Wood Duck (Aix Sponsa)

Transcription

1 Baker River Project Terrestrial Working Group Analysis Species Drafted by Sarie Nichol Habitat Type: Snag/Log Dependent Wood Duck (Aix Sponsa) Species Biology and Population Status: *** For additional information on species biology and population status refer to The Birds of North America, No *** At the Muscatatuck National Wildlife Refuge in southcentral Indiana, the daily survival rate for wood duck nests was ± 0.01 and nest success was estimated to be 0.22 (Robb and Bookhout 1995). Meanwhile, results of 512 wood duck nests from 9 studies throughout the eastern United States reported 40% mean nesting success (Ryan et al 1998). Studies comparing nesting productivity between natural cavities and nest boxes found successful parasitized natural cavities hatched 14.2 ducklings/nest, while successful normal natural cavities hatched 9.7 ducklings/nest. Means from nesting boxes across the wood duck range found 15.5 ducklings hatched per successful parasitized clutch and 9.5 ducklings hatched per successful unparasitized clutch (Ryan et al 1998). Although moderate intraspecific nest parasitism is a normal feature of wood duck breeding in natural cavities, the incidence of nest parasitism in eastern United States and Oregon is lower in natural nest cavities than among artificial nest boxes. Nest boxes often occur in dense aggregations making them highly visible and accessible to parasitizing females (Ryan et al 1998). Adult female wood ducks demonstrate philopatry, a homing ability enabling them to remember a previous year s nest site or even a specific nesting cavity. Philopatry is also strong among yearling hens that seek nest sites close to places where they hatched (Shurtleff and Savage 1996). While female wood ducks have a predetermined propensity to return to successful nest sites of the previous year, male wood ducks may migrate to new nesting grounds on an annual basis. As the subdominate member of a mating pair, male wood ducks follow females to nesting grounds, thus a male paired last spring with a female nesting in northern Minnesota may find himself following this season s mate to her nesting grounds in Florida (Shurtleff and Savage 1996). Observations of intraspecific parasitism at artificial nest boxes in Illnois demonstrates the importance of site fidelity and nest site competition among wood ducks. In this study, females would return to nest boxes used in the previous year and lay a clutch regardless if the box was already occupied. Both the host and parasite would behave so similarly that it was difficult for researchers

2 to differentiate between the two, eventually one of these females was forced to depart, usually the parasite and usually following a fight. Displaced females would generally nest in a nearby box and attempt to renest, the following year, in the box they had parasitized. Parasitism was noticeably restricted among close kin. In general, fidelity to a specific nest is important to females as the location is known and nest quality has been proven in previous years (Semel and Sherman 2001). Intra- and interspecific competition for nest sites is largely a function of population density, nest site availability and behavioral adaptations to habitat characteristics of cavity sites in addition to the features of a specific nesting cavity. Predation can decrease competition by lowering population densities thus increasing the availability of suitable nest sites and other limiting resources, indirectly affecting wood duck productivity (Robb and Bookhout 1995). A study to determine if premature mate removal affects female wood duck incubation behavior found that paired and widowed females did not differ significantly with respect to incubation period, body mass, or nesting and hatching success. Widowed females, however, were less likely to produce a second brood during the same season. Thus mate removal may affect future reproductive opportunities throughout the wood duck s southern range, where breeding seasons are long and females regularly produce two broods per season (Manlove and Hepp 1998). The combination of reduced predation risk and the need for neonates to be more functionally mature at hatch explains longer incubation periods among cavitynesting waterfowl. Ducklings need to be coordinated for a fairly laborious descent from the cavity nest that involves a series of vertical leaps to ascend the cavity wall and then scaling the remaining distance (Manlove and Hepp 2000). Age and size-specific variation in reproductive performance occurs among female wood ducks. Yearling hens have been found to initiate nests days later than older females, and heavier females, independent of age, nest earlier than smaller females. Late-nesting yearlings survive better than yearling females that initiate nests early. Conversely, adult females nesting early produce large clutches, show a high hatching success, are at less risk from predators and increase their chances of successfully producing a second brood during the same season (Hepp and Kennamer 1993). Although most wood duck hens breed as yearlings, ducklings hatched late in the season may exhibit delayed sexual maturity and begin breeding in their second year (Fehlig 1997). If frightened off their nests, adult females leave their eggs uncovered and often soiled, the scent of which is thought to repel invading predators (Shurtleff and Savage 1996). The wood duck in neither a state listed species or a state candiate species for listing nor is it a species of concern by priority habitat type in Washington State (WDFW 2000). 2

3 Habitat Requirements: ***For additional information on habitat requirements refer to The Birds of North America, No *** Availability of suitable nesting cavities is regarded as the primary limiting resource for wood ducks (Robb and Bookhout 1995). Studies conducted in Illinois, however, found predation, rather than nest site availability to be the main factor limiting wood duck production (Yetter et al 1999). At Muscatatuck National Wildlife Refuge in southcentral Indiana minimum wood duck nest densities were 0.13 ± 0.08 nest/ha in 1984 and 0.08 ± 0.03 nest/ha in Stands containing mature and/or sawlog trees had a higher density of suitable nesting cavities (1.69 ± 0.22 cavities/ha) than in younger stands (0.31 ± 0.11 cavity/ha). American beech, red maple, and American sycamore produced the majority of suitable nesting cavities. Tree cavities with vertical facing entrances were highly selected for. In addition, cavity volume, entrance area and diameter of the bole at the entrance were important distinguishing features of cavities used by wood ducks. Nest success is predicted to be higher in cavities with smaller entrance holes located at greater heights. Trees ranging from cm diameter at breast height (dbh) provide optimum cavity size in trunks. In addition, mature trees produce branch cavities with preferred dimensions for wood duck nests (Robb and Bookhout 1995). Studies conducted throughout the Midwest and eastern portions of the wood duck s range found densities ranging from 1.26 to 5.5 cavities/ha. Management recommendations in Illinois suggest 1 nest for every 2 ha (Yetter et al 1999). Wood ducks select pileated woodpecker cavities for nesting sites because the small openings afford greater protection from some predators. Because wood ducks show high nest site fidelity, selecting cavities with features that may reduce the risk of predation is expected in areas with high predator densities. In addition, wood ducks using artificial nest boxes in Ontario regularly selected boxes with smaller entrance holes (Yetter et al 1999). At Muscatatuck National Wildlife Refuge, early spring wood duck nesting success was greater for nests located further from water. Relatively poor nest success for near water wood duck nests was attributed to shoreline predators, such as raccoons (Robb and Bookhout 1995). In Minnesota, wood duck nest cavities were predominately situated close to the nearest forest opening and water. Similarly, in southcentral Indiana distance from nest sites to the nearest forest opening was shorter than were other suitable wood duck nesting cavities found in large, contiguous, bottomland stands. These findings suggest that female wood ducks will search for nesting cavities from the forest edge into the forest interior (Robb and Bookhout 1995). Although nest sites near wetlands are preferred by wood ducks, production from natural cavities in upland forests near river floodplains may be underestimated, particularly where extensive loss and fragmentation of floodplain forests has occurred. A study conducted in the upper Mississippi River system found that 3

4 82% of wood ducks were produced from upland nests that were >1 km from permanent water (Ryan et al 1998). Ponds with interlaced fallen logs, and patches of shoreline vegetation (i.e. cattails and willows) offer better protection than large open ponds or swamps for broods. Small, heavily overgrown ponds, with numerous areas of shrubs and brush offering refuge from predators and places for sunning and preening, tend to support a greater number of wood duck broods. Under optimum habitat conditions, a single acre (~ 0.40 ha) can support ten to fifteen broods, equaling an estimated one hundred ducklings, without exhausting the carbohydrate and protein resources of the area (Shurtleff and Savage 1996). Unlike most other dabbling ducks, wood ducks do not have a stable home range. Their home range varies both spatially and temporally with the rise and fall of floodwaters (Fehlig 1997). Food Resources and Foraging Behavior: *** For additional information on food resources and foraging behavior refer to The Birds of North America, No *** Feeding experiments conducted on captive wood ducks found that survivorship and reproduction was impaired when diets were restricted by 15 to 20%. A lower threshold is expected for wild wood ducks, as they have greater energy costs than those kept in captivity. These findings suggest conservation strategies need to be implemented in primary winter foraging habitats (bottomland hardwood ecosystems) for migrating and wintering wood ducks (Demarest et al 1997). Although acorns are the preferred food of the adult wood duck s diet, a variety of nuts, seeds and berries are also consumed by adult wood ducks including hickory and beech nuts, black tupelo, wild rice, duckweed, sedge, bur reed and dogwood (Shurtleff and Savage 1996). It has been calculated that one female wood duck needs to consume over 5,000 insects in order to produce a single egg. Within two weeks, a hen will consume roughly her own body weight in food. When the last egg is laid the female will remain inside the nesting cavity, and incubate her eggs for 30 days, leaving only to join her mate in brief feeding bouts during early morning and late evening (Shurtleff and Savage 1996). During the egg-laying cycle, female ducks are constantly foraging for insects, among shoreline grasses and probing the mud along the edges of ponds or waterways while male mates swim leisurely alongside alert and on guard (Shurtleff and Savage 1996). Attendance by breeding males throughout egglaying and incubation may increase female wood duck foraging efficiency by decreasing harassment from other males (Manlove and Hepp 1998). 4

5 Habitat Alteration and the Effects of Human Disturbance: *** For more information on habitat alteration and the effects of human disturbance refer to The Birds of North America No *** Agriculture, logging, urbanization, and wetland conversion has substantially reduced the amount of forest bottomlands throughout the wood duck s range. Landscape alterations indirectly and directly affect availability of winter food resources for wood ducks in forested wetlands. Limited or poor quality winter food resources may delay physiological and behavioral functions in ducks, such as pair formation. Late pair formation in females may result in delayed nesting and decreased egg mass, clutch size and duckling survival (Demarest et al 1997). Flood-control projects alter hydrology and flooding in lowland forests occupied by nesting wood ducks (Demarest et al 1997). Winter line-transect surveys of wood ducks in Mississippi greentree reservoirs found that duck numbers decreased with increasing river levels (Sherman et al 1995). In Illinois, flooding killed a number of suitable nesting trees and in areas where flooding persisted throughout the nesting season, no successful wood duck nests were found. While some studies indicate that floodplain tree species can withstand more than 2 years of permanent flooding, results from the Illinois study found protracted flooding during one or more growing seasons decreased tree survival (up to ~ 43% of suitable nesting trees died) and altered forest composition (Yetter et al 1999). Seasonal and annual fluctuations in water levels, due to drought or flood conditions, during prenesting and egg laying may affect female wood ducks ability to acquire the nutritional resources necessary to produce and incubate clutches. Shallow water invertebrates are an important food source, providing the proteins and minerals essential for egg formation. Despite changes in distribution and surface water depth, wood ducks demonstrate strong fidelity to floodplain forest sites (Ryan et al 1998). Wood ducks are sensitive to dioxin and furan contamination. A wetland in central Arkansas, located near a former chemical plant that manufactured the herbicide 2,4,5-T, found polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran residues in wood duck eggs. Nest success, hatching success and production were suppressed at nesting sites up to 58 km downstream from the former facility (White and Seginak 1994). In the late nineteenth and early twentieth centuries overhunting had severely reduced wood duck populations to the brink of extinction. The Migratory Bird Treaty Act between the U.S. and Canada in 1918 gave the wood duck protected status and reduced hunting seasons to fall and early winter (Fehlig 1997). In addition, nest box programs established throughout North America since the 1930 s have provided suitable nest sites in many areas where habitat loss and fragmentation have limited the number of natural nesting cavities for wood ducks ( 1999). 5

6 Studies Conducted in the Baker River Watershed: *** Local information still needs to be added. *** Literature Cited: Anonymous Wood Duck (Aix sponsa). U.S. Department of Agriculture, Natural Resources Conservation Service, Madison, MS, and Wildlife Habitat Council, Silver Spring, MD. Fish and Wildlife Habitat Management Leaflet. 12 pages. Jamestown, ND: Northern Prairie Wildlife Research Center Home Page. November Demarest, D.W., R.M. Kaminski, L.A. Brennan, and C.R. Boyle Body-mass, survival, and pairing consequences of winter-diet restriction in wood ducks. Journal of Wildlife Management 61(3): Fehlig, R Aix sponsa: Wood Duck. Available online at November Hepp, G.R., and R.A. Kennamer Effects of age and experience on reproductive performance of wood ducks. Ecology 74(7): Manlove, C.A. and G.R. Hepp Effects of mate removal on incubation behavior and reproductive success of female wood ducks. Condor 100: and Patterns of nest attendance in female wood ducks. Condor 102: Robb, J.R., and T.A. Bookhout Factors influencing wood duck use of natural cavities. Journal of Wildlife Management 59(2): Ryan, D.C., R.J. Kawula, and R.J. Gates Breeding biology of wood ducks using natural cavities in southern Illinois. Journal of Wildlife Management 62(1): Semel, B., and P.W. Sherman Intraspecific parasitism and nest-site competition in wood ducks. Animal Behavior 61: Sherman, D.E., R.M. Kaminski, and B.D. Leopold Winter line-transect surveys of wood ducks and mallards in Mississippi greentree reservoirs. Wildlife Society Bulletin 23(2): Shurtleff and Savage The home and habits of the wood duck. Pages in Dunham, J., editor. The Wood Duck and the Mandarin: The Northern Wood Ducks. University of California Press, Berkeley, CA. USA. 6

7 Washington Department of Fish and Wildlife Washington gap analysis. Washington Cooperative Fish and Wildlife Research Unit, University of Washington, Seattle, WA. USA. Available online at ftp:// /pub/gapdata/birds/gifs/aisp/gif. November State listed species; State candidate species; Species of concern by priority habitat type. Olympia WA. USA. White, D.H., and J.T. Seginak Dioxins and furans linked to reproductive impairment in wood ducks. Journal of Wildlife Management 58(1): Yetter, A.P., S.P. Havera, and C.S. Hine Natural-cavity use by nesting wood ducks in Illinois. Journal of Wildlife Management 63(2): References: Colwell, S.V., R.A. Kennamer, and L. Brisbin, Jr Radiocesium patterns in wood duck eggs and nesting females in a contaminated reservoir. Journal of Wildlife Management 60(1): Conner, R.N., C.E. Shackelford, D. Saenz, and R.R. Schaefer Interactions between nesting pileated woodpeckers and wood ducks. Wilson Bulletin 113(2): Hepp, G.R., and F.C. Bellrose Wood duck; Aix sponsa. The Birds of North America, No. 169: 1-24., and C.A. Manlove A comparison of methoxyflurane and propofol to reduce nest abandonment by wood ducks. Wildlife Society Bulletin 29(2): Kennamer, R.A., S.K. Alsum, and S.V. Colwell Composition of wood duck eggs in relation to egg size, laying sequence, and skipped days of laying. Auk 114(3): White, D.H., and D.J. Hoffman Effects of polychlorinated dibenzo-p-dioxins and dibenzofurans on nesting wood ducks (Aix sponsa) at Bayou Meto, Arkansas. Environmental Health Perspectives 103(4): Wilson, S.F., and N.A.M. Verbeek Patterns of wood duck nest temperatures during egg-laying and incubation. Condor 97: