Delta Scientists Answering the Pressing Questions of the Day
By Dr. Frank Rohwer
Delta Scientific Director
For several years waterfowl scientists have wondered if the U.S. side of the breeding grounds was exporting ducks to Canada. Research being conducted by Delta student Laura Beaudoin (Ph.D. student at University of Guelph) suggests that might be the case.
Laura has been working on Delta’s North Dakota predator management sites, where she’s been studying the movement of ducks after the breeding season by placing radio transmitters on juveniles just before they reached flight stage. Her marked sample included birds raised on trapped blocks as well as birds from the non-trapped comparison areas.
She then documented survival and movements until the birds headed for the wintering grounds. The work resumed the following spring when the birds returned to the breeding grounds.
Laura spent much of her spring in an airplane tracking her radio-marked birds. Mallards tend to home to their natal area in early spring, and that’s exactly what she found. But the radio-marked birds then dispersed to sites that were far from the North Dakota prairies, many of them settling in Canada.
We’re not certain why, but speculate that the habitat in the Dakotas had reached the saturation point and was incapable of supporting more ducks. Thanks to the Conservation Reserve Program and low fox numbers that resulted from mange and increasing coyote numbers, duck production has been off the charts across North Dakota.
Unfortunately, production in Canada has been low because of ongoing habitat losses north of the border. Nest success in our recent evaluations in parklands in southern Manitoba hasn’t approached break-even production levels in many years. That means duck production would have been better if those hens had stayed in the Dakotas.
Ducks and trees go together like oil and water. At least, that’s the opinion of many waterfowl managers, including some who believe removing trees, which serve as habitat for predators, would enhance duck nest success.
Would a tree-removal program work? That’s what Sarah Thompson, a Ph.D. candidate from the University of Minnesota, will be trying to find out as she examines the link between trees, predators and duck nests.
One of the human alterations of the prairies was lots of tree planting. These tree lines may increase local nest predation by serving as preferred habitats for nest predators. Managers at some sites are actively removing trees.
Sarah is looking at various sites in southwestern Minnesota that have trees or where trees were removed. Sarah’s 2008 results suggested tree removal increased duck nest success, but 2009 results failed to show the same pattern. This will be the final year of field work for Sarah.
Kevin Ringleman learned waterfowl basics in his home state of North Dakota, but now he is studying ducks in a very different location: central California. Kevin’s research looks at the interactions between predators, several managed nesting habitats and duck nests. Like many biologists, Kevin and his crew go out and find lots of nests in several different planted habitats. At the same time Kevin captures local predators like skunks and raccoons and fits them with some sophisticated electronic gadgetry.
Think of the GPS unit on your car’s dashboard, but the GPS unit Kevin is using is so tiny it fits on a collar that is around a skunk’s neck. Kevin’s GPS collars essentially give him a complete picture of every place his marked animals go for 21 days.
The spatial information about predator travels and duck nest locations should make it possible for Kevin to understand how nest location impacts the probability that an animal will discover that nest. The only tricky part is getting enough collars on predators and getting them back. Once he gets them, Kevin can download the stored information on predator locations.
David Iles (M.S. student, Utah State) is starting field work this spring looking at common eider productivity at a colony along the shores of Hudson’s Bay. While he’s just starting, David has the benefit of a long-term data set due to years of monitoring by biologists associated with a large snow goose research project.
David is particularly interested in catastrophic nest failure at eider colonies. Several predators – polar bears, wolves, herring gulls and bald eagles – have been documented as the cause of near-complete failures in production.
However, the role of earlier thawing of the arctic icepack may be influencing the predator numbers or behavior and thereby influencing the frequency of massive breeding failures. With the long term data set, David has a unique ability to try and look at how climate influences predators and ultimately eider populations.
Bruce Davis (Ph.D. student at Louisiana State) is nearing the end of his field work examining the movements, habitat use, and survival of mottled ducks in Louisiana. Bruce’s work is based on radio-telemetry monitoring of birds that are captured during the period in the summer when mottled ducks, like most waterfowl, molt their wing feathers and have a flightless period for three to four weeks.
Bruce has had the unique opportunity to examine mottled ducks during some unusual times. During his three years of field work, the Louisiana coast was buffeted by two major hurricanes – Ike and Gustav – which displaced the ducks but caused no known mortalities.
Unfortunately, the major oil spill off the coast is likely to have far more detrimental impacts on the mottled ducks and a host of other coastal species if that oil gets into coastal marshlands.
Brandt Meixell, a Ph.D. student at University of Minnesota, has directed his research to understanding the influence of “low pathogenic” strain of avian influenza (AI) on ducks. The name is a bit misleading, because we don’t have good information on how AI actually impacts ducks. Brandt selected two very different geographic areas to pursue his research – namely, prairie habitats in the Dakotas and high-latitude wetlands in the boreal forest at Minto Flats, Alaska.
These sites have a long history of waterfowl work, so Brandt can look at condition and vital rates – nest success, brood survival and adult survival – for birds today and contrast that with data obtained in the same area 30 years earlier.
By sampling large numbers of ducks Brandt also can look at condition and survival for infected and virus non-infected birds. In his first two years, Brandt and his team have handled over 6,000 birds, so he should have ample data for some very robust analyses. In addition to the field component, Brandt will also examine survival for dosed and non-treated mallard ducklings in captivity.
Has the winter distribution of ducks changed over the years? A lot of hunters seem to think so--the internet is rife with anecdotes about how the changing winter distribution of birds has impacted hunting success. Unfortunately, good scientific analyses are scarce. Recently Delta scientists took on a project to examine how harvest distribution might have changed in recent decades.
Step one was to take a look a the harvest dates for mallards over the 40 years of data collection as part of the U.S. Fish and Wildlife Service Parts Collection Survey. The data set has well over a million records with harvest date, location and age/sex of the mallard.
We asked the question: “has the harvest date shifted within each state?” The preliminary analyses suggest the answer is “yes.” Southern and mid-latitude states have had later harvest dates in most flyways, but we can’t say for certain what has caused the change. Establishing cause-and-effect is a ways down the road. the current analysis doesn’t correct for things like regulations and ending dates, which likely have a significant impact on mean harvest date.
Our next step is to look at data for several other species to see if the same patterns exist for gadwall, teal and other species.
Almost 30 years ago Delta’s then-scientific director Dr. Bruce Batt reported that captive mallards at the Delta station had great consistency in their individual nesting dates from year to year. Waterfowl biologists had presumed that all the later-nesting females were re-nesting after an earlier failed attempt. So did Batt’s finding apply in wild populations?
Answering this question was one aspect of Tim Kimmel’s research, which he is wrapping up this spring. Tim (M.S. student, Louisiana State) had the unique opportunity to test for individual consistency because he could utilize a banded population of almost 1,000 female mallards that had known nesting histories established by another student, Matt Pieron.
Tim found that 37 percent of females initiate nests within the same seven-day window in subsequent years. He also discovered that young females do not nest any later than older females and they show the same pattern of decreasing numbers of eggs laid as the season progresses. In other words, the wild mallards did behave like the captive studied at Delta three decades earlier.
Lucien Laborde is working on the other side of the equation from ducks conducting research on duck hunters. The long-term pattern for hunter numbers is a bleak picture. Unless we retain existing hunters and recruit new ones, duck hunting faces a bleak future. Luke is focused on hunter retentions.
He’s trying to get handle on what factors cause hunters to be satisfied and disappointed with their waterfowl hunting. Prior work suggests that it is a far more complicated story than simply examining hunting success. Luke started his work with a major survey of Louisiana waterfowl hunters, but this season he plans to expand his work to other states in the Mississippi Flyway.
I think of Beth Ross (Ph.D. student , Utah State) as Delta’s “Scaup Rocket Scientist.” Beth has taken on the difficult task of using all the available scaup data to better understand what is causing the population to decline.
Beth has been systematically working through the scaup problem, starting with the most fundamental wildlife data, abundance data. More specifically, Beth asked how the pairing status of scaup in different areas of the breeding pair survey region has changed since 1955 when systematic duck counts began.
Beth developed mathematical models known as “multi-state occupancy models” to assess whether the occurrence of paired birds vs. non-breeders has changed over time. In recent years there have been more paired birds in the Dakotas and fewer in some eastern regions. But the northern boreal forest is the region that most significantly impacts population size and productivity. Beth is continuing this sort of sophisticated and detailed examination of all the available scaup data sets – counts, banding, and harvest – to get a far more complete view of the factors influencing scaup numbers.
Two M.S. students from the University of Guelph, Paul Guerra and Jessica Rosenberg, have been gathering information at the Norfolk County ALUS pilot project in an effort to learn how to efficiently provide environmental goods and services on a province-wide scale for rural lands in Ontario.
One particular goal is to get a handle on “community capacity” which is the essential trust and reputation needed to successfully deliver any new farm program. Another aspect of research is a detailed of both the on-farm and program economics of ALUS type programs in the Ontario.
The final objective was to understand “institutional innovation’, so that we can identify critical success factors and institutional requirements to sustain market-exchange relationships in the provision of environmental goods and services and to identify institutional and policy impediments for the development of local and regional markets for environmental goods and services. This clearly isn’t typical duck research, but making environmental programs work in an agricultural environment is all about the habitat that ducks need to thrive.