Changes in Waterfowl Abundance and Species Composition on Louisiana Coastal Wildlife Management Areas and Refuges 2004-2016

Aerial waterfowl surveys are conducted on major wintering areas to provide regional population indices and determine habitat use of non-breeding waterfowl. Coastal Louisiana supports more than one quarter of the continental dabbling duck population during winter. Thus, consid- erable effort is allocated to monitoring waterfowl abundance in coastal Louisiana with implications for future waterfowl habitat management in the region. We conducted monthly surveys on nine state-owned coastal wildlife management areas and refuges, November–January 2004–2016. Across all sites and survey years, the most commonly observed species were gadwall (Mareca strepera), green-winged teal (Anas crecca), and mallard (Anas platy- rhynchos). Despite increases in continental breeding population indices to near record highs, their populations were stable region-wide in coastal Lou- isiana, with minor declines on some heavily-hunted and unmanaged areas. In contrast, northern pintail (Anas acuta) experienced a precipitous decline region-wide and on four of the nine major wintering areas surveyed. We hypothesize that this decline is related to changes in coastal and agricultural habitats. Diving duck populations tended to be increasing or stable: lesser scaup (Aythya affinis) increased on two areas, and ring-necked ducks (Aythya collaris) increased substantially on one area, perhaps because of increases in water depth from increased rainfall and changes in water management capacity on these areas. Our results demonstrate the utility of aerial surveys for monitoring waterfowl populations and documenting important trend data for commonly observed species. We also pose hypotheses about habitat change to help guide future analyses and coastal waterfowl management.

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