Performing Department
School of Renewable Natural Resources
Non Technical Summary
In North America, the Wood Duck is the most abundant species of breeding waterfowl south of 40° N latitude, and the species is commonly found in bottomland hardwood forests along the Mississippi River and in riparian areas further east. This was not always the case. Historically, the Wood Duck's year-round abundance near populated areas led to especially acute levels of overharvest until the passage of the Migratory Bird Treaty Act in 1918. By the mid-1940s, populations had recovered to sufficient levels to permit harvest in most states, making Wood Ducks one of the greatest conservation success stories in waterfowl management. Today, populations are stable or increasing, and Wood Ducks are the most abundant birds in hunter bags in several southeastern states, including Alabama, Georgia, and the Carolinas. Moreover, they provide consistent hunting opportunities in states like Louisiana, where more than 100,000 residents hunted waterfowl in 2011, pumping more than $119 million dollars into the local economy. The economic and cultural importance of waterfowl in southern states creates a vital need for sustainable management of the waterfowl resource to ensure healthy populations persist well into the future.The success of Wood Ducks is often attributed to the large-scale establishment of nest box programs, which can help mitigate the loss of natural cavities where forests have been cleared. The majority of Wood Duck recruits at a continental level are derived from natural cavities, with local exceptions in California and Nevada. This trend not only emphasizes the importance of bottomland hardwood habitats for nesting Wood Ducks, but it also suggests that nest box programs should be evaluated for effectiveness, especially in geographies where natural cavities are not limiting. Wood Ducks are brood parasites (lay eggs in boxes of other nesting Wood Ducks), and in such cases where highly visible boxes are distributed at high densities, high rates of parasitism have the potential to reduce reduce Wood Duck productivity. Periodic assessment of Wood Duck nest boxes in terms of use, nest success, and recruitment could help inform improvements to state and federal wildlife conservation programs and ensure continued success of Wood Duck populations.In addition to providing valuable habitat for Wood Ducks, nest boxes are also used by Black-bellied Whistling-Ducks. Black-bellied Whistling-Ducks are most commonly found in Central and South America, with a historic range just reaching southern Texas. However, since the 1980s they have expanded their breeding range northward and have established stable populations in Arizona, Texas, Louisiana, and Florida, with anecdotal sightings of individuals recorded in many of the lower 48 states. Black-bellied Whistling-Ducks nest both on the ground in upland areas and in cavitiesand thus have the potential to compete with Wood Ducks for breeding territories and nest cavities, as well as to reduce Wood Duck production through nest parasitism. Virtually nothing is known about Black-bellied Whistling-Duck breeding biologyor how Black-Bellied Whistling-Ducks could influence Wood Duck population dynamics. As such, evaluating overlap in the timing of nesting, habitat preferences, and potential competition between these two species is an important first step in understanding how the two species interact. This project will evaluate Wood Duck and Whistling-Duck nesting ecology through a combination of monitoring nest boxes, marking adults and ducklings with bands/tags, and analyzing historic banding data.
Animal Health Component
0%
Research Effort Categories
Basic
10%
Applied
90%
Developmental
(N/A)
Goals / Objectives
Estimate annual nest box use, rates of conspecific and interspecific parasitism, and duckling production from representative bottomland hardwood sites in northern and central Louisiana.Determine local- and landscape-level habitat characteristics associated with levels of box use, parasitism, and duckling production.Estimate recruitment of marked ducklings into the breeding population, and landscape-level habitat characteristics that may influence recruitment.Evaluate temporal overlap, habitat overlap, and potential competition between Wood Ducks and Black-bellied Whistling-Ducks.Analyze existing female box-banded recovery and recapture data to inform local estimates of Wood Duck demographics.
Project Methods
My project will target three sites and nearby properties supporting >100 nest boxes each: Sherburne Wildlife Management Area (central Louisiana), and the Woodworth Outdoor Education Facility (northern Louisiana). Sites were selected to represent of a range of bottomland hardwood habitat conditions available to cavity-nesting waterfowl across the state. Boxes will be monitored following standard protocols approximately once per week from 15 January to 15 August, with more frequent checks as occupied boxes approach hatching. When a box is discovered occupied, each egg will be candled to determine incubation stage (Weller 1956) and individually numbered on the side and the rounded (air space) end with a Sharpie to determine egg success. Each egg will be measured and weighed to attempt post-hoc categorization of nest parasitism and to evaluate the influence of egg morphometrics on hatch success. Nests will be considered parasitized if the total number of eggs exceeds 15, if more than one egg per day appears in the box, or if a clutch contains eggs from more than one species (Baldassarre 2014).Within two weeks of the onset of incubation, female Wood Ducks will be captured on the box and banded with a size 5A aluminum USGS leg band. Detailed morphometric measurements will be collected, including true tarsus length, wing chord, culmen width and length, white eye patch length and width, and mass. Blood samples will also be drawn using a tarsus prick, blotted onto dry matrix for later relatedness analysis at the University of California-Davis (Eadie et al. unpublished). As the hatch date approaches, nests will be checked at one- to three-day intervals. Ducklings will be captured on the nest within 24 h of hatching (hatch date estimated by candling eggs), sexed by cloacal examination (Hochbaum 1942), weighed, and measured for tarsus length. Half of all ducklings will be microchipped with a 2x12 mm Cyntag Passive Integrated Transponder (PIT tag) inserted subcutaneously between the scapula. The remaining ducklings will be double-marked with matching serial Monel web tags. By splitting our duckling sample between marking methods, we will be able to evaluate potential survival bias in web-tagged ducklings, because anecdotal reports suggest that metal web tags may attract aquatic predators such as fish and turtles. In years two and three of the study, all females captured on the nest will be checked for PIT tags before banding to evaluate recruitment of ducklings into the local breeding population. For boxes used by Whistling-Ducks, we will attempt to capture and PIT-tag both the male and female (Whistling-Ducks are unique among Anatidae in that both sexes incubate [James et al. 2012]). For boxes occupied by Whistling-Ducks, we propose to use a PIT-tag reader placed at the box entrance to gather additional information on partitioning of bi-parental care responsibilities, a behavior for which we have no quantitative data for this species.At each box, we will measure the vegetation type and cover surrounding the box, distance of the box to water, nest box height, distance to nearest neighbor, and volumetric/construction metrics of the box itself (to the extent that they are variable). We anticipate using cover boards to measure visual obstruction, and range-finders and GIS to quantify distances between boxes and water. Cover measurements will be made on the day at which a box is discovered occupied to prevent phenological bias in linking vegetation growth to demographic outcomes (Ringelman and Skaggs 2019), which also probably represents our best measure of adaptive selection for particular habitat attributes. In hydrologically dynamic habitats, distance to water will be measured when the nest is discovered active (to evaluate habitat selection) and on the day the clutch hatches (which could influence brood survival).All data will be entered digitally into Wildnote, a web- and app-based scientific data management software that supports online backup, version control, and relational databases. This project is designed to interface with ongoing Wood Duck and Whistling-Duck nesting research being undertaken at Clemson University, Mississippi State University, and the University of Delaware. Through establishment of this collaboration and formal data-sharing agreements, our overarching goal is to develop a region-wide synthesis of cavity-nesting waterfowl ecology across the eastern United States.The Louisiana Department of Wildlife and Fisheries annually maintains and monitors >2,000 nest boxes across the state, and effort has been made over the last decade to capture and band females on the nest. We will leverage this existing long-term dataset and develop multi-state mark-recapture models to estimate demographic parameters such as breeding site fidelity, survival, and recruitment. The exact nature of the dataset is currently unknown, so analyses will proceed in exploratory fashion.