Maryland Wood Duck Initiative (MWDI) volunteers and other nest box program sponsors participating in MWDI's data surveys identified Hooded Merganser nest use in 34 sites (32 separate boxes and 2 broods observed to have hatched from natural cavities). 28 of these nests successfully hatched including the 2 cavity broods (82%). Egg counts were available from 25 of the nest sites. 226 total eggs were laid in both Success & Unsuccessful nests in 26 boxes. In the 20 nest box hatches, 150 ducklings were estimated to have been produced from 182 eggs (82%). The gross hatch rate (Total eggs laid all boxes / ducklings hatched) was 66%, comparable numbers to MWDI's 2006 wood duck results.

Details by box site are included in the attached spreadsheets. Most nests (27of 34) were located on Maryland's western shore in PG, Carroll, Montgomery and Charles Counties. Kent County was the only eastern shore county to confirm hooded merganser use in 2006.

The hooded nests were confirmed by a combination of unhatched eggs, hen on nest sittings, membranes attached to shell fragments and shell fragments where adequate nest cleaning had previously occurred. Shell fragments were measured in several areas, pictures taken and more than one inspector was involved in each confirmation. Other than work done by Frank McGilvrey at Patuxent Wildlife Research Center, Cliff Brown, Executive Director of MWDI was present for all other confirmations. 1,025 boxes were involved in MWDI's Public Lands Survey for the 2006 nest season. 577 of these boxes were included in the sites where hooded nest were found. Thus, hooded use was 5.9% of total boxes on these sites and 3.3% overall. The most nests were found at McKee Beshers in Montgomery County (11 - 10% of total project site).

Interviews and information with other box program sponsors strongly suggests that hooded merganser nesting has been routine in many parts of Maryland for several years although the breadth and scope appears to be increasing. Lack of information to confidently distinguish hooded eggs from wood duck eggs is probably one reason more confirmed nests have not been reported. MWDI was not focused on hooded nest counts in 2005 although we documented several. Mixed wood duck and hooded nests can also be especially difficult to assess depending on the timing and frequency of nest checks as well as residual shell fragments from prior year's use.

For example, in Harford Co., Karen Cifranik with a group of students (Harford Glen Educational Center) reported that in 2005 after flushing a wood duck from a box, her group then found a hooded merganser sitting in the same box when it was opened. Rick Latshaw, MD DNR - MT Nebo WMA (Garret Co), also reports having seen hooded mergansers in his boxes but kept no data and was not aware how to distinguish shell fragments between the wood duck and hooded. MWDI's sample of boxes is also smaller on several eastern shore counties at this time relative to other areas and identification techniques are not yet as focused.

In 2007, hooded merganser nests have also been confirmed in Baltimore County (Loch Raven Reservoir - 2) and Somerset Co. on the lower eastern shore. Hooded nests have also been confirmed at the same general sites as 2006 except in Charles but data collection is only partially completed.

Cliff Brown
20-May-07