’s not a scientific argument. That’s a socio-political argument. We’re going to do our share.
Link, with more than 1,000 shots under his belt, gambled that the heron had moved far enough away, depressing the detonator. The rockets fired and carried the net through the air over the unsuspecting wood ducks, capturing 120; a solid number that biologists will be no less confident in when monitoring survival of wood ducks in the future.
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