Second North American Sea Duck Conference - Patuxent Wildlife ...

SECOND NORTH AMERICAN SEA DUCK CONFERENCE
HABITAT USE BY RED-BREASTED MERGANSER BROODS
AT KOUCHIBOUGUAC NATIONAL PARK, NEW BRUNSWICK
Shawn Craik and Roger D. Titman
Department of Natural Resource Sciences, McGill University Macdonald Campus; shawn.craik@m
ail.mcgill.ca
Recruitment of juvenile waterfowl to fall populations requires that adequate brood-rearing habitat
be available. Despite breeding in a variety of fresh and salt water wetlands, little is known about the
brood habitat requirements of nearctic red-breasted mergansers (Mergus serrator) that breed in marine
environments, particularly at coastal barrier island sites. The objective of the study was to determine
habitat selection by red-breasted merganser broods at two scales (home range and sites within home
range). We used a landscape-level approach to habitat selection where discrete coastal habitats were
delineated from the Canadian Wildlife Service’s Maritime Wetlands Inventory. Over three years
(2002-2004), habitat use was determined for 11 radio-marked merganser broods originating from a
breeding colony located on three barrier islands at Kouchibouguac National Park, New Brunswick. At
both scales of study, radio-marked broods preferred continental and barrier island estuarine intertidal
flats. Adjacent tidal wetlands of estuarine intertidal flat habitat provided young broods (< 10 days
post-hatch) with concealed resting and loafing sites amidst emergent salt water cordgrass (Spartina
alterniflora). Older broods typically did not seek emergent vegetation and were often observed loafing
along the sandy shores of the intertidal flats located along the barrier island complex. Preliminary fish
sampling evidence suggested that the intertidal regions of the estuarine system support a large number
of small fish species (e.g. Atlantic silversides Menidia menidia) in high abundance throughout the late
summer brood-rearing period. Tidal river habitat was avoided for brood-rearing despite its proximity
to the nesting islands and apparent large prey base. Interspecific competition with common merganser
(Mergus merganser) broods at tidal river sites may be a proximate factor in the evolution of habitat
selection by mergansers at Kouchibouguac National Park. Determining habitat requirements will lead
to future investigations concerning impacts by foraging merganser broods on small fish populations in
the estuarine system at Kouchibouguac.
NOV. 7-11, 2005 ANNAPOLIS, MARYLAND, USA
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