Connections between Wintering, Migration and Breeding Areas
To evaluate long-range movement and identify connectivity between wintering, staging and breeding areas, female black ducks will be captured and fitted with GPS satellite transmitters in wintering areas located in Delaware, Ohio, New Jersey, New York and Virginia. During winter 2007/2008 and 2008/2009, a total of 60 adult females will be radioed (10 per year per location). The satellite transmitters will allow researchers to identify important wintering, staging and breeding areas, local and large-scale habitat use patterns, migration chronology, flight paths and duration of stay in staging and wintering locations. Please visit our Follow the Ducks page to see maps of the ducks' progress.
Local Habitat Use and Behavior
To determine local habitat use, field crews study the ducks’ activities and amount of time spent in different habitat types. To achieve this task, black ducks are bait-trapped from mid- to late November and a sample of 30 females is fitted with radios each year. The radioed hens are then followed via truck-mounted or handheld telemetry from fall through their departure in late spring. Locations are then plotted on aerial photographs and later digitized for spatial analysis.
Black duck behavior also will be examined via time-activity budgets. Flocks of black ducks are observed from concealed blinds between sunrise and sunset. Behaviors are categorized and recorded as feeding, loafing, sleeping, comfort, courtship, agonistic and locomotion. This information helps identify the importance of different habitats to specific waterfowl needs.
To determine current food habits of wintering black ducks, a sample of birds will be collected along the Atlantic coast. The esophagus will be removed from each collected bird and food items will be sorted and identified. Frequency of occurrence, average weight and average volume of food items will be determined. Historic food habits data for black ducks will be compared with present food habits. In addition, food habits information will be compared with food availability determined for various habitats used by black ducks.
Food Availability and Depletion
To evaluate food availability and food depletion, food samples are taken from multiple sites within available habitats. Samples are collected in mid- to late October, allowing researchers to estimate the total amount of food available when black ducks first arrive in early autumn. Because the level of food availability is expected to change throughout the course of the winter and spring, food samples are taken again in midwinter (mid- to late December) and in early spring (early March). Food samples include both invertebrates and aquatic plants, which are important black duck foods. Waterfowl and shorebird presence also is documented at each sampling site.
To determine the true metabolizable energy of foods commonly found in the black duck diet, captive black ducks will be precision fed a known amount of six test foods including saltmarsh snails, killifish, fiddler crabs, widgeon grass vegetation, widgeon grass seeds and saltmarsh cordgrass seeds. Following precision feeding, excreta will be collected from test birds for a 48-hour period. Gross energy of test foods and excreta samples will be determined via bomb calorimetry to estimate how much energy black ducks metabolize from each food type.
Landscape Analysis of Habitat Availability and Change
In order to determine how much wintering habitat along the Atlantic coast is currently available, researchers will conduct an analysis of the landscape between Maine and Maryland. This type of spatial analysis requires satellite imagery and GIS (Geographic Information Systems). This analysis will allow researchers to determine if there is adequate habitat to support current wintering populations of black ducks and wintering population goals set forth in the North American Waterfowl Management Plan (NAWMP).