GULL EXCLOSURES INSTALLED by San McAskiT‘

On Aprii 22nd and 23rd, voTunteers of the NaturaT History Society of Prince

Edward Isiand Toaded heavy cod Tine, 2 x cw W“ 45, metai strapping, and tooTs in a k{”/’

Boston whaTer and a Zodiac raft so that _._- .. -_— -

guTT echosures coqu be instaTTed on __ __ ___..

four of the Hiiisborough Bridge Piers. The two boats were used in conjunction with up to four cTimbers to instaiT the monofiiament Tines in a manner simiiar to the guii exciosures deveToped by Hans Biockpoei of the Canadian WdeTife Service in Ontario. The exciosures consist of paraTTeT heavy monofiiament Tines stretched between upright poTes. These Tines discourage guTTs from landing because they tend to Tand in a sweeping gTide whereas terns settTe sTowTy from a hovering position.

This work is a continuation of over 20 years of monitoring the Common Terns nesting on the on bridge piers (refer to IsTand Naturaiist Issue 111 for the history of this coTony). This monitoring has shown that the Great Biack-backed GuTTs, a single pair of which started nesting on the site in 1985, are causing a serious decTine in the terns using this site and have reduced the production of tern young to very Tow numbers. This spring there were four pairs of Great Biack-backed Guiis occupying four piers and experience has shown that the guTTs wiTT eat either the eggs or the young of the terns nesting on the same pier as weTT as adjacent piers.

In 1988, the Society had two summer students monitor the guTT and tern interactions at the on bridge piers and, since then, the Society has gathered scientific information on these interactions from throughout eastern Canada and New Engiand. In AtTantic Canada, decTines and abandonments of tern coTonies have been frequent in the past few decades. An estimated 44,000 pairs of Common and Arctic terns stiTT nest in Atiantic Canada but this is a substantiaT reduction from tern numbers at the turn of the century when 100,000 to 500,000 pairs nested on Sabie Island aione. Tern numbers in the Great Lakes have decreased from 16,000 pairs to 3,000 pairs in the past 20 years. Monitoring in New EngTand has shown that once terns abandon a nesting site, it is difficuit to encourage their'return. Research over the past 30 pTus years indicates that action shouid be taken before terns abandon a nesting site.

Great BTack-backed Guiis and Herring Guiis popuTations have increased dramaticaiiy in response to garbage, human waste, and fish waste handiing practices. There are heaTthy breeding coionies of both species in HiiisborOugh Bay and the movement of the 4 pairs of birds away from the HiTstorough piers wiTT have a negligibie impact on their popuiation.

The Society wiTT'be monitoring the site throughout the breeding season to determine how the terns and guiis respond to the exciosures. The Society hopes that this non-destructive technique wiii be sufficient to protect the terns nesting at this site. The work was carried out in conjunction with the advice and permission of the Canadian NdeTife Service.

Thanks to Bruce Smith, AT McLennan, PhiT Hard, Geraid MacDougaTi, Ted

Currie, Robert Redmond, Todd Dupuis, and Bruce Pigot who voiunteered their

time and expertise to assist with the cTimbing and/0r pTanning for this

project. Thanks aTso to Hans Biockpoei and Tony Locke of the Canadian

WdeTife Service who provided vaTuabTe advice on the echosures.

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