The winter inventory is an aerial survey conducted annually by much the same 

 personnel over the same area during the first two weeks in January. It 

 provides the only direct visual estimates of Maine's waterfowl populations. 

 Waterfowl counts are made at elevations between 100 and 300 feet. The entire 

 shoreline, including islands and ledges, are surveyed in each wildlife 

 management unit. A number of factors may influence the accuracy of the 

 counts . 



Light and tide conditions vary constantly during the course of the survey, and 

 several species form into common flocks. Color patterns and flight 

 characteristics of goldeneyes, bufflehead, and mergansers are most easily 

 differentiated. Other common waterfowl of Maine are readily identifiable 

 because they occur in small flocks, usually less than 100. In Chesapeake Bay 

 and Bear River marshes, flocks number in the tens of thousands, whereas in 

 Maine, flocks rarely reach 500 individuals, and most are much smaller. 

 Because of probable error and limitations just described, statistical 

 appraisal is not applicable. The annual wintering population estimates for 

 major species from 1952 to 1979 are shown in table 15-5. The annual 

 population estimates of 8 species of wintering waterfowl are given for each 

 waterfowl inventory unit (figures 15-4 to 15-11). 



Among the species in the winter inventory, the black duck is perhaps the 

 easiest to identify, consequently, winter estimates of its abundance are 

 likely to be most accurate. The increase in black duck counts Statewide from 

 1960 to 1975, and the sharp decline in Casco Bay, Muscongus Bay, and Penobscot 

 Bay units since 1975 are unexplainable . The winter population estimates for 

 most duck species were much higher in 1975 than in 1979 (table 15-5). It is 

 not known whether the wintering population changes reflected by the data were 

 caused by weather or other factors in the wintering grounds, or by habitat 

 alteration or breeding failures in other areas of its overall range. 



Breeding Populations 



The status of waterfowl breeding populations in coastal Maine and the wildlife 

 management units is best assessed by using the results of a recent compilation 

 of 21 years of production data (MDIFW) . The numbers of broods of each species 

 were counted periodically and listed by wetland type or by wildlife management 

 unit. The data in tables 15-6 to 15-8 are used in this analysis. The species 

 composition of breeding waterfowl populations in the coastal wildlife 

 management units in 1956 to 1965 and 1966 to 1976, and the State as a whole, 

 are given in table 15-6. Breeding ducks were largely black ducks, wood ducks, 

 ring-necked ducks, and goldeneyes. The data also show a sizeable reduction in 

 the percentage of black ducks and wood ducks from 1956 to 1965 and 1966 to 

 1976, and an increase in ring-necked and goldeneye ducks. Although changes 

 were shown for other waterfowl, the numbers were too small for analysis. 



The duck brood estimates (eider excluded) for the waterfowl of Maine are based 

 on the average number of duck broods per acre for seven inland wetland types 

 from 1956 to 1965 and from 1966 to 1976 (table 15-7). These estimates 

 probably are conservative because there are no data from several tidal wetland 

 types which are known to produce young, and because the estimates are based on 

 actual counts (many could have been missed) . 



15-14 



