Influence Of Habitat Conditions On Nesting Activity Of Wood Ducks Aix Sponsa In Tree Cavities

Abstract: Wood duck breeding biology has largely been studied in artificial nest boxes, but environmental influences on nesting biology must be studied in the context within which wood ducks evolved (i.e. natural tree cavities). Previous work suggested that intra- and inter-seasonal changes in abundance of invertebrate foods and/or accessibility of tree cavities may affect nesting season length and the breeding chronology of wood duck hens. This study examined the relationships of intra-seasonal and annual variation in invertebrate food abundance and leaf emergence with nesting chronology, nesting effort, and nest parasitism rates in a southern Illinois' wood duck population that nests in natural cavities. Nest chronology, nesting effort, and parasitism rates were studied during 1994 -- 1998 and 2001 -- 2002. I modeled wetland conditions with local precipitation and stage of the Mississippi River. Wetland invertebrate food abundance was measured by sweep- net sampling in seasonal and semi-permanent wetlands in 2001 and 2002. Invertebrate sampling was completed during four nesting periods (egg laying, late egg laying/early incubation, incubation! early hatch, hatch) during 2001 -- 2002. Weekly leaf emergence in 2001 and 2002 was measured with a Model-A Spherical Densiometer, from the onset of leaf emergence through the period of maximum upper story leaf coverage. Annual nesting effort of radiomarked hens known to incubate clutches ranged from 42% - 70% throughout the study. Clutch sizes >14 (indicative of nest parasitism) ranged from 8% - 43% during the study and varied inversely with nesting effort. High nesting effort was observed in years with the most stable water levels during egg laying and incubation. Invertebrate biomass did not differ throughout the 2001 (P = 0.76) and 2002 (P = 0.17) nesting seasons. During hatch, densities in 2002 were 1.7 times higher than egg laying and incubation/early hatch; however did not differ from late egg laying/early incubation (P = 0.05). Mean invertebrate densities were not significantly different (P = 0.87) during 2001. Two commonly consumed invertebrates known to occur during nest initiation and hatch, Isopoda and Diptera (primarily Chironomidae), were 10.2% and 18.4% more numerous during the egg laying and hatch (P

Natural cavity nesting, brood movements, and survivorship of wood ducks (Aix sponsa) were studied for 2 years (1984-85) at Muscatatuck National Wildlife Refuge in south-central Indiana. Study objectives were to (1)determine the availability and use of natural tree cavities for wood duck nesting; (2) determine the availability and use of brood habitat;and (3) calculate a fledging rate for wood duck broods on Muscatatuck,NWR. Suitable tree cavities for wood duck nesting were sampled via 381 0.5-ha plots poststratified into bottomland and upland categories.Examination of potential cavities showed that 15% (122) of apparent entrances (789) were suitable cavities, and the 3,127-ha refuge had 2,195 +- 537 (95%) CI) cavities suitable for wood duck nesting. Areas with mature or sawlog trees had 1.69 +- 0.22 (x +- SE) cavities per ha and all the forested area on the refuge contained 1.23 +- 0.16 (x +- SE)cavities per ha. American beech (Fagus grandifolia), red maple (Acer rubrum), and Ame.

Reference on the wood duck includes basic biology, life history, population characteristics, and research and management techniques.

Various ecological and biological aspects of the wood duck (Aix sponsa)were investigated in the elm-ash-maple (Ulmus-Fraxinus- Acer) bottomland timber impoundments at Montezuma National Wildlife Refuge in central New York. Major areas of research included (a) a description of the forest stand with special reference to the ecological impact of seasonal impoundment, (b) the pattern of occurrence and use of natural nest cavities by wood ducks, (c) the nesting response of wood ducks to nest boxes, (d) an investigation of dump nesting, (e) mark-recapture estimates of annual duckling production, (f) a study of vernal pool invertebrates, and (g) a study of brood usage and survival. Spring flooded green timber was found to produce ideal breeding habitat for wood ducks in providing ample acceptable nest cavities (1.60 per acre)and an abundance of early spring (vernal pool) invertebrate food resources, including fairy shrimp (Chirocephalopsis bundyi), cladocerans (Daphnia pulex), mosquito lar.