in a direct disturbance or affect the habitat which in turn affects the bird 

 populations for many years. Other problems of shorter duration such as the 

 presence of rats, mink ( Mustela vison ), dogs, and cats on islands are fre- 

 quently too subtle to be noticed except by the experienced observer. 

 Inventory data must be used prudently. 



The shifting of colonies from one site to another over a period of years 

 is characteristic of some species, for example terns and herons. To designate 

 present colony sites for protection at the expense of permitting abuse to 

 former or potential colony sites could result in a drastic decline of those 

 species in the future. Groups or clusters of islands should be protected and 

 managed as units for colonial nesting waterbirds. 



INVENTORY METHODS 



Aerial Versus Ground Inventories 



In both 1976 and 1977, the inventories were initiated by surveying the 

 coastal islands from a fixed-wing amphibious aircraft. Fixed-wing aircraft 

 were used for the survey because they offered greater flight speed and 

 longer sustained flights than helicopters. Approximately 20 hours of flight 

 time was required to survey the entire study area. 



Ground counts of the colonies were considered essential. During the 

 spring surveys at altitudes of less than 100 m and at 80 knots/hour, common 

 puffins, black guillemots, razorbills, laughing gulls. Leach's storm-petrels, 

 and black-crowned night herons were rarely seen because of their low 

 numbers, inconspicuous coloration, small size, or secretive habits. It was 

 also impossible to differentiate common, Arctic, and roseate terns. 

 Therefore, an inventory of Maine's coastal waterbird colonies would be ^^ery 

 incomplete without ground verification of species composition and breeding 

 populations. 



A flight in a small Bell helicopter during the 1977 nesting season re- 

 vealed some advantages and disadvantages of surveying the Maine colonies by 

 helicopter. Excellent visibility permitted fairly precise estimates of the 

 number of nests of double-crested cormorants and great blue herons and also 

 adult gulls and terns. However, the advantage to the observer appeared to 

 be outweighed by the disadvantage to the birds. Black guillemots and 

 common eiders were disturbed by the approaching helicopter. Black 

 guillemots took flight and if overtaken by the helicopter dove directly from 

 the air into the water. Substantial losses of nests of common eiders were 

 anticipated due to predation by gulls when incubating eiders were flushed, 

 because gulls returned to the colony sooner than eiders. The nest predation 

 could be somewhat alleviated by landing the helicopter and covering eider 

 nests with down as was done when ground checks were made. The habitat 

 and small size of the islands frequently precluded landing a helicopter without 

 damage to the nesting cover or nests. 



OWNERSHIP OF COLONY SITES 



The fact that a large proportion (73%) of the seabirds and wading birds 

 nested in colonies located on privately-owned lands is cause for some concern. 



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