A DIPPICULT DECISION ,- TEENS OVER GUI.le by Dan McAakill 
     
    
   
   
    
     The Natural History Society of Prince Edward Island Ltd. began studying 
     
     the Hillsborough Bridge Tern Colony in 1988 after Greater Black-backed Gulls 
     
     started nesting in this colony. Between 1988 and 1990, the production of 
     
     VCommon Terns in this colony steadily declined to a very low number in 1990. 
     
     The reason'was predation of the Common Terns eggs and young by the Greater 
     
     Blackrbacked Gulls. Region wide the population of Common Terns has declined-_ 
     
     while-the population of gulls has increased dramatically because of the amount' 
     
     Of “aete released by people from processing facilities and homes. 
     
    

    
     In 1991, the Society, under permit, installed gull exclosure wires on 
     
     the Hillsborough Bridge Piers to allow the Common Terns attempting nesting at 
     
     this site to successfully produce young. Mr. Ben Ho ling and others recorded 
     
     the results of this exclosure experiment and 196 ter nests were tended. .At 
     
     least 50 recently'fledged young were seen on the adjacent beaches on one day. 
     
     thus confirming that the colony had successfully fledged terns in 1991. ‘As 
     
     the nesting was spread out over a considerable time period, success was much 
     
     higher than the 50 fledged chicks. 
     
    

    
     The history of this tern colony is reviewed in the Island Naturalist # 
     
     111 (July—August, 1990) and the Society will be publishing the 1991 study 
     
     results later this year. Since the Greater Black-backed Gulls started nesting‘ 
     
     at this site, the Common Tern fledging suCCess declined to virtually zero by 
     
     1990. -While the 1991 efforts may have offered a reprieve to the colony, the 
     
     condition of the piers has steadily deteriorated. The amount of spelling rock 
     
     and the state of disrepair of the piers makes the climbing of many of these 
     
     piers very dangerous due to the probability of a stone block falling on a 
     
     climber or the boat and carrying workers under the'water's surface. Even if 
     
     the appropriate diving equipment was on site, it is improbable that a person- 
     
     could be freed from under one of these large stones before suffocating. The 
     
     Society's Tern Committee, after evaluating the results of the work and the 
     
     probability of an accident, has recommended that a safer alternative be! 
     
     utilized in protecting the tern colony. ’ 7 ‘ . 
     
    

    
     The Society discussed the situation and potential solutions at the April' 
     
     7th, 1992 monthly meeting. The Society had previously contacted the Canadian 
     
     Wildlife Service and the CWS indicated that it did not have the resources to 
     
     undertake the work and thus could not take action themselves. They did 
     
     indicate that they would provide a permit to allow the selective removal of 
     
     the adult Greater Black-backed Gulls provided that the Fish and Wildlife 
     
     Division supported this step and.that the police would allow the use of a high 
     
     powered air rifle at this site. An expert marksman volunteered to assist the 
     
     Society in carrying out this selective kill. After consideration of the 
     
     various alternatives to support the continued health of the Hillsborough Tern 
     
     Colony, the Society voted to remove, under the appropriate permits and by 
     
     selective means, the small number of nesting Greater Black-backed Gulls 
     
     (thought to be 8 gulls) from the Hillsborough Piers. An air rifle was tested 
     
     and proved to have inadequate accuracy at the distance betweenlthe clay road 
     
     and the piers. The Canadian Wildlife Service recommended the use of a 22 
     
    

    
     ~ caliber rifle and on May 9th and May 11th the pair of Greater Black-backed 
     
     Gulls nesting on Pier number 1 were successfully removed. Three other pairs 
     
     of Greater Black-backed Gulls were nesting on the piers on this date. The 
     
     removal of‘a third Greater Black-backed Gull led to the gulls abandoning the 
     
     .piers for this spring. Terns have now fully occupied the 8 remaining piers. 
     
    
   
   
    
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