8 6 Craig A. Harper, James F. Parnell, and Eric G. Bolen 



amounts of flooded vegetation and downed timber (such as 1-2 in our study) 

 seem to provide habitat for a larger standing stock and increased production over 

 riverine sites (e.g., non-impounded blackwater streams). High diversity and bio- 

 mass of invertebrates make an important contribution to nesting and brooding 

 wood ducks. 



Wood ducks utilized the impoundments as nesting and brooding sites 

 during both years of the study. One wood duck nest was located in 1991 (nine 

 boxes were available). In 1992, two wood duck nests were among 15 bird nests 

 found in 21 boxes available on the impoundments. Other birds using the nest 

 boxes included eastern bluebirds (Sialia sialis), Carolina wrens (Thryothorus 

 ludovicianus), great-crested flycatchers (Myiarchus crinitus), and prothonotary 

 warblers (Protonotaria citrea). 



Broods were sighted 34 times on 1-1 during the survey period (May - 

 June 1992). Because no eggs hatched in nest boxes at 1-1, these broods either 

 emigrated from other wetlands or hatched from nests in natural cavities nearby. 

 The thick cover of fetterbush, titi, wax myrtle, honeysuckle (Lonicerajaponica), 

 and blackberry {Rubus spp.) around and within 1-1, coupled with an abundance 

 of invertebrates, made this impoundment an attractive brood rearing site. Molt- 

 ing adults also were observed within 1-1 during brood surveys. Broods and 

 adults were observed using floating logs in 1-1 as loafing sites. 



Brood habitat also was favorable at 1-2, where broods were sighted on 

 35 occasions. The largest of these consisted of seven ducklings, but because this 

 brood was observed before any clutches hatched in nest boxes located at 1-2, the 

 ducklings must have come from another site or a natural cavity in the local area. 

 Movement of broods should not be unexpected in light of the mobility 

 McGilvrey (1969) recorded for wood duck broods on impoundments elsewhere. 



Thick cover at both 1-1 and 1-2 precluded precise censuses of broods; 

 however, two broods were commonly observed concurrently on each impound- 

 ment, thus providing a conservative estimate of use. This compares favorably 

 with the average of three broods per sampling date observed on impoundments 

 of 0.71 to 2.70 ha in South Dakota, where visibility was much greater (see Rum- 

 ble and Flake 1982). Similarly, Belanger and Couture (1988) recorded the great- 

 est density of dabbling duck broods (2.0 broods/ha) on man-made ponds con- 

 taining >30% cover and 0.35 g of invertebrate biomass per m 2 , similar to condi- 

 tions at 1-1 and 1-2. 



Broods were not observed at 1-3 during the survey, and the 10 ducklings 

 that hatched from a nest box there in 1991 left the impoundment shortly after- 

 ward. The relative lack of invertebrates and plant cover, along with the small 

 size of 1-3, likely contributed to the absence of broods (Sousa and Farmer 1983, 

 Drobney and Fredrickson 1979, Haramis 1990). Continued use of these 

 impoundments as brood cover will depend on the schedule of flooding and 

 drawdown. Brooding, molting, and roosting wood ducks depend on thick cover. 



